Lithium ion battery and electronic device

Abstract

The application relates to a lithium ion battery and an electronic device. The lithium ion battery comprises a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode additive; the electrolyte comprises a sulfur-containing additive and 1,3-propane sultone; (X+Y) / (W*A) is greater than or equal to 0.025; wherein the mass percentage of the sulfur-containing additive in the electrolyte is X%; the mass percentage of 1,3-propane sultone in the electrolyte is Y%; the mass percentage of the positive electrode additive in the positive electrode active material layer is W%; and the specific surface area of the positive electrode additive is A m 2 / g. The scheme provided by the application can make the lithium ion battery have excellent first coulomb efficiency, high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a lithium ion battery and an electronic device. BACKGROUND

[0002] Lithium ion batteries are widely used in consumer electronics, new energy vehicles and energy storage fields. With the rapid development of the new energy vehicle industry, consumers have higher requirements for the driving range and application scenarios, that is, the battery has higher energy density.

[0003] In related technologies, silicon material has higher theoretical capacity than graphite material, and is widely used in lithium ion batteries due to its abundant source and low price. However, silicon material will expand and contract to a large extent during the process of metal ion insertion and extraction, which will cause the degradation of electrochemical performance, and the degradation of electrochemical performance will be further intensified in high temperature environment; in low temperature working environment, the viscosity of electrolyte will increase, which will slow down the migration rate of lithium ions and increase the interface impedance of the battery, resulting in the decrease of the conductivity of the battery, and ultimately leading to the decrease of the low temperature cycle performance of the battery; in addition, during the first charging process of the lithium ion battery, a solid electrolyte interface film (SEI) will be formed on the surface of the negative electrode, which will consume a part of the active lithium in the positive electrode, resulting in the decrease of the first coulomb efficiency.

[0004] Therefore, it is urgent to develop a lithium ion battery with high energy density, high first coulomb efficiency and high low temperature performance. SUMMARY

[0005] To solve or partially solve the problems in related technologies, the present application provides a lithium ion battery and an electronic device, which can have high energy density, high first coulomb efficiency and high low temperature performance.

[0006] The first aspect of the present application provides a lithium ion battery, wherein the lithium ion battery comprises a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode additive; the electrolyte comprises a sulfur-containing additive and 1,3-propane sultone; and the lithium ion battery satisfies the following relationship:

[0007] (X+Y) / (W*A)≥0.025

[0008] In the relationship, the mass percentage content of the sulfur-containing additive in the electrolyte is X%; the mass percentage content of the 1,3-propane sultone in the electrolyte is Y%; the mass percentage content of the positive electrode additive in the positive electrode active material layer is W%; and the specific surface area of the positive electrode additive is A m 2 / g.

[0009] The lithium ion battery as claimed in the preceding paragraph, wherein the lithium ion battery satisfies the following relationship:

[0010] (X+Y) / (W*A)≥0.2.

[0011] The lithium ion battery as claimed in the preceding paragraph, wherein 0.01≤W≤10; and / or, 0.1≤A≤10.

[0012] The lithium ion battery as claimed in the preceding paragraph, wherein A / W≥0.1.

[0013] The lithium ion battery as claimed in the preceding paragraph, wherein 0.5≤X≤4; and / or, 0.5≤Y≤4.

[0014] The lithium ion battery as claimed in the preceding paragraph, wherein X / Y≥0.25.

[0015] The lithium ion battery as claimed in the preceding paragraph, wherein the positive electrode additive comprises at least one of Li2NiO2, Li6CoO4, Li5FeO4, Li2MnO3, Li6MnO4, LiMnFePO4, Li2C2O4, Li2O3Ti, LiTi2(PO4)3, LiLaTiO4, LiTaO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3.

[0016] The lithium ion battery as claimed in the preceding paragraph, wherein the sulfur-containing additive comprises at least one of the compounds shown in Formulas 1-12:

[0017]

[0018]

[0019] The lithium ion battery as claimed in the preceding paragraph, wherein the positive electrode active material layer further comprises a positive electrode active material, the chemical formula of the positive electrode active material being LiNi a Co b Mn (1-a-b) M c O2, wherein 0≤a≤0.9, a+b≤1, 0≤c<0.08, M is at least one of Al, Mg, Zr and Ti.

[0020] The second aspect of the present application provides an electronic device comprising the lithium ion battery as claimed in the preceding paragraph.

[0021] The technical scheme provided in the application can have the following beneficial effects: when (X+Y) / (W*A) is greater than or equal to 0.025, the matching of the positive plate of the lithium ion battery and the electrolyte is better, the positive electrode additive can supplement lithium for the lithium ion battery, improve the first coulomb efficiency of the lithium ion battery, and the side reaction between the positive electrode additive and the positive electrode active material is less, so that the low-temperature and high-temperature cycle performances can be better balanced, the sulfur-containing additive and 1,3-propane sulfone can synergistically form a film on the positive electrode additive and the positive electrode active material, further relieve the side reaction between the positive electrode additive and the positive electrode active material, and improve the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery, and the sulfonic acid group of 1,3-propane sulfone can inhibit the generation of acidic substances such as HF, and the CEI film formed by the sulfur-containing additive on the positive electrode side has strong thermal stability, further improving the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery.

[0022] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory and are not restrictive of the application. DETAILED DESCRIPTION

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "and / or," as used herein, refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0024] It should be understood that although the terms "first", "second", "third", etc. can be used in this application to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information without departing from the scope of the application. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0025] In the related art, when a lithium ion battery works in a high-temperature environment, the internal working temperature of the lithium ion battery increases, and the silicon material will expand and contract to a high degree in the process of metal ion insertion and extraction, which deteriorates the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery; when the lithium ion battery works in a low-temperature environment, the viscosity of the electrolyte increases, which slows down the lithium ion migration rate and increases the lithium ion battery interface impedance, which reduces the conductivity of the lithium ion battery, and ultimately leads to the decline of the low-temperature cycle performance of the lithium ion battery; in addition, in the first charging process of the lithium ion battery, the generation of the SEI film on the negative electrode surface will consume a part of the active lithium in the positive electrode, which leads to the reduction of the first coulomb efficiency.

[0026] To solve the above problems, the embodiment of the present application provides a lithium ion battery, which comprises a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode additive; the electrolyte comprises a sulfur-containing additive and 1,3-propane sultone; and the lithium ion battery satisfies the following relationship:

[0027] (X+Y) / (W*A)≥0.025

[0028] In the relationship, the mass percentage of the sulfur-containing additive in the electrolyte is X%; the mass percentage of 1,3-propane sultone in the electrolyte is Y%; the mass percentage of the positive electrode additive in the positive electrode active material layer is W%; and the specific surface area of the positive electrode additive is A m 2 / g.

[0029] It can be understood that, in the present application, the specific surface area of the positive electrode additive refers to the total area of the positive electrode additive per unit mass, and the unit of the specific surface area of the positive electrode additive is m 2 / g, but the present application does not limit the unit of the specific surface area of the positive electrode additive, for example, the unit of the specific surface area of the positive electrode additive can also be cm 2 / g, etc., when the unit of the specific surface area of the positive electrode additive is other than m 2 / g, the unit is converted into m 2 / g, and the obtained formula value is greater than or equal to 0.025, which is also within the protection scope of the present application.

[0030] The lithium ion battery of the present application comprises a positive electrode sheet, which comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a positive electrode additive, a conductive agent and a binder, and the positive electrode current collector is generally an aluminum foil. The present application does not limit the selection of the positive electrode active material, which can be selected according to actual needs, for example, a transition metal oxide of lithium can be used as the positive electrode active material. The present application does not limit the selection of the positive electrode additive, as long as the positive electrode additive can compensate for the consumed active lithium of the lithium ion battery, which can be selected according to actual needs, for example, a lithium supplementing agent such as Li2NiO2 can be selected. The conductive agent and the binder in the positive electrode active material layer of the present application can be selected from conventional materials in the art.

[0031] The lithium ion battery of the present application comprises an electrolyte, which comprises a sulfur-containing additive and 1,3-propanesulfonic acid lactone, wherein the sulfur-containing additive refers to an additive containing sulfur elements.

[0032] According to the above scheme provided in the application, after the positive plate and the electrolyte are applied to the lithium ion battery, the lithium ion battery has excellent first coulomb efficiency, high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance. The applicant analyzes the principle and believes that the reason is that the first coulomb efficiency, high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance of the lithium ion battery are jointly determined by the positive plate and the electrolyte. The positive electrode additive can supplement lithium for the lithium ion battery and improve the first coulomb efficiency of the lithium ion battery. At the same time, since the conductivity of the positive electrode additive is poorer than that of the positive active material, appropriately increasing the specific surface area of the positive electrode additive can increase the contact area between the electrolyte and the positive electrode additive, so that the transmission channel of lithium ions in the positive electrode additive is more, the low-temperature rate performance of the positive electrode additive is improved, and thus the low-temperature cycle performance of the lithium ion battery is improved. However, during the cycle of the lithium ion battery, the contact between the positive electrode additive and the positive active material is poor, and the electrolyte has differences in film-forming potential and mechanism between the positive electrode additive and the positive active material, which will cause the electrolyte side reaction of the local contact interface between the positive electrode additive and the positive active material to intensify. If the specific surface area of the positive electrode additive or the content of the positive electrode additive increases, the electrolyte contact surface will also increase, and the side reaction between the positive electrode additive and the positive active material will intensify, which will cause the high-temperature performance of the lithium ion battery to deteriorate rapidly. In order to improve the high-temperature performance, the electrolyte of the application adds a sulfur-containing additive and 1,3-propane sulfone. This is because 1,3-propane sulfone can inhibit the generation of acidic substances such as HF to a certain extent during the high-temperature storage process of the lithium ion battery, and the CEI film formed by the sulfur-containing additive on the positive side has strong thermal stability. Therefore, 1,3-propane sulfone and the sulfur-containing additive can effectively cooperate to form a film on the positive electrode additive and the positive active material, relieve the side reaction between the positive electrode additive and the positive active material, and thus improve the high-temperature cycle performance and high-temperature storage gas production of the lithium ion battery.

[0033] It can be understood that X is the mass percentage of the sulfur-containing additive in the electrolyte, Y is the mass percentage of 1,3-propanesultone in the electrolyte, therefore, X+Y refers to the synergistic effect of the sulfur-containing additive and 1,3-propanesultone; W is the mass percentage of the positive electrode additive in the positive electrode active material layer, and A is the specific surface area of the positive electrode additive, therefore, W*A refers to the total specific surface area of the positive electrode additive in the positive electrode active material layer. Therefore, based on experience and experimental findings, the physical meaning of (X+Y) / (W*A) is actually the matching degree of the positive electrode sheet and the electrolyte in the lithium ion battery. When (X+Y) / (W*A)≥0.025, the matching of the positive electrode sheet and the electrolyte in the lithium ion battery is better, the positive electrode additive can supplement lithium for the lithium ion battery, improve the first coulomb efficiency of the lithium ion battery, and at the same time, the positive electrode additive can supplement lithium for the lithium ion battery, improve the first coulomb efficiency of the lithium ion battery, and at the same time, the sulfur-containing additive and 1,3-propanesultone can synergistically form a film on the positive electrode additive and the positive electrode active material, efficiently relieve the side reaction between the positive electrode additive and the positive electrode active material, improve the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery, and the specific surface area of the positive electrode additive is reasonable, the side reaction between the positive electrode additive and the positive electrode active material is less, and the low-temperature and high-temperature cycle performance can be better balanced. If (X+Y) / (W*A)<0.025, the matching of the positive electrode sheet and the electrolyte is unreasonable, the stability of the formed CEI film is poor or the side reaction between the positive electrode additive and the positive electrode active material is more, thereby affecting the high-temperature cycle performance, high-temperature storage performance or low-temperature cycle performance of the lithium ion battery.

[0034] In a specific embodiment, (X+Y) / (W*A)≥0.2. When (X+Y) / (W*A)≥0.2, the matching of the positive electrode sheet and the electrolyte is more reasonable, the side reaction between the positive electrode additive and the positive electrode active material is less, the stability of the CEI film formed by the synergistic effect of the sulfur-containing additive and 1,3-propanesultone is higher, the side reaction between the positive electrode additive and the positive electrode active material can be effectively relieved, and the generation of acidic substances such as HF in the electrolyte can be better inhibited, thereby making the first coulomb efficiency, high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance of the lithium ion battery more optimal.

[0035] In an embodiment, the mass percentage of the positive electrode additive in the positive electrode active material layer is W%, and 0.01≤W≤10, for example, W can be 0.01, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc. When the mass percentage of the positive electrode additive in the positive electrode active material layer is within the above range, the positive electrode additive can effectively supplement lithium for the lithium ion battery, and the side reaction between the positive electrode additive and the positive electrode active material is less, thereby improving the first coulomb efficiency, high-temperature cycle performance and high-temperature storage performance of the lithium ion battery.

[0036] In an embodiment, the specific surface area of the positive electrode additive is A m 2 / g, 0.1≤A≤10, for example, A can be 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc. When the specific surface area of the positive electrode additive is within the above range, the low-temperature rate performance of the positive electrode additive can be improved, while the high-temperature side reaction between the positive electrode additive and the positive electrode active material is avoided, thereby the high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance of the lithium ion battery can be balanced.

[0037] In an embodiment, A / W≥0.1, A / W represents the relative ratio of the specific surface area of the positive electrode additive to the content of the positive electrode additive. If the specific surface area of the positive electrode additive remains unchanged, the higher the content of the positive electrode additive, the worse the cycle performance of the lithium ion battery; if the content of the positive electrode additive remains unchanged, the higher the specific surface area of the positive electrode additive, the better the cycle performance of the lithium ion battery, for example, A / W can be 0.1, 0.2, 0.5, 1, 2, 5 or 10, etc. When the ratio of the specific surface area of the positive electrode additive to the mass percentage of the positive electrode additive is within the above range, the side reaction between the positive electrode additive and the positive electrode active material is less, and the high-specific-surface-area positive electrode additive can improve the low-temperature rate performance of the lithium ion battery, thereby the high-temperature performance and low-temperature performance of the lithium ion battery are well balanced.

[0038] In an embodiment, the mass percentage of the sulfur-containing additive in the electrolyte is X%, and 0.5≤X≤4, for example, X can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4, etc. When the mass percentage of the sulfur-containing additive in the electrolyte is within the above range, the stability of the CEI film formed by the sulfur-containing additive and 1,3-propane sultone is better, and the impedance of the CEI film is lower, which is conducive to alleviating the side reaction between the positive electrode additive and the positive electrode active material, thereby the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery can be effectively improved.

[0039] In an embodiment, the mass fraction of 1,3-propanesultone in the electrolyte is Y%, 0.5≤Y≤4, for example, Y can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4, etc., based on 100% of the mass fraction of the electrolyte. When the mass fraction of 1,3-propanesultone is within the above range, the stability of the CEI film formed by the synergistic effect of the sulfur-containing additive and 1,3-propanesultone is better, and the generation of acidic substances such as HF in the electrolyte can be effectively reduced, while avoiding excessive polarization of the positive electrode caused by excessive impedance of the CEI film formed by 1,3-propanesultone on the positive electrode side, and avoiding the deterioration of the high-temperature and low-temperature cycle performance of the lithium ion battery.

[0040] In an embodiment, X / Y≥0.25, X / Y represents the ratio of the mass content of the sulfur-containing additive to the mass content of 1,3-propanesultone, for example, X / Y can be 0.25, 0.3, 0.35, 0.4, 0.5, 1, 2, 5 or 8, etc. Since the impedance of the CEI film formed by 1,3-propanesultone on the positive electrode surface is large, and the impedance of the CEI film formed by the sulfur-containing additive on the positive electrode surface is lower, if the mass content of the sulfur-containing additive is relatively low compared to the mass content of 1,3-propanesultone, the impedance of the CEI film on the positive electrode surface will be high. When the ratio of the mass fraction of the sulfur-containing additive to the mass fraction of 1,3-propanesultone is within the above range, the impedance of the CEI film formed on the positive electrode side is low and the stability is high, thereby effectively alleviating the side reaction of the positive electrode additive and the positive electrode active material, and further improving the high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance of the lithium ion battery.

[0041] In an embodiment, the positive electrode additive includes at least one of Li2NiO2, Li6CoO4, Li5FeO4, Li2MnO3, Li6MnO4, LiMnFePO4, Li2C2O4, Li2O3Ti, LiTi2(PO4)3, LiLaTiO4, LiTaO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3. During the first charging process of the lithium ion battery, a solid electrolyte interface film (SEI) is formed on the negative electrode surface, which consumes a part of the active lithium in the positive electrode, resulting in a decrease in the first coulombic efficiency. When the positive electrode additive is selected from the above compounds, the positive electrode additive is a sacrificial lithium source, which can provide additional lithium ions to compensate for the active lithium consumed in the formation of the SEI film, thereby improving the first coulombic efficiency and energy density of the lithium ion battery. At the same time, the side reaction between these positive electrode additives and the positive electrode active material is less, which can better improve the high-temperature cycle performance, high-temperature storage performance and low-temperature cycle performance of the lithium ion battery.

[0042] In one specific embodiment, the sulfur-containing additive includes at least one of the compounds shown in Formulas 1-12:

[0043]

[0044] The sulfur-containing additive of the present application includes a five-membered cyclic carbonate group, a five-membered cyclic sulfate group, a six-membered cyclic carbonate group, or a six-membered cyclic sulfate group, and the sulfur-containing additive includes at least one cyclic sulfate group, and the sulfate group or carbonate group in the sulfur-containing additive can participate in the formation of an interfacial film, improving the stability of the interfacial film. When the sulfur-containing additive is selected from the above-mentioned compounds, the sulfur-containing additive and 1,3-propanesultone can better synergize to generate a CEI film with higher stability, thereby better mitigating the side reaction between the positive electrode additive and the positive active material, and further improving the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery to a greater extent.

[0045] In one specific embodiment, the electrolyte further includes an electrolyte salt, and the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorodicyanophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorophosphate; the molar concentration of the electrolyte salt in the electrolyte is 0.4-2.2 mol / L, for example, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L, or 2.2 mol / L, etc. When the electrolyte salt is selected and the molar concentration is within the above-mentioned range, the conductivity and stability of the electrolyte can be further improved, thereby further improving the first coulombic efficiency, high-temperature cycle performance, high-temperature storage performance, and low-temperature cycle performance of the lithium ion battery.

[0046] In an embodiment, the electrolyte further comprises an organic solvent, and the organic solvent comprises at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, propyl acetate, ethyl butyrate, propyl propionate, γ-butyrolactone, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. When the organic solvent of the electrolyte is selected from the above-mentioned organic solvents, the electrolyte has a lower viscosity and a higher ionic conductivity, which is beneficial to improving the migration rate of lithium ions, thereby improving the high and low temperature cycle performance of the lithium ion battery, and the above-mentioned organic solvents can improve the stability of the electrolyte, avoid decomposition reaction of the electrolyte, and further improve the high temperature storage performance of the lithium ion battery.

[0047] In an embodiment, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode active material, and the chemical formula of the positive electrode active material is LiNi a Co b Mn (1-a-b) M c O2, wherein 0≤a≤0.9, a+b≤1, 0≤c<0.08, and M is at least one of Al, Mg, Zr, and Ti. When the positive electrode active material is selected from the above-mentioned compounds, the positive electrode active material can fully exert its performance, thereby improving the electrochemical performance of the lithium ion battery, and the side reaction between the positive electrode active material and the positive electrode additive is low, which can improve the high temperature cycle performance, high temperature storage performance, and low temperature cycle performance of the lithium ion battery.

[0048] In the embodiments, the type of the positive electrode current collector is not particularly limited, and it can be any known material suitable for use as a positive electrode current collector. In an embodiment, the positive electrode current collector comprises metal materials such as aluminum, stainless steel, nickel plating layer, titanium, tantalum, and carbon materials such as carbon cloth and carbon paper. Preferably, the positive electrode current collector is a metal material.

[0049] In an embodiment, the positive electrode active material layer further comprises a conductive agent and a binder. The conductive agent comprises at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The binder comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0050] In an embodiment, the lithium ion battery further comprises a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer disposed on a surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, a conductive agent, and a binder. The negative electrode current collector is not particularly limited as long as it can achieve the purpose of the present application, and can be, for example, a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, or a composite current collector. The negative electrode active material is selected from at least one of graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon particles, and a lithium-containing metal composite oxide material.

[0051] The conductive agent and the binder in the negative electrode active material layer of the embodiment of the present application can be conventional materials in the art.

[0052] In an embodiment, the lithium ion battery further comprises a separator. The material and shape of the separator are not particularly limited as long as they do not significantly impair the effects of the present application. The material of the resin or glass fiber separator can include, but is not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyether sulfone, and the like. The shape of the separator can be a porous sheet or a non-woven fabric, and the like.

[0053] In an embodiment, the lithium ion battery can comprise an outer package for packaging the electrode assembly and the electrolyte.

[0054] In an embodiment, the outer package of the lithium ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and examples of the plastic can include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

[0055] The shape of the secondary battery is not particularly limited, and the secondary battery can have a cylindrical shape, a square shape, or any other shape.

[0056] The embodiment of the present application also provides an electronic device comprising the lithium ion battery described above. The electronic device has advantages corresponding to the lithium ion battery described above, and will not be described again.

[0057] The electronic device of the embodiment of the present application can be a conventional electronic device in the art. For example, the electronic device can include a mobile device (such as a mobile phone, a notebook computer, or the like), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, or the like), an electric train, a ship, a satellite, an energy storage system, or the like.

[0058] The present application will be further described in detail below through specific embodiments.

[0059] Example 1

[0060] 1. Preparation of positive electrode sheet

[0061] The positive electrode active material LiCoO2, the positive electrode additive Li2NiO2, the conductive agent acetylene black (Super P) and the polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 96.5:0.5:1.5:1.5 and uniformly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform black slurry. The mixed slurry was coated on both sides of the aluminum foil current collector, and then baked, rolled, cut and sheeted to obtain the positive electrode sheet. The coating surface density of the positive electrode active material layer and the mass percentage of the positive electrode additive in the positive electrode active material layer are shown in Table 1.

[0062] 2. Preparation of negative electrode sheet

[0063] The negative electrode active material graphite and silicon-carbon particles (mass ratio of 9:1), the conductive agent acetylene black (Super P), the thickening agent CMC and the binder SBR were mixed in a mass ratio of 94:2:1.2:2.8 and uniformly dispersed in deionized water to form a uniform black slurry. The mixed slurry was coated on both sides of the aluminum foil current collector, and then baked, rolled, cut and sheeted to obtain the negative electrode sheet.

[0064] 3. Preparation of electrolyte

[0065] a. The mixed solvent was prepared by mixing and stirring ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP) and diethyl carbonate (DEC) in a mass ratio of 10:20:40:30, and then removing water with molecular sieves. Then, 1M lithium hexafluorophosphate (LiPF6) was added and mixed uniformly.

[0066] b. The colorless transparent liquid obtained in step a was added with sulfur-containing additives and additive Y (the types and amounts of the additives are shown in Table 1) to obtain the electrolyte of each example and comparative example.

[0067] 4. Preparation of lithium ion battery

[0068] The positive electrode sheet, the separator and the negative electrode sheet were stacked in order, with the separator between the positive and negative electrodes to play a separating role, and then wound to obtain a bare cell. The bare cell was placed in an outer packaging bag, dried at high temperature until the water content of the electrode sheet was less than 100 ppm, and then injected with the prepared electrolyte. After vacuum packaging, standing, formation and shaping, the preparation of the lithium ion battery was completed.

[0069] The preparation method of the lithium ion battery provided in Examples 2-48 and Comparative Examples 1-27 is basically the same as that of Example 1, and the specific parameters are shown in Table 1.

[0070] Table 1

[0071]

[0072]

[0073]

[0074]

[0075] Test Example

[0076] Lithium ion battery performance test:

[0077] 1. First coulombic efficiency test:

[0078] After the lithium ion battery is completed, it is placed at room temperature for 48H, and the lithium ion battery is charged to 4.53V at 0.3C rate, the cutoff current is 0.05C, the charge capacity C0 is recorded, and the lithium ion battery is placed for 10min; then discharged to 3.0V at 0.2C rate, record the discharge capacity C1. First efficiency = C1 / C0*100%, take the average value recorded in Table 2.

[0079] 2. 45℃ cycle test:

[0080] The test method is: in a 45±2℃ constant temperature box, the lithium ion battery is charged to 4.53V at 1C constant current and constant voltage, the cutoff current is 0.05C, and then discharged to 3V at 1C, and the above conditions are repeated for multiple charge and discharge cycles, and the capacity retention rate after 600 cycles of the battery is calculated, and each group has 5 batteries.

[0081] Capacity retention rate (%) = discharge capacity (mAh) corresponding to cycle number / third week cycle discharge capacity (mAh)*100%

[0082] The capacity retention rate of each group of 5 batteries after different cycle times is recorded in Table 2.

[0083] 3. 0℃ cycle test:

[0084] The test method is: in a 0±2℃ constant temperature box, the lithium ion battery is charged to 4.53V at 1C constant current and constant voltage, the cutoff current is 0.05C, and then discharged to 3V at 1C, and the above conditions are repeated for multiple charge and discharge cycles, and the capacity retention rate after 600 cycles of the battery is calculated, and each group has 5 batteries.

[0085] Capacity retention rate (%) = discharge capacity (mAh) corresponding to cycle number / third week cycle discharge capacity (mAh)*100%

[0086] The capacity retention rate of each group of 5 batteries after different cycle times is recorded in Table 2.

[0087] 4. 60℃ storage performance test:

[0088] The test method is as follows: the lithium ion battery is charged to 4.53 V at 1C in a 25±2℃ constant temperature box, and the cutoff current is 0.05C. The thickness of the lithium ion battery (as the thickness before storage) is tested. The fully charged cell / battery is left to stand open circuit at (60±2)℃ for 35 days, and after 35 days of storage, it is left to stand open circuit at room temperature for 2h. The thickness after storage is tested, and the thickness expansion rate of the lithium ion battery is calculated:

[0089] The thickness expansion rate = [(thickness after storage-thickness before storage) / thickness before storage]x100%, and the results are recorded in Table 2.

[0090] Table 2

[0091]

[0092]

[0093]

[0094] According to the comparison of Examples 1-48 and Comparative Example 27, when the total amount of the sulfur-containing additive and PS (1,3-propanesulfone) is too low relative to the positive electrode additive and specific surface area content, the side reaction of the positive electrode additive interface cannot be improved. Therefore, it is necessary to meet: (X+Y) / (W*A)≥0.025, and the comprehensive performance of the lithium ion battery is relatively good. According to the comparison of Examples 1-44 and Examples 45-48, when (X+Y) / (W*A)≥0.2, the comprehensive performance of the lithium ion battery is better.

[0095] According to the comparison of Example 4, Example 12 and Comparative Examples 1-6, when the positive electrode additive, the sulfur-containing additive and PS synergistically act in the lithium ion battery, the lithium ion battery can have high initial coulombic efficiency, high low-temperature cycle performance and high-temperature storage performance.

[0096] According to the comparison of examples 11-16, with the increase of the content of the positive electrode additive, the first coulombic efficiency of the lithium ion battery is improved, and the high and low temperature cycle performance and high temperature storage performance of the lithium ion battery are deteriorated. According to the data of examples 17-22, with the increase of the specific surface area of the positive electrode additive, the low temperature cycle performance of the lithium ion battery is improved, the first efficiency has no obvious change, and the high temperature cycle is deteriorated. When the positive electrode active material is highly delithiated, the positive electrode additive can be used as a lithium source to supplement lithium, improve the first efficiency and capacity of the lithium ion battery. However, during the cycle of the electrochemical device, the contact between the positive electrode additive and the positive electrode active material is poor, and the electrolyte has differences in the film-forming potential and mechanism between the positive electrode additive and the positive electrode active material, which will cause the electrolyte side reaction of the local contact interface between the two materials to be intensified. When the specific surface area of the positive electrode additive increases, the electrolyte contact surface will also increase. Therefore, when the proportion of the positive electrode additive in the positive electrode active material layer and the specific surface area increase, the side reaction between the positive electrode additive and the positive electrode active material will be intensified. The conductivity of the positive electrode additive itself is poorer than that of the positive electrode active material, so increasing the specific surface area of the positive electrode material can improve the low temperature rate performance of the positive electrode additive, but too high specific surface area will intensify the high temperature side reaction, so the specific surface area of the positive electrode additive and the content of the positive electrode additive need to be in a certain range to better balance the low temperature and high temperature cycle performance. According to the comparison of examples 11-22 and comparative examples 21-22, comparative examples 25-26, when 0.01≤W≤10, 0.1≤A≤10, A / W≥0.1, the comprehensive performance of the lithium ion battery is relatively good. According to the comparison of example 4 and examples 34-44, when the positive electrode additive is selected from the above compounds, the lithium ion battery can have the first coulombic efficiency, high and low temperature cycle performance and high temperature storage performance.

[0097] The sulfur-containing additive and the additive 1,3-propane sultone can effectively synergize on the positive electrode additive and the positive electrode active material to form a film, alleviate the side reaction between the positive electrode material and the positive electrode active material, and thus improve the high-temperature cycle performance and the high-temperature storage gas production of the lithium ion battery. When the total amount of the sulfur-containing additive and the additive 1,3-propane sultone is within a certain range relative to the content and specific surface area of the positive electrode additive, the low-temperature and high-temperature performance can be well balanced. During the high-temperature storage process of the lithium ion battery, the sulfonic acid group of 1,3-propane sultone can inhibit the generation of HF to some extent, thereby improving the storage gas production. On the other hand, the CEI film formed by the sulfur-containing additive on the positive electrode side has strong thermal stability, so the synergistic effect of 1,3-propane sultone and the sulfur-containing additive can effectively improve the high-temperature storage performance of the lithium ion battery. However, the film formed by 1,3-propane sultone on the positive electrode side has high impedance, and a high content of 1,3-propane sultone can easily lead to excessive polarization of the positive electrode, thereby deteriorating the high-low temperature cycle performance. On the other hand, the CEI film formed by the sulfur-containing additive on the positive electrode side has low impedance, and when the content of 1,3-propane sultone decreases and the content of the sulfur-containing additive increases under the same total amount of the two, the high-temperature cycle is improved. According to the comparison of Examples 1 to 4, as the content of the sulfur-containing additive increases, the cycle performance and the storage performance of the lithium ion battery are improved. According to the comparison of Examples 7 to 10, as the content of 1,3-propane sultone increases, the cycle performance of the lithium ion battery deteriorates, but the high-temperature storage performance is improved. According to the comparison of Example 12 and Comparative Examples 2, 7 to 9, 12, 14 to 16, 19 to 20, and the comparison of Example 4 and Comparative Examples 3, 10 to 11, 13, 17 to 18, the synergistic effect of the sulfur-containing additive and PS is good only when they are used together, and the content of the additive should not be too high, otherwise the viscosity of the electrolyte will increase and the impedance will increase. According to Examples 5 to 6, when the total amount of the additive is unchanged, increasing the content of the sulfur-containing additive and reducing the content of PS can improve the cycle performance of the lithium ion battery, and slightly deteriorate the storage performance. According to Examples 4, 7 to 10, and Comparative Examples 23 to 24, the content of the sulfur-containing additive relative to the content of PS needs to be within a certain range to effectively improve the deterioration of the PS on the positive electrode impedance. The following relationships are met: 0.5≤X≤4, 0.5≤Y≤4, and X / Y≥0.25, and the comprehensive performance of the lithium ion battery is relatively good. According to the comparison of Example 5 and Examples 24 to 34, when the sulfur-containing additive is selected from the compounds shown in Formulas 1 to 12, the sulfur-containing additive and PS can synergize to improve the comprehensive performance of the lithium ion battery.

[0098] Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only, and that many modifications and variations of the embodiments described herein are possible. It is therefore to be understood that within the scope of the appended claims, and their equivalents, many alternatives to the embodiments described herein are possible. The selection of terms to be used in the description is not intended to limit the scope of the embodiments described herein, but rather to best explain the principles of the embodiments, practical application, or improvement over the technology in the art, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A lithium-ion battery, characterized in that, The battery includes a positive electrode and an electrolyte; the positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive additive; the electrolyte includes a sulfur-containing additive and 1,3-propanesulfonate lactone; the lithium-ion battery satisfies the following relationship: (X+Y) / (W×A)≥0.025 In the formula, the mass percentage of the sulfur-containing additive in the electrolyte is X; the mass percentage of the 1,3-propanesulfonic acid lactone in the electrolyte is Y; the mass percentage of the positive electrode additive in the positive electrode active material layer is W; and the specific surface area of ​​the positive electrode additive is Am. 2 / g; the positive electrode additives include Li2NiO2, Li6CoO4, Li5FeO4, Li2MnO3, Li6MnO4, LiMnFePO4, Li2C2O4, Li2O3Ti, LiTi2(PO4)3, LiLaTiO4, LiTaO3, Li 1.5 Al 0.5 Ge 1.5 At least one of (PO4)3; the sulfur-containing additive includes at least one of the compounds shown in Formulas 1 to 12:

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies the following relationship: (X+Y) / (W×A)≥0.

2.

3. The lithium-ion battery according to claim 1, characterized in that, 0.01≤W≤10; and / or, 0.1≤A≤10.

4. The lithium-ion battery according to claim 1 or 3, characterized in that, A / W ≥ 0.

1.

5. The lithium-ion battery according to claim 1, characterized in that, 0.5≤X≤4; and / or, 0.5≤Y≤4.

6. The lithium-ion battery according to claim 1 or 5, characterized in that, X / Y ≥ 0.

25.

7. The lithium-ion battery according to claim 1, characterized in that, The positive electrode active material layer further includes a positive electrode active material, the chemical formula of which is LiNi. a Co b Mn (1-a-b) M c O2, where 0≤a≤0.9, a+b≤1, 0≤c<0.08, and M is at least one of Al, Mg, Zr and Ti.

8. An electronic device, characterized in that, Including the lithium-ion battery according to any one of claims 1-7.

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