Lithium metal negative electrode material, negative electrode sheet, lithium metal secondary battery, power using device, preparation method and application

Abstract

The present application relates to a lithium metal negative electrode material, a negative electrode sheet, a lithium metal secondary battery, an electric device, a preparation method and an application. The lithium metal negative electrode material comprises lithium metal and a polymer Poly bonded to the lithium metal in the lithium metal, the polymer Poly has a linear carbon chain and a first side chain and a second side chain grafted to the side groups of the linear carbon chain, the first side chain contains a fluorinated aliphatic chain Rf, and the second side chain contains an EO block. The lithium metal negative electrode material comprises a polymer layer firmly combined with the lithium metal in a dense and uniform manner, the polymer layer has certain elasticity, flexibility and swelling, can play a protective layer role at the negative electrode of the lithium metal secondary battery for a long time, the polymer composition in the polymer layer contains a fluorinated aliphatic chain and a flexible side chain, the polymer layer can effectively inhibit the contact reaction between the electrolyte and lithium, reduce the consumption of the electrolyte and lithium metal, prolong the cycle life of the battery, and also can inhibit the lithium dendrite problem.

Description

Technical Field

[0001] The present application relates to the technical field of lithium metal secondary batteries, and in particular to lithium metal negative electrode materials, negative electrode sheets, lithium metal secondary batteries, electrical devices, preparation methods and applications. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] With the development of various electronic products such as smart phones, tablets, smart wearables, power tools and electric vehicles, lithium metal secondary batteries with high energy density are becoming more and more popular, and high energy density is an irreversible trend in the future development of lithium metal secondary batteries.

[0004] However, lithium metal secondary batteries currently on the market often have problems with rapid cycle life decay and very serious lithium dendrite-induced short circuits and safety risks. Summary of the Invention

[0005] In view of the above problems, the present application provides a lithium metal negative electrode material, a negative electrode sheet, a lithium metal secondary battery, an electrical device, a preparation method, and applications. The lithium metal negative electrode material comprises a dense and uniform polymer layer that is firmly bonded to the lithium metal. The polymer layer has certain elasticity, flexibility, and swelling properties. The polymer component in the polymer layer contains a fluorinated aliphatic chain and a flexible side chain. The polymer layer can effectively inhibit the contact reaction between the electrolyte and lithium, reduce the consumption of the electrolyte and lithium metal, extend the battery cycle life, and also inhibit the problem of lithium dendrites.

[0006] In a first aspect, the present application provides a lithium metal negative electrode material, which includes a lithium-containing metal and a polymer Poly bonded to the lithium metal in the lithium-containing metal, wherein the polymer Poly has a linear carbon chain and a first side chain and a second side chain grafted to the side group of the linear carbon chain, wherein the first side chain contains a fluorinated aliphatic chain Rf, and the second side chain contains an EO block, and the structure of the EO block is *-(CH2CH2O) z -, z is a positive integer, and * indicates a connection site pointing to the linear carbon chain.

[0007] The lithium metal negative electrode material provided by the present application is coated with a dense and uniform polymer layer on the surface of the lithium-containing metal. The polymer layer can act as a protective layer at the negative electrode of the lithium metal secondary battery, effectively inhibit the contact reaction between the electrolyte and the lithium metal, reduce the consumption of the electrolyte and the lithium metal, and extend the battery cycle life; the linear carbon chain can give the polymer Poly and the polymer layer a certain flexibility; the polymer component Poly in the polymer layer has a stable chemical connection with the lithium-containing metal, so that the polymer layer is firmly bonded to the lithium-containing metal surface, and when the volume of the negative electrode side changes during the charge and discharge process, the polymer layer can be prevented from peeling off from the lithium-containing metal surface; the polymer Poly contains a fluorinated aliphatic chain Rf. On the one hand, the introduction of fluorine element can regulate the lithium ion The polymer layer is characterized by a fluorinated aliphatic chain (Rf) that imparts a certain degree of elasticity to the polymer layer, facilitating better adhesion between the polymer layer and the lithium-containing metal and the separator. The polymer (Poly) also contains a flexible EO block, which not only improves the flexibility of the polymer layer, enhances the close adhesion between the protective layer and the negative electrode substrate, and between the protective layer and the separator, reducing interfacial impedance, but also enhances the elasticity of the protective layer, allowing it to better adapt to the larger volume expansion of the negative electrode, thereby reducing or preventing polymer layer rupture and providing a longer-term protective effect. Furthermore, the dense and uniform polymer layer can be swollen by the electrolyte and provides good ionic conductivity after swelling, thereby enabling efficient transfer of lithium ions within the polymer layer and at the lithium metal interface. The introduction of the polymer layer results in minimal interfacial polarization, and the battery exhibits good charge and discharge cycle stability. The above-mentioned characteristics of the polymer layer work together to greatly improve the cycle life of the lithium metal secondary battery and suppress the lithium dendrite problem.

[0008] In some embodiments, in the structure of the polymer Poly, the number of the first side chains is m, and the number of the second side chains is n; wherein m and n are each independently an integer greater than or equal to 8;

[0009] Optionally, m and n are each independently an integer selected from 8 to 600.

[0010] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0011] The ratio of m to n satisfies 0.5≤m / n≤8, optionally, 1≤m / n≤5, further optionally, 1≤m / n≤3;

[0012] m is an integer selected from 50 to 250, optionally, m is an integer selected from 50 to 200;

[0013] n is an integer selected from 25 to 200, optionally, n is an integer selected from 40 to 150.

[0014] The introduction of a second side chain containing an EO block can improve the flexibility and swelling rate of the polymer layer, while the presence of a first side chain containing a fluorinated aliphatic chain Rf helps improve the elasticity of the polymer layer. Furthermore, by controlling the number of the two copolymer units in the polymer Poly, the flexibility and elasticity of the polymer layer can be simultaneously regulated, thereby regulating the elastic deformation of the polymer layer and the degree of adhesion between the polymer layer and the substrate and the separator. Greater elastic deformation helps better accommodate the significant volume expansion of the negative electrode during charging, reducing or preventing rupture of the protective layer and thus ensuring a longer-term protective effect. Greater flexibility facilitates close adhesion between the polymer layer and the lithium metal and the separator, reducing interfacial impedance and thus improving the battery's energy density and power density.

[0015] By controlling the m / n ratio, the elasticity, swelling rate, and ionic conductivity of the polymer can be optimized. By comprehensively regulating the polymer's elasticity, swelling rate, and ionic conductivity, the polymer protective layer on the negative electrode side can better and more durably isolate the electrolyte from contact and regulate lithium deposition.

[0016] In some embodiments, z is an integer selected from 2 to 10;

[0017] Optionally, z is an integer selected from 3 to 7.

[0018] By adjusting the size of z, that is, by adjusting the length of the EO block, the flexibility of the polymer layer can be adjusted.

[0019] In some embodiments, the polymer Poly comprises a repeating unit of the structure shown in formula (U1) and a repeating unit of the structure shown in formula (U2):

[0020]

[0021] in,

[0022] X1 and X2 are each independently H or an electron-withdrawing group;

[0023] Y1 and Y2 are each independently a cyano group or a linking group formed by a cyano group bonded to the lithium metal in the lithium-containing metal;

[0024] A1 and A2 are each independently O, S or NR 11 ; Among them, R 11 H or C 1-3 alkyl;

[0025] Rd is a hydrocarbon group or a hydrocarbon group substituted by Q1, wherein Q1 is selected from the following substituents: cyano, -C(=O)NH2, -OC(=O)NHR 6 and -S(=O)2F,R 6 H or C 1-6 alkyl;

[0026] Optionally, at least one of Y1 and Y2 is a linker formed by a cyano group bonded to the lithium metal in the lithium-containing metal.

[0027] In some embodiments, in the structure of the polymer Poly, X1 and X2 each appear and are independently H or cyano, nitro or -NR 21 R 22 ; Among them, R 21 and R 22 Each independently is H or C 1-3 alkyl;

[0028] Optionally, R 21 and R 22 are each independently H or methyl;

[0029] Further optionally, R 21 and R 22 All are methyl.

[0030] In some embodiments, in the structure of the polymer Poly, each occurrence of A1 and A2 is independently O, S or NH;

[0031] Optionally, each occurrence of A1 and A2 is independently O or NH.

[0032] In some embodiments, Rd is C 1-4 hydrocarbon group;

[0033] Optionally, Rd is C 1-4 alkyl;

[0034] Further optionally, Rd is C 1-3 alkyl;

[0035] Still further optionally, Rd is methyl.

[0036] The polymer Poly can be a copolymer comprising repeating units of the structure represented by formula (U1) and repeating units of the structure represented by formula (U2). The aforementioned polymer Poly can form chemical bonds with the lithium metal through a large number of cyano groups located on the side groups of the main chain, thereby achieving a stable chemical connection between the polymer layer and the lithium-containing metal, and further forming a covalent bond.

[0037] An electron-withdrawing group can be introduced into at least one of X1 and X2 in the polymer Poly, which is beneficial to increasing the reactivity of the carbon-carbon double bond in the cyano olefin carboxylic acid derivative monomer (such as a cyanoacrylic acid derivative monomer) during the formation of the polymer layer, promoting the in situ polymerization reaction, and facilitating a tighter and more uniform coating of the polymer layer on the lithium-containing metal surface.

[0038] In addition, the fluoroaliphatic chain Rf and the EO block can be independently grafted onto the linear carbon chain via ester bonds, amide bonds, or thioester bonds, thereby flexibly selecting the corresponding polymerization monomers.

[0039] Functional substituents can also be introduced at the end of the EO block to better optimize the performance of the polymer layer and lithium metal secondary battery as needed. For example, the introduction of a cyano group can further enhance the chemical bonding between the polymer Poly and lithium metal; the introduction of a fluorosulfonyl group (-S(=O)2F) can induce uniform deposition of lithium ions; the introduction of an amide group (-C(=O)NH2) can enhance the elastic modulus of the protective layer; the introduction of a carbamate group (-OC(=O)-NHR) can enhance the elastic modulus of the protective layer; and the introduction of a urea group (-O(=O)-NH2) can enhance the elastic modulus of the protective layer. 6 , where R 6 It can be H or alkyl), and the elasticity of the material can be improved by matching soft and hard segments.

[0040] In some embodiments, the structure of the polymer Poly comprises m repeating units represented by formula (U1) and n repeating units represented by formula (U2); the definitions of m and n are consistent with those described above;

[0041] Optionally, m repeating units represented by formula (U1) and n repeating units represented by formula (U2) are arranged linearly;

[0042] Further optionally, the polymer Poly has the general structure shown below:

[0043]

[0044] The first side chains can all be introduced by formula (U1), and the second side chains can all be introduced by formula (U2).

[0045] Furthermore, formula (U1) and formula (U2) can jointly participate in the formation of a linear carbon chain in the polymer Poly.

[0046] In formula (P1), m+n is numerically equal to the degree of polymerization of the polymer Poly. By controlling m+n, the molecular weight of the polymer Poly can be regulated.

[0047] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0048] The fluorine substitution rate in any Rf is independently ≥50%;

[0049] The number of fluorine atoms in any Rf is independently ≥ 4;

[0050] The mass percentage of fluorine element in the polymer Poly is 15% to 44%.

[0051] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0052] The fluorine substitution rate in any Rf is independently ≥55%;

[0053] The number of fluorine atoms in any Rf is independently ≥ 5, optionally, the number of fluorine atoms in any Rf is independently 5 to 15;

[0054] The mass proportion of fluorine element in the polymer Poly is 15% to 41%, optionally 20% to 41%.

[0055] By controlling the fluorine substitution rate in Rf, by controlling the number of fluorine atoms in Rf, and by controlling the mass proportion of fluorine element in polymer Poly in one or more ways, it is possible to better promote the uniform deposition of lithium ions, inhibit the formation of lithium dendrites, improve the lithium ion cycle life and reduce the short circuit risk, and alleviate the volume expansion of the lithium metal negative electrode side. In addition, it can also be beneficial to the application of the polymer layer in lithium metal secondary batteries that perform charge and discharge cycles at a high current density.

[0056] Taking controlling the mass proportion of fluorine in polymer Poly as an example, it is beneficial to improve the deposition morphology of lithium dendrites in lithium metal batteries and alleviate the volume expansion of lithium metal negative electrodes, which is beneficial to the application of polymer layers in lithium metal secondary batteries that perform charge and discharge cycles at high current density.

[0057] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0058] Each Rf independently contains 2 to 10 main chain carbon atoms;

[0059] The number of carbon atoms in any one Rf is independently an integer selected from 2 to 10.

[0060] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0061] Any Rf independently contains 2 to 8 main chain carbon atoms, optionally, any Rf independently contains 3 to 8 main chain carbon atoms;

[0062] The number of carbon atoms in any Rf is independently an integer selected from 2 to 8. Alternatively, the number of carbon atoms in any Rf is independently an integer selected from 3 to 8.

[0063] The length of the Rf side chain can be adjusted by controlling the number of carbon atoms in Rf, thereby giving the polymer layer appropriate elasticity and better inhibiting the polymer layer from rupturing under large volume deformation.

[0064] In some embodiments, in the structure of the polymer Poly, one, more or all Rf independently contain one or more heteroatoms selected from the group consisting of iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus;

[0065] Optionally, the number of heteroatoms in one, more or all of Rf is independently 1 or more;

[0066] Further optionally, the number of heteroatoms in one, multiple or all of Rf is selected from 1 or 2 to 6.

[0067] In some embodiments, in the structure of the polymer Poly, one, more or all Rf satisfy one or more of the following characteristics:

[0068] The number of oxygen atoms in one, more or all Rf is 1, 2, 3, 4 or 5;

[0069] The number of nitrogen atoms in one, more or all Rf is 1, 2 or 3;

[0070] The number of sulfur atoms in one, more or all Rf is 1, 2 or 3;

[0071] The number of phosphorus atoms in one, more or all Rf is 1 or 2;

[0072] The number of iodine atoms in one, more or all Rf is 1, 2, 3, 4, 5 or 6;

[0073] The number of silicon atoms in one, more or all of Rf is 1 or 2; and

[0074] The number of boron atoms in one, more than one or all of Rf is 1 or 2.

[0075] In some embodiments, in the structure of the polymer Poly, one, more or all of Rf contain one or more selected from iodine, -NR 12 -, -O-, -S-, -S(O)2-, >Si<, >B- and >P(=O)-, wherein R 12 H or C 1-3 alkyl;

[0076] Optionally, R12 is H or methyl;

[0077] Further optionally, R 12 For H.

[0078] In some embodiments, in the structure of the polymer Poly, one, more or all of Rf contain one or more atoms or atomic groups selected from the group consisting of -O-, -S(O)2- and -(O=)P(O-)2;

[0079] Optionally, one, more or all of Rf contain one or more -O-;

[0080] Optionally, one, more or all of Rf contain -S(O)2F;

[0081] Optionally, one, more or all of Rf contain -(O=)P(O-)2.

[0082] By introducing other heteroatoms besides fluorine atoms into Rf, such as one or more heteroatoms of iodine, nitrogen, oxygen, sulfur, silicon, boron, phosphorus, etc., special properties can be given to the polymer layer. For example, phosphorus has a certain flame retardant effect. For another example, iodine can also play a certain role in regulating lithium ion deposition. For another example, fluorosulfonyl group (-S(=O)2F) has a certain effect on improving the ionic conductivity of the polymer layer and promoting the uniform deposition of lithium ions.

[0083] In some embodiments, in the structure of the polymer Poly, any Rf is independently a linear structure or a branched structure.

[0084] The linear Rf is beneficial to improving the elasticity of the polymer material, while the side chain Rf is beneficial to improving the swelling capacity of the electrolyte membrane, thereby improving the ionic conductivity.

[0085] In some embodiments, in the structure of the polymer Poly, any Rf is independently a saturated structure or an unsaturated structure.

[0086] Fluorine-substituted aliphatic chains with saturated structures can impart greater mobility to the polymer chains, which is beneficial for improving the elasticity of the polymer layer. Furthermore, by introducing unsaturated bonds in Rf, the polymer layer can be cross-linked, enhancing the elastic modulus of the polymer protective layer.

[0087] In some embodiments, in the structure of the polymer Poly, the structure of any one Rf is independently represented by Formula (III-1), Formula (III-2) or Formula (III-3):

[0088]

[0089] in,

[0090] In formula (III-1), m3 is an integer selected from 2 to 10; R 31 、R 32 and R 3 Each occurrence is independently H or F; the structure represented by formula (III-1) contains at least 4 F atoms;

[0091] In formula (III-2), m 4a and m 4b are each independently an integer selected from 1 to 9; R 41a 、R 42a 、R 4a 、R 41b 、R 42b and R 4b Each occurrence is independently H or F; the structure represented by formula (III-2) contains at least 4 F atoms;

[0092] In formula (III-3), m5 is an integer selected from 2 to 10; R 51 and R 52 Each occurrence is independently H or F; the structure represented by formula (III-3) contains at least 4 F atoms.

[0093] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0094] m3 is an integer selected from 3 to 10; alternatively, m3 is an integer selected from 3 to 8;

[0095] m 4a and m 4b are each independently an integer selected from 2 to 9; optionally, m 4a and m 4b are each independently an integer selected from 2 to 8; further optionally, m 4a and m 4b are independently an integer selected from 3 to 8; further optionally, m 4a and m 4b Each independently represents an integer selected from 3 to 6

[0096] m5 is an integer selected from 3 to 10; alternatively, m5 is an integer selected from 3 to 8.

[0097] In some embodiments, in the structure of the polymer Poly, the structure of Rf is as shown in formula (III-1); or, the structure of Rf is as shown in formula (III-2); or, the structure of Rf is as shown in formula (III-3).

[0098] Among them, the structure of formula III-1 is a linear saturated fluorinated aliphatic chain. On the one hand, it can give the polymer layer better elasticity, reduce or avoid the rupture of the polymer layer under large volume deformation. On the other hand, it can effectively promote the uniform deposition of lithium ions through the fluorine element, inhibit the formation of lithium dendrites, and alleviate the volume expansion of the lithium metal negative electrode side.

[0099] The structure of formula III-2 can introduce phosphorus elements. In addition, the phosphate group therein has a flame retardant effect, which is beneficial to improving the safety performance of the battery cell.

[0100] The structure of formula III-3 can introduce a fluorosulfonyl group, which has a certain positive effect on improving the ionic conductivity of the polymer layer.

[0101] In some embodiments, in the structure of the polymer Poly, each time Formula (III-1) appears, the number of H atoms therein is 0, 1, 2, 3, or 4; each time Formula (III-2) appears, the number of H atoms therein is 0, 1, 2, 3, 4, 5, or 6; each time Formula (III-3) appears, the number of H atoms therein is 0, 1, 2, 3, or 4;

[0102] Optionally, the number of H atoms in formula (III-1) is 0;

[0103] Optionally, the number of H atoms in formula (III-2) is 0;

[0104] Optionally, the number of H atoms in formula (III-3) is 0.

[0105] By controlling the number of H atoms, the number of sites available for fluorine substitution can be controlled.

[0106] In some embodiments, in the structure of the polymer Poly, any Rf is independently any of the following structures:

[0107]

[0108] In some embodiments, the number average molecular weight of the polymer Poly is selected from 10 kDa to 200 kDa;

[0109] Optionally, the number average molecular weight of the polymer Poly is selected from 40 kDa to 100 kDa;

[0110] Further optionally, the number average molecular weight of the polymer Poly is selected from 50 kDa to 80 kDa.

[0111] By adjusting the degree of polymerization or molecular weight of the polymer Poly, the molecular chain length of the polymer Poly can be adjusted, which can not only achieve effective coating of lithium metal, but also maintain stable chemical connection, and also affect the density and uniformity of the polymer layer.

[0112] In some embodiments, the lithium-containing metal comprises lithium or a lithium alloy;

[0113] Optionally, the lithium alloy contains lithium and one or more elements selected from the group consisting of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel and titanium.

[0114] In some embodiments, the amount of lithium metal in the lithium-containing metal relative to the polymer Poly is greater than or equal to the catalyst amount, calculated on a molar ratio basis.

[0115] In the lithium metal anode material provided herein, the lithium metal only needs to provide a catalytic amount to successfully catalyze the in-situ polymerization reaction of a cyano-olefin carboxylic acid derivative monomer (e.g., a cyanoacrylic acid derivative monomer) on the lithium metal surface. The lithium metal only needs to be in contact with the polymer (Poly) at a catalytic amount to catalyze the in-situ polymerization reaction of a cyano-olefin carboxylic acid derivative monomer (e.g., a cyanoacrylic acid derivative monomer) on the lithium metal surface.

[0116] In a second aspect, the present application provides a negative electrode plate comprising a stacked lithium-containing layer and a polymer layer, wherein the negative electrode plate comprises the lithium metal negative electrode material described in the first aspect of the present application;

[0117] The lithium-containing layer includes the lithium-containing metal in the lithium metal negative electrode material, and the polymer layer includes the polymer Poly in the lithium metal negative electrode material.

[0118] The negative electrode plate includes a lithium metal negative electrode material distributed simultaneously in a lithium-containing layer and a polymer layer. On at least one side of the negative electrode plate, the lithium-containing layer is stably connected to a dense and uniform polymer layer by chemical bonding. The polymer layer has certain elasticity, flexibility and swelling properties, which can ensure a firm, tight and durable fit between the polymer layer and the lithium-containing layer, and between the polymer layer and the isolation membrane. It can better adapt to the large volume expansion of the negative electrode side during charging, and can serve as a protective layer at the negative electrode of the lithium metal secondary battery for a long time. The polymer layer can effectively inhibit the contact reaction between the electrolyte and lithium metal, reduce the consumption of the electrolyte and lithium metal, improve the coulombic efficiency, and extend the cycle life. It can also utilize the fluorinated aliphatic chain Rf in the lithium metal negative electrode material to promote the uniform deposition of lithium ions, inhibit the formation of lithium dendrites, and alleviate the volume expansion of the lithium metal negative electrode side. In addition, the elasticity, flexibility and swelling properties of the polymer layer not only promote close adhesion between the polymer layer and the lithium-containing layer, but also help to exert good ionic conductivity, reduce interfacial polarization, and reduce interfacial impedance, so that the lithium metal secondary battery can achieve higher energy density, power density, charge and discharge cycle stability and higher safety performance in the presence of the polymer layer.

[0119] In some embodiments, the lithium-containing layer consists essentially of the lithium-containing metal;

[0120] Optionally, the material of the lithium-containing layer is lithium;

[0121] Alternatively, the material of the lithium-containing layer is a lithium alloy.

[0122] In some embodiments, the polymer layer further contains a first electrolyte, and the first electrolyte contains a lithium salt and a first electrolyte solvent.

[0123] In some embodiments, the negative electrode plate satisfies one or more of the following characteristics:

[0124] The lithium salt includes one or more of lithium hexafluorophosphate, tetrafluoroboric acid, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium perchlorate and lithium bis(oxalate)borate;

[0125] The first electrolyte solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, butylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxolane, methyl nonafluoro-n-butyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, octafluoropentyl-tetrafluoroethyl ether, 1,2-bis(cyanoethoxy)ethane, diphenyl ether and 18-crown-6.

[0126] In some embodiments, the concentration of the lithium salt in the first electrolyte is selected from 0.2 mol / L to 8 mol / L;

[0127] Optionally, the concentration of the lithium salt in the first electrolyte is selected from 0.5 mol / L to 5 mol / L;

[0128] Further optionally, the concentration of the lithium salt in the first electrolyte is selected from 0.5 mol / L to 2 mol / L.

[0129] The polymer layer of the lithium metal negative electrode material contains an electrolyte (which can be recorded as the first electrolyte). The concentration of lithium salt in the first electrolyte can affect the deposition morphology of lithium ions. The concentration of lithium salt can change the Li +The solvation effect affects the composition of the solid electrolyte interface film (SEI film) and the deposition morphology of lithium ions. By controlling the lithium salt in the electrolyte at a more appropriate concentration, it is more conducive to promoting dense and uniform deposition of lithium ions and reducing the volume expansion of the negative electrode side. In addition, by controlling the lithium salt in the electrolyte at a more appropriate concentration, the polymer layer can also have more suitable mechanical properties, such as flexibility and elasticity, and can also achieve better lithium ion conductivity during charging and discharging. When the lithium salt concentration is too high, the mechanical properties of the polymer layer may deviate from the optimal range. When the lithium salt concentration is too low, the lithium ion conductivity during charging and discharging may deviate from the larger range.

[0130] In some embodiments, the mass proportion of the first electrolyte in the polymer layer is 20% to 80%;

[0131] Optionally, the mass proportion of the first electrolyte in the polymer layer is 30% to 60%;

[0132] Further optionally, the mass proportion of the first electrolyte in the polymer layer is 40% to 60%;

[0133] Further optionally, the mass proportion of the first electrolyte in the polymer layer is 40% to 55%.

[0134] In some embodiments, the mass ratio of the polymer Poly to the first electrolyte is 4:1 to 0.25:1;

[0135] Optionally, the mass ratio of the polymer Poly to the first electrolyte is 3:1 to 0.5:1;

[0136] Further optionally, the mass ratio of the polymer Poly to the first electrolyte is 2.5:1 to 1:1;

[0137] Further optionally, the mass ratio of the polymer Poly to the first electrolyte is 7:3 to 2:1.

[0138] By controlling the mass ratio of the first electrolyte in the polymer layer or controlling the mass ratio of the polymer Poly and the first electrolyte in the polymer layer within a more appropriate range, the electrolyte can be adjusted to have a more appropriate mass ratio in the polymer layer. The mass ratio of the electrolyte in the polymer layer can affect the elastic modulus and ionic conductivity of the protective layer. In the first electrolyte, the presence of a certain amount of lithium salt and solvent (referred to as the first electrolyte solvent) can plasticize the polymer layer and improve the elasticity of the polymer layer. In addition, in the process of forming a polymer layer by in situ polymerization, the lithium salt and solvent in the first electrolyte can be incorporated into the interior of the polymer layer, so that the polymer layer has a sponge-like loose porous structure on a microscopic scale, and the pores are filled with electrolyte, which can provide a path for the subsequent transmission of lithium ions.

[0139] In some embodiments, based on the first electrolyte, the swelling rate of the polymer layer at 25° C. is 8% to 65%;

[0140] Further optionally, the swelling rate of the polymer layer at 25° C. is 15% to 55%;

[0141] Further optionally, the swelling rate of the polymer layer at 25° C. is 18% to 44%;

[0142] Further optionally, the swelling ratio of the polymer layer at 25° C. is 30% to 40%.

[0143] In some embodiments, based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.001 mS / cm to 5 mS / cm;

[0144] Optionally, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.1 mS / cm to 5 mS / cm;

[0145] Alternatively, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.5 mS / cm to 5 mS / cm;

[0146] Alternatively, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.9 mS / cm to 4.8 mS / cm;

[0147] Alternatively, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.95 mS / cm to 2.6 mS / cm.

[0148] In some embodiments, the thickness of the polymer layer is 5 nm to 10 μm;

[0149] Optionally, the thickness of the polymer layer is 0.02 μm to 8 μm;

[0150] Further optionally, the thickness of the polymer layer is 0.05 μm to 8 μm;

[0151] Further optionally, the thickness of the polymer layer is 0.05 μm to 5 μm;

[0152] Further optionally, the thickness of the polymer layer is 0.1 μm to 5 μm.

[0153] The thickness of the polymer layer on the surface of the lithium-containing metal can be controlled at a thin nanoscale, which is more conducive to the assembled battery cell showing smaller interface impedance.

[0154] In some embodiments, the elastic modulus of the polymer layer at 25° C. is 0.1 MPa to 65 MPa;

[0155] Optionally, the elastic modulus of the polymer layer at 25° C. is 0.5 MPa to 50 MPa;

[0156] Further optionally, the elastic modulus of the polymer layer at 25° C. is 10 MPa to 46 MPa;

[0157] Further optionally, the elastic modulus of the polymer layer at 25° C. is 18 MPa to 41 MPa;

[0158] Further optionally, the elastic modulus of the polymer layer at 25° C. is 29 MPa to 41 MPa.

[0159] In some embodiments, the polymer layer has an elastic deformation range of 55% to 350% at 25°C;

[0160] Optionally, the elastic deformation range of the polymer layer at 25° C. is 150% to 350%;

[0161] Further optionally, the elastic deformation range of the polymer layer at 25° C. is 150% to 300%;

[0162] Further optionally, the elastic deformation range of the polymer layer at 25° C. is 168% to 280%.

[0163] By controlling parameters such as the elastic modulus and elastic deformation range of the polymer layer within a more appropriate range, it is beneficial to make the polymer layer have more appropriate elasticity, better promote close contact between the polymer layer and the lithium-containing metal layer, reduce the interface impedance, and help achieve better energy density and power density.

[0164] In a third aspect, the present application provides a lithium metal secondary battery, which includes a positive electrode plate, an isolation membrane and the negative electrode plate described in the second aspect of the present application, the isolation membrane is arranged between the positive electrode plate and the negative electrode plate, and the polymer layer is arranged on the side of the negative electrode plate close to the isolation membrane.

[0165] The negative electrode plate in the lithium metal secondary battery includes a lithium metal negative electrode material distributed simultaneously in a lithium-containing layer and a polymer layer. On at least one side of the negative electrode plate, the lithium-containing layer is stably connected to a dense and uniform polymer layer by chemical bonding. The polymer layer has certain elasticity, flexibility and swelling properties, which can ensure a firm, tight and durable fit between the polymer layer and the lithium-containing layer, and between the polymer layer and the isolation membrane. It can better adapt to the large volume expansion of the negative electrode side during charging, and can serve as a protective layer at the negative electrode of the lithium metal secondary battery for a long time. The polymer layer can effectively inhibit the contact reaction between the electrolyte and lithium metal, reduce the consumption of the electrolyte and lithium metal, improve the coulombic efficiency, and extend the cycle life. It can also utilize the fluorinated aliphatic chain Rf in the lithium metal negative electrode material to promote the uniform deposition of lithium ions, inhibit the formation of lithium dendrites, and alleviate the volume expansion of the lithium metal negative electrode side. In addition, the elasticity, flexibility and swelling properties of the polymer layer not only promote close adhesion between the polymer layer and the lithium-containing layer, but also help to exert good ionic conductivity, reduce interfacial polarization, and reduce interfacial impedance, so that the lithium metal secondary battery can achieve higher energy density, power density, charge and discharge cycle stability and higher safety performance in the presence of the polymer layer.

[0166] In addition, by inhibiting the contact reaction between the electrolyte and lithium metal and reducing the consumption of the electrolyte and lithium metal, the coulombic efficiency of the battery can also be improved.

[0167] In some embodiments, the lithium metal secondary battery further includes a second electrolyte, and the components of the second electrolyte and the first electrolyte in the polymer layer may be the same or different.

[0168] In a fourth aspect, the present application provides an electrical device comprising the lithium metal secondary battery described in the third aspect of the present application.

[0169] In a fifth aspect, the present application provides an application of a monomer composition in preparing a negative electrode sheet or a lithium metal secondary battery, wherein the monomer composition comprises a first monomer represented by formula (M1) and a second monomer represented by formula (M2):

[0170]

[0171] wherein X1, X2, Y1, Y2, A1, A2, Rf and Rd are as defined in the first aspect of the present application; z is as defined in the first aspect of the present application; at least one of Y1 and Y2 is a cyano group;

[0172] The negative electrode plate contains lithium metal;

[0173] The first monomer and the second monomer are used to form a polymer layer bonded to the lithium metal in the negative electrode plate.

[0174] The first monomer and the second monomer in the monomer composition are both cyanoacrylic acid derivatives, the cyano group therein can contact with the lithium in the outermost layer of the negative electrode substrate to form a chemical connection, and the carbon-carbon double bond therein can undergo an in-situ polymerization reaction under lithium catalysis, thereby preparing the lithium metal negative electrode material of the first aspect of the present application. At this time, a firmly connected, dense and uniform polymer layer can be formed on the surface of the lithium-containing layer of the negative electrode. The polymer layer has certain elasticity, flexibility and swelling properties, and can play the role of a protective layer for a long time.

[0175] In some embodiments, the application includes the following steps: the first monomer and the second monomer are brought into contact with lithium metal in the lithium-containing layer to form the polymer layer through an in-situ polymerization reaction.

[0176] In some embodiments, the negative electrode plate is as defined in the second aspect of the present application, and the lithium metal secondary battery is as defined in the third aspect of the present application.

[0177] In a sixth aspect, the present application provides a method for preparing a negative electrode sheet, which comprises the following steps:

[0178] Providing a negative electrode substrate, wherein the outermost layer of at least one side of the negative electrode substrate is a lithium-containing layer, and the lithium-containing layer contains lithium metal; and also providing a reaction mixture containing a monomer composition and a first electrolyte;

[0179] The reaction mixture is applied to the surface of the lithium-containing layer on at least one side of the negative electrode substrate, so that the monomer composition contacts at least a catalytic amount of lithium metal, and the monomer composition undergoes an in-situ polymerization reaction to form a polymer Poly bonded to the lithium metal in the lithium-containing layer;

[0180] Wherein, the monomer composition is as defined in the fifth aspect of this application;

[0181] The first electrolyte is as defined in the second aspect of the present application.

[0182] In the presence of the first electrolyte, the cyano group in the monomer composition can form a chemical connection (further, a covalent connection) with lithium in the outermost layer of the negative electrode tab substrate, and the carbon-carbon double bond therein can be in-situ polymerized under lithium catalysis to form the aforementioned polymer Poly, thereby preparing the lithium metal negative electrode material of the first aspect of the present application. At this time, a firmly connected, dense and uniform polymer layer can be formed on the surface of the lithium-containing layer of the negative electrode, which has certain elasticity, flexibility and swelling properties, and can play a protective layer role for a long time. Compared with the polymer coating in the physical coating method in the prior art, the polymer layer formed in the present application is not only stably combined on the surface of the lithium-containing layer through chemical connection, but also can reduce, avoid or effectively delay the peeling of the polymer layer from the surface of the lithium-containing layer during the charging and discharging process. In addition, the polymer layer of the present application is dense and uniform, and the thickness of the polymer layer can be controlled in the nanometer scale by in-situ polymerization, so that the assembled battery cell can exhibit smaller interface impedance.

[0183] In some embodiments, the reaction temperature of the in-situ polymerization is selected from 30-100°C.

[0184] Optionally, the reaction temperature of the in-situ polymerization is selected from 30-60°C.

[0185] Alternatively, the reaction temperature of the in-situ polymerization is selected from 40-80°C.

[0186] In some embodiments, the reaction time of the in-situ polymerization is selected from 0.1-24h.

[0187] Optionally, the reaction time of the in-situ polymerization is selected from 0.1-12h.

[0188] Further optionally, the reaction time of the in-situ polymerization is selected from 0.1-6h.

[0189] In some embodiments, the surface of the negative electrode tab substrate is formed with the polymer layer of the second aspect of the present application.

[0190] In some embodiments, the negative electrode tab substrate is a pure lithium sheet or a lithium alloy.

[0191] Optionally, the mass fraction of lithium in the lithium alloy is ≥50%.

[0192] When the negative electrode tab substrate is a pure lithium sheet or a lithium alloy, the battery negative electrode tab can further introduce a negative current collector to facilitate the assembly of the tab, or a pure lithium sheet covered with a polymer layer can be used as a negative electrode tab.

[0193] In some embodiments, the negative electrode tab is as defined in the second aspect of the present application.

[0194] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF DRAWINGS

[0195] To better describe and illustrate the embodiments or examples of the applications disclosed herein, reference can be made to one or more drawings. Additional details or examples used to describe the drawings should not be considered limiting to the scope of the disclosed applications, the presently described embodiments or examples, and the best mode of these applications as presently understood. Moreover, like reference numerals are used to designate like parts throughout the accompanying drawings. In the drawings:

[0196] Figure 1 is a structural schematic diagram of a negative electrode tab of an embodiment of the application, a polymer layer is arranged on a single side of the negative electrode tab;

[0197] Figure 2 is a structural schematic diagram of a negative electrode tab of an embodiment of the application, a polymer layer is arranged on a single side of the negative electrode tab and a negative current collector is arranged;

[0198] Figure 3 is a structural schematic diagram of a negative electrode tab of an embodiment of the application, a second negative active material layer is further arranged between the lithium-containing layer and the negative current collector;

[0199] Figure 4 is a structural schematic diagram of a negative electrode tab of an embodiment of the application, a polymer layer is arranged on both sides of the negative electrode tab;

[0200] Figure 5 is a structural schematic diagram of a negative electrode tab of an embodiment of the application, a polymer layer is arranged on both sides of the negative electrode tab, and a second negative active material layer is arranged between the lithium-containing layer and the negative current collector on both sides;

[0201] Figure 6 is a schematic diagram of a secondary battery of an embodiment of the application;

[0202] Figure 7 is a schematic diagram of a secondary battery of an embodiment of the application; Figure 6 is an exploded view of a secondary battery of an embodiment of the application as shown in FIG. 5;

[0203] Figure 8 is a schematic diagram of a use electric device using a secondary battery of an embodiment of the application as a power supply.

[0204] BRIEF DESCRIPTION OF DRAWINGS: 100, negative electrode tab substrate; 110, negative current collector; 120, second negative active material layer; 130, lithium-containing layer; 200, polymer layer; 5, secondary battery; 51, shell; 52, electrode assembly; 53, cover plate; 6, use electric device. DETAILED DESCRIPTION

[0205] Below, some embodiments of the lithium metal negative electrode material, negative electrode sheet, lithium metal secondary battery, electrical device, preparation method and application of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0206] Numerical value " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and selected lower limit and upper limit define the boundary of special range. The scope that this mode limits can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, and promptly any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if also listing the maximum range value 3,4 and 5, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for a combination of these values. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0207] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0208] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, and may preferably be performed sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0209] Unless otherwise specified, the terms "having," "including," "containing," and "comprising" used in this application may each independently represent open or closed forms. For example, "including" and "comprising" may also represent other components or temporal features not listed, or may only represent the listed components or temporal features. Examples of components include materials or components, structures, elements, and instruments; non-limiting examples of temporal features include actions, conditions for the occurrence of actions, timing, and states.

[0210] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." Furthermore, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0211] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0212] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more relevant listed items, and also include any and all combinations of the relevant listed items, wherein the arbitrary and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items. For example, "A and / or B" means a group consisting of A, B, and "a combination of A and B." Among them, "including A and / or B" can mean "including A, including B, and including A and B", and can also mean "including A, including B, or including A and B", which can be appropriately understood according to the sentence in which it is located.

[0213] In this application, references to "plurality," "multiple," and the like, unless otherwise specified, refer to a quantity greater than or equal to two. For example, "one or more" refers to one or greater than or equal to two. It is understood that references to "any number" of items refer to any suitable combination of multiple items, i.e., any combination of "any number" of items that is consistent with the present application and that allows for the implementation of the present application.

[0214] As used herein, "combination thereof", "any combination thereof", "any combination thereof" and the like include all suitable combinations of any two or more of the listed items.

[0215] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the technical solution that can implement the present application.

[0216] Herein, the terms "preferred," "better," and "more preferred" are used solely to describe preferred implementations or examples and should not be construed as limiting the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, each "preferred" term is considered independent unless otherwise specified and there are no contradictions or mutual constraints.

[0217] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0218] In this application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate the differences in content between different technical solutions, but should not be understood as limiting the scope of protection of this application.

[0219] In this application, the terms "first," "second," "third," "fourth," etc. in "the first aspect," "the second aspect," "the third aspect," "the fourth aspect," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, "first," "second," "third," "fourth," etc. serve only as non-exhaustive enumeration and description and should be understood not to constitute a closed-ended limitation on quantity.

[0220] In this application, when referring to a data range, if the unit is only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5h or 3-5h both mean that the units of the left endpoint "3" and the right endpoint "5" are both hours.

[0221] The weight of the related components mentioned in the embodiments of the present application can not only refer to the content of each component, but also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the related components in the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiments of the present application. Further, the weight mentioned in the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0222] In the present application, the term "hydrocarbon group" refers to a monovalent group composed of two elements of carbon and hydrogen. The hydrocarbon group can be in the form of an alkyl group, an alkenyl group, an alkynyl group, etc.

[0223] In the present application, the term "alkyl group" refers to a saturated hydrocarbon monovalent residue generated by losing one hydrogen atom from a primary carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. The phrases containing this term, for example, "C1~ 10 "alkyl group" refers to an alkyl group containing 1 to 10 carbon atoms, which can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl or C 10Alkyl. Examples of suitable alkyl groups include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH (CH3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl ( -CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH (CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0224] In this application, the term "alkenyl" refers to a group containing at least one unsaturated site (ie, carbon-carbon sp 2 A monovalent residue formed by losing a hydrogen atom from a hydrocarbon (with a double bond) containing this term. Phrases containing this term, for example, "C2~C 10 Alkenyl" or "C 2-10 "Alkenyl" refers to an alkenyl group containing 2 to 10 carbon atoms, each occurrence of which can be independently C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl, C6 alkenyl, C7 alkenyl, C8 alkenyl, C9 alkenyl or C 10Suitable examples include, but are not limited to, vinyl (—CH═CH 2 ), allyl (—CH 2 CH═CH 2 ), cyclopentenyl (—C 5 H 7 ), and 5-hexenyl (—CH 2 CH 2 CH 2 CH 2 CH═CH 2 ).

[0225] In this application, the term "alkynyl" refers to a monovalent residue containing a hydrocarbon having at least one unsaturated site, i.e., a carbon-carbon sp triple bond, which loses a hydrogen atom. Phrases containing this term, for example, "C2-C 10 "Alkynyl" refers to an alkynyl group containing 2 to 10 carbon atoms, each occurrence of which can be independently C2 alkynyl, C3 alkynyl, C4 alkynyl, C5 alkynyl, C6 alkynyl, C7 alkynyl, C8 alkynyl, C9 alkynyl or C 10 Suitable examples include, but are not limited to, ethynyl (-C≡CH) and propargyl (-CH2C≡CH).

[0226] In the present application, fluorosulfonyl corresponds to -S(=O)2F, and nitro corresponds to -NO2.

[0227] High energy density is an irreversible trend in the development of lithium metal batteries in the future. It has high specific capacity (3860mAh / g), extremely low potential (-3.04V vs.H2 / H + ) has therefore received widespread attention in the industry, but the high reactivity of lithium metal and the problem of dendrite short-circuiting have greatly restricted its further development. Lithium metal has high reactivity and is prone to side reactions with the electrolyte, consuming the electrolyte and lithium metal, producing a thicker passivation layer, and causing the battery cycle life to decay rapidly. In addition, during the charging process, lithium ions are unevenly deposited due to regional differences in ion flow and electron flow, resulting in dendrites. On the one hand, lithium dendrites have a high specific surface area, which will aggravate the consumption of electrolyte and even cause battery diving; on the other hand, the rapid growth of lithium dendrites will penetrate the diaphragm, bringing the risk of battery short circuit.

[0228] Current reports have reported attaching a protective layer to the lithium metal surface through physical coating. The protective layer is bonded to the lithium metal via intermolecular van der Waals forces, which are weak. During long cycles, the protective layer can easily lose contact with the lithium metal due to volume changes on the negative electrode side. The functional groups contained in the protective layer have no regulatory effect on lithium deposition. Furthermore, if the protective layer is independently obtained and then attached between the lithium metal and the separator, the process is complex and the thin layer has poor flatness. To improve the wettability of the lithium metal surface, a highly viscous polymer solution is applied to the lithium metal surface, but the resulting protective layer is relatively thick.

[0229] In response to the above-mentioned common technical problems, in the first aspect, the present application provides a lithium metal negative electrode material.

[0230] The lithium metal negative electrode material provided in the first aspect of the present application includes a polymer layer that is both flexible and highly elastic. The polymer layer has lithium ion transport and regulation functions and is tightly bonded to the lithium metal through chemical connection. It can serve as a protective layer for the lithium metal and is expected to alleviate or solve the above-mentioned technical problems. First, the presence of the polymer layer can reduce the direct contact between the electrolyte and the lithium metal, inhibit the occurrence of side reactions, and reduce the consumption of the electrolyte and lithium metal. Secondly, a higher ionic conductivity and functional group design can be introduced into the polymer layer, which can not only promote the effective transfer of lithium ions within the polymer layer and at the interface with the lithium metal, but also promote the uniform deposition of lithium ions, inhibit the formation of lithium dendrites, reduce the consumption of electrolyte, and greatly inhibit the problem of dendrites piercing the diaphragm and short-circuiting. Furthermore, the close bonding between the polymer layer and the lithium metal can better adapt to the volume change of the negative electrode side during charging and discharging, and can avoid peeling from the lithium metal surface as much as possible. In addition, the elastic polymer layer is conducive to compatibility with the volume expansion of the lithium metal side during charging, is not easy to break, and can play a protective role for a long time.

[0231] In some embodiments, the present application provides a lithium metal negative electrode material, which includes a lithium-containing metal and a polymer Poly bonded to the lithium metal in the lithium-containing metal, the polymer Poly having a linear carbon chain and a first side chain and a second side chain grafted to the side group of the linear carbon chain, the first side chain containing a fluorinated aliphatic chain Rf, the second side chain containing an EO block, and the structure of the EO block is *-(CH2CH2O) z -, z is a positive integer, and * indicates a connection site pointing to the linear carbon chain.

[0232] In this application, unless otherwise specified, the term "lithium-containing metal" may be substantially composed of lithium (Li) metal, may be a lithium alloy, or may be a composition comprising lithium metal and a lithium alloy. The lithium-containing metal "substantially composed of lithium metal" means that the weight proportion of metallic lithium is very high, and the proportion described by "substantially" here is, for example, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, equal to 100%, etc.

[0233] In this application, unless otherwise specified, the term "lithium metal" or "metallic lithium" refers to metallic lithium.

[0234] In this application, the term "lithium" used independently, unless otherwise specified, refers to metallic lithium, for example, "lithium" in lithium-containing metals.

[0235] In this application, unless otherwise specified, the term "lithium alloy" refers to an alloy containing lithium. In addition to lithium, a lithium alloy may also contain one or more other types of metals. All lithium alloys reported to be used as negative electrode active materials in lithium metal batteries fall within the scope of this application. For example, a lithium alloy can be an alloy of lithium and one or more metals selected from silver, magnesium, aluminum, gold, zinc, tin, copper, nickel and titanium. Non-limiting examples of lithium alloys include lithium-magnesium alloys and lithium-aluminum alloys.

[0236] In this application, unless otherwise specified, "polymer" refers to at least one type of polymer having an average molecular weight greater than 1000 Da, for example, at least one of the number average molecular weight and the weight average molecular weight greater than 1000 Da.

[0237] In this application, unless otherwise specified, "linear carbon chain" refers to a linear chain carbon skeleton composed of carbon atoms connected in sequence, such as the following structure "...CCCCC...". The positions where non-hydrogen atoms or groups are connected to carbon atoms other than the end points of the linear carbon chain can be referred to as "side chains". The side chains involved in this application include first side chains and second side chains. The "first" and "second" here are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the indicated technical features.

[0238] In this application, unless otherwise specified, the structural description "grafted" involved in the structure of an organic compound, such as a polymer Poly, indicates a chemical connection method, and further, unless otherwise specified, indicates a covalent connection method.

[0239] In this application, unless otherwise specified, the term "aliphatic chain" may also be referred to as "aliphatic group," which refers to a group containing at least one carbon atom and no aromatic group. When the aliphatic chain contains only one carbon atom, the carbon atom is connected to four adjacent atoms by four single bonds, i.e., excluding methylene groups substituted with carbonyl atoms or groups. An aliphatic chain is permitted to contain one or more heteroatoms. When there are multiple heteroatoms, the heteroatoms may be of one or more types. A heteroatom refers to an atom that is not carbon or hydrogen. Examples of heteroatoms include, but are not limited to, fluorine, iodine, nitrogen, oxygen, sulfur, silicon, boron, and phosphorus. An aliphatic chain may be an aliphatic hydrocarbon group, an aliphatic hydrocarbon group in which one or more hydrogen atoms are independently replaced by non-fluorine heteroatoms, or an aliphatic hydrocarbon group in which one or more carbon atoms are independently replaced by heteroatoms. Both hydrogen atom substitution and carbon atom substitution are permitted.

[0240] In this application, unless otherwise specified, "EO block" refers to a segment having one or more EO units; wherein the EO unit is a unit with the structure -CH2CH2O-.

[0241] In this application, the “*” mark in different structures or positions may have different meanings.

[0242] The lithium metal negative electrode material provided by the present application is coated with a dense and uniform polymer layer on the surface of the lithium-containing metal. The polymer layer can act as a protective layer at the negative electrode of the lithium metal secondary battery, effectively inhibit the contact reaction between the electrolyte and the lithium metal, reduce the consumption of the electrolyte and the lithium metal, and extend the battery cycle life; the linear carbon chain can give the polymer Poly and the polymer layer a certain flexibility; the polymer component Poly in the polymer layer has a stable chemical connection with the lithium-containing metal, so that the polymer layer is firmly bonded to the lithium-containing metal surface, and when the volume of the negative electrode side changes during the charge and discharge process, the polymer layer can be prevented from peeling off from the lithium-containing metal surface; the polymer Poly contains a fluorinated aliphatic chain Rf. On the one hand, the introduction of fluorine element can regulate the lithium ion The polymer layer is characterized by a fluorinated aliphatic chain (Rf) that imparts a certain degree of elasticity to the polymer layer, facilitating better adhesion between the polymer layer and the lithium-containing metal and the separator. The polymer (Poly) also contains a flexible EO block, which not only improves the flexibility of the polymer layer, enhances the close adhesion between the protective layer and the negative electrode substrate, and between the protective layer and the separator, reducing interfacial impedance, but also enhances the elasticity of the protective layer, allowing it to better adapt to the larger volume expansion of the negative electrode, thereby reducing or preventing polymer layer rupture and providing a longer-term protective effect. Furthermore, the dense and uniform polymer layer can be swollen by the electrolyte and provides good ionic conductivity after swelling, thereby enabling efficient transfer of lithium ions within the polymer layer and at the lithium metal interface. The introduction of the polymer layer results in minimal interfacial polarization, and the battery exhibits good charge and discharge cycle stability. The above-mentioned characteristics of the polymer layer work together to greatly improve the cycle life of the lithium metal secondary battery and suppress the lithium dendrite problem.

[0243] In some embodiments, in the structure of the polymer Poly, the number of the first side chains is m, and the number of the second side chains is n; wherein m and n are each independently an integer greater than or equal to 8.

[0244] In some embodiments, m and n are each independently an integer selected from 8 to 600, for example, can be any of the following values or a range selected from any two of the following values: 8, 9, 10, 11, 12, 15, 16, 18, 20, 22, 24, 25, 30, 40, 50, 60, 70, 80, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, etc., and m and n can each independently be selected from any suitable range of the following: 8 to 300, 8 to 250, 8 to 200, 8 to 180, 10 to 300, 10 to 250, 10 to 200, 10 to 180, 20 to 300, 20 to 250, 20 to 200, 20 to 180, 25 to 300, 25 to 250, 25 to 200, 25 to 180, 30 to 300, 30 to 250, 30 to 200, 30 to 180, 50 to 300, 50 to 250, 50 to 200, 50 to 180, 60 to 300, 60 to 250, 60 to 200, 60 to 180, 80 to 300, 80 to 250, 80 to 200, 80 to 180, 8 to 150, 10 to 150, 20 to 150, 25 to 150, 30 to 150, 35 to 150, 36 to 150, 8 to 125, 10 to 125, 20 to 125, 25 to 125, 30 to 125, 35 to 125, 36 to 125, etc.

[0245] In some embodiments, m is an integer selected from 8 to 300, and can be selected from any suitable range of the following: 8 to 300, 8 to 250, 8 to 200, 8 to 180, 10 to 300, 10 to 250, 10 to 200, 10 to 180, 20 to 300, 20 to 250, 20 to 200, 20 to 180, 25 to 300, 25 to 250, 25 to 200, 25 to 180, 30 to 300, 30 to 250, 30 to 200, 30 to 180, 50 to 300, 50 to 250, 50 to 200, 50 to 180, 60 to 300, 60 to 250, 60 to 200, 60 to 180, 80 to 300, 80 to 250, 80 to 200, 80 to 180, etc.

[0246] In some embodiments, m is an integer selected from 50 to 250, and can be selected from 50 to 200.

[0247] In some embodiments, n is an integer selected from 8 to 300, and can also be selected from any suitable range: 8 to 300, 8 to 250, 8 to 200, 8 to 180, 10 to 300, 10 to 250, 10 to 200, 10 to 180, 20 to 300, 20 to 250, 20 to 200, 20 to 180, 25 to 300, 25 to 250, 25 to 200, 25 to 180, 30 to 300, 30 to 250, 30 to 200, 30 to 180, 50 to 300. 00, 50-250, 50-200, 50-180, 60-300, 60-250, 60-200, 60-180, 80-300, 80-250, 80-200, 80-180, 8-150, 10-150, 20-150, 25-150, 30-150, 35-150, 36-150, 8-125, 10-125, 20-125, 25-125, 30-125, 35-125, 36-125, etc.

[0248] In some embodiments, n is an integer selected from 25 to 200. Alternatively, n is an integer selected from 40 to 150.

[0249] The value ranges of m and n can be combined in any suitable manner. In some embodiments, m is an integer selected from 50 to 250, and n is an integer selected from 25 to 200. In other embodiments, m is an integer selected from 50 to 200, and n is an integer selected from 40 to 150.

[0250] In some embodiments, the ratio of m to n (denoted as m / n) satisfies 0.5 ≤ m / n ≤ 8, optionally 1 ≤ m / n ≤ 5, and further optionally 1 ≤ m / n ≤ 3. m / n can be any of the following values ​​or an interval consisting of any two of the following values: 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, etc. m / n can also be selected from any suitable range of 1 to 8, 2 to 8, 2 to 5, etc.

[0251] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0252] The ratio of m to n satisfies 0.5≤m / n≤8, optionally, 1≤m / n≤5, further optionally, 1≤m / n≤3;

[0253] m is an integer selected from 50 to 250, optionally, m is an integer selected from 50 to 200;

[0254] n is an integer selected from 25 to 200, optionally, n is an integer selected from 40 to 150.

[0255] The introduction of a second side chain containing an EO block can improve the flexibility and swelling rate of the polymer layer, while the presence of a first side chain containing a fluorinated aliphatic chain Rf helps improve the elasticity of the polymer layer. Furthermore, by controlling the number of the two copolymer units in the polymer Poly, the flexibility and elasticity of the polymer layer can be simultaneously regulated, thereby regulating the elastic deformation of the polymer layer and the degree of adhesion between the polymer layer and the substrate and the separator. Greater elastic deformation helps better accommodate the significant volume expansion of the negative electrode during charging, reducing or preventing rupture of the protective layer and thus ensuring a longer-term protective effect. Greater flexibility facilitates close adhesion between the polymer layer and the lithium metal and the separator, reducing interfacial impedance and thus improving the battery's energy density and power density.

[0256] By controlling the m / n ratio, the elasticity, swelling rate, and ionic conductivity of the polymer can be optimized. By comprehensively regulating the polymer's elasticity, swelling rate, and ionic conductivity, the polymer protective layer on the negative electrode side can better and more durably isolate the electrolyte from contact and regulate lithium deposition.

[0257] In some embodiments, in the EO block structure, z is a positive integer. Furthermore, z is a positive integer ≤ 10. z can also be an integer selected from 2 to 10; further optionally, z is an integer selected from 3 to 7. z can also be 2, 3, 4, 5, 6, 7, 8, 9, or 10, or z can be selected from a range consisting of any two of the aforementioned integers, such as 2 to 8, 3 to 7, and the like.

[0258] In some embodiments, in the polymer Poly, each occurrence of z is independently 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0259] In some embodiments, in the polymer Poly, each occurrence of z is independently 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0260] In some embodiments, in the polymer Poly, each occurrence of z is independently 2, 3, 4, 5, 6, 7, or 8.

[0261] In some embodiments, in the polymer Poly, each occurrence of z is independently 3, 4, 5, 6, or 7.

[0262] z in the EO block structure reflects the number of EO units (oxirane units) with structure "CH2CH2O" in the EO block. By adjusting the size of z, i.e. by adjusting the length of the EO block, the flexibility of the polymer layer can be adjusted, and thus the elastic deformation of the polymer layer and the adhesion of the polymer layer to the substrate and the separator can be controlled. By controlling z in a more suitable range or size, the aforementioned multi-dimensional comprehensive excellent effects can also be achieved in cooperation with other structural units (such as Rf chains) of the polymer Poly. When the polymer Poly is prepared by in-situ polymerization, by controlling z in a more suitable range or size, the flexibility of the polymer layer can be more effectively adjusted, while maintaining a high reaction rate and effective grafting density, and thus maintaining the high compactness of the polymer layer.

[0263] In the present application, "maintain" means at least still having beneficial effects relative to the reference scheme, and it is understood that it does not require strict numerical equality.

[0264] In some embodiments, the polymer Poly comprises repeating units of structure (U1) and repeating units of structure (U2):

[0265]

[0266] wherein,

[0267] X1and X2are each independently H or an electron-withdrawing group;

[0268] Y1and Y2are each independently cyano or a linking group formed by bonding cyano to lithium metal in the lithium-containing metal;

[0269] A1and A2are each independently O, S or NR 11 ; wherein R 11 is H or C 1-3 alkyl;

[0270] Rdis a hydrocarbon group or a Q1-substituted hydrocarbon group, Q1is selected from the following substituents: cyano, -C(=O)NH2, -OC(=O)NHR 6 and -S(=O)2F, R 6 is H or alkyl; optionally, R 6 is H or C 1-6 alkyl; further optionally, R 6 is H or C 1-3 alkyl.

[0271] In some embodiments, at least one of Y1 and Y2 is a linker formed by a cyano group bonded to the lithium metal in the lithium-containing metal. In this application, the asterisk "*" in the repeating unit of the structure represented by formula (U1) and the repeating unit of the structure represented by formula (U2) is a conventional notation in the art, and the position marked by "*" indicates the connection site with the adjacent, identical or different repeating unit.

[0272] In the present application, the “bonding” mode or “chemical connection” between the cyano group and the lithium group refers to a covalent connection unless otherwise specified.

[0273] In the main chain of the polymer Poly, at least one of the main chain carbon atoms connected to the Rf side group and the main chain carbon atom connected to the EO block can be simultaneously connected to a cyano group. In this case, the cyano group at this position is conducive to the polymerization reaction of the cyanoacrylic acid derivative monomer. This is because the cyano group is an electron-withdrawing group. During the polymerization reaction, the carbon atom connected to the cyano group can form a relatively stable anionic active center, thereby continuing the chain growth until the chain terminates. On the other hand, the cyano group at this position can react with the lithium metal in the lithium metal, thereby forming a stable chemical connection between the polymer Poly and the lithium-containing metal. As a non-limiting example, at least one of Y1 and Y2 is a cyano group. In some embodiments, Y1 and Y2 are both cyano groups. As a non-limiting example, at least one of Y1 and Y2 is a cyano group. In some embodiments, Y1 and Y2 are both cyano groups. As a non-limiting example, at least one of Y1 and Y2 is a cyano group bonded to the lithium metal in the lithium-containing metal to form a linker. As a non-limiting example, at least one of Y1 and Y2 is a linker formed by a cyano group bonded to the lithium metal in the lithium-containing metal.

[0274] In this application, the term "cyanoacrylic acid derivative monomer" refers to a Derivatives of the backbone shown are used as monomers for the in situ polymerization reaction in this application. The ends marked with an asterisk "*" can be connected to the aforementioned Rf or EO blocks via a linker such as an ester or amide group. For A1 and A2, O corresponds to an ester bond, S corresponds to a thioester bond, and NH corresponds to an amide bond.

[0275] In this application, the term "C 1-3 "Alkylene" refers to an alkylene group containing 1, 2 or 3 carbon atoms, suitable examples of which are methylene (-CH2-), ethylene (-CH2CH2- or -CH(CH3)-), propylene (-CH2CH2CH2-, -CH2CH(CH3)- or -C(CH3)2-).

[0276] The polymer Poly can be a copolymer comprising repeating units of structure (U1) and repeating units of structure (U2). The aforementioned polymer Poly can form a stable chemical bond between the cyano group on the side group of the main chain and lithium metal, thereby achieving stable chemical connection between the polymer layer and the lithium-containing metal.

[0277] In some embodiments, in the structure of the polymer Poly, X1and X2are each independently H or a cyano group, a nitro group, or -NR 21 R 22 ; wherein R 21 and R 22 are each independently H or C 1-3 alkyl. R 21 and R 22 may be each independently H or methyl. In some embodiments, R 21 and R 22 are both methyl.

[0278] The introduction of an electron-withdrawing group in at least one of X1and X2in the polymer Poly can facilitate the reactivity of the carbon-carbon double bond in the cyano acrylate derivative monomer (such as the cyano acrylate derivative monomer) during the formation of the polymer layer, promote the in-situ polymerization reaction, and facilitate the more compact and uniform coating of the polymer layer on the lithium-containing metal surface.

[0279] In some embodiments, in the structure of the polymer Poly, A1and A2are each independently O, S, or NH. In some embodiments, A1and A2are each independently O or NH. In some embodiments, A1is O. In some embodiments, A1is NH. In some embodiments, A2is O. In some embodiments, A2is NH. In some embodiments, A1and A2are both O. In some embodiments, A1and A2are both NH.

[0280] The fluoroaliphatic chain Rfand the EO block can be each independently grafted to the linear carbon chain through an ester bond, an amide bond, or a thioester bond, thereby flexibly selecting the corresponding polymerizable monomer.

[0281] In the present application, the polymerizable monomer refers to a monomer that can be used for polymerization. Unless otherwise specified, it refers to a monomer that can form the polymer Poly described in the present application through polymerization.

[0282] In some embodiments, Rd is a C 1-4 hydrocarbon group; optionally, Rd is a C 1-4 alkyl group, which can be methyl, ethyl, propyl, or butyl; further optionally, Rd is a C 1-3Alkyl can be methyl, ethyl or propyl; further optionally, Rd is methyl.

[0283] In some embodiments, Rd is a hydrocarbon group substituted by Q1, and Q1 can be selected from the following substituents: cyano, -C(=O)NH2, -OC(=O)NHR 6 and -S(=O)2F,R 6 It can be H or an alkyl group.

[0284] In some embodiments, Rd is C substituted with Q1 1-4 In some embodiments, Rd is C substituted by Q1 1-4 Alkyl; here substituted C 1-4 The alkyl group may further be methyl, ethyl, propyl or butyl, and may further be C 1-3 In some embodiments, Rd is a methyl group substituted with Q1.

[0285] In some embodiments, Q1 is cyano, -C(=O)NH2, -OC(=O)NHR 6 or -S(=O)2F,R 6 It can be H or alkyl. In some embodiments, R 6 is H. In some embodiments, R 6 is an alkyl group, which may further be C 1-6 Alkyl, further can be C 1-3 Alkyl, further can be methyl, ethyl or propyl. In some embodiments, R 6 It is a methyl group.

[0286] Functional substituents can be introduced at the end of the EO block to better optimize the performance of the polymer layer and lithium metal secondary battery as needed. For example, the introduction of a cyano group can further enhance the chemical bonding between the polymer Poly and lithium metal; the introduction of a fluorosulfonyl group (-S(=O)2F) can induce uniform deposition of lithium ions; the introduction of an amide group (-C(=O)NH2) can enhance the elastic modulus of the protective layer; the introduction of a carbamate group (such as -OC(=O)-NHR) can enhance the elastic modulus of the protective layer; and the introduction of a urea group (such as -OC(=O)-NHR) can enhance the performance of the polymer layer and the lithium metal secondary battery. 6 , where R 6 It can be H or alkyl), and the elasticity of the material can be improved by matching soft and hard segments

[0287] In some embodiments, the structure of the polymer Poly comprises m repeating units represented by formula (U1) and n repeating units represented by formula (U2).

[0288] By controlling the number of the two repeating units represented by formula (U1) and formula (U2) in the polymer Poly, the flexibility and elasticity of the polymer layer can be simultaneously regulated, thereby regulating the elastic deformation of the polymer layer and regulating the degree of fit between the polymer layer and the substrate and between the polymer layer and the isolation membrane; larger elastic deformation is conducive to better adapting to the larger volume expansion of the negative electrode side during charging, which can reduce or avoid the rupture of the protective layer and thus achieve a longer-term protective effect; better flexibility is conducive to close fit between the polymer layer and the lithium metal and between the polymer layer and the isolation membrane, reducing interfacial impedance, and helping to improve the energy density and power density of the battery.

[0289] In some embodiments, in the structure of the polymer Poly, m repeating units of formula (U1) and n repeating units of formula (U2) are arranged linearly. In this case, the two repeating units of formula (U1) and formula (U2) form a linear carbon chain with good flexibility, which is more conducive to the flexibility control of the polymer Poly.

[0290] In some embodiments, formula (U1) and formula (U2) jointly participate in the formation of a linear carbon chain in the polymer Poly.

[0291] In some embodiments, the polymer Poly has a general structure as shown in formula (P1):

[0292] The definitions of m and n are the same as above.

[0293] In this application, the asterisks "*" on either side of the general structure of Formula (P1) are conventional notations in the art, representing the end groups of the linear carbon chain of the polymer Poly. In this application, the end groups of the polymer Poly, unless otherwise specified, refer to the end groups formed by the polymerization reaction of carbon-carbon double bonds. The type of end groups is related to factors such as the initiator used and the end-capping group in the termination reaction. When "*" is used to describe the end groups of the polymer Poly, it can be understood in conjunction with the relevant description of the polymerization reaction in this application, and those skilled in the art can correctly understand the structure of the polymer Poly.

[0294] In formula (P1), m+n is numerically equal to the degree of polymerization of the polymer Poly. By controlling m+n, the molecular weight of the polymer Poly can be regulated. By controlling m / n, the ratio of the number of the two repeating units in the polymer Poly can be regulated. The polymer Poly shown in formula (P1) has a controllable number of repeating units shown in formula (U1) and repeating units shown in formula (U2), and at the same time has a flexible linear carbon chain, which is more conducive to the flexible regulation of the polymer Poly, and is also more conducive to the cyanide group of the main chain side group to fully contact the metallic lithium in the lithium-containing metal, thereby making the polymer Poly and the lithium-containing metal fit more tightly, with more chemical bonding sites and a stronger bond.

[0295] In some embodiments, the first side chains in the polymer Poly are all introduced by formula (U1). In this case, Rf only exists in the repeating unit represented by formula (U1).

[0296] In some embodiments, the second side chains in the polymer Poly are introduced by formula (U2). In this case, the EO block only exists in the repeating unit represented by formula (U2).

[0297] In some embodiments, in the polymer Poly, the first side chains are introduced through formula (U1), and the second side chains are introduced through formula (U2).

[0298] In some embodiments, in the polymer Poly, the fluorine substitution rate in any Rf is independently ≥50%. In the polymer Poly, the fluorine substitution rate in any Rf can also be independently any of the following percentages, or independently selected from the interval consisting of any of the following percentages and 100%, or independently selected from the interval consisting of any two of the following percentages: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, 95%, 96%, 97%, 98%, 99%. The interval consisting of any one percentage and 100% is, for example, 50% to 100%, 55% to 100%, 60% to 100%, 65% to 100%, 70% to 100%, 80% to 100%, etc. Non-limiting examples of the interval consisting of any two percentages are 50% to 99%, 55% to 99%, etc. In some embodiments, the fluorine substitution rate of at least one Rf in the polymer Poly is 100%. In some embodiments, the fluorine substitution rate of any Rf in the polymer Poly is 100%.

[0299] In some embodiments, in the polymer Poly, the fluorine substitution rate in any Rf is independently ≥55%.

[0300] In this application, the "fluorine substitution rate in Rf" refers to the molar percentage of fluorine atoms, based on the number of replaceable hydrogen atoms in the Rf group. The "number of replaceable hydrogen atoms" can be understood as the number of replaceable sites in the Rf group, that is, the maximum number of hydrogen atoms that can be attached to carbon atoms and any heteroatoms (such as phosphorus atoms, nitrogen atoms, sulfur atoms, etc.). The hydrogen atoms can also be replaced by other elements (in this case, the sites occupied by other elements are also included in the base number).

[0301] As a non-limiting example of Rf, The fluorine substitution rate is 8 / 11, about 72.7%; The fluorine substitution rate is 100%; The fluorine substitution rate is 13 / 17, about 76.5%; the fluorine substitution rate in the group of Formula (I) is 6 / 9, about 66.7%; the fluorine substitution rate in the group of Formula (I) is 8 / 14, about 57.1%; the fluorine substitution rate in the group of Formula (I) is 100%.

[0302] In some embodiments, at least 50% of the Rf in the polymer Poly satisfy a fluorine substitution rate ≥ 80%, or ≥ 90%.

[0303] In some embodiments, at least 60% of the Rf in the polymer Poly satisfy a fluorine substitution rate ≥ 70%, or ≥ 80%, or ≥ 90%.

[0304] In some embodiments, at least 70% of the Rf in the polymer Poly satisfy a fluorine substitution rate ≥ 60%, or ≥ 70%, or ≥ 80%, or ≥ 90%.

[0305] In some embodiments, at least 80% of the Rf in the polymer Poly satisfy a fluorine substitution rate ≥ 50%, or ≥ 60%, or ≥ 70%, or ≥ 80%, or ≥ 90%.

[0306] In the present application, for the percentage interval defined with “≥”, such as ≥ 50%, ≥ 60%, if no other limitation, the upper limit is 100%, i.e. ≥ 50%, ≥ 60% have the same meaning as 50% ~ 100%, 60% ~ 100%, respectively. This definition is applicable to but not limited to the value interval of the fluorine substitution rate.

[0307] In some embodiments, the number of fluorine atoms in any one Rf in the polymer Poly is independently ≥ 4. The number of fluorine atoms in any one Rf in the polymer Poly can also be independently any one of the following values, or independently greater than or equal to any one of the following values, or independently a range consisting of any two of the following values: 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. Non-limiting examples of the range consisting of any two of the above values include 4 ~ 20, 4 ~ 16, 4 ~ 15, 4 ~ 13, 5 ~ 20, 5 ~ 16, 5 ~ 15, 5 ~ 13, 6 ~ 20, 6 ~ 16, 6 ~ 15, 6 ~ 13, 8 ~ 20, 8 ~ 16, 8 ~ 15, 8 ~ 13, 4 ~ 10, etc.

[0308] In some embodiments, the number of fluorine atoms in any one Rf in the polymer Poly is independently ≥ 5.

[0309] In some embodiments, the number of fluorine atoms in any one Rf in the polymer Poly is independently an integer selected from 4 ~ 20.

[0310] In some embodiments, in the polymer Poly, the number of fluorine atoms in any Rf is independently an integer selected from 4 to 16.

[0311] In some embodiments, in the polymer Poly, the number of fluorine atoms in any Rf is independently an integer selected from 4 to 15.

[0312] In some embodiments, in the polymer Poly, the number of fluorine atoms in any Rf is independently an integer selected from 5 to 15.

[0313] In some embodiments, in the polymer Poly, the number of fluorine atoms in any Rf is independently an integer selected from 4 to 13.

[0314] In some embodiments, in the polymer Poly, the number of fluorine atoms in any Rf is independently an integer selected from 4 to 10.

[0315] In some embodiments, the mass percentage of fluorine in the polymer Poly is 15% to 44%. The mass percentage of fluorine in the polymer Poly can also be any of the following percentages or a range consisting of any two of the following percentages: 15%, 20%, 25%, 30%, 35%, 40%, 44%. Non-limiting examples of the range consisting of any two percentages include 15% to 44%, 20% to 44%, 25% to 44%, 30% to 44%, 15% to 41%, 20% to 41%, 25% to 41%, 30% to 41%, etc.

[0316] In some embodiments, the mass percentage of fluorine element in the polymer Poly is 15% to 41%.

[0317] In some embodiments, the mass percentage of fluorine element in the polymer Poly is 20% to 41%.

[0318] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0319] The fluorine substitution rate in any Rf is independently ≥50%;

[0320] The number of fluorine atoms in any Rf is independently ≥ 4;

[0321] The mass percentage of fluorine element in the polymer Poly is 15% to 44%.

[0322] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0323] The fluorine substitution rate in any Rf is independently ≥55%;

[0324] The number of fluorine atoms in any Rf is independently ≥5, optionally, the number of fluorine atoms in any Rf is independently 5 to 15;

[0325] The mass proportion of fluorine element in the polymer Poly is 15% to 41%, optionally 20% to 41%.

[0326] By controlling the fluorine substitution rate in Rf, by controlling the number of fluorine atoms in Rf, and by controlling the mass proportion of fluorine element in polymer Poly in one or more ways, it is possible to better promote the uniform deposition of lithium ions, inhibit the formation of lithium dendrites, improve the lithium ion cycle life and reduce the short circuit risk, and alleviate the volume expansion of the lithium metal negative electrode side. In addition, it can also be beneficial to the application of the polymer layer in lithium metal secondary batteries that perform charge and discharge cycles at a high current density.

[0327] Taking controlling the mass proportion of fluorine in polymer Poly as an example, it is beneficial to improve the deposition morphology of lithium dendrites in lithium metal batteries and alleviate the volume expansion of lithium metal negative electrodes, which is beneficial to the application of polymer layers in lithium metal secondary batteries that perform charge and discharge cycles at high current density.

[0328] In some embodiments, in the polymer Poly, any Rf independently contains 2 to 10 main chain carbon atoms, that is, in the polymer Poly, the number of main chain carbon atoms contained in any Rf independently is 2 to 10. In the polymer Poly, the number of main chain carbon atoms contained in any Rf can also independently be any of the following values ​​or independently selected from the range consisting of any two of the following values: 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0329] In some embodiments, in the polymer Poly, any Rf independently contains 2 to 8 main chain carbon atoms.

[0330] In some embodiments, in the polymer Poly, any Rf independently contains 3 to 8 main chain carbon atoms.

[0331] In some embodiments, in the polymer Poly, any Rf independently contains 3, 4, 5, 6, 7 or 8 main chain carbon atoms.

[0332] In some embodiments, in the polymer Poly, the number of carbon atoms in any Rf is independently an integer selected from 2 to 10. In the polymer Poly, the number of carbon atoms in any Rf can also be independently any of the following values ​​or independently selected from the range consisting of any two of the following values: 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0333] In some embodiments, in the polymer Poly, the number of carbon atoms in any Rf is independently an integer selected from 2 to 8.

[0334] In some embodiments, in the polymer Poly, the number of carbon atoms in any Rf is independently an integer selected from 3 to 8.

[0335] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0336] Each Rf independently contains 2 to 10 main chain carbon atoms;

[0337] The number of carbon atoms in any one Rf is independently an integer selected from 2 to 10.

[0338] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0339] Any Rf independently contains 2 to 8 main chain carbon atoms, optionally, any Rf independently contains 3 to 8 main chain carbon atoms;

[0340] The number of carbon atoms in any Rf is independently an integer selected from 2 to 8. Alternatively, the number of carbon atoms in any Rf is independently an integer selected from 3 to 8.

[0341] In some embodiments, at least one Rf can be independently fluorinated C 2-10 In some embodiments, any one of Rf can be independently fluorinated C 2-10 Further, based on any of the above embodiments, the number of carbon atoms in any Rf can also be independently any of the following values ​​or independently selected from the range consisting of any two of the following values: 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0342] In some embodiments, C 2-10The alkyl group may be, for example, but is not limited to, ethylpropyl, butyl, pentyl, hexyl, heptyl, octyl, isopropyl, isobutyl, tert-butyl, isopentyl, tert-pentyl, neopentyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 2-methylhexyl, 3-methylhexyl, 2,2-dimethylpentyl, 3,3-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 3-ethylpentyl, 2,2,3-trimethylbutyl, 2-methylheptyl, 3-methylheptyl, 4- methylheptyl, 2,2-dimethylhexyl, 3,3-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 3,4-dimethylhexyl, 3-ethylhexyl, 2,2,3-trimethylpentanyl, 2,2,4-trimethylpentanyl, 2,3,3-trimethylpentanyl, 2,3,4-trimethylpentanyl, 2-methyl-3-ethylpentanyl, 3-methyl-3-ethylpentanyl, 2,2,3,3-tetramethylbutanyl, nonyl, decyl, and the like.

[0343] The length of the Rf side chain can be adjusted by controlling the number of carbon atoms in Rf, thereby giving the polymer layer appropriate elasticity and better inhibiting the polymer layer from rupturing under large volume deformation.

[0344] In some embodiments, in the structure of the polymer Poly, one, more or all Rf independently contain one or more heteroatoms selected from the group consisting of iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus. Optionally, the number of heteroatoms in any one, more or all Rf is independently 1 or more. Further optionally, the number of heteroatoms in any one, more or all Rf is selected from 1 or 2 to 6. Further optionally, the number of heteroatoms in any one, more or all Rf is selected from 1 or 2 to 5. In some embodiments, the number of oxygen atoms in one, more or all Rf is 1, 2, 3, 4 or 5. In some embodiments, the number of nitrogen atoms in one, more or all Rf is 1, 2 or 3. In some embodiments, the number of sulfur atoms in one, more or all Rf is 1, 2 or 3. In some embodiments, the number of phosphorus atoms in one, more or all Rf is 1 or 2. In some embodiments, the number of iodine atoms in one, more, or all Rf is 1, 2, 3, 4, 5, or 6. In some embodiments, the number of silicon atoms in one, more, or all Rf is 1 or 2. In some embodiments, the number of boron atoms in one, more, or all Rf is 1 or 2.

[0345] In some embodiments, in the structure of the polymer Poly, one, more or all Rf satisfy one or more of the following characteristics:

[0346] The number of oxygen atoms in one, more or all Rf is 1, 2, 3, 4 or 5;

[0347] The number of nitrogen atoms in one, more or all Rf is 1, 2 or 3;

[0348] The number of sulfur atoms in one, more or all Rf is 1, 2 or 3;

[0349] The number of phosphorus atoms in one, more or all Rf is 1 or 2;

[0350] The number of iodine atoms in one, more or all Rf is 1, 2, 3, 4, 5 or 6;

[0351] The number of silicon atoms in one, more or all of Rf is 1 or 2; and

[0352] The number of boron atoms in one, more than one or all of Rf is 1 or 2.

[0353] In some embodiments, in the structure of the polymer Poly, one, more or all of Rf contain one or more selected from iodine, -NR 12 -, -O-, -S-, -S(O)2-, >Si<, >B- and >P(=O)-, wherein R 12 H or C 1-3 Alkyl. Optionally, R 12 is H or methyl. Further optionally, R 12 For H.

[0354] In some embodiments, in the structure of the polymer Poly, one, more or all Rf contain one or more atoms or atomic groups selected from the group consisting of -O-, -S(O)2- and -(O=)P(O-)2. In some embodiments, one, more or all Rf contain one or more -O-. In some embodiments, one, more or all Rf contain -S(O)2F. In some embodiments, one, more or all Rf contain -(O=)P(O-)2.

[0355] In this application, the term "radical" refers to a group having two or more atoms.

[0356] By introducing other heteroatoms besides fluorine atoms into Rf, such as one or more heteroatoms of iodine, nitrogen, oxygen, sulfur, silicon, boron, phosphorus, etc., special properties can be given to the polymer layer. For example, phosphorus has a certain flame retardant effect. For another example, iodine can also play a certain role in regulating lithium ion deposition. For another example, fluorosulfonyl group (-S(=O)2F) has a certain effect on improving the ionic conductivity of the polymer layer and promoting the uniform deposition of lithium ions.

[0357] In some embodiments, in the structure of the polymer Poly, each Rf is independently a linear structure or a branched structure.

[0358] A linear Rf is advantageous for improving the elasticity of the polymer material. A branched Rf is advantageous for improving the swelling ability of the electrolyte membrane, and in turn, the ionic conductivity.

[0359] In some embodiments, in the structure of the polymer Poly, each Rf is independently a saturated structure or an unsaturated structure.

[0360] When the fluorine-substituted aliphatic chain has a saturated structure, it can impart a higher activity to the molecular chain of the polymer Poly, which is advantageous for improving the elasticity regulation of the polymer layer. In addition, by introducing an unsaturated bond in Rf, the polymer layer can be cross-linked, and the elastic modulus of the polymer protective layer can be enhanced.

[0361] In some embodiments, in the structure of the polymer Poly, each Rf is independently as shown in formula (III-1), formula (III-2), or formula (III-3):

[0362]

[0363] wherein,

[0364] In formula (III-1), m3 is an integer selected from 2 to 10; R 31 , R 32 , and R 3 each occurrence is independently H or F; the structure shown in formula (III-1) contains at least 4 F atoms;

[0365] In formula (III-2), m 4a and m 4b are each independently an integer selected from 1 to 9; R 41a , R 42a , R 4a , R 41b , R 42b , and R 4b each occurrence is independently H or F; the structure shown in formula (III-2) contains at least 4 F atoms;

[0366] In formula (III-3), m5 is an integer selected from 2 to 10; R 51 and R 52 each occurrence is independently H or F; the structure shown in formula (III-3) contains at least 4 F atoms.

[0367] In formula (III-1), m3 is an integer selected from 2-10. m3 can also be any one of the following values or a range selected from any two of the following values: 2, 3, 4, 5, 6, 7, 8, 9, and 10; m3 can also be selected from any one of the following ranges: 3-10, 3-8, etc.

[0368] In formula (III-1), R 31 , R 32 , and R 3 are each independently H or F, and the structure represented by formula (III-1) contains at least 4 F atoms. The number of F atoms in the structure represented by formula (III-1) can further be any suitable value defined above, which can refer to but is not limited to the number of F atoms in Rf, the F substitution rate in Rf, the mass proportion of F elements in the polymer Poly, the number of main chain carbon atoms contained in Rf, the number of carbon atoms in Rf, etc.

[0369] The structure of formula III-1 is a linear saturated fluorinated aliphatic chain, which can on the one hand impart better elasticity to the polymer layer, reduce or avoid the rupture of the polymer layer under large volume deformation, and on the other hand effectively promote the uniform deposition of lithium ions through the F element, inhibit the formation of lithium dendrites, and relieve the volume expansion on the lithium metal negative electrode side.

[0370] In formula (III-2), m 4a and m 4b are each independently an integer selected from 1-9, and can also be each independently any one of the following values or a range selected from any two of the following values: 1, 2, 3, 4, 5, 6, 7, 8, and 9. m 4a and m 4b may also be each independently selected from any one of the following ranges: 2-, 2-8, 3-8, 3-6, etc.

[0371] In formula (III-2), R 41a , R 42a , R 4a , R 41b , R 42b , and R 4b are each independently H or F, and the structure represented by formula (III-2) contains at least 4 F atoms. The number of F atoms in the structure represented by formula (III-2) can further be any suitable value defined above, which can refer to but is not limited to the number of F atoms in Rf, the F substitution rate in Rf, the mass proportion of F elements in the polymer Poly, the number of main chain carbon atoms contained in Rf, the number of carbon atoms in Rf, etc.

[0372] The structure of formula III-2 can introduce phosphorus elements, and in addition, the phosphate groups therein have a flame-retardant effect, which is conducive to improving the safety performance of the battery cell.

[0373] In formula (III-3), m5 is an integer selected from 2 to 10, and may be any of the following values ​​or an interval consisting of any two of the following values: 2, 3, 4, 5, 6, 7, 8, 9, and 10. m5 may also be selected from any of the following ranges: 3 to 10, 3 to 8, etc.

[0374] In formula (III-3), R 51 and R 52 Each occurrence is independently H or F; the structure represented by formula (III-3) contains at least 4 F atoms. The number of fluorine atoms in the structure represented by formula (III-3) can further be any suitable value defined above, with reference to but not limited to the number of fluorine atoms in Rf, the fluorine substitution rate in Rf, the mass percentage of fluorine element in the polymer Poly, the number of main chain carbon atoms contained in Rf, the number of carbon atoms in Rf, etc.

[0375] The structure of formula III-3 can introduce a fluorosulfonyl group, which has a certain positive effect on improving the ionic conductivity of the polymer layer.

[0376] In some embodiments, the polymer Poly satisfies one or more of the following characteristics:

[0377] m3 is an integer selected from 3 to 10; alternatively, m3 is an integer selected from 3 to 8;

[0378] m 4a and m 4b are each independently an integer selected from 2 to 9; optionally, m 4a and m 4b are each independently an integer selected from 2 to 8; further optionally, m 4a and m 4b are independently an integer selected from 3 to 8; further optionally, m 4a and m 4b Each independently represents an integer selected from 3 to 6

[0379] m5 is an integer selected from 3 to 10; alternatively, m5 is an integer selected from 3 to 8.

[0380] In some embodiments, in the structure of the polymer Poly, the structure of Rf is as shown in formula (III-1); or, the structure of Rf is as shown in formula (III-2); or, the structure of Rf is as shown in formula (III-3).

[0381] In some embodiments, in the structure of the polymer Poly, the number of H atoms in each occurrence of formula (III-1) is 0, 1, 2, 3, or 4; the number of H atoms in each occurrence of formula (III-2) is 0, 1, 2, 3, 4, 5, or 6; and the number of H atoms in each occurrence of formula (III-3) is 0, 1, 2, 3, or 4.

[0382] In some embodiments, the number of H atoms in formula (III-1) is 0.

[0383] In some embodiments, the number of H atoms in formula (III-2) is 0.

[0384] In some embodiments, the number of H atoms in formula (III-3) is 0.

[0385] By controlling the number of H atoms, the number of sites available for substitution by fluorine elements can be regulated.

[0386] In some embodiments, in the structure of the polymer Poly, any one Rf is independently any one of the following structures:

[0387]

[0388] Rf 10 Rf 01 Rf 02 Rf 03 Rf 04 Rf 05 Rf 06 Rf 07 Rf 08 Rf 09 Rf 01 Rf 02 Rf 03 Rf 05 Rf 07 Rf 08 Rf 09 Rf 10 .

[0389] In some embodiments, the number average molecular weight of the polymer Poly is selected from the group consisting of 10 kDa to 200 kDa; alternatively, the number average molecular weight of the polymer Poly is selected from the group consisting of 40 kDa to 100 kDa; alternatively, the number average molecular weight of the polymer Poly is selected from the group consisting of 50 kDa to 80 kDa.

[0390] The number average molecular weight of the polymer Poly can also be any one of the following or selected from the interval consisting of any two of the following: 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 25, 26, 28, 30, 35, 40, 44, 45, 46, 48, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, etc. (all in kDa).

[0391] By adjusting the polymerization degree or molecular weight of the polymer Poly, the molecular chain length of the polymer Poly can be adjusted, which can achieve effective coating of lithium metal, maintain stable chemical connection, and also affect the compactness and uniformity of the polymer layer.

[0392] In some embodiments, the lithium-containing metal contains lithium single element or lithium alloy. The lithium alloy contains lithium element, and can also contain one or more elements selected from the group consisting of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium, but is not limited thereto.

[0393] Lithium metal has the highest specific capacity (3860 mAh / g) and the lowest electrochemical potential (-3.04 V, relative to the standard hydrogen electrode) among all anode materials of lithium-based batteries, and is a preferred anode material for lithium metal batteries, which helps to achieve high energy density.

[0394] In some embodiments, the amount of lithium metal in the lithium-containing metal relative to the amount of the polymer Poly is greater than or equal to the amount of catalyst, in terms of molar ratio.

[0395] In the lithium metal anode material provided in the present application, the lithium-containing metal only needs to provide a catalyst amount, that is, to successfully catalyze the in-situ polymerization reaction of the cyano alkenyl carboxylic acid derivative monomer (such as cyano acrylate derivative monomer) on the surface of the lithium-containing metal. The amount of lithium metal relative to the amount of the polymer Poly only needs to be the catalyst amount, that is, to catalyze the in-situ polymerization reaction of the cyano alkenyl carboxylic acid derivative monomer (such as cyano acrylate derivative monomer) on the surface of the lithium metal.

[0396] In a second aspect, the present application provides a negative electrode tab, which comprises a lithium-containing layer and a polymer layer arranged in a stack, and the negative electrode tab comprises the lithium metal anode material of the first aspect of the present application.

[0397] The lithium-containing layer comprises the lithium-containing metal in the lithium metal anode material, and the polymer layer comprises the polymer Poly in the lithium metal anode material.

[0398] In this application, “active material” and “active substance” have the same meaning and can be used interchangeably; “positive electrode active substance” and “positive electrode active material” have the same meaning and can be used interchangeably; “negative electrode active substance” and “negative electrode active material” have the same meaning and can be used interchangeably.

[0399] In the present application, the "negative electrode sheet substrate" can provide a negative electrode active material for a lithium metal battery. The negative electrode sheet substrate in the negative electrode sheet includes at least a lithium-containing layer in contact with the polymer layer, that is, the lithium-containing layer is located at the outermost layer of the negative electrode sheet substrate. In other words, the outermost layer of at least one side of the negative electrode sheet substrate is a lithium-containing layer. In one embodiment, the negative electrode sheet substrate is composed of a lithium-containing layer. The polymer layer is chemically connected to at least a portion of the lithium in the lithium-containing layer. Further, "chemical connection" here refers to covalent connection. The thickness of the negative electrode sheet substrate can be the thickness of the lithium negative electrode in a conventional lithium metal battery. The "lithium negative electrode" here refers to the thickness of the negative electrode active material layer provided by lithium metal or lithium alloy. Non-limiting examples of the thickness of the lithium-containing layer are 5 μm to 40 μm. The thickness of the lithium-containing layer can also be selected from the interval consisting of any one or two of the following thicknesses: 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, etc.

[0400] In this application, the term "lithium-containing layer" refers to a structural layer containing metallic lithium. The lithium-containing layer can be essentially composed of lithium (Li) metal, or a lithium alloy, or a composition comprising lithium metal and a lithium alloy (e.g., a composition essentially composed of lithium metal and a lithium alloy). The lithium in the lithium-containing layer can play multiple roles. On the one hand, it can catalyze the in-situ polymerization reaction of the cyano-olefin carboxylic acid derivative monomer, on the other hand, it can form a stable covalent bond with the cyano group carried by the polymer Poly, and on the other hand, it can also serve as a lithium source for the negative electrode active material. The thickness of the lithium-containing layer can be any suitable thickness, as long as it is sufficient to provide a catalyst amount that can support the in-situ polymerization reaction of the cyano-olefin carboxylic acid derivative monomer. For example, it can also be the thickness of the lithium negative electrode in a conventional lithium metal battery. When the thickness of the lithium-containing layer is relatively thin, a second negative electrode active material layer can be provided on the side of the lithium-containing layer away from the polymer layer. In this case, the negative electrode substrate includes the lithium-containing layer and the second negative electrode active material layer. The composition and content of the lithium-containing layer and the second negative electrode active material layer can be the same or different.

[0401] In the present application, the lithium-containing layer "substantially consists of lithium metal" means that the weight proportion of metallic lithium is very high. The proportion described by "substantially" here is, for example, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, equal to 100%, etc.

[0402] The negative electrode sheet comprises lithium metal negative electrode material distributed in the lithium-containing layer and the polymer layer at the same time, and on at least one side of the negative electrode sheet, the lithium-containing layer is stably connected with a dense and uniform polymer layer by chemical bonding, the polymer layer has certain elasticity, flexibility and swelling property, can firmly, tightly and durably adhere the polymer layer and the lithium-containing layer, the polymer layer and the separator, can better adapt to the large volume expansion of the negative electrode side in the charging process, and can play a long-term protective layer role at the negative electrode of the lithium metal secondary battery. The polymer layer can effectively inhibit the contact reaction between the electrolyte and the lithium metal, reduce the consumption of the electrolyte and the lithium metal, prolong the cycle life, and also promote the uniform deposition of lithium ions by using the fluorinated aliphatic chain Rf in the lithium metal negative electrode material, inhibit the formation of lithium dendrites, and relieve the volume expansion of the lithium metal negative electrode side. In addition, the comprehensive performance of the elasticity, flexibility and swelling property of the polymer layer is not only conducive to the tight adhesion between the polymer layer and the lithium-containing layer, but also conducive to the good ionic conductivity, the reduction of interface polarization and the reduction of interface impedance, so that the lithium metal secondary battery can realize high energy density, power density, charge-discharge cycle stability and high safety performance in the presence of the polymer layer.

[0403] In some embodiments, the lithium-containing layer consists essentially of the lithium metal. In some of them, the lithium-containing layer is made of lithium single element. In some of them, the lithium-containing layer is made of lithium alloy.

[0404] In this application, the lithium-containing layer "consists essentially of lithium metal" means that the weight percentage of lithium metal is very high, for example, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, equal to 100%, etc.

[0405] In some embodiments, the polymer layer also contains a first electrolyte, and the first electrolyte contains a lithium salt (denoted as a first electrolyte lithium salt) and a solvent (denoted as a first electrolyte solvent).

[0406] In some embodiments, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium difluoro(oxalato)borate (LiDFOB), lithium perchlorate (LiClO4) and lithium bis(oxalato)borate (LiBOB).

[0407] In some embodiments, the first electrolyte solvent is selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), diphenyl carbonate (DPhC), dibutyl carbonate (DBC), butylene carbonate (BC), ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), dioxolane (DOL), methyl nonafluorobutyl ether (MFE), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE-458), octafluoropentyl-tetrafluoroethyl ether (F-EAE), 1,2-bis(cyanoethoxy)ethane (DENE), diphenyl ether (DPE) and 18-crown-6.

[0408] In some embodiments, the negative electrode plate satisfies one or more of the following characteristics:

[0409] The lithium salt includes one or more of lithium hexafluorophosphate, tetrafluoroboric acid, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium perchlorate and lithium bis(oxalate)borate;

[0410] The first electrolyte solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, butylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxolane, methyl nonafluoro-n-butyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, octafluoropentyl-tetrafluoroethyl ether, 1,2-bis(cyanoethoxy)ethane, diphenyl ether and 18-crown-6.

[0411] In some embodiments, the concentration of the lithium salt in the first electrolyte is selected from 0.2 mol / L to 8 mol / L; alternatively, the concentration of the lithium salt in the first electrolyte is selected from 0.5 mol / L to 5 mol / L; further alternatively, the concentration of the lithium salt in the first electrolyte is selected from 0.5 mol / L to 2 mol / L. The concentration of the lithium salt in the first electrolyte can also be any of the following concentrations or an interval consisting of any two of the following concentrations: 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, etc. (all units are mol / L).

[0412] The polymer layer of the lithium metal negative electrode material contains an electrolyte (which can be recorded as the first electrolyte). The concentration of lithium salt in the first electrolyte can affect the deposition morphology of lithium ions. The concentration of lithium salt can change the Li +The solvation effect affects the composition of the solid electrolyte interface film (SEI film) and the deposition morphology of lithium ions. By controlling the lithium salt in the electrolyte at a more appropriate concentration, it is more conducive to promoting dense and uniform deposition of lithium ions and reducing the volume expansion of the negative electrode side. In addition, by controlling the lithium salt in the electrolyte at a more appropriate concentration, the polymer layer can also have more suitable mechanical properties, such as flexibility and elasticity, and can also achieve better lithium ion conductivity during charging and discharging. When the lithium salt concentration is too high, the mechanical properties of the polymer layer may deviate from the optimal range. When the lithium salt concentration is too low, the lithium ion conductivity during charging and discharging may deviate from the larger range.

[0413] In some embodiments, the mass percentage of the first electrolyte in the polymer layer is 20% to 80%; alternatively, the mass percentage of the first electrolyte in the polymer layer is 30% to 60%; further alternatively, the mass percentage of the first electrolyte in the polymer layer is 40% to 60%; and even further alternatively, the mass percentage of the first electrolyte in the polymer layer is 40% to 55%. The mass percentage of the first electrolyte in the polymer layer can also be any of the following percentages or a range consisting of any two of the following percentages: 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, etc. Non-limiting examples of a range consisting of any two percentages include 30% to 80%, 40% to 80%, 30% to 60%, 40% to 60%, 30% to 55%, 40% to 55%, etc.

[0414] In some embodiments, the mass ratio of the polymer Poly to the first electrolyte is 4:1 to 0.25:1; alternatively, the mass ratio of the polymer Poly to the first electrolyte is 3:1 to 0.5:1; further alternatively, the mass ratio of the polymer Poly to the first electrolyte is 2.5:1 to 1:1; further alternatively, the mass ratio of the polymer Poly to the first electrolyte is 7:3 to 2:1. The mass ratio of the polymer Poly to the first electrolyte can also be 4:1, 3.5:1, 3:1, 2.5:1, 7:3, 2:1, 1.5:1, 1:1, 0.9:1, 0.8:1, 0.7:1, 0.6:1, 0.5:1, 0.4:1, 0.3:1, 1:3, 1:3.5, 0.25:1, etc. It can also be selected from the interval consisting of any two of the above ratios.

[0415] By controlling the mass ratio of the first electrolyte in the polymer layer or controlling the mass ratio of the polymer Poly and the first electrolyte in the polymer layer within a more appropriate range, the electrolyte can be adjusted to have a more appropriate mass ratio in the polymer layer. The mass ratio of the electrolyte in the polymer layer can affect the elastic modulus and ionic conductivity of the protective layer. In the first electrolyte, the presence of a certain amount of lithium salt (denoted as the first electrolyte lithium salt) and solvent (denoted as the first electrolyte solvent) can plasticize the polymer layer and improve the elasticity of the polymer layer. In addition, in the process of forming the polymer layer by in situ polymerization, the lithium salt and solvent in the first electrolyte can be incorporated into the interior of the polymer layer, so that the polymer layer has a sponge-like loose porous structure on a microscopic scale, and the pores are filled with electrolyte, which can provide a path for the subsequent transmission of lithium ions.

[0416] In some embodiments, based on the first electrolyte, the swelling ratio of the polymer layer can be any of the following percentages or a range consisting of any two of the following percentages: 8%, 10%, 11%, 12%, 14%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, etc. Non-limiting examples of the swelling ratio of the polymer layer based on the first electrolyte include 15% to 65%, 18% to 65%, 30% to 65%, 15% to 55%, 18% to 55%, 30% to 55%, 15% to 40%, 18% to 40%, 30% to 40%, etc.

[0417] In this application, "swelling rate of the polymer layer" generally refers to the value measured at 20°C to 30°C, unless otherwise specified. In some embodiments, the swelling rate of the polymer layer refers to the swelling rate at 25°C. For more information, refer to the testing methods in the "Structure and Performance Testing" section of the Examples section below.

[0418] In some embodiments, based on the first electrolyte, the swelling rate of the polymer layer at 25°C is 8% to 65%; further optionally, the swelling rate of the polymer layer at 25°C is 15% to 55%; further optionally, the swelling rate of the polymer layer at 25°C is 18% to 44%; further optionally, the swelling rate of the polymer layer at 25°C is 30% to 40%.

[0419] In some embodiments, based on the first electrolyte, the ionic conductivity of the swollen polymer layer can be any of the following values ​​or an interval selected from any two of the following values: 5mS / cm, 4.5mS / cm, 4mS / cm, 3.5mS / cm, 3mS / cm, 2.6mS / cm, 2.5mS / cm, 2mS / cm, 1.5mS / cm, 1mS / cm, 0.95mS / cm, 0.9mS / cm, 0.8mS / cm, 0.7mS / cm, 0.6mS / cm, 0.5mS / cm, 0.4mS / cm, 0.3mS / cm, 0.2mS / cm, 0 .1mS / cm, 0.09mS / cm, 0.08mS / cm, 0.07mS / cm, 0.06mS / cm, 0.05mS / cm, 0.04mS / cm, 0.03mS / cm, 0.02mS / cm, 0.01mS / cm, 0.005mS / cm, 0.001mS / cm, etc., and can also be selected from any of the following ranges: 0.001mS / cm to 5mS / cm, 0.1mS / cm to 5mS / cm, 0.5mS / cm to 5mS / cm, 0.9mS / cm to 4.8mS / cm, 0.95mS / cm to 2.6mS / cm.

[0420] In this application, 1mS / cm means 1×10 -3 S / cm.

[0421] In this application, references to "ionic conductivity of the swollen polymer layer" generally refer to values ​​measured at 20°C to 30°C, unless otherwise specified. In some embodiments, the ionic conductivity of the swollen polymer layer refers to the ionic conductivity at 25°C. For more information, see the "Structure and Performance Testing" section below in the Examples section for testing methods.

[0422] In some embodiments, based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25°C is selected from 0.001mS / cm to 5mS / cm; optionally, the ionic conductivity of the swollen polymer layer at 25°C is selected from 0.1mS / cm to 5mS / cm; alternatively, the ionic conductivity of the swollen polymer layer at 25°C is selected from 0.5mS / cm to 5mS / cm; alternatively, the ionic conductivity of the swollen polymer layer at 25°C is selected from 0.9mS / cm to 4.8mS / cm; alternatively, the ionic conductivity of the swollen polymer layer at 25°C is selected from 0.95mS / cm to 2.6mS / cm.

[0423] In some embodiments, the thickness of the polymer layer is 5 nm to 10 μm; optionally, the thickness of the polymer layer is 0.02 μm to 8 μm; further optionally, the thickness of the polymer layer is 0.05 μm to 8 μm; further optionally, the thickness of the polymer layer is 0.05 μm to 5 μm; further optionally, the thickness of the polymer layer is 0.1 μm to 5 μm. The thickness of the polymer layer can also be any of the following thicknesses or an interval consisting of any two of the following thicknesses: 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 250nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 9.5μm, 10μm, etc.

[0424] The thickness of the polymer layer on the surface of the lithium-containing metal can be controlled at a thin nanoscale, which is more conducive to the assembled battery cell showing smaller interface impedance.

[0425] In some embodiments, the elastic modulus of the polymer layer can be any of the following values ​​or an interval selected from any two of the following values: 0.1 MPa, 0.2 MPa, 0.5 MPa, 0.8 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 12 MPa, 14 MPa, 15 MPa, 16 MPa, 18 MPa, 20 MPa, 25 MPa, 29 MPa, 30 MPa, 35 MPa, 40 MPa, 41 MPa, 45 MPa, 46 MPa, 50 MPa, 60 MPa, 65 MPa, etc. Non-limiting examples of the elastic modulus of the polymer layer are: 0.1 MPa to 65 MPa, 0.5 MPa to 65 MPa, 1 MPa to 65 MPa, 10 MPa to 65 MPa, 15 MPa to 65 MPa, 18 MPa to 65 MPa, 20 MPa to 65 MPa, 29 MPa to 65 MPa, 0.1 MPa to 50 MPa, 0.5 MPa to 50 MPa, 1 MPa to 50 MPa, 10 MPa to 50 MPa, 15 MPa to 50 MPa, 18 MPa to 50 MPa, 20 MPa to 50 MPa, 29 MPa to 65 MPa. Pa~50MPa, 0.1MPa~46MPa, 0.5MPa~46MPa, 1MPa~46MPa, 10MPa~46MPa, 15MPa~46MPa, 18MPa~46MPa, 20MPa~46MPa, 29MPa~46 MPa, 0.1MPa~41MPa, 0.5MPa~41MPa, 1MPa~41MPa, 10MPa~41MPa, 15MPa~41MPa, 18MPa~41MPa, 20MPa~41MPa, 29MPa~41MPa, etc.

[0426] In this application, "elastic modulus of a polymer layer" generally refers to the value measured at 20°C to 30°C, unless otherwise specified. In some embodiments, the elastic modulus of a polymer layer refers to the elastic modulus at 25°C. For testing methods, see the "Structure and Performance Testing" section below in the Examples section.

[0427] In some embodiments, the elastic modulus of the polymer layer at 25°C is 0.1MPa~65MPa; optionally, the elastic modulus of the polymer layer at 25°C is 0.5MPa~50MPa; further optionally, the elastic modulus of the polymer layer at 25°C is 10MPa~46MPa; further optionally, the elastic modulus of the polymer layer at 25°C is 18MPa~41MPa; further optionally, the elastic modulus of the polymer layer at 25°C is 29MPa~41MPa.

[0428] In some embodiments, the elastic deformation range of the polymer layer can be selected from any one or two of the following percentages: 55%, 60%, 65%, 70%, 80%, 90%, 100%, 150%, 200%, 220%, 240%, 250%, 260%, 265%, 270%, 280%, 300%, 350%, etc. Non-limiting examples of the elastic deformation range of the polymer layer include: 55% to 350%, 55% to 300%, 55% to 280%, 150% to 350%, 150% to 300%, 150% to 280%, 160% to 350%, 160% to 300%, 160% to 280%, 168% to 350%, 168% to 300%, 168% to 280%, etc.

[0429] In this application, the "elastic deformation range of the polymer layer," unless otherwise specified, generally refers to the value tested at 20°C to 30°C. In some embodiments, the elastic deformation range of the polymer layer refers to the elastic deformation range at 25°C. For more information, see the "Structure and Performance Testing" section below in the Examples section for testing methods.

[0430] In some embodiments, the elastic deformation range of the polymer layer at 25°C is 55% to 350%; optionally, the elastic deformation range of the polymer layer at 25°C is 150% to 350%; further optionally, the elastic deformation range of the polymer layer at 25°C is 150% to 300%; further optionally, the elastic deformation range of the polymer layer at 25°C is 168% to 280%.

[0431] By controlling parameters such as the elastic modulus and elastic deformation range of the polymer layer within a more appropriate range, it is beneficial to make the polymer layer have more appropriate elasticity, better promote close contact between the polymer layer and the lithium-containing metal layer, reduce the interface impedance, and help achieve better energy density and power density.

[0432] In some embodiments, the volume expansion rate of the negative electrode plate is less than 130%, and further, can be selected from 5% to 130%. The volume expansion rate of the negative electrode plate can also be any of the following percentages or an interval consisting of any two of the following percentages: 6%, 7%, 8%, 9%, 10%, 11%, 12%, 14%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, 95%, 100%, 102%, etc. In some embodiments, the volume expansion rate of the negative electrode plate is 5% to 128%. In some embodiments, the volume expansion rate of the negative electrode plate is 5% to 102%.

[0433] In this application, references to "pole piece volume expansion rate" generally refer to values ​​measured at 20°C to 30°C, unless otherwise specified. In some embodiments, the pole piece volume expansion rate refers to the volume expansion rate at 25°C. For more information, see the "Structure and Performance Testing" test method in the Examples section below.

[0434] In some embodiments, the negative electrode substrate further includes a negative electrode current collector; the negative electrode current collector is located on a side of the lithium-containing layer away from the polymer layer.

[0435] In some embodiments, the negative electrode current collector is located between the negative electrode current collector and the lithium-containing layer with or without a second negative electrode active material layer. Furthermore, the components of the second negative electrode active material layer and the lithium-containing layer may be the same or different.

[0436] In some embodiments, the negative electrode sheet includes a negative electrode current collector, and the second negative electrode active material layer is disposed between the negative electrode current collector and the lithium-containing layer.

[0437] In some embodiments, only the outermost layer on one side of the negative electrode substrate is provided with a lithium-containing layer (see Figure 1 、 Figure 2 and Figure 3 ).

[0438] In some embodiments, the outermost layers on both sides of the negative electrode substrate are provided with lithium-containing layers (see Figure 4 and Figure 5 ). The lithium-containing layers on both sides may contain the same or different amounts of lithium. The lithium content in the lithium-containing layer may refer to the above definition. The lithium content in the second negative electrode active material layer may be selected from the lithium content in the negative electrode active material layer of a conventional lithium metal battery. Non-limiting examples of the second negative electrode active material layer include lithium metal, lithium alloy, or a combination of the two. In the case of a combination of the two, for example, different regions of the negative electrode active material layer may have different component compositions.

[0439] In this application, the "second negative electrode active material layer" can be any suitable negative electrode active material layer among the active material layers reported for lithium metal batteries. The second negative electrode active material layer can be essentially composed of lithium (Li) metal, a lithium alloy, or a combination essentially composed of lithium metal and a lithium alloy.

[0440] In some embodiments, a lithium-containing layer is provided on the outermost layers of both sides of the negative electrode substrate, and a polymer layer is provided on the surface of the lithium-containing layer on both sides (see Figure 4 and Figure 5 ); The chemical composition and content of the polymer layers on both sides may be the same or different.

[0441] In some embodiments, the negative electrode plate includes Figure 1 The structure shown includes a lithium-containing layer 130 and a polymer layer 200 in a stacked distribution. The lithium-containing layer contains lithium, lithium alloy, or a combination of both, and the lithium-containing layer herein serves as a negative active material layer; the polymer layer contains a polymer Poly, which covalently bonds (e.g., through a reaction between a cyano group in the Poly and lithium) with lithium in the lithium-containing layer to form a stable chemical linkage, such that the polymer layer is firmly attached to the surface of the lithium-containing layer. The polymer Poly can be selected from the polymers Poly described in any of the embodiments of the first aspect. The first electrolyte is as previously defined.

[0442] In some embodiments, the negative electrode tab includes a negative electrode tab substrate 100 having Figure 2 The structure shown includes a negative electrode tab substrate 100 and a polymer layer 200 in a stacked distribution; the negative electrode tab substrate 100 includes a negative current collector 110 and a lithium-containing layer 130 in a stacked distribution in sequence, and the polymer layer is located on the surface of the lithium-containing layer 130 away from the negative current collector 110. Further, the polymer layer contains a polymer Poly and a first electrolyte. The lithium-containing layer contains lithium, lithium alloy, or a combination of both, and the polymer layer contains a polymer Poly, which covalently bonds with lithium in the lithium-containing layer to form a stable chemical linkage, such that the polymer layer is firmly attached to the surface of the negative electrode tab substrate.

[0443] In some embodiments, the negative electrode tab includes a negative electrode tab substrate 100 having Figure 3 The structure shown includes a negative electrode tab substrate 100 and a polymer layer 200 in a stacked distribution; the negative electrode tab substrate 100 includes a negative current collector 110, a second negative active material layer 120, and a lithium-containing layer 130 in a stacked distribution in sequence, and the polymer layer is located on the surface of the lithium-containing layer 130 away from the negative current collector 110.

[0444] In some embodiments, the negative electrode tab includes a negative electrode tab substrate 100 having Figure 4 The structure shown includes a negative electrode tab substrate 100 and two polymer layers 200 respectively disposed on the two side surfaces of the negative electrode tab substrate 110; the negative electrode tab substrate includes a negative current collector 110, and two lithium-containing layers 130 respectively disposed on the two side surfaces of the negative current collector 110, and the lithium-containing layers 130 on the two sides of the negative electrode tab are respectively directly connected (through a chemical linkage achieved by covalent action) with the corresponding polymer layers 200. The chemical composition and content of the polymer layers 130 on the two sides can be the same or different. The chemical composition and content of the lithium-containing layers 130 on the two sides can be the same or different.

[0445] In some embodiments, the negative electrode tab includes a negative electrode tab substrate 100 having Figure 5The structure shown includes a negative electrode substrate 100 and two polymer layers 200 respectively disposed on the surfaces of both sides of the negative electrode substrate 110; the negative electrode substrate includes a negative electrode current collector 110, two second negative electrode active material layers 120 respectively disposed on the surfaces of both sides of the negative electrode current collector 110, and two lithium-containing layers 130 respectively disposed on the surface of the two second negative electrode active material layers 120 away from the negative electrode current collector 110. The lithium-containing layers 130 on both sides of the negative electrode substrate are directly connected to the corresponding polymer layers 200 (chemical connection is achieved through covalent interaction). The chemical composition and content of the polymer layers 130 on both sides can be the same or different. The chemical composition and content of the second negative electrode active material layers 120 on both sides can be the same or different. The chemical composition and content of the lithium-containing layers 130 on both sides can be the same or different.

[0446] In some embodiments, the negative electrode plate generally includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes the aforementioned lithium-containing layer and further includes a polymer layer formed on at least one surface of the lithium-containing layer remote from the interior of the negative electrode film layer. That is, the polymer layer is located on the surface of the lithium-containing layer remote from the negative electrode current collector. The polymer layer is located on the outermost layer of the negative electrode plate. Furthermore, the polymer layer and the lithium-containing layer are chemically bonded via a covalent interaction.

[0447] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0448] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate. Non-limiting examples of metal materials may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of polymer material substrates may include one or more substrates of materials such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0449] In some embodiments, the negative electrode active material in the negative electrode active material layer may be a negative electrode active material for lithium metal batteries that is well known in the art. As an example, the negative electrode active material suitable for the present application may include one or more of lithium metal and lithium alloys. In addition to lithium, the lithium alloy may also contain one or more of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, titanium, etc. The lithium-containing layer in the present application may serve as the first negative electrode active material layer, and a second negative electrode active material layer may be provided between the lithium-containing layer and the negative electrode current collector. The composition and content of the second negative electrode active material layer may be the same as or different from the composition and content of the lithium-containing layer.

[0450] In some embodiments, the negative electrode film layer may further optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0451] In some embodiments, the negative electrode film layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0452] In some embodiments, the negative electrode active material layer may further include other auxiliary agents, such as a thickener, etc. Non-limiting examples of thickeners may include sodium carboxymethyl cellulose (CMC-Na), etc.

[0453] In a third aspect, the present application provides a secondary battery (also referred to as a lithium metal secondary battery) comprising a positive electrode sheet, a separator, and the negative electrode sheet described in the second aspect of the present application, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, and the polymer layer is disposed on a side of the negative electrode sheet proximal to the separator. Because the negative electrode sheet includes a lithium-containing layer, the secondary battery of the third aspect is also referred to as a lithium metal secondary battery.

[0454] The negative electrode plate in the lithium metal secondary battery includes a lithium metal negative electrode material distributed simultaneously in a lithium-containing layer and a polymer layer. On at least one side of the negative electrode plate, the lithium-containing layer is stably connected to a dense and uniform polymer layer by chemical bonding. The polymer layer has certain elasticity, flexibility and swelling properties, which can ensure a firm, tight and durable fit between the polymer layer and the lithium-containing layer, and between the polymer layer and the isolation membrane. It can better adapt to the large volume expansion of the negative electrode side during charging, and can serve as a protective layer at the negative electrode of the lithium metal secondary battery for a long time. This polymer layer effectively inhibits the contact reaction between the electrolyte and lithium metal, reducing electrolyte and lithium metal consumption and extending cycle life. It also utilizes the fluorinated aliphatic chains (Rf) in the lithium metal anode material to promote uniform lithium ion deposition, inhibit the formation of lithium dendrites, and mitigate volume expansion on the lithium metal anode side. Furthermore, the polymer layer's combined elasticity, flexibility, and swelling properties not only promote close adhesion between the polymer layer and the lithium-containing layer, but also contribute to excellent ionic conductivity, reducing interfacial polarization and impedance. Consequently, the presence of the polymer layer enables lithium metal secondary batteries to achieve higher energy density, power density, charge-discharge cycle stability, and superior safety.

[0455] In addition, by inhibiting the contact reaction between the electrolyte and lithium metal and reducing the consumption of the electrolyte and lithium metal, the coulombic efficiency of the battery can also be improved.

[0456] In some embodiments, the lithium metal secondary battery further includes a second electrolyte, and the components of the second electrolyte and the first electrolyte in the polymer layer may be the same or different.

[0457] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a cell electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The cell electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The active ions in the secondary battery provided in the present application can be lithium ions, but are not limited to this.

[0458] Positive electrode

[0459] In the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material layer. Further, the positive electrode active material layer includes a positive electrode active substance.

[0460] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0461] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate. In the negative electrode current collector, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate include one or more substrates of materials such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0462] In some embodiments of the present application, the secondary battery is a lithium-ion secondary battery. Lithium-ion secondary batteries utilize the intercalation and deintercalation of lithium ions in electrodes and their transport in electrolytes to achieve charge and discharge. Generally speaking, the active ions in lithium-ion secondary batteries are lithium ions, but this is not limited to this.

[0463] The positive electrode active material may be a positive electrode active material for batteries that is well known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials or substances: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials or substances, and other traditional materials or substances that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, non-limiting examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium cobalt oxide include LiCoO2; non-limiting examples of lithium nickel oxide include LiNiO2; non-limiting examples of lithium manganese oxide include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide include LiNi 0.85 Co 0.15 Al 0.05 O2. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium iron phosphate include LiFePO4 (also referred to as LFP); non-limiting examples of lithium manganese phosphate include LiMnPO4.

[0464] In some embodiments, the positive electrode active material may include but is not limited to one or more of the following materials or substances: lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, sodium oxide and potassium oxide, and a material composed of any of the foregoing substances and doping elements; further, the doping elements in any one of the positive electrode active materials independently include one or more of transition metal elements and non-transition metal elements.

[0465] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0466] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0467] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, compacting (compacting can be performed by cold pressing) and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The compacted density of the positive electrode sheet can be 3.0 to 3.6g / cm 3 , can be selected as 3.3~3.5g / cm 3 .

[0468] Battery electrolyte

[0469] The cell electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of cell electrolyte, and the type can be selected based on needs. For example, the cell electrolyte can be liquid, gel, or solid.

[0470] In some embodiments, the battery cell electrolyte uses a second electrolyte solution, which includes an electrolyte salt and a solvent (which may be referred to as a second electrolyte solution solvent).

[0471] In some embodiments, the core electrolyte (eg, the second electrolyte) and the first electrolyte in the polymer layer may have the same or different components.

[0472] When the cell electrolyte (such as the second electrolyte) in the secondary battery has the same composition as the first electrolyte in the polymer layer, the consistency of lithium ion transmission in the cell can be maintained, reducing interference from multiple factors such as electrolyte solvation and interfacial side reactions.

[0473] When the composition of the core electrolyte in the secondary battery is different from that of the first electrolyte in the polymer layer, the formation of a stable SEI can be induced directionally on the lithium-containing layer side, thereby regulating the deposition morphology of lithium ions.

[0474] In some embodiments, the electrolyte salt in the second electrolyte may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0475] In some embodiments, the solvent in the second electrolyte may include one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0476] In some embodiments, the battery cell electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0477] In some embodiments, the additives in the battery electrolyte may include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), methylene methanedisulfonate (MMDS), 1-propylene-1,3-sultone (PST), vinyl sulfite (ES), propylene sulfite (PS), vinyl sulfate (DTD), succinonitrile (SN), adiponitrile (AND), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB) and anisole.

[0478] Isolation film

[0479] In this application, unless otherwise specified, “separator membrane” and “diaphragm” have the same meaning and can be used interchangeably.

[0480] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0481] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0482] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0483] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the battery cell electrolyte.

[0484] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0485] The present application has no particular restrictions on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, Figure 6 The secondary battery 5 is a square structure as an example.

[0486] In some embodiments, reference Figure 7 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a accommodating cavity. The shell 51 has an opening connected to the accommodating cavity, and the cover plate 53 can be covered on the opening to close the accommodating cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the accommodating cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs. The secondary battery provided in the present application can be circulated under certain charging current density conditions.

[0487] In some embodiments, the charging current density of the secondary battery can be selected from any one of the following values ​​or an interval consisting of any two values: 0.1 mA / cm 2 , 0.2mA / cm 2 , 0.3mA / cm 2 , 0.4mA / cm 2 , 0.5mA / cm 2 , 0.6mA / cm 2 , 0.7mA / cm 2 , .8mA / cm 2 , 0.9mA / cm 2 , 1mA / cm 2 , 1.5mA / cm 2 , 2mA / cm 2 , 2.5mA / cm 2 , 3mA / cm 2 , 3.5mA / cm 2 , 4mA / cm 2 , 4.5mA / cm 2, 5 mA / cm 2 , 5.5 mA / cm 2 , 6 mA / cm 2 , 7 mA / cm 2 , 8 mA / cm 2 , 9 mA / cm 2 , 10 mA / cm 2 , 11 mA / cm 2 , 12 mA / cm 2 , etc.

[0488] In some embodiments, the applicable charging current density can also be selected from any one of the following ranges: 0.1 mA / cm 2 ~ 3.5 mA / cm 2 , 1 mA / cm 2 ~ 3.5 mA / cm 2 , 0.1 mA / cm 2 ~ 12 mA / cm 2 , 1 mA / cm 2 ~ 12 mA / cm 2 , 0.1 mA / cm 2 ~ 4 mA / cm 2 , 1 mA / cm 2 ~ 4 mA / cm 2 , etc.

[0489] The secondary battery provided in the present application can be cycled under the aforementioned charging current density conditions.

[0490] In some embodiments, the capacity retention rate of the secondary battery after a certain number of cycles (e.g., 50 cycles) is very high. In some embodiments, the capacity retention rate of the secondary battery after 50 cycles is higher than 80%.

[0491] In the present application, the "capacity retention rate after 50 cycles" of the secondary battery, unless otherwise specified, generally refers to the test value under the condition of 20°C to 30°C. In some embodiments, the capacity retention rate of the secondary battery after 50 cycles refers to the volume expansion rate at 25°C. The test method can be found in the "structure and performance test" section of the examples below.

[0492] The present application can also provide a battery module comprising the secondary battery of the fourth aspect of the present application.

[0493] The present application can also provide a battery pack comprising the aforementioned battery module. In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0494] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0495] In a fourth aspect, the present application provides an electrical device comprising the lithium metal secondary battery described in the third aspect of the present application.

[0496] The secondary battery can be used as a power source or energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, and energy storage systems. Examples of mobile devices include, but are not limited to, mobile phones and laptops; and examples of electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks.

[0497] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0498] Figure 8 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0499] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0500] In a fifth aspect, the present application provides an application of a monomer composition in preparing a negative electrode sheet or a lithium metal secondary battery, wherein the monomer composition comprises a first monomer represented by formula (M1) and a second monomer represented by formula (M2):

[0501]

[0502] wherein X1, X2, Y1, Y2, A1, A2, Rf and Rd are as defined in the first aspect of the present application; z is as defined in the first aspect of the present application; at least one of Y1 and Y2 is a cyano group;

[0503] The negative electrode plate includes a lithium-containing layer, and the lithium-containing layer contains lithium metal;

[0504] The first monomer and the second monomer are used to form a polymer layer bonded to the lithium metal in the negative electrode plate.

[0505] In the present application, the first monomer may also be referred to as monomer compound M1, and the second monomer may also be referred to as monomer compound M2.

[0506] The first monomer and the second monomer in the monomer composition are both cyanoacrylic acid derivatives, the cyano group therein can contact with the lithium in the outermost layer of the negative electrode substrate to form a chemical connection, and the carbon-carbon double bond therein can undergo an in-situ polymerization reaction under lithium catalysis, thereby preparing the lithium metal negative electrode material of the first aspect of the present application. At this time, a firmly connected, dense and uniform polymer layer can be formed on the surface of the lithium-containing layer of the negative electrode. The polymer layer has certain elasticity, flexibility and swelling properties, and can play the role of a protective layer for a long time.

[0507] In some embodiments, Y1 and Y2 are both cyano.

[0508] In some embodiments, the application includes the following steps: the first monomer and the second monomer are brought into contact with lithium metal in the lithium-containing layer to form the polymer layer through an in-situ polymerization reaction.

[0509] In some embodiments, the negative electrode plate is as defined in the second aspect of the present application, and the lithium metal secondary battery is as defined in the third aspect of the present application.

[0510] In a sixth aspect, the present application provides a method for preparing a negative electrode sheet, which comprises the following steps:

[0511] Providing a negative electrode substrate, wherein the outermost layer of at least one side of the negative electrode substrate is a lithium-containing layer, and the lithium-containing layer contains lithium metal; and also providing a reaction mixture containing a monomer composition and a first electrolyte;

[0512] The reaction mixture is applied to the surface of the lithium-containing layer on at least one side of the negative electrode substrate, so that the monomer composition contacts at least a catalytic amount of lithium metal, and the monomer composition undergoes an in-situ polymerization reaction to form a polymer Poly bonded to the lithium metal in the lithium-containing layer;

[0513] Wherein, the monomer composition is as defined in the fifth aspect of this application;

[0514] The first electrolyte is as defined in the second aspect of the present application.

[0515] In the presence of the first electrolyte, the cyano group in the monomer composition can contact the lithium in the outermost layer of the negative electrode substrate to form a chemical connection (further, a covalent connection), and the carbon-carbon double bond therein can undergo in situ polymerization under lithium catalysis to form the aforementioned polymer Poly, thereby preparing the lithium metal negative electrode material of the first aspect of the present application. At this time, a firmly connected, dense and uniform polymer layer can be formed on the surface of the lithium-containing layer of the negative electrode. The polymer layer has certain elasticity, flexibility and swelling properties and can play a protective layer role for a long time. Compared with the polymer coating of the physical coating method in the traditional technology, the polymer layer formed in the present application is not only stably bound to the surface of the lithium-containing layer by chemical connection, but also can reduce, avoid or effectively delay the polymer layer from falling off from the surface of the lithium-containing layer during the charge and discharge process. In addition, the polymer layer of the present application is dense and uniform, and the thickness of the polymer layer can be controlled at the nanoscale by in situ polymerization, so that the assembled battery cell can exhibit a smaller interface impedance.

[0516] In some embodiments, a lithium sheet or a lithium alloy sheet may be used as the negative electrode substrate. The lithium sheet may consist essentially of lithium, excluding unavoidable impurities. The lithium alloy sheet may consist essentially of a lithium alloy, excluding unavoidable impurities.

[0517] In some embodiments, a lithium layer or lithium alloy layer can be formed on the negative electrode current collector to prepare a negative electrode substrate. The lithium layer, excluding unavoidable impurities, consists essentially of lithium. The lithium alloy layer, excluding unavoidable impurities, consists essentially of a lithium alloy.

[0518] In the negative electrode preparation method, the monomer composition provided herein contacts at least a catalytic amount of lithium metal in the lithium-containing layer, providing chemical attachment sites for the polymer layer while effectively catalyzing the in-situ polymerization reaction of the polymerizable monomer (e.g., a cyano olefin carboxylic acid derivative monomer, further comprising a cyanoacrylic acid derivative monomer).

[0519] The mass ratio of the polymer Poly in the generated polymer layer to the first electrolyte can be regulated by adjusting the mass ratio of the monomer composition and the first electrolyte. Numerically, it can be estimated and converted based on the mass ratio of the monomer composition raw material to the first electrolyte raw material being equal to the mass ratio of the polymer Poly in the polymer layer to the first electrolyte. In the method for preparing the negative electrode sheet, the mass ratio of the polymer Poly raw material to the first electrolyte raw material can refer to any appropriate ratio in the previous or subsequent text of this application, including but not limited to the definition in the second aspect.

[0520] In some embodiments, the step of coating the reaction mixture on the surface of the lithium-containing layer on at least one side of the negative electrode substrate may include coating, spraying, spin coating, and vapor deposition. The coating thickness may be controlled based on the desired thickness of the polymer layer.

[0521] In some embodiments, the reaction temperature of the in situ polymerization is selected from 30°C to 100°C; alternatively, the reaction temperature of the in situ polymerization is selected from 30°C to 60°C; further alternatively, the reaction temperature of the in situ polymerization is selected from 40°C to 80°C. The reaction temperature of the in situ polymerization can also be any one of the following temperatures or a range consisting of any two of the following temperatures: 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.

[0522] In some embodiments, the reaction time of the in situ polymerization is selected from 0.1h to 24h; alternatively, the reaction time of the in situ polymerization is selected from 0.1h to 12h; further alternatively, the reaction time of the in situ polymerization is selected from 0.1h to 6h. The reaction time of the in situ polymerization can be any of the following time lengths or an interval consisting of any two of the following time lengths: 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, 0.6h, 0.8h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 11h, 12h, 14h, 15h, 16h, 18h, 20h, 21h, 22h, 24h, etc.

[0523] In some embodiments, the polymer layer formed by the in situ polymerization reaction is as defined in the second aspect of the present application.

[0524] In some embodiments, the polymer layer described in the second aspect of the present application is formed on the surface of the negative electrode substrate.

[0525] In some embodiments, the negative electrode plate substrate is a pure lithium sheet or a lithium alloy. The definition of lithium alloy applicable to this application can be found in the above text. In some embodiments, the mass proportion of the lithium element in the lithium alloy is ≥50%. The mass proportion of the lithium element in the lithium alloy can also be independently any of the following percentages, or independently greater than or equal to any of the following percentages and less than 100%, or independently selected from the interval consisting of any two of the following percentages: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, 95%, 96%, 97%, 98%, 99%.

[0526] When the negative electrode plate substrate is a pure lithium plate or a lithium alloy, the battery negative electrode plate may further include a negative electrode current collector to facilitate assembly of the tabs, or a pure lithium plate covered with a polymer layer may be used as the negative electrode plate.

[0527] In some embodiments, the negative electrode plate is as defined in the second aspect of the present application.

[0528] In a seventh aspect, the present application provides a method for preparing the lithium metal secondary battery described in the third aspect of the present application, the method comprising the following steps: injecting a cell electrolyte into a battery casing containing the aforementioned positive electrode sheet, negative electrode sheet, and separator. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and the polymer layer in the negative electrode sheet is disposed on the side of the negative electrode sheet closest to the separator.

[0529] Some embodiments of the present application are described below.

[0530] The parameter characterizations mentioned above, including but not limited to elastic modulus, elastic deformation range, polymer swelling rate, ionic conductivity, flexibility test, negative electrode sheet expansion rate, battery cycle performance, etc., can be achieved by adopting or referring to the test methods below, including but not limited to the "Structure and Performance Test" section.

[0531] The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. Where the technology or conditions are not indicated in the embodiments, they are carried out according to the description above, or according to the technology or conditions described in the document in this area or according to the product specification. Reagents used or instruments that are not indicated by the manufacturer are conventional products that can be obtained commercially, or can be synthesized in a conventional manner by commercially available products.

[0532] In the following embodiments, room temperature refers to 20°C to 30°C, and further, may be 25°C.

[0533] In the following specific examples, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument testing accuracy or operational accuracy are allowed.

[0534] In the following examples, unless otherwise specified, the monomer-electrolyte mixture is applied by coating. When the polymer layer thickness is expressed as an approximate number, the deviation may be within ±10%, for example, 0.1 ± 0.01 μm, 1 ± 0.05 μm.

[0535] Preparation of monomer compound M1 (first monomer) and monomer compound M2 (second monomer)

[0536] The monomer compounds used in the following examples can be obtained commercially (such as 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate, CH2=C(-CN)-C(=O)-OH), or can be prepared by the following method. For the preparation of intermediates and synthetic products, those skilled in the art can use (but not limited to) Fourier transform infrared spectroscopy (FT-IR) testing, 1 Structural characterization can be performed using methods such as H NMR testing, gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS) to confirm whether the structure of the synthesized product conforms to the structural design, which is achievable for those skilled in the art.

[0537] 1. When X1 or X2 is H

[0538] When X1 in the monomer compound M1 is H, it corresponds to the compound M11 in the following formula, with a structure of CH2=C(-CN)-C(=O)-A1-Rf, which is a cyanoacrylic acid derivative and can be prepared by a condensation reaction between compound C10 (2-cyanoacrylic acid) and compound C21 (Rf-A1H). The reaction generates a linker C(=O)-A1, wherein, when A1 is O, an ester bond (C(=O)-O) is generated by a condensation reaction between a carboxyl group and a hydroxyl group; and when A1 is NH, an amide bond (C(=O)-NH) is generated by a condensation reaction between a carboxyl group and -NH2.

[0539] When X2 in the monomer compound M2 is H, the corresponding compound M21 in the following formula has the structure CH2=C(-CN)-C(=O)-A2-(CH2CH2O) z -pRd can be synthesized by reacting compound C10 (2-cyanoacrylic acid) with compound C22 (H-A2-(CH2CH2O) z -pRd) to form a linker C(=O)-A2, wherein when A2 is O, an ester bond (C(=O)-O) is generated by a condensation reaction between the carboxyl group and the hydroxyl group; and when A2 is NH, an amide bond (C(=O)-NH) is generated by a condensation reaction between the carboxyl group and -NH2.

[0540] Wherein, z is a positive integer; when z≥2, the monomer compound M2 is an ether derivative of cyanoacrylic acid. "Ether derivative" refers to a compound containing an ether bond (-O-).

[0541] Wherein, pRd is Rd or a protected form of Rd as defined above. When reacting Compound C10 with Compound C22, if Rd does not undergo an irreversible side reaction, the reaction can be carried out without protection, meaning that pRd is Rd; for example, if Rd is an alkyl group. When reacting Compound C10 with Compound C22, if Rd is likely to undergo an irreversible side reaction, the reaction can be carried out with protection, meaning that pRd is a protected form of Rd. An "irreversible side reaction" refers to an irreversible side reaction that is difficult to reconvert to the Rd group using conventional organic chemical synthesis methods. In contrast, if, during the reaction of Compound C10 with Compound C22, the new group Rd' formed by the conversion of Rd can be reconverted to Rd using common chemical modification and demodification methods such as protection, deprotection, complexation, decomplexation, salification, desalination, ionization, and deionization, then this is considered a reversible change and does not fall under the category of an "irreversible side reaction."

[0542] The reaction conditions for preparing monomers M11 and M21 can be combined with the raw material structures and reference to existing methods in the field of organic chemistry, and can be easily implemented by those skilled in the art.

[0543]

[0544] 2. When X1 or X2 is not H

[0545] When X1 or X2 is not H, X1-CH=C(-CN)-C(=O)-OH (denoted as compound C11) or X2-CH=C(-CN)-C(=O)-OH (denoted as compound C12) modified with X1 or X2 can be prepared first, and then reacted with the corresponding compound C21 or compound C22 with reference to the preparation method when X1 or X2 is H to prepare the corresponding monomer compound M12 or M22.

[0546] The structural formula of M12 is X1-CH=C(-CN)-C(=O)-A1-Rf, wherein the definitions of X1, A1 and Rf are the same as above.

[0547] The structural formula of M22 is X2-CH=C(-CN)-C(=O)-A2-(CH2CH2O) z -pRd, wherein z, X2, A2 and pRd are defined as above.

[0548]

[0549] Taking compound C11 and X1 as -N(CH3)2 as an example, reference can be made to the synthesis method of the literature "Bredereck, Hellmut, et al. Chemische Berichte, 1964, 97(12), 3397-3406", using acetal compound C31 and cyanoacrylate compound C4 (such as ethyl 2-cyanoacrylate) to prepare X1-modified cyanoacrylate derivatives (compound C51, such as 1-X1-2-cyanoacrylate), which are hydrolyzed to form X1-modified cyanoacrylic acid (compound C11).

[0550] Taking compound C12 and X2 being -N(CH3)2 as an example, reference can be made to the method of "Bredereck, Hellmut, et al. Chemische Berichte, 1964, 97(12), 3397-3406", using acetal compound C32 and cyanoacrylate compound C4 (such as ethyl 2-cyanoacrylate) to prepare X2-modified cyanoacrylate derivatives (compound C52, such as 1-X2-2-cyanoethyl acrylate), which are hydrolyzed to form X2-modified cyanoacrylic acid (compound C12).

[0551]

[0552] According to nuclear magnetic resonance spectroscopy ( 1 Whether the target compound is formed can be determined based on at least one of (but not limited to) H NMR and gas chromatography-mass spectrometry (GC-MS) results, and whether the polymer Poly is formed can be determined based on at least one of molecular weight and viscosity test results.

[0553] Example 1.

[0554] The monomer compound M1 is 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate, the monomer compound M2 is pentaethylene glycol monomethyl ether cyanoacrylate, the first electrolyte lithium salt is lithium bis(fluorosulfonyl)imide, the first electrolyte solvent is ethylene glycol dimethyl ether, and the negative electrode plate matrix is ​​a pure lithium sheet.

[0555] (1) Preparation of polymer layer reaction mixture

[0556] At 25°C, 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate, pentaethylene glycol monomethyl ether cyanoacrylate, lithium bis(fluorosulfonyl)imide (LiFSI), and ethylene glycol dimethyl ether (DME) were stirred uniformly at room temperature to obtain a monomer-electrolyte mixture. The raw material amounts are shown in Tables 1-3. This electrolyte is referred to as the first electrolyte. The LiFSI concentration in the first electrolyte was 1.0 mol / L.

[0557] (2) Preparation of negative electrode sheet

[0558] The resulting monomer-electrolyte mixture was coated on one side of a lithium sheet and allowed to react at 30°C for 3 hours to produce a lithium sheet with a transparent, dense polymer layer on one side. The operating parameters are shown in Tables 1-3. The sheet was cut into 16mm diameter discs to serve as the negative electrode.

[0559] (3) Preparation of positive electrode sheet:

[0560] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 98:1:1, and solvent N-methylpyrrolidone (NMP) was added and stirred until the system became uniform to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on one side of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying, and then cut into discs with a diameter of Φ14 mm as positive electrode sheets. The positive electrode surface capacity was 3 mAh / cm 2 .

[0561] (4) Preparation of electrolyte:

[0562] Lithium bis(fluorosulfonyl)imide (LiFSI) was slowly added to ethylene glycol dimethyl ether (DME) to prepare an electrolyte with a LiFSI concentration of 1 mol / L.

[0563] (5) Isolation film: Use polypropylene film.

[0564] (6) Preparation of lithium metal secondary batteries:

[0565] Place the above-mentioned positive electrode sheet, separator, and negative electrode sheet in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, inject the electrolyte prepared in (4) above, and assemble into a button battery.

[0566] Example 2-23 uses a method substantially the same as that of Example 1, except that step (1) is different. Please refer to the parameter differences in Tables 1-3.

[0567] Comparative Examples 1-9 adopt a method substantially the same as Example 1, except that step (1) and / or step (2) are different. The parameter differences can be seen in Tables 1-3.

[0568] In Examples 2-23 and Comparative Examples 1-9, the types and molar ratios m / n of the monomer compounds M1 and M2 in the monomer composition, the fluorine substitution rate in Rf in the monomer compound M1, the type, concentration and amount of the lithium salt in the first electrolyte (corresponding to the first electrolyte lithium salt), the type and amount of the solvent in the first electrolyte (corresponding to the first electrolyte solvent), the amount of the monomer compound M1 and the monomer compound M2, the temperature and time of the in-situ polymerization reaction, the thickness of the polymer layer, the molecular weight, PDI and glass transition temperature (Tg) of the polymer Poly, the mass proportion of the fluorine element in the polymer Poly, and the mass proportion of the first electrolyte in the polymer layer can be found in Table 1-3. The amount of the first electrolyte lithium salt and the first electrolyte solvent can be converted based on the total mass of the two and the lithium salt concentration in the first electrolyte. The amounts of monomer compound M1 and monomer compound M2 can be calculated based on their total mass and m / n conversion, assuming that the molar ratio of monomer compound M1 to monomer compound M2 is numerically equal to the ratio of the degrees of polymerization of the two repeating units in the polymer Poly. The mass ratio of the polymer Poly in the polymer layer to the first electrolyte can be estimated based on the parameters in Tables 1-3, assuming that the mass ratio of the polymer Poly in the polymer layer to the first electrolyte is numerically equal to the ratio of the total mass of the monomer composition raw materials to the total mass of the first electrolyte raw materials.

[0569] Compared with Example 1, in Examples 2-6, at least the monomer compound M1 and the monomer compound M2 in the monomer composition were adjusted.

[0570] Compared with Example 1, at least the m / n value is adjusted in Examples 7-10.

[0571] Compared with Example 1, Examples 11-14 at least adjust the content of the first electrolyte in the monomer-electrolyte mixture.

[0572] Compared with Example 1, Examples 15-18 at least adjusted the lithium salt concentration of the first electrolyte in the monomer-electrolyte mixture.

[0573] Compared with Example 1, at least the thickness of the polymer layer is adjusted in Examples 19-22.

[0574] Compared with Example 1, Example 23 changes the negative electrode plate substrate from a pure lithium plate to a lithium-magnesium alloy, and the mass ratio of lithium to magnesium is 1:1.

[0575] Comparative Example 1: A preparation method substantially identical to that of Example 1 was employed, with the exception of the negative electrode sheet. This comparative example employed a pure lithium sheet as the negative electrode sheet, i.e., without a polymer layer. All other preparation parameters were the same as those of Example 1.

[0576] Comparative Example 2. Physical application of polymer coating.

[0577] The preparation method is substantially the same as that of Example 1, except that the connection method between the polymer layer and the lithium-containing layer is different.

[0578] In this comparative example, the polymer solution was sprayed onto the surface of the pure lithium sheet and dried to obtain a polymer coating with a thickness of about 0.1 micron, as shown in Table 1-3. A tetrahydrofuran (THF) solution containing 6g of polymer and 4.3g of the first electrolyte (the first electrolyte lithium salt and the first electrolyte solvent, the concentration of the first electrolyte lithium salt in the first electrolyte is 1.0 mol / L) were mixed to prepare a polymer solution, wherein the polymer is a copolymer of 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate and pentaethylene glycol monomethyl ether cyanoacrylate, with a weight average molecular weight of 70kDa (i.e., 70,000 Daltons). The polymer used in this example adopts the monomer composition in Example 1. The two monomer raw materials were polymerized in the same amount ratio as in Example 1. The molecular weight of the product was controlled by adjusting the reaction temperature and time. The obtained polymer was prepared into a polymer solution, which was then sprayed in this example.

[0579] Comparative Example 3.

[0580] The preparation method is basically the same as that of Comparative Example 2, except that the coating amount of the polymer solution is different, and the thickness of the polymer layer formed is different. The thickness of the polymer layer in this example is about 1 micron. Please refer to Tables 1-3. The polymer is a copolymer of 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate and pentaethylene glycol monomethyl ether cyanoacrylate, with a weight average molecular weight of 68 kDa (i.e. 68,000 Daltons). The polymer used in this example adopts the monomer composition in Example 1. The two monomer raw materials were polymerized in the same amount ratio as in Example 1. The molecular weight of the product was controlled by adjusting the reaction temperature and time. The obtained polymer was prepared into a polymer solution, which was then sprayed in this example.

[0581] Comparative Example 4.

[0582] The preparation method is basically the same as that of Example 1, except that no cyano group is provided in monomer compound M1 and monomer compound M2. The remaining preparation parameters are the same as those in Example 1.

[0583] Comparative Example 5.

[0584] The preparation method is basically the same as that of Example 1, except that a single monomer compound M1 is used. The monomer compound containing EO block was omitted. The remaining preparation parameters were the same as those in Example 1.

[0585] Comparative Example 6.

[0586] The preparation method is basically the same as that of Example 1, except that a single monomer compound M2 is used. The monomer compound containing the fluorinated aliphatic chain Rf was omitted. The remaining preparation parameters were the same as those in Example 1.

[0587] Comparative Example 7.

[0588] The preparation method is basically the same as that in Example 1, except that a single monomer is used. The monomer does not include the monomer compound M1 containing Rf, nor the monomer compound M2 containing EO block. The remaining preparation parameters are the same as those in Example 1.

[0589] Comparative Example 8.

[0590] The preparation method is basically the same as that of Example 1, except that the Rf and EO blocks are provided in the same monomer compound and the single monomer is used. The remaining preparation parameters are the same as those in Example 1.

[0591] Comparative Example 9.

[0592] The preparation method is basically the same as that in Example 1, except that the monomer compound M2 is replaced by The EO block is thereby replaced by a polyoxypropylene PPO segment, and the remaining parameters refer to Example 1.

[0593] Table 1.

[0594]

[0595]

[0596] In Table 1, in each embodiment and related comparative example, the raw material molar ratio of the monomer compound M1 to the monomer compound M2 is numerically equal to the polymerization degree ratio m / n of the two repeating units in the target polymer Poly.

[0597] Table 2.

[0598]

[0599]

[0600]

[0601] In each example, the mass ratio of the polymer Poly in the polymer layer to the first electrolyte can be estimated by converting using the following formula: m10 / m20, that is, the sum of the masses of the monomer compound M1 and the monomer compound M2 in Table 2 (m10) divided by the sum of the mass of the lithium salt and the mass of the solvent in the first electrolyte (m20); wherein, the respective amounts of the monomer compound M1 and the monomer compound M2 can be obtained by conversion according to m / n, assuming that the molar ratio of the monomer compound M1 and the monomer compound M2 is numerically equal to the ratio of the degree of polymerization of the two repeating units in the polymer Poly.

[0602] In each example, the mass proportion of the first electrolyte in the polymer layer can be estimated by the following formula: m20 / (m20+m10)×100%, see Table 3.

[0603] Table 3.

[0604]

[0605]

[0606] Test sample preparation

[0607] 1. Preparation of polymer layer membrane

[0608] The monomer compound M1 is 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate. The monomer compound M2 is pentaethylene glycol monomethyl ether cyanoacrylate. The lithium salt and solvent in the first electrolyte are lithium bis(fluorosulfonyl)imide (LiFSI) and ethylene glycol dimethyl ether (DME), respectively.

[0609] (1) At 25° C., 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate and pentaethylene glycol monomethyl ether cyanoacrylate were mixed at a molar ratio of 2:1 (equal to m / n), lithium bis(fluorosulfonyl)imide (LiFSI) and ethylene glycol dimethyl ether (DME) were mixed at a lithium salt concentration of 1.0 mol / L, and the monomer compound M1, the monomer compound M2, and the lithium salt and solvent of the first electrolyte were stirred at room temperature to obtain a uniform solution.

[0610] (2) Add 0.1 g of lithium powder to the homogeneous solution obtained in step (1), stir rapidly until uniform, and then apply the mixture to a glass plate. Allow the mixture to react at 30°C for 3 h to obtain a transparent polymer film with a thickness of 15 μm. Refer to the in-situ polymerization conditions of Example 1.

[0611] Structure and performance testing

[0612] 1. Characterization of polymer components in the polymer layer

[0613] The lithium sheet containing the polymer layer is immersed in isopropanol. The lithium sheet will be corroded and consumed. The generated lithium isopropoxide can be dissolved in isopropanol. The polymer is insoluble in isopropanol and precipitates. After centrifugal drying, a solid sample of the polymer can be obtained.

[0614] 1.1. Fourier transform infrared spectroscopy (FT-IR) test: ATR mode, 4cm -1 Resolution, 32 scans, wave number range 4000cm -1 ~400cm -1 .

[0615] 1.2. 1 H NMR nuclear magnetic test: 1 The H resonance frequency was 400 MHz, the solvent was deuterated dimethyl sulfoxide (DMSO-d6), and tetramethylsilane (TMS) was used as the internal standard.

[0616] 1.3. Molecular weight test: The polymer sample was dissolved in NMP and the molecular weight was tested by gel permeation chromatography (GPC) to obtain the weight average molecular weight, number average molecular weight and molecular weight polydispersity index (PDI).

[0617] 1.4. Polymer layer thickness test: The polymer layer thickness was measured using a laser thickness gauge.

[0618] 2. Fluorine content

[0619] The content of fluorine in the polymer layer can be detected by X-ray photoelectron spectroscopy (XPS).

[0620] 3. Swelling parameters

[0621] The swelling parameters of the polymer layer were tested using the following method:

[0622] The test temperature is 25°C. The lithium metal sheet containing the polymer layer is cut into 30mm×30mm square samples, with three parallel samples in each group, and the mass of each sample is weighed W1. Then, the sample is immersed in a 1mol / L LiFSI DME electrolyte for 2 hours for swelling. After swelling, the sample is gently wiped with filter paper to remove the residual electrolyte on the surface, and then the mass of the swollen sample is weighed W2. The swelling rate of the polymer layer is the percentage of the mass increase of the swollen sample to the original sample mass = (W2-W1) / W1×100%.

[0623] 4. Ionic conductivity

[0624] The test temperature was 25°C. The polymer membrane was punched into a Φ16mm diameter disc. The disc was immersed in electrolyte for 1 hour, removed, and the electrolyte on the membrane surface was wiped with filter paper. The ionic conductivity σ of the polymer membrane after swelling in the electrolyte was calculated using the formula σ = d / RA, where d is the membrane thickness, measured with a micrometer, A is the membrane area, and R is the membrane impedance. The impedance of the symmetrical cell was measured using an electrochemical workstation at a test frequency of 10 -6 ~10 -1 Hz, the voltage amplitude is 5mV; the intersection of the Nyquist graph obtained in the test and the horizontal axis is the impedance R of the polymer layer.

[0625] 5. Elastic modulus and elastic deformation

[0626] Elastic Modulus: Tested at 25°C. Cut the polymer film into strips with a length L0 of 150 mm and a width of 20 mm. Measure the elastic modulus of the polymer film using a universal testing machine at a stretching distance of 100 mm and a stretching speed of 50 mm / min. The maximum tensile force of the polymer film is the elastic modulus.

[0627] Elastic deformation: The test temperature is 25° C. When a polymer film with an initial length of L0 is stretched, the length at the time of film rupture is L, and the elastic deformation of the polymer film can be calculated as (L-L0) / L0×100%.

[0628] 6. Polymer layer bonding performance test (peeling degree)

[0629] By controlling the reaction time, the thickness of the polymer layer on the lithium metal surface is controlled to be around 5μm. A 50×100 mm area is used as a peeling test sample. A sharp blade (with a sharp angle of 15° to 30°) is used to draw 10×10 1mm×1mm small grids on the surface of the protective layer sample. Each line should be deep enough to reach the bottom layer of the protective layer. Use a brush to clean the debris in the test area. Use an adhesive force of 350g / cm 2 ~400g / cm 2 Use adhesive tape (3M No. 600 tape or equivalent) to firmly adhere to the small grid being tested, and rub the tape vigorously with an eraser to increase the contact area and strength between the tape and the tested area. Grab one end of the tape and quickly tear it off vertically (90°). Perform the same test twice at the same location. Finally, use a magnifying glass to observe the condition of the grid area. If there is no peeling or it occurs within the protective layer, it is qualified. However, if the peeling occurs between the metal and polymer layers and the area is greater than 65%, it is rated as 0B; if the area is 35%-65%, it is rated as 1B; if the area is 15%-35%, it is rated as 2B; if the area is 5%-15%, it is rated as 3B; if the area is less than or equal to 5%, it is rated as 4B; if the cut edge is completely smooth and there is no peeling at the grid edge, it is rated as 5B.

[0630] 7. Flexibility of polymer materials

[0631] The glass transition temperature (Tg) of the polymer material was characterized by differential scanning calorimetry (DSC). The lower the Tg, the better the molecular weight flexibility. The DSC test temperature range was 35-800°C, the heating rate was 5°C / min, and the atmosphere was argon.

[0632] 8. Negative electrode performance test

[0633] Negative electrode volume expansion rate: The test temperature is 25°C. The thickness of the fresh lithium sheet is d1. After the battery is cycled 50 times to a fully discharged state, the battery is disassembled and the thickness of the lithium sheet is measured using an optical microscope to be d2. The negative electrode expansion rate is (d2-d1) / d1×100%.

[0634] 9. Battery performance test

[0635] (1) Cycling performance test: The test temperature is 25°C. The lithium metal battery is first charged to 4.25V at a constant current density and then discharged to 3.0V to obtain the first cycle discharge capacity (Cd1). This charge and discharge cycle is repeated for 50 cycles. The discharge capacity of the lithium metal battery after n cycles is recorded as Cdn. Capacity retention rate = discharge capacity after n cycles (Cdn) / first cycle discharge capacity (Cd1) × 100%. The charging current density can be referred to in Table 4.

[0636] (2) Observation of the lithium negative electrode surface: After the battery was fully discharged at the 50th cycle, the uniformity of lithium deposition / dissolution and the flatness of the lithium negative electrode surface were observed under an optical microscope.

[0637] Test results

[0638] The molecular weight, PDI and Tg of the polymer Poly in the polymer layer, the mass proportion of the fluorine element in the polymer Poly, the mass proportion of the first electrolyte in the polymer layer, the thickness of the polymer layer, the swelling rate of the polymer layer, the ionic conductivity, the elastic modulus and the elastic deformation, as well as the test analysis results of the capacity retention rate, lithium dendrites, negative electrode volume expansion rate and peeling degree test of the lithium metal secondary battery prepared using the negative electrode sheet containing the polymer layer of the present application after 50 cycles can be seen in Table 2-4.

[0639] Table 4.

[0640]

[0641]

[0642] According to experimental test results, by adjusting parameters such as the fluorine content of the protective layer film, the proportion of EO repeating units, the length of the EO repeating units, the lithium salt concentration in the first electrolyte, the first electrolyte content in the polymer layer and the thickness of the polymer layer, the polymer layer can obtain good ionic conductivity and good mechanical strength, which is beneficial for the application of the protective layer in lithium metal batteries that are charged and discharged at high current density.

[0643] Examples 1 to 23 use the negative electrode sheets provided by the present application, which include a lithium-containing layer and a polymer layer, and a chemical bond is formed between the two. The polymer layers formed in Examples 1 to 23 have appropriate swelling rate, elastic modulus, elastic deformation and ionic conductivity, and can be used in lithium metal batteries that perform charge and discharge cycles at a high current density. The lithium metal secondary batteries prepared in Examples 1 to 23 have improved cycle performance relative to Comparative Example 1 without a polymer layer, and the lithium dendrite phenomenon is suppressed. Among them, relative to Comparative Example 1, the volume expansion of the negative electrode sheets of Examples 1-9, 11-12, 15-16, 19-20, and 23 is significantly suppressed, and the lithium metal secondary batteries have significantly improved cycle performance, the cycle capacity retention rate is significantly improved, and there are only a small amount or no lithium dendrites, and the lithium dendrites are significantly suppressed. It should be noted that the lithium dendrite phenomenon in Examples 10, 13-14, 17-18, and 21-22 also has a certain degree of improvement in statistical significance.

[0644] Comparative Examples 2 and 3 both use physical coating to coat the polymer layer on the lithium sheet. The thickness of the polymer layer is about 0.1 micron and 1 micron, respectively. The results show that compared with Example 1 (polymer layer thickness of about 0.1 micron), the bonding strength of the polymer layer of Comparative Examples 2 and 3 is significantly reduced, and the volume expansion of the negative electrode sheet increases sharply, the cycle capacity retention rate decreases significantly, the cycle performance deteriorates significantly, and serious lithium dendrites occur. It can be seen that the embodiments of the present application can achieve a firm bond to the lithium-containing layer under the condition of a thinner polymer layer thickness, and significantly improve the cycle performance of the battery and greatly improve the cycle capacity retention rate. Comparative Example 3 increases the thickness of the physical coating polymer layer to 1 micron. Although the volume expansion of the negative electrode sheet is alleviated relative to Comparative Example 1, it leads to a significant decrease in the ionic conductivity of Comparative Example 3.

[0645] Compared with the polymerized monomers M1 and M2 in Example 1, the polymerized monomers in Comparative Example 4 do not contain a cyano group, resulting in the polymer layer formed by in situ polymerization being only physically attached to the lithium-containing layer without forming a chemical bond, resulting in a significant deterioration in the bonding strength. This also leads to a sharp increase in the volume expansion of the negative electrode sheet, a significant deterioration in the cycle performance, and the occurrence of severe lithium dendrites.

[0646] The polymerization monomers in Comparative Example 5 do not contain the EO block, i.e., the polymerization monomer M2 is omitted, which affects the adjustment of the flexibility and elasticity of the polymer layer, resulting in an increase in the volume expansion of the negative electrode sheet, a decrease in the cycle capacity retention rate, and deterioration of the cycle performance.

[0647] The polymerization monomers in Comparative Example 6 do not contain the fluorinated aliphatic chain Rf chain, i.e., the polymerization monomer M1 is omitted, which affects the regulation of the lithium ion deposition morphology, resulting in a serious lithium dendrite phenomenon, a dramatic increase in the volume expansion of the negative electrode sheet, a significant decrease in the cycle capacity retention rate, and a significant deterioration of the cycle performance.

[0648] The polymerization monomers in Comparative Example 7 do not contain the fluorinated aliphatic chain and the EO block, which affects the regulation of the lithium ion deposition morphology and the flexibility and elasticity of the polymer layer, resulting in a dramatic increase in the volume expansion of the negative electrode sheet, a significant decrease in the cycle capacity retention rate, a significant deterioration of the cycle performance, and a serious lithium dendrite phenomenon. In addition, the ionic conductivity of the polymer layer in Comparative Example 7 also decreases.

[0649] In Comparative Example 8, the Rf chain and the EO block are arranged in the same monomer molecule relative to the polymerization monomers M1 and M2 in Example 1, resulting in an increase of nearly 1 times in the volume expansion of the negative electrode sheet, a certain degree of decrease in the cycle capacity retention rate, and a certain degree of deterioration of the cycle performance. It may be due to the increase in the steric hindrance of the Rf chain and the EO block in the side chain contacting the lithium-containing layer, which affects the combination with the lithium-containing layer.

[0650] In Comparative Example 9, the EO block increases the side group, reduces the flexibility, and changes the coordination relationship with the first side chain (containing Rf), resulting in a small amount of lithium dendrite, a significant increase in the volume expansion of the negative electrode sheet, and a certain degree of decrease in the cycle capacity retention rate. In addition, the ionic conductivity of the polymer layer in Comparative Example 9 also decreases to a certain extent.

[0651] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the present disclosure.

[0652] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present application are included in the technical scope of the present application. The above-described embodiments only express several embodiments of the present application, and the description is relatively detailed, but it should not be understood as a limitation on the scope of the patent. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, other ways constructed by combining part of the elements of the embodiments are also included in the scope of the present application. It should be noted that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A lithium metal negative electrode material, characterized in that The invention relates to a polymer Poly containing lithium metal and a lithium metal bonded to the lithium metal containing lithium metal, wherein the polymer Poly has a linear carbon chain and a first side chain and a second side chain grafted to the side group of the linear carbon chain, wherein the first side chain contains a fluorinated aliphatic chain Rf, and the second side chain contains an EO block, wherein the structure of the EO block is *-(CH2CH2O) z -, z is a positive integer, * represents the connection site pointing to the linear carbon chain; In the structure of the polymer Poly, the structure of any one Rf is independently represented by formula (III-1), formula (III-2) or formula (III-3): 、 、 ； in, In formula (III-1), m3 is an integer selected from 2 to 10; R 31 、R 32 and R 3 Each occurrence is independently H or F; the structure represented by formula (III-1) contains at least 4 F atoms; In formula (III-2), m 4a and m 4b Each independently represents an integer selected from 1 to 9; R 41a 、R 42a 、R 4a 、R 41b 、R 42b and R 4b Each occurrence is independently H or F; the structure represented by formula (III-2) contains at least 4 F atoms; In formula (III-3), m5 is an integer selected from 2 to 10; R 51 and R 52 Each occurrence is independently H or F; the structure represented by formula (III-3) contains at least 4 F atoms.

2. The lithium metal negative electrode material according to claim 1, characterized in that In the structure of the polymer Poly, the number of the first side chains is m, and the number of the second side chains is n; wherein m and n are each independently an integer greater than or equal to 8.

3. The lithium metal negative electrode material according to claim 2, characterized in that m and n are each independently an integer selected from 8 to 600.

4. The lithium metal negative electrode material according to claim 2, characterized in that The polymer Poly satisfies one or more of the following characteristics: The ratio of m to n satisfies 0.5≤m / n≤8; m is an integer selected from 50 to 250; n is an integer selected from 25 to 200.

5. The lithium metal negative electrode material according to claim 4, characterized in that The polymer Poly satisfies one or more of the following characteristics: The ratio of m to n satisfies 1≤m / n≤5; m is an integer selected from 50 to 200; n is an integer selected from 40 to 150.

6. The lithium metal negative electrode material according to claim 4, characterized in that The ratio of m to n satisfies 1≤m / n≤3.

7. The lithium metal negative electrode material according to claim 1, characterized in that z is an integer selected from 2 to 10.

8. The lithium metal negative electrode material according to claim 1, characterized in that z is an integer selected from 3 to 7.

9. The lithium metal negative electrode material according to claim 1, characterized in that The polymer Poly comprises repeating units of the structure shown in formula (U1) and repeating units of the structure shown in formula (U2): ； in, X1 and X2 are each independently H or an electron-withdrawing group; Y1 and Y2 are each independently a cyano group or a linking group formed by a cyano group bonded to the lithium metal in the lithium-containing metal; A1 and A2 are each independently O, S or NR 11 ; Among them, R 11 H or C 1-3 alkyl; Rd is a hydrocarbon group or a hydrocarbon group substituted by Q1, wherein Q1 is selected from the following substituents: cyano, -C(=O)NH2, -OC(=O)NHR 6 and -S(=O)2F, R 6 H or C 1-6 alkyl.

10. The lithium metal negative electrode material according to claim 9, characterized in that At least one of Y1 and Y2 is a linking group formed by a cyano group bonded to the lithium metal in the lithium-containing metal.

11. The lithium metal negative electrode material according to claim 9, characterized in that In the structure of the polymer Poly, X1 and X2 each appear and are independently H or cyano, nitro or -NR 21 R 22 ; Among them, R 21 and R 22 Each independently is H or C 1-3 alkyl.

12. The lithium metal negative electrode material according to claim 11, characterized in that R 21 and R 22 are each independently H or methyl.

13. The lithium metal negative electrode material according to claim 11, characterized in that R 21 and R 22 All are methyl.

14. The lithium metal negative electrode material according to claim 9, characterized in that In the structure of the polymer Poly, each occurrence of A1 and A2 is independently O, S or NH.

15. The lithium metal negative electrode material according to claim 9, characterized in that Each occurrence of A1 and A2 is independently O or NH.

16. The lithium metal negative electrode material according to claim 9, characterized in that Rd is C 1-4 Hydrocarbon group.

17. The lithium metal negative electrode material according to claim 9, characterized in that Rd is C 1-4 alkyl.

18. The lithium metal negative electrode material according to claim 9, characterized in that Rd is C 1-3 alkyl.

19. The lithium metal negative electrode material according to claim 9, characterized in that Rd is methyl.

20. The lithium metal negative electrode material according to any one of claims 9 to 19, characterized in that The structure of the polymer Poly comprises m repeating units represented by formula (U1) and n repeating units represented by formula (U2); m and n are defined as in any one of claims 2 to 6.

21. The lithium metal negative electrode material according to claim 20, characterized in that m repeating units represented by formula (U1) and n repeating units represented by formula (U2) are arranged linearly.

22. The lithium metal negative electrode material according to claim 20, characterized in that The polymer Poly has a general structure as shown in formula (P1): 。 23. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The polymer Poly satisfies one or more of the following characteristics: The fluorine substitution rate in any Rf is independently ≥50%; The number of fluorine atoms in any Rf is independently ≥ 4; The mass proportion of fluorine element in the polymer Poly is 15% to 44%.

24. The lithium metal negative electrode material according to claim 23, characterized in that The polymer Poly satisfies one or more of the following characteristics: The fluorine substitution rate in any Rf is independently ≥55%; The number of fluorine atoms in any Rf is independently ≥5; The mass proportion of fluorine element in the polymer Poly is 15% to 41%.

25. The lithium metal negative electrode material according to claim 23, characterized in that The polymer Poly satisfies one or more of the following characteristics: The number of fluorine atoms in any Rf is independently 5 to 15; The mass proportion of fluorine element in the polymer Poly is 20%~41%.

26. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The polymer Poly satisfies one or more of the following characteristics: Each Rf independently contains 2 to 10 main chain carbon atoms; The number of carbon atoms in any one Rf is independently an integer selected from 2 to 10.

27. The lithium metal negative electrode material according to claim 26, characterized in that The polymer Poly satisfies one or more of the following characteristics: Each Rf independently contains 2 to 8 main chain carbon atoms; The number of carbon atoms in any one Rf is independently an integer selected from 2 to 8.

28. The lithium metal negative electrode material according to claim 26, characterized in that The polymer Poly satisfies one or more of the following characteristics: Each Rf independently contains 3 to 8 main chain carbon atoms; The number of carbon atoms in any one Rf is independently an integer selected from 3 to 8.

29. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that In the structure of the polymer Poly, one, more or all of the Rf groups independently contain one or more heteroatoms selected from the group consisting of iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus.

30. The lithium metal negative electrode material according to claim 29, characterized in that The number of heteroatoms in one, more or all of Rf is independently 1 or more.

31. The lithium metal negative electrode material according to claim 29, characterized in that The number of heteroatoms in one, more or all of Rf is selected from 1 or 2 to 6.

32. The lithium metal negative electrode material according to claim 29, characterized in that In the structure of the polymer Poly, one, more or all Rf satisfy one or more of the following characteristics: The number of oxygen atoms in one, more or all Rf is 1, 2, 3, 4 or 5; The number of nitrogen atoms in one, more or all Rf is 1, 2 or 3; The number of sulfur atoms in one, more or all Rf is 1, 2 or 3; The number of phosphorus atoms in one, more or all Rf is 1 or 2; The number of iodine atoms in one, more or all Rf is 1, 2, 3, 4, 5 or 6; The number of silicon atoms in one, more or all of Rf is 1 or 2; and The number of boron atoms in one, more than one or all of Rf is 1 or 2.

33. The lithium metal negative electrode material according to claim 29, characterized in that In the structure of the polymer Poly, one, more or all Rf contains one or more selected from iodine, -NR 12 -, -O-, -S-, -S(O)2-, >Si<, >B- and >P(=O)-, wherein R 12 H or C 1-3 alkyl.

34. The lithium metal negative electrode material according to claim 33, characterized in that R 12 is H or methyl.

35. The lithium metal negative electrode material according to claim 33, characterized in that R 12 For H.

36. The lithium metal negative electrode material according to claim 29, characterized in that In the structure of the polymer Poly, one, more or all of Rf contain one or more atoms or atomic groups selected from the group consisting of -O-, -S(O)2- and -(O=)P(O-)2.

37. The lithium metal negative electrode material according to claim 36, characterized in that One, more or all of Rf contain one or more -O-.

38. The lithium metal negative electrode material according to claim 36, characterized in that One, more or all of the Rf groups contain -S(O)2F.

39. The lithium metal negative electrode material according to claim 36, characterized in that One, more or all of the Rf groups contain -(O=)P(O-)2.

40. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that In the structure of the polymer Poly, any one Rf is independently a linear structure or a branched structure.

41. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that In the structure of the polymer Poly, any one Rf is independently a saturated structure or an unsaturated structure.

42. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The polymer Poly satisfies one or more of the following characteristics: m3 is an integer selected from 3 to 10; m 4a and m 4b are each independently an integer selected from 2 to 9; m5 is an integer selected from 3 to 10.

43. The lithium metal negative electrode material according to claim 42, characterized in that The polymer Poly satisfies one or more of the following characteristics: m3 is an integer selected from 3 to 8; m 4a and m 4b are each independently an integer selected from 2 to 8; m5 is an integer selected from 3 to 8.

44. The lithium metal negative electrode material according to claim 42, characterized in that m 4a and m 4b are each independently an integer selected from 3 to 8.

45. The lithium metal negative electrode material according to claim 42, characterized in that m 4a and m 4b are each independently an integer selected from 3 to 6.

46. ​​The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that In the structure of the polymer Poly, the structure of Rf is as shown in formula (III-1); or, the structure of Rf is as shown in formula (III-2); or, the structure of Rf is as shown in formula (III-3).

47. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that In the structure of the polymer Poly, each time formula (III-1) appears, the number of H atoms therein is 0, 1, 2, 3 or 4; each time formula (III-2) appears, the number of H atoms therein is 0, 1, 2, 3, 4, 5 or 6; each time formula (III-3) appears, the number of H atoms therein is 0, 1, 2, 3 or 4.

48. The lithium metal negative electrode material according to claim 47, characterized in that The number of H atoms in formula (III-1) is 0.

49. The lithium metal negative electrode material according to claim 47, characterized in that The number of H atoms in formula (III-2) is 0.

50. The lithium metal negative electrode material according to claim 47, characterized in that The number of H atoms in formula (III-3) is 0.

51. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that In the structure of the polymer Poly, any one Rf is independently any of the following structures: 、 、 、 、 、 、 and .

52. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The number average molecular weight of the polymer Poly is selected from 10 kDa to 200 kDa.

53. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The number average molecular weight of the polymer Poly is selected from 40 kDa to 100 kDa.

54. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The number average molecular weight of the polymer Poly is selected from 50 kDa to 80 kDa.

55. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The lithium-containing metal includes lithium element or lithium alloy.

56. The lithium metal negative electrode material according to claim 55, characterized in that The lithium alloy contains lithium element and also contains one or more elements selected from the group consisting of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel and titanium.

57. The lithium metal negative electrode material according to any one of claims 1 to 19, characterized in that The amount of lithium metal in the lithium-containing metal relative to the polymer Poly is greater than or equal to the catalyst amount, calculated by molar ratio.

58. A negative electrode plate, characterized in that The negative electrode comprises a lithium-containing layer and a polymer layer stacked together, and the negative electrode sheet comprises the lithium metal negative electrode material according to any one of claims 1 to 57; The lithium-containing layer includes the lithium-containing metal in the lithium metal negative electrode material, and the polymer layer includes the polymer Poly in the lithium metal negative electrode material.

59. The negative electrode plate according to claim 58, characterized in that The lithium-containing layer is composed of the lithium-containing metal.

60. The negative electrode plate according to claim 58, characterized in that The material of the lithium-containing layer is lithium element.

61. The negative electrode plate according to claim 58, characterized in that The material of the lithium-containing layer is lithium alloy.

62. The negative electrode plate according to claim 58, characterized in that The polymer layer further contains a first electrolyte, which contains a lithium salt and a first electrolyte solvent.

63. The negative electrode plate according to claim 62, characterized in that: Meet one or more of the following characteristics; The lithium salt includes one or more of lithium hexafluorophosphate, tetrafluoroboric acid, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalatoborate, lithium perchlorate and lithium bis(oxalate)borate; The first electrolyte solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, butylene carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxolane, methyl nonafluoro-n-butyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, octafluoropentyl-tetrafluoroethyl ether, 1,2-bis(cyanoethoxy)ethane, diphenyl ether and 18-crown-6.

64. The negative electrode plate according to claim 62, characterized in that The concentration of the lithium salt in the first electrolyte is selected from 0.2 mol / L to 8 mol / L.

65. The negative electrode plate according to claim 62, characterized in that The concentration of the lithium salt in the first electrolyte is selected from 0.5 mol / L to 5 mol / L.

66. The negative electrode plate according to claim 62, characterized in that The concentration of the lithium salt in the first electrolyte is selected from 0.5 mol / L to 2 mol / L.

67. The negative electrode plate according to claim 62, characterized in that The mass proportion of the first electrolyte in the polymer layer is 20% to 80%.

68. The negative electrode plate according to claim 62, characterized in that The mass proportion of the first electrolyte in the polymer layer is 30% to 60%.

69. The negative electrode plate according to claim 62, characterized in that The mass proportion of the first electrolyte in the polymer layer is 40% to 60%.

70. The negative electrode plate according to claim 62, characterized in that The mass proportion of the first electrolyte in the polymer layer is 40% to 55%.

71. The negative electrode plate according to claim 62, characterized in that The mass ratio of the polymer Poly to the first electrolyte is 4:1 to 0.25:

1.

72. The negative electrode plate according to claim 62, characterized in that The mass ratio of the polymer Poly to the first electrolyte is 3:1 to 0.5:

1.

73. The negative electrode plate according to claim 62, characterized in that The mass ratio of the polymer Poly to the first electrolyte is 2.5:1 to 1:

1.

74. The negative electrode plate according to claim 62, characterized in that The mass ratio of the polymer Poly to the first electrolyte is 7:3 to 2:

1.

75. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the swelling rate of the polymer layer at 25° C. is 8% to 65%.

76. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the swelling rate of the polymer layer at 25° C. is 15% to 55%.

77. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the swelling rate of the polymer layer at 25° C. is 18% to 44%.

78. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the swelling rate of the polymer layer at 25° C. is 30%-40%.

79. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.001 mS / cm to 5 mS / cm.

80. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.1 mS / cm to 5 mS / cm.

81. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.5 mS / cm to 5 mS / cm.

82. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.9 mS / cm to 4.8 mS / cm.

83. The negative electrode plate according to claim 62, characterized in that Based on the first electrolyte, the ionic conductivity of the swollen polymer layer at 25° C. is selected from 0.95 mS / cm to 2.6 mS / cm.

84. The negative electrode plate according to claim 58, characterized in that The thickness of the polymer layer is 5 nm to 10 μm.

85. The negative electrode plate according to claim 84, characterized in that The thickness of the polymer layer is 0.02 μm to 8 μm.

86. The negative electrode plate according to claim 84, characterized in that The thickness of the polymer layer is 0.05 μm to 8 μm.

87. The negative electrode plate according to claim 84, characterized in that The thickness of the polymer layer is 0.05 μm to 5 μm.

88. The negative electrode plate according to claim 84, characterized in that The thickness of the polymer layer is 0.1 μm to 5 μm.

89. The negative electrode plate according to claim 58, characterized in that The elastic modulus of the polymer layer at 25° C. is 0.1 MPa to 65 MPa.

90. The negative electrode plate according to claim 89, characterized in that The elastic modulus of the polymer layer at 25° C. is 0.5 MPa to 50 MPa.

91. The negative electrode plate according to claim 89, characterized in that The elastic modulus of the polymer layer at 25° C. is 10 MPa to 46 MPa.

92. The negative electrode plate according to claim 89, characterized in that The elastic modulus of the polymer layer at 25° C. is 18 MPa to 41 MPa.

93. The negative electrode plate according to claim 89, characterized in that The elastic modulus of the polymer layer at 25° C. is 29 MPa to 41 MPa.

94. The negative electrode plate according to claim 58, characterized in that The elastic deformation range of the polymer layer at 25° C. is 55% to 350%.

95. The negative electrode plate according to claim 94, characterized in that The elastic deformation range of the polymer layer at 25° C. is 150% to 350%.

96. The negative electrode plate according to claim 94, characterized in that The elastic deformation range of the polymer layer at 25° C. is 150% to 300%.

97. The negative electrode plate according to claim 94, characterized in that The elastic deformation range of the polymer layer at 25° C. is 168% to 280%.

98. A lithium metal secondary battery, characterized in that It comprises a positive electrode sheet, a separator and the negative electrode sheet according to any one of claims 58 to 97, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the polymer layer is arranged on the side of the negative electrode sheet close to the separator.

99. The lithium metal secondary battery according to claim 98, characterized in that The lithium metal secondary battery further includes a second electrolyte, and the components of the second electrolyte and the first electrolyte in the polymer layer may be the same or different.

100. An electrical device, characterized in that: It includes the lithium metal secondary battery according to claim 98 or 99.

101. Use of a monomer composition in preparing a negative electrode sheet or a lithium metal secondary battery, characterized in that: The monomer composition includes a first monomer represented by formula (M1) and a second monomer represented by formula (M2): ； wherein X1, X2, Y1, Y2, A1, and A2 are as defined in any one of claims 9 to 15; Rf and Rd are as defined in any one of claims 9, 16 to 19, 23 to 41, and 46 to 51; z is as defined in claim 1, 7, or 8; at least one of Y1 and Y2 is a cyano group; The negative electrode plate includes a lithium-containing layer, and the lithium-containing layer contains lithium metal; The first monomer and the second monomer are used to form a polymer layer bonded to the lithium metal in the negative electrode plate.

102. The use according to claim 101, characterized in that The method comprises the following steps: the first monomer and the second monomer are brought into contact with lithium metal in the lithium-containing layer, and the polymer layer is formed through an in-situ polymerization reaction.

103. The use according to claim 101, characterized in that The negative electrode plate is as defined in any one of claims 58 to 97, and the lithium metal secondary battery is as defined in claim 98 or 99.

104. A method for preparing a negative electrode sheet, characterized in that: The steps include: Providing a negative electrode substrate, wherein the outermost layer of at least one side of the negative electrode substrate is a lithium-containing layer, and the lithium-containing layer contains lithium metal; and also providing a reaction mixture containing a monomer composition and a first electrolyte; The reaction mixture is applied to the surface of the lithium-containing layer on at least one side of the negative electrode substrate, so that the monomer composition contacts at least a catalytic amount of lithium metal, and the monomer composition undergoes an in-situ polymerization reaction to form a polymer Poly bonded to the lithium metal in the lithium-containing layer; wherein the monomer composition is as defined in claim 101; The first electrolyte is as defined in any one of claims 62 to 74.

105. The preparation method according to claim 104, characterized in that The reaction temperature of the in-situ polymerization is selected from 30°C to 100°C.

106. The preparation method according to claim 104, characterized in that The reaction temperature of the in-situ polymerization is selected from 30°C to 60°C.

107. The preparation method according to claim 104, characterized in that The reaction temperature of the in-situ polymerization is selected from 40°C to 80°C.

108. The preparation method according to claim 104, characterized in that The reaction time of the in-situ polymerization is selected from 0.1 h to 24 h.

109. The preparation method according to claim 104, characterized in that The reaction time of the in-situ polymerization is selected from 0.1 h to 12 h.

110. The preparation method according to claim 104, characterized in that The reaction time of the in-situ polymerization is selected from 0.1 h to 6 h.

111. The preparation method according to any one of claims 104 to 110, characterized in that A polymer layer of the negative electrode sheet according to any one of claims 58 to 97 is formed on the surface of the negative electrode sheet substrate.

112. The preparation method according to any one of claims 104 to 110, characterized in that The negative electrode plate substrate is a pure lithium plate or a lithium alloy.

113. The preparation method according to claim 112, characterized in that The mass proportion of lithium element in the lithium alloy is ≥50%.

114. The preparation method according to any one of claims 104 to 110, characterized in that The negative electrode plate is defined in any one of claims 58 to 97.

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