Lithium-coated compositions, negative electrode sheets, secondary batteries, battery modules, battery packs, electrical devices, methods, and applications.

Abstract

This application discloses a lithium-coated composition comprising a lithium-containing metal and a polymer Poly chemically bonded to the lithium surface of the lithium-containing metal, the polymer Poly comprising the structure shown in Formula I; wherein, each occurrence of Rf is independently a fluorine-substituted aliphatic group; each occurrence of X is independently H or an electron-withdrawing group; and each occurrence of Z is independently O, S, or NR. 11 Among them, R 11 For H or C 1‑3 Alkyl group; * indicates the site of the linking end group; n is an integer selected from ≥10; at least one cyano group in the polymer Poly forms a chemical link with lithium in the lithium-containing metal.

Description

Technical Field

[0001] This application relates to the field of lithium metal secondary battery technology, and more specifically to lithium-coated compositions, negative electrode sheets, electrode assemblies, secondary batteries, battery modules, battery packs, electrical devices, methods, and applications. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

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

[0004] However, lithium metal rechargeable batteries currently on the market often suffer from rapid degradation of cycle life and lithium dendrite formation. Summary of the Invention

[0005] In view of the above problems, this application provides a lithium-coated composition, a negative electrode sheet, an electrode assembly, a secondary battery, a battery module, a battery pack, an electrical device, a method, and an application. Using this lithium-coated composition, a dense polymer layer can be formed on the surface of the lithium negative electrode, effectively suppressing the contact reaction between the electrolyte and lithium, reducing the consumption of lithium by the electrolyte, extending battery life, and further, effectively suppressing dendrite short circuit problems.

[0006] In a first aspect, this application provides a lithium-coated composition comprising a lithium-containing metal and a polymer Poly of lithium chemically linked to the lithium-containing metal, the polymer Poly comprising the structure shown in Formula I;

[0007]

[0008] in,

[0009] Each time Rf appears, it is independently a fluorine-substituted aliphatic group;

[0010] Each time X appears, it is independently either H or an electron-withdrawing group;

[0011] Each time Z appears, it is independently O, S, or NR. 11 Among them, R 11 For H or C 1-3 alkyl;

[0012] * indicates the site where the terminal base is attached;

[0013] n is an integer selected from 10 or higher;

[0014] At least one cyano group in the polymer Poly forms a chemical bond with lithium in the lithium-containing metal.

[0015] In this lithium coating composition, the polymer Poly forms a dense and uniform polymer layer on the lithium-containing metal surface. When this polymer layer is formed on the lithium-containing metal surface of the lithium metal battery negative electrode, it can act as a protective layer at the lithium metal battery negative electrode, effectively inhibiting the contact reaction between the electrolyte and lithium, reducing electrolyte and lithium consumption, improving coulombic efficiency, and extending cycle life. The polymer Poly carries a large number of cyano groups, one or more of which can form stable chemical bonds (further, covalent bonds) with lithium in lithium-containing metals, firmly binding the polymer layer to the surface of the lithium-containing metal. Therefore, during charging and discharging, when the volume changes on the negative electrode side, the polymer layer is prevented from peeling off from the lithium-containing metal surface. The polymer Poly contains a large number of fluorine-substituted aliphatic groups as side groups. On the one hand, these aliphatic side groups with a certain length enhance the elasticity of the polymer layer, preventing it from cracking under large volume deformation. On the other hand, the introduction of fluorine can effectively regulate the uniform deposition of lithium ions, improve the deposition morphology of lithium dendrites in lithium metal batteries at a certain charging current density, suppress the formation of lithium dendrites, and alleviate the volume expansion on the lithium negative electrode side. Furthermore, this dense and uniform polymer layer can be swollen by the electrolyte, and after swelling, it can provide a relatively high ionic conductivity (e.g., 10). -3 This ensures efficient lithium-ion transfer within the polymer layer and at the lithium interface, significantly reducing interfacial polarization of the cell.

[0016] In some embodiments, each time Rf appears, the fluorine substitution rate in Rf independently satisfies >50%;

[0017] Preferably, the fluorine substitution rate in Rf independently satisfies ≥55%;

[0018] Preferably, the fluorine substitution rate in Rf independently satisfies ≥65%;

[0019] Preferably, the fluorine substitution rate in Rf independently satisfies ≥70%;

[0020] Preferably, the fluorine substitution rate in Rf independently satisfies ≥80%;

[0021] Preferably, at least 50% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥80% or ≥90%.

[0022] Preferably, at least 60% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥70%, ≥80%, or ≥90%.

[0023] Preferably, at least 70% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥60%, ≥70%, ≥80%, or ≥90%.

[0024] Preferably, at least 80% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥50%, ≥60%, ≥70%, ≥80%, or ≥90%.

[0025] In some embodiments, each time Rf appears, the number of fluorine atoms in Rf is independently an integer of ≥4;

[0026] Preferably, the number of fluorine atoms in Rf is an integer selected from 4 to 20;

[0027] Preferably, the number of fluorine atoms in Rf is an integer selected from 4 to 16;

[0028] Preferably, the number of fluorine atoms in Rf is an integer selected from 4 to 15;

[0029] Preferably, the number of fluorine atoms in Rf is an integer selected from 4 to 13;

[0030] Preferably, the number of fluorine atoms in Rf is an integer selected from 4 to 10;

[0031] Alternatively, the number of fluorine atoms in Rf is independently 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13.

[0032] In some embodiments, the mass percentage of fluorine in the polymer Poly is selected from 30% to 55%;

[0033] Preferably, the mass percentage of fluorine in the polymer Poly is selected from 35% to 55%;

[0034] Preferably, the mass percentage of fluorine in the polymer Poly is selected from 30% to 50%.

[0035] By controlling one or more of the following methods—namely, the fluorine substitution rate in Rf, the number of fluorine atoms in Rf, and the mass percentage of fluorine in the polymer Poly—the uniform deposition of lithium ions can be optimally regulated, lithium dendrite formation can be suppressed, lithium-ion cycle life can be improved, short-circuit risk can be reduced, and the volume expansion on the lithium anode side can be alleviated. Taking the control of the mass percentage of fluorine in the polymer Poly as an example, it is beneficial to improve the lithium dendrite deposition morphology and alleviate the volume expansion of the lithium anode in lithium metal batteries at a certain charging current density.

[0036] In some embodiments, each occurrence of Rf contains 2 to 10 main chain carbon atoms;

[0037] Preferably, Rf contains 3 to 10 main chain carbon atoms;

[0038] Preferably, Rf contains 3 to 8 main chain carbon atoms;

[0039] Preferably, Rf contains 3, 4, 5, 6, 7 or 8 main chain carbon atoms.

[0040] In some embodiments, each time Rf appears, the number of carbon atoms in Rf is an integer selected from 2 to 10;

[0041] Preferably, the number of carbon atoms in Rf is an integer selected from 3 to 10;

[0042] Preferably, the number of carbon atoms in Rf is an integer selected from 3 to 8;

[0043] Alternatively, the number of carbon atoms in Rf is 3, 4, 5, 6, 7 or 8.

[0044] By controlling the main chain carbon atoms in Rf, the length of the Rf side groups can be further adjusted by controlling the number of carbon atoms in Rf, thereby giving the polymer layer suitable elasticity and better preventing the polymer layer from cracking under large volume deformation.

[0045] In some embodiments, each occurrence of Rf further contains one or more heteroatoms selected from the group consisting of iodine, nitrogen, oxygen, sulfur, silicon, boron, and phosphorus.

[0046] In some embodiments, each time Rf appears, the number of any one of the heteroatoms in Rf is one or more;

[0047] Preferably, the number of any one of the heteroatoms in Rf is selected from 1 to 5;

[0048] Preferably, the number of any one of the heteroatoms in Rf is selected from 1, 2, 3 or 4.

[0049] In some embodiments, each occurrence of Rf satisfies one or more of the following:

[0050] The number of oxygen atoms in Rf is 1, 2, 3, 4 or 5;

[0051] The number of nitrogen atoms in Rf is 1, 2, or 3;

[0052] The number of sulfur atoms in Rf is 1, 2, or 3;

[0053] The number of phosphorus atoms in Rf is 1 or 2;

[0054] The number of iodine atoms in Rf is 1, 2, 3, 4, 5 or 6;

[0055] The number of silicon atoms in Rf is 1 or 2; and

[0056] The number of boron atoms in Rf is 1 or 2.

[0057] In some embodiments, each occurrence of Rf contains one or more elements selected from iodine, -NR, etc. 12 Atoms or atomic groups in the group consisting of -, -O-, -S-, -S(O)2-, >Si<, >B-, and >P(=O)-, where R 12 For H or C 1-3 alkyl;

[0058] Preferably, R 12 It is H or methyl;

[0059] Alternatively, R 12 For H.

[0060] In some embodiments, each time Rf appears, Rf contains one or more atoms or groups of atoms selected from the group consisting of -O-, -S(O)2- and -(O=)P(O-)2;

[0061] Preferably, Rf contains one or more -O-;

[0062] Preferably, Rf contains -S(O)2F;

[0063] Alternatively, Rf contains -(O=)P(O-)2.

[0064] By introducing heteroatoms other than fluorine atoms into Rf, such as one or more heteroatoms from iodine, nitrogen, oxygen, sulfur, silicon, boron, and phosphorus, special properties can be imparted to the polymer layer. For example, phosphorus has a certain flame-retardant effect. Iodine can also play a role in regulating lithium-ion deposition. Furthermore, sulfonyl fluoride groups have a positive effect on improving the ionic conductivity of the polymer layer.

[0065] In some embodiments, each occurrence of the fluorine-substituted aliphatic group is independently a straight-chain structure or a branched structure.

[0066] Linear Rf chains are beneficial for improving the flexibility of polymer materials. Branched Rf chains are beneficial for improving the swelling capacity of electrolyte membranes, thereby increasing ionic conductivity.

[0067] In some embodiments, each time Rf appears, the structure of Rf is independently shown as in Equation III-1, Equation III-2, or Equation III-3:

[0068]

[0069] Among them, R 31 R32 and R 3 Each occurrence is independently H or F; each occurrence of m3 is independently an integer selected from 2 to 10; Formula III-1 contains at least 4 F atoms;

[0070] Preferably, m3 is an integer selected from 3 to 10;

[0071] Preferably, m3 is an integer selected from 3 to 8;

[0072] Alternatively, m3 is 3, 4, 5, 6, 7, or 8;

[0073] R 41a R 42a R 4a R 41b R 42b and R 4b Each occurrence is independently either H or F; m 4a and m4 4b Each occurrence is an independent integer selected from 1 to 9 (1, 2, 3, 4, 5, 6, 7, 8, and 9); Formula III-2 contains at least 4 F atoms;

[0074] Preferably, m 4a and m4 4b Each is an integer selected independently from 2 to 9;

[0075] Alternatively, m 4a and m4 4b Each is an integer selected independently from 2 to 8;

[0076] Alternatively, m 4a and m4 4b Each is an integer selected independently from 3 to 8;

[0077] Alternatively, m 4a and m4 4b Each is an integer selected independently from 3 to 6;

[0078] R 51 and R 52 Each occurrence is independently H or F; each occurrence of m5 is independently an integer selected from 2 to 10; Formula III-3 contains at least 4 F atoms;

[0079] Preferably, m5 is an integer selected from 3 to 10;

[0080] Preferably, m5 is an integer selected from 3 to 8;

[0081] Alternatively, m5 can be 3, 4, 5, 6, 7 or 8.

[0082] In some embodiments, each time Rf appears, the structure of Rf is as shown in Equation III-1;

[0083] Alternatively, each time Rf appears, the structure of Rf is as shown in Equation III-2;

[0084] Alternatively, each time Rf appears, the structure of Rf is as shown in Equation III-3.

[0085] 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 and prevent the polymer layer from cracking under large volume deformation. On the other hand, it can effectively regulate the uniform deposition of lithium ions through fluorine elements, suppress the formation of lithium dendrites, and alleviate the volume expansion on the lithium anode side.

[0086] The structure of formula III-2 can be introduced with phosphorus, in which case a phosphate ester group is formed between Z and Rf.

[0087] The structure of formula III-3 can incorporate sulfonyl fluoride groups. This has a positive effect on improving the ionic conductivity of the polymer layer.

[0088] In some embodiments, each occurrence of Formula III-1 contains 0, 1, 2, 3, or 4 H atoms; each occurrence of Formula III-2 contains 0, 1, 2, 3, 4, 5, or 6 H atoms; and each occurrence of Formula III-3 contains 0, 1, 2, 3, or 4 H atoms.

[0089] Preferably, each time Formula III-1 appears, the number of H atoms is 0; each time Formula III-2 appears, the number of H atoms is 0; each time Formula III-3 appears, the number of H atoms is 0.

[0090] By controlling the number of H atoms, the number of sites available for fluorine substitution can be regulated.

[0091] In some embodiments, each occurrence of Rf is independently selected from any of the following structures:

[0092]

[0093] In some embodiments, each occurrence of X is independently H or an electron-withdrawing group containing 1 to 6 non-hydrogen atoms.

[0094] In some embodiments, each occurrence of X is 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;

[0095] Preferably, R 21 and R 22 Each can be independently H or methyl;

[0096] Alternatively, R 21 and R 22 All are methyl groups.

[0097] Introducing an electron-withdrawing group at the X position can enhance the reactivity of carbon-carbon double bonds in cyanoacrylate derivative monomers during polymer layer formation, thereby promoting in-situ polymerization.

[0098] In some embodiments, each occurrence of Z is independently O, S, or NH;

[0099] Preferably, each occurrence of Z is independently either O or NH;

[0100] Preferably, Z is always 0.

[0101] Alternatively, Z is always NH.

[0102] The linker Z can form reactive functional group pairs with different reactive functional groups through coupling reactions, such as -COOH from cyanoacrylate derivative monomers or their derivative reactive forms (e.g., acyl chloride forms, N-succinimide ester activated forms of carboxyl groups). These pairs then generate different types of chemical bonds through coupling reactions. For example, when Z is O, S, or NH, it can be obtained through coupling reactions between -COOH from cyanoacrylate derivative monomers or their derivative reactive forms and -OH, -SH, or -NH2. The diversity of Z is a result of the flexible combination of reactive monomers.

[0103] In some implementations, Rf in Formula I is always the same; X in Formula I appears the same every time; Z in Formula I appears the same every time. In this case, a single type of monomer can be used for the polymerization reaction.

[0104] In some embodiments, n is an integer selected from 10 to 1000, preferably an integer selected from 10 to 950, preferably an integer selected from 10 to 800, preferably an integer selected from 15 to 800, preferably an integer selected from 20 to 800, preferably an integer selected from 40 to 800, preferably an integer selected from 50 to 800, preferably an integer selected from 100 to 800, preferably an integer selected from 10 to 750, preferably an integer selected from 15 to 750, preferably an integer selected from 20 to 750, and preferably an integer selected from... The integer is 40 to 750, preferably 50 to 750, preferably 80 to 750, preferably 100 to 750, preferably 10 to 650, preferably 15 to 650, preferably 20 to 650, preferably 40 to 650, preferably 50 to 650, preferably 100 to 650, preferably 150 to 500, and preferably 200 to 350.

[0105] In some embodiments, the number-average molecular weight of the polymer Poly is selected from 10 kDa to 200 kDa;

[0106] Preferably, the number-average molecular weight of the polymer Poly is selected from 50kDa to 100kDa.

[0107] In Equation I, n is numerically equal to the degree of polymerization of the polymer Poly. By controlling n, the molecular weight of the polymer Poly can be adjusted. By adjusting the degree of polymerization or molecular weight, the molecular chain length of the polymer Poly can be adjusted, achieving effective coating of lithium-containing metals, maintaining stable chemical bonds, and influencing the density and uniformity of the polymer layer.

[0108] In some embodiments, the amount of lithium in the lithium-containing metal relative to the polymer Poly is greater than the amount of catalyst, in molar ratio.

[0109] Preferably, the lithium-containing metal comprises lithium metal or a lithium alloy;

[0110] Preferably, the lithium alloy contains lithium and one or more of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium.

[0111] In this coating composition, as long as the lithium metal can provide the catalyst amount, it can smoothly catalyze the in-situ polymerization reaction of cyanoacrylate derivative monomers on the lithium metal surface.

[0112] Secondly, this application provides a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode sheet substrate and a polymer layer stacked together; the negative electrode sheet substrate includes a lithium-containing layer in contact with the polymer layer, the lithium-containing layer contains lithium, and the polymer layer is chemically bonded to at least a portion of the lithium in the lithium-containing layer;

[0113] The polymer layer comprises the polymer Poly as defined in the first aspect of this application.

[0114] The negative electrode has a dense and uniform polymer layer formed on the lithium-containing layer surface on at least one side, which can act as a protective layer at the negative electrode of the lithium metal battery. This can effectively suppress the contact reaction between the electrolyte and lithium, reduce the consumption of electrolyte and lithium, improve coulombic efficiency, and extend cycle life.

[0115] In some embodiments, the amount of lithium in the lithium-containing layer relative to the polymer Poly is greater than the amount of catalyst, in molar ratio.

[0116] Preferably, the lithium-containing layer comprises lithium metal or a lithium alloy.

[0117] Alternatively, the lithium-containing layer is substantially composed of lithium metal.

[0118] Preferably, the lithium-containing layer is a lithium alloy.

[0119] Preferably, the lithium alloy contains lithium and one or more of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium. In some embodiments, the polymer layer also contains an electrolyte. This is beneficial for providing better ionic conductivity.

[0120] In some embodiments, the electrolyte contains a lithium salt and an electrolyte solvent.

[0121] In some embodiments, the lithium salt is selected from one or more of lithium hexafluorophosphate, tetrafluoroboric acid, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium perchlorate, and lithium dioxoborate.

[0122] Preferably, the electrolyte solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, butenyl carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxapentane, methyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, octafluoropentyl-tetrafluoroethyl ether, 1,2-di(cyanoethoxy)ethane, diphenyl ether, and 18-crown ether-6.

[0123] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 10 mol / L;

[0124] Preferably, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 8 mol / L;

[0125] Preferably, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 5 mol / L;

[0126] Preferably, the concentration of the lithium salt in the electrolyte is selected from 5 mol / L to 10 mol / L;

[0127] Preferably, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 3 mol / L;

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

[0129] The concentration of lithium salts in the electrolyte also affects the deposition morphology of lithium ions. The lithium salt concentration alters the Li ion deposition morphology in the electrolyte. + The solvation effect of lithium salts influences the composition of the solid electrolyte interphase (SEI) membrane and the deposition morphology of lithium ions. By controlling the lithium salt concentration in the electrolyte to an appropriate level, dense and uniform lithium ion deposition with minimal volume expansion can be achieved. Furthermore, controlling the lithium salt concentration in the electrolyte also ensures suitable mechanical properties of the polymer layer, avoiding the negative mechanical properties caused by excessively high lithium salt concentrations. It also enables better lithium ion conductivity during charge and discharge, preventing poor lithium ion conductivity due to insufficient lithium salt concentration.

[0130] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 199:1 to 1:1;

[0131] Preferably, the mass ratio of the polymer Poly to the electrolyte is selected from 19:1 to 1:1;

[0132] Preferably, the mass ratio of the polymer Poly to the electrolyte is selected from 9.5:1 to 1:1;

[0133] Preferably, the mass ratio of the polymer Poly to the electrolyte is selected from 8:1 to 2:1;

[0134] Preferably, the mass ratio of the polymer Poly to the electrolyte is selected from 6:1 to 1:1.

[0135] In some embodiments, the electrolyte comprises, by mass percentage, 0.5% to 50% of the polymer layer;

[0136] Preferably, the electrolyte comprises 1% to 50% by mass in the polymer layer;

[0137] Preferably, the electrolyte comprises 2% to 50% by mass in the polymer layer;

[0138] Preferably, the electrolyte comprises 5% to 50% by mass in the polymer layer;

[0139] Preferably, the electrolyte comprises 8% to 50% by mass in the polymer layer;

[0140] Preferably, the electrolyte comprises 9% to 50% by mass in the polymer layer;

[0141] Preferably, the electrolyte comprises 9.5% to 50% by mass in the polymer layer;

[0142] Preferably, the electrolyte comprises 10% to 50% by mass in the polymer layer;

[0143] Preferably, the electrolyte comprises 30% to 50% by mass in the polymer layer.

[0144] The mass ratio of polymer (Poly) to electrolyte within a suitable range can be adjusted to control the electrolyte's mass percentage in the polymer layer. The electrolyte's mass percentage in the polymer layer affects the elasticity and ionic conductivity of the protective layer. The presence of a certain amount of lithium salt and solvent plasticizes the polymer layer, improving its elasticity. Furthermore, during the in-situ polymerization process, lithium salt and solvent are incorporated into the polymer layer, resulting in a microscopic, sponge-like, porous structure with pores filled by the electrolyte, providing pathways for subsequent lithium ion transport.

[0145] In some embodiments, the thickness of the polymer layer is selected from 5 nm to 10 μm;

[0146] Preferably, the thickness of the polymer layer is selected from 50 nm to 8 μm;

[0147] Preferably, the thickness of the polymer layer is selected from 50 nm to 5 μm;

[0148] Preferably, the thickness of the polymer layer is selected from 100 nm to 5 μm.

[0149] The polymer layer structure on the lithium-containing metal surface can be controlled at the nanoscale, which is beneficial for the assembled battery cell to exhibit a smaller interfacial impedance.

[0150] In some embodiments, the elastic modulus of the polymer layer at 25°C is 0.1 MPa to 80 MPa;

[0151] Preferably, the elastic modulus of the polymer layer at 25°C is 0.5 MPa to 50 MPa;

[0152] Preferably, the polymer layer has an elastic modulus of 1 MPa to 50 MPa at 25°C.

[0153] Preferably, the polymer layer has an elastic modulus of 10 MPa to 50 MPa at 25°C.

[0154] In some embodiments, the elastic deformation range of the polymer layer at 25°C is 20% to 500%.

[0155] Preferably, the polymer layer has an elastic deformation range of 20% to 300% at 25°C;

[0156] Preferably, the polymer layer has an elastic deformation range of 20% to 200% at 25°C;

[0157] Preferably, the polymer layer has an elastic deformation range of 100% to 300% at 25°C;

[0158] Preferably, the polymer layer has an elastic deformation range of 100% to 200% at 25°C;

[0159] Preferably, the polymer layer has an elastic deformation range of 100% to 190% at 25°C.

[0160] In some embodiments, based on the electrolyte, the swelling rate of the polymer layer at 25°C is selected from 5% to 50%;

[0161] Preferably, the swelling rate of the polymer layer at 25°C is selected from 10% to 50%;

[0162] Preferably, the swelling rate of the polymer layer at 25°C is selected from 10% to 45%;

[0163] Preferably, the swelling rate of the polymer layer at 25°C is selected from 20% to 45%.

[0164] In some embodiments, based on the electrolyte, the ionic conductivity of the swollen polymer layer is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -6 S / cm;

[0165] Preferably, the ionic conductivity of the swollen polymer layer at 25°C is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -5 S / cm;

[0166] Preferably, the ionic conductivity of the swollen polymer layer at 25°C is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -4 S / cm;

[0167] Preferably, the ionic conductivity of the swollen polymer layer at 25°C is selected from 3 × 10⁻⁶. -3 S / cm to 1×10 -4 S / cm;

[0168] Preferably, the ionic conductivity of the swollen polymer layer at 25°C is selected from 3 × 10⁻⁶. -3 S / cm up to 5×10 -4 S / cm.

[0169] In some embodiments, the negative electrode substrate further includes a negative electrode current collector; the negative electrode current collector is located on the side of the lithium-containing layer away from the polymer layer.

[0170] In some embodiments, a second negative electrode active material layer may or may not be provided between the negative electrode current collector and the lithium-containing layer, and the composition of the second negative electrode active material layer and the lithium-containing layer may be the same or different.

[0171] Thirdly, this application provides an electrode assembly comprising a positive electrode sheet, a separator, and a negative electrode sheet as described in the second aspect of this application, wherein the separator is disposed between the negative electrode sheet and the positive electrode sheet; and the polymer layer is disposed at least on the surface of the aforementioned negative electrode sheet substrate near the separator.

[0172] The negative electrode in this electrode assembly has a dense and uniform polymer layer formed on the lithium-containing layer surface of at least one side, which can act as a protective layer at the negative electrode of the lithium metal battery, effectively suppressing the contact reaction between the electrolyte and lithium, reducing the consumption of electrolyte and lithium, improving coulombic efficiency, and extending cycle life.

[0173] Fourthly, this application provides a secondary battery, which includes a cell electrolyte and the electrode assembly described in the third aspect of this application, wherein the cell electrolyte is disposed between the polymer layer and the positive electrode sheet.

[0174] The negative electrode sheet in this secondary battery has a dense and uniform polymer layer formed on the lithium-containing layer surface on at least one side, which can act as a protective layer at the negative electrode of the lithium metal battery, effectively suppressing the contact reaction between the electrolyte and lithium, reducing the consumption of electrolyte and lithium, improving coulombic efficiency, and extending cycle life.

[0175] In some embodiments, the composition of the electrolyte in the battery cell and the electrolyte in the polymer layer may be the same or different.

[0176] In some embodiments, the charging current density of the secondary battery is selected from 0.3 mA / cm². 2 ~12mA / cm 2 ;

[0177] Preferably, the charging current density of the secondary battery is selected from 1 mA / cm². 2 ~10mA / cm 2 ;

[0178] Preferably, the charging current density of the secondary battery is selected from 1 mA / cm². 2 ~6mA / cm 2 .

[0179] Fifthly, this application provides a battery module that includes the secondary battery described in the fourth aspect of this application.

[0180] Sixthly, this application provides a battery pack that includes the battery module described in the fifth aspect of this application.

[0181] In a seventh aspect, this application provides an electrical device comprising one or more of the secondary battery described in the fourth aspect of this application, the battery module described in the fifth aspect of this application, and the battery pack described in the sixth aspect of this application.

[0182] Eighthly, this application provides the use of monomer compound II in the preparation of negative electrode sheets, wherein the structure of monomer compound II is shown in Formula II:

[0183]

[0184] Rf, Z, and X are each independently defined as in the first aspect of this application.

[0185] In some embodiments, the monomer compound II contacts lithium in the lithium-containing layer of the negative electrode substrate and forms a polymer layer through in-situ polymerization.

[0186] The monomer compound II is a cyanoacrylate derivative compound, in which the cyano group can contact the lithium in the outermost layer of the negative electrode substrate to form a chemical bond, and the carbon-carbon double bond can undergo an in-situ polymer reaction under lithium catalysis, thereby preparing the lithium-coated composition described in the first aspect of this application. At this time, a firmly connected, dense and uniform polymer layer is formed on the surface of the lithium-containing layer of the negative electrode, which can play the aforementioned protective layer role.

[0187] Ninthly, this application provides a method for preparing a negative electrode sheet, which includes the following steps:

[0188] A negative electrode substrate is provided, wherein the outermost layer of at least one side of the negative electrode substrate is a lithium-containing layer, the lithium-containing layer comprising a lithium-containing metal; a reaction mixture containing monomer compound II and an electrolyte is also provided.

[0189] The reaction mixture is coated onto the lithium-containing layer surface of at least one side of the negative electrode substrate, and the monomer compound II is polymerized in situ to form a polymer layer;

[0190]

[0191] Wherein, Rf, Z and X are each independently as defined in the first aspect of this application;

[0192] The electrolyte is as defined in the second aspect of this application.

[0193] In the presence of an electrolyte, the cyano group in monomer compound II can form a chemical bond (covalent bond) with the lithium in the outermost layer of the negative electrode substrate. The carbon-carbon double bond can undergo an in-situ polymer reaction under lithium catalysis to form the polymer Poly shown in Formula I, thereby preparing the lithium-coated composition described in the first aspect of this application. At this point, a firmly bonded, dense, and uniform polymer layer is formed on the surface of the lithium-containing layer, which can perform the aforementioned protective layer function. Compared to the physical coating method in conventional technologies, this method not only stably binds to the surface of the lithium-containing layer through chemical bonding, preventing it from detaching from the lithium-containing layer surface during charging and discharging, but also produces a dense and uniform coating with a thickness that can be controlled at the nanoscale. The assembled battery cell can exhibit a lower interfacial impedance.

[0194] In some embodiments, this application provides that the monomer compound II is contacted with at least a catalytic amount of lithium. This provides chemical bonding sites for the polymer layer and effectively catalyzes the in-situ polymerization of cyanoacrylate derivative monomers.

[0195] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 199:1 to 1:1;

[0196] Preferably, the mass ratio of the polymer Poly to the electrolyte is selected from 19:1 to 1:1;

[0197] Preferably, the mass ratio of the monomer compound II to the electrolyte is selected from 9.5:1 to 1:1;

[0198] Preferably, the mass ratio of the monomer compound II to the electrolyte is selected from 8:1 to 2:1;

[0199] Preferably, the mass ratio of the monomer compound II to the electrolyte is selected from 6:1 to 1:1.

[0200] By controlling the mass ratio of monomer compound II to electrolyte, the mass ratio of polymer (Poly) to electrolyte in the generated polymer layer can be controlled.

[0201] In some embodiments, in the step of coating the reaction mixture onto the lithium-containing layer surface of at least one side of the negative electrode substrate, the coating method is selected from any one of coating, spraying, spin coating and vapor deposition.

[0202] In some embodiments, the reaction temperature of the in-situ polymerization is selected from 30°C to 100°C;

[0203] Preferably, the reaction temperature of the in-situ polymerization is selected from 30℃ to 50℃;

[0204] Preferably, the reaction temperature of the in-situ polymerization is selected from 40℃ to 60℃.

[0205] In some embodiments, the reaction time for the in-situ polymerization is selected from 0.1 h to 24 h;

[0206] Preferably, the reaction time for the in-situ polymerization is selected from 0.1 h to 12 h;

[0207] Preferably, the reaction time for the in-situ polymerization is selected from 0.1 h to 2 h.

[0208] In some embodiments, in the step of coating the reaction mixture onto the lithium-containing layer surface of at least one side of the negative electrode substrate, the coating thickness of the reaction mixture is selected from 100 nm to 8 μm;

[0209] Preferably, the coating thickness of the reaction mixture is selected from 50 nm to 5 μm;

[0210] Preferably, the coating thickness of the reaction mixture is selected from 50 nm to 8 μm.

[0211] In some embodiments, the polymer layer formed is as defined in the second aspect of this application.

[0212] In some embodiments, the negative electrode substrate is a pure lithium sheet. In this case, an additional negative current collector can be introduced into the battery negative electrode to facilitate the assembly of the tab, or a pure lithium sheet covered with a polymer layer can be used as the negative electrode.

[0213] In some embodiments, the negative electrode substrate further includes a negative electrode current collector; the negative electrode current collector is located on the side of the lithium-containing layer away from the polymer layer.

[0214] In some embodiments, a second negative electrode active material layer may or may not be provided between the negative electrode current collector and the lithium-containing layer, and the composition of the second negative electrode active material layer and the lithium-containing layer may be the same or different.

[0215] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0216] To better describe and illustrate embodiments or examples of the applications disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the embodiments or examples currently described, or the best mode of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. It should also be noted that the drawings are drawn in a simplified form and are intended only to facilitate and clarify the illustration of the invention. The various dimensions of each part shown in the drawings are arbitrarily shown and may be precise or not drawn to scale. For example, the dimensions of parts are appropriately exaggerated in some places in the drawings to make the illustration clearer. Unless otherwise specified, the parts in the drawings are not drawn to scale. The invention does not limit every dimension of every part. In the drawings:

[0217] Figure 1 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application, wherein a polymer layer is provided on one side of the negative electrode sheet;

[0218] Figure 2 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application. A polymer layer and a negative current collector are provided on one side of the negative electrode sheet.

[0219] Figure 3 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application. A second negative electrode active material layer is also provided between the lithium-containing layer and the negative electrode current collector.

[0220] Figure 4 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of this application, wherein polymer layers are provided on both sides of the negative electrode sheet;

[0221] Figure 5 This is a schematic diagram of the structure of a negative electrode sheet according to an embodiment of the present application. Polymer layers are provided on both sides of the negative electrode sheet, and a second negative electrode active material layer is provided between the lithium-containing layer on both sides and the negative electrode current collector.

[0222] Figure 6 This is a schematic diagram of a secondary battery according to an embodiment of this application;

[0223] Figure 7 yes Figure 6 An exploded view of a secondary battery according to an embodiment of this application is shown;

[0224] Figure 8This is a schematic diagram of a battery module according to an embodiment of this application;

[0225] Figure 9 This is a schematic diagram of a battery pack according to an embodiment of this application;

[0226] Figure 10 yes Figure 9 An exploded view of a battery pack according to an embodiment of this application is shown;

[0227] Figure 11 This is a schematic diagram of an electrical device in which a secondary battery is used as a power source, according to an embodiment of this application.

[0228] Explanation of reference numerals in the attached drawings: 100, negative electrode substrate; 110, negative electrode current collector; 120, second negative electrode active material layer; 130, lithium-containing layer; 200, polymer layer; 1, battery pack; 2, upper casing; 3, lower casing; 4, battery module; 5, secondary battery; 51, casing; 52, electrode assembly; 53, cover plate. Detailed Implementation

[0229] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the lithium-coated composition, negative electrode sheet, electrode assembly, secondary battery, battery module, battery pack, power supply device, method, and application of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0230] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0231] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0232] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0233] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0234] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0235] 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". More specifically, 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).

[0236] In this application, the terms "multiple", "various", "multiple times", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0237] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0238] In this document, the term "suitable" as used in "suitable combination", "suitable method", "any suitable method", etc., refers to the technical solution that enables the implementation of this application.

[0239] In this document, terms such as "preferred," "better," "more suitable," and "ideal" are merely descriptions of more effective implementation methods or embodiments, and should be understood not to limit the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "preferred" term shall be independent.

[0240] In this application, "optionally" means optional.

[0241] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0242] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0243] High energy density is an irreversible trend in the future development of lithium metal batteries, featuring high specific capacity (3860mAh / g) and extremely low potential (-3.04V vs. H2 / H). +Lithium metal anodes have therefore attracted widespread attention in the industry. However, the high reactivity of lithium metal and the dendrite short-circuit problem greatly limit its further development. Lithium metal is highly reactive and easily undergoes side reactions with the electrolyte, consuming both electrolyte and lithium metal, forming a thick passivation layer, and causing a rapid decline in battery cycle life. Furthermore, during charging, the uneven deposition of lithium ions due to regional differences in ion and electron flow leads to dendrite formation. Lithium dendrites have a high specific surface area, which exacerbates electrolyte consumption and can even cause battery degradation; on the other hand, the rapid growth of lithium dendrites can penetrate the separator, posing a short-circuit risk.

[0244] A highly elastic lithium metal protective layer with lithium-ion transport and regulation functions and a tight bond with lithium metal has the potential to solve the above problems. First, the presence of the protective layer reduces direct contact between the electrolyte and lithium metal, suppressing side reactions and reducing electrolyte and lithium metal consumption. Second, the high ionic conductivity and functionalized group design of the protective layer not only ensures effective lithium-ion transport within the protective layer and at the lithium metal interface, but also regulates uniform lithium-ion deposition, suppresses lithium dendrite formation, reduces electrolyte consumption, and prevents dendrites from piercing the separator and causing short circuits. Furthermore, the tight bond between the protective layer and lithium metal prevents the coating from peeling off the lithium metal surface during charging and discharging due to volume changes on the negative electrode side.

[0245] The inventors of this application have discovered that current methods all involve attaching protective layers 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 relatively weak. During long-term cycling, due to volume changes on the negative electrode side, the protective layer easily detaches from the lithium metal. Furthermore, the functional groups contained in the protective layer do not regulate lithium deposition. In addition, if the protective layer is prepared separately beforehand and then attached between the lithium metal and the separator, the operation is complex, and the flatness of the thin layer is difficult to guarantee. To ensure good wettability on the lithium metal surface, a high-viscosity polymer solution is used to coat the lithium metal surface, but this results in a relatively thick protective layer.

[0246] In response to the aforementioned common technical problems, in a first aspect, this application includes a lithium-containing metal and a polymer Poly chemically bonded to the lithium surface of the lithium-containing metal. The polymer Poly has a repeating unit structure formed by cyanoacrylate derivative monomers, and carries a large number of cyano groups and fluorine-substituted aliphatic groups. At least one cyano group in the polymer Poly is chemically bonded to the lithium in the lithium-containing metal (further, covalently bonded).

[0247] In some embodiments, a lithium coating composition is provided, comprising a lithium-containing metal and a polymer Poly chemically bonded to the lithium surface of the lithium-containing metal, the polymer Poly comprising the structure shown in Formula I;

[0248]

[0249] in,

[0250] Each time Rf appears, it is independently a fluorine-substituted aliphatic group;

[0251] Each time X appears, it is independently either H or an electron-withdrawing group;

[0252] Each occurrence of Z is independently O, S, or NR11; where R11 is H or C. 1-3 alkyl;

[0253] * indicates the site where the terminal base is attached;

[0254] n is an integer selected from 10 or higher;

[0255] At least one cyano group in the polymer Poly forms a chemical bond (further, a covalent bond) with lithium in the lithium-containing metal.

[0256] In the main chain of polymer Poly, a cyano group is attached to the carbon atom of the Rf side group. The inventors discovered that the cyano group at this position is beneficial to the polymerization reaction of cyanoacrylate derivative monomers. This is because the cyano group is an electron-withdrawing group. During the polymerization reaction, the carbon atom attached to the cyano group can form a relatively stable anionic active center, thereby continuing chain growth until chain termination.

[0257] In this application, the term "lithium-containing metal" can refer to a substance substantially composed of lithium (Li) metal, a lithium alloy, or a composition comprising lithium metal and a lithium alloy. "Substantially composed of lithium metal" indicates that the weight percentage of metallic lithium is very high; for example, "substantially" describes a percentage greater than 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 100%, etc.

[0258] In this application, the terms "lithium metal" or "lithium metal" refer to lithium in its metallic state.

[0259] In this application, the term "lithium" used independently, unless otherwise specified, refers to lithium in its metallic state. For example, "lithium" in the context of lithium-containing metals.

[0260] In this application, the term "lithium alloy" refers to an alloy containing lithium. In addition to lithium, a lithium alloy may also contain one or more other metals. All reported lithium alloys 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 with 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. In this application, the "chemical link" between the cyano group and lithium, unless otherwise specified, refers to a covalent link.

[0261] In this application, the term "cyanoacrylate derivative monomer" refers to monomers having The derivatives of the skeleton shown can be linked to the aforementioned fluorine-substituted aliphatic groups via linkers such as ester or amide groups. In this application, the term "aliphatic group" refers to a group containing at least one carbon atom and not containing any aromatic groups, and when the aliphatic group contains only one carbon atom, that carbon atom is connected to four adjacent atoms via four single bonds (i.e., excluding substituted methylene groups such as carbonyl groups). The aliphatic group is allowed to contain one or more heteroatoms, examples of which include, but are not limited to, fluorine, iodine, nitrogen, oxygen, sulfur, silicon, boron, and phosphorus.

[0262] The aliphatic group can be an aliphatic hydrocarbon group, in which one or more hydrogen atoms can be independently replaced by non-fluorine heteroatoms, or in which one or more carbon atoms can be independently replaced by heteroatoms. Simultaneous substitution of hydrogen and carbon atoms is permitted.

[0263] In this application, the term "hydrocarbon group" refers to a monovalent group composed of carbon and hydrogen. Hydrocarbon groups can be in the form of alkyl, alkenyl, alkynyl, etc.

[0264] In this application, the term "alkyl" refers to a monovalent residue formed by the loss of a hydrogen atom from a saturated hydrocarbon comprising a primary, secondary, tertiary, or quaternary carbon atom, or a combination thereof. Phrases containing this term, such as "C", are also used. 1～10 "Alkyl" refers to an alkyl group containing 1 to 10 carbon atoms. Each time it appears, it can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, C9 alkyl, or C 10Alkyl groups. 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).

[0265] In this application, the term "alkenyl" refers to a compound containing at least one unsaturated site (i.e., carbon-carbon sp). 2 A monovalent residue formed by the loss of a hydrogen atom in a hydrocarbon with a double bond. Phrases containing this term include, for example, "C2~C". 10 "Alkenyl" or "C" 2-9 "Alkenyl" refers to an alkenyl group containing 2 to 9 carbon atoms. Each time it appears, it can independently be C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl, C6 alkenyl, C7 alkenyl, C8 alkenyl, C9 alkenyl, or C... 10Alkenyl. Suitable examples include, but are not limited to: vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7) and 5-hexenyl (-CH2CH2CH2CH2CH=CH2).

[0266] In this application, the term "alkynyl" refers to a monovalent residue formed by the loss of a hydrogen atom from a hydrocarbon having at least one unsaturated site, i.e., a carbon-carbon sp triple bond. Phrases containing this term include, for example, "C2~C..." 10 "Alynyl" refers to an alkynyl group containing 2 to 9 carbon atoms. Each time it appears, it can independently be C2-alkynyl, C3-alkynyl, C4-alkynyl, C5-alkynyl, C6-alkynyl, C7-alkynyl, C8-alkynyl, C9-alkynyl, or C... 10 Alkyne group. Suitable examples include, but are not limited to, ethynyl (-C≡CH) and propyne (-CH2C≡CH).

[0267] In this application, the terminology used to refer to the end groups of polymer Poly, unless otherwise specified, refers to the end groups formed by the polymerization reaction of carbon-carbon double bonds. The type of end group is related to factors such as the initiator used and the end-capping group in the termination reaction. When the end groups of polymer Poly are described using "*", they can be understood in conjunction with the polymer reaction-related descriptions in this application. Those skilled in the art can correctly understand the structure of polymer Poly.

[0268] In some embodiments, Rf is a fluorine-substituted hydrocarbon group.

[0269] In some embodiments, Rf is a fluorine-substituted alkyl group.

[0270] In some embodiments, Rf is a fluorine-substituted alkenyl group.

[0271] In some embodiments, Rf is a fluorine-substituted alkynyl group.

[0272] In this lithium-coated composition, the polymer Poly forms a dense and uniform polymer layer on the surface of the lithium-containing metal, which acts as a protective layer at the negative electrode of the lithium metal battery. This effectively inhibits the contact reaction between the electrolyte and lithium, reduces electrolyte and lithium consumption, improves coulombic efficiency, and extends cycle life. The polymer Poly carries a large number of cyano groups, one or more of which can form stable chemical bonds (covalent bonds) with the lithium in the lithium-containing metal, firmly binding the polymer layer to the surface of the lithium-containing metal. Therefore, during charge and discharge, when the volume changes on the negative electrode side, the polymer layer is prevented from peeling off from the lithium-containing metal surface. The polymer Poly contains a large number of fluorine-substituted aliphatic groups as side groups. On the one hand, these aliphatic side groups with a certain length enhance the elasticity of the polymer layer, preventing it from cracking under large volume deformation. On the other hand, the introduction of fluorine can effectively regulate the uniform deposition of lithium ions, improve the deposition morphology of lithium dendrites in the lithium metal battery at a certain charging current density, inhibit the formation of lithium dendrites, and alleviate the volume expansion on the lithium negative electrode side. Furthermore, this dense and uniform polymer layer can be swollen by the electrolyte, and after swelling, it can provide a higher ionic conductivity (e.g., 10). - 3 This ensures efficient lithium-ion transfer within the polymer layer and at the lithium interface, significantly reducing interfacial polarization of the cell.

[0273] In some embodiments, each time Rf appears, the fluorine substitution rate in Rf independently satisfies >50%.

[0274] In some embodiments, the fluorine substitution rate in Rf independently satisfies ≥55%.

[0275] In some embodiments, the fluorine substitution rate in Rf independently satisfies ≥65%.

[0276] In some embodiments, the fluorine substitution rate in Rf independently satisfies ≥70%.

[0277] In some embodiments, the fluorine substitution rate in Rf independently satisfies ≥80%.

[0278] In some embodiments, at least 50% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥80% or ≥90%.

[0279] In some embodiments, at least 60% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥70%, ≥80%, or ≥90%.

[0280] In some embodiments, at least 70% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥60%, ≥70%, ≥80%, or ≥90%.

[0281] In some embodiments, at least 80% of the Rf in the polymer Poly satisfies a fluorine substitution rate of ≥50%, ≥60%, ≥70%, ≥80%, or ≥90%.

[0282] In this application, for percentage ranges defined by “≥”, such as ≥50% and ≥60%, unless otherwise specified, the upper limit is 100%, that is, ≥50% and ≥60% have the same meaning as 50% to 100% and 60% to 100%, respectively.

[0283] In this application, "fluorine substitution rate in Rf" refers to the molar percentage of fluorine atoms, based on the number of substituted hydrogen atoms in the Rf group. The "number of substituted hydrogen atoms" can be understood as the number of substituted sites in the Rf group, that is, the maximum number of hydrogen atoms that can be bonded to carbon atoms and possible heteroatoms (such as phosphorus atoms, nitrogen atoms, sulfur atoms, etc.). The hydrogen atoms can also be substituted by other elements (in which case the sites occupied by other elements are also included in the base number).

[0284] The fluorine substitution rate in Rf can also be selected from any one percentage or any range of two percentages: 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, and 100%. Non-limiting examples of any range of two percentages include 30%–100% and 35%–100%.

[0285] In some embodiments, each time Rf appears, the number of fluorine atoms in Rf is independently an integer of ≥4.

[0286] In some embodiments, the number of fluorine atoms in Rf is independently an integer selected from 4 to 20.

[0287] In some embodiments, the number of fluorine atoms in Rf is independently an integer selected from 4 to 16.

[0288] In some embodiments, the number of fluorine atoms in Rf is independently an integer selected from 4 to 15.

[0289] In some embodiments, the number of fluorine atoms in Rf is independently an integer selected from 4 to 13.

[0290] In some embodiments, the number of fluorine atoms in Rf is independently an integer selected from 4 to 10.

[0291] In some embodiments, the number of fluorine atoms in Rf is independently 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13.

[0292] The number of fluorine atoms in Rf can also be selected from any one of the following values ​​or any range of two values: 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc. Non-restrictive examples of any range of two values ​​are 4 to 20, 4 to 16, etc.

[0293] In some embodiments, the mass percentage of fluorine in the polymer Poly is selected from 30% to 55%.

[0294] In some embodiments, the mass percentage of fluorine in the polymer Poly is selected from 35% to 55%.

[0295] In some embodiments, the mass percentage of fluorine in the polymer Poly is selected from 30% to 50%.

[0296] The mass percentage of fluorine in the polymer Poly can also be selected from any one of the following percentages or a range of any two percentages: 30%, 35%, 40%, 45%, 50%, 55%. Non-limiting examples of a range of any two percentages include 30% to 50%.

[0297] By controlling one or more of the following methods—the fluorine substitution rate in Rf, the number of fluorine atoms in Rf, and the mass percentage of fluorine in the polymer Poly—the uniform deposition of lithium ions can be optimally regulated, lithium dendrite formation can be suppressed, lithium-ion cycle life can be improved, short-circuit risk can be reduced, and the volume expansion on the lithium anode side can be alleviated. Taking the control of the mass percentage of fluorine in the polymer Poly as an example, it is beneficial to improve the lithium dendrite deposition morphology and alleviate the volume expansion of the lithium anode in lithium metal batteries at a certain charging current density.

[0298] In some embodiments, each occurrence of Rf contains 2 to 10 main chain carbon atoms.

[0299] In some embodiments, Rf contains 3 to 10 main-chain carbon atoms.

[0300] In some embodiments, Rf contains 3 to 8 main chain carbon atoms.

[0301] In some embodiments, Rf contains 3, 4, 5, 6, 7 or 8 main-chain carbon atoms.

[0302] In some embodiments, each time Rf appears, the number of carbon atoms in Rf is an integer selected from 2 to 10.

[0303] In some embodiments, the number of carbon atoms in Rf is an integer selected from 3 to 10.

[0304] In some embodiments, the number of carbon atoms in Rf is an integer selected from 3 to 8.

[0305] In some embodiments, the number of carbon atoms in Rf is 3, 4, 5, 6, 7, or 8.

[0306] In some embodiments, Rf is a fluorine-substituted C, depending on the number of carbon atoms in Rf. 2-10 Aliphatic groups, the number of carbon atoms can be selected from any of the following values ​​or any range of two values, such as 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0307] In some embodiments, Rf is a fluorine-substituted C 2-10 Hydrocarbon group. C 2-10 The hydrocarbon group can be, but is not limited to, C. 2-10 Alkyl, C 2-10 alkenyl, C 2-10 Alkyne groups, etc.

[0308] In some embodiments, Rf is a fluorine-substituted C 2-10 Alkyl group. The number of carbon atoms can be selected from any of the following values ​​or a range of any two values, such as 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0309] In some embodiments, C 2-10 The alkyl group can be, but is not limited to, for example, 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-trimethylpentyl, 2,2,4-trimethylpentyl, 2,3,3-trimethylpentyl, 2,3,4-trimethylpentyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, 2,2,3,3-tetramethylbutyl, nonyl, decyl, etc.

[0310] In some embodiments, Rf is a fluorine-substituted C 2-10 Alkenyl. The number of carbon atoms can be selected from any of the following values ​​or a range of any two values, such as 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0311] In some embodiments, C 2-10The alkenyl group can be, but is not limited to, vinyl, propenyl, butenyl, butadienyl, pentenyl, pentadienyl, hexenyl, etc.

[0312] In some embodiments, Rf is a fluorine-substituted C 2-10 Alkyne group. The number of carbon atoms can be selected from any of the following values ​​or a range of any two values, such as 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0313] In some embodiments, C 2-10 The alkynyl group can be, but is not limited to, for example, ethynyl, propynyl, butynyl, butyynyl, pentynyl, pentyynyl, hexynyl, etc.

[0314] By controlling the main chain carbon atoms in Rf, the length of the Rf side groups can be further adjusted by controlling the number of carbon atoms in Rf, thereby giving the polymer layer suitable elasticity and better preventing the polymer layer from cracking under large volume deformation.

[0315] In some embodiments, each occurrence of Rf further contains one or more heteroatoms selected from the group consisting of iodine, nitrogen, oxygen, sulfur, silicon, boron, and phosphorus.

[0316] In some embodiments, each time Rf appears, the number of any one of the heteroatoms in Rf is one or more.

[0317] In some embodiments, the number of any one of the heteroatoms in Rf is selected from 1 to 5.

[0318] In some embodiments, the number of any one of the heteroatoms in Rf is selected from 1, 2, 3 or 4.

[0319] In some embodiments, each occurrence of Rf satisfies one or more of the following:

[0320] The number of oxygen atoms in Rf is 1, 2, 3, 4 or 5;

[0321] The number of nitrogen atoms in Rf is 1, 2, or 3;

[0322] The number of sulfur atoms in Rf is 1, 2, or 3;

[0323] The number of phosphorus atoms in Rf is 1 or 2;

[0324] The number of iodine atoms in Rf is 1, 2, 3, 4, 5 or 6;

[0325] The number of silicon atoms in Rf is 1 or 2; and

[0326] The number of boron atoms in Rf is 1 or 2.

[0327] In some embodiments, the number of oxygen atoms in Rf is 1, 2, 3, 4 or 5.

[0328] In some embodiments, the number of nitrogen atoms in Rf is 1, 2, or 3.

[0329] In some embodiments, the number of sulfur atoms in Rf is 1, 2, or 3.

[0330] In some embodiments, the number of phosphorus atoms in Rf is 1 or 2.

[0331] In some embodiments, the number of iodine atoms in Rf is 1, 2, 3, 4, 5, or 6.

[0332] In some embodiments, the number of silicon atoms in Rf is 1 or 2.

[0333] In some embodiments, the number of boron atoms in Rf is 1 or 2.

[0334] In some embodiments, each occurrence of Rf contains one or more elements selected from iodine, -NR, etc. 12 Atoms or atomic groups in the group consisting of -, -O-, -S-, -S(O)2-, >Si<, >B-, and >P(=O)-, where R 12 For H or C 1-3 alkyl.

[0335] In some embodiments, R 12 It is H or methyl.

[0336] In some embodiments, R 12 For H.

[0337] In some embodiments, each time Rf appears, Rf contains one or more atoms or groups of atoms selected from the group consisting of -O-, -S(O)2- and -(O=)P(O-)2.

[0338] In some embodiments, Rf contains one or more -O-.

[0339] In some embodiments, Rf contains -S(O)2F.

[0340] In some embodiments, Rf contains -(O=)P(O-)2.

[0341] In this application, the term "atomic group" refers to a group having two or more atoms.

[0342] By introducing heteroatoms other than fluorine atoms into Rf, such as one or more heteroatoms from iodine, nitrogen, oxygen, sulfur, silicon, boron, and phosphorus, special properties can be imparted to the polymer layer. For example, phosphorus has a certain flame-retardant effect. Iodine can also play a role in regulating lithium-ion deposition. Furthermore, sulfonyl fluoride groups have a positive effect on improving the ionic conductivity of the polymer layer.

[0343] In some embodiments, the fluorinated aliphatic group, each time it appears, is independently a straight-chain structure or a branched structure. For example, fluorinated hydrocarbon groups (such as fluorinated C...) 2-10 Hydrocarbon groups), fluorinated alkyl groups (such as fluorinated C4 groups), and fluorinated alkyl groups. 2-10 Alkyl groups), fluorinated alkenyl groups (such as fluorinated C4 groups), and fluorinated alkenyl groups. 2-10 alkenyl), fluorinated alkynyl (such as fluorinated C), 2-10 Each occurrence of the alkynyl group can be a straight-chain structure, a branched structure, or a ring-containing structure, but a straight-chain structure or a branched structure is preferred.

[0344] Linear Rf chains are beneficial for improving the flexibility of polymer materials. Branched Rf chains are beneficial for improving the swelling capacity of electrolyte membranes, thereby increasing ionic conductivity.

[0345] In some embodiments, each occurrence of the fluorine-substituted aliphatic group is independently either a saturated or unsaturated structure.

[0346] In some embodiments, the fluorine-substituted aliphatic group contains one or more unsaturated bonds selected from the group consisting of carbon-carbon double bonds and carbon-carbon triple bonds.

[0347] In some embodiments, Rf is a fluorine-substituted C 2-10 Alkenyl group. See the definition above.

[0348] In some embodiments, Rf is a fluorine-substituted C 2-10 Alkyne group. See the definition above.

[0349] When fluorine-substituted aliphatic groups have saturated structures, they can impart better flexibility to the polymer Poly molecular chains, which is beneficial for improving the elasticity control of polymer layers. Introducing a ring with a certain degree of rigidity into Rf allows for more flexible control of the molecular chain elasticity by adjusting the ratio of soft to hard segments. In addition, introducing some unsaturated bonds into Rf can prepare a polymer protective layer with a highly cross-linked structure, which is beneficial for improving the elastic modulus of the material.

[0350] In some embodiments, each time Rf appears, the structure of Rf is independently shown as in Equation III-1, Equation III-2, or Equation III-3:

[0351]

[0352] Among them, R 31 R 32 and R 3 Each occurrence is independently H or F; each occurrence of m3 is independently an integer selected from 2 to 10; Formula III-1 contains at least 4 F atoms;

[0353] Preferably, m3 is an integer selected from 3 to 10 (e.g., 3, 4, 5, 6, 7, 8, 9 or 10);

[0354] Preferably, m3 is an integer selected from 3 to 8;

[0355] Alternatively, m3 is 3, 4, 5, 6, 7, or 8;

[0356] R 41a R 42a R 4a R 41b R 42b and R 4b Each occurrence is independently either H or F; m 4a and m4 4b Each occurrence is an independent integer selected from 1 to 9; Formula III-2 contains at least 4 F atoms;

[0357] Preferably, m 4a and m4 4b Each is an integer selected from 2 to 9 (e.g., 2, 3, 4, 5, 6, 7, 8, or 9);

[0358] Alternatively, m 4a and m4 4b Each is an integer selected independently from 2 to 8;

[0359] Alternatively, m 4a and m4 4b Each is an integer selected independently from 3 to 8;

[0360] Alternatively, m 4a and m4 4b Each is an integer selected independently from 3 to 6;

[0361] R 51 and R 52 Each occurrence is independently H or F; each occurrence of m5 is independently an integer selected from 2 to 10; Formula III-3 contains at least 4 F atoms;

[0362] Preferably, m5 is an integer selected from 3 to 10 (e.g., 3, 4, 5, 6, 7, 8, 9 or 10);

[0363] Preferably, m5 is an integer selected from 3 to 8;

[0364] Alternatively, m5 can be 3, 4, 5, 6, 7 or 8.

[0365] In some embodiments, R 31 R 32 and R 3 Each occurrence is marked as F.

[0366] In some embodiments, each occurrence of m3 is independently an integer selected from 2 to 10.

[0367] In some embodiments, m3 is an integer selected from 3 to 10 (such as 3, 4, 5, 6, 7, 8, 9 or 10).

[0368] In some embodiments, m3 is an integer selected from 3 to 8.

[0369] In some embodiments, m3 is 3, 4, 5, 6, 7, or 8.

[0370] In some embodiments, R 41a R 42a R 4a R 41b R 42b and R 4b Each occurrence is marked as F.

[0371] In some embodiments, m 4a and m4 4b Each is an integer selected independently from 2 to 9 (such as 2, 3, 4, 5, 6, 7, 8 or 9).

[0372] In some embodiments, m 4a and m4 4b Each is an integer selected independently from 2 to 8.

[0373] In some embodiments, m 4a and m4 4b Each is an integer selected independently from 3 to 8.

[0374] In some embodiments, m 4a and m4 4b Each is an integer selected independently from 3 to 6.

[0375] In some embodiments, R 51 and R 52 Each occurrence is marked as F.

[0376] In some embodiments, m5 is an integer selected from 3 to 10 (such as 3, 4, 5, 6, 7, 8, 9 or 10).

[0377] In some embodiments, m5 is an integer selected from 3 to 8.

[0378] In some embodiments, m5 is 3, 4, 5, 6, 7, or 8.

[0379] In some embodiments, each time Rf appears, the structure of Rf is as shown in Equation III-1.

[0380] In some embodiments, each time Rf appears, the structure of Rf is as shown in Equation III-2.

[0381] In some embodiments, each time Rf appears, the structure of Rf is as shown in Equation III-3.

[0382] 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 and prevent the polymer layer from cracking under large volume deformation. On the other hand, it can effectively regulate the uniform deposition of lithium ions through fluorine elements, suppress the formation of lithium dendrites, and alleviate the volume expansion on the lithium anode side.

[0383] The structure of Formula III-2 can incorporate phosphorus elements. In addition, the phosphate ester groups therein have a flame-retardant effect, which helps to improve the safety performance of the battery cell.

[0384] The structure of formula III-3 can incorporate sulfonyl fluoride groups. This has a positive effect on improving the ionic conductivity of the polymer layer.

[0385] In some embodiments, each occurrence of Formula III-1 contains 0, 1, 2, 3, or 4 H atoms.

[0386] In some embodiments, each time Formula III-1 appears, the number of H atoms is 0.

[0387] In some embodiments, each occurrence of Formula III-2 contains 0, 1, 2, 3, 4, 5, or 6 H atoms.

[0388] In some embodiments, each occurrence of Formula III-2 contains 0 H atoms.

[0389] In some embodiments, each occurrence of Formula III-3 contains 0, 1, 2, 3, or 4 H atoms.

[0390] In some embodiments, each occurrence of Formula III-3 contains 0 H atoms.

[0391] By controlling the number of H atoms, the number of sites available for fluorine substitution can be regulated.

[0392] In some embodiments, each occurrence of Rf is independently selected from any of the following structures:

[0393]

[0394] In some embodiments, each occurrence of X is independently H or an electron-withdrawing group containing 1 to 6 non-hydrogen atoms. The number of non-hydrogen atoms can be selected from any one or any two of the following ranges: 1, 2, 3, 4, 5, 6.

[0395] In some embodiments, each occurrence of X is 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.

[0396] In some embodiments, R 21 and R 22 Each can be either H or methyl.

[0397] In some embodiments, R 21 and R 22 All are methyl groups.

[0398] Introducing electron-withdrawing groups (such as cyano groups) at the X position can enhance the reactivity of carbon-carbon double bonds in cyanoacrylate derivative monomers during polymer layer formation, thereby promoting in-situ polymerization.

[0399] In some embodiments, each occurrence of Z is independently O, S, or NH.

[0400] In some embodiments, Z is independently either O or NH each time it appears.

[0401] In some embodiments, Z is always 0 each time it appears.

[0402] In some embodiments, Z is always represented by NH.

[0403] The linker Z can form reactive functional group pairs with different reactive functional groups through coupling reactions, such as -COOH from cyanoacrylate derivative monomers or their derivative reactive forms (e.g., acyl chloride forms, N-succinimide ester activated forms of carboxyl groups). These pairs then generate different types of chemical bonds through coupling reactions. For example, when Z is O, S, or NH, it can be obtained through coupling reactions between -COOH from cyanoacrylate derivative monomers or their derivative reactive forms and -OH, -SH, or -NH2. The diversity of Z is a result of the flexible combination of reactive monomers.

[0404] In some implementations, Rf in Formula I is always the same; X in Formula I always appears the same; Z in Formula I always appears the same. In this case, a single type of monomer (Formula (II)) can be used for polymerization.

[0405]

[0406] In some embodiments, the general formula structure of polymer Poly can be selected from the structures formed by polymerizing any of the monomer polymers in Table 1. The molecular weight can be the same as or different from the polymers corresponding to those in Table 1.

[0407] The monomers corresponding to Example 1 in Table 1 For example, the structure formed by polymerization is: In formula I, X is H, Z is O, and Rf is...

[0408] In some embodiments, in formula I, X is -N(CH3)2, Z is O, and Rf is...

[0409] In some embodiments, in Formula I, X is -NO2, Z is O, and Rf is...

[0410] In some embodiments, in Equation I, X is H, Z is O, and Rf is...

[0411] In some embodiments, in Equation I, X is H, Z is O, and Rf is...

[0412] In some embodiments, in Equation I, X is H, Z is O, and Rf is...

[0413] In some embodiments, in formula I, X is H, Z is NH, and Rf is

[0414] In some embodiments, in Equation I, X is H, Z is O, and Rf is...

[0415] In some embodiments, n is an integer selected from 10 to 1000, preferably an integer selected from 10 to 950, preferably an integer selected from 10 to 800, preferably an integer selected from 15 to 800, preferably an integer selected from 20 to 800, preferably an integer selected from 40 to 800, preferably an integer selected from 50 to 800, preferably an integer selected from 100 to 800, preferably an integer selected from 10 to 750, preferably an integer selected from 15 to 750, preferably an integer selected from 20 to 750, and preferably an integer selected from... The integer is 40 to 750, preferably 50 to 750, preferably 80 to 750, preferably 100 to 750, preferably 10 to 650, preferably 15 to 650, preferably 20 to 650, preferably 40 to 650, preferably 50 to 650, preferably 100 to 650, preferably 150 to 500, and preferably 200 to 350.

[0416] In some embodiments, n can be selected from any one of the following values ​​or an interval consisting of any two of the following values: 10, 20, 30, 40, 50, 60, 70, 80, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 850, 900, 950, 1000, etc.

[0417] In some embodiments, the number-average molecular weight of the polymer Poly is selected from 10 kDa to 200 kDa.

[0418] In some embodiments, the number-average molecular weight of the polymer Poly is selected from 50 kDa to 100 kDa.

[0419] In some embodiments, the number-average molecular weight of the polymer Poly can be selected from any one of the following molecular weights or a range consisting of any two molecular weights (in kDa): 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.

[0420] In Equation I, n is numerically equal to the degree of polymerization of the polymer Poly. By controlling n, the molecular weight of the polymer Poly can be adjusted. By adjusting the degree of polymerization or molecular weight, the molecular chain length of the polymer Poly can be adjusted, achieving effective coating of lithium-containing metals, maintaining stable chemical bonds, and influencing the density and uniformity of the polymer layer.

[0421] In some embodiments, the amount of lithium in the lithium-containing metal relative to the polymer Poly is greater than the amount of catalyst, in molar ratio.

[0422] In this coating composition, as long as the lithium metal can provide the catalyst amount, it can smoothly catalyze the in-situ polymerization reaction of cyanoacrylate derivative monomers on the lithium metal surface.

[0423] In some embodiments, the lithium-containing metal comprises lithium metal or a lithium alloy.

[0424] 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 for lithium-based batteries, making it a superior anode material for lithium metal batteries and contributing to the achievement of high energy density.

[0425] In some embodiments, the lithium alloy contains lithium, and also contains one or more of the following: silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, titanium, etc.

[0426] Secondly, this application provides a negative electrode sheet, wherein the negative electrode sheet includes a negative electrode sheet substrate and a polymer layer stacked together; the negative electrode sheet substrate includes a lithium-containing layer in contact with the polymer layer, the lithium-containing layer contains lithium, and the polymer layer is chemically bonded to at least a portion of the lithium in the lithium-containing layer;

[0427] The polymer layer comprises the polymer Poly as defined in the first aspect of this application.

[0428] In this application, the "negative electrode substrate" provides a negative electrode active material for lithium metal batteries. The negative electrode 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 as the outermost layer of the negative electrode substrate, in other words, the outermost layer on at least one side of the negative electrode substrate is a lithium-containing layer. In one embodiment, the negative electrode substrate consists of a single lithium-containing layer. The polymer layer is chemically bonded to at least a portion of the lithium in the lithium-containing layer; further, "chemically bonded" here refers to covalent bonding. The thickness of the negative electrode substrate can be the thickness of a typical lithium anode in a lithium metal battery. Here, "lithium anode" refers to the thickness of the negative electrode active material layer provided by lithium metal or lithium alloy. Examples of non-limiting thicknesses for the lithium-containing layer include 5 μm to 40 μm. The thickness of the lithium-containing layer can also be selected from any of the following thicknesses or any range of two thicknesses: 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, etc.

[0429] 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, 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: firstly, it can catalyze the in-situ polymerization reaction of cyanoacrylate derivative monomers; secondly, it can form stable covalent bonds with the cyano groups carried by the polymer; and thirdly, it can 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 provides sufficient catalyst to support the in-situ polymerization reaction of cyanoacrylate derivative monomers; for example, it can be the thickness of a typical lithium anode in a lithium metal battery. When the lithium-containing layer is thin, a second negative electrode active material layer can be disposed on the side of the lithium-containing layer away from the polymer layer. In this case, the negative electrode substrate includes both 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.

[0430] The lithium-containing layer on at least one side of the negative electrode sheet has a dense and uniform polymer layer, which can act as a protective layer at the negative electrode of the lithium metal battery. This can effectively suppress the contact reaction between the electrolyte and lithium, reduce the consumption of electrolyte and lithium, improve coulombic efficiency, and extend cycle life.

[0431] In some embodiments, the amount of lithium in the lithium-containing layer relative to the polymer (Poly) is greater than the amount of catalyst, in molar ratio. Typically, the negative electrode needs to provide sufficient lithium (much greater than the amount of catalyst) to significantly improve the energy density of the cell, while also ensuring the initial coulombic efficiency of the negative electrode and reducing or avoiding lithium consumption of the positive electrode.

[0432] In some embodiments, the lithium-containing layer comprises lithium metal or a lithium alloy.

[0433] In some embodiments, the lithium alloy contains lithium and one or more of silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium.

[0434] In some embodiments, the polymer layer further contains an electrolyte. This is advantageous for providing better ionic conductivity.

[0435] In some embodiments, the electrolyte contains a lithium salt and an electrolyte solvent.

[0436] In some embodiments, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), tetrafluoroboric acid (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorooxalate borate (LiDFOB), lithium perchlorate (LiClO4), and lithium dioxoborate (LiBOB).

[0437] In some embodiments, the electrolyte solvent is selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dipropyl carbonate (DPC), diphenyl carbonate (DPhC), dibutyl carbonate (DBC), butylene carbonate (BC), diethylene 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 ether-6.

[0438] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 10 mol / L.

[0439] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 8 mol / L.

[0440] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 5 mol / L.

[0441] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 5 mol / L to 10 mol / L.

[0442] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 3 mol / L.

[0443] In some embodiments, the concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 2 mol / L.

[0444] In some embodiments, the concentration of the lithium salt in the electrolyte can be selected from any one of the following values ​​or a range of any two values ​​(in mol / L): 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 9.5, 10, etc.

[0445] The concentration of lithium salts in the electrolyte also affects the deposition morphology of lithium ions. The lithium salt concentration alters the Li ion deposition morphology in the electrolyte. + The solvation effect of lithium salts influences the composition of the solid electrolyte interphase (SEI) membrane and the deposition morphology of lithium ions. By controlling the lithium salt concentration in the electrolyte to an appropriate level, dense and uniform lithium ion deposition with minimal volume expansion can be achieved. Furthermore, controlling the lithium salt concentration in the electrolyte also ensures suitable mechanical properties of the polymer layer, avoiding the negative mechanical properties caused by excessively high lithium salt concentrations. It also enables better lithium ion conductivity during charge and discharge, preventing poor lithium ion conductivity due to insufficient lithium salt concentration.

[0446] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 199:1 to 1:1. Here, "199:1 to 1:1" and (199 to 1):1 have the same meaning and can be used interchangeably.

[0447] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 19:1 to 1:1.

[0448] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 9.5:1 to 1:1.

[0449] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 8:1 to 2:1.

[0450] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 6:1 to 1:1.

[0451] In some embodiments, the mass ratio of polymer (Poly) to electrolyte can also be 49:1, 39:1, 19:1, 9.5:1, 9:1, 8.5:1, 8:1, 7.5:1, 7:1, 6.5:1, 6:1, 5.5:1, 5:1, 4.5:1, 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, etc. It can also be selected from any range of two of the above ratios, such as (9–2):1.

[0452] In some embodiments, the electrolyte comprises, by mass, 0.5% to 50% of the polymer layer.

[0453] In some embodiments, the electrolyte comprises, by mass, 1% to 50% of the polymer layer.

[0454] In some embodiments, the electrolyte comprises, by mass, 2% to 50% of the polymer layer.

[0455] In some embodiments, the electrolyte comprises, by mass, 5% to 50% of the polymer layer.

[0456] In some embodiments, the electrolyte comprises, by mass, 8% to 50% of the polymer layer.

[0457] In some embodiments, the electrolyte comprises, by mass, 9% to 50% of the polymer layer.

[0458] In some embodiments, the electrolyte comprises, by mass, 9.5% to 50% of the polymer layer.

[0459] In some embodiments, the electrolyte comprises 10% to 50% by mass in the polymer layer.

[0460] In some embodiments, the electrolyte comprises 30% to 50% by mass in the polymer layer.

[0461] In some embodiments, the mass percentage of the electrolyte in the polymer layer can be selected from any one percentage or a range of any two percentages: 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 14%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. Non-limiting examples of any two percentage ranges include 9% to 55%, 9.5% to 50%, etc.

[0462] The mass ratio of polymer (Poly) to electrolyte within a suitable range can be adjusted to control the electrolyte's mass percentage in the polymer layer. The electrolyte's mass percentage in the polymer layer affects the elasticity and ionic conductivity of the protective layer. The presence of a certain amount of lithium salt and solvent plasticizes the polymer layer, improving its elasticity. Furthermore, during the in-situ polymerization process, lithium salt and solvent are incorporated into the polymer layer, resulting in a microscopic, sponge-like, porous structure with pores filled by the electrolyte, providing pathways for subsequent lithium ion transport.

[0463] In some embodiments, the thickness of the polymer layer is selected from 5 nm to 10 μm.

[0464] In some embodiments, the thickness of the polymer layer is selected from 50 nm to 8 μm.

[0465] In some embodiments, the thickness of the polymer layer is selected from 50 nm to 5 μm.

[0466] In some embodiments, the thickness of the polymer layer is selected from 100 nm to 5 μm.

[0467] In some embodiments, the thickness of the polymer layer may be selected from any one or 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.

[0468] The polymer layer structure on the lithium-containing metal surface can be controlled at the nanoscale, which is beneficial for the assembled battery cell to exhibit a smaller interfacial impedance.

[0469] In some embodiments, the elastic modulus of the polymer layer is 0.1 MPa to 80 MPa.

[0470] In some embodiments, the elastic modulus of the polymer layer is 0.5 MPa to 50 MPa.

[0471] In some embodiments, the elastic modulus of the polymer layer is 1 MPa to 50 MPa.

[0472] In some embodiments, the elastic modulus of the polymer layer is 10 MPa to 50 MPa.

[0473] In some embodiments, the elastic modulus of the polymer layer may be selected from any one of the following values ​​or a range consisting of 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, 30 MPa, 35 MPa, 40 MPa, 45 MPa, 50 MPa, 60 MPa, 65 MPa, 70 MPa, 75 MPa, 80 MPa, etc.

[0474] In this application, the term "elastic modulus of polymer layer" generally refers to the test value under conditions of 20°C to 30°C, unless otherwise specified.

[0475] In some embodiments, the elastic modulus of the polymer layer refers to the elastic modulus at 25°C.

[0476] In some embodiments, the elastic deformation range of the polymer layer is 20% to 500%.

[0477] In some embodiments, the elastic deformation range of the polymer layer is 20% to 300%.

[0478] In some embodiments, the elastic deformation range of the polymer layer is 20% to 200%.

[0479] In some embodiments, the elastic deformation range of the polymer layer is 100% to 300%.

[0480] In some embodiments, the elastic deformation range of the polymer layer is 100% to 200%.

[0481] In some embodiments, the elastic deformation range of the polymer layer is 100% to 190%.

[0482] In some embodiments, the elastic deformation range of the polymer layer may be selected from any one or any two of the following percentages: 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 90%, 100%, 150%, 200%, 220%, 240%, 250%, 260%, 280%, 300%, 350%, 400%, 450%, 500%, etc.

[0483] In this application, the term "elastic deformation range of polymer layer" generally refers to the test value under conditions of 20℃ to 30℃ unless otherwise specified.

[0484] In some embodiments, the elastic deformation range of the polymer layer refers to the elastic deformation range at 25°C.

[0485] In some embodiments, based on the electrolyte, the swelling rate of the polymer layer at 25°C is selected from 5% to 50%.

[0486] In some embodiments, the swelling ratio of the polymer layer is selected from 10% to 50%.

[0487] In some embodiments, the swelling ratio of the polymer layer is selected from 10% to 45%.

[0488] In some embodiments, the swelling ratio of the polymer layer is selected from 20% to 45%.

[0489] In some embodiments, based on the electrolyte, the swelling rate of the polymer layer can be selected from any one percentage or a range of any two percentages: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 14%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0490] In this application, the term "swelling rate of polymer layer" generally refers to the test value under conditions of 20℃ to 30℃ unless otherwise specified.

[0491] In some embodiments, the swelling rate of the polymer layer refers to the swelling rate at 25°C. See the test methods in the "Structure and Performance Testing" section of the Examples section below.

[0492] In some embodiments, based on the electrolyte, the ionic conductivity of the swollen polymer layer is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -6 S / cm.

[0493] In some embodiments, the ionic conductivity of the swollen polymer layer is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -5 S / cm.

[0494] In some embodiments, the ionic conductivity of the swollen polymer layer is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -4 S / cm.

[0495] In some embodiments, the ionic conductivity of the swollen polymer layer is selected from 3 × 10⁻⁶. -3 S / cm to 1×10 -4 S / cm.

[0496] In some embodiments, the ionic conductivity of the swollen polymer layer is selected from 3 × 10⁻⁶. -3 S / cm up to 5×10 -4 S / cm.

[0497] In some embodiments, based on the electrolyte, the ionic conductivity of the swollen polymer layer can be selected from any one of the following values ​​or a range consisting of any two of them: 5 × 10 -3 S / cm, 4.5×10 -3 S / cm, 4×10 -3 S / cm, 3.5×10 -3 S / cm, 3×10 -3 S / cm, 2.5×10 -3 S / cm, 2×10 -3 S / cm, 1.5×10 -3 S / cm, 1×10 -3 S / cm, 9×10 -4 S / cm, 8×10 - 4 S / cm, 7×10 -4 S / cm, 6×10 -4 S / cm, 5×10 -4 S / cm, 4×10 -4 S / cm, 3×10 -4 S / cm, 2×10 -4 S / cm, 1×10 -4 S / cm, 9×10 -5 S / cm, 8×10 -5 S / cm, 7×10 -5 S / cm, 6×10 -5 S / cm, 5×10 -5 S / cm, 4×10 -5 S / cm, 3×10 -5 S / cm, 2×10 -5 S / cm, 1×10 -5 S / cm, etc.

[0498] In this application, the term "ionic conductivity of the swollen polymer layer" generally refers to the test value under conditions of 20°C to 30°C unless otherwise specified.

[0499] In some embodiments, the ionic conductivity of the swollen polymer layer refers to the ionic conductivity at 25°C.

[0500] In some embodiments, the volume expansion rate of the negative electrode is selected from 7% to 96%. The volume expansion rate of the negative electrode may also be selected from any one percentage or any range of two percentages: 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%, 95%, etc.

[0501] In this application, the term "volume expansion rate of the electrode" generally refers to the test value under conditions of 20℃ to 30℃ unless otherwise specified.

[0502] In some embodiments, the volume expansion rate of the electrode refers to the volume expansion rate at 25°C.

[0503] In some embodiments, the negative electrode substrate further includes a negative electrode current collector; the negative electrode current collector is located on the side of the lithium-containing layer away from the polymer layer.

[0504] In some embodiments, the negative electrode current collector is located between the negative electrode current collector and the lithium-containing layer, and a second negative electrode active material layer may or may not be provided. Further, the composition of the second negative electrode active material layer and the lithium-containing layer may be the same or different.

[0505] In some embodiments, a lithium-containing layer is provided only on the outermost layer of one side of the negative electrode substrate (see reference). Figure 1 , Figure 2 and Figure 3 ).

[0506] In some embodiments, a lithium-containing layer is provided on the outermost layer of both sides of the negative electrode substrate (see reference). 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 layers can be referred to the aforementioned definition. The lithium content in the second negative electrode active material can be selected from the lithium content in the negative electrode active material layer of a typical 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.

[0507] In this application, the "second negative electrode active material layer" can be any suitable negative electrode active material layer from the reported active material layers of lithium metal batteries. The second negative electrode active material layer can be composed essentially of lithium (Li) metal, or it can be a lithium alloy, or it can be a composition essentially composed of lithium metal and a lithium alloy.

[0508] In some embodiments, a lithium-containing layer is provided on the outermost layer of both sides of the negative electrode substrate, and a polymer layer is provided on the surface of both lithium-containing layers (see reference). Figure 4 and Figure 5The chemical composition and content of the polymer layers on both sides can be the same or different.

[0509] In some embodiments, the negative electrode includes having Figure 1 The structure shown includes a lithium-containing layer 130 and a polymer layer 200 stacked together. The lithium-containing layer contains lithium, a lithium alloy, or a combination of both, and serves as the negative electrode active material layer. The polymer layer contains a polymer (Poly) carrying a large number of cyano groups, which covalently bond with the lithium in the lithium-containing layer to form stable chemical bonds, thus firmly attaching the polymer layer to the surface of the lithium-containing layer. The polymer (Poly) can be selected from the polymers described in any embodiment of the first aspect. The electrolyte is defined as previously stated.

[0510] In some embodiments, the negative electrode includes having Figure 2 The structure shown includes a negative electrode substrate 100 and a polymer layer 200 stacked together. The negative electrode substrate 100 includes a negative electrode current collector 110 and a lithium-containing layer 130 stacked sequentially. The polymer layer 200 is located on the surface of the lithium-containing layer 130 away from the negative electrode current collector 110. Further, the polymer layer comprises a polymer (Poly) and an electrolyte. The lithium-containing layer contains lithium, a lithium alloy, or a combination of both, and the polymer layer contains a polymer (Poly) carrying a large number of cyano groups. These cyano groups covalently bond with the lithium in the lithium-containing layer, forming a stable chemical bond, thus firmly attaching the polymer layer to the surface of the negative electrode substrate.

[0511] In some embodiments, the negative electrode includes having Figure 3 The structure shown includes a negative electrode substrate 100 and a polymer layer 200 stacked together; the negative electrode substrate 100 includes a negative electrode current collector 110, a second negative electrode active material layer 120 and a lithium-containing layer 130 stacked together in sequence, and the polymer layer is located on the surface of the lithium-containing layer 130 away from the negative electrode current collector 110.

[0512] In some embodiments, the negative electrode includes having Figure 4 The structure shown includes a negative electrode substrate 100 and two polymer layers 200 respectively disposed on both sides of the negative electrode substrate 110. The negative electrode substrate includes a negative current collector 110 and two lithium-containing layers 130 respectively disposed on both sides of the negative current collector 110. The lithium-containing layers 130 on both sides of the negative electrode are directly connected to the corresponding polymer layers 200 (chemically connected 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 lithium-containing layers 130 on both sides can be the same or different.

[0513] In some embodiments, the negative electrode includes having Figure 5The structure shown includes a negative electrode substrate 110 and two polymer layers 200 respectively disposed on both sides of the negative electrode substrate 110. The negative electrode substrate includes a negative current collector 110, two second negative electrode active material layers 120 respectively disposed on both sides of the negative 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 current collector 110. The lithium-containing layers 130 on both sides of the negative electrode are directly connected to the corresponding polymer layers 200 (chemically connected 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.

[0514] Negative electrode sheet

[0515] In some embodiments, the negative electrode typically includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative electrode film layer includes the aforementioned lithium-containing layer and further includes a polymer layer formed on at least one side of the lithium-containing layer away from the interior of the negative electrode film layer. That is, the polymer layer is located on the surface of the lithium-containing layer away from the negative current collector, and the polymer layer is located on the outermost layer of the negative electrode. Further, the polymer layer and the lithium-containing layer are chemically connected through covalent interaction.

[0516] As an example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0517] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0518] In some embodiments, the negative electrode active material in the negative electrode active material layer can be a negative electrode active material known in the art for lithium metal batteries. As an example, the negative electrode active material suitable for this 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 this application can serve as the first negative electrode active material layer, and a second negative electrode active material layer may also 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.

[0519] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one 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).

[0520] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0521] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0522] Thirdly, this application provides an electrode assembly comprising a positive electrode sheet, a separator, and a negative electrode sheet as described in the second aspect of this application, wherein the separator is disposed between the negative electrode sheet and the positive electrode sheet; and the polymer layer is disposed at least on the surface of the negative electrode sheet substrate near the separator.

[0523] The negative electrode in this electrode assembly has a dense and uniform polymer layer formed on the lithium-containing layer surface of at least one side, which can act as a protective layer at the negative electrode of the lithium metal battery, effectively suppressing the contact reaction between the electrolyte and lithium, reducing the consumption of electrolyte and lithium, improving coulombic efficiency, and extending cycle life.

[0524] In some embodiments, a lithium-containing layer is provided on the outermost layer of one side of the negative electrode substrate.

[0525] In some embodiments, a lithium-containing layer is provided on the outermost layer of both sides of the negative electrode substrate. The lithium-containing layers on both sides may contain the same or different amounts of lithium.

[0526] In some embodiments, a lithium-containing layer is provided on the outermost layer on both sides of the negative electrode substrate, and a polymer layer is provided on the surface of the lithium-containing layer on both sides. The chemical composition and content of the polymer layers on both sides may be the same or different.

[0527] Fourthly, this application provides a secondary battery, which includes a cell electrolyte and the electrode assembly described in the third aspect of this application, wherein the cell electrolyte is disposed between the polymer layer and the positive electrode sheet.

[0528] The negative electrode sheet in this secondary battery has a dense and uniform polymer layer formed on the lithium-containing layer surface on at least one side, which can act as a protective layer at the negative electrode of the lithium metal battery, effectively suppressing the contact reaction between the electrolyte and lithium, reducing the consumption of electrolyte and lithium, improving coulombic efficiency, and extending cycle life.

[0529] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0530] Positive electrode sheet

[0531] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0532] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0533] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0534] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0535] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0536] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0537] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0538] Battery cell electrolyte

[0539] The electrolyte in the battery cell plays a role in conducting ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte in the battery cell, and it can be selected according to requirements. For example, the electrolyte in the battery cell can be liquid, gel, or all-solid.

[0540] In some embodiments, the electrolyte of the battery cell is a second electrolyte. The second electrolyte comprises an electrolyte salt and a solvent. The composition of this electrolyte may be the same as or different from that of the electrolyte in the polymer layer.

[0541] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0542] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0543] In some embodiments, the electrolyte in the battery cell may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0544] Separating membrane

[0545] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0546] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven 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.

[0547] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0548] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and the cell electrolyte.

[0549] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0550] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 This is an example of a square-structured secondary battery 5.

[0551] In some implementations, refer to Figure 7 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0552] In some embodiments, the composition of the electrolyte in the battery cell and the electrolyte in the polymer layer may be the same or different.

[0553] When the electrolyte in the cell of a secondary battery has the same composition as the electrolyte in the polymer layer, the consistency of lithium-ion transport within the cell can be maintained, reducing interference from multiple factors such as electrolyte solvation and interfacial side reactions.

[0554] When the electrolyte composition of the cell in a secondary battery differs from that of the electrolyte in the polymer layer, the formation of a stable SEI can be directionally induced on the lithium-containing layer side, thereby regulating the deposition morphology of lithium ions.

[0555] In some embodiments, the charging current density of the secondary battery is selected from 0.3 mA / cm². 2 ~12mA / cm 2 .

[0556] In some embodiments, the charging current density of the secondary battery is selected from 1 mA / cm². 2 ~10mA / cm 2 .

[0557] In some embodiments, the charging current density of the secondary battery is selected from 1 mA / cm². 2 ~6mA / cm 2 .

[0558] In some embodiments, the charging current density of the secondary battery can be selected from any one of the following values ​​or a range consisting of any two of the following values: 0.3 mA / cm² 2 0.4mA / cm 2 0.5mA / cm 2 0.6mA / cm 2 0.7mA / cm 2 0.8mA / 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 5mA / cm 2 5.5mA / cm 2 6mA / cm 2 7mA / cm 2 8mA / cm 2 9mA / cm 2 10mA / cm 2 11mA / cm 2 12mA / cm 2 wait.

[0559] In some embodiments, the applicable charging current density may also be 0.3 mA / cm². 2 ~0.5mA / cm2 0.5mA / cm 2 ~1mA / cm 2 1mA / cm 2 ~1.5mA / cm 2 1.5mA / cm 2 ~2mA / cm 2 2mA / cm 2 ~2.5mA / cm 2 2.5mA / cm 2 ~3mA / cm 2 3mA / cm 2 ~3.5mA / cm 2 3.5mA / cm 2 ~4mA / cm 2 4mA / cm 2 ~4.5mA / cm 2 4.5mA / cm 2 ~5mA / cm 2 5mA / cm 2 ~5.5mA / cm 2 5.5mA / cm 2 ~6mA / cm 2 6mA / cm 2 ~8mA / cm 2 8mA / cm 2 ~10mA / cm 2 or 10mA / cm 2 ~12mA / cm 2 .

[0560] In some embodiments, the capacity retention of the secondary battery after 50 cycles is selected from 80% to 97%. The capacity after 50 cycles may also be selected from any one percentage or a range of any two percentages: 80%, 81%, 82%, 83%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, etc.

[0561] In this application, the term "capacity retention rate after 50 cycles" of a secondary battery generally refers to the test value under conditions of 20°C to 30°C, unless otherwise specified.

[0562] In some embodiments, the capacity retention rate of a secondary battery after 50 cycles refers to the volume expansion rate at 25°C.

[0563] Fifthly, this application provides a battery module that includes the secondary battery described in the fourth aspect of this application.

[0564] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0565] Figure 8 This is battery module 4, used as an example. (See reference...) Figure 8 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0566] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0567] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0568] Sixthly, this application provides a battery pack that includes the battery module described in the fifth aspect of this application.

[0569] Figure 9 and Figure 10 This is battery pack 1 as an example. (See reference...) Figure 9 and Figure 10 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0570] In a seventh aspect, this application provides an electrical device comprising one or more of the secondary battery described in the fourth aspect of this application, the battery module described in the fifth aspect of this application, and the battery pack described in the sixth aspect of this application.

[0571] The electrical device includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Mobile devices may include, for example, mobile phones, laptops, etc.; electric vehicles may include, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0572] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0573] Figure 11 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0574] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0575] Eighthly, this application provides the use of monomer compound II in the preparation of negative electrode sheets, wherein the structure of monomer compound II is shown in Formula II:

[0576]

[0577] Rf, Z, and X are each independently defined as in the first aspect of this application.

[0578] Non-limiting examples of monomeric compound II are shown in Table 1.

[0579] In some embodiments, the monomer compound II contacts lithium in the lithium-containing layer of the negative electrode substrate and forms a polymer layer through in-situ polymerization.

[0580] The monomer compound II is a cyanoacrylate derivative compound, in which the cyano group can contact the lithium in the outermost layer of the negative electrode substrate to form a chemical bond, and the carbon-carbon double bond can undergo an in-situ polymer reaction under lithium catalysis, thereby preparing the lithium-coated composition described in the first aspect of this application. At this time, a firmly connected, dense and uniform polymer layer is formed on the surface of the lithium-containing layer, which can play the aforementioned protective layer role.

[0581] Ninthly, this application provides a method for preparing a negative electrode sheet, which includes the following steps:

[0582] A negative electrode substrate is provided, wherein the outermost layer of at least one side of the negative electrode substrate is a lithium-containing layer, the lithium-containing layer comprising a lithium-containing metal; a reaction mixture containing monomer compound II and an electrolyte is also provided.

[0583] The reaction mixture is coated onto the lithium-containing layer surface of at least one side of the negative electrode substrate, and the monomer compound II is polymerized in situ to form a polymer layer;

[0584]

[0585] Wherein, Rf, Z and X are each independently as defined in the first aspect of this application;

[0586] The electrolyte is as defined in the second aspect of this application.

[0587] The definition of the negative electrode substrate provided in this aspect is the same as that described above. The negative electrode substrate provided in this aspect includes at least a lithium-containing layer that can contact monomer compound II in order to catalyze the in-situ polymerization reaction.

[0588] In the presence of an electrolyte, the cyano group in monomer compound II can form a chemical bond (covalent bond) with the lithium in the outermost layer of the negative electrode substrate. The carbon-carbon double bond can undergo an in-situ polymer reaction under lithium catalysis to form the polymer Poly shown in Formula I, thereby preparing the lithium-coated composition described in the first aspect of this application. At this point, a firmly bonded, dense, and uniform polymer layer is formed on the surface of the lithium-containing layer, which can perform the aforementioned protective layer function. Compared to the physical coating method in conventional technologies, this method not only stably binds to the surface of the lithium-containing layer through chemical bonding, preventing it from detaching from the lithium-containing layer surface during charging and discharging, but also produces a dense and uniform coating with a thickness that can be controlled at the nanoscale. The assembled battery cell can exhibit a lower interfacial impedance.

[0589] In some embodiments, the negative electrode substrate can be prepared by dispersing the above-mentioned components for preparing the negative electrode, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode substrate after drying, cold pressing and other processes.

[0590] In some embodiments, this application provides that the monomer compound II is contacted with lithium in at least a catalytic amount of the lithium-containing metal. This provides chemical bonding sites for the polymer layer and effectively catalyzes the in-situ polymerization of cyanoacrylate derivative monomers.

[0591] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 199:1 to 1:1.

[0592] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 49:1 to 1:1.

[0593] In some embodiments, the mass ratio of the polymer Poly to the electrolyte is selected from 19:1 to 1:1.

[0594] In some embodiments, the mass ratio of the monomer compound II to the electrolyte is selected from 9.5:1 to 1:1.

[0595] In some embodiments, the mass ratio of the monomer compound II to the electrolyte is selected from 8:1 to 2:1.

[0596] In some embodiments, the mass ratio of the monomer compound II to the electrolyte is selected from 6:1 to 1:1.

[0597] In some embodiments, the mass ratio of the polymer Poly to the electrolyte may be any of the following ratios or a range selected from any two of the following ratios: 49∶1, 19∶1, 9.5∶1, 9∶1, 8∶1, 7∶1, 6∶1, etc.

[0598] By controlling the mass ratio of monomer compound II to electrolyte, the mass ratio of polymer (Poly) to electrolyte in the generated polymer layer can be controlled.

[0599] In some embodiments, in the step of coating the reaction mixture onto the lithium-containing layer surface of at least one side of the negative electrode substrate, the coating method is selected from any one of coating, spraying, spin coating and vapor deposition.

[0600] In some embodiments, the reaction temperature of the in-situ polymerization is selected from 30°C to 100°C.

[0601] In some embodiments, the reaction temperature of the in-situ polymerization is selected from 30°C to 50°C.

[0602] In some embodiments, the reaction temperature of the in-situ polymerization is selected from 40°C to 60°C.

[0603] In some embodiments, the reaction temperature of in-situ polymerization can be selected from any one of the following values ​​or a range consisting of any two of the following values: 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.

[0604] In some embodiments, the reaction time for the in-situ polymerization is selected from 0.1 h to 24 h.

[0605] In some embodiments, the reaction time for the in-situ polymerization is selected from 0.1 h to 12 h.

[0606] In some embodiments, the reaction time for the in-situ polymerization is selected from 0.1 h to 2 h.

[0607] In some embodiments, the reaction time for in-situ polymerization can be selected from any one of the following durations or an interval consisting of any two durations: 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.

[0608] In some embodiments, in the step of coating the reaction mixture onto the lithium-containing layer surface of at least one side of the negative electrode substrate, the coating thickness of the reaction mixture is selected from 100 nm to 8 μm.

[0609] In some embodiments, the coating thickness of the reaction mixture is selected from 50 nm to 5 μm.

[0610] In some embodiments, the coating thickness of the reaction mixture is selected from 50 nm to 8 μm.

[0611] In some embodiments, the coating thickness of the reaction mixture can be selected from any one of the following values ​​or a range of any two of the following values: 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, etc.

[0612] In some embodiments, the polymer layer formed is as defined in the second aspect of this application.

[0613] In some embodiments, the negative electrode substrate is a pure lithium sheet. In this case, an additional negative current collector can be introduced into the battery negative electrode to facilitate the assembly of the tab, or a pure lithium sheet covered with a polymer layer can be used as the negative electrode.

[0614] In some embodiments, the negative electrode substrate further includes a negative electrode current collector; the negative electrode current collector is located on the side of the lithium-containing layer away from the polymer layer.

[0615] In some embodiments, a second negative electrode active material layer may or may not be provided between the negative electrode current collector and the lithium-containing layer, and the composition of the second negative electrode active material layer and the lithium-containing layer may be the same or different.

[0616] In some embodiments, the method of forming a second active material layer or a lithium-containing layer on the negative electrode current collector may be selected from: (1) a method of transferring lithium metal or lithium alloy rolled by rolling onto the negative electrode current collector; (2) a method of evaporating lithium metal or lithium alloy onto the negative electrode current collector, etc.

[0617] In some embodiments, the method of forming a lithium-containing layer on the second active material layer may be selected from: (1) a method of transferring lithium metal or lithium alloy rolled by rolling onto the second active material layer; (2) a method of evaporating lithium metal or lithium alloy onto the second active material layer, etc.

[0618] In a tenth aspect, this application provides a method for preparing a secondary battery, wherein the secondary battery is the secondary battery described in the fourth aspect of this application, and the preparation method includes the following steps: injecting the cell electrolyte into a battery casing containing the electrode assembly described in the third aspect of this application.

[0619] The following describes some embodiments of this application.

[0620] The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed according to the description above, or according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially, or can be synthesized from commercially available products using conventional methods.

[0621] In the following examples, room temperature refers to 20°C to 30°C.

[0622] In the following examples, the monomer-electrolyte mixture is coated using a coating method.

[0623] Preparation of fluorinated monomers (corresponding to monomer compound II)

[0624] The fluorinated monomers used in the following examples can be obtained commercially (e.g., 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate) or prepared by the following methods.

[0625] 1. When X in monomer compound II is H, it can be prepared by the condensation reaction between compound C1 (2-cyanoacrylic acid) and compound C2, which generates a linking group Z. When Z is O, an ester bond (C(=O)-O) is generated by the condensation reaction between the carboxyl group and the hydroxyl group. When Z is NH, an amide bond (C(=O)-NH) is generated by the condensation reaction between the carboxyl group and -NH2.

[0626]

[0627] 2. When X in monomer compound II is not H, taking X as -N(CH3)2 as an example, the method of “Bredereck, Hellmut, et al. Chemische Berichte, 1964, 97(12), 3397-3406” can be referred to. Acrylate compound C5 containing 1-X and 2-cyano groups is prepared by using acetal compound C3 and 2-cyanoacrylate compound C4. The acrylate compound C5 is hydrolyzed to form compound C6, and then condensed with compound C2 to generate the fluorinated monomer shown in formula II.

[0628]

[0629] Whether a product compound has formed can be determined based on at least one of the molecular weight test results and the viscosity test results.

[0630] Example 1. Preparation of a lithium metal anode containing a polymer layer

[0631] (1) At 25°C, 10g of 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate (fluorinated monomer), 0.8g of lithium bis(fluorosulfonyl)imide (LiFSI) and 5g of dimethyl ethylene glycol (DME) were stirred at room temperature to obtain a monomer-electrolyte mixture, as shown in Table 1.

[0632] (2) The obtained monomer-electrolyte mixture is coated onto the surface of a lithium sheet and allowed to stand at 30°C for 2 hours to obtain a lithium sheet containing a transparent and dense polymer layer. The operating parameters are shown in Table 2. The sheet is cut into a circular piece with a diameter of Φ16mm to serve as the negative electrode.

[0633] (3) Preparation of the positive electrode sheet:

[0634] The positive electrode active material LiCO2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 96:2:2. N-methylpyrrolidone (NMP) solvent was added and stirred until the system was homogeneous to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated onto the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. It was then cut into circular pieces with a diameter of Φ14mm to serve as the positive electrode sheet, with a positive electrode surface capacity of 3mAh / cm². 2 .

[0635] (4) Electrolyte preparation:

[0636] Lithium bis(fluorosulfonyl)imide (LiFSI) was slowly added to dimethyl ethylene glycol (DME) to prepare an electrolyte with a LiFSI concentration of 1 mol / L.

[0637] (5) Separation membrane: Polypropylene film is selected.

[0638] (6) Battery fabrication:

[0639] Place the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. Inject the electrolyte prepared in step (4) and assemble it into a button cell.

[0640] Before battery testing, the lithium metal battery was subjected to an input current of 3.0 mA / cm. 2 It is charged to 4.25V with a constant current, and then at 3.0mA / cm 2 Discharge at a constant current to 3.0V.

[0641] Examples 2 to 14 use the same method as Example 1, except that step (1) is different.

[0642] In Examples 2 to 14, the fluorinated monomer, the fluorine substitution rate in Rf of the monomer, the mass content of electrolyte in the monomer-electrolyte mixture, the lithium salt concentration in the electrolyte of step (1), the coating thickness, and the temperature and time of the in-situ polymerization reaction can be found in Tables 1 and 2.

[0643] The steps (1) of Examples 2 to 14 are as follows.

[0644] Examples 2 to 8

[0645] Step (1): At 25°C, mix 10g of fluorinated monomer, 0.8g of lithium salt and 5g of electrolyte solvent evenly, and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0646] Example 9

[0647] Step (1): At 25°C, mix 18g of fluorinated monomer, 0.012g of lithium salt and 0.078g of electrolyte solvent evenly and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0648] Example 10

[0649] Step (1): At 25°C, mix 9g of fluorinated monomer, 1.241g of lithium salt and 7.759g of electrolyte solvent evenly and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0650] Example 11

[0651] Step (1): At 25°C, mix 10g of fluorinated monomer, 0.565g of lithium salt and 5.235g of electrolyte solvent evenly and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0652] Example 12

[0653] Step (1): At 25°C, mix 10g of fluorinated monomer, 3.964g of lithium salt and 1.836g of electrolyte solvent evenly and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0654] Example 13

[0655] Step (1): At 25°C, mix 10g of fluorinated monomer, 0.8g of lithium salt and 5g of electrolyte solvent evenly, and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0656] Example 14

[0657] Step (1): At 25°C, mix 10g of fluorinated monomer, 0.8g of lithium salt and 5g of electrolyte solvent evenly, and stir evenly at room temperature to obtain monomer-electrolyte mixture, see Table 1 for fluorinated monomer.

[0658] Comparative Examples 1 and 2 were conducted using essentially the same methods as in Example 1, with the difference being the different mass content of electrolyte in the monomer-electrolyte mixture, as shown in Tables 1 and 2.

[0659] Comparative Examples 3 and 4 were performed using methods that were essentially the same as those used in Example 1, with the difference being the different lithium salt concentrations in the electrolyte during step (1), as shown in Tables 1 and 2.

[0660] Comparative Examples 5 and 6 were performed using essentially the same methods as in Example 1, the only difference being the coating thickness, as shown in Tables 1 and 2.

[0661] Comparative Example 7 uses essentially the same method as Example 1, except that the structure of monomer compound II is different (the side chain is not substituted with fluorine), see Tables 1 and 2.

[0662] Comparative Example 8: A polymer solution with a molecular weight of 1000 kDa was sprayed onto the surface of a pure lithium sheet and dried to obtain a coated polymer layer, as shown in Tables 1 and 2. The polymer solution was prepared by dissolving 18 g of polymer in 50 mL of solvent. The polymer was a PVdF-HFP (polyvinylidene fluoride-hexafluoropropylene) copolymer with a weight-average molecular weight of 500 kDa, and the solvent was tetrahydrofuran (THF).

[0663] Comparative Example 9 uses pure lithium sheet as the negative electrode, that is, without polymer layer.

[0664] Table 1.

[0665]

[0666]

[0667]

[0668] Table 2.

[0669]

[0670]

[0671] Note 1: The word “approximately” in the average degree of polymerization indicates ±2; the average degree of polymerization corresponds to the average n value of the polymer Poly shown in Formula I in the polymer layer.

[0672] Test sample preparation

[0673] 1. Preparation of polymer layer films

[0674] (1) At 25°C, 30g of 2,2,3,3,4,4,5,5-octafluoropentane-2-cyanoacrylate, 2.4g of lithium bis(fluorosulfonyl)imide (LiFSI) and 15g of dimethyl ethylene glycol (DME) were stirred at room temperature to obtain a homogeneous solution.

[0675] (2) Add 0.48g of lithium powder to the homogeneous solution obtained in step (1), stir quickly and evenly, then coat it onto a glass plate. After standing at 30°C for 2 hours, a transparent polymer layer film with a thickness of 15μm can be obtained.

[0676] Structural and performance testing

[0677] 1. Characterization of polymer components in the polymer layer (lithium metal protective layer)

[0678] Lithium sheets containing polymer layers are immersed in isopropanol. The lithium sheets are corroded and consumed, and the resulting lithium isopropoxide can be dissolved in isopropanol. The polymer is insoluble in isopropanol and will precipitate. After centrifugation and drying, a solid polymer sample can be obtained.

[0679] 1.1. Fourier Transform Infrared Spectroscopy (FT-IR) Test: ATR mode, 4cm -1 Resolution, 32 scans, wavenumber range 4000 cm⁻¹ -1 ~400cm -1 .

[0680] 1.2. 1 H NMR nuclear magnetic resonance test: 1 The H resonance frequency was 400 MHz, the solvent was deuterated dimethyl sulfoxide (DMSO-d6), and tetramethylsilane (TMS) was used as an internal standard.

[0681] 1.3. Molecular weight test: The polymer sample is dissolved in NMP and the molecular weight is tested by gel permeation chromatography (GPC) to obtain the weight average molecular weight, number average molecular weight and polydispersity index (PDI).

[0682] 1.4. Polymer layer thickness test: The thickness of the polymer coating is measured using a laser thickness gauge.

[0683] 1.5. Viscosity Test: The viscosity of the polymer solution was tested using a viscometer. The polymer solution was prepared by dissolving 5g of polymer in 30mL of NMP. The test temperature was 25℃.

[0684] 2. Fluorine content

[0685] The fluorine content in the polymer layer can be determined by X-ray photoelectron spectroscopy (XPS).

[0686] 3. Swelling parameters

[0687] The swelling parameters of the polymer layer were tested using the following method:

[0688] The test temperature was 25℃. Lithium metal sheets containing the polymer layer were cut into 30mm × 30mm square samples, with three parallel samples per group, and the mass of each sample was weighed. Then, the samples were immersed in a 1 mol / L LiFSI DME electrolyte solution for 2 hours to allow swelling. After swelling, the surface of the samples was gently wiped with filter paper to remove residual electrolyte, and the mass of the swollen samples was then weighed. The swelling rate of the polymer layer is the percentage increase in mass of the swollen sample relative to the original sample mass.

[0689] 4. Ionic conductivity

[0690] The test temperature was 25℃. The polymer film was punched into a disc with a diameter of Φ16mm. The disc was immersed in the electrolyte for 1 hour, then removed, and the electrolyte was wiped off the membrane surface with filter paper. The ionic conductivity of the polymer film 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 tested using an electrochemical workstation at a frequency of 10 Hz. -6 ~ 10 -1 Hz, voltage amplitude is 5mV; the intersection of the graph and the horizontal axis is the impedance R of the polymer film.

[0691] 5. Elastic modulus and elastic deformation

[0692] Elastic modulus: The test temperature is 25℃. The polymer film is cut into strips with a length L0 of 150mm and a width of 20mm. The elastic modulus of the polymer film is measured by a universal testing machine with a tensile distance of 100mm and a tensile speed of 50mm / min. The maximum tensile force of the polymer film is the elastic modulus.

[0693] Elastic deformation: The test temperature is 25℃. When the polymer film is stretched, with the length at which the film breaks as L, the elastic deformation of the film can be calculated as (L-L0) / L0×100%.

[0694] 6. Polymer layer bonding performance test (peeling degree)

[0695] The thickness of the polymer layer on the lithium metal surface was controlled to approximately 5 μm by controlling the reaction time. A 50 × 100 mm area was used as the peel test sample. Ten × ten 1 mm × 1 mm grids were drawn on the surface of the protective layer sample using a sharp blade (15°–30°), each line penetrating to the bottom layer of the protective layer. The test area was then cleaned of debris with a brush. An adhesion test with a strength of 350 g / cm² was performed. 2 ~400g / cm 2 Apply 3M 600 tape or equivalent firmly to the test grid and rub the tape vigorously with an eraser to increase the contact area and force between the tape and the test area. Hold one end of the tape and quickly tear it off vertically (90°). Repeat the same test twice at the same location. Finally, observe the grid area with a magnifying glass. If there is no peeling or the peeling occurs within the protective layer, it is acceptable. However, if the peeling occurs between the metal and the protective layer, an area greater than 65% is grade 0B; an area between 35% and 65% is grade 1B; an area between 15% and 35% is grade 2B; an area between 5% and 15% is grade 3B; an area less than or equal to 5% is grade 4B; and if the cut edges are completely smooth and there is no peeling at the grid edges, it is grade 5B.

[0696] 7. Electrode performance testing

[0697] Electrode volume expansion rate: The test temperature was 25℃. The thickness of the fresh lithium sheet was d1. After the battery was cycled 50 times to a fully discharged state, the battery was disassembled, and the thickness of the lithium sheet was measured using an optical microscope to be d2. The electrode expansion rate was (d2-d1) / d1×100%.

[0698] 8. Battery performance testing

[0699] (1) Cyclic Performance Test: The test temperature was 25℃. The lithium metal battery was initially charged to 4.25V with a constant current, and then discharged to 3.0V to obtain the initial discharge specific capacity (Cd1). This charge-discharge cycle was repeated for 50 cycles. The discharge specific capacity of the lithium metal battery after n cycles is denoted as Cdn. Capacity retention rate = discharge specific capacity after n cycles (Cdn) / initial discharge specific capacity (Cd1) × 100%.

[0700] (2) Observation of lithium anode surface: After cycling to the 50th cycle and fully discharged state, the battery was disassembled and the uniformity of lithium deposition / dissolution and the flatness of lithium anode surface were observed under an optical microscope.

[0701] Test Results

[0702] Table 2 shows the results of polymer molecular weight testing, fluorine content in the polymer, and polymer layer thickness testing. Table 3 shows the results of polymer layer swelling rate, ionic conductivity, elastic modulus, and elastic deformation testing, as well as the capacity retention rate, lithium dendrite formation, electrode volume expansion rate, and peeling degree testing of lithium-ion batteries prepared using negative electrode sheets containing the polymer layer of this application after 50 cycles.

[0703] Example 1:

[0704] FTIR: 2853-2962cm -1 CH stretching vibration; 2248cm -1 -CN stretching vibration; 1743cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration.

[0705] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0706] GPC: 60kDa; PDI: 1.4.

[0707] Viscosity (25℃): 3652cp.

[0708] Example 2:

[0709] FTIR: 2890cm-2962cm -1 CH stretching vibration; 2245cm -1 -CN stretching vibration; 1747cm -1 -C=O stretching vibration; 1190cm -1CN stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration.

[0710] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0711] GPC: 100kDa; PDI: 1.5.

[0712] Example 3:

[0713] FTIR: 2856-2960cm -1 CH stretching vibration; 2243cm -1 -CN stretching vibration; 1749cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration.

[0714] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0715] GPC: 20kDa; PDI: 1.2.

[0716] Example 4:

[0717] FTIR: 2853-2962cm -1 CH stretching vibration; 2247cm -1 -CN stretching vibration; 1745cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration.

[0718] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0719] GPC: 70kDa; PDI: 1.3.

[0720] Example 5:

[0721] FTIR: 2853-2962cm -1CH stretching vibration; 2248cm -1 -CN stretching vibration; 1748cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration.

[0722] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0723] GPC: 30kDa; PDI: 1.2.

[0724] Example 6:

[0725] FTIR: 2853-2962cm -1 CH stretching vibration; 2239cm -1 -CN stretching vibration; 1746cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration.

[0726] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0727] GPC: 150kDa; PDI: 1.7.

[0728] Example 7:

[0729] FTIR: 3220-3410cm -1 NH stretching vibration; 2853-2962cm -1 CH stretching vibration; 2231cm -1 -CN stretching vibration; 1673cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration. 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0730] GPC: 50kDa; PDI: 1.5.

[0731] Example 8:

[0732] FTIR: 2853-2962cm -1 CH stretching vibration; 2231cm -1 -CN stretching vibration; 1735cm -1 -C=O stretching vibration; 1100-1300cm -1 -CF stretching vibration; 400-700cm -1 -CF bending vibration; 1396cm -1 -P=O stretching vibration; 741cm -1 -PO stretching vibration.

[0733] 1 HNMR: δ1.3ppm, -CH2-; δ4.3ppm, -CHF2; δ2.6-3.0ppm, main chain -CH2.

[0734] GPC: 70kDa; PDI: 1.4.

[0735] Compared with Comparative Examples 8 and 9, after the polymer layer of this application was included (Examples 1-14, Comparative Examples 3-6), the volume expansion of the lithium anode was significantly suppressed after multiple cycles of the lithium metal battery, which is beneficial for the battery to maintain a good capacity retention rate.

[0736] By controlling the monomer structure in the polymer layer, different fluorine substitution rates and fluorine contents can be achieved. Compared with Comparative Example 7, the introduction of fluorine in Examples 1-14 helps to improve the lithium-ion deposition regulation effect of the protective film, improve dendrite morphology, and reduce volume expansion.

[0737] Comparing Example 7 and Comparative Example 8, it can be seen that when the fluorine-substituted aliphatic group is connected to the polymer backbone through the amide group (Z is NH in Example 7), the polymer protective layer can improve the ionic conductivity of the polymer layer, improve the battery charging current density, capacity retention rate after 50 cycles and volume expansion performance of the secondary battery, and significantly suppress lithium dendrites.

[0738] Comparing Example 8 and Comparative Example 8, it can be seen that when the fluorinated aliphatic group is attached to the polymer backbone via a phosphate ester group (in Example 8, Z is O, and Rf is on the side closer to Z), The polymer protective layer can improve the ionic conductivity of the polymer layer, improve the battery charging current density, capacity retention after 50 cycles and volume expansion performance of the secondary battery, and significantly suppress lithium dendrites.

[0739] Comparing Examples 9-10 and Comparative Examples 1-2, it can be seen that controlling the electrolyte content in the polymer layer can regulate the swelling ratio and mechanical properties of the polymer layer. In Comparative Example 1, although a high electrolyte content is beneficial to improving ionic conductivity, the membrane rigidity is low, which is detrimental to achieving 3 mA / cm². 2 The above high-current charge-discharge processes resulted in severe dendrite formation, significant volume expansion, and rapid capacity decay. In Comparative Example 2, the ionic conductivity decreased, which is unfavorable for achieving 3 mA / cm². 2 The above high-current charging and discharging causes severe dendrite formation, significant volume expansion, and rapid capacity decay.

[0740] Comparing Examples 11-12 and Comparative Examples 3-4, it can be seen that by controlling the lithium salt concentration in the polymer layer, the polymer layer can exhibit different deposition morphologies and expansion rates. Lower lithium salt concentrations result in lower ionic conductivity and lower elastic modulus in the polymer protective layer, which is detrimental to suppressing dendrite formation and volume expansion on the negative electrode side; while higher lithium salt concentrations affect the mechanical strength of the material.

[0741] Comparing Examples 13-14 and Comparative Examples 5-7, it can be seen that the thickness of the polymer layer needs to be controlled within a certain range. If it is too thick, the cell polarization is large, the ionic conductivity is low, and the cycle decay is fast; if it is too thin, the mechanical strength is poor, which is not conducive to suppressing dendrites and uneven lithium deposition.

[0742] In summary, by adjusting the fluorine content, lithium salt concentration, electrolyte content, and thickness of the protective layer, the membrane can achieve higher conductivity and mechanical strength, which is beneficial for its application in lithium metal batteries that undergo charge-discharge cycles at high current densities.

[0743] Table 3.

[0744]

[0745]

[0746] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0747] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. The above-described embodiments only illustrate several embodiments of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this application without departing from the spirit of this application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A lithium coating composition comprising a lithium-containing layer and a polymer layer, wherein the lithium-containing layer contains lithium metal, and the polymer layer comprises a polymer, Poly, wherein, The polymer Poly is chemically bonded to the lithium surface in the lithium-containing metal, and the polymer Poly comprises the structure shown in Formula I. (I) in, Each time Rf appears, it is independently a fluorine-substituted aliphatic group; Each time X appears, it is independently either H or an electron-withdrawing group; Z is, at each occurrence, independently O or NR 11 ; wherein R 11 is H or C 1-3 alkyl; * indicates the site where the terminal base is attached; n is an integer ≥ 10; At least one cyano group in the polymer Poly forms a chemical bond with lithium in the lithium-containing metal.

2. The lithium-coated composition according to claim 1, wherein, The fluorine substitution rate in Rf independently satisfies >50%.

3. The lithium-coated composition according to claim 1, wherein, The fluorine substitution rate in Rf independently satisfies ≥55%.

4. The lithium-coated composition according to claim 1, wherein, The fluorine substitution rate in Rf independently satisfies ≥65%.

5. The lithium-coated composition according to claim 1, wherein, The fluorine substitution rate in Rf independently satisfies ≥70%.

6. The lithium-coated composition according to claim 1, wherein, The fluorine substitution rate in Rf independently satisfies ≥80%.

7. The lithium-coated composition according to claim 1, wherein, The number of fluorine atoms in Rf is an independent integer of ≥4.

8. The lithium-coated composition according to claim 1, wherein, The number of fluorine atoms in Rf is an independent integer from 4 to 20.

9. The lithium-coated composition according to claim 1, wherein, The number of fluorine atoms in Rf is an independent integer from 4 to 16.

10. The lithium-coated composition according to claim 1, wherein, The number of fluorine atoms in Rf is an independent integer from 4 to 15.

11. The lithium-coated composition according to claim 1, wherein, The number of fluorine atoms in Rf is an independent integer from 4 to 13.

12. The lithium-coated composition according to claim 1, wherein, The number of fluorine atoms in Rf is an independent integer from 4 to 10.

13. The lithium-coated composition according to claim 1, wherein, The mass percentage of fluorine in the polymer Poly is selected from 30% to 55%.

14. The lithium-coated composition according to claim 1, wherein, The mass percentage of fluorine in the polymer Poly is selected from 35% to 55%.

15. The lithium-coated composition according to claim 1, wherein, The mass percentage of fluorine in the polymer Poly is selected from 30% to 50%.

16. The lithium-coated composition according to claim 1, wherein, Rf contains 2 to 10 main chain carbon atoms.

17. The lithium-coated composition according to claim 1, wherein, Rf contains 3 to 10 main chain carbon atoms.

18. The lithium-coated composition according to claim 1, wherein, Rf contains 3 to 8 main chain carbon atoms.

19. The lithium-coated composition according to claim 16, wherein, The number of carbon atoms in Rf is an integer from 2 to 10.

20. The lithium-coated composition according to claim 16, wherein, The number of carbon atoms in Rf is an integer from 3 to 10.

21. The lithium-coated composition according to claim 16, wherein, The number of carbon atoms in Rf is an integer from 3 to 8.

22. The lithium-coated composition according to claim 1, wherein, Rf also contains one or more heteroatoms selected from the group consisting of iodine, nitrogen, oxygen, sulfur, and phosphorus.

23. The lithium-coated composition according to claim 22, wherein, The number of any one of the heteroatoms in Rf is one or more.

24. The lithium-coated composition according to claim 22, wherein, The number of any one of the heteroatoms in Rf is selected from 1 to 5.

25. The lithium-coated composition according to claim 22, wherein, The number of any one of the heteroatoms in Rf is selected from 1, 2, 3 or 4.

26. The lithium-coated composition according to claim 22, wherein, The number of heteroatoms in Rf satisfies one or more of the following: The number of oxygen atoms in Rf is 1, 2, 3, 4 or 5; The number of nitrogen atoms in Rf is 1, 2, or 3; The number of sulfur atoms in Rf is 1, 2, or 3; The number of phosphorus atoms in Rf is 1 or 2; The number of iodine atoms in Rf is 1, 2, 3, 4, 5, or 6.

27. The lithium-coated composition according to claim 1, wherein, Rf contains one or more groups selected from iodine, -NR 12 Atoms or atomic groups in the group consisting of -, -O-, -S-, -S(O)2- and >P(=O)-, where R 12 For H or C 1-3 alkyl.

28. The lithium-coated composition according to claim 27, wherein, R 12 It is H or methyl.

29. The lithium-coated composition according to claim 27, wherein, Rf contains one or more atoms or groups of atoms selected from the group consisting of -O-, -S(O)2- and -(O=)P(O-)2.

30. The lithium-coated composition according to claim 29, wherein, Rf contains one or more -O-.

31. The lithium-coated composition according to claim 29, wherein, Rf contains -S(O)2F.

32. The lithium-coated composition according to claim 29, wherein, Rf contains -(O=)P(O-)2.

33. The lithium-coated composition according to claim 1, wherein, Each occurrence of the fluorine-substituted aliphatic group is independently either a straight-chain structure or a branched-chain structure.

34. The lithium-coated composition according to claim 1, wherein, The structure of Rf is independently shown as in Equation III-1, Equation III-2, or Equation III-3: Among them, R 31 R 32 and R 3 Each occurrence is independently H or F; each occurrence of m3 is independently an integer from 2 to 10; Formula III-1 contains at least 4 F atoms; R 41a R 42a R 4a R 41b R 42b and R 4b Each occurrence is independently either H or F; m 4a and m 4b Each occurrence is an independent integer from 1 to 9; Formula III-2 contains at least 4 F atoms; R 51 and R 52 Each occurrence is independently H or F; each occurrence of m5 is independently an integer from 2 to 10; Formula III-3 contains at least 4 F atoms.

35. The lithium-coated composition according to claim 34, wherein, m3 is an integer from 3 to 10.

36. The lithium-coated composition according to claim 34, wherein, m3 is an integer from 3 to 8.

37. The lithium-coated composition according to claim 34, wherein, m 4a and m 4b Each is an integer from 2 to 9.

38. The lithium-coated composition according to claim 34, wherein, m 4a and m 4b Each is an independent integer from 2 to 8.

39. The lithium-coated composition according to claim 34, wherein, m 4a and m 4b Each is an integer between 3 and 8.

40. The lithium-coated composition according to claim 34, wherein, m 4a and m 4b Each is an integer between 3 and 6, independent of the others.

41. The lithium-coated composition according to claim 34, wherein, m5 is an integer from 3 to 10.

42. The lithium-coated composition according to claim 34, wherein, m5 is an integer from 3 to 8.

43. The lithium-coated composition according to claim 34, wherein, Each time Formula III-1 appears, the number of H atoms is 0, 1, 2, 3, or 4; or each time Formula III-2 appears, the number of H atoms is 0, 1, 2, 3, 4, 5, or 6; or each time Formula III-3 appears, the number of H atoms is 0, 1, 2, 3, or 4.

44. The lithium-coated composition according to claim 43, wherein, Each time Formula III-1 appears, the number of H atoms is 0; or each time Formula III-2 appears, the number of H atoms is 0; or each time Formula III-3 appears, the number of H atoms is 0.

45. The lithium-coated composition according to claim 34, wherein, Rf is independently selected from any of the following structures: , , , , , , and .

46. ​​The lithium-coated composition according to claim 1, wherein, X is either H independently or an electron-withdrawing group containing 1 to 6 non-hydrogen atoms.

47. The lithium-coated composition according to claim 46, wherein, X can be H independently or a cyano or nitro group.

48. The lithium-coated composition according to claim 1, wherein, Z can be O, S, or NH independently.

49. The lithium-coated composition according to claim 1, wherein, Z can be either O or NH.

50. The lithium-coated composition according to claim 1, wherein, Z is O.

51. The lithium-coated composition according to claim 1, wherein, Z is NH.

52. The lithium-coated composition according to claim 1, wherein, n is an integer between 10 and 1000.

53. The lithium-coated composition according to claim 1, wherein, n is an integer from 10 to 950.

54. The lithium-coated composition according to claim 1, wherein, n is an integer from 10 to 800.

55. The lithium-coated composition according to claim 1, wherein, n is an integer from 15 to 800.

56. The lithium-coated composition according to claim 1, wherein, n is an integer between 20 and 800.

57. The lithium-coated composition according to claim 1, wherein, n is an integer between 40 and 800.

58. The lithium-coated composition according to claim 1, wherein, n is an integer between 50 and 800.

59. The lithium-coated composition according to claim 1, wherein, n is an integer between 100 and 800.

60. The lithium-coated composition according to claim 1, wherein, n is an integer between 10 and 750.

61. The lithium-coated composition according to claim 1, wherein, n is an integer between 15 and 750.

62. The lithium-coated composition according to claim 1, wherein, n is an integer between 20 and 750.

63. The lithium-coated composition according to claim 1, wherein, n is an integer between 40 and 750.

64. The lithium-coated composition according to claim 1, wherein, n is an integer between 50 and 750.

65. The lithium-coated composition according to claim 1, wherein, n is an integer between 80 and 750.

66. The lithium-coated composition according to claim 1, wherein, n is an integer between 100 and 750.

67. The lithium-coated composition according to claim 1, wherein, n is an integer between 10 and 650.

68. The lithium-coated composition according to claim 1, wherein, n is an integer between 15 and 650.

69. The lithium-coated composition according to claim 1, wherein, n is an integer between 20 and 650.

70. The lithium-coated composition according to claim 1, wherein, n is an integer between 40 and 650.

71. The lithium-coated composition according to claim 1, wherein, n is an integer between 50 and 650.

72. The lithium-coated composition according to claim 1, wherein, n is an integer between 100 and 650.

73. The lithium-coated composition according to claim 1, wherein, n is an integer between 150 and 500.

74. The lithium-coated composition according to claim 1, wherein, n is an integer between 200 and 350.

75. The lithium-coated composition according to claim 1, wherein, The number-average molecular weight of the polymer Poly is selected from 10 kDa to 200 kDa.

76. The lithium-coated composition according to claim 1, wherein, The number-average molecular weight of the polymer Poly is selected from 50 kDa to 100 kDa.

77. The lithium-coated composition according to claim 1, wherein, The lithium-containing metal includes lithium metal or lithium alloy.

78. The lithium-coated composition according to claim 77, wherein, The lithium alloy contains lithium, and also contains one or more of the following: silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium.

79. A negative electrode plate, wherein, The negative electrode includes a negative electrode substrate and a polymer layer stacked together; the negative electrode substrate includes a lithium-containing layer in contact with the polymer layer, the lithium-containing layer contains lithium, and the polymer layer is chemically bonded to at least a portion of the lithium in the lithium-containing layer; The polymer layer comprises the polymer Poly as defined in any one of claims 1 to 78 of the lithium-coated composition.

80. The negative electrode sheet according to claim 79, wherein, The lithium-containing layer comprises lithium metal or a lithium alloy.

81. The negative electrode sheet according to claim 80, wherein, The lithium alloy contains lithium, and also contains one or more of the following: silver, magnesium, aluminum, gold, zinc, tin, copper, nickel, and titanium.

82. The negative electrode sheet according to claim 79, wherein, The polymer layer also contains an electrolyte.

83. The negative electrode sheet according to claim 82, wherein, The electrolyte contains lithium salt and electrolyte solvent.

84. The negative electrode sheet according to claim 83, wherein, The lithium salt is selected from one or more of lithium hexafluorophosphate, tetrafluoroboric acid, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium perchlorate, and lithium dioxoborate.

85. The negative electrode according to claim 83, wherein the electrolyte solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, butenyl carbonate, ethylene glycol dimethyl ether, tetrahydrofuran, dioxopentane, methyl nonafluorobutyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, octafluoropentyl-tetrafluoroethyl ether, 1,2-di(cyanoethoxy)ethane, diphenyl ether, and 18-crown ether-6.

86. The negative electrode sheet according to claim 83, wherein, The concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 10 mol / L.

87. The negative electrode sheet according to claim 83, wherein, The concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 8 mol / L.

88. The negative electrode sheet according to claim 83, wherein, The concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 5 mol / L.

89. The negative electrode sheet according to claim 83, wherein, The concentration of the lithium salt in the electrolyte is selected from 5 mol / L to 10 mol / L.

90. The negative electrode sheet according to claim 83, wherein, The concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 3 mol / L.

91. The negative electrode sheet according to claim 83, wherein, The concentration of the lithium salt in the electrolyte is selected from 0.5 mol / L to 2 mol / L.

92. The negative electrode sheet according to claim 82, wherein, The mass ratio of the polymer (Poly) to the electrolyte is from 199:1 to 1:

1.

93. The negative electrode sheet according to claim 82, wherein, The mass ratio of the polymer Poly to the electrolyte is 49:1 to 1:

1.

94. The negative electrode sheet according to claim 82, wherein, The mass ratio of the polymer (Poly) to the electrolyte is from 9.5:1 to 1:

1.

95. The negative electrode sheet according to claim 82, wherein, The mass ratio of the polymer (Poly) to the electrolyte is 8:1 to 2:

1.

96. The negative electrode sheet according to claim 82, wherein, The mass ratio of the polymer (Poly) to the electrolyte is 6:1 to 1:

1.

97. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 0.5% to 50% of the mass of the polymer layer.

98. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 1% to 50% of the mass of the polymer layer.

99. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 2% to 50% of the mass of the polymer layer.

100. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 5% to 50% of the mass of the polymer layer.

101. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 8% to 50% of the mass of the polymer layer.

102. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 9% to 50% of the mass of the polymer layer.

103. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 9.5% to 50% of the mass of the polymer layer.

104. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 10% to 50% of the mass of the polymer layer.

105. The negative electrode sheet according to claim 82, wherein, The electrolyte accounts for 30% to 50% of the mass of the polymer layer.

106. The negative electrode sheet according to claim 79, wherein, The thickness of the polymer layer is selected from 5 nm to 10 μm.

107. The negative electrode according to claim 79, wherein the thickness of the polymer layer is selected from 50 nm to 8 μm.

108. The negative electrode according to claim 79, wherein the thickness of the polymer layer is selected from 50 nm to 5 μm.

109. The negative electrode according to claim 79, wherein the thickness of the polymer layer is selected from 100 nm to 5 μm.

110. The negative electrode sheet according to claim 79, wherein, The elastic modulus of the polymer layer is 0.1 MPa ~ 80 MPa.

111. The negative electrode sheet according to claim 79, wherein, The elastic modulus of the polymer layer at 25 °C is selected from 0.5 MPa to 50 MPa.

112. The negative electrode sheet according to claim 79, wherein, The elastic modulus of the polymer layer at 25 °C is selected from 1 MPa to 50 MPa.

113. The negative electrode sheet according to claim 79, wherein, The elastic modulus of the polymer layer at 25 °C is selected from 10 MPa to 50 MPa.

114. The negative electrode sheet according to claim 79, wherein, The elastic deformation range of the polymer layer is 20% to 500%.

115. The negative electrode sheet according to claim 79, wherein, The polymer layer has an elastic deformation range of 20% to 300% at 25 °C.

116. The negative electrode sheet according to claim 79, wherein, The polymer layer has an elastic deformation range of 20% to 200% at 25 °C.

117. The negative electrode sheet according to claim 79, wherein, The polymer layer has an elastic deformation range of 100% to 300% at 25 °C.

118. The negative electrode sheet according to claim 79, wherein, The polymer layer has an elastic deformation range of 100% to 200% at 25 °C.

119. The negative electrode sheet according to claim 79, wherein, The polymer layer has an elastic deformation range of 100% to 190% at 25 °C.

120. The negative electrode sheet according to claim 82, wherein, Based on the electrolyte, the swelling ratio of the polymer layer is 5% to 50%.

121. The negative electrode sheet according to claim 82, wherein, Based on the electrolyte, the swelling ratio of the polymer layer at 25 °C is selected from 10% to 50%.

122. The negative electrode sheet according to claim 82, wherein, Based on the electrolyte, the swelling ratio of the polymer layer at 25 °C is selected from 10% to 45%.

123. The negative electrode sheet according to claim 82, wherein, Based on the electrolyte, the swelling ratio of the polymer layer at 25 °C is selected from 20% to 45%.

124. The negative electrode sheet according to claim 120, wherein, Based on the electrolyte, the ionic conductivity of the swollen polymer layer is 5 × 10⁻⁶. -3 S / cm to 1×10 -6 S / cm.

125. The negative electrode sheet according to claim 120, wherein, The ionic conductivity of the swollen polymer layer at 25 °C is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -5 S / cm.

126. The negative electrode sheet according to claim 120, wherein, The ionic conductivity of the swollen polymer layer at 25 °C is selected from 5 × 10⁻⁶. -3 S / cm to 1×10 -4 S / cm.

127. The negative electrode sheet according to claim 120, wherein, The ionic conductivity of the swollen polymer layer at 25 °C is selected from 3 × 10⁻⁶. -3 S / cm to 1×10 -4 S / cm.

128. The negative electrode sheet according to claim 120, wherein, The ionic conductivity of the swollen polymer layer at 25 °C is selected from 3 × 10⁻⁶. -3 S / cm up to 5×10 -4 S / cm.

129. The negative electrode sheet according to claim 79, wherein, The negative electrode substrate also includes a negative electrode current collector; the negative electrode current collector is located on the side of the lithium-containing layer away from the polymer layer.

130. The negative electrode sheet according to claim 129, wherein, A second negative electrode active material layer is provided between the negative electrode current collector and the lithium-containing layer. The composition of the second negative electrode active material layer may be the same as or different from that of the lithium-containing layer.

131. An electrode assembly comprising a positive electrode, a separator, and a negative electrode as described in any one of claims 79 to 130, wherein the separator is disposed between the negative electrode and the positive electrode; and the polymer layer is disposed at least on the surface of the negative electrode substrate near the separator.

132. A secondary battery comprising a cell electrolyte and an electrode assembly as described in claim 131, wherein the cell electrolyte is disposed between the polymer layer and the positive electrode sheet; wherein, The electrolyte in the battery cell can be liquid, gel, or solid.

133. The secondary battery according to claim 132, wherein, The electrolyte in the battery cell and the electrolyte in the polymer layer may have the same or different compositions.

134. The secondary battery according to claim 132, wherein, The charging current density of the secondary battery is selected from 0.3 mA / cm². 2 ~ 12 mA / cm 2 .

135. The secondary battery according to claim 132, wherein, The charging current density of the secondary battery is selected from 1 mA / cm². 2 ~ 10 mA / cm 2 .

136. The secondary battery according to claim 132, wherein, The charging current density of the secondary battery is selected from 1 mA / cm². 2 ~ 6 mA / cm 2 .

137. A battery module comprising the secondary battery as described in any one of claims 132 to 136.

138. A battery pack comprising the battery module of claim 137.

139. An electrical device comprising one or more of the secondary battery as described in any one of claims 132 to 136, the battery module as described in claim 137, and the battery pack as described in claim 138.

140. The application of monomer compound II in the preparation of negative electrode sheets, among which, The structure of the monomeric compound II is shown in Formula II: (II) Wherein, Rf, Z and X are each independently Rf, Z and X in the lithium coating composition as defined in any one of claims 1 to 78; wherein, the monomer compound II contacts the lithium in the lithium-containing layer of the negative electrode substrate and forms a polymer layer by in-situ polymerization, the polymer layer comprising polymer Poly, at least one cyano group in the polymer Poly forming a chemical bond with the lithium in the lithium-containing layer.

141. A method for preparing a negative electrode sheet, comprising the following steps: A negative electrode substrate is provided, wherein the outermost layer of at least one side of the negative electrode substrate is a lithium-containing layer, the lithium-containing layer comprising a lithium-containing metal; a reaction mixture containing monomer compound II and an electrolyte is also provided. The reaction mixture is coated onto the lithium-containing layer surface of at least one side of the negative electrode substrate, and the monomer compound II is polymerized in situ to form a polymer layer; (II) in, Rf, Z, and X are each independently Rf, Z, and X in the lithium-coated composition as defined in any one of claims 1 to 78; The electrolyte is the electrolyte in the negative electrode as defined in any one of claims 79 to 130.

142. The preparation method according to claim 141, wherein, The mass ratio of the monomer compound II to the electrolyte is 199:1 to 1:

1.

143. The preparation method according to claim 141, wherein, The mass ratio of the monomer compound II to the electrolyte is selected from 19:1 to 1:

1.

144. The preparation method according to claim 141, wherein, The mass ratio of the monomer compound II to the electrolyte is selected from 9.5:1 to 1:

1.

145. The preparation method according to claim 141, wherein, The mass ratio of the monomer compound II to the electrolyte is selected from 8:1 to 2:

1.

146. The preparation method according to claim 141, wherein, The mass ratio of the monomer compound II to the electrolyte is selected from 6:1 to 1:

1.

147. The preparation method according to claim 141, wherein, In the step of coating the reaction mixture onto the lithium-containing layer surface of at least one side of the negative electrode substrate, the coating method is selected from the coating method.

148. The preparation method according to claim 147, wherein, The coating method is selected from either spray coating or spin coating.

149. The preparation method according to claim 141, wherein, The reaction temperature for the in-situ polymerization is selected from 30 °C to 100 °C.

150. The preparation method according to claim 141, wherein, The reaction temperature for the in-situ polymerization is selected from 30 °C to 50 °C.

151. The preparation method according to claim 141, wherein, The reaction temperature for the in-situ polymerization is selected from 40 °C to 60 °C.

152. The preparation method according to claim 141, wherein, The reaction time for the in-situ polymerization is selected from 0.1 h to 24 h.

153. The preparation method according to claim 141, wherein, The reaction time for the in-situ polymerization is selected from 0.1 h to 12 h.

154. The preparation method according to claim 141, wherein, The reaction time for the in-situ polymerization is selected from 0.1 h to 2 h.

155. The preparation method according to claim 141, wherein, In the step of coating the reaction mixture onto the lithium-containing layer surface of at least one side of the negative electrode substrate, the coating thickness of the reaction mixture is selected from 100 nm to 8 μm.

156. The preparation method according to claim 141, wherein, The coating thickness of the reaction mixture is selected from 50 nm to 5 μm.

157. The preparation method according to claim 141, wherein, The coating thickness of the reaction mixture is selected from 50 nm to 8 μm.

158. The preparation method according to claim 141, wherein, The polymer layer formed is the polymer layer in the negative electrode as defined in any one of claims 106 to 128.

159. The preparation method according to claim 141, wherein, The negative electrode substrate is a pure lithium sheet.

160. The preparation method according to claim 141, wherein, The negative electrode substrate also includes a negative electrode current collector; the negative electrode current collector is located on the side of the lithium-containing layer away from the polymer layer.

161. The preparation method according to claim 160, wherein, A second negative electrode active material layer is provided between the negative electrode current collector and the lithium-containing layer. The composition of the second negative electrode active material layer may be the same as or different from that of the lithium-containing layer.

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