A battery

Abstract

The application provides a battery, which comprises a negative electrode sheet, a positive electrode sheet, a separator and an electrolyte, the negative electrode sheet comprises a negative electrode current collector, the negative electrode current collector comprises a copper foil, the surface of the copper foil comprises a protective layer with a thickness of 5 nm-100 nm, and the average proportion of low-angle grain boundaries with a difference of less than 10° between two crystal grains in the copper foil is less than 18%; the separator comprises a carrier layer, the carrier layer comprises a substrate layer and an organic coating layer located on at least one side surface of the substrate layer, the organic coating layer comprises organic particles with a composition comprising a nitrogen-containing compound, and the Dv10 of the organic particles is 0.15 μm-0.5 μm; the electrolyte comprises ethyl difluoroacetate and a tricyanide compound, the weight proportion of ethyl difluoroacetate in the total weight of the electrolyte is A 1 %, the weight proportion of the tricyanide compound is A 2 %, and the battery satisfies 9≤A 1 / A 2 ≤35. The battery of the application can inhibit the corrosion of the copper foil and the dissolution of copper ions, and improve the cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery. Background Technology

[0002] Lithium-ion batteries are widely used in various products, such as laptops, mobile phones, and new energy vehicles, due to their advantages such as large capacity and long cycle life. In particular, silicon-based anodes have extremely high theoretical specific capacity, far exceeding that of traditional graphite, which can significantly improve the energy density of lithium-ion batteries, thereby effectively extending the battery life of electronic devices.

[0003] The problem of a high K-value is particularly prominent in silicon-based anode systems. During charging and discharging, silicon undergoes drastic volume changes, leading to repeated rupture and regeneration of the solid electrolyte interphase (SEI) membrane. This process continuously consumes active lithium and electrolyte while constantly exposing fresh silicon surfaces, exacerbating side reactions and resulting in a significantly higher K-value than traditional graphite anode systems. Secondly, silicon-based materials (such as the widely used silicon-carbon material) have high hardness, and the expansion of silicon particles can easily puncture the separator, inducing localized electron conduction and further increasing the self-discharge current. Therefore, reducing the K-value of silicon-based anode batteries has become a key challenge in improving their reliability for commercial applications. Summary of the Invention

[0004] To address the issue of increased battery K-value caused by the expansion of the negative electrode active layer, common existing technologies involve applying a coating layer to the surface of the silicon-based material to reduce its expansion or increasing the puncture resistance of the separator. However, this study found that due to the high hardness of silicon-based materials, the protective layer of the negative electrode current collector is easily damaged during the rolling stage of the negative electrode active layer. This leads to direct contact between the exposed copper foil and the electrolyte during the battery formation stage, causing corrosion of the copper foil by the electrolyte and resulting in the dissolution of copper ions. This leads to copper deposition on the negative electrode, and the deposited copper dendrites can easily induce local short circuits inside the battery, increasing the battery K-value. At the same time, copper dissolution reduces the performance of the copper foil, which, under the expansion stress of the negative electrode during battery cycling, exacerbates the risk of breakage of the negative electrode current collector, thereby reducing the battery's cycle performance.

[0005] To overcome the problems of increased K-value and reduced cycle performance caused by copper ion dissolution, this invention provides a battery. The battery of this invention optimizes the protective layer structure on the surface of the negative electrode current collector, improves the corrosion resistance of the copper foil, effectively and stably inhibits the corrosion of the copper foil and the dissolution of copper ions, improves the problem of copper metal precipitation at the negative electrode during the formation stage, reduces the K-value, and simultaneously improves the battery's cycle performance.

[0006] To achieve the above objectives, the present invention provides a battery comprising a negative electrode, a positive electrode, a separator, and an electrolyte. The negative electrode comprises a negative current collector, the negative current collector comprises a copper foil, the surface of the copper foil comprises a protective layer, the thickness of the protective layer on one side is 5nm-100nm, the average proportion of small-angle grain boundaries in the copper foil is less than 18%, and the small-angle grain boundary is a grain boundary where the orientation difference between two grains is less than 10°. The diaphragm includes a carrier layer, the carrier layer includes a substrate layer and an organic coating located on at least one side surface of the substrate layer, the organic coating includes organic particles, the organic particles are composed of nitrogen-containing compounds, and the Dv10 of the organic particles is 0.15μm-0.5μm; The electrolyte comprises ethyl difluoroacetate and a trinitrile compound, wherein the weight percentage of ethyl difluoroacetate is A, based on the total weight of the electrolyte. 1 The weight percentage of the trinitrile compound is A. 2 The battery satisfies the following relationship: 9≤A 1 / A 2 ≤35.

[0007] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: This invention provides basic physical isolation for the negative electrode current collector by setting a protective layer with a thickness of 5nm-100nm on the surface of the negative electrode current collector, while avoiding the increase in interface impedance caused by excessive thickness of the protective layer. Meanwhile, by controlling the proportion of small-angle grain boundaries in the copper foil to be less than 18%, the present invention improves the corrosion resistance of the copper foil itself, slows down the corrosion of the copper foil at the damaged part of the protective layer, and thus inhibits the corrosion of the copper foil and the dissolution of copper ions. Furthermore, this invention adds a trinitrile compound to the electrolyte. The trinitrile compound can improve the stability of the positive electrode active material, preventing transition metals in the positive electrode active material from precipitating and migrating to the negative electrode and damaging the SEI film, thereby improving the battery's cycle performance. However, the trinitrile compound can form an adsorption layer with the copper exposed at the damaged copper foil protective layer through coordination bonds. Because the molecular structure of the trinitrile compound is branched or asymmetrical with multiple strongly polar functional groups, its multiple cyano groups cannot simultaneously form coordination bonds with the copper on the copper foil surface. This results in the trinitrile compound failing to form a dense adsorption layer, which becomes loose, disordered, and contains numerous voids. Furthermore, the cyano groups that do not participate in coordination carry a partial positive charge and can attract corrosive anions or water molecules to aggregate. These corrosive molecules corrode the exposed copper foil along the gaps and defects in the adsorption layer, forming pitting corrosion, which initiates and accelerates the local corrosion of the copper foil. Therefore, ethyl difluoroacetate is also added to the electrolyte. Ethyl difluoroacetate is more difficult to oxidize and decompose under high pressure. Compared with traditional easily decomposed carbonate solvents, the stability of ethyl difluoroacetate reduces its side reactions with lithium salts (such as LiPF6), thereby inhibiting the formation of highly corrosive substances such as HF and HPO2F2, which can reduce the corrosion of the copper foil by the electrolyte. Furthermore, during the first charge and discharge of the battery, ethyl difluoroacetate preferentially oxidizes and decomposes on the positive electrode surface compared to other solvents, synergistically forming a thin and dense positive electrode electrolyte interphase (CEI) film with trinitrile compounds. This enhances the structural stability of the CEI film, reduces the generation of electrolyte byproducts, and further reduces the corrosion of copper foil by electrolyte byproducts. Additionally, the decomposition products of ethyl difluoroacetate can co-form an adsorption layer with trinitrile compounds at the damaged areas of the copper foil, reducing the positive charge of the trinitrile compound adsorption layer and decreasing the amount of HF and Cl. - Corrosive anions accumulate, thereby reducing localized corrosion micro-zones on the copper foil surface and reducing copper ion dissolution. However, excessive DEFA content can lead to a decrease in the ionic conductivity of the electrolyte. The relationship between the weight percentages of trinitrile compounds and ethyl difluoroacetate in the electrolyte should be controlled to satisfy: 9 ≤ A 1 / A 2 With a temperature ≤35, the electrolyte's oxidation resistance and ionic conductivity can be further balanced, allowing the trinitrile compound and ethyl difluoroacetate to synergistically form a stable composite adsorption layer on the copper foil surface. This prevents copper corrosion while balancing the potential of the adsorption layer, reducing the aggregation of corrosive anions and water molecules, further inhibiting pitting corrosion of the copper foil and reducing copper ion dissolution. Moreover, the trinitrile compound and ethyl difluoroacetate can synergistically form a thin and dense positive electrode electrolyte interface film (CEI film), effectively improving the structural stability of the CEI film, reducing the generation of electrolyte byproducts, further reducing the corrosion of the copper foil by electrolyte byproducts, and reducing copper ion dissolution.

[0008] Furthermore, this invention also adds nitrogen-containing organic particles to the organic coating of the diaphragm and controls the Dv10 of the organic particles to be 0.15μm-0.5μm. Under the action of the electrolyte, the organic particles release a small amount of nitrogen-containing compounds, which migrate to the surface of the copper foil and form a protective film mainly composed of Cu-N coordination bonds with the copper. This repairs the damage to the protective layer and fills the gaps in the trinitrile compound adsorption layer, improving the density of the compound adsorption layer and further reducing the corrosion of the copper foil and the dissolution of copper ions. At the same time, the nitrogen-containing compounds can also adsorb the dissolved copper ions, reducing the free copper ions in the electrolyte. Therefore, the battery of the present invention can effectively and stably suppress the corrosion of copper foil and the dissolution of copper ions at the damaged protective layer during the formation stage and the cycling process, thereby improving the problem of copper metal precipitation at the negative electrode during the formation stage, avoiding the reduction of the current collector performance of the negative electrode, and improving the cycle stability of the battery.

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

[0010] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0011] Figure 1 The figure shown is a cross-sectional schematic diagram of the negative electrode current collector of the present invention.

[0012] Figure 2 The image shown is one of the cross-sectional schematic diagrams of the diaphragm of the present invention.

[0013] Figure 3 The image shown is a second cross-sectional schematic diagram of the diaphragm of the present invention.

[0014] Figure 4 The third cross-sectional schematic diagram of the diaphragm of the present invention is shown. Detailed Implementation

[0015] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0016] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0017] This invention provides a battery comprising a negative electrode, a positive electrode, a separator, and an electrolyte. The negative electrode includes a negative current collector, which comprises a copper foil. The surface of the copper foil includes a protective layer, the thickness of which on one side is 5nm-100nm, for example, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, or 75nm. The copper foil has a diameter of 80nm, 85nm, 90nm, 95nm, or 100nm, and the average proportion of small-angle grain boundaries in the copper foil is less than 18%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or 17%. The small-angle grain boundary is a grain boundary where the difference in orientation between two grains is less than 10° (for example, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, or 9°). The diaphragm includes a carrier layer, the carrier layer includes a substrate layer and an organic coating located on at least one surface of the substrate layer, the organic coating includes organic particles, the organic particles are composed of nitrogen-containing compounds, and the Dv10 of the organic particles is 0.15μm-0.5μm, for example, 0.15μm, 0.18μm, 0.2μm, 0.22μm, 0.24μm, 0.26μm, 0.28μm, 0.3μm, 0.32μm, 0.34μm, 0.36μm, 0.38μm, 0.4μm, 0.42μm, 0.44μm, 0.46μm, 0.48μm or 0.5μm; The electrolyte comprises ethyl difluoroacetate and a trinitrile compound, wherein the weight percentage of ethyl difluoroacetate is A, based on the total weight of the electrolyte. 1 The weight percentage of the trinitrile compound is A. 2 The battery satisfies the following relationship: 9≤A 1 / A 2 ≤35, for example, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 27, 28, 30, 32, 34 or 35.

[0018] In this invention, the main component of the protective layer is a metal or a metal oxide, wherein the metal is at least one selected from nickel and chromium, and the metal oxide includes at least one selected from chromium oxide and nickel oxide. According to a specific embodiment, such as... Figure 1 As shown, the protective layer 11 is located on two opposing surfaces in the thickness direction of the copper foil 1.

[0019] In this invention, the thickness of the protective layer on one side refers to the thickness of the protective layer on one side of the copper foil, which can be measured by an ellipsometer. For example, copper foil disassembled from a battery with the negative electrode active layer removed, or fresh copper foil without a negative electrode active layer, is used as the analysis object. A flat area on the surface of the copper foil is selected, and the thickness of the copper foil protective layer is tested by an ellipsometer using a non-contact spectroscopic measurement method. This method uses multi-wavelength (400nm-1000nm) polarized light to irradiate the surface of the copper foil to obtain the ellipsometric parameters Ψ and Δ. In the data processing, a three-layer optical model of "copper substrate + oxide layer (Cu2O / CuO) + air" is established, and the material optical constants (n,k) are set. The measured data is fitted by the nonlinear least squares method to inversely deduce the protective thickness.

[0020] In this invention, Dv10 refers to the particle size corresponding to the cumulative particle size distribution of the organic particles, arranged from smallest to largest, reaching 10%. In this invention, the volumetric particle size distribution of the organic particles can be obtained by SEM measurement. Specifically, a fresh separator that has not been used in battery preparation or a portion of the separator removed from the battery that has not been in contact with the positive and negative electrode active layers is used as a sample. An SEM image of the organic coating surface is taken, and an arbitrary 100μm × 100μm region is selected. The Dv10 of the organic particles is then measured and statistically processed using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.). The Dv10 of the organic particles can also be obtained by laser particle size analyzer testing. For example, before separator preparation or after separating the organic coating, the organic particles are thoroughly stirred, and the Dv10 of the organic particles is measured using a laser particle size analyzer.

[0021] In this invention, the proportion of small-angle grain boundaries in the copper foil refers to the proportion of grain boundaries with a crystallographic orientation difference of less than 10° between two grains in the total number of all grain boundaries (including small-angle grain boundaries and large-angle grain boundaries). The proportion of small-angle grain boundaries in the copper foil can be measured by electron backscatter diffraction (EBSD).

[0022] A protective layer, primarily composed of metal oxides or metals, is formed on the surface of the copper foil to isolate the negative electrode current collector from the reaction and corrosion of the electrolyte. However, increasing the thickness of the oxide protective layer leads to an increase in the impedance of the negative electrode current collector. Therefore, in addition to forming a protective layer on the surface of the negative electrode current collector, this invention further controls the thickness of the protective layer to 5nm-100nm to ensure that while isolating the negative electrode current collector from electrolyte corrosion, it also avoids an increase in the impedance of the negative electrode current collector, thereby improving the cycle performance and rate performance of the battery. Furthermore, to further improve the problem of copper foil corrosion and copper ion dissolution caused by damage to the protective layer on the surface of the negative electrode current collector, this invention also controls the flatness of the small-angle grain boundaries in the copper foil. With a proportion of less than 18%, the grain boundary energy of the copper foil is low, thereby reducing the diffusion of impurity atoms (such as oxygen and sulfur) along the grain boundaries, improving the corrosion resistance of the copper foil itself, reducing the probability of copper foil corrosion and the tendency of copper ion dissolution. Therefore, this invention effectively reduces the corrosion of copper foil and the dissolution of copper ions at the damaged protective layer, prevents the reduction and precipitation of copper ions on the surface of the negative electrode during the formation stage and the reduction of the performance of the negative electrode current collector, and lowers the K value. At the same time, it can reduce or even avoid the reduction of copper foil performance caused by copper dissolution, thereby reducing or even avoiding the breakage of the negative electrode current collector due to the expansion stress of the negative electrode during battery cycling, and improving the cycle performance of the battery.

[0023] Furthermore, to improve the stability of the positive electrode active material and prevent transition metals from precipitating and migrating to the negative electrode to damage the SEI film, trinitrile compounds are often added to the electrolyte. This study found that during battery formation, due to the strong complexing effect of trinitrile compounds, they can form an adsorption layer with the exposed copper at the damaged copper foil protective layer through coordination bonds. However, because the molecular structure of trinitrile compounds is branched or asymmetrical with multiple strongly polar functional groups, the multiple cyano groups of the trinitrile compound do not simultaneously form ideal coordination bonds with the copper on the copper foil surface. This results in the trinitrile compound failing to form a dense adsorption layer, which becomes loose, disordered, and contains numerous voids. Moreover, the carbon atoms in the cyano groups that fail to effectively participate in coordination and remain suspended outside the adsorption layer (especially highly active intermediate cyano groups) may carry a partial positive charge, attracting corrosive anions (such as Cl-). - Or water molecules gather around it, and these corrosive anions (such as Cl) -Water molecules can corrode the exposed copper foil along the gaps and defects in the adsorption layer, forming pitting corrosion, which initiates and accelerates localized corrosion of the copper foil. Therefore, ethyl difluoroacetate is added to the electrolyte. Ethyl difluoroacetate contains two fluorine atoms with strong electron-withdrawing ability, exhibiting strong molecular structural stability. This lowers the highest occupied molecular orbital (HOMO) energy level of ethyl difluoroacetate. In electrochemistry, the lower the HOMO energy level, the more difficult it is for the molecule to lose electrons. Therefore, ethyl difluoroacetate itself is less likely to be oxidized and decomposed under high pressure. Compared with traditional easily decomposed carbonate solvents, the stability of ethyl difluoroacetate effectively reduces its side reactions with lithium salts (such as LiPF6), thereby inhibiting the formation of highly corrosive substances such as HF, HPO2, and F2, and thus effectively improving the oxidation resistance of the electrolyte and reducing electrolyte side reactions. The corrosion of the copper foil at the damaged protective layer by the product further reduces the dissolution of copper ions. In addition, during the first charge and discharge of the battery, ethyl difluoroacetate preferentially oxidizes and decomposes on the surface of the positive electrode, forming a thin and dense positive electrode electrolyte interface film (CEI film) in synergy with trinitrile compounds. This effectively improves the structural stability of the CEI film and further reduces the corrosion of the copper foil by electrolyte byproducts. Therefore, under the synergistic effect of trinitrile compounds and ethyl difluoroacetate in the electrolyte, the corrosion of the copper foil and the dissolution of copper ions are further reduced, the precipitation of copper metal in the negative electrode during the formation stage is reduced, the K value is lowered, the performance of the negative electrode current collector is avoided, and the cycle performance of the battery is improved.

[0024] Furthermore, the decomposition products of ethyl difluoroacetate in the electrolyte (such as LiF and Li₂CO₃) can form an adsorption layer with the trinitrile compound at the damaged area of ​​the copper foil through electrostatic interactions, reducing the positive charge of the trinitrile compound adsorption layer and decreasing the concentration of HF and Cl. - Corrosive anions accumulate, thereby reducing localized corrosion micro-zones on the copper foil surface and further reducing copper ion dissolution. However, excessive DEFA content can lead to a decrease in the ionic conductivity of the electrolyte. Therefore, in order to balance the oxidation resistance and ionic conductivity of the electrolyte, and to ensure sufficient ethyl difluoroacetate to generate decomposition products to effectively reduce the positive charge of the trinitrile compound adsorption layer and reduce HF and Cl... - To mitigate the accumulation of corrosive anions at the adsorption layer, this invention controls the weight percentages of ethyl difluoroacetate and trinitrile compounds in the electrolyte, ensuring that the battery satisfies the relationship: 9 ≤ A. 1 / A 2 ≤35, by precisely controlling the weight ratio of ethyl difluoroacetate to trinitrile compound, a stable composite adsorption layer is synergistically formed on the copper foil surface by the trinitrile compound and ethyl difluoroacetate. This inhibits pitting corrosion and copper ion dissolution, effectively preventing copper precipitation during the formation stage, reducing the K value, and improving battery cycle performance. When A1 / A 2 If the content of difluoroethyl ester is less than 9, then the content of trinitrile compound is relatively insufficient or the content of trinitrile compound is too high. Difluoroethyl ester cannot fully compensate for the defects in the trinitrile compound adsorption layer, resulting in poor pitting corrosion inhibition. 1 / A 2 If the content is greater than 35, the content of trinitrile compounds is relatively insufficient, which is not conducive to improving the stability of the positive electrode active material. Alternatively, if the content of ethyl difluoroacetate is too high, it will lead to a decrease in the ionic conductivity of the electrolyte and a decrease in rate performance.

[0025] Furthermore, this invention adds organic particles containing nitrogen compounds to the organic coating of the separator, and controls the Dv10 of the organic particles to be 0.15μm-0.5μm. This allows the organic coating to have suitable porosity without reducing the lithium-ion permeability of the separator. The organic particles with the aforementioned particle size can release trace amounts of nitrogen compounds under the action of the electrolyte. These nitrogen compounds migrate to the copper foil surface and form coordination bonds with copper through nitrogen atoms in their molecular structure, thereby forming a protective film on the copper foil surface. This film not only repairs damage to the protective layer on the copper foil surface together with the trinitrile compound, but also compensates for defects and voids in the trinitrile compound adsorption layer, improving the density of the trinitrile compound adsorption layer. This further reduces copper foil corrosion and copper ion dissolution, reduces copper metal precipitation during the formation stage, lowers the K value, and improves the cycle stability of the battery. Moreover, the nitrogen compounds can also adsorb copper ions dissolved in the electrolyte, reducing copper precipitation and further improving the cycle stability of the battery.

[0026] In this invention, it is understood that the trace dissolution of nitrogen-containing compounds by the organic particles under the action of the electrolyte does not mean that the particle state of all organic particles disappears or that all organic particles are completely dissolved. Rather, it means that some nitrogen-containing substances in a single organic particle dissolve, and the particle state of the single organic particle can still be completely retained.

[0027] In this invention, a copper foil with a protective layer of specific thickness and small-angle grain boundaries, a separator containing organic particles containing nitrogen-containing compounds, and an electrolyte containing ethyl difluorocarbonate and trinitrile compounds in a specific ratio are used. Compared with existing technologies, this invention can effectively suppress the corrosion of copper foil and the dissolution of copper ions without increasing the overall impedance of the battery, thereby reducing or even preventing copper deposition at the negative electrode during the formation stage, lowering the K value, and improving the cycle performance of the battery. To further improve the effect, one or more of the technical features can be further optimized.

[0028] In some embodiments, the thickness of the protective layer on one side is 20nm-80nm, for example, 20nm, 22nm, 24nm, 26nm, 28nm, 30nm, 32nm, 34nm, 36nm, 38nm, 40nm, 42nm, 44nm, 46nm, 48nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm or 80nm.

[0029] In some embodiments, the protective layer includes at least one of chromium and nickel.

[0030] In some embodiments, the thickness of the copper foil is 3μm-20μm, for example, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm.

[0031] In this invention, the thickness of the copper foil can be tested by the following method: for example, disassembling the negative electrode sheet from the battery or using the fresh copper foil obtained during the preparation of the negative electrode sheet as a sample, taking a cross-sectional image of the copper foil in the thickness direction using SEM, randomly selecting 10 different positions in the SEM image, measuring the thickness of the copper foil at each position, and taking the arithmetic mean as the thickness of the copper foil.

[0032] In some embodiments, the negative electrode sheet further includes a negative electrode active layer located on at least one side surface of the negative electrode current collector. The negative electrode active layer comprises a silicon-based material, and the weight percentage of the silicon-based material in the negative electrode active layer is 8%-96%, for example, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 96%.

[0033] In some embodiments, 4.5 ≤ A 1 ≤50, for example, 4.5, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50.

[0034] In some embodiments, 20≤A 1 ≤43.

[0035] In some embodiments, 0.5 ≤ A 2≤4.5, for example, 0.5, 0.7, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4 or 4.5.

[0036] In some embodiments, 1≤A 2 ≤2.9. When 1≤A 2 When the concentration is ≤2.9, the formation of pitting corrosion by trinitrile compounds can be more effectively suppressed without affecting the stability of the positive electrode active material, and the local corrosion of copper foil caused and accelerated by trinitrile compounds can be suppressed, thereby further improving the dissolution of copper in the copper foil.

[0037] In some embodiments, the battery satisfies the relationship: 15 ≤ A 1 / A 2 ≤27.

[0038] According to one specific implementation, 4.5 ≤ A 1 ≤50, 0.5≤A 2 ≤4.5, the battery satisfies the relationship: 9≤A 1 / A 2 ≤35.

[0039] According to one specific implementation, 4.5 ≤ A 1 ≤50, 0.5≤A 2 ≤4.5, the battery satisfies the relationship: 15≤A 1 / A 2 ≤27.

[0040] According to one specific implementation, 20≤A 1 ≤43, 1≤A 2 ≤2.9, the battery satisfies the relationship: 9≤A 1 / A 2 ≤35.

[0041] According to one specific implementation, 20≤A 1 ≤43, 1≤A 2 ≤2.9, the battery satisfies the relationship: 15≤A 1 / A 2 ≤27.

[0042] In some embodiments, the average proportion of small-angle grain boundaries in the copper foil is less than 10%.

[0043] In some embodiments, the molecular structure of the nitrogen-containing compound includes at least one of a diazine ring, a triazine ring, a pyrimidine ring, a benzimidazole ring, and a purine ring.

[0044] In some embodiments, the nitrogen-containing compound includes at least one selected from 2-aminopyrazine, pyrazinamide, 5,6-diamino-2,3-dicyanopyrazine, 2,3-dicyanopyrazine, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, 4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, guanine, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-sulfonic acid benzimidazole, 2-mercapto-5-carboxybenzimidazole, and 2-mercapto-5-nitrobenzimidazole.

[0045] In some embodiments, the ethyl difluoroacetate includes at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate.

[0046] In some embodiments, the trinitrile compound includes at least one selected from 1,3,6-hexanetrionitrile, 1,2,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,1,1-tris(cyanoethoxymethylene)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,2,6-tris(cyanoethoxy)hexane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, tris(2-cyanoethyl) phosphate, 1,2,4-butanetrionitrile, 1,3,5-cyclohexanetrionitrile, 1,3,5-phenyltricyanide, and 1,2,3-propanetrionitrile.

[0047] In some embodiments, the electrolyte includes an organic solvent, a lithium salt, and additives.

[0048] In some embodiments, the organic solvent includes ethyl difluoroacetate and at least one of the following optional substances: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethyl propionate (EP), propyl propionate (PP), ethyl acetate (EA), and ethyl butyrate (EB).

[0049] In some embodiments, the organic solvent includes ethyl difluoroacetate and at least one of the following optional substances: propyl propionate, ethyl propionate, diethyl carbonate, propylene carbonate, and ethylene carbonate.

[0050] In some embodiments, the additive includes a trinitrile compound.

[0051] In some embodiments, the additive further includes a first compound whose molecular structure includes unsaturated bonds, including at least one of carbon-carbon double bonds, carbon-oxygen double bonds, phosphorus-oxygen double bonds, and aromatic π bonds.

[0052] In some embodiments, the first compound includes at least one of ethylene ethylene ester, triargyl phosphate, and ethylene carbonate.

[0053] In some embodiments, the weight percentage of the first compound is A, based on the total weight of the electrolyte. 3 %, where 0.01≤A 3 ≤3 (e.g., 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or 3).

[0054] During the first charge of a lithium-ion battery, at the negative electrode potential, the first compound containing unsaturated bonds is reduced on the surface of the negative electrode active layer, generating free radical intermediates. These free radical intermediates have high reactivity and can undergo chain polymerization reactions with other free radicals or unreacted molecules, thereby forming a high molecular weight polymer film with a three-dimensional cross-linked structure on the surface of the negative electrode active layer. The polymer film has a non-conductive polymer backbone, thus exhibiting high density, strong electronic insulation, and good flexibility. Based on the total weight of the electrolyte, the weight percentage of the first compound is controlled to be 0.01%-3%. On the one hand, the first compound containing unsaturated bonds can be reduced before copper ions, thereby inhibiting the reduction of free copper ions in the formation stage to copper metal on the surface of the negative electrode active layer and reducing the K value. On the other hand, even after a small amount of copper metal is deposited on the surface of the negative electrode active layer, the flexible polymer film that continues to form on the copper metal surface can, to a certain extent, prevent the copper deposited in the negative electrode active layer from piercing the separator and forming a micro-short circuit, further reducing the K value and thus improving the cycle performance of the battery in subsequent cycles.

[0055] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0056] In some embodiments, based on the total weight of the electrolyte, the organic solvent accounts for 10%-85% by weight (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 85%), the additive accounts for 0.5%-50% by weight (e.g., 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 50%), and the lithium salt accounts for 5%-40% by weight (e.g., 5%, 10%, 15%, 20%, 25%, 30%, or 40%).

[0057] In some embodiments, the proportion of grains with a particle size less than or equal to 1 μm in the copper foil is B. 1 The electrolyte further includes a first compound, wherein the weight percentage of the first compound is A, based on the total weight of the electrolyte. 3 The battery satisfies the relationship: 4≤B 1 / A 3 ≤450 (e.g., 4, 5, 6, 8, 10, 12, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, or 450).

[0058] Increasing the proportion of grains with a diameter less than or equal to 1 μm in the copper foil can improve the grain packing density, grain boundary smoothness, reduce surface energy and chemical reactivity, and enhance oxidation resistance. An appropriate amount of the first compound can form a dense and tough polymer film on the surface of the negative electrode active layer, effectively blocking the reduction and precipitation of copper ions on the negative electrode surface. However, excessive polymer film formation increases the interfacial impedance between the negative electrode and the separator, reducing the battery's rate performance. When the proportion of grains with a diameter less than or equal to 1 μm increases, the corrosion resistance of the copper foil is enhanced, the amount of dissolved copper ions decreases accordingly, and the amount of the first compound in the electrolyte can be relatively reduced, controlling the battery to satisfy the relationship: 4 ≤ B. 1 / A 3 ≤450 can achieve optimal matching between the proportion of grains with a particle size of less than or equal to 1μm in the copper foil and the content of the first compound in the electrolyte, further suppressing the dissolution of copper ions and the precipitation of copper metal during the formation stage, reducing the K value, and improving the battery's cycle stability and rate performance. When B 1 / A 3When the value is <4, the proportion of grains with a diameter less than or equal to 1 μm in the copper foil is relatively low, the surface of the copper foil is too rough, the corrosion of the copper foil increases, and the risk of copper deposition and short circuit increases. Alternatively, the content of the first compound containing unsaturated bonds is relatively high, the polymer film is too thick, and the interfacial impedance of the negative electrode increases. Therefore, it is not conducive to further improving the K value and rate performance of the battery. 1 / A 3 When the temperature is greater than 450, the proportion of grains with a diameter of less than or equal to 1 μm in the copper foil is relatively high, which reduces the bending resistance of the copper foil. Under the repeated stress caused by the expansion of the negative electrode active layer during battery cycling, the risk of copper foil breakage increases, which is not conducive to improving the cycle stability of the battery. Alternatively, if the content of the first compound containing unsaturated bonds is relatively low, the polymer film on the surface of the negative electrode active layer cannot effectively block the reduction and precipitation of copper ions on the negative electrode surface, and copper precipitation is aggravated. Therefore, it is not conducive to further reducing the K value of the battery and improving the cycle performance of the battery.

[0059] In this invention, the proportion of grains with a diameter less than or equal to 1 μm in the copper foil can be measured by the following method: For example, the battery is disassembled, the negative electrode sheet is removed, and the negative electrode active layer on the surface of the copper foil is removed to obtain the copper foil. Alternatively, the copper foil obtained during the preparation of the negative electrode sheet is used. After removing the protective layer on the surface of the copper foil, the area equivalent circle diameter of all grains in a randomly selected 14 μm × 14 μm area on the surface of the copper foil is statistically obtained by electron backscatter diffraction (EBSD) as the grain diameter. The proportion of grains with a diameter less than or equal to 1 μm is calculated as the proportion of grains with a diameter less than or equal to 1 μm in that region. The arithmetic mean of any 5 regions on the surface of the copper foil is calculated as the final result.

[0060] In some embodiments, the proportion of grains with a particle size less than or equal to 1 μm in the copper foil is B. 1 %, where 10≤B 1 ≤50 (e.g., 10, 15, 20, 25, 30, 35, 40, 45 or 50).

[0061] According to one specific implementation, 0.01≤A 3 ≤3, 10≤B 1 ≤50, the battery satisfies the relationship: 4≤B 1 / A 3 ≤450.

[0062] In this invention, the copper foil can be obtained by conventional preparation methods in the art, or by selecting products sold on the market.

[0063] In some embodiments, the method for preparing the copper foil includes the following steps: (1) Dissolve high-purity copper to prepare an electrolyte solution containing copper sulfate (CuSO4) and sulfuric acid (H2SO4), and add brighteners, leveling agents and inhibitors to regulate the grain structure of the copper foil during the deposition process (e.g., the average proportion of grain size and small-angle grain boundaries). The electrolyte solution is purified and filtered before entering the electrolytic cell.

[0064] (2) A titanium alloy cathode roller with a precision-polished surface is placed in an electrolytic cell as a substrate, and direct current is applied to it. Cu 2+ Ions migrate from the electrolyte solution to the cathode surface, where they are reduced to metallic copper. This metallic copper is then deposited layer by layer to obtain a copper foil of the target thickness. The temperature, electrolyte circulation rate, and stirring intensity are strictly controlled throughout the process to ensure uniform deposition and the absence of dendrites, thereby achieving a uniform grain structure.

[0065] (3) Peel the copper foil off the cathode roller, clean it with deionized water, dry it with hot air, and then perform surface treatment, such as chemical roughening or anti-oxidation coating (e.g., metal or metal oxide), to obtain copper foil with a protective layer on the surface.

[0066] It is understood that, in this invention, the grain size of copper foil and the average proportion of small-angle grain boundaries can be changed by adjusting the type and amount of additives and the electrolysis process during preparation.

[0067] In some embodiments, the negative electrode active layer further includes a carbon-based material, which includes at least one of graphite, soft carbon, and hard carbon materials.

[0068] In some embodiments, the negative electrode active layer further includes a negative electrode conductive agent and a negative electrode binder.

[0069] In some embodiments, the negative electrode conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, graphene, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0070] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyurethane, polyacrylonitrile, acrylonitrile-vinylidene fluoride copolymer, acrylate adhesives, polytetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), polyacrylic acid (PAA), sodium polymethyl cellulose (CMC-Na), and lithium polymethyl cellulose (CMC-Li).

[0071] In some embodiments, the silicon-based material in the negative electrode active layer comprises 8%-96% by weight (e.g., 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 96%), and the carbon-based material comprises 0-89% by weight (e.g., 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 7%). The negative electrode conductive agent has a weight percentage of 0.5%-10% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%), and the negative electrode binder has a weight percentage of 0.5%-15% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%).

[0072] In some embodiments, the organic particles account for 40%-99% of the weight of the organic coating, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99%.

[0073] In some embodiments, the organic coating further includes a first binder, the first binder comprising 1%-60% by weight of the organic coating, for example, 1%, 2%, 4%, 6%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%.

[0074] In some embodiments, the organic coating further includes a first adhesive, which includes at least one of the following: fluoropolymer, polyimide, polyacrylonitrile, aramid resin, styrene-butadiene rubber, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose, sodium carboxymethyl cellulose, carboxyethyl cellulose, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, acrylic polymer, acrylate polymer, lithium polystyrene sulfonate, silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, and pure styrene latex.

[0075] In this invention, the fluoropolymer includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0076] In this invention, the acrylate polymers include one or more of the following: polymethyl methacrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, acrylate monomer-ethylene copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer copolymer, styrene-acrylate monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

[0077] In this invention, the acrylate monomers include one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, ethyl methacrylate, n-propyl acrylate, octyl acrylate, isooctyl acrylate, octadecyl acrylate, isobutyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate.

[0078] In this invention, the acrylic polymer includes one or more of polyacrylic acid, polymethacrylic acid, polyethylacrylic acid, polypropylacrylic acid, and polybutylacrylic acid.

[0079] In some embodiments, the organic coating further includes heat-resistant particles, the heat-resistant particles being composed of at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, aluminum nitride, boron nitride, zirconium titanate, barium titanate, and magnesium fluoride.

[0080] In some embodiments, the heat-resistant particles constitute 0-59% of the organic coating by weight, for example, 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, and 59%. A weight percentage of 0 indicates that no heat-resistant particles have been added to the organic coating.

[0081] According to one specific embodiment, the organic coating includes organic particles, a first binder, and heat-resistant particles. The organic particles account for 40%-98% of the weight of the organic coating, the first binder accounts for 1%-9% of the weight of the organic coating, and the heat-resistant particles account for 1%-59% of the weight of the organic coating.

[0082] According to one specific embodiment, the organic coating includes organic particles and a first binder, wherein the organic particles account for 90%-99% of the weight of the organic coating, and the first binder accounts for 1%-10% of the weight of the organic coating.

[0083] In some embodiments, the carrier layer includes a first surface and a second surface, and the diaphragm includes a first adhesive layer located on the first surface and a second adhesive layer located on the second surface. The first adhesive layer includes first polymer particles, and the second adhesive layer includes a porous structure formed of a second polymer.

[0084] In some embodiments, the first surface corresponds to the positive electrode and the second surface corresponds to the negative electrode.

[0085] In some embodiments, the organic coating is located on the first surface.

[0086] According to one specific embodiment, the carrier layer includes a first surface and a second surface, the first surface corresponding to the positive electrode and the second surface corresponding to the negative electrode. The separator includes a first adhesive layer located on the first surface and a second adhesive layer located on the second surface. The first adhesive layer includes first polymer particles, and the second adhesive layer includes a porous structure formed by a second polymer.

[0087] A first adhesive layer containing first polymer particles is used on the first surface of the carrier layer facing the positive electrode of the separator to ensure that there is an appropriate buffer space on the positive electrode side of the separator. During the formation stage and cycling process, when the negative electrode active layer expands, it slows down the stretching of the negative electrode active layer on the copper foil, reduces the stretching of the current collector by the expansion stress, further reduces the risk of current collector breakage, and improves the cycle performance of the battery. Furthermore, a second adhesive layer containing a porous structure is used on the second surface of the carrier layer facing the negative electrode of the separator, which can improve the adhesion between the separator and the negative electrode and reduce the interfacial impedance between the separator and the electrode, thereby improving the cycle performance and rate performance of the battery.

[0088] According to a specific implementation method, such as Figure 2 As shown, the diaphragm 2 includes a carrier layer 21, a first adhesive layer 22, and a second adhesive layer 23. The carrier layer 21 includes a substrate layer 211 and an organic coating 212 located on one side of the substrate layer. The first adhesive layer 22 is located on the surface of the organic coating 212, and the second adhesive layer 23 is located on the other side of the substrate layer 211.

[0089] According to a specific implementation method, such as Figure 3As shown, the diaphragm 2 includes a carrier layer 21, a first adhesive layer 22, and a second adhesive layer 23. The carrier layer 21 includes a substrate layer 211 and an organic coating 212 located on one side of the substrate layer. The first adhesive layer 22 is located on the other side of the substrate layer 211, and the second adhesive layer 23 is located on the surface of the organic coating 212.

[0090] According to a specific implementation method, such as Figure 4 As shown, the diaphragm includes a carrier layer 21, a first adhesive layer 22, and a second adhesive layer 23. The carrier layer 21 includes a substrate layer 211 and an organic coating 212 located on both sides of the substrate layer. The first adhesive layer 22 is located on one side of the organic coating 212, and the second adhesive layer is located on the other side of the organic coating 212.

[0091] In some embodiments, the first polymer particles comprise at least one of the following: fluoropolymers, acrylate polymers, polyacrylonitrile, polyacrylic acid, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resins, epoxy resins, ethylene-vinyl acetate copolymers, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymers and their derivatives, aramid fibers, phenolic resins, polyimides, and polyetherimides.

[0092] In some embodiments, the first polymer particle is an agglomerated polymer particle, wherein the average particle size of the secondary particles of the agglomerated polymer particle is 3μm-8μm, for example, 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, 7.2μm, 7.4μm, 7.6μm, 7.8μm, or 8μm.

[0093] By controlling the average particle size of the secondary particles of the agglomerated polymer particles in the first adhesive layer within the above-mentioned range, the buffering capacity of the positive electrode side of the separator can be further improved. When the negative electrode active layer expands, the stretching of the negative electrode active layer on the copper foil can be further reduced, thereby further reducing the risk of copper foil breakage and improving the cycle performance of the battery.

[0094] In this invention, the secondary particles of the agglomerated polymer particles are formed by the agglomeration of five or more primary particles of the agglomerated polymer particles. In this invention, the average particle size of the secondary particles of the agglomerated polymer particles can be measured by the following method: For example, an SEM image of the cross-section of the first adhesive layer in the thickness direction of the diaphragm is taken. Within an arbitrarily selected area of ​​100μm × 100μm, secondary particles formed by the agglomeration of five or more primary particles of the agglomerated first polymer particles are identified in the cross-sectional image of the first adhesive layer. A rectangle or square with the smallest area completely surrounding the secondary particle is drawn, i.e., a rectangle or square tangent to the outer edge of the particle is drawn. The length of the long side of the rectangle, or the length of any side of the square, is the particle size of the single secondary particle. The arithmetic mean of the particle sizes of 100 randomly selected secondary particles of the agglomerated polymer particles is calculated as the average particle size of the secondary particles of the agglomerated polymer particles. If there are fewer than 100 secondary particles in a single image, multiple images are taken until a total of 100 are accumulated.

[0095] According to one specific embodiment, the first polymer particle is an agglomerated polymer particle, and the components of the first polymer particle include at least one of acrylate polymers, modified polyethylene, and modified polypropylene.

[0096] In some embodiments, the coverage of the first polymer particles on the first surface is 5%-30%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 22%, 24%, 26%, 28%, or 30%.

[0097] By controlling the coverage of the first polymer particles on the first surface to be 5%-30%, when the first adhesive layer is located on the surface of the organic coating, nitrogen-containing compounds in the organic coating of the separator can dissolve and migrate to the negative electrode more quickly through the pores between the first polymer particles in the first adhesive layer, forming coordination bonds with the copper on the copper foil surface at the damaged part of the negative electrode protective layer, further inhibiting the dissolution of copper ions in the copper foil and improving the cycle performance of the battery.

[0098] According to one specific embodiment, the first adhesive layer is located on the surface of the organic coating of the carrier layer, and the first polymer particles have a coverage of 5%-30% on the first surface.

[0099] In this invention, the coverage rate of the first polymer particles on the first surface refers to the proportion of the projected area of ​​the first polymer particles in the first adhesive layer on the first surface of the carrier layer to the total area of ​​the first surface of the carrier layer. This can be specifically measured using a scanning electron microscope (SEM): for example, a separator that has not been in contact with the electrode and is disassembled from a battery, or a fresh separator obtained during the manufacturing process, is observed using an elemental discrimination microscope. The magnification is adjusted to 200X, and automatic area measurement and identification and statistical analysis of the first polymer particles are performed to obtain the coverage rate value. Five areas are randomly selected on the surface of the first adhesive layer for measurement, and the arithmetic mean of the five measurements is taken as the coverage rate of the first polymer particles on the first surface.

[0100] In some embodiments, the second polymer includes at least one of fluoropolymers, acrylonitrile polymers, phenolic resins, epoxy resins, ethylene-vinyl acetate copolymers, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymers and their derivatives, aramid fibers, phenolic resins, polyimides, and polyetherimides.

[0101] In this invention, acrylonitrile polymers refer to polymers in which the proportion of acrylonitrile monomers is higher than 50%.

[0102] In some embodiments, the second polymer accounts for 30%-100% of the weight of the second adhesive layer, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%.

[0103] In some embodiments, the second adhesive layer further includes filler particles, the filler particles being composed of at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, aluminum nitride, boron nitride, zirconium titanate, barium titanate, and magnesium fluoride.

[0104] In some embodiments, the filler particles account for 0-70% of the weight of the second adhesive layer, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%. A filler particle weight percentage of 0 indicates that no filler particles have been added to the second adhesive layer.

[0105] In some embodiments, the filler particles account for 20%-70% of the weight of the second adhesive layer.

[0106] According to one specific embodiment, the second adhesive layer includes a second polymer but does not include filler particles, and the weight percentage of the second polymer in the second adhesive layer is 30%-100%.

[0107] According to one specific embodiment, the second adhesive layer includes a second polymer and filler particles, wherein the second polymer accounts for 30%-80% of the weight of the second adhesive layer, and the filler particles account for 20%-70% of the weight of the second adhesive layer.

[0108] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the surface of the positive current collector. The positive active layer includes a positive active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium nickel oxide, lithium titanate, and lithium manganese oxide.

[0109] In some embodiments, the positive electrode active layer further includes a positive electrode conductive agent and a positive electrode binder.

[0110] In some embodiments, the positive electrode conductive agent includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, and graphene.

[0111] In some embodiments, the positive electrode binder includes at least one of polyurethane, polyvinylidene fluoride (PVDF), acrylic-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0112] In some embodiments, in the positive electrode active layer, the weight percentage of the positive electrode active material is 80%-99.8% (e.g., 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, or 99.8%), the weight percentage of the positive electrode conductive agent is 0.1%-10% (e.g., 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%), and the weight percentage of the positive electrode binder is 0.1%-10% (e.g., 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%).

[0113] In some instances, the battery is a lithium-ion rechargeable battery.

[0114] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0115] Example 1 (1) Preparation of positive electrode The positive electrode active material (lithium cobalt oxide), positive electrode binder (polyvinylidene fluoride 500), and positive electrode conductive agent (conductive carbon black: carbon nanotubes (weight ratio) = 1:1) were mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 98.5:0.8:0.7 and continuously stirred under the action of a stirrer to form a homogeneous and fluid positive electrode slurry. Subsequently, the positive electrode slurry was coated on both sides of the positive electrode current collector (aluminum foil) and dried in a vacuum oven at 120°C for 6 hours. Then, it was rolled and slit to obtain the desired positive electrode sheet.

[0116] (2) Preparation of negative electrode Carbon-based materials (artificial graphite), silicon-based materials (silicon-carbon materials), negative electrode conductive agent (conductive carbon black: carbon nanotubes (weight ratio) = 1:1), and negative electrode binder (styrene-butadiene rubber: polyacrylic acid (weight ratio) = 1:1) are mixed in an aqueous solvent at a weight ratio of 76:20:1:3 and continuously stirred under the action of a mixer to form a uniform and flowing negative electrode slurry. Subsequently, the slurry was coated onto both sides of the negative electrode current collector (copper foil), and dried in a vacuum oven at 120°C for 6 hours. After rolling and slitting, the negative electrode sheet was obtained. The negative electrode current collector includes a copper foil and protective layers disposed on two opposing surfaces along the thickness direction of the copper foil. The copper foil has a thickness of 8 μm, and the protective layers include chromium. The thickness of a single-sided protective layer is 35 nm. The average proportion of small-angle grain boundaries in the copper foil is 7.2%, where a small-angle grain boundary is defined as a grain boundary where the orientation difference between two grains is less than 10°. The proportion of grains with a diameter less than or equal to 1 μm in the copper foil is 31.2% (B). 1 =31.2).

[0117] (3) Electrolyte preparation In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), the following non-fluorinated solvents—propyl propionate, ethyl propionate, and propylene carbonate—were mixed in a volume ratio of 3:4:3 to form a homogeneous solvent. Then, 31.1% of 2,2-difluoroethyl acetate (ethyl difluoroacetate, A) based on the total weight of the electrolyte was slowly added. 1 =31.1%), 1.8% 1,3,6-hexanetrionitrile (trionitrile compound, A) 2 =1.8%), 1.6% ethylene ethylene (Compound 1, A) 3=1.6), 10% fluoroethylene carbonate, and 13% LiPF6 were stirred evenly to obtain the desired lithium-ion battery electrolyte, wherein A 1 / A 2 =31.1 / 1.8=17.3, B 1 / A 3 =31.1 / 1.6=19.5.

[0118] (4) Preparation of the diaphragm Organic particles (composed of melamine cyanurate, Dv10 of 0.36μm) and the first binder (polyacrylic acid) were added to deionized water at a weight ratio of 96:4. After thorough stirring, a first slurry with a solid content of 25% was obtained. The first slurry was coated onto one side of the substrate layer (polyethylene) using a gravure roller. After drying in a multi-section oven at 60°C, an organic coating was formed on the carrier layer located on one side of the substrate layer.

[0119] Polymethyl methacrylate (first polymer particles, agglomerated polymer particles) and water are mixed and stirred thoroughly to obtain a second slurry. The second slurry is then coated onto the surface of the organic coating in the carrier layer (first surface) using a gravure roller, and then dried in a multi-section oven at 60°C to form a first adhesive layer.

[0120] Polyvinylidene fluoride (second polymer) and boehmite (filler particles) were added to N,N-dimethylacetamide (DMAC) at a weight ratio of 65:35. After thorough stirring until the second polymer was dissolved, a third slurry was obtained. The third slurry was coated onto the other side surface (second surface) of the substrate layer in the carrier layer using a gravure roller. It was then dried in a multi-section oven at 60°C to form a second adhesive layer, thereby preparing the desired diaphragm. The average particle size of the secondary particles of the agglomerated polymer particles was 5.7%, and the coverage of the first polymer particles on the first surface was 17.8%.

[0121] (5) Preparation of lithium-ion batteries The electrode assembly, which is formed by sequentially stacking and winding the positive electrode, negative electrode, and separator obtained above, is then subjected to processes such as winding, electrolyte injection, vacuum sealing, room temperature standing, and high temperature formation to obtain the desired lithium-ion battery. The first adhesive layer is located on the first surface of the carrier layer and corresponds to the positive electrode, and the second adhesive layer is located on the second surface of the carrier layer and corresponds to the negative electrode.

[0122] Example 2 This embodiment is based on Embodiment 1, except that the thickness of the protective layer on one side of the copper foil surface in the negative electrode is 20.8 nm, the protective layer contains nickel, the average proportion of small-angle grain boundaries in the copper foil is 2.5%, and the proportion of grains with a diameter less than or equal to 1 μm is 20.1% (B 1=20.1), in the negative electrode active layer, the weight percentage of silicon-based material is 12%, the weight percentage of carbon-based material is 84%, the weight percentage of negative electrode binder is 3%, and the weight percentage of negative electrode conductive agent is 1%; the separator includes a carrier layer, a first adhesive layer, and a second adhesive layer. The carrier layer includes a substrate layer and an organic coating on one side of the substrate layer. The second adhesive layer is located on the surface of the organic coating (the first surface of the carrier layer) corresponding to the positive electrode. The first adhesive layer is located on the other side of the substrate layer (the second surface of the carrier layer) corresponding to the negative electrode. The first adhesive layer includes organic particles, a first binder, and heat-resistant particles. The composition of the organic particles is changed from melamine cyanurate to 2-mercaptocyanurate. The organic coating contains 90% benzimazole, 8% organic particles, 2% heat-resistant particles, and a second adhesive layer comprising a second polymer and filler particles. The second polymer comprises 30% and 70% filler particles in the second adhesive layer. In the electrolyte, ethyl difluoroacetate is replaced by 2,2-difluoroethyl acetate, and the trinitrile compound is replaced by 1,3,6-hexanetrionitrile. Based on the total weight of the electrolyte, ethyl difluoroacetate comprises 42.8% (A). 1 =42.8%), the weight percentage of trinitrile compounds was 2.8% (A 2 =2.8), A 1 / A 2 =42.8 / 2.8=15.3, B 1 / A 3 =20.1 / 1.6=12.6.

[0123] Example 3 This embodiment is based on Embodiment 1, except that in the negative electrode, the thickness of the protective layer on one side of the copper foil surface is 79.6 nm, the average proportion of small-angle grain boundaries in the copper foil is 9.6%, and the proportion of grains with a diameter less than or equal to 1 μm in the copper foil is 39.8% (B 1=39.8); The separator includes a carrier layer, a first adhesive layer, and a second adhesive layer. The carrier layer includes a substrate layer and an organic coating on both sides of the substrate layer. The first adhesive layer is located on the surface of the organic coating (the first surface of the carrier layer) and corresponds to the positive electrode. The second adhesive layer is located on the surface of the organic coating (the second surface of the carrier layer) and corresponds to the negative electrode. The first adhesive layer includes organic particles and a first binder. The organic particles account for 99% of the weight of the organic coating, and the first binder accounts for 1% of the weight of the organic coating. The second adhesive layer includes a second polymer and filler particles. The second polymer accounts for 80% of the weight of the second adhesive layer, and the filler particles account for 20% of the weight of the second adhesive layer. In the electrolyte, the trinitrile compound is replaced by 1,3,6-hexanetrinitrile with 1,2,4-butanetrinitrile. Based on the total weight of the electrolyte, the weight percentage of ethyl difluoroacetate is 26.9% (A). 1 =26.9), the weight percentage of trinitrile compounds was 1% (A 2 =1), A 1 / A 2 =26.9 / 1=26.9, B 1 / A 3 =39.8 / 1.6=24.9.

[0124] Example 4 group This embodiment group is based on Embodiment 1, except that the thickness of the protective layer on one side of the copper foil surface is changed.

[0125] Example 4-1 This embodiment is based on Embodiment 1, except that the thickness of the protective layer on one side of the copper foil surface is 5 nm.

[0126] Example 4-2 This embodiment is based on Embodiment 1, except that the thickness of the protective layer on one side of the copper foil surface is 100 nm.

[0127] Example 5 This embodiment group is based on Example 1, except that the average proportion of small-angle grain boundaries in the copper foil is 17%, and the proportion of grains with a diameter less than or equal to 1 μm in the copper foil is 32.3% (B). 1 =32.3), B 1 / A 3 =32.3 / 1.6=20.2.

[0128] Example 6 group This embodiment group is based on Example 1, except that the Dv10 of the organic particles is changed.

[0129] Example 6-1 This embodiment is based on Example 1, except that the Dv10 of the organic particles is 0.15 μm.

[0130] Example 6-2 This embodiment is based on Example 1, except that the Dv10 of the organic particles is 0.5 μm.

[0131] Example 7 group This set of examples is based on Example 1, except that the weight percentage of ethyl difluoroacetate and / or the weight percentage of trinitrile compound in the electrolyte are changed to make A 1 / A 2 Things have changed.

[0132] Example 7-1 This embodiment is based on Example 1, except that, based on the total weight of the electrolyte, the weight percentage of ethyl difluoroacetate is 27% (A). 1 =27), the trinitrile compound accounted for 2.9% by weight (A 2 =2.9), A 1 / A 2 =27 / 2.9=9.3.

[0133] Example 7-2 This embodiment is based on Example 1, except that, using the total weight of the electrolyte as a baseline, the weight percentage of ethyl difluoroacetate is 50% (A). 1 =50), the trinitrile compound accounts for 1.5% by weight (A 2 =1.5), A 1 / A 2 =50 / 1.5=33.3.

[0134] Example 7-3 This embodiment is based on Example 1, except that, based on the total weight of the electrolyte, the weight percentage of ethyl difluoroacetate is 3.5% (A). 1 =3.5), the trinitrile compound accounts for 0.3% by weight (A 2 =0.3), A 1 / A 2 =3.5 / 0.3=11.7.

[0135] Example 7-4 This embodiment is based on Example 1, except that, using the total weight of the electrolyte as a baseline, the weight percentage of ethyl difluoroacetate is 58% (A). 1 =58), the trinitrile compound accounted for 4.8% by weight (A 2 =4.8), A 1 / A 2=58 / 4.8=12.1.

[0136] Example 8 group This embodiment is based on Example 1, except that the proportion of grains with a particle size of less than or equal to 1 μm in the copper foil and / or the weight proportion of the first compound based on the total weight of the electrolyte are changed, so that B 1 / A 3 Changes have occurred; see Table 1 for details.

[0137] Table 1 The " / " indicates that the data does not exist. Example 9 group This embodiment group is based on Embodiment 1, except that the average particle size of the secondary particles of the agglomerated polymer particles and / or the coverage of the first polymer particles on the first surface are changed.

[0138] Example 9-1 This embodiment is based on Embodiment 1, except that the average particle size of the secondary particles of the agglomerated polymer particles is 3 μm, and the coverage of the first polymer particles on the first surface is 5.2%.

[0139] Example 9-2 This embodiment is based on Embodiment 1, except that the average particle size of the secondary particles of the agglomerated polymer particles is 7.8 μm, and the coverage of the first polymer particles on the first surface is 29.8%.

[0140] Example 9-3 This embodiment is based on Embodiment 1, except that the average particle size of the secondary particles of the agglomerated polymer particles is 2.2 μm, and the coverage of the first polymer particles on the first surface is 4.3%.

[0141] Example 9-4 This embodiment is based on Embodiment 1, except that the average particle size of the secondary particles of the agglomerated polymer particles is 9.7 μm, and the coverage of the first polymer particles on the first surface is 38.8%.

[0142] Example 10 group This embodiment group is based on Embodiment 1, except that the weight ratio of silicon-based material in the negative electrode active layer is changed.

[0143] Example 10-1 This embodiment is based on Embodiment 1, except that the weight ratio of silicon-based material in the negative electrode active layer is 8%.

[0144] Example 10-2 This embodiment is based on Embodiment 1, except that the weight ratio of silicon-based material in the negative electrode active layer is 96%.

[0145] Example 11 This embodiment is based on Embodiment 1, except that the second adhesive layer is located on the surface of the organic coating (the first surface of the carrier layer) and the other side surface of the substrate layer (the second surface of the carrier layer).

[0146] Comparative Example 1 This embodiment is based on Embodiment 1, except that the thickness of the protective layer on one side of the copper foil surface is 4.2 nm.

[0147] Comparative Example 2 This embodiment is based on Embodiment 1, except that the thickness of the protective layer on one side of the copper foil surface is 108 nm.

[0148] Comparative Example 3 This embodiment is based on Embodiment 1, except that the average proportion of small-angle grain boundaries in the copper foil is 19.3%, and the proportion of grains with a diameter less than or equal to 1 μm in the copper foil is 30.9% (B). 1 =30.9), B 1 / A 3 =30.9 / 1.6=19.3.

[0149] Comparative Example 4 This embodiment is based on Example 1, except that the Dv10 of the organic particles is 0.1 μm.

[0150] Comparative Example 5 This embodiment is based on Example 1, except that the Dv10 of the organic particles is 0.7 μm.

[0151] Comparative Example 6 This embodiment is based on Embodiment 1, except that boehmite is used to replace the organic particles in the organic coating.

[0152] Comparative Example 7 This embodiment is based on Example 1, except that no trinitrile compound is added to the electrolyte.

[0153] Comparative Example 8 This embodiment is based on Example 1, except that the trinitrile compound in the electrolyte is replaced by a dinitrile compound (adiponitrile).

[0154] Comparative Example 9 This embodiment is based on Example 1, except that ethyl difluoroethylene was not added to the electrolyte.

[0155] Comparative Example 10 This embodiment is based on Example 1, except that, based on the total weight of the electrolyte, the weight percentage of ethyl difluoroacetate is 4.5% (A). 1 =4.5), the weight percentage of the trinitrile compound is 0.6% (A 2 =0.6), A 1 / A 2 =4.5 / 0.6=7.5.

[0156] Comparative Example 11 This embodiment is performed in accordance with Embodiment 1, except that, based on the total weight of the electrolyte, the weight percentage of ethyl difluoroacetate is 26% (A). 1 =26), the trinitrile compound accounts for 0.7% by weight (A 2 =0.7), A 1 / A 2 =26 / 0.7=37.1.

[0157] Test case The batteries prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 2: (1) Capacity retention rate during 25℃ cycling: At 25℃±2℃, discharge at 0.2C to the lower limit voltage of 3V, let stand for 10 minutes, charge at 0.8C to the upper limit voltage of 4.53V, cut off at 0.05C, let stand for 10 minutes, discharge at 0.2C to the lower limit voltage of 3V, let stand for 10 minutes, and record the initial discharge capacity as C. 0 Cyclic procedure: Charge at 0.5C to the upper limit voltage of 4.53V, cut off at 0.05C, rest for 10 minutes, discharge at 0.5C to the lower limit voltage of 3V, rest for 10 minutes, cycle 500 times, and record the discharge capacity as C. 1 The capacity retention rate is (C 1 / C 0 )×100%.

[0158] (2) Failure of the negative electrode current collector: Take the battery from the above-mentioned example after 500T cycles, disassemble the battery cell, carefully separate the negative electrode sheet, further peel off the negative electrode active layer on the surface of the negative electrode current collector, expose the negative electrode current collector, observe whether the negative electrode current collector is broken, and measure the crack length with a plastic ruler. The severity of the crack is indicated by the crack length: level 0 < level 1 (crack length ≤ 3mm) < level 2 (crack length is 3mm-8mm) < level 3 (> 8mm).

[0159] (3) Rate performance at 25℃: At 25±2℃, allow to stand for 10 minutes, discharge at 0.2C to the lower limit voltage of 3V, allow to stand for 10 minutes, and record the initial discharge capacity as Q. 1 Cyclic charging method: Charge at 0.2C to the upper limit voltage of 4.53V, cut off at 0.05C, let stand for 10 minutes, discharge at 0.2C to the lower limit voltage of 3V, let stand for 5 minutes, repeat 3 times, and then test the discharge capacity and record it as Q. 2 The rate capability is Q 2 / Q 1 ×100%.

[0160] (4) Volumetric energy density: The battery was left to stand for 1 hour at (25±2)℃. It was then charged at a constant current of 0.5C to 4.53V, followed by constant voltage charging at 4.53V to a current of 0.05C, and left to stand for 10 minutes. Next, it was discharged at a constant current of 0.2C to 3V and left to stand for 10 minutes. The discharge capacity was recorded as Q, the average discharge plateau voltage as V, the lithium-ion battery thickness as H, the lithium-ion battery length as Y, the lithium-ion battery width as Z, and the volumetric energy density as (Q×V) / (H×Y×Z), in Wh / L.

[0161] (5) Determination of K value: The open-circuit potential of the sorted lithium-ion batteries was measured under constant temperature and stability conditions of 25±2℃ to obtain V. 1 After letting it stand for 24 hours, the open-circuit potential of the battery was measured again to obtain V. 2 The value of K is (V 1 -V 2 ) / Δt, where Δt is the time interval between two measurements (Δt=24h), and the unit is mV / h.

[0162] Table 2 As shown in Table 2, by comparing the comparative example and the embodiment, the embodiment shows improved room temperature cycling capacity retention, improved rate performance, reduced K value, improved volumetric energy density, and reduced breakage of the negative electrode current collector. This indicates that by setting copper foil with a specific thickness protective layer and small-angle grain boundaries, a separator containing organic particles containing nitrogen-containing compounds, and an electrolyte containing ethyl difluorocarbonate and trinitrile compounds in a specific ratio, compared with the prior art, it is possible to effectively suppress copper foil corrosion and copper ion dissolution without increasing the overall battery impedance, reduce or even prevent copper deposition at the negative electrode during the formation stage, thereby reducing the K value, improving the problem of negative electrode current collector breakage, improving the battery's room temperature cycling performance and rate performance, and ensuring that the battery has a high volumetric energy density.

[0163] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The device includes a negative electrode, a positive electrode, a separator, and an electrolyte. The negative electrode includes a negative current collector, which includes a copper foil. The surface of the copper foil includes a protective layer. The thickness of the protective layer on one side is 5nm-100nm. The average proportion of small-angle grain boundaries in the copper foil is less than 18%. The small-angle grain boundary is a grain boundary where the orientation difference between two grains is less than 10°. The diaphragm includes a carrier layer, the carrier layer includes a substrate layer and an organic coating located on at least one side surface of the substrate layer, the organic coating includes organic particles, the organic particles are composed of nitrogen-containing compounds, and the Dv10 of the organic particles is 0.15μm-0.5μm; The electrolyte comprises ethyl difluoroacetate and a trinitrile compound, wherein the weight percentage of ethyl difluoroacetate is A, based on the total weight of the electrolyte. 1 The weight percentage of the trinitrile compound is A. 2 The battery satisfies the following relationship: 9≤A 1 / A 2 ≤35.

2. The battery according to claim 1, wherein, The thickness of the protective layer on one side is 20nm-80nm; And / or, the protective layer includes at least one of chromium and nickel; And / or, the thickness of the copper foil is 3μm-20μm; And / or, the negative electrode sheet further includes a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising a silicon-based material, the silicon-based material comprising 8%-96% by weight in the negative electrode active layer.

3. The battery according to claim 1, wherein, The molecular structure of the nitrogen-containing compound includes at least one of the following: diazine ring, triazine ring, pyrimidine ring, benzimidazole ring, and purine ring; And / or, the ethyl difluoroacetate comprises at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate; And / or, the trinitrile compound includes at least one selected from 1,3,6-hexanetrionitrile, 1,2,6-hexanetrionitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,1,1-tris(cyanoethoxymethylene)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,2,6-tris(cyanoethoxy)hexane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, tris(2-cyanoethyl) phosphate, 1,2,4-butanetrionitrile, 1,3,5-cyclohexanetrionitrile, 1,3,5-phenyltricyanide, and 1,2,3-propanetrionitrile.

4. The battery according to claim 1, wherein, 4.5≤A 1 ≤50, preferably 20≤A 1 ≤43; And / or, 0.5≤A 2 ≤4.5, preferably 1≤A 2 ≤2.9; And / or, the battery satisfies the relationship: 15 ≤ A 1 / A 2 ≤27; And / or, the average proportion of small-angle grain boundaries in the copper foil is less than 10%; And / or, the nitrogen-containing compound includes at least one of 2-aminopyrazine, pyrazinamide, 5,6-diamino-2,3-dicyanopyrazine, 2,3-dicyanopyrazine, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, 4-amino-2,6-dihydroxypyrimidine, uracil, cytosine, guanine, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-sulfonic acid benzimidazole, 2-mercapto-5-carboxybenzimidazole, and 2-mercapto-5-nitrobenzimidazole.

5. The battery according to claim 1, wherein, The electrolyte further includes a first compound, the molecular structure of which includes unsaturated bonds, the unsaturated bonds including at least one of carbon-carbon double bonds, carbon-oxygen double bonds, phosphorus-oxygen double bonds, and aromatic π bonds; Preferably, the first compound includes at least one of ethylene ethylene ester, triargyl phosphate, and ethylene carbonate.

6. The battery according to claim 5, wherein, The proportion of grains with a diameter of 1 μm or less in the copper foil is B. 1 Based on the total weight of the electrolyte, the weight percentage of the first compound is A. 3 The battery satisfies the relationship: 4≤B 1 / A 3 ≤450; And / or, the proportion of grains with a diameter less than or equal to 1 μm in the copper foil is B. 1 %, where 10≤B 1 ≤50; And / or, based on the total weight of the electrolyte, the weight percentage of the first compound is A. 3 %, where 0.01≤A 3 ≤3.

7. The battery according to claim 1, wherein, The organic particles account for 40%-99% of the weight of the organic coating; And / or, the organic coating further includes a first binder, wherein the first binder accounts for 1%-60% of the weight of the organic coating; And / or, the organic coating further includes a first adhesive, the first adhesive comprising at least one of the following: fluoropolymer, polyimide, polyacrylonitrile, aramid resin, styrene-butadiene rubber, polyethylene glycol, polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose, sodium carboxymethyl cellulose, carboxyethyl cellulose, polyacrylamide, phenolic resin, epoxy resin, polyurethane, ethylene-vinyl acetate copolymer, acrylic polymer, acrylate polymer, lithium polystyrene sulfonate, silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, and pure styrene latex; And / or, the organic coating further includes heat-resistant particles, the heat-resistant particles being composed of at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, aluminum nitride, boron nitride, zirconium titanate, barium titanate, and magnesium fluoride; preferably, the heat-resistant particles account for 0-59% of the weight of the organic coating.

8. The battery according to claim 1, wherein, The carrier layer includes a first surface and a second surface, and the diaphragm includes a first adhesive layer located on the first surface and a second adhesive layer located on the second surface. The first adhesive layer includes first polymer particles, and the second adhesive layer includes a porous structure formed of a second polymer. Preferably, the first surface corresponds to the positive electrode and the second surface corresponds to the negative electrode. Preferably, the first polymer particle is an agglomerated polymer particle, and the average particle size of the secondary particles of the agglomerated polymer particle is 3μm-8μm; Preferably, the coverage of the first polymer particles on the first surface is 5%-30%.

9. The battery according to claim 8, wherein, The first polymer particles are composed of at least one of the following: fluoropolymers, acrylate polymers, polyacrylonitrile, polyacrylic acid, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, ethylene-vinyl acetate copolymer, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymer and its derivatives, aramid, phenolic resin, polyimide, and polyetherimide. And / or, the second polymer comprises at least one of fluoropolymers, acrylate polymers, polyacrylonitrile, polyacrylic acid, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, ethylene-vinyl acetate copolymer, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymer and its derivatives, aramid, phenolic resin, polyimide, and polyetherimide; preferably, the second polymer accounts for 30%-100% of the weight of the second adhesive layer; And / or, the second adhesive layer further includes filler particles, the composition of which includes at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, aluminum nitride, boron nitride, zirconium titanate, barium titanate, and magnesium fluoride; preferably, the filler particles account for 0-70% by weight in the second adhesive layer.

10. The battery according to claim 1, wherein, The positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the surface of the positive current collector. The positive active layer includes a positive active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium nickel oxide, lithium titanate, and lithium manganese oxide. And / or, the electrolyte further includes at least one of propyl propionate, ethyl propionate, diethyl carbonate, propylene carbonate, and ethylene carbonate.

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