Battery

Abstract

The invention relates to a battery which comprises a positive plate, a negative plate and a diaphragm, the positive plate comprises a positive active material layer, the negative plate comprises a negative active material layer, and the diaphragm is located between the positive plate and the negative plate and comprises a base film and a diaphragm coating arranged on at least one side surface of the base film; wherein at least one of the positive electrode active material layer, the negative electrode active material layer and the diaphragm coating comprises lithium phytate. According to the scheme provided by the invention, the battery can present excellent rate capability, cycle performance and storage performance under high voltage.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery. Background Art

[0002] Lithium-ion batteries are widely used in 3C digital, power tools, aerospace, energy storage, power vehicles and other fields due to their advantages such as high specific energy, no memory effect and long cycle life. The rapid development of electronic information technology and consumer products has put forward higher requirements for the high voltage and high energy density of lithium-ion batteries.

[0003] In related technologies, the development of high-voltage cathode materials has become an important direction for improving battery energy density. However, currently commonly used high-voltage cathode materials still face a series of problems. For example, lithium cobalt oxide undergoes phase changes under high voltage, leading to structural collapse and microcracks, affecting the battery's cycling performance and safety. At the same time, the oxygen free radicals and cobalt ions released by lithium cobalt oxide under high voltage will attack the electrolyte, causing interfacial side reactions and electrolyte decomposition, further deteriorating battery performance. The released oxygen and free radicals may trigger thermal runaway of the battery. For example, the layered structure of lithium-rich manganese-based materials is prone to phase changes during cycling under high voltage, resulting in irreversible structural damage, affecting the battery's cycling stability and service life. Moreover, the changes in the surface structure of lithium-rich manganese-based materials and the decomposition of the electrolyte under high voltage can also lead to rapid voltage decay. In addition, common problems faced by high-voltage battery systems include electrolyte decomposition and gas production, which lead to increased internal battery pressure and may cause safety issues. At the same time, side reactions are prone to occur on the surface of the electrode material, forming a solid electrolyte interface film (SEI film), which increases the internal impedance of the battery and degrades the battery's cycling performance.

[0004] Therefore, there is an urgent need to develop a battery that exhibits excellent rate performance, cycle performance and storage performance at high voltage. Summary of the Invention

[0005] In order to solve or partially solve the problems existing in the related art, the present application provides a battery that can exhibit excellent rate performance, cycle performance and storage performance at high voltage.

[0006] The present application provides a battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet comprises a positive electrode active material layer, the negative electrode sheet comprises a negative electrode active material layer, and the separator is located between the positive electrode sheet and the negative electrode sheet, and comprises a base film and a separator coating provided on at least one side of the base film. Wherein, at least one of the positive electrode active material layer, the negative electrode active material layer and the separator coating layer comprises lithium phytate.

[0007] The battery as described above, wherein the particle size D50 of the lithium phytate is 1 μm to 5 μm; and / or, The specific surface area of ​​the lithium phytate is 1m 2 / g~5m 2 / g; and / or, In the XRD diffraction pattern of the lithium phytate, a diffraction peak exists at a diffraction angle of 2θ=(23±0.5)°, and the half-peak width of the diffraction peak is ≥1.0°; and / or, In the infrared absorption spectrum of lithium phytate, at wave number 780 cm -1 ~890cm -1 、905cm -1 ~1100cm -1 、1101cm -1 ~1205cm -1 There is an absorption peak at .

[0008] The battery as described above, wherein the preparation method of the lithium phytate comprises the following steps: The phytic acid solution and the lithium source solution are mixed to obtain a salt solution, and the salt solution is spray-dried to obtain the powdered lithium phytate; Wherein, the mass ratio of phytic acid to lithium source is 1:(0.15~3); and / or, the mass percentage of the phytic acid solution is 10%~30%, and the mass percentage of the lithium source solution is 5%~20%; and / or, the mixing temperature of the mixing treatment is 25°C~120°C, and the mixing time is 1h~24h; and / or, the spraying treatment is carried out in the spray dryer, the air inlet temperature of the spray dryer is 215°C~225°C, the air outlet temperature is 60°C~160°C, the hot air temperature is 175°C~185°C, and the drying time is 3s~5s.

[0009] In the battery as described above, before the lithium phytate is used in the battery, the water content in the lithium phytate is ≤200 ppm.

[0010] The battery as described above, wherein the positive electrode active material layer comprises a positive electrode active material and the lithium phytate; The mass proportion of the lithium phytate is 0.5% to 2% of the positive electrode active material; and / or, The positive electrode active material layer satisfies the following relationship: m 植酸锂 / m 正极活性材料 =k×S 正极活性材料 / S 植酸锂 Formula 1 In the above relational formula 1, m 植酸锂 is the amount of lithium phytate added to the positive electrode active material layer; m 正极活性材料is the amount of the positive electrode active material added to the positive electrode active material layer; k is 0.005 to 0.2; S 正极活性材料 is the specific surface area of ​​the positive electrode active material; S 植酸锂 is the specific surface area of ​​the lithium phytate.

[0011] The battery as described above, wherein the method for preparing the positive electrode sheet comprises the following steps: S1, performing a first mixing process on the positive electrode binder and the solvent to obtain a positive electrode binder mixed solution; Wherein, the mass ratio of the positive electrode binder to the solvent is 0.6-1.4; and / or, the first mixing process is performed by stirring, the stirring temperature is 20° C.-60° C., and the stirring speed is 10 rpm-600 rpm; S2, adding the positive electrode active material, the positive electrode conductive agent and the lithium phytate to the positive electrode binder mixed solution for a second mixing process to obtain a positive electrode slurry; The mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (80-98): (1-10): (1-10); and / or the viscosity of the positive electrode slurry is 3500 mPa.s-6000 mPa.s; and / or the compatibility index of the lithium phytate in the positive electrode slurry and the solvent is ≤0.1; S3, applying the positive electrode slurry to at least one side of the positive electrode current collector, and performing a first drying process to obtain a positive electrode sheet; The first drying treatment is performed under vacuum conditions at 115° C. to 125° C. for 10 to 12 hours; and / or the mass percentage of the solvent in the positive electrode active material layer after the first drying treatment is not higher than 0.1%.

[0012] In the battery as described above, the diaphragm coating comprises lithium phytate, the mass percentage of lithium phytate in the diaphragm coating is 1% to 20%, and the thickness of the diaphragm coating is 0.1 μm to 5 μm.

[0013] The battery as described above, wherein the method for preparing the separator comprises the following steps: S1, dispersing the alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder in water, and mixing them evenly to obtain a diaphragm coating slurry; The mass ratio of the alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder is (50-70): (1-20): (10-25): (5-15); and / or the solid content of the diaphragm coating slurry is 15%-25%; S2, applying the membrane coating slurry to at least one side of the base film, and drying the base film to obtain the membrane; The diaphragm coating slurry is applied by coating, with a coating gap of 10 μm to 20 μm; and / or the drying treatment is a gradient drying treatment, drying at 80°C to 100°C for 1 min to 3 min, then heating to 120°C to 150°C and drying for 2 min to 5 min.

[0014] In the battery as described above, the negative electrode active material layer includes a negative electrode binder and the lithium phytate, and the mass proportion of the lithium phytate to the negative electrode binder is 0.5% to 2%.

[0015] The battery as described above, wherein the method for preparing the negative electrode sheet comprises the following steps: S1, dispersing the negative electrode active material, negative electrode conductive agent, and negative electrode binder in water, and mixing them uniformly to obtain a negative electrode mixture; Wherein, the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (90-96): (1-5): (2-5); S2. Adding lithium phytate solution to the negative electrode mixture and performing dispersion treatment to obtain a negative electrode slurry; The dispersion treatment comprises stirring at a rotation speed of 300 rpm to 800 rpm for 60 min to 120 min and ultrasonic dispersion at a power of 20 W to 50 W for 30 min to 60 min; and / or the pH of the negative electrode slurry is 7 to 9; and / or the solid content of the negative electrode slurry is 40% to 55%; S3, applying the negative electrode slurry to at least one side of the negative electrode current collector, and performing a second drying process to obtain a negative electrode sheet; The second drying treatment is performed under vacuum conditions at 115° C. to 125° C. for 10 to 12 hours; and / or the mass percentage of water in the negative electrode active material layer after the second drying treatment is not higher than 0.1%.

[0016] The battery as described above, wherein the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes LiCoO2 and its modified derivative materials, lithium-rich manganese-based materials Li 1.2 Ni 0.2 Mn 0.6 O2 and its modified derivative materials, spinel LiNi 0.5 Mn 1.5 At least one of O4 and its modified derivative materials.

[0017] The battery as described above, wherein the charging cut-off voltage of the battery is not less than 4.45V; and / or, The thickness expansion rate of the battery when stored at 85° C. for 6 hours is not higher than 10%; and / or, The thermal runaway trigger temperature of the battery under 1C full charge state is ≥180°C.

[0018] In the battery as described above, when the positive electrode active material layer comprises lithium phytate, after the battery is charged and discharged for 200 cycles at 1C / 1C, the amount of transition metal ions dissolved in the positive electrode active material is not higher than 800 ppm.

[0019] The technical solution provided by the present application may include the following beneficial effects: lithium phytate is added to the positive electrode active material layer, and the phosphate group of lithium phytate can chelate the transition metal ions of the positive electrode active material, effectively inhibiting the dissolution of the transition metal ions, significantly improving the interface stability of the battery, and reducing interface side reactions. Moreover, the phosphorus-oxygen double bonds in lithium phytate can capture free radicals generated by the oxidation of the electrolyte, reduce the decomposition rate of the electrolyte, and reduce the gas production problem. At the same time, the lithium phosphate generated by the decomposition of lithium phytate can form a uniform interface coating on the positive electrode active material layer, reduce the direct contact between the positive electrode active material and the electrolyte, and reduce the occurrence of side reactions, thereby improving the cycle performance, rate performance and storage performance of the battery; on the other hand, lithium phytate is added to the negative electrode active material layer, and lithium phytate decomposes to generate lithium phosphate during the charge and discharge process. Lithium phosphate can be embedded in the SEI film to form a high-conductivity lithium channel, reducing the interface impedance. At the same time, the phosphate group can be preferentially adsorbed on the surface of lithium metal or graphite, regulating the uniform deposition of lithium ions and inhibiting the formation of lithium dendrites. The weak alkalinity of lithium phytate can neutralize the acidic by-products in the negative electrode active material layer, reduce the corrosion of the SEI film, and improve the stability of the SEI film, thereby improving the battery's rate performance, cycle performance and storage performance. In addition, lithium phytate is added to the diaphragm coating. The flame retardant properties of lithium phytate can delay the thermal shrinkage of the diaphragm, improve the thermal stability of the diaphragm, avoid the diaphragm shrinkage at high temperature causing battery short circuit, and improve the high-temperature storage performance of the battery. The phosphate group can improve the surface energy of the diaphragm coating, promote the wettability of the electrolyte to the diaphragm, and improve the ion conductivity of the battery. At the same time, lithium phytate can also form a uniform porous structure in the diaphragm coating, balance the ion transfer rate and mechanical strength of the diaphragm, thereby improving the battery's cycle performance, rate performance and storage performance. When lithium phytate is added to the positive electrode active material layer, the negative electrode active material layer or the separator coating at the same time, lithium phytate can synergistically improve the cycle performance, rate performance and storage performance of the battery in the positive electrode active material layer, the negative electrode active material layer and the separator coating.

[0020] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD diffraction pattern of lithium phytate prepared in Example 1; Figure 2This is the Fourier transform infrared spectrum of the lithium phytate prepared in Example 1; Figure 3 This is a SEM image of the lithium phytate prepared in Example 1; Figure 4 Graphs showing rate performance tests of the batteries of Example 1 and Comparative Example 47; Figure 5 Graphs showing cycle performance tests of the batteries of Example 1 and Comparative Example 47; Figure 6 This is a test diagram of the cycle performance of the batteries of Example 30 and Comparative Example 48. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present application, the present application will be described in detail below. However, before describing the present application in detail, it should be understood that the present application is not limited to the specific embodiments described. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting.

[0023] Where a range of values ​​is provided, it is understood that each intervening value between the upper and lower limits of the range and any other specified or intervening values ​​in the specified range is encompassed herein. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed herein, subject to any express exclusions in the specified range. Where a specified range includes one or both limits, ranges excluding either or both of those included limits are also encompassed herein.

[0024] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. Although any methods and materials equivalent to those described herein can also be used in the practice or testing of this application, preferred methods and materials are now described.

[0025] In the related technology, the currently commonly used high-voltage positive electrode materials still face a series of problems. For example, lithium cobalt oxide positive electrode materials will undergo phase changes at high voltages, affecting the cycle performance and safety of the battery. At the same time, the oxygen free radicals and cobalt ions released by lithium cobalt oxide at high voltages will attack the electrolyte, further deteriorating the battery performance, and may cause thermal runaway of the battery. For example, lithium-rich manganese-based positive electrode materials are prone to phase changes at high voltages, affecting the cycle stability and service life of the battery, and also causing rapid voltage decay. In addition, common problems faced by high-voltage battery systems, such as electrolyte decomposition and gas production, lead to increased internal pressure of the battery, which may cause safety problems. At the same time, side reactions are prone to occur on the surface of the electrode material, deteriorating the cycle performance of the battery.

[0026] In response to the above problems, an embodiment of the present application provides a battery, comprising a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet includes a positive electrode active material layer, the negative electrode sheet includes a negative electrode active material layer, the separator is located between the positive electrode sheet and the negative electrode sheet, and includes a base film and a separator coating provided on at least one side of the base film; wherein, at least one of the positive electrode active material layer, the negative electrode active material layer and the separator coating includes lithium phytate.

[0027] This application does not limit the choice of positive electrode current collector, which can be selected according to actual needs, such as aluminum foil. This application does not limit the choice of negative electrode current collector, which can be selected according to actual needs, such as copper foil. This application does not limit the choice of base film, which can be selected according to actual needs, such as polyethylene separator, polypropylene separator, etc.

[0028] At least one of the positive electrode active material layer, negative electrode active material layer and diaphragm coating of the present application includes lithium phytate, that is, the presence of lithium phytate in the battery can be divided into three situations: the first is that lithium phytate is added to the positive electrode active material layer; the second is that lithium phytate is added to the negative electrode active material layer; the third is that lithium phytate is added to the diaphragm coating; the fourth is that lithium phytate is added to both the positive electrode active material layer and the negative electrode active material layer; the fifth is that lithium phytate is added to both the positive electrode active material layer and the diaphragm coating; the sixth is that lithium phytate is added to both the negative electrode active material layer and the diaphragm coating; the seventh is that lithium phytate is added to the negative electrode active material layer, the diaphragm coating and the positive electrode active material layer.

[0029] According to the above scheme provided in the present application, after the positive electrode sheet, negative electrode sheet and separator are applied to the battery, the battery has excellent rate performance, cycle performance and storage performance at high voltage (voltage ≥ 4.45V). On the one hand, this is because lithium phytate is added to the positive electrode active material layer, and the phosphate group of lithium phytate can chelate the transition metal ions of the positive electrode active material, effectively inhibiting the dissolution of the transition metal ions, significantly improving the interface stability of the battery, and reducing interface side reactions. In addition, the phosphorus-oxygen double bond in lithium phytate can capture the free radicals generated by the oxidation of the electrolyte, reduce the decomposition rate of the electrolyte, and reduce the gas production problem. At the same time, the lithium phosphate generated by the decomposition of lithium phytate can form a uniform interface coating on the positive electrode active material layer, reduce the direct contact between the positive electrode active material and the electrolyte, and reduce the occurrence of side reactions, thereby improving the cycle performance, rate performance and storage performance of the battery; on the other hand, lithium phytate is added to the negative electrode active material layer, and lithium phytate decomposes to form lithium phosphate during the charge and discharge process. Lithium phosphate can be embedded in the SEI film to form a high-conductivity lithium channel, reducing the interface impedance, and at the same time, the phosphate group The groups can be preferentially adsorbed on the surface of lithium metal or graphite, regulating the uniform deposition of lithium ions and inhibiting the formation of lithium dendrites. Moreover, the weak alkalinity of lithium phytate can neutralize the acidic by-products in the negative electrode active material layer, reduce the corrosion of the SEI film, and improve the stability of the SEI film, thereby improving the rate performance, cycle performance and storage performance of the battery. In addition, the addition of lithium phytate to the diaphragm coating, the flame retardant properties of lithium phytate can delay the thermal shrinkage of the diaphragm, improve the thermal stability of the diaphragm, avoid the battery short circuit caused by the shrinkage of the diaphragm at high temperature, and improve the high-temperature storage performance of the battery. Moreover, the phosphate group can improve the surface energy of the diaphragm coating, promote the wettability of the electrolyte to the diaphragm, and improve the ion conductivity of the battery. At the same time, lithium phytate can also form a uniform porous structure in the diaphragm coating, balance the ion transfer rate and mechanical strength of the diaphragm, thereby improving the cycle performance, rate performance and storage performance of the battery. When lithium phytate is added to the positive active material layer, the negative active material layer and / or the separator coating, the lithium phytate can synergistically improve the cycle performance, rate performance and storage performance of the battery in the positive active material layer, the negative active material layer and the separator coating.

[0030] In a specific embodiment, the particle size D50 of lithium phytate is 1 μm to 5 μm, for example, the particle size D50 of lithium phytate is 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, etc. When the particle size of lithium phytate is within the above range, lithium phytate can be better dispersed in the positive electrode active material layer, the negative electrode active material layer and the separator coating, so that lithium phytate can be efficiently decomposed to form lithium phosphate, thereby chelating transition metal ions, improving the interfacial stability of the battery, reducing the decomposition and gas production of the electrolyte, improving the stability and lithium conductivity of the SEI film, inhibiting the formation of lithium dendrites, and increasing the thermal stability, wettability and ion transfer rate of the separator, thereby further improving the cycle performance, rate performance and storage performance of the battery.

[0031] In one embodiment, the specific surface area of ​​lithium phytate is 1 m 2 / g~5m 2 / g, for example, the specific surface area of ​​lithium phytate is 1m 2 / g, 1.5m 2 / g, 2m 2 / g, 2.5m 2 / g、3m 2 / g, 3.5m 2 / g、4m 2 / g, 4.5m 2 / g or 5m 2 / g, etc. When the specific surface area of ​​lithium phytate is within the above range, the porous structure of lithium phytate can decompose into lithium phosphate more quickly, and can form a SEI film with higher stability and interface impedance, further inhibiting the formation of lithium dendrites, making the stability, wettability and lithium conductivity of the separator better, and better inhibiting the dissolution of transition metal ions, thereby making the battery present better cycle performance, rate performance and storage performance.

[0032] In a specific embodiment, in the XRD diffraction pattern of lithium phytate, there is a diffraction peak at a diffraction angle of 2θ = (23 ± 0.5) °, and the half maximum width (FWHM) of the diffraction peak is ≥ 1.0 °, indicating that the lithium phytate has an amorphous structure. When the amorphous structure of lithium phytate is used in a battery, it can increase the migration rate of lithium ions in the lithium phytate and reduce the interfacial impedance of the battery. In addition, the amorphous structure of lithium phytate can better adhere to the electrode surface or the base film surface, reduce the interfacial pores, and at the same time, the isotropic Li + distribution can avoid Li + Aggregation reduces the formation of lithium dendrites, thereby improving the cycle performance, rate performance and storage performance of the battery.

[0033] In a specific embodiment, in the infrared absorption spectrum of lithium phytate, at wave number 780 cm -1 ~890cm -1 、905cm -1 ~1100cm -1 、1101cm -1 ~1205cm -1 There are absorption peaks at the symmetric stretching vibration of POM, PO3 2- Asymmetric stretching vibration, HPO3 - stretching vibration.

[0034] In a specific embodiment, the preparation method of lithium phytate comprises the following steps: mixing a phytic acid solution and a lithium source solution to obtain a salt solution, and then spray drying the salt solution to obtain powdered lithium phytate; wherein the mass ratio of phytic acid to the lithium source is 1: (0.15~3), for example, the mass ratio of phytic acid to the lithium source is 1:0.15, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc.; and / or, the mass percentage of the phytic acid solution is 10%~30%, for example, the mass percentage of the phytic acid solution is 10%, 15%, 20%, 25% or 30%, etc., and the mass percentage of the lithium source solution is 5%~20%; and / or, the mixing temperature of the mixing treatment is 25°C~120°C, the mixing time is 1h~24h and / or, the spraying treatment is carried out in a spray dryer, and the spraying The temperature of the air inlet of the dryer is 215℃~225℃, for example, the temperature of the air inlet is 215℃, 216℃, 217℃, 218℃, 219℃, 220℃, 221℃, 222℃, 223℃, 224℃ or 225℃, etc. The temperature of the air outlet is 60℃~160℃, for example, the temperature of the air outlet is 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 12 0℃, 130℃, 140℃, 150℃ or 160℃, etc., the hot air temperature is 175℃~185℃, for example, the hot air temperature is 175℃, 176℃, 177℃, 178℃, 179℃, 180℃, 181℃, 182℃, 183℃, 184℃ or 185℃, etc., and the drying time is 3s~5s, for example, the drying time is 3s, 3.5s, 4s, 4.5s or 5s, etc.

[0035] Specifically, first, a phytic acid solution with a mass percentage of 10% to 30% and a lithium source solution with a mass percentage of 5% to 20% are prepared, and the mass ratio of phytic acid to lithium source is controlled to be 1:(0.15~3). The phytic acid solution and the lithium source solution are mixed at a temperature of 25°C to 60°C for 1h to 24h to obtain a salt solution; then, the salt solution is added to a spray dryer, and the air inlet temperature of the spray dryer is controlled to be 215°C to 225°C, the air outlet temperature is controlled to be 60°C to 160°C, the hot air temperature is controlled to be 175°C to 185°C, and the mixture is dried for 3s to 5s to obtain lithium phytate powder.

[0036] The present application does not limit the choice of lithium source, which can be selected according to actual needs, for example, lithium hydroxide, lithium carbonate, lithium acetate, lithium chloride, lithium nitrate, etc. can be selected.

[0037] The lithium phytate prepared by the present application has a morphology of a mixture of a sphere and a surface wrinkled spherical shape, which helps to provide a shorter ion diffusion path for lithium ions, improves the rate performance of the battery, and can increase the specific surface area of ​​the lithium phytate, promote the penetration of the electrolyte, and improve the transmission performance of lithium ions, thereby improving the cycle performance of the battery. Moreover, the lithium phytate prepared by the preparation method of the lithium phytate provided by the present application has a suitable particle size and a high specific surface area, which is beneficial to the transition metal ions in the lithium phytate chelate battery, improves the interfacial stability of the battery, reduces the decomposition and gas production of the electrolyte, improves the stability and lithium ion conductivity of the SEI film, suppresses the generation of lithium dendrites, increases the thermal stability, wettability and ion transmission rate of the diaphragm, thereby improving the cycle performance, rate performance and storage performance of the battery.

[0038] In one embodiment, before the lithium phytate powder is applied to the positive electrode active material layer, the negative electrode active material layer, or the separator coating, the moisture content in the lithium phytate should be controlled to ≤200ppm to prevent the moisture in the lithium phytate from inducing side reactions in the battery and causing degradation of battery performance. This application does not limit the method for controlling the moisture content in the lithium phytate. For example, the lithium phytate can be vacuum-dried at 120°C for 4 to 20 hours. The moisture content in the lithium phytate powder of this application can be detected by the Karl Fischer method.

[0039] In a specific embodiment, the positive electrode active material layer includes a positive electrode active material and lithium phytate, and the mass ratio of lithium phytate to the mass ratio of the positive electrode active material is 0.5% to 2%, for example, the mass ratio of lithium phytate to the mass ratio of the positive electrode active material is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%. When the mass ratio of lithium phytate to the positive electrode active material is within the above range, the phosphate groups of the appropriate amount of lithium phytate can chelate more transition metal ions of the positive electrode active material, further inhibiting the dissolution of transition metal ions, improving the interfacial stability of the battery, and more efficiently capturing free radicals generated by oxidation of the electrolyte, further reducing gas generation problems. At the same time, it can form a better interfacial coating on the positive electrode active material layer, reducing the occurrence of side reactions, thereby enabling the battery to exhibit better cycle performance, rate performance, and storage performance.

[0040] In a specific embodiment, the positive electrode active material layer includes a positive electrode active material and lithium phytate, and the positive electrode active material layer satisfies the following relationship: m 植酸锂 / m 正极活性材料 =k×S 正极活性材料 / S 植酸锂 Formula 1 In equation 1, m 植酸锂 is the amount of lithium phytate added to the positive electrode active material layer; m正极活性材料 is the amount of positive electrode active material added to the positive electrode active material layer; k is 0.005~0.2; S 正极活性材料 is the specific surface area of ​​the positive electrode active material; S 植酸锂 is the specific surface area of ​​lithium phytate.

[0041] The mass ratio of lithium phytate to the positive electrode active material in the positive electrode active material layer is inversely proportional to the ratio of the specific surface area of ​​lithium phytate to the positive electrode active material. This application does not limit the specific surface area of ​​the positive electrode active material, and it only needs to satisfy the above formula 1. For example, the specific surface area of ​​the positive electrode active material can be 0.5m 2 / g~3.5m 2 / g. Preferably, the ratio of the specific surface area of ​​lithium phytate to the positive electrode active material is within a range of 0.1 to 3.5. When the lithium phytate and the positive electrode active material in the positive electrode active material layer satisfy the above relationship, the lithium phytate can better chelate the transition metal ions in the positive electrode active material, preventing the dissolution of the transition metal ions. At the same time, it can provide better interface coating for the positive electrode active material, greatly reducing side reactions and improving the battery's cycle performance, rate performance, and storage performance.

[0042] In one embodiment, the method for preparing the positive electrode sheet includes the following steps: S1. Performing a first mixing process on the positive electrode binder and the solvent to obtain a positive electrode binder mixed solution.

[0043] Among them, the mass ratio of the positive electrode binder to the solvent is 0.6~1.4, for example, the mass ratio can be 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or 1.4, etc.; and / or, the first mixing treatment is performed by stirring treatment, the stirring temperature is 20℃~60℃, for example, the stirring temperature can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, etc., and the stirring speed is 10rpm~600rpm, for example, the speed can be 10rpm, 50rpm, 100rpm, 200rpm, 300rpm, 400rpm, 500rpm or 600rpm, etc.

[0044] S2. Adding a positive electrode active material, a positive electrode conductive agent, and lithium phytate to the positive electrode binder mixed solution to perform a second mixing process to obtain a positive electrode slurry.

[0045] The mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (80-98): (1-10): (1-10), for example, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder can be 80:10:10, 85:7.5:7.5, 90:5:5, 95:2.5:2.5, or 98:1:1, etc.; and / or, the viscosity of the positive electrode slurry is 3500 mPa.s-6000 mPa.s. Pa.s, for example, the viscosity of the positive electrode slurry may be 3500mPa.s, 4000mPa.s, 4500mPa.s, 5000mPa.s, 5500mPa.s or 6000mPa.s, etc.; and / or, the compatibility index (CI) between lithium phytate and the solvent in the positive electrode slurry is ≤0.1, for example, the compatibility index may be 0.01, 0.02, 0.04, 0.06, 0.08 or 0.1, etc.

[0046] S3. Apply the positive electrode slurry to at least one side of the positive electrode current collector and perform a first drying process to obtain a positive electrode sheet.

[0047] The first drying treatment is drying under vacuum conditions at 115° C. to 125° C. for 10 to 12 hours; and / or the mass percentage of the solvent in the positive electrode active material layer after the first drying treatment is not higher than 0.1%.

[0048] Specifically, S1. Stirring the positive electrode binder and the solvent in a mass ratio of 0.6~1.4 at 20℃~60℃, with a stirring speed of 10rpm~600rpm to obtain a positive electrode binder mixed solution; S2. Adding a positive electrode active material, a positive electrode conductive agent and lithium phytate to the positive electrode binder mixed solution for mixing, controlling the mass ratio of the positive electrode active material, the positive electrode conductive agent and the lithium phytate to be (80~98):(1~10):(1~10), and stirring at a low speed under vacuum conditions to remove bubbles, to obtain a positive electrode slurry with a viscosity of 3500mPa.s~6000mPa.s, and the compatibility index (CI) of the lithium phytate and the solvent in the positive electrode slurry is ≤0.1; S3. Coating the positive electrode slurry on at least one side surface of the positive electrode current collector, and drying it under vacuum conditions at 115℃~125℃ for 10h~12h to make the residual solvent content ≤0.1wt%, to obtain a positive electrode sheet.

[0049] It is worth noting that lithium phytate is vacuum dried at 120°C for 12h~18h to make the moisture content in lithium phytate ≤200ppm before being applied to the positive electrode slurry to avoid the negative impact of moisture in lithium phytate on the positive electrode active material layer.

[0050] The compatibility index of lithium phytate and solvent in the positive electrode slurry of the present application refers to the ratio of the volume of the precipitate in the positive electrode slurry to the total volume of the positive electrode slurry, that is, CI = precipitate volume / total slurry volume × 100%.

[0051] The present application does not limit the choice of solvent, which can be selected according to actual needs, such as N-methylpyrrolidone (NMP). The present application does not limit the choice of positive electrode active material, which can be selected according to actual needs, such as high-voltage LiCoO2 (charge cut-off voltage ≥ 4.45V) and its modified derivatives, lithium-rich manganese-based materials Li 1.2 Ni 0.2 Mn 0.6 O2 and its modified derivative materials, spinel LiNi 0.5 Mn 1.5 O4 (cutoff voltage 4.9V) and its modified derivatives. This application does not limit the choice of positive electrode conductive agent, which can be selected according to actual needs, such as carbon black, carbon nanotubes, etc. This application does not limit the choice of positive electrode binder, which can be selected according to actual needs, such as styrene-butadiene rubber, carboxymethyl cellulose, or a combination thereof.

[0052] Through the preparation method of the positive electrode sheet provided in the present application, lithium phytate can be adapted to the N-methylpyrrolidone solvent system, which can enable lithium phytate to efficiently chelate transition metal ions, reduce the dissolution amount of transition metal ions, improve the interface stability of the battery, reduce interface side reactions, and reduce the decomposition and gas production problem of the electrolyte. At the same time, the interface coating of the positive electrode active material layer is more uniform, so that the direct contact between the positive electrode active material and the electrolyte is less, thereby improving the battery's cycle performance, rate performance and storage performance.

[0053] In a specific embodiment, the diaphragm coating includes lithium phytate, and the mass percentage of lithium phytate in the diaphragm coating is 1% to 20%, for example, the mass percentage of lithium phytate in the diaphragm coating can be 1%, 2%, 5%, 10%, 15% or 20%, etc. The thickness of the diaphragm coating is 0.1μm to 5μm, for example, the thickness of the diaphragm coating is 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm, etc. When the mass percentage of lithium phytate in the diaphragm coating and the thickness of the diaphragm coating are within the above ranges, the lithium phytate can better retard the thermal shrinkage of the diaphragm, improve the thermal stability of the diaphragm, further improve the wettability of the electrolyte to the diaphragm, improve the ionic conductivity of the battery, and better balance the ion transfer rate and mechanical strength of the diaphragm, thereby improving the cycle performance, rate performance and storage performance of the battery.

[0054] In one embodiment, the method for preparing the diaphragm comprises the following steps: S1. Disperse alumina ceramics, lithium phytate, diaphragm conductive agent, and diaphragm binder in water and mix them evenly to obtain diaphragm coating slurry. Wherein, the mass ratio of alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder is (50-70): (1-20): (10-25): (5-15), for example, the mass ratio of alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder can be 50:20:25:5, 60:10:15:15, 70:5:10:15, or 70:1:24:5, etc.; and / or, the solid content of the diaphragm coating slurry is 15%-25%, for example, the solid content can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%, etc.; S2, applying the membrane coating slurry to at least one side of the base film, and drying the base film to obtain the membrane; The diaphragm coating slurry is coated by coating, and the coating gap is 10 μm to 20 μm, for example, the coating gap can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm, etc.; and / or, the drying process is a gradient drying process, after drying at 80°C to 100°C for 1min to 3min, for example, the drying temperature can be 80°C, 85°C, 90°C, 95°C or 100℃, etc., the drying time is 1min, 1.5min, 2min, 2.5min or 3min, etc., the temperature is raised to 120℃~150℃ and dried for 2min~5min. For example, the drying temperature can be 120℃, 125℃, 130℃, 135℃, 140℃, 145℃ or 150℃, etc., and the drying time is 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min, etc.

[0055] Specifically, S1. Mix alumina ceramic, lithium phytate, a diaphragm conductive agent, a diaphragm binder and water, control the mass ratio of lithium phytate, the diaphragm conductive agent and the diaphragm binder to be (50~70): (1~20): (10~25): (5~15), and control the amount of water to obtain a diaphragm coating slurry with a solid content of 15%~25%; S2. Apply the diaphragm coating slurry to at least one side surface of the base film through a micro-gravure coating process, control the coating gap to be 10μm~20μm, and adopt gradient drying, that is, dry at 80℃~100℃ for 1min~3min, then heat to 120℃~150℃ and dry for 2min~5min to obtain a diaphragm.

[0056] This application does not limit the choice of separator conductive agent, which can be selected based on actual needs. For example, at least one of nano-alumina (Al2O3), nano-silicon oxide (SiO2), boron nitride (BN), and carbon nanotubes (CNTs) can be selected. This application does not limit the choice of separator binder, which can be selected based on actual needs. For example, at least one of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyvinyl alcohol (PVA), and polydopamine (PDA) can be selected. This application does not limit the choice of base film, which can be selected based on actual needs. For example, polyethylene separators, polypropylene separators, etc. can be selected.

[0057] The above-mentioned method for preparing the diaphragm can prepare a diaphragm containing lithium phytate, which makes the diaphragm more thermally stable and improves the storage performance of the battery. At the same time, it can improve the wettability of the diaphragm, improve the ionic conductivity of the battery, and improve the cycle performance and rate performance of the battery.

[0058] In one specific embodiment, the negative electrode active material layer includes a negative electrode binder and lithium phytate, and the mass proportion of lithium phytate in the negative electrode binder is 0.5% to 2%, for example, the mass proportion of lithium phytate in the negative electrode binder is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2%. This application does not limit the choice of negative electrode binder, and it can be selected according to actual needs. For example, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyimide (PI), etc. can be selected. When the amount of lithium phytate added to the negative electrode active material layer is within the above range, an appropriate amount of lithium phytate decomposes into lithium phosphate, which can be embedded in the SEI film to form a high-conductivity lithium channel, reducing the interfacial impedance, while better inhibiting the formation of lithium dendrites, reducing the corrosion of the SEI film, and improving the stability of the SEI film, thereby improving the battery's rate performance, cycle performance, and storage performance.

[0059] In one embodiment, the method for preparing the negative electrode sheet includes the following steps: S1. Disperse the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder in water and mix them evenly to obtain a negative electrode mixture.

[0060] The mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (90-96): (1-5): (2-5), for example, the mass ratio can be 90:5:5, 92:4:4, 94:3:3, 96:2:2, 96:1:3, etc.

[0061] S2. adding a lithium phytate solution to the negative electrode mixture and performing a dispersion treatment to obtain a negative electrode slurry; The dispersion treatment is carried out by stirring at a speed of 300 rpm to 800 rpm for 60 min to 120 min, for example, the speed can be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, etc., the stirring time can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, etc., and ultrasonic dispersion is carried out at a power of 20 W to 50 W for 30 min to 60 min, for example, the ultrasonic dispersion power can be 20 W, 25 W, 30 W, 35 W, 40 W, 50 W, 60 W, 70 W, 80 W, 90 W, 100 W, 110 W or 120 W. 5W, 40W, 45W or 50W, for example, the ultrasonic dispersion time can be 30min, 35min, 40min, 45min, 50min, 55min or 60min, etc.; and / or, the pH of the negative electrode slurry is 7-9, for example, the pH of the negative electrode slurry can be 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8 or 9, etc.; and / or, the solid content of the negative electrode slurry is 40%-55%, for example, the solid content can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 55%, etc.

[0062] S3. Coating the negative electrode slurry on at least one side of the negative electrode current collector and performing a second drying process to obtain a negative electrode sheet.

[0063] The second drying treatment is drying under vacuum conditions at 115° C. to 125° C. for 10 to 12 hours; and / or the mass percentage of water in the negative electrode active material layer after the second drying treatment is not higher than 0.1%.

[0064] Specifically, S1, mixing the negative electrode active material, the negative electrode conductive agent, the negative electrode binder, and water, controlling the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder to be (90-96): (1-5): (2-5), and controlling the amount of water added to obtain a negative electrode mixture; S2, dissolving lithium phytate in water to obtain a lithium phytate solution, and dispersing the lithium phytate solution and the negative electrode mixture, that is, stirring at a speed of 300 rpm to 800 rpm for 60 min to 12 0min, ultrasonically disperse at a power of 20W~50W for 30min~60min, and add water or ethanol-water mixture at the same time to adjust the solid content of the negative electrode slurry to 40%~55%, and add pH regulator to the negative electrode slurry to control the pH of the negative electrode slurry to 7~9; S3, apply the negative electrode slurry on at least one side of the negative electrode current collector, and dry it under vacuum conditions at 115℃~125℃ for 10h~12h to make the residual water content ≤0.1wt% to obtain a negative electrode sheet.

[0065] It is worth noting that lithium phytate is vacuum dried at 115°C~125°C for 12h~18h to make the moisture content in lithium phytate ≤200ppm before being applied to the negative electrode slurry to avoid the negative impact of moisture in lithium phytate on the negative electrode active material layer.

[0066] This application does not limit the choice of negative electrode active material, which can be selected according to actual needs, such as graphite, silicon carbon or their composite materials. This application does not limit the choice of negative electrode conductive agent, which can be selected according to actual needs, such as carbon black, carbon nanotubes, etc. This application does not limit the choice of negative electrode binder, which can be selected according to actual needs, such as styrene-butadiene rubber, carboxymethyl cellulose or a combination thereof. This application does not limit the choice of pH adjuster, which can be selected according to actual needs, such as ammonia water, citric acid, etc.

[0067] The present application controls the pH of the negative electrode slurry within the range of 7 to 9, which can maintain the stability of the negative electrode slurry and avoid hydrolysis of lithium phytate, laying the foundation for the subsequent preparation of the negative electrode sheet.

[0068] The preparation method of the negative electrode sheet provided in this application enables lithium phytate to be evenly dispersed in the negative electrode active material layer, indicating that lithium phytate is compatible with aqueous solution systems, helps reduce the impedance of the SEI film, and can regulate the uniform deposition of lithium ions, reduce the formation of lithium dendrites, and simultaneously reduce the corrosion of the SEI film by acidic byproducts in the negative electrode active material layer, thereby improving the stability of the SEI film and thus improving the battery's rate performance, cycle performance, and storage performance. In addition, the preparation process is simple and efficient, which can reduce the production cost of the battery.

[0069] In a specific embodiment, the positive electrode active material includes high-voltage LiCoO2 (charge cut-off voltage ≥ 4.45V) and its modified derivatives, lithium-rich manganese-based materials Li 1.2 Ni 0.2 Mn 0.6 O2 and its modified derivative materials, spinel LiNi 0.5 Mn 1.5 At least one of O4 (cut-off voltage 4.9V) and its modified derivatives. When the above materials are used as the positive electrode active material, the positive electrode active material can withstand high voltage, avoiding problems such as damage and cracking under high-voltage environments. At the same time, lithium phytate can chelate the positive electrode active material and reduce direct contact between the positive electrode active material and the electrolyte, thereby improving the battery's cycle performance, rate performance, and storage performance.

[0070] In a specific embodiment, the charging cut-off voltage of the battery is not less than 4.45V, that is, the battery can maintain stable charging and discharging operation at a high voltage, thereby expanding the application range of the battery.

[0071] In one embodiment, the thickness expansion rate of the battery after storage at 85°C for 6 hours is no more than 10%. The battery of the present application has excellent high-temperature storage performance, avoiding excessive expansion rate under high temperature conditions that may cause battery damage or explosion, thereby degrading battery safety performance.

[0072] In a specific embodiment, the thermal runaway trigger temperature of the battery under 1C full charge state is ≥180°C, indicating that the battery exhibits excellent thermal safety performance.

[0073] In one specific embodiment, the positive electrode active material layer includes lithium phytate. After the battery is cycled at 1C / 1C for 200 cycles, the amount of transition metal ions dissolved from the positive electrode active material is no more than 800 ppm. This low amount of transition metal ion dissolution in this battery can improve the battery's interfacial stability, reduce interfacial side reactions, and enhance the battery's cycling performance, rate capability, and storage performance.

[0074] In a specific embodiment, the battery of the present application further includes an electrolyte, which is a well-known electrolyte in the art that can be used in batteries and has excellent electrochemical performance of the battery, including lithium salts and organic solvents, and can be specifically configured as needed.

[0075] In a specific embodiment, the battery may include an outer packaging, which can be used to encapsulate the electrode assembly and the electrolyte.

[0076] In one embodiment, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0077] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape.

[0078] This application has no particular restrictions on the application fields of secondary batteries, and they can be used in consumer electronics, new energy vehicles, energy storage and other fields.

[0079] The present application is further described in detail below through specific examples.

[0080] Example 1 Adding lithium phytate to the positive electrode active material layer 1. Preparation of lithium phytate First, a phytic acid solution with a mass percentage of 20% (phytic acid purity ≥ 95%) and a lithium hydroxide solution with a mass percentage of 15% (lithium salt purity ≥ 99%) were prepared, and the mass ratio of phytic acid to lithium hydroxide was controlled to be 1:1.8. The phytic acid solution and the lithium source solution were mixed at a temperature of 45°C for 1 hour to obtain a salt solution; then the salt solution was added to a spray dryer, and the air inlet temperature of the spray dryer was controlled to be 220°C, the air outlet temperature was controlled to be 80°C, the hot air temperature was controlled to be 180°C, and the mixture was dried for 4 seconds to obtain lithium phytate.

[0081] 2. Preparation of positive electrode PVDF and NMP were stirred at a mass ratio of 1:1 at 40°C and a stirring speed of 300 rpm to obtain a PVDF mixed solution. Subsequently, the positive electrode active material lithium cobalt oxide (specific surface area S 正极活性材料 0.86m 2 / g), positive electrode conductive agent carbon black and lithium phytate are mixed, the mass ratio of lithium cobaltate, carbon black and PVDF is controlled to be 90:5:5, and lithium phytate powder is added at a mass ratio of lithium cobaltate: lithium phytate = 100:1, and bubbles are removed by low-speed stirring under vacuum conditions to obtain a positive electrode slurry with a viscosity of 4500mPa.s, and the compatibility index (CI) of lithium phytate and solvent in the positive electrode slurry is ≤0.1; finally, the positive electrode slurry is coated on at least one side of the positive electrode current collector, and dried under vacuum conditions at 120°C for 12h to make the residual solvent content 0.05wt%, to obtain a positive electrode sheet.

[0082] The mass ratio of lithium phytate to the positive electrode active material lithium cobalt oxide is 1%; the ratio of the specific surface area of ​​lithium cobalt oxide to the specific surface area of ​​lithium phytate is 0.26, and k is calculated to be 0.038.

[0083] 3. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder, and water are mixed, and the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is controlled to be 94:3:3 to obtain a negative electrode slurry with a solid content of 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to be 7.5±0.2, and finally the negative electrode slurry is coated on at least one side of the copper foil and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0084] 4. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0085] 5. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence and wound with a polypropylene separator to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected and vacuum-sealed, allowed to stand, formed, and shaped to produce a lithium-ion battery.

[0086] The main difference between Examples 2 to 15 and Comparative Examples 1 to 14 and Example 1 is that the preparation parameters of lithium phytate are different, see Table 1.

[0087] Table 1

[0088] The main difference between Examples 16 to 29 and Comparative Examples 15 to 26 and Example 1 is the different preparation parameters of the positive electrode sheets, see Table 2.

[0089] Table 2

[0090] Example 30 Adding lithium phytate to the separator coating 1. Preparation of lithium phytate The preparation method of lithium phytate in this embodiment is the same as the preparation method of lithium phytate in Example 1.

[0091] 2. Preparation of diaphragm Mixing lithium phytate, nano-alumina, a diaphragm conductive agent, a diaphragm binder, and water, controlling the mass ratio of lithium phytate, nano-alumina, the diaphragm conductive agent, and the diaphragm binder to be 5:60:20:15, and controlling the amount of water to obtain a diaphragm coating slurry with a solid content of 20%; then coating the diaphragm coating slurry on at least one side of the base film by a micro-gravure coating process, controlling the coating gap to be 15 μm, and adopting gradient drying, that is, drying at 80° C. for 3 minutes, then heating to 130° C. for drying for 3 minutes, to obtain a diaphragm; The mass percentage of lithium phytate in the diaphragm coating is 5%, and the thickness of the diaphragm coating is 4 μm.

[0092] 3. Preparation of positive electrode The positive electrode active material, a lithium-rich manganese-based material, the positive electrode conductive agent, carbon black, and the positive electrode binder, PVDF, were mixed uniformly in a mass ratio of 90:5:5. The mixture was thoroughly stirred in an N-methylpyrrolidone solvent to form a slurry with a solid content of 50%. This was then stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on at least one side of an aluminum foil and dried under vacuum at 120°C for 12 hours to reduce the residual solvent content to 0.05wt%, thereby obtaining a positive electrode sheet.

[0093] 4. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder and water are mixed, and the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is controlled to be 95:2:3 to obtain a negative electrode slurry with a solid content of 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to be 7.5±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0094] 5. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0095] 6. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence, and the stacked electrodes and separator are wound to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film, dehydrated at 80°C, and injected with the prepared electrolyte. After vacuum packaging, static standing, formation, and shaping, the lithium-ion battery is obtained.

[0096] The main difference between Examples 31 to 41, Comparative Examples 27 to 36 and Example 30 is the different preparation parameters of the diaphragms, see Table 3.

[0097] Table 3

[0098] Example 42 Adding lithium phytate to the negative electrode active material layer 1. Preparation of lithium phytate The preparation method of lithium phytate in this embodiment is the same as the preparation method of lithium phytate in Example 1.

[0099] 2. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder and water are mixed, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is controlled to be 96:2:2, and the amount of water added is controlled to obtain a mixture; then lithium phytate is dissolved in water to obtain a lithium phytate solution, and the lithium phytate solution and the mixture are dispersed, that is, stirred at a speed of 500 rpm for 90 minutes, ultrasonically dispersed at a power of 30 W for 45 minutes, and water is added at the same time to adjust the solid content of the negative electrode slurry to 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to 7.8±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil, and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0100] The mass ratio of lithium phytate to the negative electrode binder is 1%.

[0101] 3. Preparation of positive electrode The positive electrode active material, lithium cobalt oxide, the positive electrode conductive agent, carbon black, and the positive electrode binder, PVDF, were mixed uniformly in a mass ratio of 90:5:5. The mixture was thoroughly stirred in N-methylpyrrolidone solvent to form a slurry with a viscosity of 4500 mPa·s. This was then stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on at least one side of an aluminum foil and dried under vacuum at 120°C for 12 hours to reduce the residual solvent content to 0.05 wt%, resulting in a positive electrode sheet.

[0102] 4. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0103] 5. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence and wound with a polypropylene separator to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected and vacuum-sealed, allowed to stand, formed, and shaped to produce a lithium-ion battery.

[0104] The main difference between Examples 43 to 52, Comparative Examples 37 to 46 and Example 42 is the different preparation parameters of the negative electrode sheets, see Table 4.

[0105] Table 4

[0106] Example 53 Adding lithium phytate to the positive electrode active material layer and the negative electrode active material layer 1. Preparation of lithium phytate The preparation method of lithium phytate in this embodiment is the same as the preparation method of lithium phytate in Example 1.

[0107] 2. Preparation of positive electrode PVDF and NMP were stirred at a mass ratio of 1:1 at 40°C and a stirring speed of 300 rpm to obtain a PVDF mixed solution. Subsequently, the positive electrode active material lithium cobalt oxide (specific surface area S 正极活性材料 0.86m 2 / g), positive electrode conductive agent carbon black and lithium phytate are mixed, the mass ratio of lithium cobaltate, carbon black and PVDF is controlled to be 90:5:5, and lithium phytate powder is added at a mass ratio of lithium cobaltate: lithium phytate = 100:1, and bubbles are removed by low-speed stirring under vacuum conditions to obtain a positive electrode slurry with a viscosity of 4500mPa.s, and the compatibility index (CI) of lithium phytate and solvent in the positive electrode slurry is ≤0.1; finally, the positive electrode slurry is coated on at least one side of the positive electrode current collector, and dried under vacuum conditions at 120°C for 12h to make the residual solvent content 0.05wt%, to obtain a positive electrode sheet.

[0108] The mass ratio of lithium phytate to the positive electrode active material lithium cobalt oxide is 1%; the ratio of the specific surface area of ​​lithium cobalt oxide to the specific surface area of ​​lithium phytate is 0.26, and k is calculated to be 0.038.

[0109] 3. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder and water are mixed, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is controlled to be 96:2:2, and the amount of water added is controlled to obtain a mixture; then lithium phytate is dissolved in water to obtain a lithium phytate solution, and the lithium phytate solution and the mixture are dispersed, that is, stirred at a speed of 500 rpm for 90 minutes, ultrasonically dispersed at a power of 30 W for 45 minutes, and water is added at the same time to adjust the solid content of the negative electrode slurry to 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to 7.8±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil, and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0110] The mass ratio of lithium phytate to the negative electrode binder is 1%.

[0111] 4. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0112] 5. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence and wound with a polypropylene separator to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected and vacuum-sealed, allowed to stand, formed, and shaped to produce a lithium-ion battery.

[0113] Example 54 Adding lithium phytate to the negative electrode active material layer and separator coating 1. Preparation of lithium phytate The preparation method of lithium phytate in this embodiment is the same as the preparation method of lithium phytate in Example 1.

[0114] 2. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder and water are mixed, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is controlled to be 96:2:2, and the amount of water added is controlled to obtain a mixture; then lithium phytate is dissolved in water to obtain a lithium phytate solution, and the lithium phytate solution and the mixture are dispersed, that is, stirred at a speed of 500 rpm for 90 minutes, ultrasonically dispersed at a power of 30 W for 45 minutes, and water is added at the same time to adjust the solid content of the negative electrode slurry to 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to 7.8±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil, and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0115] The mass ratio of lithium phytate to the negative electrode binder is 1%.

[0116] 3. Preparation of diaphragm Mixing lithium phytate, nano-alumina, a diaphragm conductive agent, a diaphragm binder, and water, controlling the mass ratio of lithium phytate, nano-alumina, the diaphragm conductive agent, and the diaphragm binder to be 5:60:20:15, and controlling the amount of water to obtain a diaphragm coating slurry with a solid content of 20%; then coating the diaphragm coating slurry on at least one side of the base film by a micro-gravure coating process, controlling the coating gap to be 15 μm, and adopting gradient drying, that is, drying at 80° C. for 3 minutes, then heating to 130° C. for drying for 3 minutes, to obtain a diaphragm; The mass percentage of lithium phytate in the diaphragm coating is 5%, and the thickness of the diaphragm coating is 4 μm.

[0117] 4. Preparation of positive electrode The positive electrode active material, lithium cobalt oxide, the positive electrode conductive agent, carbon black, and the positive electrode binder, PVDF, were mixed uniformly in a mass ratio of 90:5:5. The mixture was thoroughly stirred in N-methylpyrrolidone solvent to form a slurry with a viscosity of 4500 mPa·s. This was then stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on at least one side of an aluminum foil and dried under vacuum at 120°C for 12 hours to reduce the residual solvent content to 0.05 wt%, resulting in a positive electrode sheet.

[0118] 5. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0119] 6. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence, and the stacked electrodes and separator are wound to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film, dehydrated at 80°C, and injected with the prepared electrolyte. After vacuum packaging, static standing, formation, and shaping, the lithium-ion battery is obtained.

[0120] Example 55 Adding lithium phytate to the separator coating and the positive electrode active material layer 1. Preparation of lithium phytate The preparation method of lithium phytate in this embodiment is the same as the preparation method of lithium phytate in Example 1.

[0121] 2. Preparation of diaphragm Mixing lithium phytate, nano-alumina, a diaphragm conductive agent, a diaphragm binder, and water, controlling the mass ratio of lithium phytate, nano-alumina, the diaphragm conductive agent, and the diaphragm binder to be 5:60:20:15, and controlling the amount of water to obtain a diaphragm coating slurry with a solid content of 20%; then coating the diaphragm coating slurry on at least one side of the base film by a micro-gravure coating process, controlling the coating gap to be 15 μm, and adopting gradient drying, that is, drying at 80° C. for 3 minutes, then heating to 130° C. for drying for 3 minutes, to obtain a diaphragm; The mass percentage of lithium phytate in the diaphragm coating is 5%, and the thickness of the diaphragm coating is 4 μm.

[0122] 3. Preparation of positive electrode PVDF and NMP were stirred at a mass ratio of 1:1 at 40°C and a stirring speed of 300 rpm to obtain a PVDF mixed solution. Subsequently, the positive electrode active material lithium cobalt oxide (specific surface area S 正极活性材料 0.86m 2 / g), positive electrode conductive agent carbon black and lithium phytate are mixed, the mass ratio of lithium cobaltate, carbon black and PVDF is controlled to be 90:5:5, and lithium phytate powder is added at a mass ratio of lithium cobaltate: lithium phytate = 100:1, and bubbles are removed by low-speed stirring under vacuum conditions to obtain a positive electrode slurry with a viscosity of 4500mPa.s, and the compatibility index (CI) of lithium phytate and solvent in the positive electrode slurry is ≤0.1; finally, the positive electrode slurry is coated on at least one side of the positive electrode current collector, and dried under vacuum conditions at 120°C for 12h to make the residual solvent content 0.05wt%, to obtain a positive electrode sheet.

[0123] The mass ratio of lithium phytate to the positive electrode active material lithium cobalt oxide is 1%; the ratio of the specific surface area of ​​lithium cobalt oxide to the specific surface area of ​​lithium phytate is 0.26, and k is calculated to be 0.038.

[0124] 4. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder and water are mixed, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is controlled to be 96:2:2, and the amount of water added is controlled to obtain a mixture; then lithium phytate is dissolved in water to obtain a lithium phytate solution, and the lithium phytate solution and the mixture are dispersed, that is, stirred at a speed of 500 rpm for 90 minutes, ultrasonically dispersed at a power of 30 W for 45 minutes, and water is added at the same time to adjust the solid content of the negative electrode slurry to 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to 7.8±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil, and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0125] The mass ratio of lithium phytate to the negative electrode binder is 1%.

[0126] 5. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0127] 6. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence, and the stacked electrodes and separator are wound to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film, dehydrated at 80°C, and injected with the prepared electrolyte. After vacuum packaging, static standing, formation, and shaping, the lithium-ion battery is obtained.

[0128] Example 56 Adding lithium phytate to the negative electrode active material layer, separator coating, and positive electrode active material layer 1. Preparation of lithium phytate The preparation method of lithium phytate in this embodiment is the same as the preparation method of lithium phytate in Example 1.

[0129] 2. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder and water are mixed, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is controlled to be 96:2:2, and the amount of water added is controlled to obtain a mixture; then lithium phytate is dissolved in water to obtain a lithium phytate solution, and the lithium phytate solution and the mixture are dispersed, that is, stirred at a speed of 500 rpm for 90 minutes, ultrasonically dispersed at a power of 30 W for 45 minutes, and water is added at the same time to adjust the solid content of the negative electrode slurry to 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to 7.8±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil, and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0130] The mass ratio of lithium phytate to the negative electrode binder is 1%.

[0131] 3. Preparation of diaphragm Mixing lithium phytate, nano-alumina, a diaphragm conductive agent, a diaphragm binder, and water, controlling the mass ratio of lithium phytate, nano-alumina, the diaphragm conductive agent, and the diaphragm binder to be 5:60:20:15, and controlling the amount of water to obtain a diaphragm coating slurry with a solid content of 20%; then coating the diaphragm coating slurry on at least one side of the base film by a micro-gravure coating process, controlling the coating gap to be 15 μm, and adopting gradient drying, that is, drying at 80° C. for 3 minutes, then heating to 130° C. for drying for 3 minutes, to obtain a diaphragm; The mass percentage of lithium phytate in the diaphragm coating is 5%, and the thickness of the diaphragm coating is 4 μm.

[0132] 4. Preparation of positive electrode PVDF and NMP were stirred at a mass ratio of 1:1 at 40°C and a stirring speed of 300 rpm to obtain a PVDF mixed solution. Subsequently, the positive electrode active material lithium cobalt oxide (specific surface area S 正极活性材料 0.86m 2 / g), positive electrode conductive agent carbon black and lithium phytate are mixed, the mass ratio of lithium cobaltate, carbon black and PVDF is controlled to be 90:5:5, and lithium phytate powder is added at a mass ratio of lithium cobaltate: lithium phytate = 100:1, and bubbles are removed by low-speed stirring under vacuum conditions to obtain a positive electrode slurry with a viscosity of 4500mPa.s, and the compatibility index (CI) of lithium phytate and solvent in the positive electrode slurry is ≤0.1; finally, the positive electrode slurry is coated on at least one side of the positive electrode current collector, and dried under vacuum conditions at 120°C for 12h to make the residual solvent content 0.05wt%, to obtain a positive electrode sheet.

[0133] The mass ratio of lithium phytate to the positive electrode active material lithium cobalt oxide is 1%; the ratio of the specific surface area of ​​lithium cobalt oxide to the specific surface area of ​​lithium phytate is 0.26, and k is calculated to be 0.038.

[0134] 5. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0135] 6. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence, and the stacked electrodes and separator are wound to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film, dehydrated at 80°C, and injected with the prepared electrolyte. After vacuum packaging, static standing, formation, and shaping, the lithium-ion battery is obtained.

[0136] Comparative Example 47 1. Preparation of negative electrode sheet The negative electrode active material graphite, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder, and water are mixed, and the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is controlled to be 96:2:2 to obtain a negative electrode slurry with a solid content of 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to be 7.5±0.2; finally, the negative electrode slurry is coated on at least one side of the copper foil and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0137] 2. Preparation of positive electrode The positive electrode active material, lithium cobalt oxide, the positive electrode conductive agent, carbon black, and the positive electrode binder, PVDF, were mixed uniformly in a mass ratio of 90:5:5. The mixture was thoroughly stirred in N-methylpyrrolidone solvent to form a slurry with a viscosity of 4500 mPa·s. This was then stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on at least one side of an aluminum foil and dried under vacuum at 120°C for 12 hours to reduce the residual solvent content to 0.05 wt%, resulting in a positive electrode sheet.

[0138] 3. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0139] 4. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence and wound with a polypropylene separator to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected and vacuum-sealed, allowed to stand, formed, and shaped to produce a lithium-ion battery.

[0140] Comparative Example 48 1. Preparation of diaphragm Nano-alumina, an adhesive, and water are mixed, and the mass ratio of lithium phytate, nano-alumina, and the adhesive is controlled to be 65:20:15. The amount of water is also controlled to obtain a diaphragm coating slurry with a solid content of 20%. The diaphragm coating slurry is then coated on at least one side of the base film by a micro-gravure coating process, with a coating gap of 15 μm. Gradient drying is performed, i.e., drying at 80° C. for 3 minutes, then heating to 130° C. for 3 minutes, to obtain a diaphragm. The mass percentage of lithium phytate in the diaphragm coating is 5%, and the thickness of the diaphragm coating is 4 μm.

[0141] 2. Preparation of negative electrode sheet The negative electrode active material graphite-silicon carbon composite material, the negative electrode conductive agent carbon nanotubes, the negative electrode binder SBR-CMC composite binder, and water are mixed, and the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is controlled to be 94:3:3 to obtain a negative electrode slurry with a solid content of 50%; then a pH regulator is added to the negative electrode slurry to control the pH of the negative electrode slurry to be 7.5±0.2, and finally the negative electrode slurry is coated on at least one side of the copper foil and dried under vacuum conditions at 120°C for 12 hours to make the residual solvent content 0.05wt%, thereby obtaining a negative electrode sheet.

[0142] 3. Preparation of positive electrode The positive electrode active material, a lithium-rich manganese-based material, the positive electrode conductive agent, carbon black, and the positive electrode binder, PVDF, were mixed uniformly in a mass ratio of 90:5:5. The mixture was thoroughly stirred in an N-methylpyrrolidone solvent to form a slurry with a solid content of 50%. This was then stirred uniformly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on at least one side of an aluminum foil and dried under vacuum at 120°C for 12 hours to reduce the residual solvent content to 0.05wt%, thereby obtaining a positive electrode sheet.

[0143] 4. Preparation of electrolyte EC and DMC were mixed in a volume ratio of 3:7 and stirred until uniformly mixed to obtain the solvent for the electrolyte. LiPF6 was added to the solvent, the temperature was controlled at 25±2°C, and the mixture was stirred until completely dissolved. 2 vol% of fluoroethylene carbonate (FEC) and 1 vol% of 1,3-propane sultone (PS) were added to the electrolyte in sequence and stirred for 30 minutes. Impurities were removed by filtering through a 0.22 μm filter membrane, and the water content was ≤20 ppm (detected by Karl Fischer method) to obtain the electrolyte.

[0144] 5. Production of lithium-ion batteries The positive and negative electrodes are stacked in sequence, and the stacked electrodes and separator are wound to form an electrode assembly. The electrode assembly is placed in a pre-molded aluminum-plastic film, dehydrated at 80°C, and injected with the prepared electrolyte. After vacuum packaging, static standing, formation, and shaping, the lithium-ion battery is obtained.

[0145] Test Example 1 The lithium phytate prepared in Example 1 was subjected to XRD test. The XRD diffraction pattern of lithium phytate is as follows: Figure 1 As shown, a broad diffraction peak appears at 2θ=23.5°, indicating that the lithium phytate has an amorphous structure.

[0146] The lithium phytate prepared in Example 1 was subjected to Fourier transform infrared spectroscopy test. The Fourier transform infrared spectrum of lithium phytate is as follows: Figure 2 As shown, it can be seen at wave number 780cm -1 ~890cm -1 、905cm -1 ~1100cm -1 、1101cm -1 ~1205cm -1 There is a characteristic absorption peak at 780cm -1 ~890cm -1 The absorption peak corresponds to the symmetrical stretching vibration of POM, 905cm -1 ~1100cm -1 The absorption peak corresponds to PO3 2- Asymmetric stretching vibration; 1101cm -1 ~1205cm-1 The absorption peak corresponds to HPO3 - Stretching vibration, indicating the successful preparation of lithium phytate.

[0147] The lithium phytate prepared in Example 1 was dissolved in water to prepare a 5% by weight lithium phytate solution. The pH of the lithium phytate solution was tested. The pH of the 5% lithium phytate solution was 9.12, indicating that the lithium phytate was weakly alkaline.

[0148] The lithium phytate prepared in Example 1 was subjected to a particle size test, and the particle size D50 of the lithium phytate was 3.2 μm.

[0149] The lithium phytate prepared in Example 1 was subjected to BET test, and the specific surface area of ​​lithium phytate was 1.83 m 2 / g.

[0150] The lithium phytate prepared in Example 1 was subjected to SEM testing. The SEM image of lithium phytate is as follows: Figure 3 As shown, lithium phytate has a morphology that is a mixture of spherical and surface wrinkled spherical shapes.

[0151] Test Example 2 The diaphragms prepared in Example 30 and Comparative Example 48 were tested for diaphragm coating thickness, diaphragm coating area density, thermal shrinkage properties, and wettability.

[0152] Test method and process for diaphragm coating thickness: Instrument: A lithium battery separator coating thickness gauge (KURABO RX410) was used to measure both substrate and coating thickness simultaneously.

[0153] Process: ① Lay the diaphragm sample flat on the measurement platform; ② Scan the coating surface using non-contact optical or ultrasonic technology; ③ Record thickness data at multiple points and calculate the average value.

[0154] Test method and process for membrane coating surface density: Instruments: high-precision electronic balance (accuracy 0.1 mg) and cutting tools.

[0155] Process: ① Cut the membrane sample into standard size (such as 10cm×10cm); ② Use a balance to weigh the sample mass; ③ Calculate the surface density (g / m²).

[0156] Thermal shrinkage performance test method and process: Instruments: Oven or oil bath equipment, thermal shrinkage test fixture.

[0157] Process: ① Mark the initial size (e.g., 10 cm x 10 cm) on the diaphragm; ② Heat the sample in an oven or oil bath at a set temperature (e.g., 120°C); ③ After cooling, measure the shrunken size and calculate the shrinkage rate (%).

[0158] Wettability test method and process: Instrument: Contact angle meter (optical method) or wetting balance (weighing method).

[0159] Process: ① Fix the membrane sample on a horizontal platform; ② Add a standard liquid (such as deionized water) to the surface; ③ Use an optical system to capture the shape of the droplet and calculate the contact angle; ④ The imbibition method (measuring liquid penetration time) can also be used.

[0160] The thickness of the diaphragm coating of Example 30 is 3.3 μm, and the surface density of the diaphragm coating is 5.61 g / m 2 The thermal shrinkage of the diaphragm at 120°C is 0.75%, and the wettability is 33 mm. The thickness of the diaphragm coating of the diaphragm of Comparative Example 48 is 2.9 μm, and the surface density of the diaphragm coating is 5.13 g / m 2 The thermal shrinkage of the separator at 120°C is 0.8%, and the wettability is 31mm. This shows that the thermal shrinkage performance and wettability of the separator are not deteriorated by the addition of lithium phytate.

[0161] Test Example 3 The batteries prepared in Examples 1 to 56 and Comparative Examples 1 to 48 were tested for the following properties: 1. Rate performance test: The test was conducted at (25±2)℃. The lithium-ion battery was charged to 4.53V at 0.8C, with a cutoff current of 0.05C, and allowed to stand for 10 minutes. It was then discharged to 3.0V at 0.2C / 0.5C / 1.0C / 1.5C / 2.0C / 3.0C, respectively, and allowed to stand for 10 minutes. The corresponding capacities were recorded, and the ratio of the discharge capacity at 3.0C to the discharge capacity at 0.2C was calculated. The results are recorded in Tables 5 to 9.

[0162] 2. Cycle performance test In a constant temperature chamber at (25±2)°C, the lithium-ion battery was charged at a constant current and constant voltage of 1C to 4.45V, then charged at a constant voltage to 4.53V. After standing for 5 minutes, it was discharged at 1C to 3.0V. The capacity obtained in this step was used as the initial capacity. A cycle test was performed using a 1C charge / 1C discharge cycle, and the capacity retention rate of the battery after 200 cycles was calculated. The calculation formula is as follows: 200th cycle capacity retention rate (%) = (200th cycle discharge capacity) / (first cycle discharge capacity) × 100%. The results are recorded in Tables 5-9.

[0163] 3. 85℃ storage test The battery was charged to 4.45V at 1C current at room temperature. The fully charged battery was placed in an environment of 85℃ for 6 hours. The thermal measurement thickness expansion rate (%) = (cycle thickness after storage - thickness before storage) / (thickness before cycle) × 100%. The results are recorded in Tables 5 to 9.

[0164] 4. Cobalt dissolution After cycling, disassemble the battery in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm) and remove the positive electrode, separator, and electrolyte. Record the battery cycling conditions (e.g., number of cycles, cutoff voltage, and temperature).

[0165] The membrane was immersed in 2 mL of anhydrous DMC and sonicated for 10 minutes to elute the adsorbed electrolyte. The eluate was then combined with the original electrolyte and centrifuged (10,000 rpm for 10 minutes) to remove particulate impurities. The electrolyte sample was filtered through a 0.22 μm filter membrane to obtain the electrolyte sample to be tested.

[0166] The dissolution of Co was tested by inductively coupled plasma optical emission spectrometry (ICP-OES) using a Co standard solution (1000 ppm) diluted to a series of concentrations of 0.1, 0.5, 1.0, 5.0, and 10.0 ppm. The electrolyte sample was diluted 10 to 100 times to obtain the sample to be tested. The standard curve was tested and the Co concentration was calculated by the standard curve fitting equation. The results are recorded in Tables 5 to 9. The standard curve fitting equation is [C Co =C 测 ×V 稀释 / m 电解液 ×10 6 (ppm)】 5. Thermal runaway trigger temperature test The thermal runaway triggering temperature of the battery was tested using an adiabatic accelerating rate calorimeter (ARC).

[0167] A fully charged battery (SOC ≥ 90%) was left unattended for 24 hours with a voltage fluctuation of ≤ ±0.01V. K-type thermocouples were attached to the center and sides of the battery surface and connected to the ARC data acquisition system. The first step was preheating: the temperature was raised to 80°C at a rate of 5°C / min and held at that temperature for 10 minutes. The second step was adiabatic tracking: the ARC adiabatic mode was activated, and the temperature rise rate was monitored in real time. The third step was trigger determination: the trigger temperature was recorded when dT / dt ≥ 0.08°C / s. The results are recorded in Tables 5-9.

[0168] Test Example 4 The batteries prepared in Example 1 (LCO+1% lithium phytate) and Comparative Example 47 (LCO) were subjected to rate performance tests. The rate performance test figures of the batteries in Example 1 and Comparative Example 47 are shown in FIG. Figure 4 As shown, it is shown that adding lithium phytate to the positive electrode active material layer can significantly improve the rate performance of the battery.

[0169] The batteries prepared in Example 1 (LCO+1% lithium phytate) and Comparative Example 47 (LCO) were subjected to cycle performance tests. The cycle performance test figures of the batteries in Example 1 and Comparative Example 47 are shown in FIG. Figure 5 As shown, it shows that adding lithium phytate to the positive electrode active material layer can significantly improve the cycle performance of the battery.

[0170] The batteries prepared in Example 30 (PL05) and Comparative Example 48 (PL00) were subjected to cycle performance tests. The cycle performance test figures of the batteries in Example 30 and Comparative Example 48 are shown in FIG. Figure 6 As shown, it shows that adding lithium phytate to the separator coating can significantly improve the cycle performance of the battery.

[0171] Table 5

[0172] As shown in Table 5, based on the comparison between Examples 1 to 3 and Comparative Examples 1 and 2, when the mass ratio of phytic acid to lithium source is 1:(0.15-3), the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are higher.

[0173] According to the comparison between Examples 1, 4-5 and Comparative Examples 3 and 4, when the mass percentage of the phytic acid solution is 10%-30%, it helps to improve the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery.

[0174] According to the comparison between Examples 1, 6-7 and Comparative Examples 5 and 6, when the mass percentage of the lithium source solution is 5%-20%, the rate performance, cycle performance and safety performance of the battery are better, and the cobalt dissolution amount is lower.

[0175] According to the comparison between Examples 1, 8 to 9 and Comparative Examples 7 and 8, it can be seen that when the mixing temperature of the mixing treatment is 25°C to 120°C and the mixing time is 1h to 24h, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery can be improved.

[0176] According to the comparison between Examples 1, 10-11 and Comparative Examples 9 and 10, when the temperature of the air inlet of the spray dryer is 215°C-225°C, the temperature of the air outlet is 60°C-160°C, the hot air temperature is 175°C-185°C, and the drying time is 3s-5s, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are further improved.

[0177] According to the comparison between Examples 1, 12-13 and Comparative Examples 11 and 12, when the particle size D50 of lithium phytate is 1 μm-5 μm, it is beneficial to optimize the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery.

[0178] According to the comparison between Examples 1, 14-15 and Comparative Examples 13 and 14, when the specific surface area of ​​lithium phytate is 1 m 2 / g~5m 2 / g, the battery's rate performance, cycle performance, cobalt dissolution and safety performance can be improved.

[0179] Table 6

[0180] As can be seen from Table 6, according to the comparison of Examples 1, 16-17 and Comparative Examples 15 and 16, when the mass proportion of lithium phytate is 0.5%-2% of the positive electrode active material, it helps to improve the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery.

[0181] According to the comparison between Examples 1, 18 to 21 and Comparative Examples 17 and 18, when the positive electrode active material layer satisfies the relationship of Formula 1, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are higher.

[0182] According to the comparison between Examples 1, 22-23 and Comparative Examples 19 and 20, it can be seen that when the mass ratio of the positive electrode binder to the solvent is 0.6-1.4, the rate performance, cycle performance and safety performance of the battery are better, and the cobalt dissolution amount is lower.

[0183] According to the comparison between Examples 1, 24-25 and Comparative Examples 21 and 22, when the stirring temperature is 20°C-60°C and the stirring speed is 10rpm-600rpm, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are improved.

[0184] According to the comparison between Examples 1, 26-27 and Comparative Examples 23 and 24, it can be seen that when the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (80-98): (1-10): (1-10), it is beneficial to the optimization of the battery's rate performance, cycle performance, cobalt dissolution amount, and safety performance.

[0185] According to the comparison between Examples 1, 28-29 and Comparative Examples 25 and 26, when the viscosity of the positive electrode slurry is 3500mPa.s-6000mPa.s, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery can be improved.

[0186] Table 7

[0187] It can be seen from Table 7 that, according to the comparison of Examples 30 to 32 and Comparative Examples 27 and 28, when the mass percentage of lithium phytate in the diaphragm coating is 1% to 20%, and the mass ratio of alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder is (50 to 70): (1 to 20): (10 to 25): (5 to 15), it helps to improve the rate performance, cycle performance, cobalt dissolution amount, and safety performance of the battery.

[0188] According to the comparison between Examples 30, 33 to 35 and Comparative Examples 29 and 30, it can be seen that when the thickness of the diaphragm coating is 0.1 μm to 5 μm, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are better.

[0189] According to the comparison between Examples 30, 36-37 and Comparative Examples 31 and 32, when the coating gap is 10 μm-20 μm, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are improved.

[0190] According to the comparison of Examples 30, 38-39 and Comparative Examples 33 and 34, it can be seen that when the solid content of the diaphragm coating slurry is 15%-25%, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery can be improved.

[0191] According to the comparison of Examples 30, 40~41 and Comparative Examples 35 and 36, it can be seen that when the battery is dried at 80℃~100℃ for 1min~3min and then heated to 120℃~150℃ for drying for 2min~5min, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery can be improved.

[0192] Table 8

[0193] As can be seen from Table 8, according to the comparison of Examples 42 to 44 and Comparative Examples 37 and 38, when the mass proportion of lithium phytate is 0.5% to 2% of the negative electrode binder, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery can be improved.

[0194] According to the comparison between Examples 42, 45-46 and Comparative Examples 39 and 40, it can be seen that when the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (90-96): (1-5): (2-5), it is beneficial to optimize the rate performance, cycle performance, cobalt dissolution amount, and safety performance of the battery.

[0195] According to the comparison between Examples 42, 47~48 and Comparative Examples 41 and 42, it can be seen that when the dispersion treatment is stirring at a rotation speed of 300rpm~800rpm for 60min~120min and ultrasonic dispersion at a power of 20W~50W for 30min~60min, the battery has better rate performance, cycle performance and safety performance, and the cobalt dissolution amount is lower.

[0196] According to the comparison of Examples 42, 49-50 and Comparative Examples 43 and 44, it can be seen that when the solid content of the negative electrode slurry is 40%-55%, it helps to improve the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery.

[0197] According to the comparison between Examples 42, 51-52 and Comparative Examples 45 and 46, when the pH of the negative electrode slurry is 7-9, the rate performance, cycle performance, cobalt dissolution amount and safety performance of the battery are improved.

[0198] Table 9

[0199] As can be seen from Table 9, according to the comparison of Examples 1, 30, 42, Examples 53 to 55, and Example 56, adding lithium phytate to two or three of the positive electrode active material layer, the negative electrode active material layer, and the separator coating can further improve the rate performance, cycle performance, and storage performance of the battery.

[0200] According to the comparison of Examples 1, 30, 32 and Comparative Example 47, adding lithium phytate to the positive electrode active material layer, the negative electrode active material layer and the separator coating can improve the rate performance, cycle performance and storage performance of the battery.

[0201] According to the comparison between Example 30 and Comparative Example 48, adding lithium phytate to the diaphragm coating helps to improve the rate performance, cycle performance and storage performance of the battery.

[0202] The embodiments of the present application have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. A battery, characterized in that: The device comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the positive electrode sheet comprises a positive electrode active material layer, the negative electrode sheet comprises a negative electrode active material layer, and the separator is located between the positive electrode sheet and the negative electrode sheet and comprises a base film and a separator coating provided on at least one side of the base film. Wherein, at least one of the positive electrode active material layer, the negative electrode active material layer and the separator coating layer comprises lithium phytate.

2. The battery according to claim 1, wherein: The particle size D50 of the lithium phytate is 1 μm to 5 μm; and / or, The specific surface area of ​​the lithium phytate is 1m 2 / g~5m 2 / g; and / or, In the XRD diffraction pattern of the lithium phytate, a diffraction peak exists at a diffraction angle of 2θ=(23±0.5)°, and the half-peak width of the diffraction peak is ≥1.0°; and / or, In the infrared absorption spectrum of lithium phytate, at wave number 780 cm -1 ~890cm -1 、905cm -1 ~1100cm -1 、1101cm -1 ~1205cm -1 There is an absorption peak at .

3. The battery according to claim 2, characterized in that The preparation method of lithium phytate comprises the following steps: The phytic acid solution and the lithium source solution are mixed to obtain a salt solution, and the salt solution is spray-dried to obtain the powdered lithium phytate; Wherein, the mass ratio of phytic acid to lithium source is 1:(0.15~3); and / or, the mass percentage of the phytic acid solution is 10%~30%, and the mass percentage of the lithium source solution is 5%~20%; and / or, the mixing temperature of the mixing treatment is 25°C~120°C, and the mixing time is 1h~24h; and / or, the spray drying treatment is carried out in the spray dryer, the air inlet temperature of the spray dryer is 215°C~225°C, the air outlet temperature is 60°C~160°C, the hot air temperature is 175°C~185°C, and the drying time is 3s~5s.

4. The battery according to claim 2, characterized in that Before the lithium phytate is used in the battery, the water content in the lithium phytate is ≤200 ppm.

5. The battery according to claim 4, characterized in that The positive electrode active material layer includes a positive electrode active material and the lithium phytate; The mass proportion of the lithium phytate is 0.5% to 2% of the positive electrode active material; and / or, The positive electrode active material layer satisfies the following relationship: m 植酸锂 / m 正极活性材料 =k×S 正极活性材料 / S 植酸锂 Formula 1 In the above relational formula 1, m 植酸锂 is the amount of lithium phytate added to the positive electrode active material layer; m 正极活性材料 is the amount of the positive electrode active material added to the positive electrode active material layer; k is 0.005 to 0.2; S 正极活性材料 is the specific surface area of ​​the positive electrode active material; S 植酸锂 is the specific surface area of ​​the lithium phytate.

6. The battery according to claim 5, characterized in that The method for preparing the positive electrode sheet comprises the following steps: S1, performing a first mixing process on the positive electrode binder and the solvent to obtain a positive electrode binder mixed solution; Wherein, the mass ratio of the positive electrode binder to the solvent is 0.6-1.4; and / or, the first mixing process is performed by stirring, the stirring temperature is 20° C.-60° C., and the stirring speed is 10 rpm-600 rpm; S2, adding the positive electrode active material, the positive electrode conductive agent and the lithium phytate to the positive electrode binder mixed solution for a second mixing process to obtain a positive electrode slurry; The mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (80-98): (1-10): (1-10); and / or the viscosity of the positive electrode slurry is 3500 mPa.s-6000 mPa.s; and / or the compatibility index of the lithium phytate in the positive electrode slurry and the solvent is ≤0.1; S3, applying the positive electrode slurry to at least one side of the positive electrode current collector, and performing a first drying process to obtain a positive electrode sheet; The first drying treatment is performed under vacuum conditions at 115° C. to 125° C. for 10 to 12 hours; and / or the mass percentage of the solvent in the positive electrode active material layer after the first drying treatment is not higher than 0.1%.

7. The battery according to claim 4, characterized in that The diaphragm coating comprises the lithium phytate, the mass percentage of the lithium phytate in the diaphragm coating is 1% to 20%, and the thickness of the diaphragm coating is 0.1 μm to 5 μm.

8. The battery according to claim 7, characterized in that The preparation method of the diaphragm comprises the following steps: S1, dispersing the alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder in water, and mixing them evenly to obtain a diaphragm coating slurry; The mass ratio of the alumina ceramic, lithium phytate, diaphragm conductive agent, and diaphragm binder is (50-70): (1-20): (10-25): (5-15); and / or the solid content of the diaphragm coating slurry is 15%-25%; S2, applying the membrane coating slurry to at least one side of the base film, and drying the base film to obtain the membrane; The diaphragm coating slurry is applied by coating, with a coating gap of 10 μm to 20 μm; and / or the drying treatment is a gradient drying treatment, drying at 80°C to 100°C for 1 min to 3 min, then heating to 120°C to 150°C and drying for 2 min to 5 min.

9. The battery according to claim 4, characterized in that The negative electrode active material layer includes a negative electrode binder and the lithium phytate, and the mass proportion of the lithium phytate to the negative electrode binder is 0.5% to 2%.

10. The battery according to claim 9, characterized in that The method for preparing the negative electrode sheet comprises the following steps: S1, dispersing the negative electrode active material, negative electrode conductive agent, and negative electrode binder in water, and mixing them uniformly to obtain a negative electrode mixture; Wherein, the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is (90-96): (1-5): (2-5); S2. Adding lithium phytate solution to the negative electrode mixture and performing dispersion treatment to obtain a negative electrode slurry; The dispersion treatment comprises stirring at a rotation speed of 300 rpm to 800 rpm for 60 min to 120 min and ultrasonic dispersion at a power of 20 W to 50 W for 30 min to 60 min; and / or the pH of the negative electrode slurry is 7 to 9; and / or the solid content of the negative electrode slurry is 40% to 55%; S3, applying the negative electrode slurry to at least one side of the negative electrode current collector, and performing a second drying process to obtain a negative electrode sheet; Wherein, the second drying treatment is drying under vacuum conditions for 10 hours to 12 hours; and / or, the mass percentage of the water in the negative electrode active material layer after the second drying treatment is not higher than 0.1%.

11. The battery according to claim 1, characterized in that The positive electrode active material layer includes positive electrode active materials, and the positive electrode active materials include LiCoO2 and its modified derivative materials, lithium-rich manganese-based materials Li 1.2 Ni 0.2 Mn 0.6 O2 and its modified derivative materials, spinel LiNi 0.5 Mn 1.5 At least one of O4 and its modified derivative materials.

12. The battery according to claim 1, characterized in that The charging cut-off voltage of the battery is not less than 4.45V; and / or, The thickness expansion rate of the battery when stored at 85° C. for 6 hours is not higher than 10%; and / or, The thermal runaway trigger temperature of the battery under 1C full charge state is ≥180°C.

13. The battery according to claim 1, characterized in that When the positive electrode active material layer includes the lithium phytate, after the battery is charged and discharged for 200 cycles at 1C / 1C, the amount of transition metal ions dissolved in the positive electrode active material is no more than 800 ppm.

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