Battery cell, battery device, and electric device

Abstract

The application discloses a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a positive electrode active material and a lithium supplement agent, in a section along the thickness direction of the positive electrode sheet, the longest diameter of the positive electrode active material particles with a quantity ratio of more than 50% is less than the shortest diameter of the lithium supplement agent particles; the negative electrode sheet comprises a negative electrode active material layer, the negative electrode active material layer comprises a negative electrode active material, the volume particle size distribution Dv90 of the negative electrode active material is 15-30 mu m, and the negative electrode active material comprises graphite. Therefore, the battery can have higher energy efficiency and longer service life.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to battery cells, battery devices, and power-consuming devices. Background Technology

[0002] Secondary batteries are not only used in energy storage systems for 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. With the development of society, people have increasingly higher requirements for batteries, such as high energy efficiency and long service life. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides a battery cell that aims to achieve high energy efficiency and long service life.

[0004] To achieve the above objectives, in a first aspect of this application, a battery cell is provided, comprising:

[0005] A positive electrode sheet, the positive electrode sheet including a positive active material layer, the positive active material layer including a positive active material and a lithium supplementing agent, wherein, along the thickness direction of the positive electrode sheet, more than 50% of the positive active material particles have a longest diameter smaller than the shortest diameter of the lithium supplementing agent particles.

[0006] A negative electrode sheet, wherein the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, the volume particle size distribution Dv90 of the negative electrode active material is 15μm-30μm, and the negative electrode active material includes graphite.

[0007] The battery cell of the first aspect of this application has at least the following beneficial effects: by simultaneously designing the positive electrode and the negative electrode, the longest diameter of the positive active material particles and the shortest diameter of the lithium replenishing agent particles meet the above-mentioned range, and by matching them with negative active material particles whose volume particle size distribution Dv90 meets the above-mentioned range, the uniformity of lithium ion extraction in the positive electrode can be improved on the basis of positive electrode lithium replenishment. At the same time, the lithium ions extracted from the positive electrode can be quickly and uniformly inserted into the negative electrode, and the side reactions of the negative electrode can be reduced. In this way, the risk of lithium plating in the negative electrode can be reduced, the lithium replenishment effect and kinetic performance of the battery can be improved, and the battery can have both high energy efficiency and long service life.

[0008] In some embodiments of this application, the OI value of the graphite is 2-5. This is beneficial for lithium-ion intercalation and improves the kinetic performance of the battery.

[0009] In some embodiments of this application, the volume average particle size Dv50 of the graphite is 6 μm-12 μm. This is beneficial for shortening the transport path of lithium ions in the graphite bulk phase and improving the kinetic performance of the battery.

[0010] In some embodiments of this application, the lithium supplement includes Li x M1 y O z Where 1≤x≤6, 1≤y≤6, 2≤z≤12, and M1 includes one or more of the elements Na, Ni, Co, Mn, Al, and Fe.

[0011] In some embodiments of this application, the lithium replenishing agent includes Li2NiO2 and / or Li5FeO4. This can achieve a better lithium replenishment effect.

[0012] In some embodiments of this application, the lithium supplement includes Li n NiO m and / or Li p FeO q , where 0≤n≤2, 0<m≤2, 0<p≤5, 0<q≤4.

[0013] In some embodiments of this application, the lithium supplement includes NiO. m and / or Li p FeO q , where 0 < m ≤ 2, 0 < p ≤ 1, 0 < q ≤ 2.

[0014] In some embodiments of this application, at least a portion of the surface of the lithium replenishing agent is provided with a coating layer, which includes one or more of the elements C, Al, Zr, P, and S. This improves the air stability of the lithium replenishing agent, reduces the formation of lithium impurities on its surface, and also enhances its kinetic performance, facilitating delithiation.

[0015] In some embodiments of this application, the coating layer includes one or more of carbon materials, aluminum oxides, zirconium oxides, lithium phosphides, and lithium sulfides.

[0016] In some embodiments of this application, the lithium replenishing agent further includes a doping element, which includes one or more of Al, Zr, and B. This not only helps to reduce the decomposition voltage of the lithium replenishing agent and improve its decomposition capability, enabling it to perform greater capacity compensation, but also helps to stabilize the crystal structure of the lithium replenishing agent after decomposition, reducing the dissolution of transition metals and possible side reactions with the electrolyte.

[0017] In some embodiments of this application, based on the total mass of the lithium replenishing agent, the contents of Al, Zr and B elements in the lithium replenishing agent are independently 50ppm-1000ppm.

[0018] In some embodiments of this application, the compaction density of the positive electrode active material layer is 2.1 g / cm³. 3 -2.5g / cm 3 This facilitates electrolyte wetting and improves ionic conductivity.

[0019] In some embodiments of this application, the single-sided coating weight of the positive electrode active material layer is 0.25g / 1540.25mm. 2 -0.3g / 1540.25mm 2 This helps reduce electrode polarization and improve the battery's dynamic performance.

[0020] In some embodiments of this application, the compaction density of the negative electrode active material layer is 1.2 g / cm³. 3 -1.5g / cm 3 This facilitates electrolyte wetting and improves ionic conductivity.

[0021] In some embodiments of this application, the single-sided coating weight of the negative electrode active material layer is 0.12 g / 1540.25 mm. 2 -0.15g / 1540.25mm 2 This helps reduce electrode polarization and improve the battery's dynamic performance.

[0022] In some embodiments of this application, the battery cell further includes an electrolyte comprising a solvent, the solvent comprising cyclic carbonates and linear carbonates, wherein, 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 is beneficial for improving the stability of the electrolyte and enhancing the kinetic performance of the battery.

[0023] In some embodiments of this application, the electrolyte further includes a lithium salt with a concentration of 0.6 mol / L to 1.2 mol / L, optionally 0.7 mol / L to 1 mol / L. This is beneficial for obtaining higher ionic conductivity and improving battery kinetic performance.

[0024] In some embodiments of this application, the electrolyte further includes fluoroethylene carbonate and vinylene carbonate.

[0025] In some embodiments of this application, the fluoroethylene carbonate has a mass content of 0.1%-0.2% in the electrolyte, and the vinylene carbonate has a mass content of 1%-1.5% in the electrolyte.

[0026] In some embodiments of this application, the battery cell further includes a separator, the separator comprising a base film, and at least one side of the base film having a coating.

[0027] In some embodiments of this application, the thickness of the separator is 7μm-14μm. This is advantageous in simultaneously achieving good puncture resistance of the separator and energy density of the battery.

[0028] In some embodiments of this application, the thickness of the isolation membrane is 10μm-12μm.

[0029] In some embodiments of this application, the positive electrode active material includes a polyanionic positive electrode active material. This is beneficial for improving the cycle life of the battery.

[0030] In some embodiments of this application, the positive electrode active material layer further includes a conductive agent, which comprises conductive carbon black and / or carbon nanotubes. This not only improves the conductivity of the electrode but also facilitates the decomposition of the lithium replenishment agent and enhances the battery's kinetic performance.

[0031] In some embodiments of this application, the positive electrode active material includes lithium iron phosphate materials.

[0032] A second aspect of this application provides a battery device comprising: the battery cell described in the first aspect of this application, wherein the battery device includes at least one of a battery module, a battery pack, and an energy storage device.

[0033] A third aspect of this application provides an electrical device comprising: a battery cell as described in the first aspect of this application or a battery device as described in the second aspect of this application, wherein the battery cell or the battery device is used to provide electrical energy. Attached Figure Description

[0034] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0035] Figure 1 A scanning electron microscope image of the cross-section of the positive electrode sheet in a single battery cell according to one embodiment of this application.

[0036] Figure 2 This is a scanning electron microscope image of the cross-section of the positive electrode sheet in a battery cell according to another embodiment of this application.

[0037] Figure 3This is a schematic diagram of the structure of a battery cell according to one embodiment of this application.

[0038] Figure 4 This is a schematic diagram of the structure of a battery module according to one embodiment of this application.

[0039] Figure 5 This is a schematic diagram of the structure of a battery pack according to one embodiment of this application.

[0040] Figure 6 yes Figure 5 The exploded diagram.

[0041] Figure 7 This is a schematic diagram of one embodiment of the battery device used as a power source in this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1: Battery cell; 2: Battery module; 3: Battery pack; 4: Upper casing; 5: Lower casing; 10: Lithium replenishment agent; 11: Covering layer. Detailed Implementation

[0044] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0045] In this application, the reference to "embodiment" means that a specific 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 mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0046] The "range" disclosed in this application is defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit, which defines the boundary of the particular range. Ranges defined in this way may or may not include endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form an undefined range, and any lower limit can be combined with other lower limits to form an undefined range. Similarly, any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, each individually disclosed point or single value can itself serve as a lower limit or upper limit, combined with any other point or single value, or combined with other lower limits or upper limits to form an undefined range.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0049] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S1 and S2, indicating that the method may include steps S1 and S2 performed sequentially, or it may include steps S2 and S1 performed sequentially. For example, the method may also include step S3, indicating that step S3 may be added to the method in any order. For example, the method may include steps S1, S2, and S3, or it may include steps S1, S3, and S2, or it may include steps S3, S1, and S2, etc.

[0050] Unless otherwise specified, in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0051] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0052] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms "comprising" and "having," and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion. Unless otherwise stated, the terms used in this application have their commonly understood meanings as understood by one of ordinary skill in the art. Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0053] With the continuous advancement of green and environmentally friendly themes, battery applications have penetrated into all aspects of life, including vehicles, electronic devices, and energy storage devices. However, as battery applications continue to expand, people's requirements for batteries are also increasing. For example, taking lithium-ion batteries as an example, high-energy-efficiency and long-life rechargeable batteries have become an important research direction in the battery industry. Among existing battery systems, there is a scheme that uses lithium iron phosphate-based positive electrode active materials combined with graphite negative electrodes to improve the cycle stability and reliability of batteries and extend their lifespan. However, this scheme suffers from low initial efficiency of graphite and the need to consume active lithium during the SEI film stabilization process, resulting in rapid capacity decay in the early stages, making it difficult to adequately meet customers' increasingly demanding requirements for long lifespans.

[0054] This application aims to develop battery cells that combine high energy efficiency and long service life. The battery cell of this application incorporates a lithium supplement agent in the positive electrode and comprehensively controls the particle size relationship between the lithium supplement agent and the positive electrode active material, as well as the volumetric particle size distribution of the negative electrode active material, to develop a battery cell with high energy density and long service life.

[0055] In the positive electrode sheet of this application, the positive active material layer includes a positive active material and a lithium supplement. In the cross section along the thickness direction of the positive electrode sheet, the longest diameter of the positive active material particles, which accounts for more than 50% of the total, is smaller than the shortest diameter of the lithium supplement particles. In the negative electrode sheet, the volumetric particle size distribution Dv90 of the negative active material is 15μm-30μm, and the negative active material includes graphite.

[0056] Introducing lithium replenishers can improve the initial efficiency and cycle performance of battery cells, and increase their cycle life and service life. However, if the lithium replenisher is unevenly dispersed in the positive electrode active material layer, it can easily lead to uneven lithium extraction from the positive electrode, increasing the risk of lithium plating and dendrite formation in the negative electrode. Simultaneously, if the lithium ions extracted from the positive electrode cannot be quickly and uniformly embedded in the negative electrode active material layer, it will also weaken the battery's kinetic performance and increase the risk of lithium plating and dendrite formation. In this application, by appropriately increasing the particle size of the lithium replenisher particles, ensuring that the longest diameter of more than half of the positive electrode active material particles is smaller than the shortest diameter of the lithium replenisher particles, the uniformity of the lithium replenisher's dispersion in the positive electrode active material layer can be effectively improved. This allows lithium ions to be uniformly extracted during the delithiation process of the positive electrode, reducing the risk of excessive local lithium ion concentration due to lithium ion agglomeration and thus increasing the risk of lithium plating in the negative electrode. Meanwhile, if the particle size of the negative electrode active material is large, it increases the lithium-ion intercalation pathway and makes intercalation more difficult. Conversely, if the particle size is small, its surface activity is high, but the risk of side reactions is also higher. By using negative electrode active material particles with a volumetric particle size distribution (Dv90) of 15μm-30μm, it is possible to promote the rapid and uniform intercalation of lithium ions extracted from the positive electrode into the negative electrode sheet and reduce side reactions in the negative electrode. This results in a battery cell that possesses both high energy efficiency, good cycle performance, and a long service life.

[0057] The battery cells disclosed in this application can be used in electrical devices that use the battery cells or battery devices containing the battery cells as a power source, or in various energy storage systems that use the battery cells or battery devices containing the battery cells as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0058] The first aspect of this application provides a battery cell comprising: a positive electrode and a negative electrode. The positive electrode includes a positive active material layer comprising a positive active material and a lithium supplement agent. Along the thickness direction of the positive electrode, more than 50% of the positive active material particles have a longest diameter smaller than the shortest diameter of the lithium supplement agent particles. The negative electrode includes a negative active material layer comprising a negative active material. The negative active material has a volumetric particle size distribution Dv90 of 15 μm-30 μm, and the negative active material comprises graphite.

[0059] To improve battery cycle performance and achieve long cycle life and extended lifespan, lithium replenishment agents are typically introduced. These agents provide additional lithium during the initial charge to compensate for the lithium consumed by the SEI film, improving initial efficiency and cycle performance. However, uneven distribution of the lithium replenishment agent within the positive electrode active material layer can lead to uneven lithium extraction, increasing the risk of lithium plating and dendrite formation. This not only affects the battery's kinetic performance but also its energy efficiency and cycle life. To address this issue, the relative particle size relationship between the lithium replenishment agent and the positive electrode active material particles can be controlled. Instead of mixing lithium replenishment agent particles and positive electrode active material particles of similar size, creating a particle size distribution between the lithium replenishment agent and the positive electrode active material particles can effectively improve the uniformity of lithium replenishment agent dispersion within the positive electrode active material layer. Since the particle size of positive electrode active materials (such as lithium iron phosphate) can typically be very small, processing smaller lithium replenishment particles is relatively more difficult, and the risk of agglomeration between small-sized lithium replenishment agent particles and small-sized positive electrode active material particles is also greater, similarly increasing the risk of uneven lithium-ion extraction. In this application, by appropriately increasing the particle size of the lithium replenishing agent particles, the longest diameter of more than half of the positive electrode active material particles is smaller than the shortest diameter of the lithium replenishing agent particles. This allows the lithium replenishing agent and the positive electrode active material particles to form a size distribution, effectively improving the dispersion uniformity of the lithium replenishing agent in the positive electrode active material layer. Consequently, during the delithiation process of the positive electrode sheet, lithium ions can be uniformly removed, reducing the risk of excessive local lithium ion concentration due to lithium ion agglomeration and thus increasing the risk of lithium deposition on the negative electrode.

[0060] Meanwhile, if lithium ions extracted from the positive electrode cannot be quickly and uniformly embedded into the negative electrode active material layer, it will weaken the battery's kinetic performance and increase the risk of lithium plating and dendrite formation at the negative electrode. Therefore, to ensure that lithium ions extracted from the positive electrode can be quickly and uniformly embedded into the negative electrode, negative electrode active particles with an appropriate particle size range are required. If the particle size of the negative electrode active material is too large, it will increase the lithium ion intercalation path, making intercalation more difficult and hindering the improvement of battery kinetic performance and the reduction of lithium plating risk. Conversely, if the particle size of the negative electrode active material is too small, its surface activity is higher, increasing the risk of side reactions and easily deteriorating the battery's energy efficiency, cycle life, and kinetic performance. In this application, based on ensuring that the particle size of the positive electrode active material and the lithium replenishing agent in the positive electrode sheet meets the above-mentioned range, negative electrode active material particles with a volume particle size distribution Dv90 of 15μm-30μm are combined. This not only improves the uniformity of lithium ion extraction on the basis of positive electrode lithium replenishment, but also enables the lithium ions extracted from the positive electrode to be quickly and uniformly embedded in the negative electrode sheet and reduces the side reactions of the negative electrode. Thus, the lithium replenishment effect and kinetic performance of the battery can be improved, and the battery can have both high energy efficiency, good cycle performance and long service life.

[0061] Therefore, the battery cell of the first aspect of this application has at least the following beneficial effects: it can enable the battery to have both high energy efficiency and long service life.

[0062] For example, the volumetric particle size distribution Dv90 of the negative electrode active material can be 15μm, 17μm, 19μm, 21μm, 23μm, 25μm, 28μm or 30μm, etc.

[0063] For example, in a cross-section along the thickness direction of the positive electrode sheet, there may be positive active material particles whose longest diameter is smaller than the shortest diameter of the lithium supplement particles, accounting for more than 50%, 60%, 70%, or 80% of the total. (Reference) Figure 1 understand, Figure 1 The image shown is a scanning electron microscope (SEM) image of the cross-section of the positive electrode of a battery cell in one embodiment of this application, which shows the particulate state of the lithium supplement 10 and the positive electrode active material.

[0064] In this application, the shortest diameter of the lithium replenishing agent particles and the longest diameter of the positive electrode active material particles are defined as follows: The positive electrode sheet, including the lithium replenishing agent particles and the positive electrode active material particles, is cut along its thickness direction to expose the cross-section of the positive electrode active material layer. The shortest diameter of the lithium replenishing agent particles and the longest diameter of the positive electrode active material particles are determined by scanning electron microscopy (SEM) testing of the cross-section of the positive electrode active material layer. Specifically, the shortest diameter of the lithium replenishing agent is the shortest straight line passing through the center point of the lithium replenishing agent and extending to the outer periphery of the particle; the longest diameter of the positive electrode active material is the longest straight line passing through the center point of the positive electrode active material particle and extending to the outer periphery of the particle. In this application, the shortest diameter of the lithium replenishing agent particles and the longest diameter of the positive electrode active material particles can be tested by the following method: Selecting lithium replenishing agent particles in the cross-sectional image of the positive electrode active material layer and measuring their shortest diameter; selecting positive electrode active material particles in the cross-sectional image of the positive electrode active material layer and measuring the longest diameter of each of the multiple positive electrode active material particles.

[0065] In this application, one or more conventional instruments and methods, such as scanning electron microscopy, EDS energy dispersive spectroscopy, X-ray diffraction, and inductively coupled plasma atomic emission spectrometry, can be used to qualitatively analyze the positive electrode active material layer to determine whether a lithium replenishing agent exists in the positive electrode active material layer and what type of lithium replenishing agent it is. For example, in the positive electrode active material layer, in addition to differences in elemental composition, lithium replenishing agents and positive electrode active material particles usually differ in size and particle morphology. Moreover, lithium replenishing agents do not completely disappear after delithiation, but leave residual elements and particle skeletons. After delithiation, lithium replenishing agents usually undergo a certain volume shrinkage, causing a certain gap between the residual particle skeleton and the surrounding area (see reference). Figure 2 As shown, Figure 2This is a scanning electron microscope (SEM) image of the cross-section of the positive electrode sheet in a battery cell according to another embodiment of this application. It shows the microstructure of the lithium replenishing agent 10 with the coating layer 11 after delithiation (a gap forms between the particle skeleton of the lithium replenishing agent 10 and its surface coating layer 11 during the later stage of delithiation). Based on these differences, the possible locations of the lithium replenishing agent in the cross-section along the thickness direction of the positive electrode sheet can be quickly screened during SEM testing. Furthermore, EDS energy dispersive spectroscopy analysis can be used to distinguish the lithium replenishing agent particles and the positive electrode active material particles by elemental composition, thereby comparing the size differences between the positive electrode active particle size and the lithium replenishing agent particle size. For example, the surface roughness of the positive electrode active material particles and the lithium replenishing agent particles is usually different; this difference can also be used to quickly screen the possible locations of the lithium replenishing agent during SEM testing. For example, lithium replenishing agents typically do not completely delithigate after formation. The changes in diffraction peaks (such as peak position and intensity) of the XRD patterns of the positive electrode active material layer before and after charge / discharge can be compared to pre-determine whether a lithium replenishing agent has been added to the positive electrode and what type of lithium replenishing agent has been added. Furthermore, due to differences in lithium content between the lithium replenishing agent and the positive electrode active material, as well as differences in lithium insertion / extraction efficiencies during charge / discharge, their lithium content in the fully charged and discharged states also differs. For instance, in the charging state, the delithiation efficiency of the lithium replenishing agent in the positive electrode is usually lower than that of the positive electrode active material, which can be distinguished by FIB (Focused Ion Beam) combined with SIMS (Secondary Ion Mass Spectrometry). Moreover, during a charge / discharge process, the difference in lithium insertion / extraction efficiencies between the lithium replenishing agent and the positive electrode active material results in significant differences in the volume expansion between material particles, which can be observed and characterized by in-situ confocal microscopy.

[0066] In this application, conventional instruments such as particle size analyzers (e.g., laser particle size analyzers) can be used to test the particle size of the negative electrode active material in the negative electrode active material layer. For example, wet methods and / or ultrasonic methods can be used to separate the negative electrode active material layer and the negative electrode current collector, thereby obtaining negative electrode active material particles.

[0067] In the battery cell of this application, in the cross-section along the thickness direction of the positive electrode sheet, it is required that more than 50% of the positive electrode active material particles have a longest diameter smaller than the shortest diameter of the lithium replenishing agent particles. This also allows for design space to further improve the energy density and service life of the battery cell. For example, the energy density of the battery can be further improved and the service life extended by combining a small number of large-diameter positive electrode active material particles with the positive electrode active material particles whose longest diameter is smaller than the shortest diameter of the lithium replenishing agent particles to form a particle size distribution.

[0068] In some embodiments of this application, the OI value of graphite can be 2-5, for example, 2, 2.5, 3, 3.5, 4, 4.5, or 5. The OI value of graphite can be calculated in conjunction with XRD testing. A low OI value of graphite indicates a large number of lithium-ion extraction / intercalation facets in the graphite, which is beneficial for lithium-ion intercalation and improves kinetic performance. Therefore, ensuring that the OI value of graphite meets the given range is beneficial for further improving the kinetic performance of the battery.

[0069] In some embodiments of this application, the volume average particle size Dv50 of graphite can be 6μm-12μm, for example, 7μm, 8μm, 9μm, 10μm, 11μm, or 12μm, etc. The volume average particle size Dv50 of graphite can also be measured using a particle size analyzer. Small-diameter graphite has a shorter lithium-ion transport path, which is beneficial for further improving the kinetic performance of the battery.

[0070] In some embodiments of this application, the volume average particle size Dv50 of the negative electrode active material can be 6μm-12μm, for example, 7μm, 8μm, 9μm, 10μm, 11μm or 12μm, etc. This is beneficial for further improving the kinetic performance of the battery.

[0071] In some embodiments of this application, the lithium supplement may include Li x M1 y O z Wherein, 1≤x≤6, 1≤y≤6, 2≤z≤12, and M1 may include one or more of the elements Na, Ni, Co, Mn, Al, and Fe. For example, the value of x can be 1, 2, 3, 4, 5, or 6, or a range of any of the above values. Optionally, the value of x can be 1 < x ≤ 6, such as 2 ≤ x ≤ 5; the value of y can be 1, 2, 3, 4, 5, or 6, or a range of any of the above values; the value of z can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, or a range of any of the above values. Optionally, the value of z can be 2 ≤ z ≤ 8. Wherein, Li x M1 y O z The charging capacity is 1 to 5 times that of multi-element positive electrode active materials, which can provide additional lithium during the first charge. Furthermore, it facilitates the pre-storage of additional lithium in the negative electrode, extending battery life. Lithium is incorporated into the positive electrode active material layer. x M1 y O zThis can achieve a good lithium replenishment effect. It is understandable that during battery formation and use, as the lithium replenishment process proceeds, lithium in the lithium replenishment agent will be partially or completely released, causing the lithium replenishment agent to change from the initial state to a partially delithiated state or a completely delithiated state. At this time, the situation x≤1 and / or z≤2 will occur.

[0072] In some embodiments of this application, the lithium supplementer may include, but is not limited to, Li2NiO2 and / or Li5FeO4. In the fabrication process of the positive electrode, Li2NiO2 and / or Li5FeO4 can be directly incorporated into the positive electrode active material layer. After delithiation, Li2NiO2 can form LiNiO2 with lithium insertion / extraction capability, and LiNiO2 in the delithiation state can become Li... 1-x1 NiO2, with 0≤x1≤1, can revert to LiNiO2 in the lithium-intercalated state; Li5FeO4 has strong lithium replenishment capacity, and the LiFeO2 formed after delithiation does not cause significant side reactions. Therefore, using Li2NiO2 and / or Li5FeO4 as lithium replenishers can achieve good capacity compensation. For example, Li2NiO2 can be used as the lithium replenisher, as it can provide considerable lithium replenishment capacity simply by changing the valence of Ni atoms at a lower potential, without needing to change the valence of oxygen atoms, thus reducing the risk of electrolyte oxidation by oxygen free radicals.

[0073] In some embodiments of this application, the lithium replenishing agent may include an initial state, a partially delithiated state, and a fully delithiated state. When the lithium replenishing agent transitions from the initial state to the partially delithiated state or the fully delithiated state, the lithium replenishing agent may include Li. n NiO m and / or Li p FeO q Wherein, 0 ≤ n ≤ 2, 0 < m ≤ 2, 0 < p ≤ 5, 0 < q ≤ 4. For example, the value of n can be 0, 0.5, 1, 1.5, or 2, or any range of the above values; the value of m can be 0.5, 1, 1.5, or 2, or any range of the above values; the value of p can be 0.5, 1, 2, 3, 4, or 5, or any range of the above values; the value of q can be 1, 2, 3, or 4, or any range of the above values. For example, taking a lithium replenishing agent initially in the state of Li2NiO2 as an example, when the lithium portion in Li2NiO2 is released, the lithium replenishing agent Li... n NiO m The composition may include one or more of the components of 0 < n < 1, n = 1, and 1 < n < 2; when lithium is completely extracted from Li2NiO2, the lithium replenishing agent Li n NiO m Its composition may include NiO mTaking a lithium replenisher initially in the form of Li5FeO4 as an example, when some lithium is released from Li5FeO4, the lithium replenisher Li... p FeO q The composition may include one or more of the following: 1 < p < 2, 2 ≤ p < 3, 3 ≤ p < 4, 4 ≤ p < 5; when lithium is completely extracted from Li5FeO4, the lithium replenishing agent Li p FeO q The composition may include LiFeO2. Under factors such as polarization, LiFeO2 may undergo further delithiation, resulting in Li with p < 1. p FeO q Components.

[0074] In some embodiments of this application, when the lithium replenishing agent transitions from an initial state to a fully delithiated state, the lithium replenishing agent may include NiO. m and / or Li p FeO q Wherein, 0 < m ≤ 2, 0 < p ≤ 1, 0 < q ≤ 2. For example, the value of m can be 0.5, 1, 1.5, or 2, or a range of any of the above values; the value of p can be 0.2, 0.5, 0.8, or 1, or a range of any of the above values; the value of q can be 0.2, 0.5, 1, 1.5, or 2, or a range of any of the above values. For example, taking a lithium replenishing agent initially in the form of Li2NiO2 and Li5FeO4 as an example, when the lithium replenishing agent is completely delithiated, the delithiated lithium replenishing agent can include, but is not limited to, NiO and / or LiFeO2.

[0075] In some embodiments of this application, at least a portion of the surface of the lithium replenishing agent may be coated with a layer, which may include one or more of the elements C, Al, Zr, P, and S. The elemental composition of the coating layer can be qualitatively analyzed using characterization techniques such as EDS (Energy Dispersive Spectroscopy). Lithium replenishing agents typically have poor air stability. For example, Li₂NiO₂ is highly alkaline and readily reacts with water and CO₂. Forming a coating layer on the surface of the lithium replenishing agent can, on the one hand, improve its air stability and reduce the formation of lithium impurities on the surface; on the other hand, it can also improve the ion-conducting properties of the lithium replenishing agent, improve lithium-ion transport efficiency, and enhance kinetic performance, thereby further facilitating delithiation and improving lithium replenishment capacity.

[0076] In some embodiments of this application, the coating layer may include one or more of carbon materials, aluminum oxides, zirconium oxides, lithium phosphides, and lithium sulfides. The type of coating layer material can be determined by combining one or more analytical methods such as EDS energy dispersive spectroscopy and X-ray diffraction. Since the lithium replenisher has relatively poor conductivity, using carbon materials, aluminum oxides, or zirconium oxides as coating layer materials is beneficial for improving the air stability of the lithium replenisher and reducing the formation of lithium impurities on the surface. Furthermore, using carbon materials as the coating layer material is beneficial for improving the conductivity of the positive electrode. Using fast ion conductors, such as lithium phosphides or lithium sulfides (exemplarily, including lithium phosphate or lithium sulfate), as the coating layer material is beneficial for improving the lithium-ion transport rate and enhancing kinetic performance, thereby further facilitating delithiation and improving lithium replenishment capacity. This is beneficial for further improving the electrochemical performance of the battery.

[0077] In some embodiments of this application, the lithium replenishing agent may further include doping elements, which may include one or more of Al, Zr, and B. Doping the lithium replenishing agent with one or more of Al, Zr, and B elements is beneficial for reducing the decomposition voltage of the lithium replenishing agent, improving its decomposition capability, enabling it to perform greater capacity compensation, and also helps to stabilize the crystal structure of the lithium replenishing agent after decomposition, reducing the dissolution of transition metals and possible side reactions with the electrolyte, thereby further contributing to a battery with both high energy efficiency and cycle life.

[0078] In some embodiments of this application, based on the total mass of the lithium replenishing agent, the contents of Al, Zr, and B elements in the lithium replenishing agent can be independently 50ppm-1000ppm, such as 50ppm, 200ppm, 500ppm, 800ppm, or 1000ppm, etc.

[0079] In some embodiments of this application, the positive electrode active material layer may further include a conductive agent, which may include conductive carbon black and / or carbon nanotubes. Lithium supplements have poor conductivity, while carbon nanotubes exhibit better conductivity than conductive carbon black, but are relatively more expensive. Using a composite of zero-dimensional conductive carbon black and one-dimensional carbon nanotubes as the conductive agent not only facilitates the dispersion of carbon nanotubes but also forms a better conductive network, achieving superior conductivity. Therefore, this not only improves the conductivity of the electrode but also facilitates the decomposition of the lithium supplement and enhances the battery's kinetic performance.

[0080] In some embodiments of this application, the positive electrode active material may include a polyanionic positive electrode active material. Optionally, the positive electrode active material may include, but is not limited to, lithium iron phosphate-based positive electrode active materials. It is understood that lithium iron phosphate-based positive electrode active materials may include, but are not limited to, doped or undoped lithium iron phosphate and lithium manganese iron phosphate materials. For example, the general structural formula of the polyanionic material may be Li... x2 Fe a Mn b M2 c O4, wherein 0.5≤x2≤1.2, a+b+c=1, 0.5≤a≤1, 0≤b≤0.5, 0≤c≤0.1, and M2 can be a transition metal element. Optionally, M2 can include one or more of V, Cr, Ni, Co, Cu, Al, Zr, etc. For example, the value of x2 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or 1.2, or a range of any of the above values; the value of a can be 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or a range of any of the above values; the value of b can be 0, 0.1, 0.2, 0.3, 0.4, or 0.5, or a range of any of the above values; and the value of c can be 0, 0.02, 0.05, 0.08, or 0.1, or a range of any of the above values. Qualitative and quantitative analyses of the positive electrode active material layer can be performed using one or more conventional instruments and methods, such as scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffraction, and inductively coupled plasma atomic emission spectrometry (ICP-AES), to determine the type of positive electrode active material. Compared to ternary positive electrode active materials, lithium iron phosphate (LFP) positive electrode active materials have a more stable crystal structure, resulting in better cycle stability and improved battery cycle life and lifespan.

[0081] In some embodiments of this application, the compaction density of the positive electrode active material layer can be 2.1 g / cm³. 3 -2.5g / cm 3 For example, it can be 2.1 g / cm³. 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 Or 2.5g / cm 3 Appropriately reducing the compaction density of the positive electrode active material layer is beneficial for electrolyte wetting and improves the battery's kinetic performance. Ensuring the compaction density of the positive electrode active material layer meets the given range can improve the battery's kinetic performance while maintaining its energy density.

[0082] In some embodiments of this application, the single-sided coating weight of the positive electrode active material layer can be 0.25g / 1540.25mm.2 -0.3g / 1540.25mm 2 For example, it could be 0.25g / 1540.25mm 2 0.28g / 1540.25mm 2 Or 0.3g / 1540.25mm 2 This helps reduce electrode polarization and improve the battery's kinetic performance.

[0083] In some embodiments of this application, the compaction density of the negative electrode active material layer can be 1.2 g / cm³. 3 -1.5g / cm 3 For example, it can be 1.2 g / cm³. 3 1.3g / cm 3 1.4g / cm 3 Or 1.5g / cm 3 Appropriately reducing the compaction density of the negative electrode active material layer is beneficial for electrolyte wetting and improves the battery's kinetic performance. Ensuring the compaction density of the negative electrode active material layer meets the given range can improve the battery's kinetic performance while maintaining its energy density.

[0084] In some embodiments of this application, the single-sided coating weight of the negative electrode active material layer can be 0.12 g / 1540.25 mm. 2 -0.15g / 1540.25mm 2 For example, it could be 0.12g / 1540.25mm 2 0.13g / 1540.25mm 2 0.14g / 1540.25mm 2 Or 0.15g / 1540.25mm 2 This helps reduce electrode polarization and improve the battery's dynamic performance.

[0085] In this application, the single-sided coating weight and compaction density of the positive electrode active material layer can be determined using the following method: The positive electrode sheet is disassembled from the battery cell. For example, a single-sided coated positive electrode sheet (if it is a double-sided coated sheet, the positive electrode active material layer on one side can be wiped off first) is cut into small circular pieces with an area of ​​S1. Its weight is weighed and recorded as M1, and its thickness H1 is measured. Then, the positive electrode active material layer of the weighed positive electrode sheet is wiped off, the weight of the positive current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the positive electrode active material layer = (weight of the positive electrode sheet M1 - weight of the positive current collector M0) / S1, the thickness of the positive electrode active material layer = thickness of the positive electrode sheet H1 - thickness of the positive current collector H0, and the compaction density of the positive electrode active material layer = single-sided coating weight of the positive electrode active material layer / thickness of the positive electrode active material layer. The single-sided coating weight of the negative electrode active material layer and the compaction density of the negative electrode can also be determined by referring to the method described above.

[0086] In some implementations, the compaction density of the positive or negative electrode active material layer can be the compaction density corresponding to approximately 0% SOC of the battery. 0% SOC refers to the state corresponding to charging a single battery cell at 1 / 3C constant current to 3.65V at room temperature, charging it at 3.65V constant voltage to a current of 0.05C, and then discharging it at 1 / 3C to 2.5V.

[0087] Typically, the positive electrode also includes a positive current collector, with the positive active material layer disposed on at least a portion of the surface of at least one side of the positive current collector. The positive current collector can be a conventional metal foil or a composite current collector (a composite current collector can be formed by depositing metal material on a polymer substrate). As an example, the positive current collector may include at least one of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil.

[0088] In some embodiments of this application, the positive electrode active material layer may optionally include at least one of a binder and other optional additives. The binder and additives can be conventional choices in the art; for example, the binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). These materials are all commercially available.

[0089] Typically, the negative electrode sheet also includes a negative electrode current collector, with the negative electrode active material layer disposed on at least a portion of the surface of at least one side of the negative electrode current collector. The negative electrode current collector can be a conventional metal foil or a composite current collector (e.g., a composite current collector can be formed by depositing a metal material on a polymer substrate). As an example, the negative electrode current collector can be a metal foil such as copper foil.

[0090] In some embodiments of this application, the negative electrode active material layer typically further includes a binder and a conductive agent. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. This application does not specifically limit the types of conductive agents and binders for the negative electrode sheet, and they can be selected according to actual needs. As an example, the conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder may include, but is not limited to, at least one of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC). In addition, the negative electrode active material layer may optionally include a thickener, such as carboxymethyl cellulose (CMC). However, this application is not limited to this, and other materials that can be used as thickeners for lithium-ion battery negative electrode sheets may also be used.

[0091] In some embodiments of this application, the battery cell further includes an electrolyte, which comprises a solvent. The solvent may include cyclic carbonates and linear carbonates. Based on the total mass of the electrolyte, the mass percentage of cyclic carbonates may be 15%-25%, and the mass percentage of linear carbonates may be 50%-70%. For example, based on the total mass of the electrolyte, the mass percentage of cyclic carbonates may be 15%, 18%, 20%, 22%, or 25%, etc.; and the mass percentage of linear carbonates may be 50%, 55%, 60%, 65%, or 70%, etc. Appropriately reducing the cyclic carbonate content is beneficial for reducing the electrolyte viscosity and increasing the lithium-ion transport rate; appropriately increasing the cyclic carbonate content is beneficial for increasing the dielectric constant of the electrolyte and reducing the migration resistance of lithium ions in the electrolyte. Thus, ensuring that the composition of the electrolyte meets the given range is beneficial for improving the stability of the electrolyte and improving the kinetic performance of the battery.

[0092] In some embodiments of this application, the cyclic carbonate may include EC (ethylene carbonate) and / or PC (propylene carbonate), for example, EC.

[0093] In some embodiments of this application, the linear carbonate may include one or more of EMC (ethyl methyl carbonate), DMC (dimethyl carbonate), and DEC (diethyl carbonate).

[0094] In some embodiments of this application, the electrolyte may further include a lithium salt, the concentration of which may be 0.6 mol / L to 1.2 mol / L, for example, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, etc. Exemplarily, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(fluoromethylsulfonate), lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonyl)imide. Appropriately increasing the lithium salt concentration can increase the number of lithium ions and improve ionic conductivity; appropriately decreasing the lithium salt concentration is beneficial for reducing electrolyte viscosity and improving ion transport efficiency and ionic conductivity. Therefore, ensuring the lithium salt concentration meets the given range is beneficial for obtaining higher ionic conductivity and improving battery kinetic performance. Optionally, the lithium salt concentration may be 0.7 mol / L to 1 mol / L.

[0095] In some embodiments of this application, the electrolyte may optionally include additives that can improve certain battery performance characteristics. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, additives that improve battery overcharge performance, high-temperature performance, or low-temperature performance, etc. Exemplarily, the additives may include, but are not limited to, FEC (fluoroethylene carbonate) and / or VC (ethylene carbonate). The mass content of fluoroethylene carbonate in the electrolyte may be 0.1%-0.2%, for example, 0.1%, 0.12%, 0.15%, 0.18%, or 0.2%, etc., and the mass content of vinylene carbonate in the electrolyte may be 1%-1.5%, for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, etc. This is beneficial for further improving battery performance.

[0096] In some embodiments of this application, the electrolyte may include one or more of phosphorus-containing additives, fluorine-containing additives, and sulfur-containing additives. This is beneficial for further improving battery performance.

[0097] In some embodiments of this application, the battery cell may further include a separator. Optionally, the separator may be any known porous membrane with electrochemical and mechanical stability, depending on actual needs. For example, it may include, but is not limited to, a single-layer or multi-layer film containing at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0098] In some implementations, the separator can be an uncoated separator. Uncoated separators are not only less expensive, but also facilitate smoother lithium-ion conduction and improve ionic conductivity.

[0099] In some embodiments, the separator may include a base film, and at least one side of the base film may be coated.

[0100] For example, the side of the base film facing the positive electrode may be provided with a ceramic coating containing inorganic oxides. For example, the inorganic oxides may include, but are not limited to, boehmite. Optionally, the ceramic coating may also include an adhesive, which may include, but is not limited to, acrylate adhesives. Providing a ceramic coating containing inorganic oxides is beneficial for improving the oxidation resistance and high-temperature stability of the separator.

[0101] For example, the side of the base film facing the negative electrode may be provided with an adhesive coating. Providing an adhesive coating helps save internal space in the battery and improves the volumetric energy density. Optionally, the adhesive coating may include, but is not limited to, polyvinylidene fluoride (PVDF) and / or polymethyl methacrylate (PMMA).

[0102] In some embodiments of this application, the thickness of the separator can be 7μm-14μm, for example, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, or 14μm. This is advantageous in simultaneously considering the puncture strength of the separator and the energy density of the battery, reducing the risk of the separator being easily punctured by dendrites due to its thinness or the risk of reduced battery energy density due to its thickness. Optionally, the thickness of the separator can be 10μm-12μm.

[0103] In some embodiments of this application, after the battery cell is formed, based on the carbon content on the surface of the negative electrode, the carbon content in the organic components is ≥60%, and the carbon-containing organic components include, but are not limited to, alkyl lithium, alkyl oxide lithium, alkyl ester lithium, etc. The carbon content in the organic components can be obtained by XPS analysis of the carbon elements on the surface of the negative electrode. Taking Li2NiO2 as an example, during the delithiation and decomposition of the lithium replenisher, oxygen changes its valence and releases oxygen free radicals. A small amount of oxygen free radicals can react with the carbonate electrolyte to generate carbonate protonated fragments, which are reduced at the negative electrode to form an organic SEI film, thereby enhancing the ionic conductivity and improving the kinetic performance of the battery.

[0104] The embodiments of this application do not impose particular limitations on the shape of the battery cell. For example, in some embodiments of this application, the battery can be a pouch battery, a prismatic battery, or a cylindrical battery. Figure 3 Here is a square-structured battery cell 1 as an example.

[0105] In some embodiments of this application, the battery cell can be a cylindrical battery, which may include a casing with a first end and a second end at its two ends. The first end can be connected to a negative electrode plate via the casing wall at the first end. For example, the tab of the negative electrode plate can be connected to the casing wall at the first end via a first current collector. The second end may be provided with a cap, which may include a terminal post. The terminal post can be connected to a positive electrode plate. For example, the tab of the positive electrode plate can be connected to the terminal post via a second current collector. Optionally, the cap can be a steel cap. The cap structure not only facilitates the welding connection of cylindrical batteries via current collectors (such as current buses), but also helps to release pressure after battery failure, reducing the safety risks that may be caused by the large amount of gas generated due to thermal runaway in high-nickel, high-silicon batteries.

[0106] In some embodiments, the battery cell may include an outer packaging. This outer packaging is used to encapsulate the positive electrode, the negative electrode, and the electrolyte.

[0107] In some embodiments, the outer packaging may include a shell and a cover. The shell may include a base plate and side plates attached to the base plate, the base plate and side plates enclosing a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover can be placed over the opening to close the receiving cavity.

[0108] The positive electrode, negative electrode, and separator can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is encapsulated within the receiving cavity. The number of electrode assemblies contained in a single battery cell can be one or more, and can be adjusted as needed.

[0109] In some implementations, the outer packaging of the battery may include a rigid shell, such as a rigid plastic shell, an aluminum shell, or a steel shell.

[0110] The outer packaging of a battery cell may also include a pouch, such as a bag-type pouch. The material of the pouch may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0111] A second aspect of this application provides a battery device comprising: a single battery cell according to the first aspect of this application. Optionally, the battery device may include at least one of a battery module, a battery pack, and an energy storage device.

[0112] In some implementations, the battery device can be either a single battery cell or a battery module or battery pack assembled from battery cells. The number of battery cells contained in a battery module or battery pack can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0113] Figure 4 This is battery module 2 as an example. (See reference...) Figure 4In battery module 2, multiple battery cells 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 1 can be secured with fasteners. Battery module 2 may also include a housing with a receiving space in which the multiple battery cells 1 are housed. In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0114] Figure 5 and 6 This is battery pack 3 as an example. (See reference...) Figure 5 and 6 The battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper body 4 and a lower body 5, with the upper body 4 covering the lower body 5 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0115] A third aspect of this application provides an electrical device comprising: a battery cell of the first aspect of this application or a battery device of the second aspect of this application, wherein the battery cell or battery device is used to provide electrical energy.

[0116] Specifically, the battery cell or battery device can serve 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), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0117] Figure 7 This is just one example of an electrical device. Such devices include pure electric vehicles, hybrid electric vehicles, or plug-in hybrid electric vehicles. Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and may use batteries as their power source.

[0118] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0119] Example 1

[0120] (1) Positive electrode plate

[0121] The device includes a positive electrode current collector aluminum foil, on both opposite surfaces of which a positive electrode active material layer is formed. The aluminum foil has a thickness of 13 μm, and the thickness of the positive electrode active material layer on both surfaces is equal. The single-sided coating weight of the positive electrode active material layer is 0.28 g / 1540.25 mm. 2 Based on the mass of the positive electrode active material layer, the positive electrode active material layer includes lithium iron phosphate with a mass ratio of 95.8%, lithium supplementer Li2NiO2 with a mass ratio of 2% (the lithium supplementer has aluminum oxide on its surface), conductive carbon black (Super P) with a mass ratio of 0.4%, and binder polyvinylidene fluoride (PVDF) with a mass ratio of 1.8%.

[0122] (2) Negative electrode plate

[0123] The device includes a negative electrode current collector copper foil. A negative electrode active material layer is deposited on both opposite surfaces of the copper foil. The copper foil has a thickness of 6 μm, and the thickness of the negative electrode active material layer on both surfaces is equal. The single-sided coating weight of the negative electrode active material layer is 0.14 g / 1540.25 mm. 2 Based on the mass of the negative electrode active material layer, the negative electrode active material layer includes 97.2% artificial graphite, 0.8% conductive agent (Super P), 0.8% binder styrene-butadiene rubber (SBR), and 1.2% thickener sodium carboxymethyl cellulose (CMC-Na).

[0124] (3) Electrolyte:

[0125] It includes solvent, electrolyte salt and additives. The solvent is prepared by EC, DMC and EMC in a mass ratio of 23:39:38. The electrolyte salt is LiPF6 and the concentration of LiPF6 in the electrolyte is 1 mol / L. The additives include FEC and VC. The mass percentage of FEC in the electrolyte is 0.15% and the mass percentage of VC in the electrolyte is 1.2%.

[0126] (4) Separation membrane: a porous polypropylene membrane with a thickness of 12μm.

[0127] (5) Battery cell: including the above-mentioned positive electrode, negative electrode, separator and electrolyte.

[0128] Performance testing:

[0129] (1) Energy density test

[0130] At 25℃, the formed battery is charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left to stand for 5 minutes, and then discharged at 1 / 3C to 2.5V. The discharge capacity is recorded as C. After measuring the size of the battery cell, its volume is calculated as V. The volumetric energy density is then 3.22×C / V.

[0131] (2) Energy efficiency test

[0132] At 25℃, the formed battery was left to stand for 30 minutes, then discharged to 2.5V with a constant current of 1 / 3C, and then charged to 3.65V with a constant power of 0.5P. The charging energy at this point was recorded as W. c Let it stand for 5 minutes; then discharge it at a constant power of 0.5P to 2.5V, and record the discharge energy as W. d .

[0133] Calculate the battery's energy efficiency (%) using the following formula: W d / W c ×100%.

[0134] (3) Cyclic performance test

[0135] At 25°C, the formed battery was left to stand for 30 minutes, then discharged to 2.5V with a constant current of 1 / 3C. Afterwards, charge-discharge cycles were performed as follows: leave to stand for 5 minutes, charge to 3.65V with a constant current of 1 / 3C, then charge at a constant voltage until the current drops to 0.05C, recording the charge capacity at this point as C0; leave to stand for 5 minutes; then discharge to 2.5V with a constant current of 1 / 3C. This cycle was repeated 450 times, and the discharge capacity C on the 450th cycle was recorded. 450 Calculate the capacity retention rate after 450 cycles using the following formula:

[0136] Capacity retention rate (%) after 450 cycles: C 450 / C0'×100%.

[0137] Comparative Example 1

[0138] The negative electrode and electrolyte in the battery cell are the same as in Example 1. The difference is that the positive electrode active material layer does not contain lithium replenishing agent, but the total mass ratio of positive electrode active material and lithium replenishing agent in the positive electrode active material layer is the same as in Example 1.

[0139] Comparative Example 2

[0140] The negative electrode and electrolyte in the battery cell are the same as in Example 1. The difference is that in the positive electrode, only the longest diameter of the positive active material particles, which account for less than 50% of the total number, is smaller than the shortest diameter of the lithium replenishing agent particles in the cross-section along the thickness direction of the positive electrode.

[0141] Comparative Example 3, Comparative Example 4

[0142] The positive electrode and electrolyte in the battery cell are the same as in Example 1, except that the Dv90 particle size of the graphite active material in the negative electrode is different.

[0143] The differences between Example 1 and Comparative Examples 1 to 4 are shown in Table 1.

[0144] Table 1

[0145]

[0146] As can be seen from Example 1 and Comparative Examples 1 to 4, the battery cell proposed in this application has both high energy efficiency and cycle capacity retention. This indicates that by using a lithium replenishing agent in the positive electrode sheet and making the shortest diameter of the lithium replenishing agent particles greater than the longest diameter of more than half of the positive electrode active material particles, while controlling the volume particle size Dv90 of the negative electrode active material graphite within a suitable range, the energy density of the battery cell can be improved, the energy efficiency and cycle performance of the battery cell can be improved, and the service life of the battery cell can be extended.

[0147] Example 2, Example 3, Example 4

[0148] The positive electrode and electrolyte in the battery cell are the same as in Example 1, except that the graphite in the negative electrode has a different Dv90 particle size and a different OI value.

[0149] Example 5

[0150] The positive electrode and electrolyte in the battery cell are the same as in Example 1, except that the OI value of the graphite in the negative electrode is different.

[0151] The differences between Examples 2 to 5 and Example 1 are shown in Table 2.

[0152] Table 2

[0153]

[0154] As can be seen from Examples 1, 3-4, and 2-5, appropriately reducing the volumetric particle size of the negative electrode active material, graphite, is beneficial to improving the energy density, energy efficiency, and cycle performance of the battery. The reason for this may be that when the particle size of the negative electrode active material is large, the compaction density of the negative electrode active material layer is relatively small, which affects the energy density of the battery cell. Appropriately reducing the volumetric particle size of the negative electrode active material not only helps to increase the compaction density of the negative electrode active material layer but also helps to improve the lithium-ion insertion / extraction efficiency at the negative electrode, thus improving the kinetic performance of the battery cell. Conversely, when the particle size of the negative electrode active material is small, its specific surface area is large, its activity is high, and the probability of side reactions is also high, which also easily affects the energy density of the battery cell. Furthermore, as can be seen from Examples 4 and 5, reducing the OI value of graphite is also beneficial to improving the energy efficiency and cycle capacity retention of the battery cell. The reason for this may be that a lower OI value of graphite further facilitates the lithium-ion insertion / extraction, improving the kinetic performance of the battery cell, thereby improving the energy efficiency and cycle capacity retention of the battery cell. In summary, this application controls the volumetric particle size Dv90 and OI value of artificial graphite in the negative electrode sheet within a suitable range, which further helps to enable the battery cell to have both high energy density, energy efficiency and cycle capacity retention, and can extend the service life of the battery cell.

[0155] Example 6

[0156] The negative electrode and electrolyte in the battery cell are the same as in Example 1, except that the coating weight of the positive electrode active material layer is different in the positive electrode.

[0157] Example 7

[0158] The positive electrode and electrolyte in the battery cell are the same as in Example 1, except that the coating weight of the negative electrode active material layer is different in the negative electrode.

[0159] The differences between Example 5, Example 6 and Example 1 are shown in Table 3.

[0160] Table 3

[0161]

[0162] As can be seen from Examples 1, 6, and 7, the energy density of the battery cell is improved with the increase of the coating weight of the active material layer in the positive and negative electrode sheets. However, the energy efficiency and cycle capacity retention rate of the battery cell are lower than those in Example 1. The main reason for this is that the increase in the coating weight of the active material layer of the electrode sheets leads to an increase in the thickness of the active material layer, which affects the internal resistance of the battery cell and makes the lithium ion transport path longer, thus affecting the energy efficiency and cycle capacity of the battery cell. This indicates that controlling the coating weight of the positive and negative active material layers within a suitable range is more conducive to enabling the battery cell to have both high energy density and energy efficiency, as well as good cycle performance and a longer service life.

[0163] Example 8

[0164] The negative electrode and electrolyte in the battery cell are the same as in Example 1, except that the type of conductive agent in the positive electrode active material layer is different in the positive electrode.

[0165] Example 9, Example 10

[0166] The negative electrode and electrolyte in the battery cell are the same as in Example 1. The difference is that the content of lithium replenishing agent in the positive electrode active material layer is different, but the total mass ratio of positive electrode active material and lithium replenishing agent in the positive electrode active material layer is the same as in Example 1.

[0167] Example 11

[0168] The negative electrode and electrolyte in the battery cell are the same as in Example 1. The difference is that the type and content of the lithium replenishing agent in the positive electrode active material layer and the material coating the surface of the lithium replenishing agent are different, but the total mass ratio of the positive electrode active material and the lithium replenishing agent in the positive electrode active material layer is the same as in Example 1.

[0169] The differences between Examples 8, 9, 10 and 11 and Example 1 are shown in Table 4.

[0170] Table 4

[0171]

[0172]

[0173] As can be seen from Examples 1 and 8, the energy density, energy efficiency, and cycle capacity retention of the battery cell were all improved after incorporating carbon nanotubes into conductive carbon black. This indicates that combining conductive carbon black with an appropriate amount of carbon nanotubes as a positive electrode conductive agent is more beneficial to extending the service life of the battery cell.

[0174] As can be seen from Examples 1, 9, and 10, the cycle capacity retention rate of the battery cell increases with the increase of the lithium replenishment agent content. However, the energy density of the battery cell shows a trend of first increasing and then decreasing. The main reason for this is that when the lithium replenishment agent content is high, the relative amount of positive electrode active material decreases. The improvement effect of the lithium replenishment agent on the energy density of the battery cell is insufficient to compensate for the impact of the reduced amount of positive electrode active material on the energy density of the battery cell. This indicates that appropriately increasing the amount of lithium replenishment agent is beneficial to further enable the battery cell to have higher volumetric energy density, energy efficiency, and cycle capacity retention rate, thereby further extending the service life of the battery cell.

[0175] As can be seen from Examples 1 and 11, replacing the lithium replenisher in Example 1 with other lithium-rich materials can also enable the battery cell to have high volumetric energy density, energy efficiency and cycle capacity retention, and extend the service life of the battery cell.

[0176] Examples 12, 13, and 14

[0177] The negative electrode and electrolyte in the battery cell are the same as in Example 1, except that the lithium replenishing agent in the positive electrode contains doped elements.

[0178] Example 15, Example 16

[0179] The negative electrode and electrolyte in the battery cell are the same as in Example 1. The difference is that the lithium replenishing agent in the positive electrode contains doped elements, and the type of material coated on the surface of the lithium replenishing agent is different.

[0180] The differences between Examples 12 to 16 are shown in Table 6.

[0181] Table 5

[0182]

[0183] As can be seen from Examples 1 and 12 to 16, introducing appropriate doping elements into the lithium replenishing agent or forming other coating materials on the surface of the lithium replenishing agent can further regulate the energy efficiency or cycle performance of the battery cell, so that the battery cell has both high energy density, energy efficiency and cycle capacity retention, and obtains a longer service life.

[0184] 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, wherein the positive electrode sheet includes a positive active material layer, the positive active material layer includes a positive active material and a lithium supplementing agent, and in the cross section along the thickness direction of the positive electrode sheet, more than 50% of the positive active material particles have a longest diameter smaller than the shortest diameter of the lithium supplementing agent particles. A negative electrode sheet, wherein the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, the volume particle size distribution Dv90 of the negative electrode active material is 15μm-30μm, and the negative electrode active material includes graphite.

2. The battery cell according to claim 1, characterized in that, The OI value of the graphite is 2-5.

3. The battery cell according to claim 1 or 2, characterized in that, The volume average particle size Dv50 of the graphite is 6μm-12μm.

4. The battery cell according to claim 1 or 2, characterized in that, The lithium supplement includes Li x M1 y O z , Wherein, 1≤x≤6, 1≤y≤6, 2≤z≤12, and M1 includes one or more of the elements Na, Ni, Co, Mn, Al, and Fe.

5. The battery cell according to claim 1 or 2, characterized in that, The lithium supplement includes Li2NiO2 and / or Li5FeO4.

6. The battery cell according to claim 1 or 2, characterized in that, The lithium supplement includes Li n NiO m and / or Li p FeO q , where 0≤n≤2, 0<m≤2, 0<p≤5, 0<q≤4.

7. The battery cell according to claim 1 or 2, characterized in that, The lithium supplement includes NiO. m and / or Li p FeO q , where 0 < m ≤ 2, 0 < p ≤ 1, 0 < q ≤ 2.

8. The battery cell according to claim 1 or 2, characterized in that, At least a portion of the surface of the lithium replenishing agent is provided with a coating layer, the coating layer comprising one or more of the elements C, Al, Zr, P, and S.

9. The battery cell according to claim 8, characterized in that, The coating layer includes one or more of the following: carbon materials, aluminum oxides, zirconium oxides, lithium phosphides, and lithium sulfides.

10. The battery cell according to claim 1 or 2, characterized in that, The lithium replenishing agent also includes doping elements, which include one or more of Al, Zr, and B.

11. The battery cell according to claim 10, characterized in that, Based on the total mass of the lithium replenishing agent, the contents of Al, Zr and B elements in the lithium replenishing agent are independently 50ppm-1000ppm.

12. The battery cell according to claim 1 or 2, characterized in that, The compaction density of the positive electrode active material layer is 2.1 g / cm³. 3 -2.5g / cm 3 .

13. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the positive electrode active material layer is 0.25g / 1540.25mm. 2 -0.3g / 1540.25mm 2 .

14. The battery cell according to claim 1 or 2, characterized in that, The compaction density of the negative electrode active material layer is 1.2 g / cm³. 3 -1.5g / cm 3 .

15. The battery cell according to claim 1 or 2, characterized in that, The single-sided coating weight of the negative electrode active material layer is 0.12 g / 1540.25 mm. 2 -0.15g / 1540.25mm 2 .

16. The battery cell according to claim 1 or 2, characterized in that, Also includes: The electrolyte includes a solvent comprising cyclic carbonates and linear carbonates, wherein, 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.

17. The battery cell according to claim 16, characterized in that, The electrolyte also includes a lithium salt, the concentration of which is 0.6 mol / L to 1.2 mol / L.

18. The battery cell according to claim 16, characterized in that, The electrolyte also includes a lithium salt, the concentration of which is 0.7 mol / L to 1 mol / L.

19. The battery cell according to claim 17, characterized in that, The electrolyte also includes fluoroethylene carbonate and vinylene carbonate.

20. The battery cell according to claim 19, characterized in that, The fluoroethylene carbonate has a mass content of 0.1%-0.2% in the electrolyte, and the vinylene carbonate has a mass content of 1%-1.5% in the electrolyte.

21. The battery cell according to claim 1 or 2, characterized in that, Also includes: A separating membrane, the separating membrane comprising a base membrane, wherein at least one side of the base membrane is provided with a coating.

22. The battery cell according to claim 21, characterized in that, The thickness of the isolation membrane is 7μm-14μm.

23. The battery cell according to claim 21, characterized in that, The thickness of the isolation membrane is 10μm-12μm.

24. The battery cell according to claim 1 or 2, characterized in that, The positive electrode active material includes a polyanionic positive electrode active material.

25. The battery cell according to claim 1 or 2, characterized in that, The positive electrode active material layer further includes a conductive agent, which includes conductive carbon black and / or carbon nanotubes.

26. The battery cell according to claim 1 or 2, characterized in that, The positive electrode active material includes lithium iron phosphate materials.

27. A battery device, characterized in that, The battery device includes the battery cell of any one of claims 1-26, and the battery device includes at least one of the battery module, battery pack, and energy storage device.

28. An electrical appliance, characterized in that, Includes a battery cell according to any one of claims 1-26 or a battery device according to claim 27, wherein the battery cell or the battery device is used to provide electrical energy.

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