Electrolyte, lithium secondary battery, and electric device

Abstract

An electrolyte, a lithium secondary battery and a power utilization device, the electrolyte comprising a first solvent, a silane compound containing a carbon-carbon double bond and a cyclic lithium borate compound, the first solvent comprising a cyclic carbonate compound; wherein the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy: 0.001≤(W1+W2) / W3≤2.67 based on the total mass of the electrolyte. The combination of the silane compound containing a carbon-carbon double bond and the cyclic lithium borate compound can improve the flexibility and thermal stability of the SEI film, thereby reducing the gas generation degree during the cycle and storage of the lithium secondary battery, and improving the storage performance, fast charging performance and cycle performance of the lithium secondary battery.

Description

Electrolyte, lithium secondary battery and electrical device

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311600919.X, filed on November 28, 2023, entitled “Electrolyte, Lithium Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the technical field of lithium batteries, and in particular to an electrolyte, a lithium secondary battery, and an electrical device. Background Art

[0004] In recent years, the application of lithium-ion batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As lithium-ion batteries have achieved significant development, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0005] Improving the power performance, cycle and storage life of batteries has always been the industry's goal, but due to the side reactions of the electrolyte at the anode and cathode interfaces, the overall performance of the battery cell is poor.

[0006] Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide an electrolyte aimed at improving the flexibility and thermal stability of the SEI (Solid Electrolyte Interphase) membrane, thereby reducing the gas production during the cycle and storage process of the lithium secondary battery, improving the storage performance, fast charging performance and cycle performance of the lithium secondary battery, and comprehensively improving the performance of the lithium secondary battery.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present application provides an electrolyte for a lithium secondary battery, comprising a first solvent, a silane compound containing a carbon-carbon double bond, and a cyclic lithium borate compound, wherein the first solvent comprises a cyclic carbonate compound, and the cyclic carbonate compound comprises at least one of ethylene carbonate, fluoroethylene carbonate, and propylene carbonate; wherein, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond, and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.001≤(W1+W2) / W3≤2.67.

[0009] In any embodiment, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond, and the mass content W2 of the cyclic lithium borate compound satisfy: 0.005≤(W1+W2) / W3≤2.

[0010] By controlling the content of cyclic carbonate compounds in the electrolyte within an appropriate range and adding silane compounds containing carbon-carbon double bonds and cyclic lithium borate compounds within the above content range, the flexibility and thermal stability of the SEI film can be effectively improved, thereby taking into account the storage performance and DC impedance of the lithium secondary battery, and comprehensively improving the performance of the lithium secondary battery.

[0011] In any embodiment, the cyclic carbonate compound includes at least one of ethylene carbonate, fluoroethylene carbonate, and propylene carbonate.

[0012] When cyclic carbonate compounds are used as solvents in the electrolyte, they have excellent ionic conductivity and film-forming properties.

[0013] In any embodiment, the silane compound containing a carbon-carbon double bond includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, and vinyltrimethylsilane.

[0014] In any embodiment, the silane compound containing a carbon-carbon double bond comprises tetravinylsilane.

[0015] Due to the presence of carbon-carbon double bonds, the above-mentioned silane compounds containing carbon-carbon double bonds can form a film at the anode in preference to cyclic carbonate compounds, and generate polymer components in the SEI film, thereby improving the flexibility of the SEI film; at the same time, the SEI film can cover the surface of the anode electrode to reduce the degree of exposure of the anode electrode to the electrolyte, reduce side reactions and gas production, and improve the performance of lithium secondary batteries.

[0016] In any embodiment, the cyclic lithium borate compound includes a compound having a structure shown in Formula I,

[0017] Wherein, Y1, Y2, Y3, and Y4 independently include at least one of an oxygen atom and a sulfur atom. In any embodiment, the cyclic lithium borate compound includes At least one of .

[0018] The above-mentioned cyclic lithium borate compounds can be reduced to form a film preferentially over cyclic carbonate compounds, and form a lithium salt-rich component in the SEI film, thereby improving the thermal stability of the SEI film, reducing the overall oxidative decomposition degree of the SEI film, and its solubility in the electrolyte solvent, thereby improving the storage performance of the lithium secondary battery.

[0019] In any embodiment, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.01≤W1 / W2≤200.

[0020] In any embodiment, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.1≤W1 / W2≤10.

[0021] In any embodiment, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.5≤W1 / W2≤5.

[0022] By controlling the mass content ratio of the silane compound containing a carbon-carbon double bond and the cyclic lithium borate compound within an appropriate range, the thermal stability and flexibility of the SEI film can be comprehensively improved through the synergistic effect of the two, thereby taking into account the storage performance and DC impedance of the lithium secondary battery and comprehensively improving the performance of the lithium secondary battery.

[0023] In any embodiment, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound satisfies: 3%≤W3≤20%.

[0024] In any embodiment, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound satisfies: 5%≤W3≤20%.

[0025] Controlling the content of cyclic carbonate compounds in the electrolyte within an appropriate range can take into account both the formation of the SEI film and the ionic conductivity of the electrolyte, thereby improving the cycle performance of the lithium secondary battery and reducing the gas generation during storage.

[0026] In any embodiment, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond satisfies: 0.01%≤W1≤5%.

[0027] In any embodiment, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond satisfies: 0.01%≤W1≤3%.

[0028] Controlling the content of silane compounds containing carbon-carbon double bonds in the electrolyte within an appropriate range can improve the flexibility of the SEI film, while reducing side reactions and gas production, thereby improving the performance of lithium secondary batteries.

[0029] In any embodiment, based on the total mass of the electrolyte, the mass content W2 of the cyclic lithium borate compound satisfies: 0.01%≤W2≤3%.

[0030] In any embodiment, based on the total mass of the electrolyte, the mass content W2 of the cyclic lithium borate compound satisfies: 0.1%≤W2≤2%.

[0031] Controlling the content of cyclic lithium borate compounds in the electrolyte within an appropriate range can improve the thermal stability of the SEI film, thereby enhancing the storage performance of the lithium secondary battery.

[0032] In any embodiment, the electrolyte includes a second solvent, the second solvent includes a linear carbonate compound; the linear carbonate compound includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

[0033] Adding the above-mentioned second solvent to the electrolyte can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and further improve the fast charging performance and cycle life of the battery.

[0034] In any embodiment, the electrolyte includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonyl(perfluorobutylsulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide; the concentration of the lithium salt in the electrolyte is 0.8 mol / L to 1.3 mol / L.

[0035] Controlling the concentration of lithium salt in the electrolyte within the above range can increase the conductivity of the electrolyte, which is beneficial to further improve the cycle life of the battery.

[0036] A second aspect of the present application provides a lithium secondary battery, comprising a positive electrode sheet, a negative electrode sheet, and the electrolyte of the first aspect of the present application.

[0037] In any embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer located on at least one side of the positive electrode current collector, wherein the positive electrode material layer includes Li d [Ni x Co y X1 z M1 1-x-y-z]O2, LiMn2O4, Li2MnO3·(1-a)LiAO2, LiM2X2O4, one or more thereof, wherein 0.1≤d≤1, X1 comprises Mn and / or Al; M1 comprises one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1; A comprises one or more of Ni, Co, Mn, 0<a<1; M2 comprises one or more of Fe, Mn, Ni, Co; X2O4 h- X2 includes one or more of S, P, As, V, Mo, and W, and h=2 or 3.

[0038] In any embodiment, the positive electrode material layer includes Li d [Ni x Co y X1 z M1 1-x-y-z ]O2, wherein 0.1≤d≤1, X1 includes Mn and / or Al; M1 includes one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1.

[0039] In any embodiment, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer located on at least one side of the negative electrode current collector, and the negative electrode material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microcarbon beads, silicon-based materials and tin-based materials.

[0040] In any embodiment, the negative electrode material layer includes at least one of artificial graphite and natural graphite.

[0041] A third aspect of the present application provides an electrical device comprising the lithium secondary battery of the second aspect of the present application.

[0042] The secondary battery manufactured using the electrolyte provided by the present application has improved cycle performance and storage performance. Correspondingly, the electrical device provided by the present application also has good performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0044] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0045] FIG3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0046] Description of reference numerals:

[0047] 5 secondary battery; 51 housing; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0048] Below, the embodiments of the electrolyte, lithium secondary battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0049] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0051] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0052] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0053] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0054] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0055] As a solvent component in the electrolyte, cyclic carbonate compounds (such as ethylene carbonate) have excellent ionic conductivity and film-forming properties, but the proton hydrogen produced during the oxidation process will attack the lithium hexafluorophosphate in the solvent, thereby destroying the SEI film, causing the electrolyte to continuously undergo redox decomposition at the positive and negative electrodes, consuming active lithium, and thus deteriorating the performance of the battery cell. At the same time, cyclic carbonate compounds (such as ethylene carbonate) are oxidized and decomposed to produce gas at the positive electrode, causing the battery cell to expand, the distance between the positive and negative electrodes to increase, and the lithium ion migration path to become longer. In order to avoid these defects, a common practice is to reduce the content of cyclic carbonate compounds (such as ethylene carbonate) in the electrolyte, but reducing the content of cyclic carbonate compounds will not only affect the ionic conductivity of the electrolyte, but also affect the formation of the SEI film.

[0056] [Electrolyte]

[0057] In order to achieve the above-mentioned objectives, the present application provides an electrolyte for a lithium secondary battery, comprising a first solvent, a silane compound containing a carbon-carbon double bond, and a cyclic lithium borate compound, wherein the first solvent comprises a cyclic carbonate compound, and the cyclic carbonate compound comprises at least one of ethylene carbonate, fluoroethylene carbonate, and propylene carbonate; wherein, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond, and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.001≤(W1+W2) / W3≤2.67.

[0058] In some embodiments, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond, and the mass content W2 of the cyclic lithium borate compound satisfy: 0.005≤(W1+W2) / W3≤2.

[0059] In the electrolyte provided by this application, silane compounds containing carbon-carbon double bonds can effectively form polymer components in the SEI film, thereby improving the flexibility of the SEI film and, to a certain extent, inhibiting the reductive decomposition of the electrolyte. Cyclic lithium borate compounds also form lithium salt-rich components in the SEI film, which can improve the thermal stability of the SEI. Through the synergistic effect of these two, the SEI film's stability is enhanced while its flexibility is also taken into account, thereby reducing the degree of gassing during the cycling and storage of lithium secondary batteries, improving the storage performance and fast charging performance of lithium secondary batteries, and comprehensively improving the cycling performance of lithium secondary batteries.

[0060] In addition, by controlling the content of cyclic carbonate compounds in the electrolyte within an appropriate range and adding silane compounds containing carbon-carbon double bonds and cyclic lithium borate compounds within the above content range, the flexibility and thermal stability of the SEI film can be effectively improved, thereby taking into account the storage performance and DC impedance of the lithium secondary battery, and comprehensively improving the performance of the lithium secondary battery.

[0061] In some embodiments, the cyclic carbonate compound includes at least one of ethylene carbonate, fluoroethylene carbonate, and propylene carbonate.

[0062] When cyclic carbonate compounds are used as solvents in the electrolyte, they have excellent ionic conductivity and film-forming properties.

[0063] In some embodiments, the silane compound containing a carbon-carbon double bond includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane, and vinyltrimethylsilane.

[0064] In some embodiments, the silane compound containing a carbon-carbon double bond includes tetravinylsilane.

[0065] Due to the presence of carbon-carbon double bonds, the above-mentioned silane compounds containing carbon-carbon double bonds can be reduced to form a film at the anode before the solvent, and generate polymer components in the SEI film, thereby improving the flexibility of the SEI film; at the same time, the SEI film can cover the surface of the anode electrode to reduce the degree of exposure of the anode electrode to the electrolyte, reduce side reactions and gas production, and improve the performance of lithium secondary batteries.

[0066] In some embodiments, the cyclic lithium borate compound includes a compound having a structure shown in Formula I,

[0067] Wherein, Y1, Y2, Y3, and Y4 each independently include at least one of an oxygen atom and a sulfur atom. In some embodiments, the cyclic lithium borate compound includes At least one of .

[0068] In some optional embodiments, in Formula I, Y1, Y2, Y3, and Y4 all include oxygen atoms.

[0069] The above-mentioned cyclic lithium borate compounds can be reduced to form a film preferentially over cyclic carbonate compounds, and form a lithium salt-rich component in the SEI film, thereby improving the thermal stability of the SEI film, reducing the overall oxidative decomposition degree of the SEI film, and its solubility in the electrolyte solvent, thereby improving the storage performance of the lithium secondary battery.

[0070] In some embodiments, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.01≤W1 / W2≤200.

[0071] In some embodiments, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.1≤W1 / W2≤10.

[0072] In some embodiments, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.5≤W1 / W2≤5.

[0073] When the W1 / W2 ratio is too low, the content of the silane compound containing a carbon-carbon double bond is too low, making it difficult to improve the flexibility of the SEI film. On the other hand, when the W1 / W2 ratio is too high, the content of the cyclic lithium borate compound is too low, making it difficult to improve the thermal stability of the SEI film. Therefore, controlling the mass ratio of the silane compound containing a carbon-carbon double bond to the cyclic lithium borate compound within an appropriate range can, through the synergistic effect of the two, comprehensively improve the thermal stability and flexibility of the SEI film, thereby balancing the storage performance and DC impedance of the lithium secondary battery and comprehensively improving the performance of the lithium secondary battery.

[0074] In some embodiments, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound satisfies: 3%≤W3≤20%.

[0075] In some embodiments, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound satisfies: 5%≤W3≤20%.

[0076] When the cyclic carbonate content in the electrolyte is less than 3%, the electrolyte conductivity is too low, thus affecting the battery's cycling performance. When the cyclic carbonate content in the electrolyte is higher than 20%, its oxidative decomposition and gas production can damage battery performance. Therefore, controlling the cyclic carbonate content in the electrolyte within an appropriate range can balance the formation of the SEI film and the ionic conductivity of the electrolyte, thereby improving the cycling performance of lithium secondary batteries and reducing the degree of gas production during storage.

[0077] In some embodiments, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond satisfies: 0.01%≤W1≤5%.

[0078] In some embodiments, based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond satisfies: 0.01%≤W1≤3%.

[0079] When the content of silane compounds containing carbon-carbon double bonds in the electrolyte is less than 0.01%, it cannot effectively form a film. When the content of silane compounds containing carbon-carbon double bonds in the electrolyte is higher than 5%, the film formation impedance is too large, which affects the fast charging performance of the battery. Therefore, controlling the content of silane compounds containing carbon-carbon double bonds in the electrolyte within an appropriate range can improve the flexibility of the SEI film, while reducing side reactions and gas production, and improving the performance of lithium secondary batteries.

[0080] In some embodiments, based on the total mass of the electrolyte, the mass content W2 of the cyclic lithium borate compound satisfies: 0.01%≤W2≤3%.

[0081] In some embodiments, based on the total mass of the electrolyte, the mass content W2 of the cyclic lithium borate compound satisfies: 0.1%≤W2≤2%.

[0082] When the content of cyclic lithium borate compounds in the electrolyte is less than 0.01%, they do not effectively form a film. When the content of cyclic lithium borate compounds in the electrolyte is higher than 3%, the electrolyte viscosity may increase, which may deteriorate the conductivity of the electrolyte. Therefore, controlling the content of cyclic lithium borate compounds in the electrolyte within an appropriate range can improve the thermal stability of the SEI film, thereby enhancing the storage performance of lithium secondary batteries.

[0083] In some embodiments, the electrolyte includes a second solvent, the second solvent includes a linear carbonate compound; the linear carbonate compound includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate, and propyl propionate.

[0084] Adding the above-mentioned second solvent to the electrolyte can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and further improve the fast charging performance and cycle life of the battery.

[0085] In some embodiments, the electrolyte includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonyl(perfluorobutylsulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide; the concentration of the lithium salt in the electrolyte is 0.8 mol / L to 1.3 mol / L.

[0086] In some embodiments, the concentration of the lithium salt in the electrolyte is 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, or a value within a range consisting of any two of the above concentrations.

[0087] Controlling the concentration of lithium salt in the electrolyte within the above range can increase the conductivity of the electrolyte, which is beneficial to further improve the cycle life of the battery.

[0088] The present application also provides a lithium secondary battery comprising a positive electrode sheet, a negative electrode sheet, and the electrolyte of the first aspect of the present application. During the battery's charge and discharge process, active ions are intercalated and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte acts as an ion conductor between the positive electrode sheet and the negative electrode sheet. A separator is disposed between the positive electrode sheet and the negative electrode sheet, primarily to prevent a short circuit between the positive and negative electrodes while allowing ions to pass through.

[0089] [Positive electrode]

[0090] The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer located on at least one side of the positive electrode current collector.

[0091] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0092] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer located on at least one side of the positive electrode current collector, wherein the positive electrode material layer includes Li d [Ni x Co y X1 z M1 1-x-y-z ]O2, LiMn2O4, Li2MnO3·(1-a)LiAO2, LiM2X2O4, one or more thereof, wherein 0.1≤d≤1, X1 comprises Mn and / or Al; M1 comprises one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1; A comprises one or more of Ni, Co, Mn, 0<a<1; M2 comprises one or more of Fe, Mn, Ni, Co; X2O4 h- X2 includes one or more of S, P, As, V, Mo, and W, and h=2 or 3.

[0093] In some embodiments, the positive electrode material layer includes Li d [Ni x Co y X1 z M1 1-x-y-z ]O2, wherein 0.1≤d≤1, X1 includes Mn and / or Al; M1 includes one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1.

[0094] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0095] In some embodiments, the positive electrode material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0096] In some embodiments, the positive electrode material layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode material layer, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0098] [Negative electrode]

[0099] The negative electrode plate includes a negative electrode current collector and a negative electrode material layer located on at least one side of the negative electrode current collector.

[0100] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0101] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer located on at least one side of the negative electrode current collector, and the negative electrode material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microcarbon beads, silicon-based materials and tin-based materials.

[0102] In some embodiments, the negative electrode material layer includes at least one of artificial graphite and natural graphite.

[0103] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0104] In some embodiments, the negative electrode material layer may further 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).

[0105] In some embodiments, the negative electrode material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0106] In some embodiments, the negative electrode material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0107] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode material layer, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0108] [Isolation film]

[0109] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0110] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0111] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0112] [Secondary battery]

[0113] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0114] 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. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0115] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0116] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0117] [Electrical devices]

[0118] In addition, the present application also provides an electrical device, which includes the lithium secondary battery provided by the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0119] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0120] Figure 3 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0121] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0122] Example

[0123] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0124] 1. Preparation method

[0125] Example 1

[0126] 1) Electrolyte

[0127] In an argon atmosphere glove box (H2O content <10ppm, O2 content <1ppm), a first solvent, ethylene carbonate (EC), and a second solvent, ethyl methyl carbonate (EMC), were mixed and 1 mol / L LiPF6 lithium salt was dissolved. Then, tetravinylsilane and lithium fluoromalonate (difluoro) borate (Y1-Y4 in Formula I are all O) were added and stirred to prepare an electrolyte. Based on the total mass of the electrolyte, the mass content W3 of the first solvent was 10%, the mass content W1 of tetravinylsilane was 2%, and the mass content W2 of lithium fluoromalonate (difluoro) borate was 1%.

[0128] 2) Preparation of positive electrode sheet

[0129] The positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone solvent system in a weight ratio of 90:5:5 to obtain a positive electrode slurry with a solid content of 50wt%; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil; the aluminum foil is dried at room temperature and then transferred to an 85℃ oven for drying and cold pressing, and then trimmed, cut into pieces, and slit, and then dried under vacuum conditions at 85℃ for 4h to make a positive electrode sheet.

[0130] 3) Preparation of negative electrode sheet

[0131] The negative electrode active material, artificial graphite, was mixed with the conductive agent Super P, the thickener sodium carboxymethyl cellulose (CMC-Na), and the binder styrene-butadiene rubber (SBR) in a mass ratio of 80:15:3:2 in deionized water to create a negative electrode slurry with a solid content of 30wt%. The negative electrode slurry was then coated onto the current collector copper foil. After drying at room temperature, the foil was transferred to an 85°C oven for drying. After cold pressing, trimming, cutting, and slitting, it was then dried at 120°C under vacuum for 12 hours to form the negative electrode sheet.

[0132] 4) Isolation film

[0133] A 16 μm polyethylene (PE) porous polymer film was used as the separator.

[0134] 5) Battery Preparation

[0135] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed in the middle of the positive and negative electrode sheets to isolate the positive and negative electrode sheets. The bare battery cell is wound and the tabs are welded. The bare battery cell is placed in an outer package, and the above-prepared electrolyte is injected into the dried battery cell. The battery cell is packaged, allowed to stand, formed, shaped, and capacity tested to complete the preparation of the soft-pack lithium secondary battery (the thickness of the soft-pack lithium secondary battery is 4.0 mm, the width is 60 mm, and the length is 140 mm).

[0136] The secondary batteries of Examples 2 to 21 and the secondary batteries of Comparative Examples 1 to 4 were prepared in a similar manner to the secondary battery of Example 1, but the composition of the battery electrodes and product parameters were adjusted. The different product parameters are detailed in Table 1.

[0137] 2. Performance Testing

[0138] 1. Electrolyte

[0139] 1) Ionic conductivity

[0140] The ionic conductivity test of the electrolyte is carried out according to the HG-T 4067-2015 method. The specific operation is as follows:

[0141] Pretreatment: Take the test solution and keep the temperature of the test solution constant to the test temperature and the standard solution constant to 25℃ (deviation ±0.1℃).

[0142] Test: Test the instrument with two standard solutions at 25°C. After calibration, clean the electrode and test the sample. Place the electrode vertically into the liquid to be tested, click to start the test, and wait for the data to stabilize for more than 10 seconds to record the test results.

[0143] 2) Measurement method of electrolyte solvent content

[0144] The test method for the solvent content of the electrolyte is carried out in accordance with GB / T 9722-2006. The specific method is as follows: prepare the standard solution, directly take the standard solution and sample for automatic FID detection, determine the type of additive based on the peak position, and calculate the content of the additive in the electrolyte based on the peak area.

[0145] 3) Measurement method of electrolyte additive (lithium salt) content

[0146] The test method for the content of salt additives is based on GB / T 6040-2002. The specific method is as follows: weigh a certain amount of electrolyte (the dilution concentration is in the middle of the standard curve), dilute to 100 mL with ultrapure water, and perform automatic sampling detection on an ion chromatograph. The type of additive is determined based on the peak position, and the additive content is determined based on the peak area.

[0147] 4) Test method for the mass content W3 of cyclic carbonate compounds, the mass content W1 of silane compounds containing carbon-carbon double bonds, and the mass content W2 of cyclic lithium borate compounds in the electrolyte

[0148] With reference to the standard GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents", the organic components in the electrolyte were qualitatively and quantitatively analyzed by gas chromatography to obtain the mass content W3 of cyclic carbonate compounds, the mass content W1 of silane compounds containing carbon-carbon double bonds, and the mass content W2 of cyclic lithium borate compounds in the electrolyte.

[0149] 2. Battery

[0150] 1) DC impedance

[0151] At 25°C, adjust the single cell state of charge to 50% SOC, let it rest for 30 minutes, and record the battery voltage at this time as U1 (V). Discharge it at 4C for 30 seconds, and record the battery voltage at this time as U2 (V). The corresponding battery discharge current I (mA) is 4 × the battery design capacity (mAh). DC resistance DCR (mΩ) = (U1 - U2) / I.

[0152] 2) Cycle performance

[0153] At 25°C, the prepared lithium secondary battery was charged at a constant current of 1C to 4.4V, then charged at a constant voltage of 0.05C, then left for 10 minutes, and then discharged at a constant current of 1C to 2.8V. The discharge capacity was recorded as C0. 300 cycles were performed according to the above charge and discharge process. The discharge capacity after 300 cycles was C1, and the battery's cycle capacity retention rate = C1 / C0×100%.

[0154] 3) Storage performance

[0155] At 25°C, the prepared lithium secondary battery was charged at a constant current rate of 1C to 4.4V, then charged at a constant voltage of 0.05C. After standing for 5 minutes, it was discharged at a constant current rate of 1C to 2.8V. The discharge capacity was recorded as D0. The lithium secondary battery was then stored at 60°C for 30 days. The lithium secondary battery was removed and allowed to return to 25°C. It was discharged at a constant current rate of 1C to 2.8V. After standing for 2 hours, it was charged at 1C to 4.4V. It was then charged at a constant voltage of 0.05C. After standing for 2 hours, it was discharged at 1C to 2.8V. The discharge capacity was recorded as D1. Discharge capacity retention = D1 / D0 × 100%.

[0156] 3. Analysis of test results of various embodiments and comparative examples

[0157] Batteries of various examples and comparative examples were prepared according to the above methods, and various performance parameters were measured. The results are shown in Table 1 below.

[0158] Table 1 Preparation parameters

[0159] Table 2 Preparation parameters

[0160] Table 3 Preparation and performance parameters

[0161] The electrolytes in Examples 1 to 18 all include a first solvent, a silane compound containing a carbon-carbon double bond, and a cyclic lithium borate compound. The lithium secondary batteries containing the electrolytes all have low DC impedance and excellent storage performance and cycle performance.

[0162] There is no silane compound containing a carbon-carbon double bond in the electrolyte of Comparative Example 1. From the comparison between Examples 1 to 18 and Comparative Example 1, it can be seen that adding a silane compound containing a carbon-carbon double bond to the electrolyte can effectively reduce the DC impedance and improve the storage performance and cycle performance of the lithium secondary battery.

[0163] There is no cyclic lithium borate compound in the electrolyte of Comparative Example 2. From the comparison between Examples 1 to 18 and Comparative Example 2, it can be seen that adding cyclic lithium borate compounds to the electrolyte can effectively reduce the DC impedance and improve the storage performance and cycle performance of the lithium secondary battery.

[0164] In the electrolytes of Examples 1 to 18, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond, and the mass content W2 of the cyclic lithium borate compound satisfy the following conditions: 0.001≤(W1+W2) / W3≤2.67, and 0.01≤W1 / W2≤200. The lithium secondary batteries containing the electrolytes all have low DC impedance and excellent storage performance and cycle performance.

[0165] In the electrolyte of Comparative Example 3, the value of (W1+W2) / W3 does not meet the range of 0.001≤(W1+W2) / W3≤2.67. From the comparison of Examples 1 to 18 with Comparative Example 3, it can be seen that by controlling the content of cyclic carbonate compounds, silane compounds containing carbon-carbon double bonds, and cyclic lithium borate compounds in the electrolyte within an appropriate range, the cycle performance, storage performance and DC impedance of the lithium secondary battery can be taken into account, thereby comprehensively improving the performance of the lithium secondary battery.

[0166] As can be seen from Examples 1-5, controlling the mass content W3 of the first solvent, ethylene carbonate, to 3% to 20% can result in lithium secondary batteries having lower DC impedance and better storage and cycling performance. In Comparative Example 3, the mass content W3 of ethylene carbonate is 2%. A comparison of Examples 1-5 with Comparative Example 3 shows that controlling the mass content W3 of the first solvent, ethylene carbonate, to 3% to 20%, can effectively reduce DC impedance and improve the storage and cycling performance of lithium secondary batteries.

[0167] It can be seen from Examples 1 and 6 to 9 that controlling the mass content W1 of the silane compound containing a carbon-carbon double bond to 0.01% to 5% can enable the lithium secondary battery to have lower DC impedance, better storage performance and cycle performance.

[0168] It can be seen from Examples 1 and 10 to 13 that controlling the mass content W2 of the cyclic lithium borate compound to 0.01% to 3% can enable the lithium secondary battery to have lower DC impedance, better storage performance and cycle performance.

[0169] As can be seen from Examples 1 and 14 to 17, by using a variety of different types of first solvents (e.g., ethylene carbonate, fluoroethylene carbonate), or a variety of different types of silane compounds containing carbon-carbon double bonds (e.g., tetravinylsilane, trivinylethylsilane, vinyltrimethylsilane), or a variety of different types of cyclic lithium borate compounds (e.g., compounds in which Y1, Y2, Y3, and Y4 in Formula I are all oxygen atoms, and compounds in which Y1 and Y2 are sulfur atoms, and Y3 and Y4 are oxygen atoms in Formula I), lithium secondary batteries can have lower DC impedance, better storage performance, and better cycle performance.

[0170] It can be seen from Examples 1 and 18 that the use of different types of negative electrode active materials (such as artificial graphite and mesophase microcarbon beads) can enable lithium secondary batteries to have lower DC impedance, better storage performance and cycle performance.

[0171] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An electrolyte for a lithium secondary battery, characterized in that: It includes a first solvent, a silane compound containing a carbon-carbon double bond, and a cyclic lithium borate compound, wherein the first solvent includes a cyclic carbonate compound, and the cyclic carbonate compound includes at least one of ethylene carbonate, fluoroethylene carbonate, and propylene carbonate; Among them, based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy: 0.001≤(W1+W2) / W3≤2.

67.

2. The electrolyte according to claim 1, characterized in that Based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy: 0.005≤(W1+W2) / W3≤2.

3. The electrolyte according to claim 1 or 2, characterized in that The silane compound containing a carbon-carbon double bond includes at least one of tetravinylsilane, trivinylethylsilane, divinyldiethylsilane and vinyltrimethylsilane.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The silane compound containing a carbon-carbon double bond includes tetravinylsilane.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The cyclic lithium borate compound includes a compound having a structure shown in Formula I, Wherein, Y1, Y2, Y3, and Y4 each independently include at least one of an oxygen atom and a sulfur atom.

6. The electrolyte according to any one of claims 1 to 5, characterized in that The cyclic lithium borate compound includes At least one of .

7. The electrolyte according to any one of claims 1 to 6, characterized in that Based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.01≤W1 / W2≤200.

8. The electrolyte according to any one of claims 1 to 7, characterized in that Based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.1≤W1 / W2≤10.

9. The electrolyte according to any one of claims 1 to 8, characterized in that Based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond and the mass content W2 of the cyclic lithium borate compound satisfy the following relationship: 0.5≤W1 / W2≤5.

10. The electrolyte according to any one of claims 1 to 9, characterized in that Based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound satisfies: 3%≤W3≤20%.

11. The electrolyte according to any one of claims 1 to 10, characterized in that Based on the total mass of the electrolyte, the mass content W3 of the cyclic carbonate compound satisfies: 5%≤W3≤20%.

12. The electrolyte according to any one of claims 1 to 11, characterized in that Based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond satisfies: 0.01%≤W1≤5%.

13. The electrolyte according to any one of claims 1 to 12, characterized in that Based on the total mass of the electrolyte, the mass content W1 of the silane compound containing a carbon-carbon double bond satisfies: 0.01%≤W1≤3%.

14. The electrolyte according to any one of claims 1 to 13, characterized in that Based on the total mass of the electrolyte, the mass content W2 of the cyclic lithium borate compound satisfies: 0.01%≤W2≤3%.

15. The electrolyte according to any one of claims 1 to 14, characterized in that Based on the total mass of the electrolyte, the mass content W2 of the cyclic lithium borate compound satisfies: 0.1%≤W2≤2%.

16. The electrolyte according to any one of claims 1 to 15, characterized in that The electrolyte includes a second solvent, and the second solvent includes a linear carbonate compound; The linear carbonate compound includes at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl acetate, methyl propionate, ethyl propionate and propyl propionate.

17. The electrolyte according to any one of claims 1 to 16, characterized in that The electrolyte includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonyl (perfluorobutylsulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide; The concentration of the lithium salt in the electrolyte is 0.8 mol / L to 1.3 mol / L.

18. A lithium secondary battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet and the electrolyte according to any one of claims 1 to 17.

19. The lithium secondary battery according to claim 18, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer located on at least one side of the positive electrode current collector, wherein the positive electrode material layer includes Li d [Ni x Co y X1 z M1 1-x-y-z ]O2, LiMn2O4, Li2MnO3·(1-a)LiAO2, LiM2X2O4 or one or more thereof, Wherein, 0.1≤d≤1, X1 includes Mn and / or Al; M1 includes one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1; A includes one or more of Ni, Co, Mn, 0<a<1; M2 includes one or more of Fe, Mn, Ni, Co; X2O4 h- X2 includes one or more of S, P, As, V, Mo, and W, and h=2 or 3.

20. The lithium secondary battery according to claim 19, characterized in that: The positive electrode material layer includes Li d [Ni x Co y X1 z M1 1-x-y-z ]O2, wherein 0.1≤d≤1, X1 includes Mn and / or Al; M1 includes one or more of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, 0≤x<1, 0≤y≤1, 0≤z≤1, x+y+z≤1.

21. The lithium secondary battery according to any one of claims 18 to 20, characterized in that: The negative electrode plate includes a negative electrode current collector and a negative electrode material layer located on at least one side of the negative electrode current collector, and the negative electrode material layer includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, intermediate phase micro carbon beads, silicon-based materials and tin-based materials.

22. The lithium secondary battery according to claim 21, characterized in that: The negative electrode material layer includes at least one of artificial graphite and natural graphite.

23. An electrical device, characterized in that: A lithium secondary battery comprising the lithium secondary battery according to any one of claims 18 to 22.

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