Battery cell, battery device, and electric device

Abstract

The application discloses a battery monomer, a battery device and an electric equipment. The battery monomer comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode film layer, a first region and a second region of the positive electrode film layer, the first region comprises iron elements and phosphorus elements, a ratio of a molar ratio of the phosphorus elements to the iron elements is 0.5-1.5, the second region comprises the phosphorus elements and transition metal M, a ratio of a molar ratio of the phosphorus elements to the transition metal M is a, and 0<=a<=0.2 is satisfied, a negative electrode sheet and an electrolyte. The electrolyte comprises an additive, the additive comprises one or more of a phosphorus-containing additive, a fluorine-containing additive and a sulfur-containing additive, and a sum of mass proportions of the phosphorus-containing additive, the fluorine-containing additive and the sulfur-containing additive accounts for 0.2%-2.1% based on a total mass of the electrolyte. Thus, the cycle life and the energy density of the battery are improved.

Description

[0001] This application is a divisional application of the original patent application (i.e., the parent application) with the application date of August 22, 2024, application number of 2024111615925, and invention title of "Battery cell, battery device and power consumption device". Technical Field

[0002] This application relates to the field of batteries, specifically to battery cells, battery devices, and electrical equipment. Background Technology

[0003] Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. Long-term energy storage products generally have a service life of more than 20 years, requiring high battery life. Adding lithium supplements to the positive electrode can improve battery life to some extent, but the improvement is limited, and the battery energy density is relatively low, making it difficult to meet the requirements of lightweighting and miniaturization. Since lithium supplements need to decompose under high pressure, there is also the problem of incompatibility between the electrolyte and the positive and negative electrodes under high pressure. Summary of the Invention

[0004] The first aspect of this application provides a battery cell, the battery cell comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer comprising a plurality of first regions and a plurality of second regions; the first regions comprising a positive electrode active material, the first regions comprising iron and phosphorus, the molar ratio of phosphorus to iron being 0.5-1.5; the second regions comprising a lithium supplement agent, the second regions comprising the phosphorus and a transition metal M, the transition metal M comprising Ni, Co, V, Cr, and Mn. The battery comprises one or more of the following elements: n, Fe, Mo, Cu, and Zn, wherein the molar ratio of phosphorus to transition metal M is α, and satisfies 0 ≤ a ≤ 0.2; a negative electrode sheet, comprising a negative current collector and a negative electrode film layer located on at least one side of the negative current collector; and an electrolyte comprising additives, including one or more of phosphorus-containing, fluorine-containing, and sulfur-containing additives, wherein the sum of the masses of the phosphorus-containing, fluorine-containing, and sulfur-containing additives accounts for 0.2%-2.1% based on the total mass of the electrolyte. This improves the capacity and structural stability of the positive electrode active material, enhances the stability of the electrolyte under high-voltage conditions, and improves the battery capacity and cycle life.

[0005] According to some embodiments of this application, the positive electrode active material includes lithium iron phosphate, wherein the longest diameter of the lithium iron phosphate is smaller than the shortest diameter of the lithium replenishing agent. This improves the lithium insertion / extraction kinetics of the positive electrode active material and reduces side reactions between the lithium replenishing agent and the electrolyte.

[0006] According to some embodiments of this application, the ratio of the longest diameter to the shortest diameter of the lithium replenishing agent is 1.2-2.5. This improves the delithiation efficiency while reducing the risk of the lithium replenishing agent being crushed during the rolling process.

[0007] According to some embodiments of this application, the lithium supplement includes Li x M y O z Where 1≤x≤5, 1≤y≤3, 2≤z≤8. This improves the lithium replenishment effect and increases the initial efficiency of individual battery cells.

[0008] According to some embodiments of this application, the lithium replenishing agent includes one or both of Li2NiO2 and Li5FeO4.

[0009] According to some embodiments of this application, the lithium supplement includes Li n NiO m and Li e FeO f One or two of them, wherein 0 < m ≤ 2, 0 ≤ n ≤ 2, 0 ≤ e ≤ 5, and 0 < f ≤ 4.

[0010] According to some embodiments of this application, the lithium supplement includes NiO. m and Li p FeO q One or two of them, where 0 < m ≤ 2, 0 ≤ p ≤ 1, and 0 < q ≤ 2.

[0011] Therefore, the decomposition of lithium replenishment agents can compensate for the active lithium ions consumed in the formation of SEI, thereby improving the initial efficiency and energy density of battery cells.

[0012] According to some embodiments of this application, the electrolyte further includes an electrolyte salt, and the molar concentration of the electrolyte salt in the electrolyte is 1.1 mol / L-1.5 mol / L. Therefore, during charging and discharging, concentration polarization caused by lithium ion migration can be reduced, the impact of concentration polarization on the lithium ion transport rate can be decreased, the internal resistance of the battery cell can be reduced, and the charging and discharging efficiency of the battery cell can be improved.

[0013] According to some embodiments of this application, the electrolyte salt includes one or both of lithium hexafluorophosphate and lithium fluorosulfonylimide. This improves the conductivity of the battery cell.

[0014] According to some embodiments of this application, the negative electrode film layer includes a negative electrode active material, which includes graphite. This reduces the cost of the battery cell and increases its energy density and cycle life.

[0015] According to some embodiments of this application, the compaction density of the positive electrode film is 2.2 g / cm³. 3 -2.6g / cm 3 2.4g / cm³ is an optional value. 3 -2.5g / cm 3 This increases the energy density of individual battery cells.

[0016] According to some embodiments of this application, the coating weight of the positive electrode film is 20 mg / cm³. 2 -60mg / cm 2 40mg / cm 2 -50mg / cm 2 This increases the energy density of individual battery cells.

[0017] According to some embodiments of this application, the graphite has a graphitization degree of 93%-97%, optionally 93%-96%. This increases the capacity of the graphite and improves the energy density of the battery cell.

[0018] According to some embodiments of this application, the volume average particle size Dv50 of the graphite is 8μm-20μm, and optionally 10μm-16μm. This reduces the number of active sites in the graphite, decreases Li consumption in SEI film formation, and improves the cycle life of the battery cell.

[0019] According to some embodiments of this application, the compaction density of the negative electrode film is 1.3 g / cm³. 3 -1.7g / cm 3 1.4g / cm³ is an optional value. 3 -1.6g / cm 3 This increases the energy density of individual battery cells.

[0020] According to some embodiments of this application, the coating weight of the negative electrode film is 10 mg / cm³. 2 -26mg / cm 2 15mg / cm 2 -20mg / cm 2 This increases the energy density of individual battery cells.

[0021] According to some embodiments of this application, the electrolyte further includes a solvent comprising cyclic carbonates and linear carbonates. Based on the total mass of the electrolyte, the cyclic carbonates account for 15%-25% of the mass, and the linear carbonates account for 50%-70% of the mass. This improves the stability of the electrolyte and extends the battery life.

[0022] According to some embodiments of this application, the cyclic carbonate includes ethylene carbonate.

[0023] According to some embodiments of this application, the linear carbonate includes one or both of dimethyl carbonate and ethyl methyl carbonate.

[0024] According to some embodiments of this application, the additive further includes carbonate additives, including one or more of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate. This forms an SEI film containing polymers, improving the stability of the SEI film and increasing battery life.

[0025] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 2%-5%, optionally 3%-4%. This forms an SEI film containing polymers, improving the stability of the SEI film and increasing battery life.

[0026] According to some embodiments of this application, the mass percentage of the phosphorus-containing additive is 0.01%-0.05% based on the total mass of the electrolyte.

[0027] According to some embodiments of this application, the mass percentage of the fluorinated additive is 0.05%-0.5% based on the total mass of the electrolyte.

[0028] According to some embodiments of this application, the mass percentage of the sulfur-containing additive is 0.1%-2% based on the total mass of the electrolyte.

[0029] Therefore, by keeping the contents of phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives within the above-mentioned range, a dense solid electrolyte membrane (CEI membrane) can be formed at the positive electrode during the first charging process, reducing the probability of the electrolyte being oxidized.

[0030] According to some embodiments of this application, the phosphorus-containing additive includes one or more of lithium difluorophosphate, tris(trimethylsilane) phosphate, triphenylphosphine oxide, triethyl phosphate, and ethylene trifluoroethyl phosphate.

[0031] According to some embodiments of this application, the fluorinated additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, perfluoroalkyl ethylene carbonate, lithium tetrafluoroborate, and lithium difluorooxalate borate.

[0032] According to some embodiments of this application, the sulfur-containing additive includes one or more of vinyl sulfite, propylene sulfite, vinyl sulfate, 4-methylethylene sulfate, and 1,3-propenesulfonyl lactone.

[0033] Therefore, a dense solid electrolyte interphase (CEI) film can be formed at the positive electrode during the first charging process, reducing the probability of the electrolyte being oxidized.

[0034] According to some embodiments of this application, the lithium iron phosphate has a unimodal particle size distribution with a particle size range of 1.5-1.7. This improves the kinetics of lithium insertion / extraction.

[0035] According to some embodiments of this application, based on the total mass of the positive electrode film, the mass percentage of the positive electrode active material is 90%-98%, and the mass percentage of the lithium replenishing agent can be 0.5%-8%. This improves the energy density and cycle life of the battery.

[0036] According to some embodiments of this application, at least a portion of the surface of the positive electrode active material has a first carbon coating layer, and the mass percentage of the first carbon coating layer is 0.5%-1.5% based on the total mass of the positive electrode active material. This improves the electronic conductivity of the positive electrode.

[0037] According to some embodiments of this application, at least a portion of the surface of the lithium replenishing agent has a second carbon coating layer, and the mass percentage of the second carbon coating layer is 1%-5%, optionally 2%-4%, based on the total mass of the lithium replenishing agent. This reduces the number of active sites exposed on the surface of the lithium replenishing agent and reduces side reactions between the lithium replenishing agent and the electrolyte.

[0038] According to some embodiments of this application, the positive electrode film layer further includes a conductive agent, which includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. This improves the conductivity of the positive electrode sheet.

[0039] According to some embodiments of this application, the battery cell further includes: a separator, the separator comprising: a base film made of polyethylene; an adhesive layer located on at least one side of the base film; and a ceramic layer located on the side of the adhesive layer away from the base film. This improves the oxidation resistance of the separator.

[0040] According to some embodiments of this application, the separator is disposed between the positive electrode and the negative electrode, with the ceramic layer close to the positive electrode. This improves the oxidation resistance of the separator.

[0041] According to some embodiments of this application, the volumetric energy density of the battery cell is greater than or equal to 410Wh / L.

[0042] According to some embodiments of this application, the volumetric energy density of the battery cell is greater than or equal to 420Wh / L.

[0043] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0044] A third aspect of this application provides an electrical device including a battery cell provided in the first aspect of this application, the battery cell being used to provide electrical energy.

[0045] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0046] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is an SEM image of the longitudinal section of the positive electrode sheet in Embodiment 1 of this application.

[0047] Figure 2 This is a schematic diagram of a battery according to one embodiment of this application.

[0048] Figure 3 yes Figure 2 An exploded view of a battery according to one embodiment of this application is shown.

[0049] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0050] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0051] Figure 6 yes Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0052] Figure 7 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0053] Explanation of reference numerals in the attached figures: 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Lithium iron phosphate particles; 7 Lithium replenishing agent particles. Detailed Implementation

[0054] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0055] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0056] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0057] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0058] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] Currently, judging from the development of the market, batteries are being used more and more widely, and can be applied to energy storage power systems such as hydropower, thermal power, wind power and solar power plants. However, the energy storage batteries in related technologies cannot simultaneously meet the requirements of long life and high safety.

[0060] This application aims to develop a battery cell with both high energy density and long lifespan. The battery cell of this application is developed by comprehensively controlling the relative contents of iron and phosphorus in the lithium iron phosphate positive electrode active material in the electrode sheet, the relative contents of phosphorus and transition metal M in the lithium replenishment region, and matching a suitable electrolyte formula, thereby developing a battery cell with high energy density and long lifespan.

[0061] In this application, the molar ratio of phosphorus to iron in the lithium iron phosphate region of the positive electrode is between 0.5 and 1.5. This reduces the proportion of lithium phosphate impurities in the lithium iron phosphate, increasing the capacity of the battery cell. Furthermore, it increases the phosphate content, improving the structural stability of the positive electrode active material and extending the cycle life of the battery cell. To further improve the cycle life and energy density, a lithium replenishing agent is introduced into the positive electrode. By controlling the relative content of phosphorus and transition metal M, the cycle life and energy density of the battery cell are optimized. However, when a lithium replenishing agent is introduced into the positive electrode, the high formation voltage required for its effectiveness can easily cause premature decomposition of electrolyte additives, preventing them from continuing to function in the later long-cycle process. Therefore, to reduce the probability of electrolyte decomposition caused by the high voltage during the formation stage, this application introduces phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives into the electrolyte. Utilizing the high HOMO energy level of these additives, the stability of the electrolyte under high voltage is improved, reducing the risk of redox decomposition and extending the battery's cycle life. Furthermore, the elements contained in the lithium replenishment material can also participate in the formation of the SEI film components, optimize the SEI film impedance, and benefit the battery cycle performance.

[0062] The battery cells proposed in this application can be used in electrical devices that use the battery cells as a power source or in various energy storage systems that use the battery cells as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0063] The first aspect of this application provides a battery cell, which includes a positive electrode, a negative electrode, and an electrolyte.

[0064] The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a plurality of first regions and a plurality of second regions. The first regions include a positive active material, which includes iron and phosphorus elements, and the molar ratio of phosphorus to iron is 0.5-1.5. The second regions include a lithium supplement agent, which includes the phosphorus element and a transition metal M. The transition metal M includes one or more of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn elements, and the molar ratio of phosphorus to transition metal M is a, which satisfies 0 ≤ a ≤ 0.2.

[0065] The negative electrode includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector.

[0066] The electrolyte includes additives, which include one or more of phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Based on the total mass of the electrolyte, the sum of the masses of the phosphorus-containing additives, the fluorine-containing additives, and the sulfur-containing additives accounts for 0.2%-2.1%.

[0067] Therefore, while reducing the probability of lithium phosphate formation and increasing the capacity of individual battery cells, increasing the phosphate content improves the structural stability of the positive electrode active material and extends the cycle life of the battery cells. By adding a lithium replenishing agent to the positive electrode, the decomposition of the lithium replenishing agent during the formation stage can compensate for the lithium ions consumed in the formation of the SEI film, improving the battery's initial efficiency and energy density. To reduce the probability of electrolyte decomposition caused by high voltage during the formation stage, the electrolyte includes one or more of the following: phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Under high voltage conditions, these additives can preferentially decompose to form stable CEI and SEI films, reducing the contact between the electrolyte and the positive and negative electrode surfaces, lowering the risk of electrolyte oxidation and decomposition, improving the stability of the electrolyte under high voltage conditions, and extending the battery's cycle life.

[0068] In this application, the region containing the positive electrode active material is the first region, and the region containing the lithium replenishing agent is the second region. The first region and the second region are uniformly distributed on the positive electrode sheet. Because the particle size and phosphorus (P) content of the positive electrode active material and the lithium replenishing agent differ significantly—the average particle size of the positive electrode active material is approximately 1 μm, while the longest diameter of a single lithium replenishing agent particle is >5 μm; the P content in the positive electrode active material is greater than 20%, while the P content in the lithium replenishing agent is <0.5%—the first region and the second region can be distinguished based on particle size and P content. Specifically, the region with a smaller average particle size and higher P content is the first region containing the positive electrode active material, while the region with a larger longest diameter and lower P content is the second region containing the lithium replenishing agent.

[0069] As an example, the molar ratio of phosphorus to iron in the first region can be 0.5, 0.7, 0.9, 1.1, 1.3, or 1.5, or a range of any of the above values. By ensuring the molar ratio of phosphorus to iron is within the above range, on the one hand, the risk of lithium phosphate formation due to excessive phosphorus content, thereby reducing the capacity of the battery cell, is reduced; on the other hand, the risk of insufficient phosphorus content leading to low phosphate content is reduced, improving the structural stability of the positive electrode active material and increasing the cycle life of the battery cell.

[0070] As an example, the value of 'a' can be 0, 0.05, 0.1, 0.15, or 0.2, or a range of any of the above values. When 'a' is 0, the second region does not include phosphorus, which can increase the theoretical specific capacity of the battery cell; when 0 < a ≤ 0.2, the diffusion rate of lithium ions can be increased, improving the lithium replenishment efficiency. By ensuring 0 ≤ a ≤ 0.2, the theoretical specific capacity of the battery cell is increased while reducing the impact on the lithium ion extraction rate.

[0071] In this application, the method for identifying the types and contents of P, Fe and M elements is as follows: the positive electrode sheet is cut along its thickness direction using plasma to obtain the cross-section of the positive electrode sheet, and the particles at different positions of the cross-section are tested using an energy dispersive spectrometer (EDS) to obtain the contents of different types of elements.

[0072] In this application, the types and contents of electrolyte additives can be tested with reference to GB / T 9722-2006 Chemical Reagents - Gas Chromatography. Specifically, a certain amount of electrolyte is tested using a gas chromatograph. By utilizing the different adsorption and desorption capacities of the various components of the electrolyte in the chromatographic column, the components of the electrolyte are separated. The separated sample is then tested using a gas chromatograph-mass spectrometer (GC-MS).

[0073]

Positive Electrode

[0074] The longest and shortest diameters of lithium iron phosphate particles or lithium supplement particles in this application are defined as follows: The positive electrode sheet, comprising lithium iron phosphate particles and lithium supplement particles, was cut along its thickness to expose a longitudinal section of the positive electrode film. Scanning electron microscopy (SEM) was used to analyze the longitudinal section of the positive electrode film to determine the longest diameter of the lithium iron phosphate particles and the shortest diameter of the lithium supplement particles. Specifically, the longest diameter of the lithium iron phosphate particles is the longest straight line passing through the center point of the lithium iron phosphate particle and extending to its outer periphery; the shortest diameter of the lithium supplement is the shortest straight line passing through the center point of the lithium supplement and extending to its outer periphery.

[0075] Reference Figure 1 , Figure 1The image shows a SEM image of a longitudinal section of a positive electrode sheet including lithium iron phosphate particles 6 and lithium replenishing agent particles 7. The image shows that the shortest diameter of the lithium replenishing agent particles 7 is greater than the longest diameter of the lithium iron phosphate particles 6 within the field of view, and the size of the lithium replenishing agent particles 7 is greater than the size of the lithium iron phosphate particles 6.

[0076] According to some embodiments of this application, the lithium iron phosphate has a unimodal particle size distribution with a particle size range of 1.5-1.7. This improves the kinetics of lithium insertion / extraction.

[0077] This application provides a method for testing the particle size distribution of lithium iron phosphate: after scraping the positive electrode sheet, the powder is dispersed with N-methylpyrrolidone (NMP), and then the particle size distribution is tested using a laser particle size analyzer (DLS).

[0078] According to some embodiments of this application, the ratio of the longest diameter to the shortest diameter of the lithium replenishing agent can be 1.2-2.5. For example, it can be 1.2, 1.5, 1.7, 2, 2.3, or 2.5, or any range of the above values. This improves the delithiation efficiency while reducing the risk of the lithium replenishing agent cracking during the rolling process.

[0079] According to some embodiments of this application, the lithium supplement includes Li x M y O z Where 1≤x≤5, 1≤y≤3, 2≤z≤8. Therefore, the decomposition of the lithium replenishment agent can compensate for the active lithium ions consumed in the formation of the SEI film, thereby improving the initial efficiency and energy density of the battery cell.

[0080] As an example, x can be 1, 2, 3, 4 or 5, or a range of any of the above values.

[0081] As an example, y can be 1, 1.5, 2, 2.5 or 3, or a range of any of the above values.

[0082] As an example, z can be 2, 3, 4, 5, 6, 7 or 8, or a range of any of the above values.

[0083] According to some embodiments of this application, the lithium replenishing agent includes one or both of Li2NiO2 and Li5FeO4. This improves the lithium replenishment effect.

[0084] According to some embodiments of this application, when all or part of the lithium in the lithium replenishing agent is extracted, the lithium replenishing agent includes Li n NiO m and Li e FeO f One or two of them, wherein 0 < m ≤ 2, 0 ≤ n ≤ 2, 0 ≤ e ≤ 5, and 0 < f ≤ 4.

[0085] As an example, m can be 0.5, 1, 1.5 or 2, or a range of any of the above values.

[0086] As an example, n can be 0, 0.5, 1, 1.5 or 2, or a range of any of the above values.

[0087] As an example, e can be 0, 1, 2, 3, 4 or 5, or a range of any of the above values.

[0088] As an example, f can be 1, 2, 3, or 4, or a range of any of the above values.

[0089] According to some embodiments of this application, when all the lithium in the lithium replenishing agent is released, the lithium replenishing agent includes NiO. m and Li p FeO q One or two of them, where 0 < m ≤ 2, 0 ≤ p ≤ 1, and 0 < q ≤ 2.

[0090] As an example, m can be 0.5, 1, 1.5 or 2, or a range of any of the above values.

[0091] As an example, p can be 0, 0.2, 0.4, 0.6, 0.8 or 1, or a range of any of the above values.

[0092] As an example, q can be 0.5, 1, 1.5 or 2, or a range of any of the above values.

[0093] According to some embodiments of this application, the compaction density of the positive electrode film layer can be 2.2 g / cm³. 3 -2.6g / cm 3 For example, it could be 2.2 g / cm³. 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 Or 2.6g / cm 3 The values ​​can be any range of the aforementioned values. This increases the energy density of the battery cell. According to some specific embodiments of this application, the compaction density of the positive electrode sheet can be 2.4 g / cm³. 3 -2.5g / cm 3 .

[0094] In this application, the compaction density of the positive electrode film is determined by measuring the mass (g / cm³) of the positive electrode film per unit area. 2The density of the positive electrode film is determined by the thickness (cm) of the positive electrode film per unit area. Specifically, the compaction density of the positive electrode film = (mass of the positive electrode sheet per unit area - mass of the positive current collector per unit area) / (thickness of the positive electrode sheet - thickness of the positive current collector).

[0095] According to some embodiments of this application, the coating weight of the positive electrode film can be 20 mg / cm³. 2 -60mg / cm 2 For example, it can be 20 mg / cm³. 2 30mg / cm 2 40mg / cm 2 50mg / cm 2 Or 60mg / cm 2 The values ​​can be any range of the aforementioned values. This increases the energy density of the battery cell. According to some specific embodiments of this application, the coating weight of the positive electrode film is 40 mg / cm³. 2 -50mg / cm 2 .

[0096] It should be noted that the coating weight of the positive electrode film referred to here refers to the coating weight of the double-sided positive electrode film on the positive electrode current collector.

[0097] In this application, the test method for the coating weight of the positive electrode film is to take a positive electrode sheet, use a fixed-size mold to punch and coat the middle area and the tab area, the mass of the positive electrode film on both sides of the positive electrode sheet in the middle area is m1, the mass of the positive electrode film on both sides of the positive electrode sheet in the tab area is m2, and the coating mass of one side of the positive electrode film is (m1-m2) / S, where S is the area of ​​the mold.

[0098] According to some embodiments of this application, based on the total mass of the positive electrode film, the mass percentage of the positive electrode active material can be 90%-98%, and the mass percentage of the lithium replenishing agent can be 0.5%-8%. This improves the lithium replenishment effect and increases the energy density of the battery cell.

[0099] As an example, the mass percentage of the positive electrode active material can be 90%, 92%, 94%, 96%, or 98%, or a range of any of the above values.

[0100] As an example, the mass percentage of the lithium replenishing agent can be 0.5%, 1%, 3%, 5%, 7% or 8%, or a range of any of the above values.

[0101] According to some embodiments of this application, at least a portion of the surface of the positive electrode active material has a first carbon coating layer. Based on the total mass of the positive electrode active material, the mass percentage of the first carbon coating layer can be 0.5%-1.5%, for example, it can be 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, or 1.5%, or any range of the above values. This improves the conductivity of the positive electrode active material.

[0102] According to some embodiments of this application, at least a portion of the surface of the lithium replenishing agent has a second carbon coating layer, and the mass percentage of the carbon coating layer is 1%-5% based on the total mass of the lithium replenishing agent. For example, it can be 1%, 2%, 3%, 4%, or 5%, or any range of the above values. Thus, the second carbon coating layer reduces the number of active sites on the surface of the lithium replenishing agent, reducing the consumption of active lithium during the formation of the SEI film, and improving the initial efficiency and energy density of the battery cell. According to some specific embodiments of this application, the mass percentage of the second carbon coating layer can be 2%-4% based on the total mass of the lithium replenishing agent.

[0103] According to some embodiments of this application, the positive electrode film layer further includes a conductive agent, which includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. This improves the conductivity of the positive electrode sheet.

[0104] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, lithium supplement, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0106] [Negative electrode plate] The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes graphite.

[0107] According to some embodiments of this application, the graphite has a graphitization degree of ≥93%, for example, it can be 93%, 94%, 95%, 96%, 97%, or 98%, or a range of any of the above values. This increases the capacity of the graphite and improves the energy density of the battery cell. According to some specific embodiments of this application, the graphitization degree of the graphite is 93%-96%.

[0108] In this application, the method for testing the degree of graphitization of graphite is as follows: scrape off the negative electrode film powder from the negative electrode sheet, perform testing using an X-ray diffractometer (XRD), and calculate the 002 interplanar spacing (d) using the Bragg equation. 002 =nλ / sinθ), degree of graphitization P=(1-(d 002 -0.3354) / (0.344-0.3354))×100%.

[0109] According to some embodiments of this application, the volume average particle size Dv50 of the graphite is 8μm-20μm, for example, it can be 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, or 20μm, or any range of the above values. Therefore, increasing the volume average particle size of the graphite reduces the specific surface area of ​​the graphite, reduces the number of active sites on the graphite surface, and reduces the consumption of active lithium during the formation of the SEI film. According to some specific embodiments of this application, the volume average particle size Dv50 of the graphite is 10μm-16μm.

[0110] In this application, Dv50 refers to the particle size corresponding to a cumulative volumetric distribution percentage of 50%, for example, measured using a laser particle size analyzer (Malvern Master Size 2000) according to standard GB / T 19077-2016 / ISO 13320:2009. The specific testing procedure is as follows: Take an appropriate amount of the sample to be tested (ensuring a light-blocking degree of 8%-12% for the sample concentration), add 20 ml of deionized water, and simultaneously sonicate for 5 minutes (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to the standard GB / T19077-2016 / ISO13320:2009.

[0111] According to some embodiments of this application, the compaction density of the negative electrode film layer can be 1.3 g / cm³. 3 -1.7g / cm 3 For example, it could be 1.3 g / cm³. 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 Or 1.7g / cm 3The values ​​can be any range of the aforementioned values. This increases the energy density of the battery cell. According to some specific embodiments of this application, the compaction density of the negative electrode film is 1.4 g / cm³. 3 -1.6g / cm 3 .

[0112] In this application, the compaction density of the negative electrode film is determined by measuring the mass (g / cm³) of the negative electrode film per unit area. 2 The density of the negative electrode film is determined by the thickness (cm) of the negative electrode film per unit area. Specifically, the compaction density of the negative electrode film is calculated as follows: (mass of the negative electrode sheet per unit area - mass of the negative current collector per unit area) / (thickness of the negative electrode sheet - thickness of the negative current collector).

[0113] According to some embodiments of this application, the coating weight of the negative electrode film is 10 mg / cm³. 2 -26mg / cm 2 For example, it can be 10 mg / cm³ 2 12mg / cm 2 14mg / cm 2 16mg / cm 2 18mg / cm 2 20mg / cm 2 22mg / cm 2 24mg / cm 2 Or 26mg / cm 2 The values ​​can be any range of the aforementioned values. This increases the energy density of the battery cell. According to some specific embodiments of this application, the coating weight of the negative electrode film is 15 mg / cm³. 2 -20mg / cm 2 .

[0114] It should be noted that the coating weight of the negative electrode film referred to here refers to the coating weight of the double-sided negative electrode film on the negative electrode current collector.

[0115] In this application, the test method for the coating weight of the negative electrode film is to take a negative electrode sheet, use a fixed-size mold to punch and coat the middle area and the tab area, the mass of the negative electrode film on both sides of the negative electrode sheet in the middle area is m1, the mass of the negative electrode film on both sides of the negative electrode sheet in the tab area is m2, and the coating mass of one side of the negative electrode film is (m1-m2) / S, where S is the mold area.

[0116] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0117] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0118] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0119] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0120] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0121]

Isolation Film

[0122] According to some embodiments of this application, the separator is disposed between the positive electrode and the negative electrode, with the ceramic layer close to the positive electrode. This reduces the probability of the base film being oxidized under high voltage conditions.

[0123] Electrolyte Typically, electrolytes consist of solvents, electrolyte salts, and additives.

[0124] According to some embodiments of this application, the molar concentration of the electrolyte salt in the electrolyte can be 1.1 mol / L to 1.5 mol / L, for example, it can be 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or 1.5 mol / L, or any range of the above values. Therefore, by increasing the concentration of the electrolyte salt in the electrolyte, concentration polarization caused by lithium ion migration can be reduced during charging and discharging, thereby increasing the lithium ion transport rate and improving the charging and discharging efficiency of the battery cell.

[0125] In this application, when measuring the molar concentration of electrolyte salts in the electrolyte, a quantitative amount of electrolyte is weighed and diluted to 1000 mL with ultrapure water, and the sample is automatically injected by ion chromatography for detection. Standard JY / T 020-1996 or GB / T 6040-2002 can be referenced.

[0126] According to some embodiments of this application, the electrolyte salt may include one or both of lithium hexafluorophosphate and lithium fluorosulfonylimide.

[0127] According to some embodiments of this application, the additive includes one or more of phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Based on the total mass of the electrolyte, the sum of the masses of the phosphorus-containing additive, the fluorine-containing additive, and the sulfur-containing additive can be 0.2%-2.1%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, or 2.1%, or a range of any of the above values.

[0128] According to some embodiments of this application, the phosphorus-containing additive includes one or more of lithium difluorophosphate (LiDFP), tris(trimethylsilane) phosphate (TMSP), triphenylphosphine oxide (TPPO), triethyl phosphate (TEP), and ethylene trifluoroethyl phosphate (TFEOP).

[0129] According to some embodiments of this application, the fluorinated additive includes one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and perfluoroalkyl ethylene carbonate.

[0130] According to some embodiments of this application, the electrolyte further includes boron-containing additives, which include one or more of tris(trimethylsilane)borate (TMSB), lithium tetrafluoroborate (LiBF4), lithium dioxalate borate (LiBOB), and lithium difluorooxalate borate (LiDFOB).

[0131] According to some embodiments of this application, the sulfur-containing additive includes one or more of vinyl sulfite (ES), propylene sulfite (PS), vinyl sulfate (DTD), 4-methylethylene sulfate (PCS), and 1,3-propenesulfonyl lactone (PST).

[0132] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the phosphorus-containing additive can be 0.01%-0.05%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04% or 0.05%, or it can be any range of the above values.

[0133] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the fluorinated additive can be 0.05%-0.5%, for example, it can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, or it can be any range of the above values.

[0134] According to some embodiments of this application, based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive can be 0.1%-2%, for example, it can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9% or 2%, or it can be any range of the above values.

[0135] Therefore, by adding the above-mentioned types and amounts of additives to the electrolyte, the above-mentioned additives have a high HOMO, and can preferentially decompose to form a dense CEI film and SEI film during the first high-voltage charge, reducing the risk of electrolyte oxidation and improving the life of the battery cell.

[0136] According to some embodiments of this application, the additive further includes carbonate additives, and the mass percentage of the carbonate additives is 2%-5% based on the total mass of the electrolyte. For example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or any range of the above values. This forms an SEI film containing polymers, improving the stability of the SEI film and increasing the lifespan of the battery cells. According to some specific embodiments of this application, the mass percentage of the cyclic carbonate additives is 3%-4%.

[0137] As an example, the carbonate additives include one or more of vinylene carbonate (VC), propylene carbonate, and vinyl ethylene carbonate.

[0138] As an example, the carbonate additives include vitamin C.

[0139] According to some embodiments of this application, the solvent includes cyclic carbonates and linear carbonates. Based on the total mass of the electrolyte, the cyclic carbonates account for 15%-25% of the mass, and the linear carbonates account for 50%-70% of the mass. This improves the stability of the electrolyte. As an example, the mass percentage of the cyclic carbonate can be 15%, 17%, 19%, 21%, 23%, or 25%, or a range of any of the above values.

[0140] As an example, the mass percentage of the linear carbonate can be 50%, 55%, 60%, 65%, or 70%, or a range of any of the above values.

[0141] According to some embodiments of this application, the cyclic carbonate includes ethylene carbonate (EC).

[0142] According to some embodiments of this application, the linear carbonate includes one or both of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0143] According to some embodiments of this application, the solvent includes one or more of EC, DMC, EMC, and diethyl carbonate (DEC).

[0144] In this application, solvent refers to a substance in the electrolyte that accounts for 10% or more by mass.

[0145] This application provides a battery device, which can be a battery module, battery pack, energy storage battery, etc.

[0146] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 The example shown is a square-structured battery cell 5.

[0147] In some implementations, refer to Figure 3 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0148] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0149] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0150] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0151] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0152] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0153] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0154] As the electrical equipment, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0155] Figure 7This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0156] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0157] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0158] Example 1 1. Positive electrode sheet The positive electrode sheet includes a positive current collector aluminum foil, with a positive electrode film layer on both surfaces. The thickness of the positive electrode film layer on one side is 97.4 μm, and the compaction density is 2.4 g / cm³. 3 The coating weight of the single-sided positive electrode film is 23.4 mg / cm³. 2 Based on the total mass of the single-sided positive electrode film, the positive electrode film includes 94.3% lithium iron phosphate material, 2.5% lithium supplementer Li5FeO4 (with Li3PO4 coating on the surface), 1% conductive agent carbon black, and 2.2% binder polyvinylidene fluoride (PVDF). The longest diameter of the lithium iron phosphate is 1.5 μm.

[0159] 2. Negative electrode plate The negative electrode sheet includes a negative current collector copper foil, with a negative electrode film layer on both surfaces. The thickness of the negative electrode film layer on one side is 53.8 μm, and the compaction density is 1.45 g / cm³. 3 The coating weight of the double-sided negative electrode film is 15.6 mg / cm³. 2 Based on the total mass of the single-sided negative electrode film, the negative electrode film includes 96.2% active material artificial graphite (94% graphitization degree), 0.8% conductive agent carbon black, 1.8% binder styrene-butadiene rubber (SBR), and 1.2% thickener sodium carboxymethyl cellulose (CMC-Na).

[0160] 3. Electrolyte The electrolyte comprises solvents, electrolyte salts, and additives. The solvents include EC, DMC, and EMC, with a mass ratio of 31.5:37.3:31.2. The electrolyte salt is LiPF6 with a molar concentration of 1.2 mol / L. Additives include phosphorus-containing additives, fluorine-containing additives, sulfur-containing additives, and carbonate additives. The phosphorus-containing additive is LiDFP, accounting for 0.039% of the total electrolyte mass. The fluorine-containing additives are FEC, LIDFOB, and LIBF4, with FEC accounting for 0.23%, LIDFOB for 0.0246%, and LIBF4 for 0.0091% of the total electrolyte mass. The sulfur-containing additive is PS, accounting for 0.54% of the total electrolyte mass. The carbonate additive is VC, accounting for 3.34% of the total electrolyte mass.

[0161] 4. Separating membrane Polyethylene film.

[0162] 5. Battery cell A single battery cell includes a positive electrode, a separator, a negative electrode, and an electrolyte.

[0163] Performance testing 1. Cyclic performance at 25℃ At 25°C, the corresponding battery is charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left to rest for 5 minutes, and then discharged to 2.5V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity C of the battery after the nth cycle is recorded. n Then, the battery capacity retention rate P after each cycle n =C n / C0 100%, thus obtaining the battery capacity retention rate.

[0164] During this test, the first loop corresponds to n=1, the second loop corresponds to n=2, ... the 1000th loop corresponds to n=1000.

[0165] 2. Energy density At 25℃, the corresponding battery is first weighed and its mass m is recorded. It is then charged to 3.65V with a constant current of 1 / 3C, and then charged to 0.05C with a constant voltage of 3.65V. After resting for 5 minutes, it is discharged to 2.5V with 1 / 3C. This cycle is repeated 3 times, and the energy recorded in the third cycle is taken as W. The energy density is W / m.

[0166] 3. Storage performance at 45℃ At 25℃, the corresponding battery was charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V. After resting for 5 minutes, it was discharged to 2.5V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0. Alternatively, the battery was charged to 3.65V at 1 / 3C and then charged to a constant voltage of 0.05C. Afterward, the battery was placed in a 45℃ constant temperature oven for 150 days and then discharged to 2.5V at room temperature. After being removed, the battery was charged to 3.65V at a constant current of 1 / 3C at 25℃, then charged to a current of 0.05C at a constant voltage of 3.65V. After resting for 5 minutes, it was discharged to 2.5V at 1 / 3C. The capacity C was recorded. n The capacity retention rate is (C n / C0) 100%.

[0167] Comparative Example 1 The negative electrode and electrolyte in the battery cell are the same as in Example 1, except that the positive electrode film does not contain lithium replenishing agent.

[0168] Comparative Example 2 The positive and negative electrode plates in the battery cell are the same as in Example 1, except that the electrolyte does not contain phosphorus-containing additives, fluorine-containing additives, or sulfur-containing additives.

[0169] Examples 2-4 The negative electrode and electrolyte in the battery cell are the same as in Example 1, except that the aspect ratio of the lithium replenishing agent is different.

[0170] Example 5 The negative electrode and electrolyte in the battery cell are the same as in Example 1, except that the type of lithium replenishing agent in the positive electrode film is different.

[0171] The differences between Examples 1-5 and Comparative Example 1 are detailed in Table 1.

[0172] Table 1

[0173] The differences between Example 1 and Comparative Example 2 are detailed in Table 2.

[0174] Table 2

[0175] As can be seen from the comparison between Examples 1-4 and Comparative Examples 1 and 2, the battery cell proposed in this application has both high energy density and high cycle capacity retention and storage capacity retention, that is, the battery cell has excellent cycle performance and storage performance while having high energy density. This application demonstrates that by setting a lithium replenishing agent on the positive electrode, the decomposition of the lithium replenishing agent during the formation stage can compensate for the lithium ions consumed in the formation of the SEI film, thereby improving the battery's energy density. The electrolyte includes phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Under high pressure conditions, these additives preferentially decompose to form stable CEI and SEI films, reducing the risk of electrolyte oxidation and decomposition, improving the stability of the electrolyte under high pressure conditions, and increasing the battery's cycle life and storage life.

[0176] As can be seen from Examples 1 and 5, adding appropriate amounts of different types of lithium supplementers can improve the energy density of battery cells. Furthermore, by adding additives with high HOMO energy levels to the electrolyte, battery cells with both high energy density and long lifespan can be obtained.

[0177] Example 6, Example 7 The positive and negative electrode plates in the battery cells are the same as in Example 1, except that the total content of additives in the electrolyte is different, as detailed in Table 3.

[0178] Table 3

[0179] As can be seen from the comparison between Examples 1, 6 and 7, by adjusting the content of additives in the electrolyte, the stability of the electrolyte under high voltage can be improved, the risk of electrolyte being decomposed by high voltage can be reduced, and the cycle life of the battery cell can be improved.

[0180] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, include: A positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer including a plurality of first regions and a plurality of second regions; The first region includes a positive electrode active material, and the first region includes iron and phosphorus elements, wherein the molar ratio of phosphorus to iron is 0.5-1.

5. The second region includes a lithium replenishing agent, which includes lithium-containing nickel-based oxides and / or lithium-containing iron-based oxides. The second region includes phosphorus and a transition metal M, which includes one or more of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn. The molar ratio of phosphorus to transition metal M is a, and satisfies 0 ≤ a ≤ 0.

2. A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode film layer located on at least one side of the negative current collector; The electrolyte includes additives, which include one or more of phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Based on the total mass of the electrolyte, the sum of the masses of the phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives accounts for 0.2%-2.1% of the total mass of the electrolyte. The electrolyte also includes a solvent, which comprises cyclic carbonates. Based on the total mass of the electrolyte, the mass percentage of the cyclic carbonates is 15%-25%, and the cyclic carbonates include ethylene carbonate.

2. The battery cell according to claim 1, characterized in that, The positive electrode active material includes lithium iron phosphate, and in a cross-sectional view along the thickness direction of the positive electrode sheet, the longest diameter of the lithium iron phosphate is smaller than the shortest diameter of the lithium replenishing agent.

3. The battery cell according to claim 1 or 2, characterized in that, The ratio of the longest diameter to the shortest diameter of the lithium replenishing agent is 1.2-2.

5.

4. The battery cell according to any one of claims 1-3, characterized in that, The lithium supplement includes Li x M y O z , where 1≤x≤5, 1≤y≤3, 2≤z≤8.

5. The battery cell according to any one of claims 1-3, characterized in that, The lithium supplement includes one or both of Li2NiO2 and Li5FeO4.

6. The battery cell according to any one of claims 1-3, characterized in that, The lithium supplement includes Li n NiO m and Li e FeO f One or two of them, wherein 0 < m ≤ 2, 0 ≤ n ≤ 2, 0 ≤ e ≤ 5, and 0 < f ≤ 4.

7. The battery cell according to any one of claims 1-3, characterized in that, The lithium supplement includes NiO. m and Li p FeO q One or two of them, where 0 < m ≤ 2, 0 ≤ p ≤ 1, and 0 < q ≤ 2.

8. The battery cell according to any one of claims 1-7, characterized in that, The electrolyte also includes an electrolyte salt, and the molar concentration of the electrolyte salt in the electrolyte is 1.1 mol / L to 1.5 mol / L.

9. The battery cell according to claim 8, characterized in that, The electrolyte salt includes one or both of lithium hexafluorophosphate and lithium fluorosulfonylimide.

10. The battery cell according to any one of claims 1-9, characterized in that, The negative electrode film layer includes a negative electrode active material, which includes graphite.

11. The battery cell according to any one of claims 1-10, characterized in that, The compaction density of the positive electrode film is 2.2 g / cm³. 3 -2.6g / cm 3 2.4g / cm³ is an optional value. 3 -2.5g / cm 3 .

12. The battery cell according to any one of claims 1-11, characterized in that, The coating weight of the positive electrode film is 20 mg / cm³. 2 -60mg / cm 2 40mg / cm 2 -50mg / cm 2 .

13. The battery cell according to any one of claims 10-12, characterized in that, The graphite has a graphitization degree of 93%-97%, and can be selected as 93%-96%.

14. The battery cell according to any one of claims 10-13, characterized in that, The volume average particle size Dv50 of the graphite is 8μm-20μm, and can be selected as 10μm-16μm.

15. The battery cell according to any one of claims 1-14, characterized in that, The compaction density of the negative electrode film is 1.3 g / cm³. 3 -1.7g / cm 3 1.4g / cm³ is an optional value. 3 -1.6g / cm 3 .

16. The battery cell according to any one of claims 1-15, characterized in that, The coating weight of the negative electrode film is 10 mg / cm³. 2 -26mg / cm 2 15mg / cm 2 -20mg / cm 2 .

17. The battery cell according to any one of claims 1-16, characterized in that, The solvent also includes linear carbonate, which accounts for 50%-70% of the total mass of the electrolyte.

18. The battery cell according to claim 16, characterized in that, The linear carbonate includes one or both of dimethyl carbonate and ethyl methyl carbonate.

19. The battery cell according to any one of claims 1-18, characterized in that, The additives also include carbonate additives, which include one or more of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate.

20. The battery cell according to claim 19, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the carbonate additive is 2%-5%, optionally 3%-4%.

21. The battery cell according to any one of claims 1-20, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the phosphorus-containing additive is 0.01%-0.05%.

22. The battery cell according to any one of claims 1-21, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the fluorinated additive is 0.05%-0.5%.

23. The battery cell according to any one of claims 1-22, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the sulfur-containing additive is 0.1%-2%.

24. The battery cell according to any one of claims 1-23, characterized in that, The phosphorus-containing additives include one or more of lithium difluorophosphate, tris(trimethylsilane) phosphate, triphenylphosphine oxide, triethyl phosphate, trimethylolpropane, and trifluoroethyl ethylene phosphate.

25. The battery cell according to any one of claims 1-24, characterized in that, The fluorinated additives include one or more of the following: fluoroethylene carbonate, difluoroethylene carbonate, perfluoroalkyl ethylene carbonate, tris(trimethylsilane)borate, lithium tetrafluoroborate, lithium dioxalate borate, and lithium difluorooxalate borate.

26. The battery cell according to any one of claims 1-25, characterized in that, The sulfur-containing additives include one or more of vinyl sulfite, propylene sulfite, vinyl sulfate, 4-methylethylene sulfate, and 1,3-propenesulfonyl lactone.

27. The battery cell according to any one of claims 2-26, characterized in that, The lithium iron phosphate has a single-peaked particle size distribution with a particle size distribution range of 1.5-1.

7.

28. The battery cell according to any one of claims 1-27, characterized in that, Based on the total mass of the positive electrode film, the positive electrode active material accounts for 90%-98% of the mass, and the lithium supplement agent accounts for 0.5%-8% of the mass.

29. The battery cell according to any one of claims 1-28, characterized in that, At least a portion of the surface of the positive electrode active material has a first carbon coating layer, and the mass percentage of the first carbon coating layer is 0.5%-1.5% based on the total mass of the positive electrode active material.

30. The battery cell according to any one of claims 1-29, characterized in that, At least a portion of the surface of the lithium replenishing agent has a second carbon coating layer, and the mass percentage of the second carbon coating layer is 1%-5%, optionally 2%-4%, based on the total mass of the lithium replenishing agent.

31. The battery cell according to any one of claims 1-30, characterized in that, The positive electrode film layer also includes a conductive agent, which includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

32. The battery cell according to any one of claims 1-31, characterized in that, The battery cell further includes: a separator, the separator comprising: Base film, wherein the material of the base film includes polyethylene; An adhesive layer, said adhesive layer being located on at least one side of the base film; A ceramic layer, the ceramic layer being located on the side of the adhesive layer away from the base film.

33. The battery cell according to claim 32, characterized in that, The separator is disposed between the positive electrode and the negative electrode, and the ceramic layer is close to the positive electrode.

34. The battery cell according to any one of claims 1-33, characterized in that, The volumetric energy density of the battery cell is greater than or equal to 410Wh / L.

35. The battery cell according to any one of claims 1-34, characterized in that, The volumetric energy density of the battery cell is greater than or equal to 420Wh / L.

36. A battery device, characterized in that, Includes the battery cell according to any one of claims 1-35.

37. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 1-35, said battery cell being used to provide electrical energy.

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