Lithium-ion battery

Abstract

The present invention relates to the technical field of batteries, and in particular to a lithium-ion battery. 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 located on one side surface or two side surfaces of the positive electrode current collector; the positive electrode active material layer comprises a positive electrode active material; W is the peak intensity ratio of (003) crystal plane to (104) crystal plane in the positive electrode active material; and X is the peak intensity ratio of (006) crystal plane to (104) crystal plane in the positive electrode active material. The electrolyte comprises a phosphate additive; and based on the total weight of the electrolyte, the weight content of the phosphate additive is dwt%. The lithium-ion battery meets the following relations: 0.033≤d / W≤0.4 and 0.67≤d / x≤6.5. The battery has the advantages of good high-temperature cycle performance, good storage performance and high safety performance.

Description

lithium-ion batteries Technical Field

[0001] The present disclosure relates to the technical field of batteries, and in particular to a lithium-ion battery.

[0002] Background of the Invention

[0003] Lithium-ion batteries offer advantages such as high energy storage density, high open-circuit voltage, low self-discharge rate, long cycle life, and excellent safety. They are widely used in various fields, including portable energy storage, electronic devices, and electric vehicles. However, these batteries also place higher demands on their overall performance, such as high energy density, good high-temperature storage performance, and good cycling performance. However, with high energy density comes a decrease in high-temperature storage performance and cycling performance.

[0004] Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present disclosure provides a lithium-ion battery with good high-temperature cycle performance, good storage performance and high safety performance.

[0006] In order to achieve the above-mentioned object, the present disclosure provides a lithium-ion battery, wherein the lithium-ion battery comprises a positive electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on one side or both sides of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, W is the peak intensity ratio of the (003) crystal plane to the (104) crystal plane in the positive electrode active material, and X is the peak intensity ratio of the (006) crystal plane to the 104 crystal plane in the positive electrode active material; the electrolyte comprises a phosphate additive, and the weight content of the phosphate additive is dwt% based on the total weight of the electrolyte, then the lithium-ion battery satisfies the following relationship: 0.033≤d / W≤0.4 and 0.67≤d / X≤6.5.

[0007] Through the above technical solution, the present disclosure has at least the following advantages compared with the prior art:

[0008] The lithium-ion battery disclosed in the present invention can improve the Li+ / Li+ phase separation caused by the mixed arrangement of nickel and lithium in the ternary material by satisfying the following conditions: 0.033≤d / W≤0.4 and 0.67≤d / X≤6.5. + It can not only solve the problem of reduced migration rate, but also enhance the mechanical properties of the positive electrode interface, avoid the structural collapse of the ternary material, and improve the structural stability of the positive electrode active material, so that the battery has the advantages of good high-temperature cycle performance, good storage performance and high safety performance.

[0009] Other features and advantages of the present disclosure will be described in detail in the following detailed description.

[0010] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG1 shows an XRD spectrum of the positive electrode active material in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0012] The following is a detailed description of the specific embodiments of the present disclosure. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure. In this article, unless otherwise specified, data ranges include endpoints.

[0013] It should be noted that the numerical expressions such as "first" and "second" in this disclosure are only used to distinguish different substances or usage methods, and do not represent a difference in order.

[0014] The present disclosure provides a lithium-ion battery, comprising a positive electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on one side or both sides of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, W is the peak intensity ratio of the (003) crystal plane to the (104) crystal plane in the positive electrode active material, and X is the peak intensity ratio of the (006) crystal plane to the (104) crystal plane in the positive electrode active material; the electrolyte comprises a phosphate additive, and the weight content of the phosphate additive is dwt% based on the total weight of the electrolyte, then the lithium-ion battery satisfies the following relationship: 0.033≤d / W≤0.4 and 0.67≤d / X≤6.5.

[0015] The battery may satisfy the following relationship: 0.033≤d / W≤0.4 (e.g., 0.033, 0.035, 0.05, 0.07, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4) and 0.67≤d / X≤6.5 (e.g., 0.67, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5).

[0016] Although ternary materials have high energy density, the inherent nickel-lithium mixed arrangement will hinder the Li + The migration of ternary materials and the structural collapse of ternary materials during accelerated battery cycling result in poor high-temperature cycling performance and storage performance of lithium-ion batteries.

[0017] When the lithium-ion battery satisfies 0.033≤d / W≤0.4 and 0.67≤d / X≤6.5, the dissolution of metal ions in the positive electrode material can be reduced, and the electrolyte includes a phosphate additive, the phosphate additive has a higher HOMO energy level, the higher the HOMO energy level, the easier it is to be oxidized, so that it can be preferentially oxidized at the interface layer of the positive electrode to form a protective film with excellent mechanical properties, the protective film can inhibit the occurrence of nickel-lithium mixed arrangement of the ternary material, reduce the degree of damage to the crystal structure of the ternary material, thereby avoiding Li + The migration of lithium ions is hindered, thereby improving the high-temperature cycle stability of the battery. At the same time, during the repeated charge and discharge process, the protective film can also inhibit the continuous expansion and contraction of the unit cell of the ternary material due to the insertion and extraction of lithium ions, causing the positive electrode active material particle structure to break and pulverize, avoiding the increase in battery internal resistance due to poor contact between the positive electrode active particles, reducing the side reaction between the positive electrode sheet and the electrolyte, and improving the battery's cycle performance. Moreover, the protective film has good heat resistance and can maintain high stability under conditions of thermal abuse, avoiding the accelerated decomposition and gas production of the electrolyte under thermal abuse, and improving the battery's storage performance and safety performance. In addition, the phosphate additives in the electrolyte can significantly reduce the oxidation activity of the positive electrode active material in the delithiation state, thereby reducing the oxidative decomposition of the electrolyte and improving the battery's cycle performance and safety performance.

[0018] In the present disclosure, by controlling the relationship between the electrolyte and the positive electrode active material in the lithium-ion battery, the lithium-ion battery has higher cycle performance, better storage performance and higher safety performance. To further improve the effect, one or more of the technical features can be further optimized.

[0019] The diffraction peak intensity of the positive electrode active material can satisfy the following relationship: 1.2≤W≤3 (for example, 1.2, 1.5, 1.7, 2, 2.2, 2.5, 2.7, 3), 0.02≤X≤0.15 (for example, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15), 0.06≤Y≤0.15 (for example, 0.06, 0.08, 1, 0.12, 0.15), wherein Y is the peak intensity ratio of the (006) crystal plane to the (104) crystal plane in the positive electrode active material. The positive electrode active material with W satisfying the above range is more stable, can reduce the degree of lithium-nickel mixing, thereby reducing the damage to the layered structure. At the same time, limiting X and Y within the above range can avoid the shrinkage of the interlayer spacing of the crystal plane, and ensure that the integrity of the positive electrode active material structure and the crystal structure are not damaged.

[0020] Among them, in the XRD spectrum of the positive electrode material, the (003) crystal plane is located at 16°-20°, the (006) crystal plane is located at 36°-39°, and the (104) crystal plane is located at 42°-45°.

[0021] In one embodiment, the electrolyte includes ethylene carbonate, propylene carbonate, and diethyl carbonate. When the electrolyte includes the carbonate esters, the dissociation degree of the lithium salt can be increased, the transference number of lithium ions can be increased, and the low-temperature performance of the battery can be improved.

[0022] In one example, based on the total weight of the electrolyte, the weight content of ethylene carbonate is awt%, the weight content of propylene carbonate is cwt%, and the weight content of diethyl carbonate is bwt%, then the electrolyte satisfies the following relationship: 0.1<a / c<0.8, and / or; 45≤(a+c) / d≤300, and / or; 150≤b / d≤500.

[0023] In one example, the electrolyte satisfies the following relationship: 0.1<a / c<0.8 (for example, 0.11, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.79), and 45≤(a+c) / d≤300 (for example, 45, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300), and 150≤b / d≤500 (for example, 150, 200, 250, 300, 350, 400, 450, 500).

[0024] When the electrolyte satisfies the above relationship, the viscosity of diethyl carbonate in the electrolyte is low, which can reduce the migration impedance of lithium ions and further reduce the Li ion caused by the mixed arrangement of nickel and lithium in the ternary material. + The migration rate is reduced. At the same time, diethyl carbonate has good high-temperature stability, which can reduce the side reaction between the positive electrode and the electrolyte during the full charge process and improve the cycle stability of the battery; both ethylene carbonate and propylene carbonate in the electrolyte can form a good solvation effect with the lithium salt, and the content of ethylene carbonate is limited to be lower than that of propylene carbonate, which can improve the stability of the ternary material in the electrolyte and increase the concentration of lithium salt around ethylene carbonate, thereby improving the high-temperature cycle performance of the battery.

[0025] In one embodiment, 30≤a+c≤50 (eg, 30, 32, 35, 38, 40, 42, 45, 48, 50). When a+c satisfies the above range, the conductivity of the electrolyte can be increased, and the high-rate cycle charge-discharge performance can be improved.

[0026] According to a specific embodiment, bwt% is 30wt%-70wt% (e.g., 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%). The above range of diethyl carbonate is used in combination with ethylene carbonate and propylene carbonate to achieve both high temperature resistance and safety performance of the battery.

[0027] In one embodiment, bwt% is 40wt%-65wt%.

[0028] According to a specific embodiment, the dwt% is 0.1wt%-1wt% (e.g., 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%). The phosphate additive within the above range can undergo an electrochemical redox reaction at the positive and negative electrode interfaces to form a polymer. The polymer has high thermal stability and can improve the high-temperature cycling stability of the battery.

[0029] In one example, the dwt% is 0.3wt%-0.7wt%.

[0030] In one embodiment, the electrolyte satisfies the following relationship: 0.1<a / c<0.8, and 45≤(a+c) / d≤300, and 150≤b / d≤500, and 30≤a+c≤50, and bwt% is 30wt%-70wt%, and dwt% is 0.1wt%-1wt%. Through the combination of electrolyte solvent and additives, the cyclic carbonate has a high dielectric constant, while the linear carbonate has a uniform electron cloud density distribution and good high-temperature thermal stability. The additive forms an interface film at the positive and negative electrodes, preventing the solvent from directly contacting the positive and negative active materials, which would otherwise cause redox decomposition of the solvent. The three synergistically enable the battery to simultaneously take into account high and low temperature cycle performance.

[0031] In one embodiment, the phosphate additive includes a structure represented by formula (I),

[0032] Among them, R1, R2, and R3 can be the same or different, and are independently selected from substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups, and at least one of R1, R2, and R3 is selected from substituted or unsubstituted C2-C5 unsaturated hydrocarbon groups.

[0033] The substituted or unsubstituted C2-C5 unsaturated hydrocarbon group includes a substituted or unsubstituted C2-C5 olefin group and / or a substituted or unsubstituted C2-C5 alkynyl group.

[0034] At least one of R1, R2, and R3 is selected from a substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, and the number of unsaturated hydrocarbon groups in R1, R2, and R3 can be 1, 2, or 3. In this case, the HOMO energy level of the phosphate ester additive can be increased, while the electron cloud density of the unsaturated bond is greater and the LUMO energy level of the phosphate ester additive is lower, which is conducive to the preferential electrochemical redox reaction of the phosphate ester additive to form an electrode interface protective layer. The interface protective layer formed by the phosphate ester additive is also more stable, which can further inhibit the occurrence of nickel-lithium mixed arrangement in the ternary material.

[0035] In the present disclosure, the expression "substituted or unsubstituted" means, for example, "substituted or unsubstituted C1-C5 alkyl", which means that the alkyl group may be substituted or not substituted by any substituent. When the alkyl group is substituted by a substituent, one H group in the alkyl group may be substituted, multiple H groups may be substituted, or all H groups may be substituted.

[0036] The substituted substituents may be selected from halogen.

[0037] In one example, the halogen includes one or more of F, Cl, Br and I.

[0038] In one embodiment, the halogen is F.

[0039] C1-C5 alkyl, for example, is selected from methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, cyclopentyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl.

[0040] C2~C5 olefin groups, for example, are selected from vinyl, n-propenyl, isopropenyl, cyclopropenyl, n-butenyl, isobutenyl, sec-butenyl, tert-butenyl, cyclobutenyl, n-pentenyl, isopentenyl, tert-pentenyl, neopentenyl, cyclopentenyl, 2,2-dimethylpropenyl, 1-ethylpropenyl, 1-methylbutenyl, and 2-methylbutenyl.

[0041] C2-C5 alkynyl, for example, selected from ethynyl, n-propynyl, isopropynyl, cyclopropynyl, n-butynyl, isobutynyl, sec-butynyl, tert-butynyl, cyclobutynyl, n-pentynyl, isopentenyl, tert-pentynyl, neopentynyl, cyclopentynyl, 2,2-dimethylpropynyl, 1-ethylpropynyl, 1-methylbutynyl, 2-methylbutynyl.

[0042] In one embodiment, the phosphate additive includes one or more of the following structures:

[0043] In one embodiment, the electrolyte includes a sultone compound, and the sultone compound includes a structure represented by formula (II),

[0044] Wherein, R4, R5, and R6 may be the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C1-C5 alkyl, and the substituted substituent is halogen.

[0045] The bond energy of the sulfur-oxygen bond in the sultone compound is relatively small. In the electrochemical reaction, oxidation bond breaking easily occurs to form an interface film containing lithium sulfite (Li2SO3) at the positive electrode interface, thereby enhancing the mechanical properties of the interface and avoiding the collapse of the layered structure of the ternary material. At the same time, the sultone compound in the electrolyte can form a protective film rich in sulfonic acid groups on the surface of the positive electrode sheet. The sulfonic acid group has good tolerance to high temperatures. Therefore, adding the sultone compound to the electrolyte can further reduce the side reactions between the positive electrode sheet and the electrolyte at high temperatures, thereby further improving the high-temperature cycle performance of the battery.

[0046] In the structure represented by formula (II), the dotted line in the five-membered ring represents a single bond, which may or may not exist. When the single bond exists, it indicates that the sultone compound includes a five-membered alkene ring, and the sultone compound has structures such as (II-6), (II-7), (II-8), (II-9), and (II-10). When the single bond does not exist, it indicates that the sultone compound includes a five-membered alkane ring, and the sultone compound has structures such as (II-1), (II-2), (II-3), (II-4), and (II-5).

[0047] The halogen may include one or more of F, Cl, Br and I.

[0048] In one embodiment, the sultone compound includes one or more of the following structures:

[0049] According to a specific embodiment, the weight ratio of the sultone compound to the phosphate additive is (0.01-50):1 (e.g., 0.01:1, 0.05:1, 0.1:1, 0.5:1, 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1). When the weight ratio of the sultone compound to the phosphate additive is limited to the above range, the phosphate protective film and the sulfonate protective film formed at the interface of the positive electrode sheet can act synergistically to further improve the structural stability of the ternary material, thereby further improving the high-temperature cycling stability, storage performance, and safety performance of the battery.

[0050] In one example, the weight ratio of the sultone compound to the phosphate additive is (0.5-10):1.

[0051] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the sultone compound is 0.01wt%-10wt% (for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%). When the content of the sultone compound in the electrolyte exceeds 10wt%, the protective film formed by the sultone compound will hinder the transmission of lithium ions, increase the interface impedance of the positive electrode sheet, and thus increase the impedance of the battery. When the content of the sultone compound in the electrolyte is less than 0.01wt%, the high temperature resistance of the protective film formed by the sultone compound is not obvious, thereby causing the high temperature cycle performance of the battery to be low. When the content of the sultone compound in the electrolyte is limited to the above range, the high temperature resistance and low impedance of the protective film can be exerted at the same time, so that the battery has the advantages of low impedance and good high temperature cycle performance.

[0052] In one embodiment, based on the total weight of the electrolyte, the weight content of the sultone compound is 0.25 wt % to 3 wt %.

[0053] In one embodiment, the electrolyte includes ethyl methyl carbonate. When the electrolyte includes ethyl methyl carbonate (EMC), the low-temperature kinetic performance of the battery can be improved, thereby enabling the battery to have both high and low temperature cycle stability.

[0054] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the ethyl methyl carbonate is 0wt%-75wt% (for example, 0wt%, 0.1wt%, 0.5wt%, 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%). When the weight content of the ethyl methyl carbonate in the electrolyte is 0wt%, it means that there is no ethyl methyl carbonate in the electrolyte.

[0055] In one embodiment, based on the total weight of the electrolyte, the weight content of the ethyl methyl carbonate is 0 wt%-40 wt%.

[0056] In one example, the electrolyte includes an electrolyte lithium salt, a first additive, and a second additive.

[0057] In one example, the electrolyte lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonyl imide (LiN(CF3SO2)2 (abbreviated as LiTFSI)), lithium bistrifluorosulfonyl imide (Li(N(SO2F)2) (abbreviated as LiFSI)), lithium difluorobisoxalate phosphate (LiPF2(C2O4)2), lithium tetrafluorooxalate phosphate, lithium tetrafluorooxalate (LiPF4C2O4), lithium hexafluorocesium oxide (LiCsF6) and lithium trifluoromethanesulfonate.

[0058] In one example, based on the total weight of the electrolyte lithium salt, the weight content of the lithium hexafluorophosphate is greater than 50 wt %.

[0059] In one example, the first additive includes one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and fluoroethylene carbonate (FEC).

[0060] In one embodiment, the second additive includes one or more of diethylenetriaminetetradecanoate (DTD), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiODFB), lithium bis(oxalatoborate) (LiBOB), lithium tetrafluoroborate (LiBF4), tris(trimethylsilyl)borate (TMSB), and tris(trimethylsilyl)phosphate (TMSP). These second additives can form an inorganic SEI film with excellent mechanical properties and thermal stability.

[0061] According to a specific embodiment, based on the total weight of the electrolyte, the weight content of the electrolyte lithium salt is 10wt%-20wt% (for example, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%), and the weight content of the first additive is 0.01wt%-5wt% (for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%).

[0062] In one embodiment, the weight content of the second additive is 0.5wt%-6wt% (e.g., 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%) based on the total weight of the electrolyte. When the content of the second additive in the electrolyte is less than 0.5wt%, battery gassing or increased impedance may occur, affecting battery performance. When the content of the second additive in the electrolyte is greater than 6wt%, the inorganic SEI film formed by the second additive may provide insufficient protection for the battery, resulting in poor high-temperature cycling performance of the battery.

[0063] In one example, based on the total weight of the electrolyte, the weight content of the electrolyte lithium salt is 12wt%-16wt%, the weight content of the first additive is 0.5wt%-3wt%, and the weight content of the second additive is 1.5wt%-4.5wt%.

[0064] In one embodiment, the positive electrode active material comprises a ternary layered oxide, wherein the ternary layered oxide comprises a chemical formula of Li a Ni y Mn z Co x A k A ternary layered oxide of O2, wherein 0.9≤a≤1.1, 0.1≤x≤0.4, 0.3≤y≤1, 0≤z≤0.3, 0≤k≤0.05, A is a doping element, and A includes one or more of Al, Mg, Ti and Nb.

[0065] In one example, the positive electrode active material includes Ni, and the transition metal element in the positive electrode material includes one or more of Ni, Mn, and Co.

[0066] In one embodiment, the molar content of Ni is ≥50% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%) based on the total molar amount of transition metal elements in the positive electrode active material. When the molar content of Ni meets the above range, it has a certain impact on the thermal stability of the positive electrode active material. However, by using it together with an electrolyte containing a phosphate additive, the thermal stability of the positive electrode active material can be improved, thereby enhancing the safety and high-temperature cycle performance of the battery.

[0067] In one embodiment, the median particle size Dv50 of the positive electrode active material is 4 μm to 18 μm (e.g., 4 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 18 μm). When the median particle size of the positive electrode active material is less than 4 μm, its specific surface area is large, resulting in more interfacial side reactions. When the median particle size of the positive electrode active material is greater than 18 μm, particles tend to agglomerate into secondary particles, which are easily damaged during battery cycling, forming new interfaces that degrade the battery's high-temperature cycling performance.

[0068] In one example, the median particle size Dv50 of the positive electrode active material is 6 μm-13 μm.

[0069] In one embodiment, the specific surface area of ​​the positive electrode active material is 0.2 m 2 / g-1.5m 2 / g (for example, 0.2m 2 / g, 0.5m 2 / g, 0.7m 2 / g、1m 2 / g, 1.2m 2 / g, 1.5m 2 / g). When the specific surface area of ​​the positive electrode active material is greater than 1.5 m 2 / g, the interface side reaction of the positive electrode active material is more; when the specific surface area of ​​the positive electrode active material is less than 0.2m 2 / g, particles are easily agglomerated into secondary particles.

[0070] In one embodiment, the specific surface area of ​​the positive electrode active material is 0.7 m 2 / g-1.2m 2 / g.

[0071] In one example, the positive electrode active material layer includes a first binder and a first conductive agent.

[0072] In one embodiment, the first binder includes one or more of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinylidene fluoride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon. The first binder can improve the bonding between the positive electrode active materials and the bonding between the positive electrode active material layer and the positive electrode current collector.

[0073] In one example, the first conductive agent includes one or more of a carbon-based material, a metal-based material, and a conductive polymer (eg, a polyphenylene derivative). The first conductive agent may impart conductivity to the electrode.

[0074] In one example, the carbon-based material includes one or more of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber.

[0075] In one example, the metal-based material includes metal powder and / or metal fiber.

[0076] In one example, the metal powder includes one or more of copper, nickel, aluminum, and silver.

[0077] In one example, the positive electrode current collector includes aluminum (Al).

[0078] According to a specific embodiment, based on the total weight of the positive electrode active material layer, the weight content of the positive electrode active material is 93.5wt%-98wt% (for example: 93.5wt%, 94wt%, 95wt%, 95.5wt%, 96wt%, 96.5wt%, 97wt%, 97.5wt%, 98wt%), the weight content of the first binder is 0.5wt%-4.5wt% (for example: 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%), and the weight content of the first conductive agent is 1wt%-5wt% (for example: 1wt%, 2wt%, 3wt%, 4wt%, 5wt%).

[0079] In one example, based on the total weight of the positive electrode active material layer, the weight content of the positive electrode active material is 95wt%-96.5wt%, the weight content of the first binder is 1wt%-2.5wt%, and the weight content of the first conductive agent is 1.5wt%-3wt%.

[0080] In one example, the battery includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer located on one side or both sides of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode material.

[0081] In one example, the negative electrode active material includes graphite.

[0082] In one embodiment, the interlayer spacing of the graphite is 0.3256 nm to 0.37367 nm (e.g., 0.3256 nm, 0.33 nm, 0.3356 nm, 0.336 nm, 0.3361 nm, 0.3365 nm, 0.337 nm, 0.338 nm, 0.339 nm, 0.34 nm, 0.342 nm, 0.345 nm, 0.347 nm, 0.35 nm, 0.352 nm, 0.355 nm, 0.357 nm, 0.36 nm, 0.36367 nm, 0.37 nm, 0.37367 nm). When the interlayer spacing of the graphite is lower than 0.3256 nm, the battery has poor rate performance and poor fast charging kinetics. When the interlayer spacing of the graphite is higher than 0.37367 nm, the compaction density of the negative electrode sheet is low and the energy density of the battery is low. When the interlayer spacing of the graphite is limited to the above range, the compaction density of the negative electrode sheet is higher, the energy density of the battery is higher, and the thickness of the passivation film formed by the phosphate additive on the surface of the negative electrode sheet is more uniform, with excellent ion conductivity. Therefore, the battery has better rate performance and better fast charging dynamics performance.

[0083] In one example, the negative electrode active material includes graphite, and the interlayer spacing of the graphite is 0.3356 nm-0.3367 nm.

[0084] In one embodiment, the specific surface area of ​​the negative electrode active material is 1 m 2 / g-5m 2 / g (e.g. 1m 2 / g, 1.5m 2 / g, 2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g、5m 2 / g). The specific surface area of ​​the negative electrode active material can affect the transmission path of lithium ions on the surface of the negative electrode active material. Limiting the specific surface area of ​​the negative electrode active material to the above range can improve the transmission rate of lithium ions. At the same time, the negative electrode active material with the above specific surface area can be used with the electrolyte of the present disclosure to improve the ion transmission performance of the battery, so that the battery has higher intermittent cycle performance under high temperature conditions.

[0085] In one embodiment, the specific surface area of ​​the negative electrode active material is 1.8 m 2 / g-4m 2 / g.

[0086] In one example, the negative active material layer includes a thickener, a second binder, and a second conductive agent.

[0087] In one embodiment, the second binder includes one or more of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon. The second binder can improve the bonding between the negative electrode active materials and the bonding between the negative electrode active material layer and the negative electrode current collector.

[0088] In one example, the second conductive agent includes one or more of a carbon-based material, a metal-based material, and a conductive polymer (eg, a polyphenylene derivative). The second conductive agent may impart conductivity to the electrode.

[0089] In one example, the carbon-based material includes one or more of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber.

[0090] In one example, the metal-based material includes metal powder and / or metal fiber.

[0091] In one example, the metal powder includes one or more of copper, nickel, aluminum, and silver.

[0092] In one example, the thickener includes sodium carboxymethylcellulose (CMC-Na) and / or lithium carboxymethylcellulose (CMC-Li).

[0093] In one example, the negative electrode current collector includes one or more of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and a polymer substrate coated with a conductive metal.

[0094] According to a specific embodiment, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 94.5wt%-97.5wt% (for example, 94.5wt%, 95wt%, 96wt%, 96.5wt%, 97wt%, 97.5wt%), the weight content of the thickener is 1wt%-3wt% (for example, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%), the weight content of the second binder is 1wt%-3wt% (for example, 1wt%, 1.5wt%, 1.8wt%, 2wt%, 2.5wt%, 2.8wt%, 3wt%), and the weight content of the second conductive agent is 0.5wt%-3wt% (for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%).

[0095] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 95.5wt%-97wt%, the weight content of the thickener is 1.2wt%-2wt%, the weight content of the second binder is 1.5wt%-2.5wt%, and the weight content of the second conductive agent is 0.8wt%-2wt%.

[0096] In one example, the battery includes a separator located between the positive electrode sheet and the negative electrode sheet to prevent short circuit.

[0097] The separator may be a conventional separator in the art, for example, the separator includes a substrate layer and a surface treatment layer.

[0098] In one example, the separator includes a polymer or an inorganic substance, wherein the polymer and the inorganic substance are formed of a material stable to the electrolyte.

[0099] In one embodiment, the substrate layer is a non-woven fabric, film, or composite film having a porous structure. The substrate layer includes one or more of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, the substrate layer can be a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film.

[0100] In one embodiment, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0101] In one example, the inorganic layer includes inorganic particles and a binder.

[0102] In one example, the inorganic particles include one or more of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0103] In one example, the binder includes one or more of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0104] In one example, the polymer layer includes a polymer, and the polymer includes one or more of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0105] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0106] The following examples are provided to illustrate the batteries of the present disclosure.

[0107] Example 1

[0108] (1) Preparation of ingredients

[0109] Positive electrode active material layer: positive electrode active material (lithium nickel cobalt manganese oxide (LiNi 0.5 Mn 0.3 Co 0.2O2)) 95.5 parts by weight, a first binder (polyvinylidene fluoride (PVDF)) 2 parts by weight, a first conductive agent (acetylene black) 2.5 parts by weight;

[0110] Negative electrode active material layer: 96 parts by weight of negative electrode active material (graphite), 1.3 parts by weight of thickener (sodium carboxymethyl cellulose (CMC-Na)), 1.8 parts by weight of second binder (styrene-butadiene rubber), and 0.9 parts by weight of second conductive agent (acetylene black).

[0111] Electrolyte: 14.5 parts by weight of electrolyte lithium salt (lithium hexafluorophosphate (LiPF6)), 0.5 parts by weight of phosphate compound (I-1), 0.5 parts by weight of sultone compound (II-6), 15 parts by weight of ethylene carbonate, 20 parts by weight of propylene carbonate, 40 parts by weight of diethyl carbonate, 4.5 parts by weight of ethyl methyl carbonate, 2.5 parts by weight of a first additive (VC), and 2.5 parts by weight of a second additive (1 part by weight of DTD, 1 part by weight of LiPO2F2, and 0.5 parts by weight of LiODFB).

[0112] (2) Preparation of batteries

[0113] 1) Preparation of the positive electrode sheet: The positive electrode active material, the first binder, and the first conductive agent are mixed, N-methylpyrrolidone (NMP) is added, and the mixture is stirred in a vacuum mixer until the mixed system becomes a uniform, fluid positive electrode slurry; the positive electrode slurry is evenly coated on an aluminum foil with a thickness of 10 μm; the coated aluminum foil is baked in an oven at five different temperature gradients (90°C, 115°C, 120°C, 110°C, and 90°C), and then dried in an oven at 120°C for 8 hours, and then rolled and slit to obtain the desired positive electrode sheet.

[0114] 2) Preparation of the negative electrode sheet: The negative electrode active material, thickener carboxyl, second binder, and second conductive agent are mixed, deionized water is added, and a negative electrode slurry is obtained under the action of a vacuum mixer; the negative electrode slurry is evenly coated on a copper foil with a thickness of 8 μm; the copper foil is dried at room temperature and then transferred to an 80°C oven for drying for 10 hours, and then cold pressed and slit to obtain the negative electrode sheet.

[0115] 3) Preparation of electrolyte: In an argon-filled glove box (water content <10 ppm, oxygen content <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate, and ethyl methyl carbonate (EMC) were uniformly mixed, and then fully dried electrolyte lithium salt was dissolved in the above-mentioned non-aqueous solvent, and a phosphate additive, a sultone compound, a first additive, and a second additive were added to prepare an electrolyte.

[0116] 4) Diaphragm

[0117] A polyethylene membrane with a thickness of 8 μm (provided by Asahi Kasei Corporation) was selected.

[0118] 5) Preparation of lithium-ion batteries

[0119] The positive electrode sheet of step 1), the separator of step 4), and the negative electrode sheet of step 2) are stacked in order, ensuring that the separator is located between the positive and negative electrode sheets to play an isolating role, and then a bare cell without liquid injection is obtained by winding; the bare cell is placed in an outer packaging foil, and the electrolyte of step 3) is injected into the dried bare cell. After vacuum packaging, standing, forming, shaping, sorting and other processes, the desired lithium-ion battery is obtained.

[0120] Example 2

[0121] The electrolyte was prepared with reference to Example 1, except that the electrolyte consisted of 14.5 parts by weight of an electrolyte lithium salt (10.5 parts by weight of lithium hexafluorophosphate (LiPF6) and 4 parts by weight of lithium bis(fluorosulfonyl)imide (LiFSI), 0.5 parts by weight of a phosphate compound (I-1), 0.5 parts by weight of a sultone compound (II-6), 15 parts by weight of ethylene carbonate, 20 parts by weight of propylene carbonate, 46.5 parts by weight of diethyl carbonate, 0 parts by weight of ethyl methyl carbonate, 2.5 parts by weight of a first additive (VC), and 2.5 parts by weight of a second additive (1 part by weight of DTD, 1 part by weight of LiPO2F2, and 0.5 parts by weight of LiODFB).

[0122] Example 3 group

[0123] This example group was carried out with reference to Example 1, except that the weight content (dwt%) of the phosphate additive in the electrolyte was adjusted to change d / W and d / X. See Table 1 for details.

[0124] Example 4 Group

[0125] This example group was carried out with reference to Example 1, except that the specific selection of the phosphate ester additive was changed. For details, see Table 1.

[0126] Example 5 Group

[0127] This example group was carried out with reference to Example 1, except that the weight content of the sultone compound (ewt%) was changed. See Table 1 for details.

[0128] Example 6

[0129] The process was carried out in accordance with Example 1, except that the weight content of one or more of ethylene carbonate, propylene carbonate and diethyl carbonate in the electrolyte was changed. For details, see Table 1.

[0130] Example 7 Group

[0131] The same process was carried out as in Example 1, except that the specific selection of the positive electrode active material was changed. For details, see Table 1.

[0132] Example 8 Group

[0133] The same method as in Example 1 is used, except that the interlayer spacing of graphite is changed by adjusting the specific selection of the negative electrode active material. See Table 1 for details.

[0134] Example 9

[0135] The same process was carried out as in Example 1, except that the specific selection of the sultone compound was changed. For details, see Table 1.

[0136] Example 10 Group

[0137] The same process was carried out as in Example 1, except that the median particle size Dv50 and specific surface area of ​​the positive electrode active material were changed. For details, see Table 1.

[0138] Example 11 Group

[0139] The same procedure was followed as in Example 1, except that the specific surface area of ​​the negative electrode active material was changed. For details, see Table 1.

[0140] Comparative Example 1

[0141] The same process was carried out as in Example 1, except that no phosphate was added to the electrolyte. For details, see Table 1.

[0142] Comparative Example 2

[0143] The same procedure was followed as in Example 1, except that d / W was 0.02. See Table 1 for details.

[0144] Comparative Example 3

[0145] The same process was carried out as in Example 1, except that d / W was 0.59. For details, see Table 1.

[0146] Comparative Example 4

[0147] The same procedure was carried out as in Example 1, except that W was 0.9. For details, see Table 1.

[0148] Comparative Example 5

[0149] The same process was carried out as in Example 1, except that d / X was 25. For details, see Table 1.

[0150] Table 1-1

[0151] Table 1-2

[0152] - means it does not exist;

[0153] ewt% represents the weight content of sultone compound in the electrolyte;

[0154] fwt% represents the weight content of ethyl methyl carbonate in the electrolyte.

[0155] Test Case

[0156] The batteries obtained in the examples and comparative examples were respectively subjected to the following tests.

[0157] 1. 45℃ 2C / 10C intermittent cycle test process:

[0158] Place at 45°C for 60 minutes, charge at 2C constant current and constant voltage to 4.35V (cut-off current 0.05C), discharge at 10C constant current to 3.0V, place for 30 minutes, charge at 2C constant current and constant voltage to 4.35V (cut-off current 0.05C), use PPG soft pack battery thickness gauge to test the thickness of the battery at this time, record it as a, place for 5 minutes, discharge at 10C constant current to 3.0V, place for 2 hours, charge at 2C constant current and constant voltage to 4.35V (cut-off current 0.05C), place for 20 hours, the above is one charge and discharge cycle. The lithium-ion battery was tested for 180 cycles of charge and discharge at 45°C under the above conditions and the battery thickness was b. b, the calculation formula of thickness expansion rate is: (ba) / a×100%.

[0159] 2. 45℃ 2C / 10C cycle test process:

[0160] Discharge the battery at 0.5C to 3.0V at 45°C and let it rest for 5 minutes. Then charge it at 2C to 4.35V. Constant-voltage charge it at 4.35V to 0.05C. After charging, discharge it at 10C to 3.0V. This constitutes one cycle. Repeat this charge-discharge process at 45°C for 600 cycles. The capacity discharged in the first cycle is recorded as C1, and the capacity discharged in the 600th cycle is recorded as C600. The capacity retention rate is calculated as: (C1 / C600) × 100%.

[0161] 3. 5℃1C / 5C cycle test process:

[0162] Discharge the battery at 0.5C to 3.0V at 5°C and let it rest for 5 minutes. Then charge it at 1C to 4.35V. Constant-voltage charge it at 4.35V to 0.05C. After charging, discharge it at 5C to 3.0V. This constitutes one cycle. Repeat this charge-discharge process at 5°C for 100 cycles. The capacity discharged during the first cycle is recorded as C1, and the capacity discharged during the 100th cycle is recorded as C100. The capacity retention rate is calculated as: (C1 / C100) × 100%.

[0163] 4. 135℃ 30min hot box test process:

[0164] At 25°C, charge the battery at 1C to 4.35V, then charge it at a constant voltage at 4.35V to a cutoff current of 0.05C. Place the battery in a hot box and heat it to 135°C at a rate of 5±2°C / min. Maintain it at 132°C for 30 minutes. If the battery does not catch fire or explode, it passes the hot box test. Ten batteries are tested in each test, and the results are expressed as "Number of Tests Passed / 10PASS." "10 / 10PASS" means 10 out of 10 tests were passed, "5 / 10PASS" means 5 out of 10 tests were passed, and "0 / 10PASS" means 0 out of 10 tests were passed.

[0165] 5. -10℃ 5C low temperature discharge test process:

[0166] At 25°C, charge the battery to 4.35V at 1C constant current and constant voltage, with a cut-off current of 0.05C, and then discharge it to 3.0V at 5C constant current. Record the initial capacity as C0. Charge the battery to 4.35V at 1C constant current and constant voltage, with a cut-off current of 0.05C. Place the battery at a low temperature of -10°C for 2 hours, and then discharge it to 3.0V at 5C constant current. Record the capacity Cn. The calculation formula for the capacity retention rate is: (C0 / Cn)×100%.

[0167] The obtained results are recorded in Table 2.

[0168] Table 2

[0169] As can be seen from Table 2, it can be seen from the comparative examples and the embodiments that the thickness expansion rate of the battery of the embodiment is significantly reduced after 180 cycles at 45°C, the capacity retention rate / % after 600 cycles at 45°C is significantly improved, the capacity retention rate / % after 100 cycles at 5°C is significantly improved, the number of times the 135°C hot box test passes the test is significantly improved, and the capacity retention rate at -10°C is significantly improved. This shows that the battery of the present invention improves the high and low temperature cycle performance, storage performance and safety performance of the battery by limiting the diffraction peak intensity of the positive electrode active material to satisfy 1.2≤W≤3, 0.02≤X≤0.15, and 0.06≤Y≤0.15, and at the same time limiting the battery to satisfy 0.033≤d / W≤0.4 and 0.67≤d / X≤6.5.

[0170] The preferred embodiments of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, various simple variations of the technical solution of the present disclosure may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed by the present disclosure and fall within the scope of protection of the present disclosure.

Claims

1. A lithium ion battery, characterized in that: The lithium ion battery comprises a positive electrode sheet and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on one side or both sides of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, W is a peak intensity ratio of a (003) crystal plane to a (104) crystal plane in the positive electrode active material, and X is a peak intensity ratio of a (006) crystal plane to a 104 crystal plane in the positive electrode active material; the electrolyte comprises a phosphate additive, and the weight content of the phosphate additive is dwt% based on the total weight of the electrolyte, then the lithium ion battery satisfies the following relationship: 0.033≤d / W≤0.4 and 0.67≤d / X≤6.

5.

2. The lithium ion battery according to claim 1, wherein The diffraction peak intensity of the positive electrode active material satisfies the following relationship: 1.2≤W≤3, 0.02≤X≤0.15; and / or; 0.06≤Y≤0.15, wherein Y is the peak intensity ratio of the (006) crystal plane to the (104) crystal plane in the positive electrode active material; And / or, the electrolyte includes ethylene carbonate, propylene carbonate and diethyl carbonate. Based on the total weight of the electrolyte, the weight content of ethylene carbonate is awt%, the weight content of propylene carbonate is cwt%, and the weight content of diethyl carbonate is bwt%. Then the electrolyte satisfies the following relationship: 0.1<a / c<0.8, and / or; 45≤(a+c) / d≤300, and / or; 150≤b / d≤500.

3. The lithium ion battery according to claim 2, wherein: 30≤a+c≤50; and / or, bwt% is 30wt%-70wt%, preferably 40wt%-65wt%; And / or, dwt% is 0.1wt%-1wt%, preferably 0.3wt%-0.7wt%.

4. The lithium ion battery according to any one of claims 1 to 3, wherein: The phosphate additive comprises a structure shown in formula (I), Wherein, R1, R2, and R3 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, and at least one of R1, R2, and R3 is selected from substituted or unsubstituted C2-C5 unsaturated hydrocarbon group; and the substituted substituent is selected from halogen.

5. The lithium ion battery according to any one of claims 1 to 4, wherein: The phosphate ester additive includes one or more of the following structures:

6. The lithium ion battery according to any one of claims 1 to 5, wherein: The electrolyte includes a sultone compound, and the sultone compound includes a structure represented by formula (II), Wherein, R4, R5, and R6 are each independently selected from hydrogen, halogen, and substituted or unsubstituted C1-C5 alkyl, and the substituted substituent is halogen.

7. The lithium ion battery according to claim 6, wherein: The sultone compound includes one or more of the following structures, 8. The lithium ion battery according to claim 6 or 7, wherein: The weight ratio of the sultone compound to the phosphate additive is (0.01-50):1, preferably (0.5-10):1; And / or, based on the total weight of the electrolyte, the weight content of the sultone compound is 0.01wt%-10wt%, preferably 0.25wt%-3wt%.

9. The lithium ion battery according to any one of claims 1 to 8, wherein: The electrolyte includes ethyl methyl carbonate, and the weight content of the ethyl methyl carbonate is 0wt%-75wt% based on the total weight of the electrolyte.

10. The lithium ion battery according to any one of claims 1 to 9, wherein: The electrode solution includes a first additive and a second additive; Preferably, the first additive comprises one or more of vinylene carbonate, vinylethylene carbonate and fluoroethylene carbonate; Preferably, the second additive includes one or more of vinyl sulfate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium tetrafluoroborate, tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate.

11. The lithium ion battery according to claim 10, wherein: Based on the total weight of the electrolyte, the weight content of the first additive is 0.01wt%-5wt%, and the weight content of the second additive is 0.5wt%-6wt%.

12. The lithium ion battery according to any one of claims 1 to 11, wherein: The positive electrode active material includes a ternary layered oxide, wherein the ternary layered oxide includes a chemical formula of Li a Ni y Mn z Co x A k A ternary layered oxide of O2, wherein 0.9≤a≤1.1, 0.1≤x≤0.4, 0.3≤y≤1, 0≤z≤0.3, 0≤k≤0.05, A is a doping element, and A includes one or more of Al, Mg, Ti and Nb; And / or, the positive electrode active material includes Ni element, and the molar content of Ni element is ≥50% based on the total molar amount of transition metal elements in the positive electrode active material; And / or, the median particle size Dv50 of the positive electrode active material is 4 μm-18 μm; And / or, the specific surface area of ​​the positive electrode active material is 0.2 m 2 / g-1.5m 2 / g.

13. The lithium ion battery according to any one of claims 1 to 12, wherein: The lithium-ion battery comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer located on one side or both sides of the negative electrode current collector, the negative electrode active material layer comprises a negative electrode material, and the negative electrode active material comprises graphite; Preferably, the interlayer spacing of the graphite is 0.3256nm-0.37367nm.

14. The lithium ion battery according to claim 13, wherein: The specific surface area of ​​the negative electrode active material is 1 m 2 / g-5m 2 / g.

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