Battery cell, battery device and electric device

Abstract

The invention discloses a battery cell, a battery device and a power utilization device. The battery monomer comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive active material layer, the positive active material layer comprises a positive active material and a lithium supplement agent, and the positive active material and the lithium supplement agent are arranged along the tangent plane of the thickness direction of the positive pole piece. The longest diameter of the positive electrode active material particles with the number ratio of more than 50% is smaller than the shortest diameter of the lithium supplement agent particles; the negative electrode plate 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 has relatively high energy efficiency and relatively long service life.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to battery cells, battery devices and electrical devices. Background Art

[0002] Secondary 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. With the development of current society, people's requirements for batteries are getting higher and higher, such as high energy efficiency or long service life. Summary of the invention

[0003] In view of the technical problems existing in the background technology, the present application provides a battery cell, aiming to obtain high energy efficiency and long service life.

[0004] In order to achieve the above object, in a first aspect of the present application, a battery cell is provided, comprising:

[0005] A positive electrode sheet, the positive electrode sheet comprising a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material and a lithium supplement, wherein along a section in a thickness direction of the positive electrode sheet, more than 50% of the positive electrode active material particles have a longest diameter that is smaller than the shortest diameter of the lithium supplement particles;

[0006] A negative electrode plate, the negative electrode plate 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 μm-30 μm, and the negative electrode active material comprises graphite.

[0007] The battery cell of the first aspect of the present application has at least the following beneficial effects: by designing the positive electrode plate and the negative electrode plate at the same time, so that the longest diameter of the positive electrode active material particles and the shortest diameter of the lithium supplement agent particles meet the above range, and with the negative electrode active material particles whose volume particle size distribution Dv90 meets the above range, it is possible to improve the uniformity of lithium ion release from the positive electrode plate on the basis of positive electrode lithium supplement, and at the same time enable the lithium ions released from the positive electrode to be quickly and evenly embedded in the negative electrode plate, and reduce the side reactions of the negative electrode, thereby reducing the risk of lithium plating in the negative electrode plate, improving the lithium supplement effect and kinetic performance of the battery, so that the battery has both high energy efficiency and long service life.

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

[0009] In some embodiments of the present application, the volume average particle size Dv50 of the graphite is 6 μm-12 μm, which is beneficial to shorten the transmission path of lithium ions in the graphite phase and improve the dynamic performance of the battery.

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

[0011] In some embodiments of the present application, the lithium supplement agent includes Li2NiO2 and / or Li5FeO4, thereby achieving a better lithium supplement effect.

[0012] In some embodiments of the present application, the lithium supplement comprises 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 the present application, the lithium supplement comprises NiO m and / or Li p FeO q , where 0<m≤2, 0<p≤1, 0<q≤2.

[0014] In some embodiments of the present application, at least part of the surface of the lithium supplement agent is provided with a coating layer, and the coating layer includes one or more of the elements C, Al, Zr, P, and S. This can not only improve the air stability of the lithium supplement agent, reduce the generation of lithium impurities on its surface, but also improve its kinetic performance and facilitate lithium removal.

[0015] In some embodiments of the present application, the coating layer includes one or more of carbon material, aluminum oxide, zirconium oxide, lithium phosphide, and lithium sulfide.

[0016] In some embodiments of the present application, the lithium supplement agent further includes a doping element, and the doping element includes one or more of Al, Zr, and B. This is beneficial to reducing the decomposition voltage of the lithium supplement agent, improving the decomposition ability of the lithium supplement agent, so that it can play a greater role in capacity compensation, and is also beneficial to stabilizing the crystal structure of the lithium supplement agent after decomposition, reducing the dissolution of transition metals and possible side reactions with the electrolyte.

[0017] In some embodiments of the present application, based on the total mass of the lithium supplement, the content of the Al element, the Zr element, and the B element in the lithium supplement is independently 50 ppm-1000 ppm.

[0018] In some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.1 g / cm 3 -2.5g / cm 3 This is beneficial to the infiltration of the electrolyte and improves the ion conductivity.

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

[0020] In some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.2 g / cm 3 -1.5g / cm 3 This is beneficial to the infiltration of the electrolyte and improves the ion conductivity.

[0021] In some embodiments of the present 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 the polarization of the pole piece and improve the dynamic performance of the battery.

[0022] In some embodiments of the present application, the battery cell further comprises: an electrolyte, the electrolyte comprises a solvent, the solvent comprises 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%. Thus, it is beneficial to improve the stability of the electrolyte and improve the dynamic performance of the battery.

[0023] In some embodiments of the present application, the electrolyte further comprises a lithium salt, and the concentration of the lithium salt is 0.6 mol / L-1.2 mol / L, and can be optionally 0.7 mol / L-1 mol / L, which is conducive to obtaining a higher ionic conductivity and improving the battery kinetics performance.

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

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

[0026] In some embodiments of the present application, the battery cell further includes: an isolation membrane, the isolation membrane includes a base membrane, and at least one side of the base membrane is provided with a coating.

[0027] In some embodiments of the present application, the thickness of the isolation film is 7 μm-14 μm, which is conducive to taking into account both the puncture strength of the isolation film and the energy density of the battery.

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

[0029] In some embodiments of the present application, the positive electrode active material includes a polyanionic positive electrode active material, which is beneficial to improve the cycle life of the battery.

[0030] In some embodiments of the present application, the positive electrode active material layer further includes: a conductive agent, wherein the conductive agent includes conductive carbon black and / or carbon nanotubes. This not only improves the conductivity of the electrode, but also facilitates the decomposition of the lithium supplement and the improvement of the battery dynamics.

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

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

[0033] The third aspect of the present application provides an electrical device, which includes: the battery cell described in the first aspect of the present application or the battery device described in the second aspect of the present application, and the battery cell or the battery device is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0037] Figure 3It is a schematic structural diagram of a battery cell according to one embodiment of the present application.

[0038] Figure 4 It is a schematic structural diagram of a battery module according to one embodiment of the present application.

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

[0040] Figure 6 yes Figure 5 Exploded diagram of .

[0041] Figure 7 It is a schematic diagram of an embodiment of an electrical device using the battery device of the present application as a power source.

[0042] Description of reference numerals:

[0043] 1: Battery cell; 2: Battery module; 3: Battery pack; 4: Upper box; 5: Lower box; 10: Lithium supplement; 11: Coating layer. DETAILED DESCRIPTION

[0044] The present application is further described below in conjunction with specific implementations. It should be understood that these specific implementations are only used to illustrate the present application and are not used to limit the scope of the present application.

[0045] Reference to "embodiments" in this application 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 in this application may be combined with other embodiments.

[0046] "Scope" disclosed in the present application is defined in the form of lower limit and / or upper limit, and a given range is defined by selecting a lower limit and / or an upper limit, and the selected lower limit and / or the rear upper limit define the boundary of a special range. The scope defined in this way can be including or excluding end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope that is not clearly recorded, and any lower limit can be combined with other lower limits to form a scope that is not clearly recorded, and any upper limit can be combined with any other upper limit to form a scope that is not clearly recorded. In addition, each separately disclosed point or single numerical value itself can be used as a lower limit or upper limit and any other point or single numerical value combination or with other lower limits or upper limits to form a scope that is not clearly recorded.

[0047] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0048] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form a new technical solution, and such a technical solution should be deemed to be included in the disclosure of the present application.

[0049] If there is no special explanation, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps S1 and S2, which means that the method may include steps S1 and S2 performed sequentially, or may include steps S2 and S1 performed sequentially. For example, the method may also include step S3, which means that step S3 may be added to the method in any order. For example, the method may include steps S1, S2 and S3, or may include steps S1, S3 and S2, or may include steps S3, S1 and S2, etc.

[0050] If there is no special explanation, in this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0051] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0052] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and any variations thereof are intended to cover non-exclusive inclusions. Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0053] With the continuous advancement of the green environmental protection theme, the application of batteries has penetrated into all aspects of life, including vehicles, electronic equipment, energy storage devices, etc. However, with the continuous promotion of battery applications, people's requirements for batteries are getting higher and higher. For example, taking lithium-ion batteries as an example, secondary batteries with high energy efficiency and long service life have become an important research direction in the battery industry. In the existing battery system, there is a solution that uses lithium iron phosphate positive electrode active materials with graphite negative electrodes to improve the cycle stability and reliability of the battery and extend the battery life. However, this solution has a low initial efficiency of graphite in the early stage and the need to consume active lithium in the SEI film stabilization process, resulting in a rapid capacity decay in the early stage, making it difficult to better meet customers' increasing demand for long service life.

[0054] The present application aims to develop a battery cell with both high energy efficiency and long service life. The battery cell of the present application adds a lithium supplement to the positive electrode plate, and comprehensively controls the particle size relationship between the lithium supplement and the positive electrode active material in the positive electrode plate, as well as the volume particle size distribution of the negative electrode active material in the plate, to develop a battery cell with high energy density and long service life.

[0055] In the positive electrode plate of the present application, the positive electrode active material layer includes a positive electrode active material and a lithium supplement agent. In the cross-section along the thickness direction of the positive electrode plate, more than 50% of the positive electrode active material particles have a longest diameter that is smaller than the shortest diameter of the lithium supplement agent particles; in the negative electrode plate, the volume particle size distribution Dv90 of the negative electrode active material is 15μm-30μm, and the negative electrode active material includes graphite.

[0056] The introduction of lithium supplement agents can improve the initial effect and cycle performance of battery cells, and increase the cycle life and service life of battery cells. However, if the lithium supplement agent is unevenly dispersed in the positive electrode active material layer, it is easy to cause uneven lithium release from the positive electrode sheet, increasing the risk of lithium precipitation and dendrite formation at the negative electrode; at the same time, if the lithium ions released from the positive electrode sheet cannot be quickly and evenly embedded in the negative electrode active material layer, it will also weaken the kinetic performance of the battery and increase the risk of lithium precipitation and dendrite formation. In this application, by appropriately increasing the particle size of the lithium supplement agent particles so that the longest diameter of more than half of the positive electrode active material particles is smaller than the shortest diameter of the lithium supplement agent particles, the uniformity of the dispersion of the lithium supplement agent in the positive electrode active material layer can be effectively improved, so that the lithium ions can be evenly released during the lithium removal process of the positive electrode sheet, and it is not easy to cause excessive local lithium ion concentration due to the release of lithium ions in agglomeration, thereby increasing the risk of lithium precipitation at the negative electrode. At the same time, if the particle size of the negative electrode active material particles is large, the lithium insertion path of lithium ions will be increased, and the difficulty of lithium insertion will be increased. If the particle size of the negative electrode active material particles is small, its surface activity is high and the risk of side reactions is also high. By matching the negative electrode active material particles with a volume particle size distribution Dv90 of 15μm-30μm, the lithium ions released from the positive electrode can be quickly and evenly embedded in the negative electrode sheet, and the side reactions of the negative electrode can be reduced. As a result, the battery monomer has both high energy efficiency, good cycle performance and long service life.

[0057] The battery cell disclosed in the embodiments of the present application can be used in electrical equipment that uses the battery cell or a battery device having the battery cell as a power source or various energy storage systems that use the battery cell or a battery device having 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, and the like. 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, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0058] The first aspect of the present application provides a battery cell, which includes: a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material and a lithium supplement, and along the cross section of the thickness direction of the positive electrode sheet, there are more than 50% of the positive electrode active material particles whose longest diameter is smaller than the shortest diameter of the lithium supplement particles; 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.

[0059] In order to improve the cycle performance of the battery and obtain a long cycle life and a long service life, it is usually necessary to introduce a lithium supplement. The lithium supplement provides additional lithium during the first charging process, compensates for the lithium consumed by the SEI film, and improves the first effect and cycle performance. However, if the lithium supplement is unevenly distributed in the positive electrode active material layer, it is easy to cause uneven lithium release, increase the risk of lithium precipitation and dendrite formation, and not only affect the kinetic performance of the battery, but also affect the energy efficiency and cycle life of the battery. To solve this problem, it can be achieved by regulating the relative particle size relationship between the lithium supplement and the positive electrode active material particles. Compared with the method of mixing lithium supplement particles and positive electrode active material particles of equivalent particle size, the lithium supplement and the positive electrode active material particles form a large and small particle size grading, which can effectively improve the dispersion uniformity of the lithium supplement in the positive electrode active material layer. The particle size of the positive electrode active material (such as lithium iron phosphate) particles can usually be very small, and the processing difficulty of the lithium supplement with smaller particles is relatively large, and the risk of agglomeration between the lithium supplement particles with small particle size and the positive electrode active material particles with small particle size is also large, which also increases the risk of uneven lithium ion release. In the present application, by appropriately increasing the particle size of the lithium supplement agent particles so that the longest diameter of more than half of the positive electrode active material particles is smaller than the shortest diameter of the lithium supplement agent particles, the lithium supplement agent and the positive electrode active material particles can form a size grading, effectively improving the dispersion uniformity of the lithium supplement agent in the positive electrode active material layer, and thus enabling the lithium ions to be uniformly released during the lithium removal process of the positive electrode plate, and it is not easy to cause excessive local lithium ion concentration due to the release of lithium ions in agglomeration, thereby increasing the risk of lithium deposition at the negative electrode.

[0060] At the same time, if the lithium ions released from the positive electrode sheet cannot be quickly and evenly embedded in the negative electrode active material layer, the kinetic performance of the battery will be weakened, increasing the risk of negative electrode lithium plating and dendrite formation. On this basis, in order to enable the lithium ions released from the positive electrode sheet to be quickly and evenly embedded in the negative electrode sheet, negative electrode active particles with a suitable particle size range are required. If the particle size of the negative electrode active material particles is large, the lithium insertion path of the lithium ions will be increased, the difficulty of lithium insertion will be increased, and it will be unfavorable to improve the battery's kinetic performance and reduce the risk of lithium plating. If the particle size of the negative electrode active material particles is small, its surface activity is high, the risk of side reactions is also high, and it is easy to deteriorate the battery's energy efficiency, cycle life and kinetic performance. In the present application, on the basis of ensuring that the particle size of the positive electrode active material and the lithium replenisher in the positive electrode plate meets the above-mentioned range, the negative electrode active material particles with a volume particle size distribution Dv90 of 15μm-30μm are matched, which can not only improve the uniformity of lithium ion extraction on the basis of positive electrode lithium replenishment, but also enable the lithium ions extracted from the positive electrode to be quickly and evenly embedded in the negative electrode plate, and reduce the side reactions of the negative electrode, thereby improving the lithium replenishment effect and kinetic performance of the battery, so that the battery has higher energy efficiency, better cycle performance and longer service life.

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

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

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

[0064] In the present application, the shortest diameter of the lithium supplement agent particles and the longest diameter of the positive electrode active material particles are defined as follows: the positive electrode sheet including the lithium supplement agent particles and the positive electrode active material particles is cut along the thickness direction of the sheet to expose the cross section of the positive electrode active material layer, and the cross section of the positive electrode active material layer is subjected to a scanning electron microscope (SEM) test to determine the shortest diameter of the lithium supplement agent particles and the longest diameter of the positive electrode active material particles. Specifically, the shortest diameter of the lithium supplement agent refers to the shortest straight line passing through the center point of the lithium supplement agent and extending to the periphery of the particle, and the longest diameter of the positive electrode active material refers to the longest straight line passing through the center point of the positive electrode active material particle and extending to the periphery of the particle. In the present application, the shortest diameter of the lithium supplement agent particles and the longest diameter of the positive electrode active material particles can be tested by the following method: select the lithium supplement agent particles in the cross section of the positive electrode active material layer and measure the shortest diameter of the lithium supplement agent particles; select the positive electrode active material particles in the cross section of the positive electrode active material layer and measure the longest diameter of each of the multiple positive electrode active material particles.

[0065] In the present application, the positive electrode active material layer can be qualitatively analyzed in combination with one or more conventional instruments and conventional methods such as scanning electron microscope, EDS spectrometer, X-ray diffractometer, inductively coupled plasma emission spectrometer, etc. to determine whether there is a lithium supplement in the positive electrode active material layer and the type of lithium supplement. For example, in the positive electrode active material layer, in addition to the different elemental composition, the lithium supplement and the positive electrode active material particles usually have differences in size and particle morphology, and the lithium supplement does not completely disappear after delithiation, but residual elements and particle skeletons will remain. The lithium supplement usually shrinks in volume after delithiation, so that a certain gap is formed between the residual particle skeleton and the surrounding area (reference Figure 2 As shown, Figure 2This is a scanning electron microscope image of a cross section of a positive electrode sheet in a battery cell in another embodiment of the present application, which shows a microscopic morphology of a lithium supplement 10 having a coating layer 11 after delithiation, and a gap is formed between the particle skeleton of the lithium supplement 10 and the coating layer 11 on its surface in the later stage of delithiation). Based on the above differences, the possible locations of the lithium supplement in the section of the positive electrode sheet along its thickness direction can be quickly screened in the scanning electron microscope test, and the lithium supplement particles and the positive electrode active material particles can be distinguished by elemental composition in combination with EDS energy spectrum analysis, and then the size difference between the particle size of the positive electrode active particles and the particle size of the lithium supplement particles can be compared. For another example, the surface roughness of the positive electrode active material particles and the lithium supplement particles is usually different, and this difference can also be combined to quickly screen the possible locations of the lithium supplement in the scanning electron microscope test. For another example, lithium supplements usually do not completely remove lithium after formation. The diffraction peak changes (such as peak position, peak intensity, etc.) of the XRD spectrum of the positive electrode active material layer to be tested before and after charging and discharging can be compared to determine in advance whether a lithium supplement is added to the positive electrode plate and the type of lithium supplement added. In addition, due to the difference in lithium content between the lithium supplement and the positive electrode active material itself and the different lithium deintercalation efficiency during charging and discharging, their lithium content in the full charged and discharged state is also different. For example, in the charged state, the lithium deintercalation efficiency of the lithium supplement in the positive electrode plate is usually lower than that of the positive electrode active material, which can be characterized and distinguished by FIB (focused ion beam) combined with SIMS (secondary ion mass spectrometry) testing; and in a charging and discharging process, the lithium supplement and the positive electrode active material have obvious differences in volume expansion between material particles due to the difference in lithium deintercalation efficiency, which can be observed and characterized by in situ confocal.

[0066] In the present application, the particle size of the negative electrode active material in the negative electrode active material layer can be tested in combination with conventional instruments such as a particle size analyzer (such as a laser particle size analyzer, etc.). For example, the negative electrode active material layer and the negative electrode current collector can be separated by a wet method and / or an ultrasonic method to obtain the negative electrode active material particles.

[0067] In the battery cell of the present application, in the cross-section along the thickness direction of the positive electrode plate, it is required that the longest diameter of the positive electrode active material particles, which accounts for more than 50%, is smaller than the shortest diameter of the lithium supplement agent particles. This can also reserve design space for further improving the energy density and service life of the battery cell. For example, a small amount of large-particle-size positive electrode active material particles can be combined with the above-mentioned positive electrode active material particles whose longest diameter is smaller than the shortest diameter of the lithium supplement agent particles to form a large and small particle size grading to further improve the energy density of the battery and extend the service life of the battery.

[0068] In some embodiments of the present 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 combination with XRD testing. A low OI value of graphite means that there are many end faces for lithium ion extraction / embedding in the graphite, which is conducive to lithium ion embedding and improves the kinetic performance. Therefore, making the OI value of graphite meet the given range is conducive to further improving the kinetic performance of the battery.

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

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

[0071] In some embodiments of the present application, the lithium supplement may include Li x M1 y O z , wherein 1≤x≤6, 1≤y≤6, 2≤z≤12, M1 may include one or more of Na element, Ni element, Co element, Mn element, Al element, and Fe element. Exemplarily, the value of x may be 1, 2, 3, 4, 5 or 6, or may be a range consisting of any of the above values. Optionally, the value of x may be 1<x≤6, such as 2≤x≤5; the value of y may be 1, 2, 3, 4, 5 or 6, or may be a range consisting of any of the above values. The value of z may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, or may be a range consisting of any of the above values. Optionally, the value of z may be 2≤z≤8. wherein Li x M1 y O z The charge capacity is 1 to 5 times that of the multi-element positive electrode active material, which can provide additional lithium during the first charge. In addition, it is also beneficial to store additional lithium in the negative electrode to extend the battery life. x M1 y O z, which can achieve a good lithium supplementation effect. It is understandable that during the formation and use of the battery, as the lithium supplementation process proceeds, the lithium in the lithium supplement will be partially or completely released, causing the lithium supplement to change from the initial state to a partially or completely de-lithiumated state, at which time x≤1 and / or z≤2 will occur.

[0072] In some embodiments of the present application, the lithium supplement may include but is not limited to Li2NiO2 and / or Li5FeO4. In the manufacturing process of the positive electrode sheet, Li2NiO2 and / or Li5FeO4 may be directly doped into the positive electrode active material layer. Li2NiO2 can form LiNiO2 with lithium deintercalation ability after lithium removal. LiNiO2 can become Li in the lithium removal state. 1-x1 NiO2, 0≤x1≤1, can be restored to LiNiO2 in the lithium-embedded state; Li5FeO4 has a strong lithium replenishment ability, and the LiFeO2 formed after lithium removal does not cause obvious side reactions. Therefore, the use of Li2NiO2 and / or Li5FeO4 as a lithium replenisher can achieve a better capacity compensation effect. Exemplarily, the lithium replenisher can be Li2NiO2, which can provide considerable lithium replenishment capacity only by changing the valence of Ni atoms at a lower potential, without the need to provide capacity through the valence change of oxygen atoms, which can reduce the risk of the electrolyte being oxidized by oxygen free radicals.

[0073] In some embodiments of the present application, the lithium supplement may include an initial state, a partially delithiated state, and a completely delithiated state. When the lithium supplement changes from the initial state to the partially delithiated state and the completely delithiated state, the lithium supplement 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, etc., or can be a range consisting of any of the above values; the value of m can be 0.5, 1, 1.5 or 2, etc., or can be a range consisting of any of the above values; the value of p can be 0.5, 1, 2, 3, 4 or 5, etc., or can be a range consisting of any of the above values; the value of q can be 1, 2, 3 or 4, etc., or can be a range consisting of any of the above values. Exemplarily, taking the lithium supplement whose initial state is Li2NiO2 as an example, when the lithium in Li2NiO2 is partially released, the lithium supplement Li n NiO m The composition may include one or more of the components of 0<n<1, n=1, 1<n<2; when the lithium in Li2NiO2 is completely removed, the lithium supplement Li n NiO m The composition may include NiO mTaking the lithium supplement agent with the initial state of Li5FeO4 as an example, when the lithium in Li5FeO4 is partially released, the lithium supplement agent Li p FeO q The composition may include one or more of the components of 1<p<2, 2≤p<3, 3≤p<4, 4≤p<5; when the lithium in Li5FeO4 is completely removed, the lithium supplement Li p FeO q The composition may include LiFeO2. Under factors such as polarization, LiFeO2 may continue to delithiate, resulting in the appearance of Li with p < 1. p FeO q Component.

[0074] In some embodiments of the present application, when the lithium supplement agent changes from an initial state to a completely de-lithiated state, the lithium supplement 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 can be a range of any of the above values; the value of p can be 0.2, 0.5, 0.8 or 1, or can be a range of any of the above values; the value of q can be 0.2, 0.5, 1, 1.5 or 2, or can be a range of any of the above values. Exemplarily, taking the lithium supplement whose initial state is Li2NiO2 and Li5FeO4 as an example, when the lithium supplement is completely de-lithiated, the lithium supplement after de-lithiation can include but is not limited to NiO and / or LiFeO2.

[0075] In some embodiments of the present application, at least part of the surface of the lithium supplement may be provided with a coating layer, and the coating layer may include one or more of C element, Al element, Zr element, P element, and S element. The types of elements in the coating layer of the lithium supplement may be qualitatively analyzed in combination with characterization methods such as EDS spectrum analysis. The air stability of the lithium supplement is generally poor. Taking Li2NiO2 as an example, it has strong alkalinity and is easy to react with water and CO2. The formation of a coating layer on the surface of the lithium supplement can improve its air stability and reduce the generation of lithium-containing impurities on the surface. On the other hand, it can also improve the ion conductivity of the lithium supplement, improve the transmission efficiency of lithium ions, and improve the kinetic performance, which is further beneficial to delithiation and improve the lithium supplement capacity.

[0076] In some embodiments of the present 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 in combination with one or more analysis methods such as EDS energy spectrum analysis and X-ray diffraction. Among them, the lithium supplement agent has relatively poor conductivity. Carbon materials, aluminum oxides, and zirconium oxides as coating layer materials are beneficial to improving the air stability of the lithium supplement agent and reducing the generation of lithium-containing impurities on the surface. In addition, the use of carbon materials as coating layer materials is beneficial to improving the conductivity of the positive electrode plate; using fast ion conductors, such as lithium phosphides or lithium sulfides (exemplarily, lithium phosphate or lithium sulfate, etc.) as coating layer materials is beneficial to improving the lithium ion transmission rate and improving the kinetic performance, which is further beneficial to delithiation and improving the lithium supplement capacity. This is conducive to further improving the electrochemical performance of the battery.

[0077] In some embodiments of the present application, the lithium supplement agent may further include a doping element, and the doping element may include one or more of Al, Zr, and B. Doping one or more of Al, Zr, and B in the lithium supplement agent is beneficial to reducing the decomposition voltage of the lithium supplement agent, improving the decomposition ability of the lithium supplement agent, so that it can play a greater role in capacity compensation, and is also beneficial to stabilizing the crystal structure of the lithium supplement agent after decomposition, reducing the dissolution of transition metals and possible side reactions with the electrolyte, thereby further enabling the battery to have both higher energy efficiency and cycle life.

[0078] In some embodiments of the present application, based on the total mass of the lithium supplement, the content of the Al element, the Zr element, and the B element in the lithium supplement can be independently 50ppm-1000ppm, such as 50ppm, 200ppm, 500ppm, 800ppm or 1000ppm, etc.

[0079] In some embodiments of the present application, the positive electrode active material layer may further include: a conductive agent, which may include conductive carbon black and / or carbon nanotubes. The conductivity of the lithium supplement is poor, and the conductivity of carbon nanotubes is better than that of conductive carbon black, but the cost is relatively high. Using zero-dimensional conductive carbon black and one-dimensional carbon nanocomposites as conductive agents is not only conducive to the dispersion of carbon nanotubes, but also to the formation of a better conductive network and the realization of better conductive properties. In this way, not only the conductive properties of the pole piece can be improved, but also the decomposition of the lithium supplement and the improvement of the battery dynamics can be facilitated.

[0080] In some embodiments of the present application, the positive electrode active material may include a polyanion positive electrode active material. Optionally, the positive electrode active material may include but is not limited to lithium iron phosphate positive electrode active materials. It is understood that lithium iron phosphate 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 polyanion 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, M2 can be a transition metal element, optionally, M2 can include one or more of V, Cr, Ni, Co, Cu, Al, Zr, etc., illustratively, for example, the value of x2 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1 or 1.2, etc., or can be a range consisting of any of the above values; the value of a can be 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc., or can be a range consisting of any of the above values; the value of b can be 0, 0.1, 0.2, 0.3, 0.4 or 0.5, etc., or can be a range consisting of any of the above values; the value of c can be 0, 0.02, 0.05, 0.08 or 0.1, etc., or can be a range consisting of any of the above values. The positive electrode active material layer can be qualitatively and quantitatively analyzed by combining one or more conventional instruments and methods such as scanning electron microscope, EDS spectrometer, X-ray diffractometer, inductively coupled plasma emission spectrometer, etc. to determine the type of positive electrode active material. Compared with ternary positive electrode active materials, lithium iron phosphate positive electrode active materials have a more stable crystal structure, can achieve better cycle stability, and improve the cycle life and service life of the battery.

[0081] In some embodiments of the present application, the compaction density of the positive electrode active material layer can be 2.1 g / cm 3 -2.5g / cm 3 , for example, it can be 2.1 g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 or 2.5g / cm 3 Etc. Properly reducing the compaction density of the positive electrode active material layer is conducive to the infiltration of the electrolyte and improves the dynamic performance of the battery. When the compaction density of the positive electrode active material layer meets the given range, the dynamic performance of the battery can be improved while taking into account the battery energy density.

[0082] In some embodiments of the present application, the single-sided coating weight of the positive electrode active material layer can be 0.25 g / 1540.25 mm2 -0.3g / 1540.25mm 2 , such as 0.25g / 1540.25mm 2 , 0.28g / 1540.25mm 2 or 0.3g / 1540.25mm 2 Etc. This is beneficial to reduce the polarization of the pole piece and improve the dynamic performance of the battery.

[0083] In some embodiments of the present application, the compaction density of the negative electrode active material layer can be 1.2 g / cm 3 -1.5g / cm 3 , for example, 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 or 1.5g / cm 3 Etc. Properly reducing the compaction density of the negative electrode active material layer is conducive to the infiltration of the electrolyte and improves the dynamic performance of the battery. When the compaction density of the negative electrode active material layer meets the given range, the dynamic performance of the battery can be improved while taking into account the battery energy density.

[0084] In some embodiments of the present 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 , such as 0.12g / 1540.25mm 2 , 0.13g / 1540.25mm 2 , 0.14g / 1540.25mm 2 or 0.15g / 1540.25mm 2 This helps reduce the polarization of the pole piece and improve the dynamic performance of the battery.

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

[0086] In some embodiments, the compaction density of the positive or negative active material layer can be the compaction density corresponding to the battery power of about 0% SOC, and the 0% SOC state means: the battery cell is charged to 3.65V at a constant current of 1 / 3C at room temperature, charged to a current of 0.05C at a constant voltage of 3.65V, and then discharged to a state corresponding to 2.5V at 1 / 3C.

[0087] Typically, the positive electrode sheet also includes a positive electrode current collector, and the positive electrode active material layer is disposed on at least a portion of the surface of at least one side of the positive electrode current collector. The positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode 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 the present application, the positive electrode active material layer may also optionally include at least one of a binder and other optional auxiliary agents. Wherein, the binder and auxiliary agent can be conventionally selected in the art, for example, the binder may include but not limited to 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) One or more. These materials can be obtained through commercial channels.

[0089] Typically, the negative electrode plate also includes a negative electrode current collector, and the negative electrode active material layer is 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 may be a conventional metal foil or a composite current collector (for example, a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector may be a metal foil such as copper foil.

[0090] In some embodiments of the present application, the negative electrode active material layer generally 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. The present application does not specifically limit the types of negative electrode sheet conductive agents and binders, and 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 (water-based acrylic resin) and carboxymethyl cellulose (CMC). In addition, the negative electrode active material layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC) and the like. However, the present application is not limited thereto, and the present application may also use other materials that can be used as thickeners for negative electrode sheets of lithium-ion batteries.

[0091] In some embodiments of the present application, the battery cell further includes: an electrolyte, the electrolyte includes a solvent, the solvent may include a cyclic carbonate and a linear carbonate, based on the total mass of the electrolyte, the mass percentage of the cyclic carbonate may be 15%-25%, and the mass percentage of the linear carbonate may be 50%-70%. For example, based on the total mass of the electrolyte, the mass percentage of the cyclic carbonate may be 15%, 18%, 20%, 22% or 25%, etc.; the mass percentage of the linear carbonate may be 50%, 55%, 60%, 65% or 70%, etc. Appropriately reducing the content of the cyclic carbonate is conducive to reducing the viscosity of the electrolyte and increasing the lithium ion transmission rate; appropriately increasing the content of the cyclic carbonate is conducive to increasing the dielectric constant of the electrolyte and reducing the migration resistance of lithium ions in the electrolyte. Therefore, making the composition of the electrolyte meet the given range is conducive to improving the stability of the electrolyte and improving the kinetic performance of the battery.

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

[0093] In some embodiments of the present 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 the present application, the electrolyte may further include a lithium salt, and the concentration of the lithium salt may be 0.6mol / L-1.2mol / L, for example, 0.6mol / L, 0.8mol / L, 1mol / L, 1.2mol / 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 bisoxalate borate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonate, and lithium bis(trifluoromethylsulfonyl)imide. Properly increasing the concentration of the lithium salt can increase the number of lithium ions and improve the ionic conductivity; properly reducing the concentration of the lithium salt is conducive to reducing the viscosity of the electrolyte, improving the ion transfer efficiency and ionic conductivity. Thus, making the lithium salt concentration meet the given range is conducive to obtaining a higher ionic conductivity and improving the battery kinetics. Optionally, the concentration of the lithium salt may be 0.7mol / L-1mol / L.

[0095] In some embodiments of the present application, the electrolyte may also optionally include additives that can improve certain properties of the battery, for example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, additives that can improve battery overcharge performance, additives that improve battery high temperature performance, or additives that improve battery low temperature performance, etc. Exemplarily, the additives may include but are not limited to FEC (fluoroethylene carbonate) and / or VC (vinyl 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 vinyl 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 conducive to further improving battery performance.

[0096] In some embodiments of the present application, the electrolyte may include one or more of a phosphorus-containing additive, a fluorine-containing additive, and a sulfur-containing additive, thereby facilitating further improvement of battery performance.

[0097] In some embodiments of the present application, the battery cell may further include: a separator. Optionally, the separator may be any known porous structure membrane with electrochemical stability and mechanical stability according to 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, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0098] In some embodiments, the separator may be an uncoated separator, which is not only low in cost but also helps to make lithium ions conduct more smoothly and improve ion conductivity.

[0099] In some embodiments, the isolation film may include a base film, and at least one side of the base film may be provided with a coating layer.

[0100] Exemplarily, a ceramic coating containing an inorganic oxide may be provided on the side of the base film facing the positive electrode plate. Exemplarily, the inorganic oxide may include but is not limited to boehmite. Optionally, the ceramic coating may also include a binder, and the binder may include but is not limited to an acrylate binder. Providing a ceramic coating containing an inorganic oxide is beneficial to improving the oxidation resistance and high temperature stability of the separator.

[0101] Exemplarily, a bonding coating may be provided on the side of the base film facing the negative electrode plate, and providing the bonding coating is beneficial to saving internal space of the battery and improving the volume energy density of the battery. Optionally, the bonding coating may include but is not limited to polyvinylidene fluoride (PVDF) and / or polymethyl methacrylate (PMMA).

[0102] In some embodiments of the present application, the thickness of the separator may be 7 μm-14 μm, for example, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm, etc. This is conducive to taking into account both the puncture strength of the separator and the energy density of the battery, reducing the risk of being easily pierced by dendrites due to the small thickness of the separator or reducing the risk of reducing the energy density of the battery due to the large thickness of the separator. Optionally, the thickness of the separator may be 10 μm-12 μm.

[0103] In some embodiments of the present application, after the battery monomer is formed, the carbon content in the organic component is ≥60% based on the carbon content on the surface of the negative electrode plate, and the carbon-containing organic component includes but is not limited to alkyl lithium, alkyl oxide lithium, alkyl ester lithium and other components. The carbon content in the organic component can be obtained by XPS analysis of the carbon element on the surface of the negative electrode plate. Taking Li2NiO2 as an example, when the lithium supplement decomposes, the oxygen changes 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 generate an organic SEI film, thereby enhancing the ionic conductivity and improving the kinetic performance of the battery.

[0104] The embodiments of the present application have no particular restrictions on the shape of the battery cell. For example, in some embodiments of the present application, the battery may be a soft-pack battery, a square battery, or a cylindrical battery. Figure 3 The battery cell 1 is a square structure as an example.

[0105] In some embodiments of the present application, the battery cell may be a cylindrical battery, which may include a shell, and the two ends of the shell are respectively a first end and a second end, and the first end may be connected to the negative electrode plate through the shell wall of the shell located at the first end, and illustratively, the pole ear of the negative electrode plate may be connected to the shell wall of the shell located at the first end through the first current collecting part; the second end may be provided with a cap, and the cap may include a pole, and the pole column may be connected to the positive electrode plate, and illustratively, the pole ear of the positive electrode plate may be connected to the pole column through the second current collecting part. Optionally, the cap may be a steel cap. Providing a cap structure not only facilitates the cylindrical battery to be connected by welding through the current collecting part (such as a collector bar, etc.), but also facilitates the pressure relief after the battery fails, and reduces the safety risks that may be caused by the high-nickel and high-silicon system batteries due to the large gas production due to thermal runaway.

[0106] In some embodiments, the battery cell may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0107] In some embodiments, the outer package may include a shell and a cover plate. The shell 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 has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity.

[0108] The positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly. The electrode assembly is packaged in the receiving cavity. The number of electrode assemblies contained in the battery cell can include one or more, which can be adjusted according to demand.

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

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

[0111] The second aspect of the present application provides a battery device, which includes: the battery cell of the first aspect of the present 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 embodiments, the battery device may be a battery cell, or a battery module or battery pack assembled from battery cells. The battery module or battery pack may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module.

[0113] Figure 4 2 is an example of a battery module 2. Figure 4In the battery module 2, a plurality of battery cells 1 may be arranged in sequence along the length direction of the battery module 2. Of course, they may also be arranged in any other manner. The plurality of battery cells 1 may further be fixed by fasteners. The battery module 2 may also include a housing having a storage space, and the plurality of battery cells 1 are stored in the storage space. In some embodiments, the battery modules may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0114] Figure 5 and 6 The battery pack 3 is used as an example. Figure 5 and 6 The battery pack 3 may include a battery box and a plurality of battery modules 2 disposed in the battery box. The battery box includes an upper box body 4 and a lower box body 5. The upper box body 4 can cover the lower box body 5 and form a closed space for accommodating the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0115] The third aspect of the present application provides an electrical device, which includes: the battery cell of the first aspect of the present application or the battery device of the second aspect of the present application, and the battery cell or the battery device is used to provide electrical energy.

[0116] Specifically, the battery cell or battery device can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops), 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, satellites, and energy storage systems.

[0117] Figure 7 As an example of an electric device, the electric device includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. As another example, the electric device may include a mobile phone, a tablet computer, and a laptop computer. The electric device is usually required to be thin and light, and a battery may be used as a power source.

[0118] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0119] Example 1

[0120] (1) Positive electrode

[0121] The positive electrode current collector aluminum foil is provided with positive electrode active material layers on two surfaces of the aluminum foil which are arranged opposite to each other. The thickness of the aluminum foil is 13 μm. The thickness of the positive electrode active material layers arranged on the two surfaces of the aluminum foil is equal. The single-side 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 95.8% lithium iron phosphate, 2% lithium supplement Li2NiO2 (the surface of the lithium supplement has aluminum oxide), 0.4% conductive carbon black (Super P), and 1.8% binder polyvinylidene fluoride (PVDF).

[0122] (2) Negative electrode

[0123] The negative electrode current collector copper foil is provided with a negative electrode active material layer on two oppositely disposed surfaces of the copper foil, the thickness of the copper foil is 6 μm, the thickness of the negative electrode active material layers disposed on the two surfaces of the copper foil is equal, and the single-side 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 solvents, electrolyte salts 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 proportion of FEC in the electrolyte is 0.15%, and the mass proportion of VC in the electrolyte is 1.2%.

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

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

[0128] Performance Test:

[0129] (1) Energy density test

[0130] At 25°C, the formed battery was 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, and the discharge capacity was recorded as C; after measuring the size of the battery cell, its volume was calculated as V, and its volume energy density was obtained to be 3.22×C / V.

[0131] (2) Energy efficiency test

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

[0133] The energy efficiency of the battery is calculated according to the following formula (%): W d / W c ×100%.

[0134] (3) Cyclic performance test

[0135] At 25°C, let the formed battery stand for 30 minutes, and discharge it to 2.5V at a constant current of 1 / 3C. Then, perform the charge and discharge cycle according to the following steps: let it stand for 5 minutes, charge it to 3.65V at a constant current of 1 / 3C, then charge it at a constant voltage until the current drops to 0.05C, and record the charge capacity at this time as C0; let it stand for 5 minutes; discharge it to 2.5V at a constant current of 1 / 3C. After 450 cycles, record the discharge capacity C0 at the 450th cycle. 450 The capacity retention rate after 450 cycles is calculated according to the following formula:

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

[0137] Comparative Example 1

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

[0139] Comparative Example 2

[0140] The negative electrode sheet and electrolyte in the battery cell are the same as those in Example 1, except that in the positive electrode sheet, only less than 50% of the positive electrode active material particles have the longest diameter smaller than the shortest diameter of the lithium supplement particles in the cross section along the thickness direction of the positive electrode sheet.

[0141] Comparative Example 3, Comparative Example 4

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

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

[0144] Table 1

[0145]

[0146] In combination with Example 1, and Comparative Examples 1 to 4, it can be seen that the battery cell proposed in the present application has both high energy efficiency and cycle capacity retention rate, indicating that the present application uses a lithium supplement in the positive electrode plate and makes the shortest diameter of the lithium supplement particles greater than the longest diameter of more than half of the positive electrode active material particles, and at the same time controls the volume particle size Dv90 of the negative electrode active material graphite within an appropriate range, which can improve the energy density of the battery cell while improving the energy efficiency and cycle performance of the battery cell and extending the service life of the battery cell.

[0147] Example 2, Example 3, Example 4

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

[0149] Example 5

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

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

[0152] Table 2

[0153]

[0154] It can be seen from Example 1, Comparative Examples 3 to 4 and Examples 2 to 5 that appropriately reducing the volume 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 analysis 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 will affect the energy density of the battery cell. Appropriately reducing the volume particle size of the negative electrode active material is not only beneficial to improving the compaction density of the negative electrode active material layer, but also beneficial to improving the deintercalation efficiency of lithium ions in the negative electrode and improving the kinetic performance of the battery cell; when the particle size of the negative electrode active material is small, its specific surface area is large, the activity is high, and the probability of side reactions is also high, which is also easy to affect the energy density of the battery cell. Further, in combination with Examples 4 and 5, it can be seen that the reduction of the OI value of graphite is also beneficial to improving the energy efficiency and cycle capacity retention rate of the battery cell. The reason for this analysis may be that when the OI value of graphite is low, it is further beneficial to the deintercalation of lithium ions, which can improve the kinetic performance of the battery cell, thereby improving the energy efficiency and cycle capacity retention rate of the battery cell. In summary, in the present application, the volume particle size Dv90 and OI value of the artificial graphite in the negative electrode plate are controlled within an appropriate range, which is further beneficial for the battery cell to have a higher energy density, energy efficiency and cycle capacity retention rate, and can extend the service life of the battery cell.

[0155] Example 6

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

[0157] Example 7

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

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

[0160] Table 3

[0161]

[0162] It can be seen from the combination of Example 1, Example 6 and Example 7 that with the increase in the coating weight of the active material layer in the positive electrode sheet and the negative electrode sheet, the energy density of the battery cell is also improved, but the energy efficiency and cycle capacity retention rate of the battery cell are reduced compared with Example 1. The main reason for this is that the increase in the coating weight of the active material layer of the electrode sheet leads to an increase in the thickness of the active material layer, which affects the internal resistance of the battery cell, lengthens the lithium ion transmission path, and affects the energy efficiency and cycle capacity of the battery cell. This shows that controlling the coating weight of the positive active material layer and the negative active material layer within an appropriate range is further beneficial to enable the battery cell to have both higher energy density and energy efficiency, as well as better cycle performance, and obtain a longer service life.

[0163] Example 8

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

[0165] Embodiment 9, Embodiment 10

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

[0167] Embodiment 11

[0168] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that in the positive electrode plate, the type and content of the lithium replenisher in the positive active material layer, and the material coated on the surface of the lithium replenisher are different, but the total mass proportion of the positive active material and the lithium replenisher in the positive active material layer is the same as that in Example 1.

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

[0170] Table 4

[0171]

[0172]

[0173] Combining Example 1 and Example 8, it can be seen that after adding carbon nanotubes to the conductive carbon black, the energy density, energy efficiency and cycle capacity retention rate of the battery cell are improved, indicating that the combination of conductive carbon black and an appropriate amount of carbon nanotubes as positive electrode conductive agents is further beneficial to extending the service life of the battery cell.

[0174] Combining Example 1, Example 9 and Example 10, it can be seen that as the amount of lithium supplement agent increases, the battery monomer cycle capacity retention rate also increases accordingly, but the battery monomer energy density shows a trend of first increasing and then decreasing. The main reason for this is that when the content of the lithium supplement agent is relatively high, the relative amount of the positive electrode active material decreases, and the improvement effect of the lithium supplement agent on the battery monomer energy density is not enough to compensate for the impact of the reduction in the amount of the positive electrode active material on the battery monomer energy density. This shows that appropriately increasing the amount of lithium supplement agent is beneficial to further enable the battery monomer to have higher volume energy density, energy efficiency and cycle capacity retention rate, and thus is beneficial to further extend the service life of the battery monomer.

[0175] Combining Example 1 and Example 11, it can be seen that using other lithium-rich materials to replace the lithium supplement in Example 1 can also enable the battery cell to have higher volume energy density, energy efficiency and cycle capacity retention rate, thereby extending the service life of the battery cell.

[0176] Example 12, Example 13, Example 14

[0177] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the lithium supplement in the positive electrode plate contains doping elements.

[0178] Example 15, Example 16

[0179] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the lithium supplement agent in the positive electrode plate has doping elements, and the type of material coated on the surface of the lithium supplement agent is different.

[0180] The differences between Example 12 and Example 16 are shown in Table 6.

[0181] Table 5

[0182]

[0183] It can be seen from Example 1 and Examples 12 to 16 that introducing an appropriate amount of doping elements into the lithium supplement or forming other coating materials on the surface of the lithium supplement can further regulate the energy efficiency or cycle performance of the battery cell, so that the battery cell has higher energy density, energy efficiency and cycle capacity retention rate, 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 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 active material layer, the positive electrode active material layer comprising a positive electrode active material and a lithium supplement, wherein along a section in a thickness direction of the positive electrode sheet, more than 50% of the positive electrode active material particles have a longest diameter that is smaller than the shortest diameter of the lithium supplement particles; A negative electrode plate, the negative electrode plate 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 μm-30 μm, and the negative electrode active material comprises 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 6 μm-12 μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The lithium supplement comprises Li x M1 y O z , Among them, 1≤x≤6, 1≤y≤6, 2≤z≤12, and M1 includes one or more of Na element, Ni element, Co element, Mn element, Al element, and Fe element.

5. The battery cell according to any one of claims 1 to 3, characterized in that: The lithium supplement includes Li2NiO2 and / or 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 / or Li p FeO q , where 0≤n≤2, 0<m≤2, 0<p≤5, 0<q≤4.

7. The battery cell according to any one of claims 1 to 3, characterized in that: The lithium supplement comprises NiO m and / or Li p FeO q , 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: At least part of the surface of the lithium supplement agent is provided with a coating layer, and the coating layer includes one or more of the C element, the Al element, the Zr element, the P element, and the S element.

9. The battery cell according to claim 8, characterized in that: The coating layer includes one or more of carbon material, aluminum oxide, zirconium oxide, lithium phosphide, and lithium sulfide.

10. The battery cell according to any one of claims 1 to 9, characterized in that: The lithium supplement further includes a doping element, and the doping element includes one or more of an Al element, a Zr element, and a B element.

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

12. The battery cell according to any one of claims 1 to 11, characterized in that: The compaction density of the positive electrode active material layer is 2.1 g / cm 3 -2.5g / cm 3 .

13. The battery cell according to any one of claims 1 to 12, characterized in that: The single-sided coating weight of the positive electrode active material layer is 0.25 g / 1540.25 mm 2 -0.3g / 1540.25mm 2 .

14. The battery cell according to any one of claims 1 to 13, characterized in that: The compaction density of the negative electrode active material layer is 1.2 g / cm 3 -1.5g / cm 3 .

15. The battery cell according to any one of claims 1 to 14, 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 any one of claims 1 to 15, characterized in that: Also includes: The electrolyte comprises a solvent, wherein 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%.

17. The battery cell according to claim 16, characterized in that: The electrolyte also includes a lithium salt, and the concentration of the lithium salt is 0.6 mol / L-1.2 mol / L, and can be optionally 0.7 mol / L-1 mol / L.

18. The battery cell according to claim 16 or 17, characterized in that: The electrolyte also includes fluoroethylene carbonate and vinylene carbonate.

19. The battery cell according to claim 18, characterized in that: The mass content of the fluoroethylene carbonate in the electrolyte is 0.1%-0.2%, and the mass content of the vinylene carbonate in the electrolyte is 1%-1.5%.

20. The battery cell according to any one of claims 1 to 19, characterized in that: Also includes: The isolation film comprises a base film, at least one side of which is provided with a coating.

21. The battery cell according to claim 20, characterized in that: The thickness of the isolation film is 7 μm-14 μm, and can be optionally 10 μm-12 μm.

22. The battery cell according to any one of claims 1 to 21, characterized in that: The positive electrode active material includes a polyanionic positive electrode active material.

23. The battery cell according to any one of claims 1 to 22, characterized in that: The positive electrode active material layer further includes: a conductive agent, and the conductive agent includes conductive carbon black and / or carbon nanotubes.

24. The battery cell according to any one of claims 1 to 23, characterized in that: The positive electrode active material includes a lithium iron phosphate material.

25. A battery device, characterized in that: The battery device comprises at least one of a battery module, a battery pack and an energy storage device.

26. An electrical device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 24 or the battery device according to claim 25, wherein the battery cell or the battery device is used to provide electrical energy.

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