Battery monomer, battery device and electric equipment

Abstract

The invention discloses a battery monomer, a battery device and electric equipment, the battery monomer comprises a positive pole piece, the positive pole piece comprises a positive pole film layer, a positive pole film layer first area and a positive pole film layer second area, the first area comprises an iron element and a phosphorus element, and the molar ratio of the phosphorus element to the iron element is 0.5-1.5; the second area comprises the phosphorus element and a transition metal M, the molar ratio of the phosphorus element to the transition metal M is a, and a is larger than or equal to 0 and smaller than or equal to 0.2; a negative pole piece; 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 based on the total mass of the electrolyte, the mass sum of the phosphorus-containing additive, the fluorine-containing additive and the sulfur-containing additive accounts for 0.2%-2.1%. Therefore, the cycle life and the energy density of the battery are improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular, to battery cells, battery devices and electrical equipment. Background Art

[0002] Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. The use time of long-term energy storage products is generally greater than 20 years, and the battery life is required to be high. The lithium supplement in the positive electrode can improve the battery life to a certain extent, but the improvement in life is limited, and the battery energy density is low, which is difficult to meet the needs of lightweight and miniaturization. Since the lithium supplement needs to be decomposed under high pressure conditions, there is also the problem of incompatibility between the electrolyte and the positive and negative electrodes under high pressure conditions. Summary of the invention

[0003] The first aspect of the present application provides a battery cell, the battery cell comprising a positive electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer having a plurality of first regions and a plurality of second regions; the first region comprising a positive electrode active material, the first region comprising an iron element and a phosphorus element, the molar ratio of the phosphorus element to the iron element being 0.5-1.5; the second region comprising a lithium supplement, the second region comprising the phosphorus element and a transition metal M, the transition metal M comprising Ni element, Co element, V element, Cr element, M n element, Fe element, Mo element, Cu element, Zn element or more, the molar ratio of the phosphorus element to the transition metal M is a, and satisfies 0≤a≤0.2; negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector; electrolyte, the electrolyte includes additives, the additives 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 mass of the phosphorus-containing additives, the fluorine-containing additives, and the sulfur-containing additives accounts for 0.2%-2.1%. Thus, the capacity and structural stability of the positive electrode active material are improved, the stability of the electrolyte under high voltage conditions is improved, and the capacity and cycle life of the battery are improved.

[0004] According to some embodiments of the present application, the positive electrode active material includes lithium iron phosphate, and the longest diameter of the lithium iron phosphate is smaller than the shortest diameter of the lithium supplement, thereby improving the kinetics of lithium insertion and extraction of the positive electrode active material and reducing the side reaction between the lithium supplement and the electrolyte.

[0005] According to some embodiments of the present application, the ratio of the longest diameter of the lithium supplement agent to the shortest diameter of the lithium supplement agent is 1.2-2.5, thereby improving the lithium removal efficiency and reducing the risk of the lithium supplement agent being fractured during the rolling process.

[0006] According to some embodiments of the present application, the lithium supplement comprises Li x M y O z , wherein 1≤x≤5, 1≤y≤3, 2≤z≤8. Thus, the lithium supplement effect is improved and the initial efficiency of the battery cell is improved.

[0007] According to some embodiments of the present application, the lithium supplement includes one or two of Li2NiO2 and Li5FeO4.

[0008] According to some embodiments of the present application, the lithium supplement comprises Li n NiO m and Li e FeO f One or two of the following, wherein 0<m≤2, 0≤n≤2, 0≤e≤5, 0<f≤4.

[0009] According to some embodiments of the present application, the lithium supplement comprises NiO m and Li p FeO q One or two of the following, where 0<m≤2, 0≤p≤1, 0<q≤2.

[0010] Therefore, the decomposition of the lithium supplement can make up for the active lithium ions consumed in forming SEI, thereby improving the initial efficiency and energy density of the battery cell.

[0011] According to some embodiments of the present 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. Thus, the concentration polarization caused by the migration of lithium ions can be reduced during the charge and discharge process, the influence of concentration polarization on the lithium ion transmission rate can be reduced, the internal resistance of the battery cell can be reduced, and the charge and discharge efficiency of the battery cell can be improved.

[0012] According to some embodiments of the present application, the electrolyte salt includes one or both of lithium hexafluorophosphate and fluorinated lithium sulfonyl imide, thereby improving the conductivity of the battery cell.

[0013] According to some embodiments of the present application, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite, thereby reducing the cost of the battery cell and improving the energy density and cycle life of the battery cell.

[0014] According to some embodiments of the present application, the compaction density of the positive electrode film layer is 2.2 g / cm3 -2.6g / cm 3 , optional 2.4g / cm 3 -2.5g / cm 3 . Thus, the energy density of the battery cell is increased.

[0015] According to some embodiments of the present application, the coating weight of the positive electrode film layer is 20 mg / cm 2 -60mg / cm 2 , optional 40mg / cm 2 -50mg / cm 2 . Thus, the energy density of the battery cell is increased.

[0016] According to some embodiments of the present application, the graphitization degree of the graphite is 93%-97%, and can be optionally 93%-96%, thereby increasing the capacity of the graphite and the energy density of the battery cell.

[0017] According to some embodiments of the present application, the volume average particle size Dv50 of the graphite is 8 μm-20 μm, and can be 10 μm-16 μm, thereby reducing the number of active sites of the graphite, reducing the Li consumption in forming the SEI film, and improving the cycle life of the battery cell.

[0018] According to some embodiments of the present application, the compaction density of the negative electrode film layer is 1.3 g / cm 3 -1.7g / cm 3 , optional 1.4g / cm 3 -1.6g / cm 3 . Thus, the energy density of the battery cell is increased.

[0019] According to some embodiments of the present application, the coating weight of the negative electrode film layer is 10 mg / cm 2 -26mg / cm 2 , optional 15mg / cm 2 -20mg / cm 2 . Thus, the energy density of the battery cell is increased.

[0020] According to some embodiments of the present application, the electrolyte further comprises a solvent, the solvent comprises a cyclic carbonate and a linear carbonate, and based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate is 15%-25%, and the mass proportion of the linear carbonate is 50%-70%. Thus, the stability of the electrolyte is improved and the life of the battery is increased.

[0021] According to some embodiments of the present application, the cyclic carbonate includes ethylene carbonate.

[0022] According to some embodiments of the present application, the linear carbonate includes one or both of dimethyl carbonate and ethyl methyl carbonate.

[0023] According to some embodiments of the present application, the additive further comprises a carbonate additive, and the carbonate additive comprises one or more of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate. Thus, a SEI film containing a polymer is formed, the stability of the SEI film is improved, and the life of the battery is increased.

[0024] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 2%-5%, and optionally 3%-4%. Thus, a SEI film containing a polymer is formed, the stability of the SEI film is improved, and the life of the battery is increased.

[0025] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the phosphorus-containing additive is 0.01%-0.05%.

[0026] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorine-containing additive is 0.05%-0.5%.

[0027] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the sulfur-containing additive is 0.1%-2%.

[0028] Therefore, by making the contents of the phosphorus-containing additive, the fluorine-containing additive and the sulfur-containing additive within the above range, a dense solid electrolyte membrane (CEI membrane) can be formed at the positive electrode during the first charge process, reducing the probability of oxidation of the electrolyte.

[0029] According to some embodiments of the present application, the phosphorus-containing additive includes one or more of lithium difluorophosphate, tris(trimethylsilyl)phosphate, triphenylphosphine oxide, triethyl phosphate, and trifluoroethyl ethylene phosphate.

[0030] According to some embodiments of the present application, the fluorine-containing additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, perfluoroalkylethylene carbonate, lithium tetrafluoroborate, and lithium difluorooxalatoborate.

[0031] According to some embodiments of the present application, the sulfur-containing additive includes one or more of vinyl sulfite, propylene sulfite, vinyl sulfate, 4-methylethylene sulfate, and 1,3-propylene sultone.

[0032] As a result, a dense solid electrolyte interface film (CEI film) can be formed at the positive electrode during the first charging process, reducing the probability of the electrolyte being oxidized.

[0033] According to some embodiments of the present application, the particle size distribution of the lithium iron phosphate is unimodal, and the particle size distribution span value is 1.5-1.7, thereby improving the kinetics of lithium insertion and extraction.

[0034] According to some embodiments of the present application, based on the total mass of the positive electrode film layer, the mass proportion of the positive electrode active material is 90%-98%, and the mass proportion of the lithium supplement agent can be 0.5%-8%, thereby improving the energy density and cycle life of the battery.

[0035] According to some embodiments of the present application, at least part of the surface of the positive electrode active material has a first carbon coating layer, and based on the total mass of the positive electrode active material, the mass proportion of the first carbon coating layer is 0.5%-1.5%, thereby improving the electronic conductivity of the positive electrode sheet.

[0036] According to some embodiments of the present application, at least part of the surface of the lithium supplement agent has a second carbon coating layer, and based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer is 1%-5%, and optionally 2%-4%. , reducing the number of active sites exposed on the surface of the lithium supplement agent and reducing the side reactions between the lithium supplement agent and the electrolyte.

[0037] According to some embodiments of the present application, the positive electrode film layer further includes a conductive agent, and the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, thereby improving the conductivity of the positive electrode sheet.

[0038] According to some embodiments of the present application, the battery cell further comprises: a separator, the separator comprising: a base film, the material of the base film comprising polyethylene; a bonding layer, the bonding layer being located on at least one side of the base film; and a ceramic layer, the ceramic layer being located on a side of the bonding layer away from the base film. Thus, the oxidation resistance of the separator is improved.

[0039] According to some embodiments of the present application, the separator is disposed between the positive electrode sheet and the negative electrode sheet, and the ceramic layer is close to the positive electrode sheet, thereby improving the oxidation resistance of the separator.

[0040] According to some embodiments of the present application, the volume energy density of the battery cell is greater than or equal to 410Wh / L.

[0041] According to some embodiments of the present application, the volume energy density of the battery cell is greater than or equal to 420Wh / L.

[0042] A second aspect of the present application provides a battery device, comprising the battery cell provided in the first aspect of the present application.

[0043] A third aspect of the present application provides an electrical device, comprising the battery cell provided by the first aspect of the present application, wherein the battery cell is used to provide electrical energy.

[0044] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0046] Figure 1 This is a SEM image of the longitudinal section of the positive electrode sheet in Example 1 of the present application.

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

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

[0049] Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0050] Figure 5 It is a schematic diagram of a battery pack according to one embodiment of the present application.

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

[0052] Figure 7 It is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0053] Description of reference numerals:

[0054] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 cover plate; 6 lithium iron phosphate particles; 7 lithium supplement particles. DETAILED DESCRIPTION

[0055] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0056] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0057] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0058] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0059] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0060] At present, judging from the development of the market situation, batteries are being used more and more widely. They can be used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations. However, the energy storage batteries in related technologies cannot meet the requirements of long life and high safety at the same time.

[0061] The present application aims to develop a battery cell with both high energy density and long life. The battery cell of the present 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, and the relative contents of phosphorus and transition metal M in the lithium supplement region, and matching a suitable electrolyte formula, to develop a battery cell with high energy density and long life.

[0062] The molar ratio of phosphorus to iron in the lithium iron phosphate region of the positive electrode of the present application is 0.5-1.5. On the one hand, the proportion of lithium phosphate impurities contained in lithium iron phosphate is reduced to increase the capacity of the battery cell; on the other hand, the content of phosphate is increased, the structural stability of the positive electrode active material is improved, and the cycle life of the battery cell is improved. In order to further improve the cycle life and energy density of the battery, a lithium supplement is introduced into the positive electrode, and the cycle life and energy density of the battery cell are improved by controlling the relative content of phosphorus and transition metal M elements. However, after the lithium supplement is introduced into the positive electrode, the formation voltage required for the lithium supplement to take effect is high, so it is easy to cause the electrolyte additive to decompose prematurely and cannot continue to act on the later long cycle process. Therefore, in order to reduce the probability of electrolyte decomposition caused by the high voltage in the formation stage, the present application introduces phosphorus-containing additives, fluorine-containing additives, sulfur-containing additives and other additives into the electrolyte, and takes advantage of the higher HOMO energy level of the additives to improve the stability of the electrolyte at high voltage, reduce the risk of electrolyte redox decomposition, and improve the cycle life of the battery. In addition, the elements contained in the lithium supplement material can also participate in the formation of SEI film components, optimize the SEI film impedance, and benefit the battery cycle performance.

[0063] The battery cell proposed in this application can be used in electrical equipment that uses the battery cell as a power source or various energy storage systems that use the battery cell as an energy storage element. Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0064] A first aspect of the present application provides a battery cell, which includes a positive electrode sheet, a negative electrode sheet and an electrolyte.

[0065] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer includes a plurality of first regions and a plurality of second regions; the first region includes a positive electrode active material, the first region includes iron element and phosphorus element, and the molar ratio of the phosphorus element to the iron element is 0.5-1.5; the second region includes a lithium supplement, the second region includes the phosphorus element and a transition metal M, the transition metal M includes one or more of Ni element, Co element, V element, Cr element, Mn element, Fe element, Mo element, Cu element, and Zn element, the molar ratio of the phosphorus element to the transition metal M is a, and satisfies 0≤a≤0.2.

[0066] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector.

[0067] The electrolyte includes additives, and the additives 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%.

[0068] Thus, while reducing the probability of generating lithium phosphate and increasing the capacity of the battery cell, the content of phosphate is increased, the structural stability of the positive electrode active material is improved, and the cycle life of the battery cell is improved. By setting a lithium supplement on the positive electrode plate, the decomposition of the lithium supplement in the formation stage can make up for the lithium ions consumed in forming the SEI film, thereby improving the initial efficiency and energy density of the battery. In order to reduce the probability of electrolyte decomposition caused by high pressure in the formation stage, the electrolyte includes one or more of phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Under high pressure conditions, the above-mentioned types of additives can preferentially decompose to form stable CEI films and SEI films, reduce the contact between the electrolyte and the positive and negative electrode surfaces, reduce the risk of oxidative decomposition of the electrolyte, improve the stability of the electrolyte under high pressure conditions, and improve the cycle life of the battery.

[0069] In the present application, the area where the positive electrode active material is located is the first area, and the area where the lithium supplement is located is the second area, and the first area and the second area are evenly distributed on the positive electrode plate. Since the particle size and P element content of the positive electrode active material and the lithium supplement are significantly different: the average particle size of the positive electrode active material is about 1μm, and the longest diameter of a single particle of the lithium supplement is greater than 5μm; the P element content in the positive electrode active material is greater than 20%, and the P element content in the lithium supplement is less than 0.5%. Therefore, the first area and the second area can be distinguished by combining the particle size and the P element content. Specifically, the first area where the positive electrode active material is located has a smaller average particle size and a higher P element content, and the second area where the lithium supplement is located has a larger longest diameter and a lower P element content.

[0070] As an example, the molar ratio of the phosphorus element to the iron element in the first region may be 0.5, 0.7, 0.9, 1.1, 1.3 or 1.5, or may be a range of any of the above values. By making the molar ratio of the phosphorus element to the iron element within the above range, on the one hand, the risk of generating lithium phosphate due to excessive phosphorus content, thereby reducing the capacity of the battery cell, is reduced; on the other hand, the risk of low phosphate content due to low phosphorus content is reduced, the structural stability of the positive electrode active material is improved, and the cycle life of the battery cell is improved.

[0071] As an example, the value of a can be 0, 0.05, 0.1, 0.15 or 0.2, etc., or can be 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, and the lithium replenishment efficiency can be improved. By setting 0≤a≤0.2, while increasing the theoretical specific capacity of the battery cell, the impact on the release rate of lithium ions is reduced.

[0072] In the present application, the method for identifying the types and contents of P element, Fe element and M element is: using plasma to cut the positive electrode sheet along its thickness direction to obtain the cross-section of the positive electrode sheet, and using an energy dispersive spectrometer (EDS) to test the particles at different positions of the cross-section to obtain the contents of different types of elements.

[0073] In the present application, the type and content of electrolyte additives can be tested with reference to GB / T 9722-2006 Chemical Reagent Gas Chromatography. Specifically, a certain amount of electrolyte is tested using a gas chromatograph, and the different adsorption and desorption capacities of the components of the electrolyte in the chromatographic column are utilized to separate the components of the electrolyte, and the separated samples are tested using a gas chromatograph-mass spectrometer (GC-MS).

[0074]

Positive electrode

[0075] According to some embodiments of the present application, the positive electrode active material includes lithium iron phosphate, and the longest diameter of the lithium iron phosphate is smaller than the shortest diameter of the lithium supplement. Thus, by reducing the particle size of lithium iron phosphate and increasing the particle size of the lithium supplement, the efficiency of lithium extraction and extraction of the positive electrode active material is improved, the specific surface area of ​​the lithium supplement is reduced, the contact between the lithium supplement and the electrolyte is reduced, the side reaction between the lithium supplement and the electrolyte is reduced, the stability of the electrolyte is improved, and the life of the battery cell is improved.

[0076] The longest diameter and shortest diameter of the lithium iron phosphate particles or lithium supplement particles of the present application are defined as follows:

[0077] The positive electrode sheet including lithium iron phosphate particles and lithium supplement particles is cut along the thickness direction of the sheet to expose the longitudinal section of the positive electrode film layer. The longest diameter of the lithium iron phosphate particles and the shortest diameter of the lithium supplement particles are determined by scanning electron microscopy (SEM) testing of the longitudinal section of the positive electrode film layer. Specifically, the longest diameter of the lithium iron phosphate particles refers to the longest straight line passing through the center point of the lithium iron phosphate particles and extending to the periphery of the particles, and the shortest diameter of the lithium supplement refers to the shortest straight line passing through the center point of the lithium supplement and extending to the periphery of the lithium supplement.

[0078] Reference Figure 1 , Figure 1This is a SEM image of a longitudinal section of a positive electrode sheet including lithium iron phosphate particles 6 and lithium supplement particles 7. The image shows that the shortest diameter of the lithium supplement particle 7 is larger than the longest diameter of the lithium iron phosphate particle 6 within the field of view, and the size of the lithium supplement particle 7 is larger than the size of the lithium iron phosphate particle 6.

[0079] According to some embodiments of the present application, the particle size distribution of the lithium iron phosphate is unimodal, and the particle size distribution span value is 1.5-1.7, thereby improving the kinetics of lithium insertion and extraction.

[0080] The present application provides a method for testing the particle size distribution of lithium iron phosphate: after taking the positive electrode sheet and scraping the powder, the powder is dispersed with N-methylpyrrolidone (NMP), and then the particle size distribution is tested with a laser particle size analyzer (DLS).

[0081] According to some embodiments of the present application, the ratio of the longest diameter of the lithium supplement agent to the shortest diameter of the lithium supplement 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 can be a range composed of any of the above values. In this way, the lithium removal efficiency is improved, and at the same time, the risk of the lithium supplement agent being fractured during the rolling process is reduced.

[0082] According to some embodiments of the present application, the lithium supplement comprises Li x M y O z , where 1≤x≤5, 1≤y≤3, 2≤z≤8. Therefore, the decomposition of the lithium supplement can make up for the active lithium ions consumed in forming the SEI film, thereby improving the initial efficiency and energy density of the battery cell.

[0083] As an example, x may be 1, 2, 3, 4 or 5, etc., or may be a range consisting of any of the above values.

[0084] As an example, y may be 1, 1.5, 2, 2.5 or 3, etc., or may be a range consisting of any of the above values.

[0085] As an example, z may be 2, 3, 4, 5, 6, 7 or 8, etc., or may be a range consisting of any of the above values.

[0086] According to some embodiments of the present application, the lithium supplement agent includes one or both of Li2NiO2 and Li5FeO4, thereby improving the lithium supplement effect.

[0087] According to some embodiments of the present application, when the lithium in the lithium supplement is completely or partially removed, the lithium supplement includes Li n NiO m and Li e FeO f One or two of the following, wherein 0<m≤2, 0≤n≤2, 0≤e≤5, 0<f≤4.

[0088] As an example, m may be 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0089] As an example, n may be 0, 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0090] As an example, e can be 0, 1, 2, 3, 4 or 5, etc., or can be a range consisting of any of the above values.

[0091] As an example, f may be 1, 2, 3 or 4, etc., or may be a range consisting of any of the above values.

[0092] According to some embodiments of the present application, when all lithium in the lithium supplement is removed, the lithium supplement includes NiO m and Li p FeO q One or two of the following, where 0<m≤2, 0≤p≤1, 0<q≤2.

[0093] As an example, m may be 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0094] As an example, p may be 0, 0.2, 0.4, 0.6, 0.8 or 1, etc., or may be a range consisting of any of the above values.

[0095] As an example, q may be 0.5, 1, 1.5 or 2, etc., or may be a range consisting of any of the above values.

[0096] According to some embodiments of the present application, the compaction density of the positive electrode film layer can be 2.2 g / cm 3 -2.6g / cm 3 , for example, can be 2.2 g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 or 2.6g / cm 3 etc., or can be any range of the above values. Thus, the energy density of the battery cell is improved. According to some specific embodiments of the present application, the compaction density of the positive electrode sheet can be 2.4 g / cm 3 -2.5g / cm 3 .

[0097] In this application, the compaction density of the positive electrode film layer is measured by measuring the mass of the positive electrode film layer per unit area (g / cm 2) and the thickness (cm) of the positive electrode film layer per unit area. Specifically, the compaction density of the positive electrode film layer = (the mass of the positive electrode sheet per unit area - the mass of the positive electrode current collector per unit area) / ( / the thickness of the positive electrode sheet - the thickness of the positive electrode current collector).

[0098] According to some embodiments of the present application, the coating weight of the positive electrode film layer can be 20 mg / cm 2 -60mg / cm 2 , for example, it can be 20 mg / cm 2 、30mg / cm 2 , 40mg / cm 2 、50mg / cm 2 or 60mg / cm 2 etc., or can be any range of the above values. Thus, the energy density of the battery cell is increased. According to some specific embodiments of the present application, the coating weight of the positive electrode film layer is 40 mg / cm 2 -50mg / cm 2 .

[0099] It should be noted that the coating weight of the positive electrode film layer referred to here refers to the coating weight of the double-sided positive electrode film layer on the positive electrode current collector.

[0100] In the present application, the testing method for the coating weight of the positive electrode film layer is to take the positive electrode sheet, use a fixed-size mold to punch and coat the middle area and the lug area, the mass of the positive electrode film layer on both sides of the positive electrode sheet in the middle area is m1, the mass of the positive electrode film layer on both sides of the positive electrode sheet in the lug area is m2, and the coating mass of one side of the positive electrode film layer = (m1-m2) / S, where S is the mold area.

[0101] According to some embodiments of the present application, based on the total mass of the positive electrode film layer, the mass proportion of the positive electrode active material can be 90%-98%, and the mass proportion of the lithium supplement can be 0.5%-8%, thereby improving the lithium supplement effect and the energy density of the battery cell.

[0102] As an example, the mass percentage of the positive electrode active material may be 90%, 92%, 94%, 96% or 98%, etc., or may be a range consisting of any of the above values.

[0103] As an example, the mass proportion of the lithium supplement may be 0.5%, 1%, 3%, 5%, 7% or 8%, etc., or may be a range consisting of any of the above values.

[0104] According to some embodiments of the present application, at least part of the surface of the positive electrode active material has a first carbon coating layer, and based on the total mass of the positive electrode active material, the mass proportion of the first carbon coating layer can be 0.5%-1.5%, for example, 0.5%, 0.7%, 0.9%, 1.1%, 1.3% or 1.5%, etc., or can be a range composed of any of the above values. Thus, the conductivity of the positive electrode active material is improved.

[0105] According to some embodiments of the present application, at least part of the surface of the lithium supplement agent has a second carbon coating layer, and based on the total mass of the lithium supplement agent, the mass proportion of the carbon coating layer is 1%-5%. For example, it can be 1%, 2%, 3%, 4% or 5%, etc., or it can be a range composed of any of the above numerical values. Thus, the number of active sites on the surface of the lithium supplement agent is reduced by the second carbon coating layer, the consumption of active lithium is reduced in the process of forming the SEI film, and the first efficiency and energy density of the battery cell are improved. According to some specific embodiments of the present application, based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer can be 2%-4%.

[0106] According to some embodiments of the present application, the positive electrode film layer further includes a conductive agent, and the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, thereby improving the conductivity of the positive electrode sheet.

[0107] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0108] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the lithium supplement, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0109]

Negative electrode

[0110] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite.

[0111] According to some embodiments of the present application, the graphitization degree of the graphite is ≥ 93%, for example, it can be 93%, 94%, 95%, 96%, 97% or 98%, etc., or it can be a range composed of any of the above values. Thereby, the capacity of the graphite is increased and the energy density of the battery cell is increased. According to some specific embodiments of the present application, the graphitization degree of the graphite is 93%-96%.

[0112] In the present application, the test method for the graphitization degree of graphite is: scrape off the negative electrode film powder on the negative electrode plate, test it using an X-ray diffractometer (XRD), and calculate the 002 crystal plane spacing (d 002 =nλ / sinθ), graphitization degree P = (1-(d 002 -0.3354) / (0.344-0.3354))×100%.

[0113] According to some embodiments of the present 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 it can be a range composed of any of the above numerical values. Thus, the volume average particle size of the graphite is increased, the specific surface area of ​​the graphite is reduced, the number of active sites on the graphite surface is reduced, and the consumption of active lithium is reduced during the formation of the SEI film. According to some specific embodiments of the present application, the volume average particle size Dv50 of the graphite is 10μm-16μm.

[0114] In this application, Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage reaching 50%, for example, with reference to the standard GB / T 19077-2016 / ISO 13320:2009, using a laser particle size analyzer (Malvern Master Size 2000) for measurement. The specific test process is: take an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8%-12% shading), add 20ml of deionized water, and ultrasonicate for 5min (53KHz / 120W) to ensure that the sample is completely dispersed, and then measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0115] According to some embodiments of the present application, the compaction density of the negative electrode film layer can be 1.3 g / cm 3 -1.7g / cm 3 , for example, can be 1.3 g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 or 1.7 g / cm3 etc., or can be any range of the above values. Thus, the energy density of the battery cell is improved. According to some specific embodiments of the present application, the compaction density of the negative electrode film layer is 1.4 g / cm 3 -1.6g / cm 3 .

[0116] In this application, the compaction density of the negative electrode film layer is measured by measuring the mass of the negative electrode film layer per unit area (g / cm 2 ) and the thickness of the negative electrode film layer per unit area (cm). Specifically, the compaction density of the negative electrode film layer = (the mass of the negative electrode sheet per unit area - the mass of the negative electrode current collector per unit area) / ( / the thickness of the negative electrode sheet - the thickness of the negative electrode current collector).

[0117] According to some embodiments of the present application, the coating weight of the negative electrode film layer is 10 mg / cm 2 -26mg / cm 2 , for example, can be 10 mg / cm 2 , 12mg / cm 2 、14mg / cm 2 、16mg / cm 2 、18mg / cm 2 , 20mg / cm 2 , 22mg / cm 2 , 24mg / cm 2 or 26 mg / cm 2 etc., or can be any range of the above values. Thus, the energy density of the battery cell is improved. According to some specific embodiments of the present application, the coating weight of the negative electrode film layer is 15 mg / cm 2 -20mg / cm 2 .

[0118] It should be noted that the coating weight of the negative electrode film layer referred to here refers to the coating weight of the double-sided negative electrode film layer on the negative electrode current collector.

[0119] In the present application, the testing method for the coating weight of the negative electrode film layer 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 layer on both sides of the negative electrode sheet in the middle area is m1, and the mass of the negative electrode film layer on both sides of the negative electrode sheet in the tab area is m2, and the coating mass of a single side of the negative electrode film layer = (m1-m2) / S, where S is the mold area.

[0120] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0121] In some embodiments, the negative electrode film layer may further include a binder. The binder 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).

[0122] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0123] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0124] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0125]

Isolation film

[0126] According to some embodiments of the present application, the isolation membrane includes: a base membrane, the material of the base membrane includes polyethylene; an adhesive layer, the adhesive layer is located on at least one side of the base membrane; and a ceramic layer, the ceramic layer is located on the side of the adhesive layer away from the base membrane. Thus, the adhesive layer can reduce the probability of wrinkles on the base membrane, and the ceramic layer can reduce the risk of puncture of the isolation membrane, thereby improving the safety of the battery cell.

[0127] According to some embodiments of the present application, the isolation film is disposed between the positive electrode sheet and the negative electrode sheet, and the ceramic layer is close to the positive electrode sheet, thereby reducing the probability of oxidation of the base film under high pressure conditions.

[0128]

Electrolyte

[0129] Typically, the electrolyte includes a solvent, an electrolyte salt, and additives.

[0130] According to some embodiments of the present application, the molar concentration of the electrolyte salt in the electrolyte may be 1.1 mol / L-1.5 mol / L, for example, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, or may be a range of any of the above values. Thus, by increasing the concentration of the electrolyte salt in the electrolyte, the concentration polarization caused by the migration of lithium ions can be reduced during the charge and discharge process, the transfer rate of lithium ions can be increased, and the charge and discharge efficiency of the battery cell can be improved.

[0131] In the present application, when measuring the molar concentration of the electrolyte salt in the electrolyte, a quantitative electrolyte is weighed and fixed to 1000 mL with ultrapure water, and the ion chromatography is automatically sampled for detection, and reference may be made to the standard JY / T 020-1996 or GB / T 6040-2002.

[0132] According to some embodiments of the present application, the electrolyte salt may include one or both of lithium hexafluorophosphate and fluorinated lithium sulfonyl imide.

[0133] According to some embodiments of the present application, the additive includes one or more of a phosphorus-containing additive, a fluorine-containing additive, and a sulfur-containing additive. 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 may account for 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%, etc., or may be a range consisting of any of the above numerical values.

[0134] According to some embodiments of the present application, the phosphorus-containing additive includes one or more of lithium difluorophosphate (LiDFP), tris(trimethylsilyl) phosphate (TMSP), triphenylphosphine oxide (TPPO), triethyl phosphate (TEP), and trifluoroethyl ethylene phosphate (TFEOP).

[0135] According to some embodiments of the present application, the fluorine-containing additive includes one or more of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), and perfluoroalkylethylene carbonate.

[0136] According to some embodiments of the present application, the electrolyte further includes a boron-containing additive, and the boron-containing additive includes one or more of tris(trimethylsilyl)borate (TMSB), lithium tetrafluoroborate (LiBF4), lithium dioxalatoborate (LiBOB), and lithium difluorooxalatoborate (LiDFOB).

[0137] According to some embodiments of the present application, the sulfur-containing additive includes one or more of ethylene sulfite (ES), propylene sulfite (PS), diethylene sulfate (DTD), 4-methylethylene sulfate (PCS), and 1,3-propylene sultone (PST).

[0138] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion 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%, etc., or it can be a range composed of any of the above numerical values.

[0139] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the fluorine-containing 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%, etc., or it can be a range composed of any of the above numerical values.

[0140] According to some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion 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%, etc., or it can be a range composed of any of the above numerical values.

[0141] Therefore, by adding the above-mentioned types and amounts of additives to the electrolyte, the HOMO of the above-mentioned types of additives is relatively high, and they can be preferentially decomposed to form dense CEI film and SEI film during the first high-voltage charging, thereby reducing the risk of electrolyte oxidation and increasing the life of the battery cell.

[0142] According to some embodiments of the present application, the additive also includes a carbonate additive, and based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 2%-5%. For example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., or it can be a range composed of any of the above numerical values. Thus, an SEI film containing a polymer is formed, the stability of the SEI film is improved, and the life of the battery cell is increased. According to some specific embodiments of the present application, the mass proportion of the cyclic carbonate additive is 3%-4%.

[0143] As an example, the carbonate additive includes one or more of vinylene carbonate (VC), propylene carbonate, and ethylene carbonate.

[0144] As an example, the carbonate additive includes VC.

[0145] According to some embodiments of the present application, the solvent includes cyclic carbonate and linear carbonate, and based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate is 15%-25%, and the mass proportion of the linear carbonate is 50%-70%. Thus, the stability of the electrolyte is improved.

[0146] As an example, the mass percentage of the cyclic carbonate may be 15%, 17%, 19%, 21%, 23% or 25%, etc., or may be a range consisting of any of the above values.

[0147] As an example, the mass percentage of the linear carbonate may be 50%, 55%, 60%, 65% or 70%, etc., or may be a range consisting of any of the above values.

[0148] According to some embodiments of the present application, the cyclic carbonate includes ethylene carbonate (EC).

[0149] According to some embodiments of the present application, the linear carbonate includes one or both of dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0150] According to some embodiments of the present application, the solvent includes one or more of EC, DMC, EMC and diethyl carbonate (DEC).

[0151] In the present application, solvent refers to a substance whose mass proportion in the electrolyte is greater than or equal to 10%.

[0152] The present application provides a battery device, which may be a battery module, a battery pack, an energy storage battery, etc.

[0153] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square or any other shape. Figure 2 The battery cell 5 is a square structure as an example.

[0154] In some embodiments, reference Figure 3 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0155] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0156] Figure 4 4 is an example of a battery module. Figure 4 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0157] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0158] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0159] Figure 5 and Figure 6 1 is a battery pack 1 as an example. Figure 5 and Figure 6 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery cell box in any manner.

[0160] In addition, the present application also provides an electric device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as power sources for the electric device, and can also be used as energy storage units for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but are not limited thereto.

[0161] As the electrical equipment, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0162] Figure 7The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0163] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0164] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0165] Example 1

[0166] 1. Positive electrode

[0167] The positive electrode sheet includes a positive electrode current collector aluminum foil, and there are positive electrode films on both surfaces of the aluminum foil. The thickness of the single-sided positive electrode film layer is 97.4 μm, and the compaction density is 2.4 g / cm 3 The coating weight of the single-sided positive electrode film is 23.4 mg / cm 2 Based on the total mass of a single-sided positive electrode film layer, the positive electrode film layer includes 94.3% lithium iron phosphate material, 2.5% lithium supplement Li5FeO4 (with Li3PO4 coated on the surface), 1% conductive agent carbon black, and 2.2% binder polyvinylidene fluoride (PVDF), and the longest diameter of the lithium iron phosphate is 1.5μm.

[0168] 2. Negative electrode

[0169] The negative electrode sheet includes a negative electrode current collector copper foil, and there are negative electrode films on both surfaces of the copper foil. The thickness of the single-sided negative electrode film is 53.8 μm, and the compaction density is 1.45 g / cm 3 The coating weight of the double-sided negative electrode film is 15.6 mg / cm 2 Based on the total mass of a single-sided negative electrode film layer, the negative electrode film layer includes 96.2% by mass of active material artificial graphite (94% graphitization degree), 0.8% of conductive agent carbon black, 1.8% of binder styrene-butadiene rubber (SBR), and 1.2% of thickener sodium carboxymethyl cellulose (CMC-Na).

[0170] 3. Electrolyte

[0171] The electrolyte includes a solvent, an electrolyte salt and an additive. The solvent includes EC, DMC and EMC, wherein the mass ratio of EC, DMC and EMC is 31.5:37.3:31.2. The electrolyte salt is LiPF6, and the molar concentration of LiPF6 is 1.2 mol / L. The additives include phosphorus-containing additives, fluorine-containing additives, sulfur-containing additives and carbonate additives. The phosphorus-containing additive is LiDFP, and the mass proportion of LiDFP based on the total mass of the electrolyte is 0.039%; the fluorine-containing additives are FEC, LIDFOB and LIBF4, and the mass proportion of FEC based on the total mass of the electrolyte is 0.23%, the mass proportion of LIDFOB is 0.0246%, and the mass proportion of LIBF4 is 0.0091%; the sulfur-containing additive is PS, and the mass proportion of PS based on the total mass of the electrolyte is 0.54%; the carbonate additive is VC, and the mass proportion of VC based on the total mass of the electrolyte is 3.34%.

[0172] 4. Isolation film

[0173] Polyethylene film.

[0174] 5. Battery Cell

[0175] A battery cell includes a positive electrode plate, a separator, a negative electrode plate and an electrolyte.

[0176] Performance Testing

[0177] 1. 25℃ Cycle Performance

[0178] At 25°C, charge the corresponding battery at a constant current of 1 / 3C to 3.65V, then charge at a constant voltage of 3.65V to a current of 0.05C, leave for 5 minutes, and then discharge at 1 / 3C to 2.5V. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery, and record the discharge capacity C of the battery after the nth cycle. n , then the battery capacity retention rate P after each cycle n =C n / C0×100%, and obtain the battery capacity retention rate.

[0179] During the test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 1000th cycle corresponds to n=1000.

[0180] 2. Energy density

[0181] At 25°C, weigh the corresponding battery and record its mass m, charge it to 3.65V at a constant current of 1 / 3C, charge it to 0.05C at a constant voltage of 3.65V, leave it for 5 minutes, and discharge it to 2.5V at 1 / 3C. Repeat 3 cycles, record the energy of the third cycle as W, and the energy density = W / m.

[0182] 3. 45℃ storage performance

[0183] At 25°C, 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, left for 5 minutes, and then discharged to 2.5V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0. Charge to 3.65V at 1 / 3C and then constant voltage to 0.05C, then place the battery in a 45°C constant temperature oven for 150 days and then take it out and discharge it to 2.5V at room temperature. The removed battery was charged to 3.65V at 25°C at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left for 5 minutes, and then discharged to 2.5V at 1 / 3C, and the capacity C was recorded. n , the capacity retention rate is (C n / C0)×100%.

[0184] Comparative Example 1

[0185] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the positive electrode film layer does not contain a lithium supplement.

[0186] Comparative Example 2

[0187] The positive electrode sheet and the negative electrode sheet in the battery cell are the same as those in Example 1, except that the electrolyte does not contain phosphorus-containing additives, fluorine-containing additives, or sulfur-containing additives.

[0188] Example 2-Example 4

[0189] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the aspect ratio of the lithium supplement is different.

[0190] Example 5

[0191] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the type of lithium supplement in the positive electrode film layer is different.

[0192] The differences between Example 1 to Example 5 and Comparative Example 1 are shown in Table 1.

[0193] Table 1

[0194]

[0195] The differences between Example 1 and Comparative Example 2 are shown in Table 2.

[0196] Table 2

[0197]

[0198] It can be seen from the comparison between Examples 1 to 4 and Comparative Examples 1 and 2 that the battery cell proposed in the present application has a high cycle capacity retention rate and a storage capacity retention rate while having a high energy density, that is, the battery cell has excellent cycle performance and storage performance while having a high energy density. Explanation: The present application provides a lithium supplement on the positive electrode plate, and the lithium supplement decomposes during the formation stage to make up for the lithium ions consumed in forming the SEI film, thereby improving the energy density of the battery; the electrolyte includes phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. Under high-pressure conditions, the above-mentioned types of additives can preferentially decompose to form stable CEI films and SEI films, thereby reducing the risk of oxidative decomposition of the electrolyte, improving the stability of the electrolyte under high-pressure conditions, and improving the cycle life and storage life of the battery.

[0199] It can be seen from Examples 1 and 5 that adding appropriate amounts of different types of lithium supplements can improve the energy density of battery cells, and by adding additives with high HOMO energy levels to the electrolyte, a battery cell with both high energy density and long life can be obtained.

[0200] Embodiment 6, Embodiment 7

[0201] The positive electrode sheet and the negative electrode sheet in the battery cell are the same as those in Example 1, except that the total content of the additive in the electrolyte is different. The difference is detailed in Table 3.

[0202] Table 3

[0203]

[0204] It can be seen from the comparison between Example 1, Example 6 and Example 7 that by adjusting the content of the additive in the electrolyte, the stability of the electrolyte under high voltage can be improved, the risk of the electrolyte being decomposed by high voltage can be reduced, and the cycle life of the battery cell can be increased.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: include: A positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprising a plurality of first regions and a plurality of second regions; The first region includes a positive electrode active material, the first region includes an iron element and a phosphorus element, and a molar ratio of the phosphorus element to the iron element is 0.5-1.5; The second region includes a lithium supplement, the second region includes phosphorus and a transition metal M, the transition metal M includes one or more of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn, and the molar ratio of the phosphorus to the transition metal M is a, and satisfies 0≤a≤0.2; A negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector; An electrolyte, wherein the electrolyte includes additives, wherein the additives include one or more of a phosphorus-containing additive, a fluorine-containing additive, and a sulfur-containing additive, and 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 accounts for 0.2%-2.1%.

2. The battery cell according to claim 1, characterized in that: The positive electrode active material includes lithium iron phosphate. In a cross-sectional view in 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 supplement.

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

5.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The lithium supplement comprises 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 to 3, characterized in that: The lithium supplement includes one or two of Li2NiO2 and Li5FeO4.

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

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

8. The battery cell according to any one of claims 1 to 7, characterized in that: The electrolyte solution further includes an electrolyte salt, and the molar concentration of the electrolyte salt in the electrolyte solution is 1.1 mol / L-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 fluorinated lithium sulfonyl imide.

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

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

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

13. The battery cell according to any one of claims 10 to 12, characterized in that: The graphitization degree of the graphite is 93%-97%, and can be optionally 93%-96%.

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

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

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

17. The battery cell according to any one of claims 1 to 16, characterized in that: The electrolyte also includes a solvent, and the solvent includes a cyclic carbonate and a linear carbonate. Based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate is 15%-25%, and the mass proportion of the linear carbonate is 50%-70%.

18. The battery cell according to claim 17, characterized in that: The cyclic carbonate includes ethylene carbonate.

19. The battery cell according to claim 17 or 18, characterized in that: The linear carbonate includes one or both of dimethyl carbonate and ethyl methyl carbonate.

20. The battery cell according to any one of claims 1 to 19, characterized in that: The additives further include carbonate additives, and the carbonate additives include one or more of vinylene carbonate, propylene carbonate, and vinyl ethylene carbonate.

21. The battery cell according to claim 20, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the carbonate additive is 2%-5%, and can be optionally 3%-4%.

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

23. The battery cell according to any one of claims 1 to 22, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the fluorine-containing additive is 0.05%-0.5%.

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

25. The battery cell according to any one of claims 1 to 24, characterized in that: The phosphorus-containing additive includes one or more of lithium difluorophosphate, tris(trimethylsilyl)phosphate, triphenylphosphine oxide, triethyl phosphate, trimethylolpropane, and trifluoroethyl ethylene phosphate.

26. The battery cell according to any one of claims 1 to 25, characterized in that: The fluorine-containing additive includes one or more of fluoroethylene carbonate, difluoroethylene carbonate, perfluoroalkylethylene carbonate, tris(trimethylsilyl)borate, lithium tetrafluoroborate, lithium bis(oxalatoborate), and lithium difluorooxalatoborate.

27. The battery cell according to any one of claims 1 to 26, characterized in that: The sulfur-containing additive includes one or more of vinyl sulfite, propylene sulfite, vinyl sulfate, 4-methylethylene sulfate, and 1,3-propylene sultone.

28. The battery cell according to any one of claims 2 to 27, characterized in that: The particle size distribution of the lithium iron phosphate is unimodal, and the particle size distribution span value is 1.5-1.

7.

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

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

31. The battery cell according to any one of claims 1 to 30, characterized in that: At least part of the surface of the lithium supplement agent has a second carbon coating layer. Based on the total mass of the lithium supplement agent, the mass proportion of the second carbon coating layer is 1%-5%, and can be 2%-4%.

32. The battery cell according to any one of claims 1 to 31, 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.

33. The battery cell according to any one of claims 1 to 32, characterized in that: The battery cell further includes: a separator, wherein the separator includes: A base film, wherein the material of the base film comprises polyethylene; an adhesive layer, the adhesive layer being located on at least one side of the base film; The ceramic layer is located on a side of the bonding layer away from the base film.

34. The battery cell according to claim 33, characterized in that: The isolation film is disposed between the positive electrode sheet and the negative electrode sheet, and the ceramic layer is close to the positive electrode sheet.

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

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

37. A battery device, characterized in that: Comprising a battery cell according to any one of claims 1-36.

38. An electrical equipment, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 36, wherein the battery cell is used to provide electrical energy.

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