Battery

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a battery. Compared with the prior art, by controlling the content of the iron element in the positive plate, the content of the carbon-lithium composite material in the negative plate and the ratio of the discharge capacities of the battery at high temperature and normal temperature, gas production in the battery is avoided while the energy density of the battery is improved, so that the cycle performance of the battery is improved.

Description

Technical Field

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

[0002] Lithium replenishment technology is an important means to improve the energy density of lithium-ion batteries. During the first charge of a lithium-ion battery, the organic electrolyte will be reduced and decomposed on the surface of the negative electrode such as graphite, forming a solid electrolyte interphase (SEI) film. This permanently consumes a large amount of lithium from the positive electrode, resulting in a low coulombic efficiency (ICE) in the first cycle, which reduces the capacity and energy density of the lithium-ion battery.

[0003] However, current cathode lithium supplements generally suffer from problems such as high residual alkali on the surface, strong interfacial side reactions, and poor electronic conductivity. These problems lead to the generation of large amounts of gas and increased internal resistance when these cathode lithium supplements are added to lithium-ion batteries, thereby reducing the battery's kinetic performance and limiting its large-scale application. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a battery with low gas production and high energy density.

[0005] This invention provides a battery, comprising a positive electrode and a negative electrode;

[0006] The positive electrode sheet includes a positive electrode active layer; the positive electrode active layer includes a positive electrode material; the positive electrode material includes lithium iron phosphate materials; the mass ratio of Fe element to the positive electrode active layer is b;

[0007] The negative electrode sheet includes a negative electrode active layer; the negative electrode active layer includes a negative electrode material; the negative electrode material includes a carbon material; in the 100% SOC state of the battery, the negative electrode active layer also includes a carbon-lithium composite; the ratio a of the mass of the carbon-lithium composite to the mass of the negative electrode active layer is;

[0008] The ratio of the specific capacity of the battery at 0.33C discharge under high temperature (45℃) to that at 0.33C discharge under normal temperature (25℃) is c; the battery satisfies the relationship: (a / b)×c=2~5.

[0009] Compared with existing technologies, this invention improves the battery's cycle performance by controlling the iron content in the positive electrode, the carbon-lithium composite material content in the negative electrode, and the ratio of the battery's discharge capacity at high and normal temperatures, thereby increasing the battery's energy density while avoiding gas generation inside the battery. Detailed Implementation

[0010] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0011] Lithium replenishment, also known as "pre-lithiation" or "pre-intercalation," involves adding lithium to the battery before it begins operation to replenish lithium ions. Pre-lithiation replenishes the electrode material, offsetting irreversible lithium loss and improving the battery's overall capacity and energy density. Compared to negative electrode lithium replenishment, positive electrode lithium replenishment materials can be added directly during the homogenization process of the positive electrode slurry, requiring no additional process modifications, resulting in lower costs, a simpler process, and safer operation. This makes it more suitable for current lithium-ion battery manufacturing processes and has gained favor in the industry in recent years.

[0012] This invention provides a battery, comprising a positive electrode and a negative electrode; the positive electrode includes a positive active layer; the positive active layer includes a positive electrode material; the positive electrode material includes a lithium iron phosphate material; the mass ratio of Fe element to the positive active layer is b; the negative electrode includes a negative active layer; the negative active layer includes a negative electrode material; the negative electrode material includes a carbon material; in the 100% SOC state of the battery, the negative active layer further includes a lithium carbon-carbon composite; the mass ratio of the lithium carbon-carbon composite to the mass of the negative active layer is a; the ratio of the specific capacity of the battery at 0.33C discharge under high temperature (45℃) to the specific capacity at 0.33C discharge under normal temperature (25℃) is c; the battery satisfies the relationship: (a / b) × c = 2~5.

[0013] Further control of the formula (a / b)×c within the range of 2.5~3.5, on the one hand, takes into account the lithium replenishment effect and improves the energy density of the battery; on the other hand, it avoids excessive gas production inside the battery, which would cause the battery cycle performance to deteriorate. If the formula value is too large, gas production will increase and the cycle performance will be worse; if the formula value is too small, the lithium replenishment effect will be poor and the battery energy density will be low.

[0014] Under high-temperature conditions, the lithium replenishing agent can react more preferentially, making up for the consumption of lithium ions during the formation and film formation process, reducing side reactions in the electrolyte and positive and negative electrodes, and allowing the lithium in the positive electrode material to fully utilize its capacity. An increase in the ratio of high temperature to room temperature means that the lithium replenishing agent's role in compensating for the consumption of active lithium is more significant, resulting in a better lithium replenishment effect. Therefore, the ratio can be used to represent the lithium replenishment effect. In this invention, the ratio c of the battery's 0.33C discharge specific capacity at 45°C to its 0.33C discharge specific capacity at 25°C is preferably 1.05~1.5. Optionally, c can be 1.05, 1.1, 1.12, 1.15, 1.18, 1.2, 1.22, 1.25, 1.28, 1.3, 1.32, 1.35, 1.38, 1.4, 1.42, 1.45, 1.48, 1.5, or any two of the above values. In some embodiments provided by the present invention, c can specifically be 1.33, 1.39, 1.35, 1.26, 1.21, 1.49, 1.45, 1.24, 1.05, 1.24, 1.47, 1.32, 1.37, 1.34, 1.46, 1.4, 1.35 or 1.31.

[0015] In a specific embodiment provided by the present invention, c is further preferably 1.2 to 1.4; within this range, the energy density of the battery can be further improved.

[0016] In this invention, the value of c can be specifically adjusted by comprehensively considering factors such as the particle size of lithium iron phosphate; the type and content of solvents and additives in the electrolyte; the type of lithium replenishing agent; and the thickness of the second carbon coating layer on the surface of the lithium replenishing agent.

[0017] The mass ratio of Fe to the positive electrode active layer is b, and the ratio of the mass of the carbon-lithium complex to the mass of the negative electrode active layer is a, when the battery is at 100% SOC. By limiting a / b, the lithium replenishment content can be indirectly reflected. During battery charging, lithium ions are released from the positive electrode and reach the negative electrode. The lithium ions released from the positive electrode are inserted into the negative electrode material and combine with the carbon in the negative electrode to form a carbon-lithium complex. The Fe element comes from lithium iron phosphate. The ratio of the carbon-lithium complex formed in the negative electrode to the Fe element in the positive electrode sheet indirectly reflects the lithium abundance and the content of the lithium replenishment agent. As the ratio increases, it means that more lithium ions are released from the positive electrode. However, if the lithium replenishment agent content is too high, the gas production will increase. At the same time, the Fe element content cannot be too low. In addition, low Fe element content can also easily reduce the electronic conductivity of the positive electrode active material layer, affecting the diffusion ability of lithium ions and affecting the battery energy density. Therefore, in this invention, the value of a / b is preferably 1.4 to 4; optionally, the value of a / b is 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, or a range between any two of the above values.

[0018] In one specific embodiment of the present invention, the a / b ratio is preferably in the range of 1.8 to 3. Within this range, the battery can have lower gas production and higher energy density.

[0019] In this invention, the value of a / b can be comprehensively adjusted by factors such as the molar ratio of Li to Fe in the lithium iron phosphate material, the particle size Dn10 of the lithium iron phosphate material, the type of lithium replenishing agent, the preparation method of the lithium replenishing agent and the lithium iron phosphate material, the thickness of the second carbon coating layer on the surface of the lithium replenishing agent, and the catalyst content.

[0020] In this invention, the Fe content cannot be too low. Low Fe content can easily reduce the electronic conductivity of the positive electrode active material layer, affecting the diffusion ability of lithium ions and thus the battery energy density. However, excessive Fe content can affect the material structure, leading to lattice defects and structural distortions, irregular particle morphology, indirectly reducing compaction density, and also increasing the impurity phase and specific surface area, thus affecting the battery energy density. Therefore, in this invention, the preferred range of the mass ratio b of Fe to the positive electrode active layer is 0.25 to 0.35; optionally, b can be 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, or any two of the above values.

[0021] In one specific embodiment of the present invention, the range of b is preferably 0.3 to 0.33; within this range, the energy density of the battery can be further improved.

[0022] The mass ratio of the lithium carbon compound in the negative electrode reflects the amount of lithium ions extracted from the positive electrode and the effect of the lithium replenishment agent. In this invention, the ratio 'a' of the mass of the lithium carbon compound to the mass of the negative electrode active layer is preferably 0.5 to 0.94 when the battery is at 100% SOC. Optionally, 'a' can be 0.5, 0.52, 0.54, 0.55, 0.56, 0.58, 0.6, 0.62, 0.64, 0.65, 0.66, 0.68, 0.7, 0.72, 0.74, 0.73, 0.75, 0.76, 0.78, 0.8, 0.82, 0.84, 0.85, 0.86, 0.88, 0.9, 0.92, 0.94, or any two of the above values.

[0023] In one specific embodiment of the present invention, the range of 'a' is preferably 0.6 to 0.8. Within this range, the gas production of the battery can be further reduced and the energy density of the battery can be increased.

[0024] In a specific embodiment of the present invention, the range of 'a' is preferably 0.72 to 0.8. Within this range, the gas production of the battery can be further reduced and the energy density of the battery can be increased.

[0025] In one specific embodiment of the present invention, the carbon-lithium composite includes LiC6, which is the most thermodynamically stable and has a longer cycle life compared to other carbon-lithium compounds; it also has a high and stable energy density and controllable energy output.

[0026] In this invention, the lithium replenishment effect can be improved by synergistic regulation of a / b and c, thereby increasing the energy density of the battery. At the same time, it avoids excessive lithium replenishment content, which would increase the amount of gas generated inside the battery.

[0027] In one specific embodiment of the present invention, the lithium iron phosphate material includes a first particle and a second particle; the first particle has a particle size greater than or equal to 1 μm; and the second particle has a particle size less than 1 μm. By combining the first and second particles, the smaller second particle fills the gaps between the first and second particles, increasing the compaction density. At the same time, the larger first particle avoids excessive side reactions caused by using only the second particle, thereby increasing the energy density of the battery. This can further reduce the demand for lithium replenishment agent and reduce the gas generation problem caused by excessive introduction of lithium replenishment agent. Therefore, under these conditions, the a / b range is preferably 1.4 to 3.5.

[0028] Furthermore, in a specific embodiment provided by the present invention, the particle size corresponding to a cumulative distribution of the second particles reaching 10% is Dn10, and the preferred range of Dn10 is 0.1~0.5 μm. By further controlling the particle size of the second particles, the gas production of the battery can be improved. Optionally, the particle size Dn10 of the second particles is 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.3 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, etc. The particle size (Dn) can be 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, 0.4 μm, 0.41 μm, 0.42 μm, 0.43 μm, 0.44 μm, 0.45 μm, 0.46 μm, 0.47 μm, 0.48 μm, 0.49 μm, 0.5 μm, or any two of the above values. By controlling the range of Dn, on the one hand, smaller particles shorten the lithium-ion transport path, improving the energy density of the battery; on the other hand, excessively small particles can lead to increased side reactions and increased gas production inside the battery.

[0029] Regarding the testing method for the second particle Dn10, this application does not limit it. Specifically, the test can be conducted as follows: If the positive electrode is in a secondary battery, the secondary battery in an empty state (the battery is discharged at 0.33C to the lower limit voltage of 2.5V) is disassembled. The obtained positive electrode is soaked in dimethyl carbonate at 25℃ for 2 hours, dried, and then the material layer powder on the positive electrode is scraped off. The scraped powder is used as a sample. The sample is fixed with conductive adhesive and CP argon ion polished, a conductive film is deposited, placed on the sample stage and observed under a scanning electron microscope (SEM). The size is adjusted to 10kx. Then, the first and second particles are determined by the particle size. The particle size (i.e., diameter) of the first lithium iron phosphate particle is greater than or equal to 1μm, and the particle size (diameter) of the second particle is <1μm. The diameter of the second particle in the measurement area is measured using Nano Measure software. The diameter of 100 second particles is measured, and the particle size Dn10 corresponding to the number of 10% of the 100 second particles is counted.

[0030] In this invention, the cathode material includes lithium iron phosphate (LFP) materials; the LFP materials include lithium iron phosphate and / or doped and modified lithium iron phosphate; by modifying with transition metal doping, some lithium, iron, or phosphorus atoms in the LFP lattice are replaced, changing the lattice parameters, optimizing the lithium-ion diffusion channels, improving the material's conductivity and lithium-ion diffusion coefficient, thereby improving the material's specific capacity and cycle performance; the doping element in the doped and modified lithium iron phosphate preferably includes Ti and / or V; the doping amount of Ti can specifically be 600~3000 ppm; optionally, the doping amount of Ti is 600 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 2600 ppm, 3000 ppm or any two of the above values; the doping amount of V can specifically be 500~2000 ppm; optionally, the doping amount of V is 500 ppm, 800 ppm, 1000 ppm, 1400 ppm, 1600 ppm. ppm, 1800 ppm, 2000 ppm, or any two of the above values.

[0031] In a specific embodiment of the present invention, the doping amount of Ti is preferably 2600~2750 ppm; within this range, the specific capacity and cycle performance of the material can be further improved; optionally, the doping amount of Ti is 2600 ppm, 2620 ppm, 2650 ppm, 2680 ppm, 2700 ppm, 2720 ppm, 2750 ppm or any two of the above values.

[0032] In a specific embodiment of the present invention, the doping amount of V is preferably 1600~1750 ppm; within this range, the specific capacity and cycle performance of the material can be further improved; optionally, the doping amount of V is 1600 ppm, 1620 ppm, 1650 ppm, 1680 ppm, 1700 ppm, 1720 ppm, 1750 ppm or any two of the above values.

[0033] Regarding the testing method for elemental content, this application does not limit the specific method. The test can be conducted as follows: If the positive electrode is in a secondary battery, disassemble the secondary battery in an empty state (the battery is discharged at 0.33C to the lower limit voltage of 2.5V). Soak the obtained positive electrode in dimethyl carbonate at 25℃ for 2 hours, dry it, scrape off the positive electrode active layer powder, accurately weigh 0.5 g of the positive electrode active layer powder, disperse it in 20 ml of water, add 2 mL of concentrated nitric acid (analytical grade) and 5 mL of 40% boric acid solution, mix well and heat it. After the powder dissolves, dilute the material with water to 100 mL to obtain the test solution. Perform ICP testing on the test solution. Before the test, a standard solution must be prepared. The linear correlation coefficient of the standard concentration must be above 0.999 to be used as a normal standard. Dilute the 1000 mg / L standard solution with deionized water to different concentrations (generally 0, 1 mg / 100mL, 2 mg / 100mL, 3 mg / 100mL), and select the element detection wavelength. Set the experimental conditions: based on the characteristics of the sample and the element to be detected, set appropriate ICP instrument operating conditions: gas flow rate 0.5 L / min, power 1150 W, and select the element detection wavelength, which depends on the element being tested (e.g., V wavelength 309.311 nm, Ti wavelength 323.452 nm). The element content in the sample can be read by the self-analysis function of the ICP testing software. The standard solution can be any solution containing the element to be tested that is well known to those skilled in the art. Specifically, it can be prepared as follows: 1) Take five 100 mL volumetric flasks and add 0 mL, 2 mL, 5 mL, 10 mL, and 15 mL of stock solution containing Ti or V, respectively; 2) Add 2 mL of concentrated nitric acid (analytical grade) and 5 mL of... 40% boric acid solution, dilute to the mark with ultrapure water and shake well; 3) let stand for 10 min (to allow the boric acid to fully complex).

[0034] In one specific embodiment of the present invention, the lithium iron phosphate material preferably further includes a first carbon coating layer. Coating with the first carbon coating layer can help improve the overall conductivity of the positive electrode and facilitate the function of the lithium replenishing agent. However, an excessively thick coating layer can also lead to increased side reactions with the electrolyte, resulting in increased gas production. Therefore, in one specific embodiment of the present invention, the thickness of the first carbon coating layer is 1~10 nm. Optionally, the thickness of the first carbon coating layer is 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any two of the above values.

[0035] In a specific embodiment provided by the present invention, the positive electrode active layer preferably further includes a lithium supplementing agent and / or reaction residues of the lithium supplementing agent; the lithium supplementing agent includes at least one of an iron-containing lithium supplementing agent, a nickel-containing lithium supplementing agent, and lithium oxalate (LCO).

[0036] In a specific embodiment provided by the present invention, the iron-containing lithium supplementing agent is lithium-rich lithium ferrate, and its structural formula is Li5(Fe x1 M1 y1 )O4, where x1 + y1 = 1, 0 < x1 ≤ 1, 0 < y1 ≤ 11, and M1 is selected from one or more of Mn, Al, Mg, Ti, and Co; after the lithium supplementing reaction, its reaction residue is LiFeO2.

[0037] In a specific embodiment provided by the present invention, the nickel-containing lithium supplementing agent is lithium-rich lithium nickelate, and the structural formula of the lithium-rich lithium nickelate is Li2(Ni x2 M2 y2 )O2, where x2 + y2 = 1, 0 < x2 ≤ 1, 0 < y2 ≤ 11, and M2 is selected from one or more of Mn, Al, Mg, Ti, and Co; after its lithium supplementing reaction, the reaction residue is lithium-deficient nickel oxide (such as LiNiO2).

[0038] In a specific embodiment provided by the present invention, the lithium supplementing agent can also be lithium oxalate, and after it plays the role of lithium supplementation, gases such as CO2 can be generated.

[0039] In a specific embodiment provided by the present invention, the mass of the lithium supplementing agent is preferably 0.5% - 5% of the mass of the lithium iron phosphate-based material; optionally, the mass of the lithium supplementing agent 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%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5% or the range between any two of the above values.

[0040] In one specific embodiment of the present invention, the surface of the lithium replenishing agent and / or the reaction residue of the lithium replenishing agent is further provided with a second carbon coating layer; the thickness of the second carbon coating layer is preferably 1~15 nm; optionally, the thickness of the carbon coating layer is 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm or any two of the above values.

[0041] In a specific embodiment of the present invention, the reaction residue of the lithium replenishing agent includes LiFeO2; a second carbon coating layer is provided on the surface of the LiFeO2; the thickness of the carbon coating layer on the surface of the LiFeO2 is preferably 3~15 nm; optionally, the thickness of the second carbon coating layer on the surface of the LiFeO2 is 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm or any two of the above values.

[0042] In a specific embodiment of the present invention, the positive electrode active layer further includes a catalyst; the catalyst is disposed on the outer surface of the lithium iron phosphate material and / or on the second carbon coating layer of the lithium replenishing agent and / or the reaction residue of the lithium replenishing agent. The catalyst is preferably an oxide of a first transition metal element, including, but not limited to, one or more of cobalt oxide, iron oxide, nickel oxide, manganese dioxide, copper oxide, titanium dioxide, and zinc oxide. Adding a catalyst provides active sites, reduces the activation energy of the lithium replenishing agent, promotes the decomposition of the lithium replenishing agent, promotes electron transfer, and lowers the delithiation plateau.

[0043] In one specific embodiment of the present invention, the mass of the catalyst may be 5% to 10% of the mass of the lithium supplement; optionally, the mass of the catalyst may be 5%, 6%, 7%, 8%, 9%, or 10% of the mass of the lithium supplement.

[0044] In a specific embodiment of the present invention, the second carbon coating layer on the surface of the lithium replenishing agent and / or the reaction residue of the lithium replenishing agent preferably further includes a conductive agent; the conductive agent can be any conductive agent known to those skilled in the art and there are no special limitations. In the present invention, carbon nanotubes, graphene, acetylene black, carbon nanofibers, etc. are preferred.

[0045] This invention does not impose any special restrictions on the preparation of the above-mentioned materials, as long as the above conditions are met; in a specific embodiment provided by this invention, the lithium iron phosphate material is preferably prepared according to the following method: a lithium source, an iron source, a phosphorus source precursor, and a precursor of doping element M (if element M is present, specifically an oxide of element M, etc.) are mixed evenly to obtain a mixture; the mixture is dispersed in a solvent and wet-milled, then spray-dried to obtain a powder; the powder is calcined once and then pulverized to obtain a first-calcined product; the first-calcined product is calcined a second time and pulverized to obtain the lithium iron phosphate material.

[0046] In a specific embodiment of the present invention, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium dihydrogen phosphate, lithium citrate, and lithium acetate; the phosphorus source includes at least one of ammonium dihydrogen phosphate, lithium dihydrogen phosphate, and ammonium phosphate; more preferably, the phosphorus source and the lithium source can be the same, such as lithium dihydrogen phosphate; the iron source includes at least one of ferrous oxalate, ferric hydroxide, ferrous hydroxide, ferric phosphate, ferrous phosphate, ferric acetate, ferrous acetate, ferric carbonate, ferrous carbonate, ferric oxide, magnetite, and ferric oxalate; the first carbon source includes at least one of glucose, sucrose, microcrystalline sugar, and organic polymer.

[0047] In a specific embodiment of the present invention, during the preparation of lithium iron phosphate materials, the mass of the first carbon source is preferably 2% to 8% of the total mass of the lithium source, iron source and phosphorus source precursors; optionally, the mass of the first carbon source is 2%, 3%, 4%, 5%, 6%, 7%, 8% of the total mass of the lithium source, iron source and phosphorus source precursors or any two of the above values.

[0048] In one specific embodiment of the present invention, the grinding speed is preferably 250~450 r / min; optionally, the grinding speed is 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or any two of the above values. The grinding time is preferably 1.5~2.5 h; optionally, the crushing time is 1.5 h, 2 h, 2.5 h or any two of the above values.

[0049] In a specific embodiment of the present invention, the pressure during spray drying is preferably 0.4~0.7 MPa; the pressure during spray drying is 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, or any two of the above values; the inlet temperature during spray drying is 200℃~290℃; optionally, the inlet temperature during spray drying is 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, or any two of the above values; the outlet temperature during spray drying is preferably 80℃~120℃; optionally, the outlet temperature during spray drying is 80℃, 90℃, 100℃, 110℃, 120℃, or any two of the above values.

[0050] In a specific embodiment of the present invention, the primary calcination temperature is preferably 600℃~800℃; optionally, the primary calcination temperature is 600℃, 650℃, 700℃, 750℃, 800℃ or any two of the above values; the primary calcination heating rate is preferably 4~6℃ / min; the primary calcination holding time is preferably 8~12 h; optionally, the primary calcination holding time is 8 h, 9 h, 10 h, 11 h, 12 h or any two of the above values.

[0051] In this invention, the secondary calcination temperature is preferably 760℃~790℃; optionally, the secondary calcination temperature is 760℃, 770℃, 780℃, 790℃ or any two of the above values; the heating rate of the secondary calcination is preferably 4~6℃ / min; the holding time of the secondary calcination is preferably 6~8 h; optionally, the secondary calcination time is 6 h, 7 h, 8 h or any two of the above values.

[0052] In this invention, the frequency of pulverization after secondary calcination is preferably 20~60 Hz; optionally, the pulverization power is 20 Hz, 30 Hz, 40 Hz, 50 Hz, 60 Hz or any two of the above values.

[0053] In a specific embodiment of the present invention, the lithium replenishing agent and lithium iron phosphate material can be integrated to form an integrated cathode material; the integrated cathode material containing the lithium replenishing agent is prepared by the following method: the lithium replenishing agent is dispersed in a solvent, then mixed with a second carbon source, and then lithium iron phosphate material is added, spray dried to obtain a master powder; the master powder is sintered to obtain an integrated cathode material containing the lithium replenishing agent.

[0054] In a specific embodiment of the present invention, the lithium replenishing agent is as described above and will not be repeated here; the solvent is preferably water; the solid content of the solution after the lithium replenishing agent is dispersed in the solvent is preferably 0.1% to 5%; optionally, the solid content of the solution after the lithium replenishing agent is dispersed in the solvent is 0.1%, 0.5%, 0.7%, 1%, 2%, 3%, 4%, 5% or any two of the above values.

[0055] In one specific embodiment of the present invention, the second carbon source includes, but is not limited to, one or more of carbon nanotubes, sucrose, and glucose; the mass of the second carbon source is preferably 2% to 6% of the mass of the lithium supplement; optionally, the mass of the second carbon source is 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6% of the mass of the lithium supplement, or a range between any two of the above values.

[0056] In one specific embodiment of the present invention, a conductive agent may also be added when adding the second carbon source; specifically, the conductive agent is preferably added in the form of a conductive slurry; the conductive slurry is preferably a CNT, carbon fiber, carbon black or graphite slurry with a solid content of 3% to 5.5%.

[0057] In a specific embodiment of the present invention, the spray drying temperature is preferably 180℃~240℃; optionally, the spray drying temperature is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃ or any two of the above values; the spray drying time is preferably 8~12 h; optionally, the spray drying time is 8 h, 9 h, 10 h, 11 h, 12 h or any two of the above values. During spray drying, fine-particle, highly uniform masterbatch powder can be obtained by reducing the feed rate and increasing the atomizer rotation speed. Specifically, the feed rate is preferably 45-80 mL / min; optionally, the feed rate is 45 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, or any two of the above values. The rotation speed of the atomizer is preferably 300-400 Hz; optionally, the rotation speed of the atomizer is 300 Hz, 320 Hz, 350 Hz, 380 Hz, 400 Hz, or any two of the above values.

[0058] The masterbatch powder is sintered to obtain an integrated cathode material containing a lithium supplement agent; the sintering temperature is preferably 250℃~350℃; optionally, the sintering temperature is 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃ or any two of the above values; the sintering time, i.e., the holding time, is preferably 3~5 h; optionally, the sintering time is 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any two of the above values.

[0059] In a specific embodiment of the present invention, after the master powder is sintered, it is preferably crushed to obtain an integrated cathode material containing a lithium supplement; the particle size of the integrated cathode material can be controlled by crushing; the crushing time is preferably 1 to 3 minutes.

[0060] In a specific embodiment of the present invention, the integrated cathode material containing the lithium replenishing agent can be further prepared by the following method: the lithium replenishing agent is dispersed in a solvent and then mixed with a second carbon source and a catalyst, and then lithium iron phosphate material is added; the subsequent preparation is the same as described above, and will not be repeated here; the catalyst is a transition metal oxide; the second carbon source includes, but is not limited to, one or more of carbon nanotubes, sucrose and glucose.

[0061] In another specific embodiment of the present invention, it is preferable to disperse the lithium supplement agent in a solvent and then mix it with a second carbon source, a conductive agent and / or a catalyst, and then add a lithium iron phosphate material; the second carbon source, the conductive agent and the catalyst are as described above, and will not be repeated here.

[0062] In one specific embodiment of the present invention, the conductive agent is preferably added in the form of a conductive paste; the conductive paste is preferably a CNT, carbon fiber, carbon black or graphite paste with a solid content of 3 to 5.5%.

[0063] The present invention also provides another method for preparing a cathode material containing a lithium replenishing agent. The method directly mixes the lithium replenishing agent with lithium iron phosphate materials to prepare a mixed, separate cathode material containing a lithium replenishing agent. Specifically, it may include the following steps: A) mixing the lithium replenishing agent with lithium iron phosphate materials to obtain a separate cathode material containing a lithium replenishing agent.

[0064] In a specific embodiment of the present invention, step A) specifically includes: preparing a lithium replenishing agent containing a second carbon coating layer, and then mixing it with a lithium iron phosphate material to obtain a separate cathode material containing the lithium replenishing agent; more specifically, dispersing the lithium replenishing agent in a solvent, then mixing it with a second carbon source, spray drying it, and then mixing it with a lithium iron phosphate material to obtain a separate cathode material containing the lithium replenishing agent.

[0065] Specifically, the solvent is preferably water; the second carbon source is as described above and will not be repeated here; the solid content of the solution after the lithium supplement is dispersed in the solvent is preferably 0.1% to 5%; optionally, the solid content of the solution after the lithium supplement is dispersed in the solvent is 0.1%, 0.5%, 0.7%, 1%, 2%, 3%, 4%, 5% or any two of the above values; the spray drying temperature is preferably 180℃ to 240℃; optionally, the spray drying temperature is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃ or any two of the above values; the spray drying time is preferably 8 to 12 h; optionally, the spray drying time is 8 h, 9 h, 10 h, 11 h, 12 h or any two of the above values. During spray drying, fine-particle, highly uniform powder can be obtained by reducing the feed rate and increasing the atomizer rotation speed. Specifically, the feed rate is preferably 45-80 mL / min; optionally, the feed rate is 45 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, or any two of the above values. The rotation speed of the atomizer is preferably 300-400 Hz; optionally, the rotation speed of the atomizer is 300 Hz, 320 Hz, 350 Hz, 380 Hz, 400 Hz, or any two of the above values.

[0066] Specifically, the mixing with lithium iron phosphate materials is preferably carried out in a mixing tank; the mixing speed is preferably 1000~3000 rpm; optionally, the mixing speed is 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm or any two of the above values; the mixing time with lithium iron phosphate materials is preferably 1~3 min; optionally, the mixing time with lithium iron phosphate materials is 1 min, 2 min, 3 min or any two of the above values.

[0067] In a specific embodiment of the present invention, step A) specifically includes: dispersing the lithium replenishing agent in a solvent, then mixing it with a second carbon source, a conductive agent and / or a catalyst, spray drying it, and then mixing it with lithium iron phosphate materials to obtain a split cathode material containing the lithium replenishing agent.

[0068] In a specific embodiment of the present invention, the catalyst is as described above and will not be repeated here; the conductive agent is preferably added in the form of a conductive slurry; the conductive slurry is as described above and will not be repeated here.

[0069] In one specific embodiment of the present invention, the positive electrode sheet includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector; the positive current collector includes, but is not limited to, copper foil, aluminum foil, etc.

[0070] In one specific embodiment of the present invention, the positive electrode active layer includes a positive electrode material; the mass of the positive electrode material is preferably 94.5% to 98.5% of the mass of the positive electrode active layer; optionally, the mass content of the positive electrode material in the positive electrode active layer is specifically 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 98%, 98.5% or any two of the above values.

[0071] In one specific embodiment of the present invention, the positive electrode active layer further includes a positive electrode binder and a positive electrode conductive agent; the positive electrode binder includes, but is not limited to, one or more of the binders polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and polyacrylonitrile (PAN); the mass of the positive electrode binder is preferably 1.3% to 2.2% of the mass of the positive electrode active layer; optionally, the mass of the positive electrode binder is 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, or 1.9% of the mass of the positive electrode active layer. The positive electrode conductive agent is 2.0%, 2.1%, 2.2%, or any two of the above values; the positive electrode conductive agent includes, but is not limited to, one or more of conductive carbon black, acetylene black, carbon nanotubes, graphene, and carbon fiber materials; the mass of the positive electrode conductive agent is preferably 0.5% to 1.5% of the mass of the positive electrode active layer; optionally, the mass of the positive electrode conductive agent is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% of the mass of the positive electrode active layer, or any two of the above values.

[0072] In a specific embodiment of the present invention, the positive electrode active layer preferably further includes a dispersant; the mass content of the dispersant in the positive electrode active layer is preferably 0.05% to 2%; optionally, the mass content of the dispersant in the positive electrode active material layer is 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2% or any two of the above values; the dispersant can be any dispersant well known to those skilled in the art, and there are no special limitations. In the present invention, it is preferably at least one of acrylic acid, acrylate, polyether ester, phosphate ester, small molecule alkanolamine, polyurethane, modified styrene / maleic anhydride, polyethyleneimine (PEI), hydrogenated nitrile butadiene rubber (HNBR), and polyvinylpyrrolidone (PVP).

[0073] Compaction density is a crucial parameter for lithium-ion batteries, directly affecting their capacity, energy density, internal resistance, and cycle performance. Generally, higher compaction density results in higher battery capacity because it increases the mass of active material per unit volume, thus enhancing energy storage capacity. However, excessive compaction density can hinder lithium-ion insertion and extraction, leading to a decrease in battery capacity. In this invention, the compaction density of the positive electrode sheet is preferably 2.4~2.7 g / cm³. 3 Optionally, the compaction density of the positive electrode sheet is 2.4 g / cm³. 3 2.42 g / cm 3 2.42 g / cm 3 2.46 g / cm 3 2.48 g / cm 3 2.5 g / cm 3 2.52 g / cm 3 2.54 g / cm 3 2.56 g / cm 3 2.58 g / cm 3 2.60 g / cm 3 2.62 g / cm 3 2.64 g / cm 3 2.66 g / cm 3 2.68 g / cm 3 2.7 g / cm 3 Or the range between any two of the above values.

[0074] The areal density of the positive electrode refers to the mass of active material per unit area of ​​the positive electrode sheet. It is a core parameter in lithium-ion battery design, directly affecting the battery's energy density and rate performance. Higher areal density means more active material per unit area, thus increasing the battery's energy density. However, excessively high areal density leads to increased internal resistance, affecting fast-charging performance. In this invention, the areal density of the positive electrode sheet is 300~500 g / m³. 2 Optionally, the areal density of the positive electrode is 300 g / m³. 2 320 g / m 2 340 g / m 2 360 g / m 2 380 g / m 2 400 g / m 2 420 g / m 2 440 g / m 2 460 g / m 2 480 g / m 2 500 g / m 2Or the range between any two of the above values.

[0075] Regarding the testing methods for compaction density and areal density, this invention does not limit the specific methods, but can be carried out according to the following methods: 1) Pretreatment: Discharge the battery at 0.33C to the lower limit voltage of 2.5V, take the empty battery, disassemble the electrode sheets, and soak the electrode sheets in dimethyl carbonate (DMC) solution for 4 hours. h; air dry 2) Use a punching machine to punch the pretreated positive electrode sheet into circular pieces of fixed area, denoted as S0. Take three circular pieces as parallel samples, and weigh the mass of the three circular pieces using an electronic balance. Take the average value and record it as M1. Use a micrometer to test the thickness of the positive electrode active layer in the three circular pieces (that is, the total thickness after removing the current collector), take the average value and record it as H. Finally, add an appropriate amount of deionized water to each of the three circular pieces, gently wipe off the coating on the circular pieces with lint-free paper to expose the copper foil, let it stand at room temperature (or dry) for 10 minutes, and after the copper foil is dry, weigh the mass of the three copper foil pieces, take the average value and record it as M0. Calculate the compaction density of the positive electrode sheet according to the following formulas: A = (M1-M0) / (H×S0); surface density = (M1-M0) / S0.

[0076] In one specific embodiment of the present invention, graphite is the optimal negative electrode material due to its high bulk capacity and low electrode potential.

[0077] In a specific embodiment of the present invention, the particle size Dv50 corresponding to the 50% volume cumulative distribution curve of the negative electrode material is preferably 3~20 μm; within this range, the side reactions between the negative electrode and the electrolyte can be reduced; optionally, the particle size Dv50 of the negative electrode material is 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or any two of the above values.

[0078] The present invention does not impose any special restrictions on the test method for the cumulative volume distribution particle size of the negative electrode material. Specifically, it can be carried out as follows: 1) Pretreatment: The battery is discharged at 0.33C to the lower limit voltage of 2.5V. The empty battery is taken out, the electrode is disassembled, and the electrode is soaked in dimethyl carbonate (DMC) solution for 4 hours and dried. The particle size of the material can be measured by a laser particle size distribution measuring instrument (Mastersizer 3000). The particle size distribution is measured according to the particle size distribution laser diffraction method (specific steps refer to GB / T19077-2016). The particle size corresponding to the cumulative particle size distribution percentage reaching 50% is Dv50.

[0079] In a specific embodiment of the present invention, the negative electrode material further includes a doping element; the doping element is preferably one or more of N, B, P, and S; the mass of the doping element is preferably 0.5% to 5% of the mass of the carbon material; optionally, the mass of the doping element is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the mass of the carbon material, or a range between any two of the above values. Doping modification can alter the electronic structure of the carbon material, improve electronic conductivity, widen the interlayer spacing, and improve lithium-ion diffusion kinetics, allowing more lithium to be inserted under the same conditions, indirectly affecting the total amount of lithium ions available in subsequent cycles, thereby affecting the amount of carbon-lithium composite material generated; simultaneously, it can accelerate lithium-ion transport at the interface, allowing for higher lithium insertion depths (i.e., higher carbon-lithium composite material content) at higher rates without lithium plating; it can also alleviate volume expansion, improve structural stability, and allow for deeper charge-discharge cycles.

[0080] In one specific embodiment of the present invention, the surface of the negative electrode material is further coated with amorphous carbon and / or a metal oxide; the metal oxide is preferably one or more of Al2O3, TiO2, and ZrO2. Coating the surface of the negative electrode material with amorphous carbon or a metal oxide can improve interface stability, reduce electrolyte decomposition and continuous SEI film growth, reduce initial irreversible capacity loss, and improve cycle performance. The preferred mass percentage of amorphous carbon coated on the surface of the negative electrode material is 2% to 8%; optionally, the mass percentage of amorphous carbon coated on the surface of the negative electrode material is 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any two of the above values; the preferred mass percentage of metal oxide coated on the surface of the negative electrode material is 0.5% to 3%; optionally, the mass percentage of metal oxide coated on the surface of the negative electrode material is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or any two of the above values.

[0081] In one specific embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer attached to at least one surface of the negative electrode current collector; the negative electrode current collector can be any negative electrode current collector known to those skilled in the art, and there are no special limitations, and the negative electrode current collector includes, but is not limited to, copper foil, aluminum foil, etc.

[0082] In one specific embodiment of the present invention, the mass of the negative electrode material is 90% to 99% of the mass of the negative electrode active layer; optionally, the mass content of the negative electrode material in the negative electrode active layer is specifically 90%, 92%, 94%, 96%, 96.4%, 97%, 98%, 99% or any two of the above values.

[0083] In a specific embodiment of the present invention, the negative electrode active layer further includes a negative electrode conductive agent; the mass content of the negative electrode conductive agent in the negative electrode active layer is preferably 0.5% to 5%; optionally, the mass content of the negative electrode conductive agent in the negative electrode active layer is 0.5%, 0.6%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any two of the above values; the negative electrode conductive agent can be any negative electrode conductive agent well known to those skilled in the art, and there are no special limitations. In the present invention, conductive agent SP and / or acetylene black are preferred.

[0084] In a specific embodiment of the present invention, the negative electrode active layer preferably further includes a negative electrode binder; the mass content of the negative electrode binder in the negative electrode active layer is preferably 1% to 5%; optionally, the mass content of the negative electrode binder in the negative electrode active layer is 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any two of the above values; the negative electrode binder can be any negative electrode binder known to those skilled in the art, and there are no special limitations. In the present invention, it is preferably one or more of polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR); the molecular weight of the PAA is preferably 30 to 100 W; optionally, the molecular weight of the PAA is 30 W, 40 W, 50 W, 60 W, 70 W, 80 W, 90 W, 100 W, or any two of the above values; the particle size of the SBR is preferably 120 to 180 nm; optionally, the particle size of the SBR is 120 nm, 130 nm, 140 nm, 150 nm, or 120 nm. nm, 160 nm, 170 nm, 180 nm, or any two of the above values.

[0085] In one specific embodiment of the present invention, the mass of the negative electrode binder is 1.2% to 2.6% of the mass of the negative electrode active layer.

[0086] In a specific embodiment of the present invention, the negative electrode active layer preferably further includes a dispersant; the mass content of the dispersant in the negative electrode active layer is preferably 0.05% to 2%; optionally, the mass content of the dispersant in the negative electrode active material layer is 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2% or any two of the above values; the dispersant can be any dispersant well known to those skilled in the art, and there are no special limitations. In the present invention, it is preferably at least one of acrylic acid, acrylate, polyether ester, phosphate ester, small molecule alkanolamine, polyurethane, modified styrene / maleic anhydride, polyethyleneimine (PEI), hydrogenated nitrile butadiene rubber (HNBR), and polyvinylpyrrolidone (PVP).

[0087] The areal density of the negative electrode also affects battery performance. Increasing the areal density increases the total amount of active material, thereby improving battery capacity and energy density. However, if the areal density of the negative electrode is too high, it will increase the lithium-ion migration path, leading to increased internal resistance. In a specific embodiment provided by this invention, the areal density of the negative electrode is preferably 180~220 g / m³. 2 Optionally, the areal density of the negative electrode sheet is 180 g / m³. 2 185 g / m 2 190 g / m 2 195 g / m 2 200 g / m 2 205 g / m 2 210g / m 2 215 g / m 2 220 g / m 2 Or the range between any two of the above values.

[0088] Compaction density is also one of the main factors affecting the cycle performance and rate discharge performance of lithium-ion batteries. Too low a compaction density leads to a loose electrode structure, reducing energy density and electron conduction efficiency. High compaction density can improve ion transport efficiency, but excessively high compaction density may clog active sites, resulting in performance degradation. Therefore, in a specific embodiment provided by this invention, the compaction density of the negative electrode sheet is preferably 1.20~1.80 g / cm³. 3 Optionally, the compaction density of the negative electrode sheet is 1.20 g / cm³. 3 1.30 g / cm 3 1.40 g / cm 3 1.50 g / cm 3 1.60 g / cm 3 1.70 g / cm 3 1.80 g / cm3 Or the range between any two of the above values.

[0089] According to the present invention, the battery further includes an electrolyte. As a key component of the battery, the electrolyte plays a significant conductive role between the positive and negative electrodes and is an ionic conductor. The electrolyte includes lithium salt, solvent, and additives.

[0090] Lithium salts play a conductive role in the electrolyte. In a specific embodiment of the present invention, the lithium salt can be any lithium salt well known to those skilled in the art, without any special limitations. Preferably, the present invention includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the lithium salt in the electrolyte is preferably 0.5~2 mol / L; optionally, the concentration of the lithium salt in the electrolyte is 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, etc. mol / L, 2 mol / L, or any two of the above values.

[0091] The primary function of the solvent in the electrolyte is to dissolve lithium salts. In this invention, the solvent includes, but is not limited to, one or more of carbonate solvents, carboxylic acid ester solvents, sulfone solvents, nitrile solvents, and ether solvents. The carbonate solvent includes, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate, methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, and fluoroethylene carbonate. The carboxylic acid ester solvent includes, but is not limited to, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, and 1,4-butyrolactone. The sulfone solvent includes, but is not limited to, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The nitrile solvent includes, but is not limited to, acetonitrile. The ether solvent includes, but is not limited to, dimethyl glycol ether (DME), dimethyl propylene glycol ether (PGME), and tetrahydrofuran.

[0092] In this invention, the value of c can be adjusted by the content of solvent EC, additives such as vinylene carbonate and fluoroethylene carbonate in the electrolyte.

[0093] In one specific embodiment of the present invention, the solvent comprises ethylene carbonate (EC); the mass of the ethylene carbonate is preferably 30% to 60% of the electrolyte mass; optionally, the mass of the ethylene carbonate is 30%, 35%, 40%, 45%, 50%, 55%, 60% of the electrolyte mass, or a range between any two of the above values. Increasing the EC content in the electrolyte can improve the ionic conductivity of the electrolyte and enhance the ion transport efficiency at 25°C, thereby improving [the electrolyte's conductivity].

[0094] According to the present invention, the additive includes at least one of fluoroethylene carbonate (FEC) and vinylene carbonate (VC); vinylene carbonate can promote the formation of the solid electrolyte interphase (SEI) film on the negative electrode; fluoroethylene carbonate (FEC) can significantly improve the overall performance of the battery by optimizing the structure and stability of the solid electrolyte interphase (SEI) film. In a specific embodiment provided by the present invention, the mass of the vinylene carbonate is preferably 0.5% to 2.5% of the electrolyte mass; within this range, it can form a dense and well-formed solid electrolyte interphase film on the negative electrode, reducing side reactions between the negative electrode and the electrolyte, and reducing gas production inside the battery; optionally, the mass of the vinylene carbonate is 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5% of the electrolyte mass, or a range between any two of the above values.

[0095] In one specific embodiment of the present invention, the mass of the fluoroethylene carbonate is preferably 1% to 3% of the mass of the electrolyte; optionally, the mass of the fluoroethylene carbonate is 1%, 1.5%, 2%, 2.5%, 3% of the mass of the electrolyte or any two of the above values.

[0096] In one specific embodiment of the present invention, the additive may further include one or more of the following: anisole derivatives, polymeric monomers (such as xylene, phenylcyclohexane), boron / nitrogen heterocyclic compounds (such as LiBOB), vinyl ethylene carbonate (VEC), 1,3-propanesulfonate lactone (1,3-PS), vinyl sulfite (ES), and vinyl sulfate (DTD).

[0097] According to the present invention, the battery preferably further includes a separator; the separator can be any separator well known to those skilled in the art, and there are no special limitations. In the present invention, the separator can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride; a coating can also be provided on the surface of the separator, and the coating can be an inorganic coating and / or an organic coating; wherein, the inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide and boehmite; the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0098] In one specific embodiment of the present invention, the diaphragm includes a base membrane and a coating disposed on at least one surface of the base membrane; the coating includes aluminum oxide; the thickness of the coating is preferably 1~4 μm.

[0099] In one specific embodiment of the present invention, the porosity of the diaphragm is preferably 35% to 50%.

[0100] The battery provided by this invention can be prepared according to methods well known to those skilled in the art, and there are no special limitations. Specifically, it can be prepared according to the following steps:

[0101] S1) Positive electrode sheet preparation: The positive electrode material, positive electrode conductive agent, positive electrode binder and dispersant are dispersed in NMP to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector to obtain a double-sided coated positive electrode sheet; then it is rolled and cut to obtain the positive electrode sheet;

[0102] S2) Negative electrode preparation: The negative electrode material, negative electrode conductive agent, negative electrode binder and dispersant are dispersed in deionized water to obtain a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector to obtain a double-sided coated electrode sheet; then it is rolled and cut to obtain the negative electrode sheet;

[0103] S3) Electrolyte preparation: Mix the solvent with the lithium salt to obtain the electrolyte. Additives may also be added as needed.

[0104] 4) Assembly and formation: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Then, they are wound to obtain the bare cell. The bare cell is placed in the outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, the battery is obtained.

[0105] In one specific embodiment of the present invention, the battery includes a cell; the cell is the basic unit of the battery, typically comprising a positive electrode, a negative electrode, and a separator. Lithium-ion cells primarily function by the intercalation and deintercalation of lithium ions between the positive and negative electrodes. In a cylindrical cell, a three-layer thin-film structure is wound into a cylindrical electrode assembly, while in a cuboid cell, the thin-film structure is wound or stacked into an electrode assembly with a generally cuboid shape. The cell thickness is greater than or equal to 20 mm, which can improve the battery's energy density.

[0106] The present invention also provides an electronic device comprising the battery described above. The electrochemical device serves as the power source for the electronic device.

[0107] The electronic device refers to any device that can utilize electrical energy and convert it into mechanical energy, thermal energy, light energy, or one or more other energy forms, such as electric motors, electric heaters, and electric light sources. Specifically, it can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, and energy storage systems. Mobile devices can include mobile phones, laptops, drones, robot vacuum cleaners, e-cigarettes, etc.; electric vehicles can include pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0108] To further illustrate the present invention, the following describes a battery provided by the present invention in detail with reference to embodiments; the molecular weight of PVDF used in the embodiments and comparative examples is about 70 W.

[0109] All reagents used in the following examples are commercially available.

[0110] Examples 1-21 and Comparative Examples 1-6

[0111] 1) Preparation of cathode materials:

[0112] Preparation of lithium iron phosphate materials: Lithium carbonate, ferrous phosphate, titanium oxide, glucose, and sucrose (with a glucose to sucrose mass ratio of 2:1 as the first carbon source; the molar ratios of lithium in lithium carbonate and iron in ferrous phosphate are shown in Table 1; the amount of the first carbon source added is shown in Table 1) are mixed uniformly; the mixture is dispersed in a solvent and wet-milled (specific conditions are shown in Table 1), then spray-dried (the spray drying pressure is 0.5 MPa, the inlet temperature is 250℃, and the outlet temperature is 100℃) to obtain powder; the powder is calcined once (specific conditions are shown in Table 1), then pulverized to obtain a first-calcined product; the first-calcined product is calcined a second time (specific conditions are shown in Table 1), then pulverized (airflow crushing, frequency 40Hz) to obtain lithium iron phosphate materials.

[0113] Preparation of integrated cathode material containing lithium supplementation agent: Lithium oxalate (LCO) was dissolved in water (solid content 0.71%). After complete dissolution, the lithium supplementation agent aqueous solution was poured into carbon source slurry (CNT, solid content 4.5%, the amount of carbon source added based on solid content is shown in Table 1) in batches. After complete and uniform dispersion, a mixed solution was obtained. A pre-dispersed catalyst solution (Co3O4, solid content 2%, the specific amount added based on solid content is shown in Table 1) was dissolved in the mixed solution. After the mixed solution was uniformly dispersed, lithium iron phosphate material was added in batches (the ratio of lithium oxalate to lithium iron phosphate material is shown in Table 1). After complete and uniform mixing, centrifugal spray drying (200℃) was performed to obtain LFP-LCO integrated master powder. An appropriate amount of master powder was weighed and placed in a tube furnace with nitrogen atmosphere for high-temperature sintering (300℃) and held for 4 h to obtain LFP-LCO integrated precursor. Then, it was crushed in a crusher to obtain integrated cathode material; the total crushing time was 2 min, with each crushing time being 1 min and then cooled before crushing again.

[0114] Preparation of a split cathode material containing a lithium supplement agent: An appropriate amount of lithium supplement agent was dissolved in water (specific types are shown in Table 1, concentration 0.71%, LFO in Table 1 is lithium iron phosphate Li5FeO4). After complete dissolution, the solution was poured in batches into a pre-dispersed carbon source slurry (CNT, solid content 4.5%, the amount of carbon source added based on solid content is shown in Table 1). After uniform dispersion, an appropriate amount of catalyst (Co3O4, solid content 2%, the specific amount added based on solid content is shown in Table 1) was added. After the catalyst was uniformly dispersed, it was centrifuged and spray-dried (200℃), and then dried in a 100℃ drying oven for 12 h to obtain the lithium supplement material. A mixing tank was used to mix the lithium supplement material and lithium iron phosphate materials in a certain proportion (specifically shown in Table 1) to obtain a mixed split cathode material.

[0115] 2) Preparation of positive electrode sheet: The above-mentioned integrated positive electrode material (Examples 1-13, Examples 19-21 and Comparative Examples 1-4) or the split positive electrode material (Examples 14-18, Comparative Examples 5 and Comparative Examples 6) were used as the main material. The main material was mixed evenly with the binder PVDF, the conductive agent SP and the dispersant polyethyleneimine (main material: 96.8%, binder ratio: 2.0%, conductive agent: 1.0%, dispersant: 0.2%) and dispersed in NMP to obtain a positive electrode slurry. The positive electrode slurry was coated on aluminum foil to obtain a double-sided coated positive electrode sheet. Then, it was rolled and cut to obtain the positive electrode sheet. During the preparation of the positive electrode sheet, the areal density was 400 g / m³. 2 Compacted to 2.55 g / cm³ 3 .

[0116] 3) Negative electrode preparation: Graphite, the negative electrode material, is mixed uniformly with conductive agent SP, binder CMC, and dispersant polyethyleneimine according to the following mass ratio (96.4% negative electrode material, 1.8% binder, 0.6% conductive agent, and 1.2% dispersant) in deionized water to obtain a negative electrode slurry. This negative electrode slurry is then coated onto copper foil to obtain a double-sided coated electrode. After rolling and cutting, the negative electrode sheet is obtained with an areal density of 180 g / m³. 2 Compacted density 1.65 g / cm³ 3 .

[0117] 4) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed to obtain an organic solvent. Then, fully dried lithium salt LiPF6 and additives are dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L. The specific composition of the solvent and additives is shown in Table 2. Except for the change in EC content, the solvent is composed of DMC and EMC in a mass ratio of 1:1.

[0118] 5) The diaphragm is made of PE.

[0119] 6) Assembly and Formation: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Then, they are wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, standing (temperature 25℃, 8 h), formation, and shaping processes, a lithium-ion battery (size 72×173×204 mm) is obtained. The formation conditions are as follows: after the battery is left to stand for 2 h, it is charged at a constant current of 0.05C for 60 min, left to stand for 5 min, charged at 0.2C to 3.9V, left to stand for another 5 min, charged at 0.05C to 4.3V, left to stand for 5 min, and discharged at 0.3C for 30 min. The gas production test is for the gas production during the formation process.

[0120] Methods for testing Ti doping levels:

[0121] 1) Pretreatment: Discharge the battery to the lower limit voltage of 2.5V at 0.33C, disassemble the empty lithium-ion battery, and obtain the electrode sheet. Soak the positive electrode sheet in DMC (dimethyl carbonate) at room temperature for 60 min, remove it, and air dry it at room temperature with humidity ≤15%; 2) Accurately weigh 0.5 g of positive electrode active material powder, disperse it in 20 mL of water, add 10 mL of nitric acid, mix well, and then heat it. After the positive electrode active material powder dissolves, dilute the material with water to 100 mL to obtain the test solution; 3) Perform ICP test on the test solution. Before the test, a standard solution must be prepared. The linear correlation coefficient of the standard concentration must be above 0.999 to be used as a normal standard. Dilute the 1000 mg / L standard solution with deionized water to different concentrations (generally 0, 1 mg / 100 mL, 2 mg / 100 mL, 3 mg / 100 mL), select the element detection wavelength, and set the experimental conditions: based on the characteristics of the sample and the element to be detected, set appropriate ICP instrument operating conditions: gas flow rate 0.5 L / min, power 1150 W, and select the element detection wavelength, which depends on the element to be tested.

[0122] The Ti doping content in the lithium iron phosphate materials was found to be 2685 ppm.

[0123] The testing method for Fe is the same as that for Ti.

[0124] Testing of the types of carbon-lithium composites in the negative electrode:

[0125] 1) Pretreatment: Discharge the battery at 0.33C to the lower limit voltage of 2.5V, remove the empty battery, disassemble the electrodes, and soak the electrodes in dimethyl carbonate (DMC) solution for 4 hours; then air dry.

[0126] 2) The electrode was tested using an XRD diffractometer. The test conditions were set as follows: copper target, scanning voltage of 40 kV, current of 40 mA, scanning range of 5-90°, and scanning speed of 4° / min. The XRD was calibrated using the silicon internal standard method. The X-ray source was started, and the type of lithium-carbon compound was determined by the peak position. The characteristic diffraction peaks of LiC6 were 2θ = 25.9° and 43.3°.

[0127] Tests revealed that the lithium-carbon composites in Examples 1-21 and Comparative Examples 1-6 were all LiC6.

[0128] Methods for detecting the content of carbon-lithium complexes:

[0129] Lithium-carbon complexes react with ethanol to produce hydrogen gas. Taking LiC6 as an example, the core reaction can be simplified to: 2LiC6 + 2C2H5OH → 2C2H5OLi + H2↑ + 12C. The amount of LiC6 can be determined by the hydrogen content, which can be tested using the following methods:

[0130] 1) Pretreatment: The battery is discharged to 2.5V at 0.33C, then charged to 3.65V at a constant current of 0.33C, and then charged to the cutoff current of 0.05C at a constant voltage to obtain a fully charged battery. The fully charged battery is disassembled, the negative electrode is removed, and the negative electrode is soaked in dimethyl carbonate (DMC) solution for 4 hours and then dried.

[0131] A single fully charged negative electrode and 99.7% anhydrous ethanol were placed in an aluminum-plastic bag, sealed, and vacuumed. The volume V1 before the reaction was measured. The ethanol bag was then punctured under pressure, and the negative electrode and ethanol reacted to produce gas. After 12 hours, the volume V2 after the reaction was measured. The amount of gas generated was obtained by subtracting V1 from V2.

[0132] Calculate the mass of LiC6: Mass of LiC6 = Difference in gas production × Hydrogen density × Molecular weight of LiC6 / 1000 = (V2 - V1) × 0.0899 × 79 / 1000;

[0133] Take a single negative electrode sheet and measure its mass m1. Then scrape off the active layer and measure the mass m2 of the copper foil. The mass of the active material layer of the negative electrode sheet = m1 - m2.

[0134] Finally, the content of LiC6 in the negative electrode active layer was calculated as a = mass of LiC6 / mass of the negative electrode active layer. The results are shown in Table 2.

[0135] Detection method for Dn10 in the second particle of lithium iron phosphate materials:

[0136] The secondary battery in its empty state (discharged at 0.33C to the lower limit voltage of 2.5V) was disassembled. The obtained positive electrode sheet was soaked in dimethyl carbonate at 25℃ for 2 hours and dried. Then, the positive electrode active layer powder on the positive electrode sheet was scraped off and used as a sample. The sample was fixed with conductive adhesive and polished with CP argon ion to deposit a conductive film. It was placed on the sample stage and observed under a scanning electron microscope (SEM). The microscope was adjusted to 10kx and then the first and second particles were determined by particle size. The first lithium iron phosphate particle size (i.e., diameter) was greater than or equal to 1μm, and the second particle size (diameter) was less than 1μm. The diameter of the second particles in the measurement area was measured using Nano Measure software. The diameter of 100 second particles was measured, and the particle size Dn10 corresponding to the number of 10% of the 100 second particles was counted. The results are shown in Table 2.

[0137] Test method for the volumetric cumulative distribution particle size of negative electrode materials:

[0138] 1) Pretreatment: Discharge the battery at 0.33C to the lower limit voltage of 2.5V, remove the empty battery, disassemble the electrode, soak the electrode in dimethyl carbonate (DMC) solution for 4 hours, air dry, scrape off the negative electrode material on the surface of the negative electrode current collector, the particle size of the material can be measured using a laser particle size distribution measuring instrument (Mastersizer 3000), according to the particle size distribution laser diffraction method (specific steps refer to GB / T19077-2016), the particle size corresponding to the cumulative particle size distribution percentage reaching 50% is Dv50.

[0139] High-temperature and room-temperature discharge capacity:

[0140] At 25°C, the battery is discharged at 0.33C to the lower limit voltage of 2.5V, then charged at 0.33C to the upper limit voltage of 3.65V with a cutoff current of 0.05C, and then discharged at 0.33C to the lower limit voltage of 2.5V. This process is repeated twice, and the discharge capacity of the second cycle is taken as the battery discharge capacity Q1.

[0141] The battery was then left to stand at a high temperature of 45°C for 30 minutes, then charged at 0.33C to the upper limit voltage of 3.65V with a cutoff current of 0.05C, and then discharged at 0.33C to the lower limit voltage of 2.5V. This was done as one cycle, and the charge and discharge cycle was repeated for two weeks. The discharge capacity of the second week was taken as the high temperature discharge capacity Q2.

[0142] The ratio Q2 / Q1 is c, and the results are shown in Table 2.

[0143] Methods for testing the amount of gas produced during chemical formation:

[0144] After the battery is fabricated, its volume is tested using the water displacement method; then, the battery is removed and subjected to the formation process as follows:

[0145] After the battery was left to stand for 2 hours, it was charged at a constant current of 0.05C for 60 minutes, left to stand for 5 minutes, charged at 0.2C to 3.9V, left to stand for another 5 minutes, charged at 0.05C to 4.3V, left to stand for 5 minutes, discharged at 0.3C for 30 minutes, and then the process was completed. The volume of the battery after the formation was completed was also tested using the water displacement method.

[0146] After the formation process is complete, remove the battery, dry it, and charge it at 0.33C to the upper limit voltage of 3.65V and the cutoff current of 0.05C at 25℃. Then discharge it at 0.33C to the lower limit voltage of 2.5V. Repeat steps 1)-4) twice. Use the discharge capacity of the second cycle as the battery discharge capacity Q. 1) Charge at a constant current rate of 1C to 3.65V and charge at a constant voltage rate until the current drops to 0.05C; 2) Let it stand for 30 minutes; 3) Discharge at a 1C rate to 2.5V; 4) Let it stand for 30 minutes.

[0147] The specific steps for testing the volume of a secondary battery using the above water displacement method are as follows: (i) Add an appropriate amount of pure water to the container and test its density with a hydrometer and record it; (ii) Adjust the balance to be level and tare the electrolyte (tare the electrolyte before testing each secondary battery); (iii) Submerge the main body of the secondary battery along with its tabs in the solution, ensuring that the secondary battery does not contact the container wall, and read and record the data as T after stabilization; (iv) Turn off the balance and seal the container to prevent the reagent from evaporating. The formula for calculating the volume of a secondary battery is T / ρ_liquid; where, before and after formation, tests are performed to obtain T0 and T1 respectively; then the difference between V1 and V0 is: V1-V0=T1 / ρ_liquid-T0 / ρ_liquid;

[0148] Formation gas production = (V1-V0) / secondary battery capacity Q;

[0149] The resulting gas production is shown in Table 2.

[0150] Battery energy density testing methods:

[0151] The weight of the battery was measured and recorded as m. The battery was placed in a fixture and a force of 3000 N was applied. It was charged to 3.65 V with a constant current of 0.33 C, and then left to rest for 30 min. It was then discharged to the lower limit voltage of 2.5 V with a constant current of 0.33 C, and left to rest for 30 min. This cycle was repeated 3 times. The discharge capacity (in Ah) and energy E (average of three cycles) were obtained. The discharge energy density = E / m (in Wh / kg). The results are shown in Table 2.

[0152] Table 1. Preparation of cathode materials

[0153]

[0154]

[0155]

[0156] Table 2 Battery electrolyte and negative electrode parameters and test results

[0157]

[0158]

[0159] Based on Examples 1-21 and Comparative Examples 1-6, it can be seen that when the formula (a / b)×c falls within the range of 2-5, the energy density of the battery is not less than 155Wh / kg and the gas production is not higher than 68.5 mL / Ah.

[0160] Furthermore, by further controlling a / b within the range of 1.8 to 3 and c within the range of 1.2 to 1.4, the energy density of the battery can be made not less than 166 Wh / kg and the gas production not more than 55.5 mL / Ah; or, further, when the formula (a / b) × c falls within the range of 2.5 to 3.5, the energy density of the battery can be made not less than 174 Wh / kg and the gas production not more than 37.2 mL / Ah.

[0161] Furthermore, by simultaneously controlling a / b within the range of 1.8 to 3 and c within the range of 1.2 to 1.4, the formula (a / b) × c falls within the range of 2.5 to 3.5, which can make the energy density of the battery no less than 180 Wh / kg and the gas production no more than 32 mL / Ah.

[0162] As can be seen from Examples 1 and 14 (split cathode materials with lithium oxalate as lithium supplement), Examples 5 and 15 (split cathode materials with lithium oxalate as lithium supplement), under similar conditions, although the gas production is similar between integrated cathode materials and split cathode materials, integrated cathode materials can significantly improve the energy density of batteries.

[0163] The amount of gas produced by a battery varies depending on the type of lithium supplement used. When lithium oxalate is used as the lithium supplement, the gas production of the battery is no higher than 68.5 mL / Ah when (a / b)×c is controlled within the range of 2 to 5. When LFO is used as the lithium supplement, the gas production of the battery is no higher than 17.8 mL / Ah. This is due to the properties of the lithium supplement itself. When lithium oxalate is used as the lithium supplement, the gas production can be further reduced by adjusting the range of a / b and c, while increasing the energy density of the battery.

[0164] The results of Comparative Example 4 show that the secondary sintering temperature exceeded 800℃ during the preparation of lithium iron phosphate materials, resulting in the formation of impurities and a decrease in Fe content, which in turn led to a significant reduction in the energy density of the battery.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A battery, characterized by, The battery comprises a positive electrode sheet and a negative electrode sheet; The positive electrode sheet comprises a positive electrode active layer; the positive electrode active layer comprises a positive electrode material; the positive electrode material comprises a lithium iron phosphate material; the mass ratio of Fe element in the positive electrode active layer is b; The negative electrode sheet comprises a negative electrode active layer; the negative electrode active layer comprises a negative electrode material; the negative electrode material comprises a carbon material; under the state of 100% SOC of the battery, the negative electrode active layer further comprises a carbon lithium compound; the ratio of the mass of the carbon lithium compound to the mass of the negative electrode active layer is a; The ratio of the specific capacity of the battery under the condition of 0.33C discharge at high temperature 45℃ to the specific capacity of the battery under the condition of 0.33C discharge at normal temperature 25℃ is c; the battery satisfies the relationship: (a / b)×c=2~5.

2. The battery of claim 1, wherein, The battery satisfies the relationship: (a / b)×c=2.5~3.

5.

3. The battery according to claim 1 or 2, characterized in that, The range of a / b is 1.4~4; And / or, the range of c is 1.05~1.

5.

4. The battery of claim 3, wherein, The range of a / b is 1.8~3; And / or, the range of c is 1.2~1.

4.

5. The battery of claim 1, wherein, The range of b is 0.25~0.35; And / or, the range of a is 0.5~0.

94.

6. The battery of claim 5, wherein, The range of b is 0.3~0.33; And / or, the range of a is 0.6~0.

8.

7. The battery according to claim 1 or 2, characterized by The range of a is 0.72~0.

8.

8. The battery of claim 1, wherein, The carbon lithium compound comprises LiC6.

9. The battery of claim 1, wherein, The lithium iron phosphate material comprises first particles and second particles; the diameter of the first particles is greater than or equal to 1 μm; the diameter of the second particles is less than 1 μm; the range of a / b is 1.4~3.

5.

10. The battery of claim 9, wherein, The particle diameter corresponding to the cumulative distribution of 10% of the second particles is Dn10, and the range of Dn10 is 0.1~0.5 μm.

11. The battery of claim 1, wherein, The lithium iron phosphate material further comprises a first carbon coating layer; the thickness of the first carbon coating layer is 1~10 nm.

12. The battery of claim 1, wherein, The positive electrode active layer further comprises a lithium supplement agent and / or reaction residues of the lithium supplement agent; the lithium supplement agent comprises at least one of an iron-containing lithium supplement agent, a nickel-containing lithium supplement agent, and lithium oxalate; the reaction residues of the lithium supplement agent comprise LiFeO2 and / or LiNiO2.

13. The battery of claim 12, wherein, The surface of the lithium supplement agent and / or the reaction residues of the lithium supplement agent is further provided with a second carbon coating layer; the thickness of the second carbon coating layer is 1~15 nm.

14. The battery of claim 13, wherein, The reaction residues of the lithium supplement agent comprise LiFeO2; the thickness of the second carbon coating layer on the surface of the LiFeO2 is 3~15 nm.

15. The battery of claim 12, wherein, The positive electrode active layer further comprises a catalyst; the catalyst is selected from one or more of cobalt oxide, iron oxide, nickel oxide, manganese dioxide, copper oxide, titanium dioxide, and zinc oxide.

16. The battery of claim 1, wherein, The lithium iron phosphate material comprises lithium iron phosphate and / or doped modified lithium iron phosphate; The doping element in the doped modified lithium iron phosphate comprises Ti and / or V.

17. The battery of claim 16, wherein, The doping amount of Ti is 600~3000 ppm.

18. The battery of claim 16, wherein, The doping amount of V is 500~2000 ppm.

19. The battery of claim 1, wherein, The surface of the negative electrode material is coated with amorphous carbon and / or metal oxide.

20. The battery of claim 19, wherein, The metal oxide is selected from one or more of Al2O3, TiO2, and ZrO2.

21. The battery of claim 1, wherein, The negative electrode material further comprises a doping element; the doping element is selected from one or more of N, B, P and S.

22. The battery of claim 21, wherein, The mass of the doping element is 0.5% to 5% of the mass of the carbon material.

23. The battery of claim 1, wherein, The particle size at which the volume cumulative distribution of the negative electrode material reaches 50% is Dv50, and the range of Dv50 is 3 to 20 μm; And / or, the surface density of the negative electrode sheet is 180 ~ 220 g / m 2 ; And / or, the compaction density of the negative electrode sheet is 1.2~1.8 g / cm 3 .

24. The battery of claim 1, wherein, Further comprising an electrolyte; the electrolyte comprises a solvent and an additive; The additive comprises at least one of fluoroethylene carbonate and vinylene carbonate; The solvent comprises ethylene carbonate.

25. The battery of claim 24, wherein, The additive comprises vinylene carbonate and fluoroethylene carbonate; The electrolyte satisfies at least one of the following characteristics (a) to (c): (a) The mass of the vinylene carbonate is 0.5% to 2.5% of the mass of the electrolyte; (b) The mass of the fluoroethylene carbonate is 1% to 3% of the mass of the electrolyte; (c) The mass of the ethylene carbonate is 30% to 60% of the mass of the electrolyte.

26. The battery of claim 1, wherein, Comprise a battery cell; the thickness of the battery cell is greater than or equal to 20 mm.

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