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, in the positive pole piece, a positive active material layer comprises a positive active material, the positive active material comprises a nickel-cobalt-manganese metal oxide, based on the total molar weight of nickel-cobalt-manganese elements in the nickel-cobalt-manganese metal oxide, the molar ratio of the nickel element in the nickel-cobalt-manganese metal oxide is 80%-96%, or the molar ratio of the negative element in the nickel-cobalt-manganese metal oxide is 80%-96%. The positive electrode active material comprises a nickel-cobalt-aluminum metal oxide, and based on the total molar weight of nickel-cobalt-aluminum elements in the nickel-cobalt-aluminum metal oxide, the molar ratio of the nickel element in the nickel-cobalt-aluminum metal oxide is 80%-96%; in the negative electrode plate, the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises graphite and a silicon-containing material, based on the total mass of the negative electrode active material, the mass ratio of the silicon element in the negative electrode active material is 0.1%-10%, and the thickness of the negative electrode current collector is 3%-8% of the total thickness of the negative electrode plate. Therefore, the battery has relatively high energy density 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 density or long service life. Summary of the invention

[0003] The present application provides a battery cell, aiming to obtain high energy density and long service life.

[0004] In order to achieve the above-mentioned object, in a first aspect of the present application, a battery cell is provided, which includes a positive electrode sheet and a negative electrode sheet:

[0005] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, wherein:

[0006] The positive electrode active material comprises nickel-cobalt-manganese metal oxide, and the molar proportion of nickel in the nickel-cobalt-manganese metal oxide is 80% to 96% based on the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese metal oxide, or,

[0007] The positive electrode active material comprises nickel-cobalt-aluminum metal oxide, and based on the total molar amount of nickel, cobalt and aluminum elements in the nickel-cobalt-aluminum metal oxide, the molar proportion of nickel element in the nickel-cobalt-aluminum metal oxide is 80% to 96%;

[0008] The negative electrode active material includes graphite and silicon-containing material. Based on the total mass of the negative electrode active material, the mass proportion of silicon element in the negative electrode active material is 0.1% to 10%, and the thickness of the negative electrode collector is 3% to 8% of the total thickness of the negative electrode sheet.

[0009] The battery cell of the first aspect of the present application has at least the following beneficial effects: by comprehensively regulating the nickel content in the high-nickel positive electrode active material system and the amount of silicon-containing material in the negative electrode plate to meet the given ranges, and adjusting the thickness ratio of the current collector in the negative electrode plate to be within the given range, the battery energy density can be improved while reducing the risk of damage or disconnection of the electrode plate due to repeated expansion of the battery cell during long-term cycles. In turn, the battery can have both high energy density and long service life.

[0010] In some embodiments of the present application, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material is 0.5% to 9.5%, and can be 2% to 9.5%. This is conducive to achieving both higher initial efficiency and better cycle stability while improving battery energy density.

[0011] In some embodiments of the present application, the thickness of the negative electrode current collector is 4% to 7% of the total thickness of the negative electrode plate, thereby further taking into account the cycle performance and energy density of the battery and extending the service life of the battery.

[0012] In some embodiments of the present application, the thickness of the positive electrode current collector is 7.5% to 15%, and optionally 10% to 13.5% of the total thickness of the positive electrode sheet, thereby further taking into account the cycle performance and energy density of the battery and extending the service life of the battery.

[0013] In some embodiments of the present application, the positive electrode active material includes nickel-cobalt-manganese metal oxide, and the molar proportion of nickel in the nickel-cobalt-manganese metal oxide is 83% to 91% based on the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese metal oxide; or, the positive electrode active material includes nickel-cobalt-aluminum metal oxide, and the molar proportion of nickel in the nickel-cobalt-aluminum metal oxide is 83% to 91% based on the total molar amount of nickel, cobalt and aluminum in the nickel-cobalt-aluminum metal oxide. Thus, it is beneficial to further improve the cycle performance of the battery on the basis of improving the battery energy density and extend the service life of the battery.

[0014] In some embodiments of the present application, the silicon-containing material includes silicon-oxygen material and / or silicon-carbon material.

[0015] In some embodiments of the present application, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material is 2% to 6%, and can be 3% to 5%. This is conducive to improving the energy density of the battery while taking into account higher first efficiency and cycle stability.

[0016] In some embodiments of the present application, the silicon-containing material further includes metal elements, and the metal elements include one or more elements of Na, Li, Ti, Fe, and Co. This is beneficial to further improve the energy density and electrochemical performance of the battery.

[0017] In some embodiments of the present application, the mass of the metal element is 0.1% to 0.6% of the mass of the silicon element, which is beneficial to further improve the energy density and electrochemical performance of the battery.

[0018] In some embodiments of the present application, at least part of the surface of the silicon-containing material includes a carbon coating layer, which is beneficial to improving the structural stability of the silicon-containing material during the charge and discharge cycle process and also beneficial to improving the conductivity of the silicon-containing material.

[0019] In some embodiments of the present application, the graphite includes natural graphite, which is beneficial to further improve the energy density of the battery.

[0020] In some embodiments of the present application, the positive electrode active material includes a polycrystalline material.

[0021] In some embodiments of the present application, the particle size distribution of the positive electrode active material is bimodal, and the particle sizes corresponding to the peak values ​​of the two peaks are D1 and D2, 0.5 μm≤D1≤1.5 μm, 7 μm≤D2≤12 μm, which is conducive to further improving the energy density of the battery.

[0022] In some embodiments of the present application, the positive electrode active material further comprises: a lithium supplement agent. Thus, the battery energy density can be improved while the battery has both high initial efficiency and cycle performance.

[0023] In some embodiments of the present application, the lithium supplement comprises Li x M y O z , 1≤x≤5, 1≤y≤3, 1≤z≤8, M includes one or more of Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn.

[0024] In some embodiments of the present application, the lithium supplement agent includes Li2NiO2 and / or Li5FeO4, which can achieve a better positive electrode lithium supplement effect.

[0025] In some embodiments of the present application, the lithium supplement comprises Li n NiO m and / or Li p FeO p , where 0≤n≤2, 0<m≤2, 0<p≤5, 0<p≤4.

[0026] 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.

[0027] In some embodiments of the present application, based on the total mass of the positive electrode active material, the mass proportion of the lithium supplement is 0.5% to 5%, and can be 1% to 3%. This allows the battery to have both high first efficiency and energy density, as well as good cycle performance.

[0028] In some embodiments of the present application, the positive electrode active material includes nickel cobalt manganese metal oxide, and the nickel cobalt manganese metal oxide includes one or more elements of Na, K, Mg, B, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F, and optionally includes one or more elements of Al, Zr, B, P, and Ti. Thus, the electrochemical performance of the positive electrode active material can be further improved.

[0029] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide includes an Al element, and based on the total mass of the positive electrode active material, the mass proportion of the Al element is 0.01% to 0.1%.

[0030] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide includes a Zr element, and based on the total mass of the positive electrode active material, the mass proportion of the Zr element is 0.1% to 0.5%.

[0031] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide includes a B element, and based on the total mass of the positive electrode active material, the mass proportion of the B element is 0.01% to 0.15%.

[0032] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide includes a P element, and based on the total mass of the positive electrode active material, the mass proportion of the P element is 0.05% to 0.2%.

[0033] In some embodiments of the present application, the single-sided coating density of the positive electrode active material layer is 20 mg / cm 2 ~30mg / cm 2 This helps the battery to have both higher energy density and better dynamic performance.

[0034] In some embodiments of the present application, the compaction density of the positive electrode active material layer is 3.3 g / cm 3 ~3.6g / cm3 This helps the battery to have both higher energy density and better dynamic performance.

[0035] In some embodiments of the present application, the thickness of the positive electrode current collector is 13 μm to 19 μm, and can be 15 μm to 17 μm. This can reduce the risk of fracture of the current collector and the active material layer, and can also take into account the energy density of the battery, so that the battery has a higher energy density, better cycle stability and a longer service life.

[0036] In some embodiments of the present application, the single-sided coating density of the negative electrode active material layer is 10 mg / cm 2 ~18mg / cm 2 , optional 13mg / cm 2 ~15mg / cm 2 This helps the battery to have both higher energy density and better kinetic performance.

[0037] In some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.3 g / cm 3 ~1.7g / cm 3 , optional 1.4g / cm 3 ~1.55g / cm 3 This helps the battery to have both higher energy density and better dynamic performance.

[0038] In some embodiments of the present application, the thickness of the negative electrode current collector is 6 μm to 13 μm, and can be optionally 8 μm to 11 μm.

[0039] In some embodiments of the present application, the battery cell further comprises: an electrolyte, the electrolyte comprises an organic solvent, and the organic solvent comprises a cyclic carbonate and a linear carbonate. This is further conducive to obtaining a battery with a high energy density.

[0040] In some embodiments of the present application, the cyclic carbonate includes EC and / or PC, and the linear carbonate includes one or more of EMC, DMC, and DEC.

[0041] In some embodiments of the present application, based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate is 15% to 25%, and the mass proportion of the linear carbonate is 50% to 70%.

[0042] In some embodiments of the present application, the electrolyte further comprises: an additive, wherein the additive comprises FEC and / or VC, thereby facilitating further improvement of the first efficiency, energy density and cycle performance of the battery.

[0043] In some embodiments of the present application, the battery cell further comprises: a separator, wherein a ceramic coating containing an inorganic oxide is disposed on a side of the separator facing the positive electrode plate, thereby facilitating improving the oxidation resistance and high temperature stability of the separator.

[0044] In some embodiments of the present application, the isolation membrane is further provided with a first bonding coating, and the first bonding coating is located between the isolation membrane and the ceramic coating.

[0045] In some embodiments of the present application, a second bonding coating is provided on the side of the separator facing the negative electrode plate.

[0046] In some embodiments of the present application, the total thickness of the isolation film is 7 μm to 14 μm, and can be optionally 7 μm to 10 μm.

[0047] In some embodiments of the present application, the battery cell is a cylindrical battery, the cylindrical battery includes a shell, the shell includes an upper cover, a lower cover and a side wall, the thickness of the side wall is 0.2mm to 0.4mm, and can be 0.25mm to 0.3mm. This can make the shell side wall have a lower thickness and mass, which is conducive to further improving the battery energy density.

[0048] In some embodiments of the present application, the thickness of the shell wall of the upper cover or the lower cover is 0.25mm-0.45mm, and can be 0.27mm-0.33mm, which can make the upper cover or the lower cover of the shell have a lower thickness and mass, which is conducive to further improving the energy density of the battery.

[0049] The 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 power-consuming device includes at least one of a battery module, a battery pack, and an energy storage device.

[0050] 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 electrical 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

[0051] 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:

[0052] Figure 1 It is a schematic structural diagram of a battery cell according to one embodiment of the present application.

[0053] Figure 2 It is a schematic structural diagram of a battery module according to one embodiment of the present application.

[0054] Figure 3It is a schematic diagram of the structure of a battery pack according to one embodiment of the present application.

[0055] Figure 4 yes Figure 3 Exploded diagram of .

[0056] Figure 5 It is a schematic diagram of an embodiment of an electrical device using the battery device of the present application as a power source.

[0057] Description of reference numerals:

[0058] 1: Battery cell; 2: Battery module; 3: Battery pack; 4: Upper case; 5: Lower case. DETAILED DESCRIPTION

[0059] 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.

[0060] 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.

[0061] "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.

[0062] 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.

[0063] Unless otherwise specified, all technical features and optional technical features 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.

[0064] 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.

[0065] 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.

[0066] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0067] 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).

[0068] 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 density and long service life have become an important research direction in the battery industry. In the existing battery system, there are many directions for improving battery energy density and service life, including but not limited to the selection of positive and negative active materials, improvement of battery structure, optimization of electrolyte, etc. For example, there is a solution that uses high-nickel positive active materials with graphite negative electrodes to extend the battery life from the two aspects of battery energy density and cycle stability, but this solution has limited ability to improve battery energy density.

[0069] This application aims to develop a battery cell with both high energy density and long service life. The energy density of the battery cell is improved by using high-nickel positive electrode active materials with graphite and silicon-containing negative electrodes. At the same time, the cycle performance of the battery cell is taken into account by controlling the nickel content in the positive electrode active material, the amount of silicon-containing material added in the negative electrode plate, and the thickness ratio of the current collector in the negative electrode plate. On the basis of obtaining high energy density, the cycle life of the battery cell is improved and the service life of the battery cell is extended.

[0070] In the positive electrode plate of the present application, the positive electrode active material includes nickel-cobalt-manganese metal oxide, and the molar proportion of nickel in the nickel-cobalt-manganese metal oxide is 80% to 96% based on the total molar amount of nickel, cobalt and manganese elements in the nickel-cobalt-manganese metal oxide, or the positive electrode active material includes nickel-cobalt-aluminum metal oxide, and the molar proportion of nickel in the nickel-cobalt-aluminum metal oxide is 80% to 96% based on the total molar amount of nickel, cobalt and aluminum elements in the nickel-cobalt-aluminum metal oxide; in the negative electrode plate, the negative electrode active material includes graphite and silicon-containing materials, and the mass proportion of silicon in the negative electrode active material is 0.1% to 10% based on the total mass of the negative electrode active material, and the thickness of the negative electrode current collector is 3% to 8% of the total thickness of the negative electrode plate. The positive electrode plate adopts a high-nickel ternary active material, and the negative electrode plate adopts graphite and silicon-containing materials, which can fully utilize the high gram capacity characteristics of the positive and negative electrode materials to increase the capacity of the positive and negative electrode plates, and significantly improve the energy density of the battery. However, silicon-containing materials are prone to particle rupture and pulverization due to large volume expansion during the charge and discharge cycle, which in turn causes rapid battery capacity decay. Therefore, although appropriately increasing the amount of silicon-containing materials in the negative electrode sheet has a positive effect on improving the battery energy density, the increase in the amount of silicon-containing materials will reduce the battery cycle performance, especially when the positive electrode active material is a high-nickel material, the battery cycle capacity decay is more aggravated, so the amount of silicon-containing materials in the negative electrode sheet needs to be controlled within an appropriate range. However, although an appropriate amount of silicon-containing materials in the negative electrode sheet can improve the energy density and reduce the cycle decay, the easy expansion of silicon-containing materials in the negative electrode sheet also causes the negative electrode active material layer to expand repeatedly during the long-term cycle, resulting in the negative electrode current collector connected thereto also being repeatedly stressed and pulled. Therefore, if the negative electrode current collector in the negative electrode sheet is set too thin (low tensile strength), it is easy to cause the negative electrode current collector to cause the negative electrode active material layer to be damaged or cracked due to the low tensile strength, reducing the cycle life and reliability of the battery. If the current collector is set too thick, it is easy to reduce the battery energy density and the internal resistance of the battery will also increase. In this application, by comprehensively regulating the nickel content in the high-nickel positive electrode active material system and the amount of silicon-containing material in the negative electrode plate to meet the given ranges, and adjusting the thickness ratio of the current collector in the negative electrode plate to be within the given range, the battery energy density can be improved while reducing the risk of damage or disconnection of the electrode plate due to repeated expansion of the battery cell during long-term cycles. In turn, the battery cell can have both high energy density and long service life.

[0071] The battery cell disclosed in the embodiments of the present application can be used in various energy storage systems that use battery cells or battery devices with the battery cells as power sources for electrical equipment or use battery cells or battery devices with the battery cells as energy storage elements. 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.

[0072] A first aspect of the present application provides a battery cell, which includes: a positive electrode sheet and a negative electrode sheet. The positive electrode plate includes a positive electrode collector and a positive electrode active material layer arranged on at least one side of the positive electrode collector, the positive electrode active material layer includes a positive electrode active material, and the negative electrode plate includes a negative electrode collector and a negative electrode active material layer arranged on at least one side of the negative electrode collector, the negative electrode active material layer includes a negative electrode active material, wherein the positive electrode active material includes nickel cobalt manganese metal oxide, based on the total molar amount of nickel, cobalt and manganese elements in the nickel cobalt manganese metal oxide, the molar proportion of nickel element in the nickel cobalt manganese metal oxide is 80% to 96%, or the positive electrode active material includes nickel cobalt aluminum metal oxide, based on the total molar amount of nickel, cobalt and aluminum elements in the nickel cobalt aluminum metal oxide, the molar proportion of nickel element in the nickel cobalt aluminum metal oxide is 80% to 96%; the negative electrode active material includes graphite and silicon-containing material, based on the total mass of the negative electrode active material, the mass proportion of silicon element in the negative electrode active material is 0.1% to 10%, and the thickness of the negative electrode collector is 3% to 8% of the total thickness of the negative electrode plate.

[0073] In the battery cell of the present application, the positive electrode plate adopts a high-nickel multi-active material, and the negative electrode plate adopts graphite and silicon-containing materials, which can make full use of the high gram capacity characteristics of the positive and negative electrode materials to increase the capacity of the positive and negative electrode plates, and significantly improve the energy density of the battery. However, silicon-containing materials are prone to particle rupture and pulverization due to large volume expansion during the charge and discharge cycle, which in turn causes the battery capacity to decay rapidly. Therefore, although appropriately increasing the amount of silicon-containing materials in the negative electrode plate has a positive effect on improving the battery energy density, the increase in the amount of silicon-containing materials will reduce the battery's cycle performance, especially when the positive active material is a high-nickel material, the battery cycle capacity decay is more aggravated, so the amount of silicon-containing materials in the negative electrode plate needs to be controlled within an appropriate range. However, although an appropriate amount of silicon-containing material in the negative electrode plate can increase the energy density and reduce the cycle attenuation, the easy expansion property of the silicon-containing material in the negative electrode plate also causes the negative electrode active material layer to expand repeatedly during long-term cycles, resulting in the negative electrode current collector connected thereto also being repeatedly stressed and pulled. Therefore, if the negative electrode current collector in the negative electrode plate is set too thin (low tensile strength), it is easy to cause the negative electrode current collector to cause damage or cracking of the negative electrode active material layer due to low tensile strength, thereby reducing the cycle life and reliability of the battery. If the current collector is set too thick, it is easy to reduce the energy density of the battery and the internal resistance of the battery will also increase.

[0074] This problem is particularly evident in cylindrical batteries. Taking cylindrical batteries as an example, during long-term cycling, the outer ring electrodes, especially the outermost electrodes, are subjected to greater forces. It is more likely that the negative electrode active material layer will be damaged or disconnected due to an unreasonable ratio of the current collector thickness to the electrode thickness, which has a more significant impact on the cycle performance.

[0075] In the present application, by comprehensively regulating the nickel content in the high-nickel positive electrode active material system and the amount of silicon-containing material in the negative electrode plate to meet the given ranges respectively, and at the same time adjusting the thickness ratio of the current collector in the negative electrode plate to be within the given range, the battery energy density can be improved while reducing the risk of damage or disconnection of the electrode plate due to repeated expansion of the battery cell during long-term cycling. Taking cylindrical batteries as an example, the risk of damage or disconnection of the outer ring electrode plate can be reduced, thereby improving the energy density, cycle life and reliability of the battery cell.

[0076] 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 density and longer service life.

[0077] Exemplarily, the positive electrode active material may include nickel cobalt manganese metal oxide, and the molar proportion of nickel element in the nickel cobalt manganese metal oxide may be 80%, 82%, 85%, 88%, 90%, 92%, 95% or 96%, etc. based on the total molar amount of nickel, cobalt and manganese elements in the nickel cobalt manganese metal oxide.

[0078] Exemplarily, the positive electrode active material may include nickel cobalt aluminum metal oxide, and the molar proportion of nickel element in the nickel cobalt aluminum metal oxide may be 80%, 82%, 85%, 88%, 90%, 92%, 95% or 96%, etc. based on the total molar amount of nickel, cobalt and aluminum elements in the nickel cobalt aluminum oxide.

[0079] Illustratively, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0080] Illustratively, the thickness of the negative electrode current collector may be 3%, 4%, 5%, 6%, 7% or 8%, etc., of the total thickness of the negative electrode sheet.

[0081] In the present application, the relative molar proportion of nickel in the positive electrode active material and the mass proportion of silicon in the negative electrode active material can include but are not limited to inductively coupled plasma emission spectrometry (ICP) testing or EDS energy spectrum analysis. For example, EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry" can be referred to. After the battery is disassembled, the active material sample to be tested is separated from the pole piece. After the sample to be tested is treated by a chemical method and digested into a solution, it is atomized into the plasma to excite the characteristic spectrum of the element, and the element content is qualitatively and quantitatively analyzed according to the wavelength and intensity of the spectrum (proportional to the concentration). In addition, the thickness proportion of the current collector in the negative electrode pole piece can be combined with conventional instruments such as a thickness meter, and calculated by testing the total thickness of the pole piece and the thickness of the current collector. In the actual operation process, when testing the element composition in the active material, the active material sample to be tested can be obtained from the pole piece by using a mechanical stripping method or the like. When testing the thickness of the current collector, one or more of heat treatment, mechanical stripping, and chemical dissolution methods can be combined to achieve effective separation of the active material layer of the pole piece and the current collector.

[0082] [Positive electrode]

[0083] In some embodiments of the present application, the thickness of the positive current collector may be 7.5% to 15% of the total thickness of the positive electrode sheet. For example, the thickness of the positive current collector may be 7.5%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15% of the total thickness of the positive electrode sheet, etc. High nickel materials expand more during the cycle than low nickel materials. This characteristic of high nickel materials also causes the positive active material layer to be repeatedly pulled due to repeated expansion during long-term cycles. Therefore, if the thickness ratio of the positive current collector in the positive electrode sheet is set to be thinner (low tensile strength), the positive current collector is easily pulled by the negative active material layer due to the low tensile strength, which may cause the positive active material layer to be damaged or cracked. This may reduce the cycle life and reliability of the battery. By controlling the thickness ratio of the positive electrode current collector in the positive electrode sheet to meet the given range, not only can the cycle performance and reliability of the battery cell be further improved, but also the energy density of the battery cell can be taken into account, and the adverse effects of the increase in the thickness of the positive electrode current collector on the battery energy density and internal resistance can be reduced, thereby enabling the battery to have a higher energy density, better cycle stability and a longer service life. Optionally, the thickness of the positive electrode current collector can be 10% to 13.5% of the total thickness of the positive electrode sheet.

[0084] In some embodiments of the present application, the positive electrode active material may include nickel-cobalt-manganese metal oxide, and the molar proportion of nickel in the nickel-cobalt-manganese metal oxide may be 83% to 91% based on the total molar amount of nickel, cobalt and manganese elements in the nickel-cobalt-manganese metal oxide; or, the positive electrode active material may include nickel-cobalt-aluminum metal oxide, and the molar proportion of nickel in the nickel-cobalt-aluminum metal oxide may be 83% to 91% based on the total molar amount of nickel, cobalt and aluminum elements in the nickel-cobalt-aluminum metal oxide. For the positive electrode active materials of the nickel-cobalt-manganese system and / or the nickel-cobalt-aluminum system with high nickel content, controlling the relative molar content of nickel to meet the given range can further take into account the cycle stability of the battery on the basis of improving the battery energy density, reduce the risk of problems such as structural instability of the positive electrode active material or lithium-nickel mixing due to high nickel content, and extend the service life of the battery.

[0085] In some embodiments of the present application, the positive electrode active material may include a polycrystalline material. Optionally, the polycrystalline material may include secondary particles formed by the accumulation of primary particles. In some embodiments, the positive electrode active material may be a polycrystalline material. In other embodiments, the positive electrode active material may include polycrystalline materials and single crystal materials. Compared with polycrystalline materials, the particle size of single crystal materials is relatively small, which can be filled in the pores of polycrystalline materials, thereby increasing the compaction density of the positive electrode active material layer; in addition, the crystal structure of single crystal particles is more stable, and the voltage is higher and the cycle life is better. Mixing single crystal materials and polycrystalline materials is conducive to further improving the energy density and cycle performance of the battery and extending the service life.

[0086] In some embodiments of the present application, the particle size distribution diagram of the positive electrode active material may be bimodal, and the particle sizes corresponding to the peak values ​​of the two peaks may be D1 and D2, respectively, 0.5 μm ≤ D1 ≤ 1.5 μm, 7 μm ≤ D2 ≤ 12 μm. For example, the value of D1 may be 0.5 μm, 0.8 μm, 1 μm, 1.2 μm or 1.5 μm, etc., and the value of D2 may be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm, etc. The particle size distribution diagram of the positive electrode active material may be measured and statistically obtained by referring to the standard GB / T 19077-2016 / ISO 13320:2009 using a laser particle size analyzer (Malvern Master Size 2000). Making the particle size distribution of the positive electrode active material present a bimodal distribution can be achieved by using two positive electrode active materials with different particle size distributions, and then using small-sized positive electrode active material particles to fill the pores of large-sized positive electrode active materials to achieve a higher electrode compaction density. In the embodiment of the present application, by controlling the particle size distribution of the positive electrode active material to present a bimodal distribution and satisfying the given range, the compaction density of the positive electrode active material layer can be significantly improved, thereby further improving the energy density of the battery.

[0087] In some embodiments of the present application, the positive electrode active material may be a polycrystalline material, and the particle size distribution diagram of the positive electrode active material may be a bimodal distribution, and the particle sizes corresponding to the peak values ​​of the two peaks may be D1 and D2, respectively, 0.5μm≤D1≤1.5μm, 7μm≤D1≤12μm. Compared with the method of mixing single crystal and polycrystalline, the use of polycrystalline material and making its particle size distribution meet the given bimodal distribution conditions can further improve the energy density of the battery.

[0088] In some embodiments of the present application, the positive electrode active material may further include: a lithium supplement. Compared with graphite, silicon-containing materials have relatively more active sites, and relatively more Li is consumed when forming the SEI film in the lithium battery. In addition, the volume expansion of silicon-containing materials during the charge and discharge cycle is also large, and the SEI film is easily broken and regenerated due to the cycle expansion, thereby consuming more Li. By adding a lithium supplement to the positive electrode active material, the consumption of Li by silicon-containing materials can be compensated or alleviated, and the adverse effects of the introduction of silicon-containing materials on the first efficiency and cycle performance of the battery can be reduced. At the same time, the high-temperature storage performance of the battery can also be improved. In this way, while improving the energy density of the battery, the battery can have both a higher first efficiency, better cycle performance and high-temperature storage performance, thereby extending the service life of the battery.

[0089] In some embodiments of the present application, the lithium supplement may include Li x M y O z, 1≤x≤5, 1≤y≤3, 1≤z≤8, M includes one or more elements selected from Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn. Exemplarily, the value of x can be 1, 2, 3, 4, or 5, or can be a range consisting of any of the above values. Optionally, the value of x can be 1<x≤5, such as 2≤x≤5; the value of y can be 1, 2, or 3, or can be a range consisting of any of the above values. The value of z can be 1, 2, 3, 4, 5, 6, 7, or 8, or can be a range consisting of any of the above values. Optionally, the value of z can be 1<z≤8, such as 2≤z≤8. Li is doped into the positive electrode active material x M y O z , which can achieve a better positive electrode lithium replenishment effect. It is understandable that during the battery formation and use process, as the lithium replenishment process proceeds, the lithium in the lithium replenisher will be partially or completely released, causing the lithium replenisher to transform from an initial state to a partially or completely delithiated state, at which time x≤1 and / or z≤1 will occur.

[0090] 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-x2 NiO2, 0≤x2≤1, can be restored to LiNiO2 in the lithium-inserted state; Li5FeO4 has a strong lithium-supplementing ability, and the LiFeO2 formed after lithium removal does not bring about obvious side reactions. Therefore, using Li2NiO2 and / or Li5FeO4 as a lithium-supplementing agent can achieve a better capacity compensation effect.

[0091] 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 m Taking 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<e<2, 2≤e<3, 3≤e<4, 4≤e<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.

[0092] 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 delithiated, the lithium supplement after delithiation can include but is not limited to NiO and / or LiFeO2.

[0093] In an embodiment of the present application, the positive electrode active material layer or the positive electrode active material can be qualitatively and quantitatively analyzed in combination with one or more conventional instruments and conventional methods such as a scanning electron microscope, an EDS spectrometer, an X-ray diffractometer, and an inductively coupled plasma emission spectrometer. For example, in the positive electrode active material layer, the lithium supplement and the nickel-cobalt-manganese metal oxide particles or the nickel-cobalt-aluminum metal oxide usually have size differences, and the lithium supplement does not completely disappear after delithiation, but residual elements and particle skeletons will remain. The lithium supplement usually has a certain volume shrinkage after delithiation, so that a certain gap is formed between the residual particle skeleton and the surrounding area. Based on the above differences, the possible location of the lithium supplement in the cross section of the positive electrode active material layer can be quickly screened in the scanning electron microscope test, and the elemental composition and content of the lithium supplement can be analyzed in combination with the EDS spectrometer; in addition, the X-ray diffractometer can be further combined to perform XRD characterization on the positive electrode active material sample to be tested to determine the crystal structure of the lithium supplement, and the content of the lithium supplement can be further determined in combination with the ICP test.

[0094] In some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass of the positive electrode active material in the positive electrode active material layer may account for 97.5% to 98.5%, for example, 97.5%, 98% or 98.5%, etc. The content of the positive electrode active material may be tested by performing thermogravimetric analysis on the positive electrode active material layer sample in a discharged state (such as after being discharged to the lower cut-off voltage), such as heating the sample to be tested at a heating rate of 5°C / min until the mass of the sample to be tested no longer changes significantly, wherein the temperature range of the heating may be 25°C to 600°C. Making the content of the positive electrode active material meet the given range is conducive to further improving the energy density of the battery.

[0095] In some embodiments of the present application, based on the total mass of the positive electrode active material, the mass proportion of the lithium supplement agent can be 0.5% to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc. The content of the lithium supplement agent in the positive electrode active material can be calculated by combining ICP testing and other methods by testing the total content of Li in the positive electrode active material per unit area of ​​the positive electrode sheet, the remaining lithium content in the lithium supplement agent and the lithium content in the nickel-cobalt-manganese metal oxide or the nickel-cobalt-aluminum metal oxide. Optionally, the content of the lithium supplement agent in the positive electrode active material can be tested in a discharged state (such as after discharging to the lower limit cut-off voltage). Among them, appropriately increasing the content of the lithium supplement agent is conducive to improving the first effect of the battery and improving the cycle performance of the battery. In this application, the content of the lithium supplement agent is controlled to meet the given conditions. On the basis of improving the first effect of the battery, the risk of a significant decrease in the battery energy density due to the large amount of lithium supplement agent added can be reduced, thereby enabling the battery to have both a higher first effect and energy density, as well as better cycle performance, and obtain a longer service life. Furthermore, based on the total mass of the positive electrode active material, the mass proportion of the lithium supplement may be 1% to 3%, thereby further enabling the battery to have both higher first efficiency and energy density, as well as better cycle performance.

[0096] In some embodiments of the present application, the positive electrode active material may include nickel cobalt manganese metal oxide, and the nickel cobalt manganese metal oxide may include one or more elements selected from the group consisting of Na, K, Mg, B, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F. For example, taking a lithium battery as an example, the nickel cobalt manganese metal oxide may include Li x1 Ni a Co b Mn c M1 dO2, wherein 0.8≤x1≤1.2, 0.8≤a≤0.96, 0.04≤b≤0.12, 0.03≤c≤0.07, 0≤d≤0.13, optionally, a+b+c+d=1, and M1 can be one or more elements selected from the group consisting of Na, K, Mg, B, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F. Other elements (such as M1 element) in nickel-cobalt-manganese metal oxide can be qualitatively and quantitatively analyzed by inductively coupled plasma emission spectroscopy (ICP) testing or EDS energy spectrum analysis. Specifically, it can be performed in a discharged state. For example, taking ICP testing as an example, the battery cell can be fully discharged (such as after being discharged to the lower limit cut-off voltage), and the battery cell can be disassembled to obtain the positive electrode active material sample to be tested, and then relevant tests can be performed. Doping the above elements in the nickel-cobalt-manganese ternary active material can further improve its electrochemical performance and extend the service life of the battery.

[0097] In some embodiments of the present application, the positive electrode active material may include nickel-cobalt-manganese metal oxide, and the nickel-cobalt-manganese metal oxide may include one or more elements of Al, Zr, B, P, and Ti. Doping elements such as Zr or B in the nickel-cobalt-manganese metal oxide is beneficial to further stabilize the structure of the high-nickel ternary active material and improve the cycle stability. As a result, the battery can further have both higher energy density and better cycle stability, extending the service life of the battery.

[0098] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide may include the Al element. Based on the total mass of the positive electrode active material, the mass proportion of the Al element may be 0.01% to 0.1%, such as 0.01%, 0.02%, 0.05%, 0.08% or 0.1%, and so on.

[0099] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide may include the Zr element. Based on the total mass of the positive electrode active material, the mass proportion of the Zr element may be 0.1% to 0.5%, such as 0.1%, 0.2%, 0.3%, 0.4% or 0.5%, etc.

[0100] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide may include the B element. Based on the total mass of the positive electrode active material, the mass proportion of the B element may be 0.01% to 0.15%, such as 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.12% or 0.15%, etc.

[0101] In some embodiments of the present application, the nickel-cobalt-manganese metal oxide may include the P element. Based on the total mass of the positive electrode active material, the mass proportion of the P element may be 0.05% to 0.2%, such as 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18% or 0.2%, etc.

[0102] In the present application, controlling the content of the elements in the nickel-cobalt-manganese metal oxide to meet the given range is beneficial to further improve the electrochemical properties of the nickel-cobalt-manganese ternary active material, and can also reduce the risk of adverse effects on battery performance due to the introduction of a high content of doping elements.

[0103] In some embodiments of the present application, the single-sided coating density of the positive electrode active material layer can be 20 mg / cm 2 ~30mg / cm 2 , for example, 20 mg / cm 2 , 22.5mg / cm 2 , 25mg / cm 2 、27.5mg / cm 2 or 30mg / cm 2 Etc. Properly increasing the surface density of the positive electrode active material layer is conducive to further improving the energy density of the battery. When the surface density of the positive electrode active material layer meets the given range, the risk of a decrease in battery kinetic performance due to a high surface density of the electrode coating can be reduced on the basis of making the battery have a higher energy density, thereby making the battery have both a higher energy density and better kinetic performance.

[0104] In some embodiments of the present application, the compaction density of the positive electrode active material layer can be 3.3 g / cm 3 ~3.6g / cm 3 , for example, it can be 3.3 g / cm 3 、3.35g / cm 3 、3.4g / cm 3 、3.45g / cm 3 , 3.5g / cm 3 、3.55g / cm 3 or 3.6g / cm 3 Etc. Properly increasing the compaction density of the positive electrode active material layer is conducive to further improving the energy density of the battery, so that the compaction density of the positive electrode active material layer meets the given range, which can reduce the risk of battery kinetic performance degradation due to high compaction density of the pole piece on the basis of making the battery have a higher energy density, thereby making the battery have both higher energy density and better kinetic performance.

[0105] In the present application, the single-sided coating surface density of the positive electrode active material layer and the compaction density of the positive electrode active material layer can be used to discharge the battery cell to 0% SOC and refer 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 a small disc with an area of ​​S1, weighed, recorded as M1, and measured its thickness H1. 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 surface density 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 surface density of the positive electrode active material layer / the thickness of the positive electrode active material layer.

[0106] It should be noted that, in the present application, discharging a battery cell to 0% SOC means: charging the battery cell to 4.25V at a constant current of 1 / 3C, then charging at a constant voltage of 4.25V to a current of 0.05C, leaving it for 5 minutes, and then discharging it to 2.5V at 1 / 3C, which corresponds to the state of charge of the battery cell.

[0107] In some embodiments of the present application, the thickness of the positive current collector may be 13 μm to 19 μm, for example, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or 19 μm. Properly increasing the thickness of the positive current collector can reduce the risk of damage to the positive current collector at a higher compaction density, as well as the risk of the positive electrode sheet being broken due to expansion or stress pulling during the charge and discharge cycle. When the thickness of the current collector meets the given range, it can not only reduce the risk of the current collector breaking during the preparation of the sheet and the risk of the sheet breaking during the use of the battery, improve the cycle performance of the battery, but also take into account the energy density of the battery, reduce the adverse effects of the increase in the thickness of the current collector on the battery energy density, and enable the battery to have both higher energy density, better cycle stability and longer service life. Further, the thickness of the positive current collector may be 15 μm to 17 μm.

[0108] In some embodiments of the present application, 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.

[0109] In some embodiments of the present application, the positive electrode active material layer may also optionally include at least one of a binder, a conductive agent, and other optional auxiliary agents. Wherein, the binder, the conductive agent, and the auxiliary agent may all be conventionally selected in the art, for example, the conductive agent may include but is not limited to one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and 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 can all be obtained through commercial channels.

[0110] [Negative electrode]

[0111] In some embodiments of the present application, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material can be 0.5% to 9.5%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 9.5%, etc. Controlling the proportion of silicon-containing materials in the negative electrode active material so that the mass proportion of silicon in the negative electrode active material meets the given range is conducive to further balancing the effect of improving the battery energy density due to the improvement of silicon-containing materials and the adverse effects of the battery's first efficiency and cycle capacity retention rate due to the large number of active sites and large cycle expansion volume of silicon-containing materials, thereby facilitating the consideration of higher first efficiency and cycle stability on the basis of further improving the battery energy density. Optionally, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material can be 2% to 9.5%.

[0112] In some embodiments of the present application, the thickness of the negative electrode current collector can be 4% to 7% of the total thickness of the negative electrode plate. In this way, the risk of damage or breakage of the negative electrode plate due to repeated expansion during long-term battery cycling can be reduced, and the adverse effect of increased thickness of the negative electrode current collector on the battery energy density can be further reduced, so that the battery has higher energy density, better cycle stability and longer service life.

[0113] In some embodiments of the present application, the graphite may include natural graphite. Compared with artificial graphite, natural graphite has a higher specific capacity, and the combination of natural graphite and silicon-containing materials is conducive to further improving the energy density of the battery.

[0114] In some embodiments of the present application, the silicon-containing material may include silicon-oxygen material and / or silicon-carbon material. This is conducive to further improving the energy density of the battery. Among them, the type of silicon-containing material can be qualitatively analyzed by combining one or more conventional characterization methods such as X-ray diffraction analysis (XRD) and EDS energy spectrum analysis.

[0115] In some embodiments of the present application, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material can be 2% to 6%, for example, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%. Controlling the proportion of silicon-containing materials in the negative electrode active material so that the mass proportion of silicon in the negative electrode active material meets the given range is conducive to further balancing the effect of improving the battery energy density due to the improvement of silicon-containing materials and the adverse effects of the battery's first efficiency and cycle capacity retention rate due to the large number of active sites and large cycle expansion volume of silicon-containing materials, thereby facilitating the further improvement of the battery energy density while taking into account the higher first efficiency and cycle stability. Further, based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material can be 3% to 5%.

[0116] In some embodiments of the present application, the silicon-containing material may also include metal elements, and the metal elements may include one or more elements of Na, Li, Ti, Fe, and Co. The presence of metal elements in the silicon-containing material can be analyzed in a discharge state (such as discharging to the lower limit cutoff voltage or discharging to 0% SOC) in combination with one or more conventional characterization methods such as EDS spectrum analysis and ICP testing. For example, the battery cell can be disassembled after discharging to 0% SOC, and the pole piece can be soaked in DMC and then cut by plasma quenching. The cross section is placed under a scanning electron microscope for observation, and the type of metal elements in the silicon-containing material is tested using an EDS spectrometer. Doping Na or Li in the silicon-containing material can occupy the active sites of the silicon-containing material, reduce the consumption of Li in the process of forming the SEI film, and thereby improve the energy density and cycle life of the battery; doping Ti, Fe or Co in the silicon-containing material can increase the carrier concentration and the conductivity of the silicon-containing material, and thereby further improve the energy density and electrochemical performance of the battery.

[0117] In some embodiments of the present application, the silicon-containing material includes a metal element, and the mass of the metal element can be 0.1% to 0.6% of the mass of the silicon element, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or 0.6% of the mass of the silicon element. The content of the metal element in the negative electrode active material can be analyzed in a discharged state (such as discharged to the lower limit cut-off voltage or discharged to 0% SOC) in combination with one or more conventional characterization methods such as ICP testing and EDS spectrum analysis, thereby obtaining the relative content of the metal element and the silicon element in the negative electrode active material. For example, after discharging to 0% SOC, the battery cell can be disassembled to obtain the negative electrode plate, and the plate can be soaked in DMC and then 2g of powder is scraped off, and the metal content is tested by ICP. The content of the metal element meets the given range, which is conducive to further improving the energy density and / or electrochemical performance of the battery.

[0118] In some embodiments of the present application, at least part of the surface of the silicon-containing material may include a carbon coating layer, thereby not only improving the structural stability of the silicon-containing material during the charge and discharge cycle and reducing the risk of pulverization due to volume expansion, but also improving the conductivity of the silicon-containing material, thereby further improving the electrochemical performance of the battery.

[0119] In some embodiments of the present application, the single-sided coating density of the negative electrode active material layer can be 10 mg / cm 2 ~18mg / cm 2 , for example, 10 mg / cm 2 , 12mg / cm 2 、14mg / cm 2 、16mg / cm 2 or 18 mg / cm 2 Properly increasing the surface density of the negative electrode active material layer is conducive to further improving the energy density of the battery. When the surface density of the negative electrode active material layer meets the given range, the risk of a decrease in battery kinetic performance due to a high surface density of the electrode coating can be reduced on the basis of making the battery have a higher energy density, thereby making the battery have both a higher energy density and better kinetic performance. Furthermore, the single-sided coating surface density of the negative electrode active material layer can be 13 mg / cm 2 ~15mg / cm 2 .

[0120] In some embodiments of the present application, the compaction density of the negative electrode active material layer can be 1.3 g / cm 3 ~1.7g / cm 3 , for example, 1.3 g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm3 or 1.7 g / cm 3 Properly increasing the compaction density of the negative electrode active material layer is conducive to further improving the energy density of the battery. When the compaction density of the negative electrode active material layer meets the given range, the risk of a decrease in battery kinetic performance due to a high compaction density of the electrode sheet can be reduced on the basis of making the battery have a higher energy density, thereby making the battery have both a higher energy density and better kinetic performance. Furthermore, the compaction density of the negative electrode active material layer can be 1.4 g / cm 3 ~1.55g / cm 3 .

[0121] In the present application, the single-sided coating density of the negative electrode active material layer and the compaction density of the negative electrode active material layer can be determined by referring to the relevant test methods for the positive electrode sheet.

[0122] In some embodiments of the present application, the thickness of the negative electrode current collector is 6μm to 13μm, for example, it can be 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm or 13μm. Appropriately increasing the thickness of the negative electrode current collector can reduce the risk of damage to the negative electrode current collector at a higher compaction density, and the risk of the negative electrode pole piece breaking due to expansion during the charge and discharge cycle. Making the thickness of the current collector meet the given range can not only reduce the risk of the current collector breaking during the preparation of the pole piece and the risk of the pole piece breaking during the use of the battery, improve the cycle performance of the battery, but also take into account the energy density of the battery, reduce the adverse effects of the increase in the thickness of the current collector on the battery energy density, and enable the battery to have both higher energy density, better cycle stability and longer service life. Further, the thickness of the negative electrode current collector can be 8μm to 11μm.

[0123] In some embodiments of the present application, 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.

[0124] 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.

[0125] [Electrolyte]

[0126] In some embodiments of the present application, the battery cell may further include: an electrolyte, the electrolyte may include an organic solvent, and the organic solvent may include a cyclic carbonate and a linear carbonate.

[0127] For example, taking a lithium battery as an example, the electrolyte may include an organic solvent and a lithium salt, and the organic solvent may include a cyclic carbonate and a linear carbonate, thereby further facilitating the acquisition of a battery with a high energy density.

[0128] For example, the cyclic carbonate may include EC (ethylene carbonate) and / or PC (propylene carbonate), for example, EC. The linear carbonate may include one or more of EMC (ethyl methyl carbonate), DMC (dimethyl carbonate), and DEC (diethyl carbonate).

[0129] In some embodiments of the present application, based on the total mass of the electrolyte, the mass percentage of the cyclic carbonate can be 15% to 25%, and the mass percentage of the linear carbonate can be 50% to 70%. For example, based on the total mass of the electrolyte, the mass percentage of the cyclic carbonate can be 15%, 18%, 20%, 22% or 25%, etc.; the mass percentage of the linear carbonate can be 50%, 55%, 60%, 65% or 70%, etc. This is conducive to improving the stability of the electrolyte.

[0130] In some embodiments of the present application, the electrolyte may further include: additives, which may include FEC (fluoroethylene carbonate) and / or VC (vinylene carbonate). Adding FEC helps the positive electrode to form a stable CEI film, and forms a tough SEI film on the surface of the negative electrode, thereby reducing the Li consumption caused by the expansion of silicon-containing materials. Adding VC is conducive to forming a stable polycarbonate SEI film on the surface of the negative electrode, further improving the cycle performance of the battery.

[0131] In some embodiments of the present application, the electrolyte may optionally include other additives that can improve certain properties of the battery, such as additives that improve the battery's overcharge performance, additives that improve the battery's high temperature performance, additives that improve the battery's low temperature performance, and the like.

[0132] In some embodiments of the present application, the electrolyte further includes an electrolyte salt, and the electrolyte salt may include a lithium salt.

[0133] In some embodiments of the present application, the electrolyte may include an organic solvent, a lithium salt and an additive, the organic solvent may include a cyclic carbonate and a linear carbonate, wherein the cyclic carbonate may include EC, the linear carbonate may include one or more of EMC, DMC, and DEC, the additive may include FEC and VC, and the lithium salt may include LiPF6.

[0134] It is understandable that the concentration of lithium salt in the electrolyte and the mass percentage of additives in the electrolyte can be flexibly selected according to actual needs and are not particularly limited here.

[0135] [Isolation film]

[0136] Typically, the battery cell also includes a separator. In the present application, there is no particular restriction on the material of the separator, and any known porous structure separator with electrochemical stability and mechanical stability can be selected according to actual needs, such as but 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.

[0137] In some embodiments of the present application, a ceramic coating containing an inorganic oxide may be provided on the side of the separator 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, which 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.

[0138] In some embodiments of the present application, the isolation membrane may also be provided with a first bonding coating, and the first bonding coating may be located between the isolation membrane and the ceramic coating.

[0139] In some embodiments of the present application, a second bonding coating may be provided on the side of the separator facing the negative electrode plate.

[0140] Wherein, the first bonding coating and the second bonding coating may independently include but are not limited to polyvinylidene fluoride (PVDF) and / or polymethyl methacrylate (PMMA). Providing the first bonding coating and / or the second bonding coating is beneficial to saving the internal space of the battery and improving the volume energy density of the battery.

[0141] In some embodiments of the present application, the total thickness of the isolation film may be 7 μm to 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 further avoiding the risk of reducing the energy density of the battery due to the large thickness of the isolation film. Further, the total thickness of the isolation film may be 7 μm to 10 μm.

[0142] 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 cell may be a soft-pack battery, a square battery, or a cylindrical battery. Figure 1 The battery cell 1 is a square structure as an example.

[0143] In some embodiments of the present application, the battery cell may be a cylindrical battery, and the cylindrical battery may include a shell, and the shell may include an upper cover, a lower cover, and a side wall.

[0144] For example, the thickness of the side wall of the shell can be 0.2 mm to 0.4 mm, such as 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm or 0.4 mm, and can be 0.25 mm to 0.3 mm. This can make the shell side wall have a lower thickness and mass, which is conducive to further improving the battery energy density.

[0145] For example, the thickness of the shell wall of the upper cover or the lower cover of the shell can be 0.25mm to 0.45mm, such as 0.25mm, 0.3mm, 0.35mm, 0.4mm or 0.45mm, etc., and can be 0.27mm to 0.33mm. In this way, the upper cover or the lower cover of the shell can have a lower thickness and mass, which is conducive to further improving the energy density of the battery.

[0146] Exemplarily, in a cylindrical battery shell, a cap may be provided on the upper cover of the shell, and the cap may include a pole, and the pole ear of the positive pole piece may be connected to the pole through a first current collecting part; the pole ear of the negative pole piece may be connected to the shell wall of the lower cover of the shell through a second current collecting part. Optionally, the cap may be a steel cap. Providing a cap structure not only facilitates the welding connection of cylindrical batteries through current collecting parts (such as collectors, etc.), but also facilitates pressure relief after battery failure, and reduces the safety risks that may be caused by the large gas production of high-nickel and high-silicon system batteries due to thermal runaway.

[0147] In some embodiments, the battery cell may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0148] 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.

[0149] 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.

[0150] In some embodiments, the outer packaging of the battery cell may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0151] 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).

[0152] 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 power-consuming device may include at least one of a battery module, a battery pack, and an energy storage device.

[0153] 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.

[0154] Figure 2 2 is an example of a battery module 2. Figure 2In 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.

[0155] Figure 3 and 4 The battery pack 3 is used as an example. Figure 3 and 4 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.

[0156] 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.

[0157] 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.

[0158] Figure 5 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 light and thin, and a battery cell may be used as a power source.

[0159] 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.

[0160] Example 1

[0161] (1) Positive electrode

[0162] The positive electrode current collector aluminum foil is provided with positive electrode active material layers on two surfaces of the aluminum foil that are arranged opposite to each other. The thickness of the positive electrode active material layers arranged on the two surfaces of the aluminum foil is equal. The thickness of the aluminum foil is 17 μm. The thickness of the current collector in the positive electrode sheet accounts for 10%. The single-sided coating surface density of the positive electrode active material layer is 25.6 mg / cm 2 , based on the mass of the positive electrode active material layer, including 98% by mass of the positive electrode active material (i.e., the ternary active material nickel cobalt manganese oxide (metal oxide), the molar ratio of nickel, cobalt and manganese is 0.83:0.11:0.06, the particle size distribution diagram of the positive electrode active material presents a unimodal distribution, and the peak value of the particle size distribution peak corresponds to a particle size of 8.3μm), 1.1% by mass of the conductive agent (conductive carbon black Super P), and 0.9% by mass of the binder polyvinylidene fluoride (PVDF).

[0163] (2) Negative electrode

[0164] The negative electrode current collector copper foil is provided with a negative electrode active material layer on two surfaces of the copper foil which are arranged opposite to each other. The thickness of the negative electrode active material layers arranged on the two surfaces of the copper foil is equal. The thickness of the copper foil is 10 μm. The thickness of the current collector in the negative electrode sheet accounts for 5%. The single-sided coating surface density of the negative electrode active material layer is 14 mg / cm 2 The negative electrode active material includes natural graphite and silicon-containing material SiO. Based on the mass of the negative electrode active material layer, it includes 96% of the positive electrode active material by mass (based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material is 2.3%), 0.8% of the conductive agent (Super P) by mass, 2% of the binder styrene-butadiene rubber (SBR) by mass, and 1.2% of the thickener sodium carboxymethyl cellulose (CMC-Na) by mass.

[0165] (3) Electrolyte

[0166] It includes an organic solvent and an electrolyte salt. The organic solvent is prepared by EC, DMC and EMC in a mass ratio of 28:36:34. The electrolyte salt is LiPF6. The concentration of LiPF6 in the electrolyte is 1 mol / L.

[0167] (4) Isolation film: polyethylene film.

[0168] (5) Battery cell: including the above-mentioned positive electrode sheet, negative electrode sheet, separator and electrolyte.

[0169] Test method:

[0170] (1) Elemental composition test by inductively coupled plasma optical emission spectrometry

[0171] The instrument standard refers to EPA6010D-2014 "Inductively Coupled Plasma Atomic Emission Spectrometry". The sample is treated by chemical methods to be digested into a solution, atomized into plasma and excited to produce characteristic spectral lines of the elements. The element content is qualitatively and quantitatively analyzed based on the wavelength and intensity of the spectral lines (which are proportional to the concentration).

[0172] (2) Particle size test of positive electrode active material

[0173] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009, specific test process: take an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8-12% shading), add 20ml of deionized water, and ultrasonicate for 5min (53KHz / 120W) to ensure that the sample is completely dispersed, and then measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0174] (3) Energy density test

[0175] At 25°C, first use a steel ruler to measure the length, width and height of the battery cell (the height of the pole is not included), record the volume V, charge it to 4.25V at a constant current of 1 / 3C, then charge it to a current of 0.05C at a constant voltage of 4.25V, leave it for 5 minutes, then discharge it to 2.5V at 1 / 3C, cycle it 3 times, take the discharge energy of the third cycle and record it as W, the volume energy density of the battery cell = W / V.

[0176] (4) Cyclic performance test

[0177] At 25°C, let the formed battery stand for 30 minutes, and discharge it to 2.8V 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 4.15V at a constant current of 1 / 2C, then charge it at a constant voltage until the current drops to 0.05C; let it stand for 5 minutes; discharge it to 2.8V at a constant current of 1 / 2C, and record the discharge capacity at this time as C0. After 500 cycles, record the discharge capacity C0 at the 500th cycle. 500 The capacity retention rate after 500 cycles is calculated according to the following formula:

[0178] Capacity retention rate after 500 cycles (%): C 500 / C0×100%.

[0179] (5) High temperature storage performance test

[0180] The battery was charged to 4.25V at a constant current of 1 / 3C at 25°C, then charged at a constant voltage of 4.25V until the current dropped to 0.05C, and then discharged to 2.5V at a constant current of 1 / 3C. The discharge capacity before storage (C d1 ); then the battery is charged again at a constant current of 1 / 3C to 4.15V, and then charged at a constant voltage of 4.15V until the current drops to 0.05C. The battery is then placed in a 45°C constant temperature box for 150 days, taken out and placed at 25°C and charged at a constant current of 1 / 3C to 4.25V, and then charged at a constant voltage of 4.25V until the current drops to 0.05C, and then discharged at a constant current of 1 / 3C to 2.5V, and the discharge capacity after storage (C d2 ). The high temperature storage capacity retention rate (%) is calculated according to the following formula: C d2 / C d1 ×100%.

[0181] Example 2, Example 3, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2

[0182] The positive electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that in the negative electrode plate, the mass proportion of the silicon-containing material in the negative electrode active material is different, and the mass proportion of the silicon element in the negative electrode active material is also different, but the mass proportion of the negative electrode active material in the negative electrode active material layer is the same as in Example 1.

[0183] Example 6

[0184] The positive electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the type of silicon-containing material in the negative electrode plate is different, and the silicon-containing material is SiC. The mass proportion of silicon element in the negative electrode active material varies with the change of the silicon-containing material, but the mass proportion of silicon-containing material in the negative electrode active material is the same as that in Example 1.

[0185] Example 7, Example 8, Example 9, Comparative Example 3, Comparative Example 4

[0186] The positive electrode sheet and electrolyte in the battery cell are the same as those in Example 1, except that the thickness of the negative electrode collector in the negative electrode sheet is different, and the thickness ratio of the negative electrode collector in the negative electrode sheet is also different.

[0187] The differences between Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 1.

[0188] Table 1

[0189]

[0190] In combination with Examples 1 to 9, as well as Comparative Examples 1 and 2, it can be seen that the battery cell proposed in the present application has both high energy density and cycle capacity retention rate, indicating that the present application uses high-nickel positive electrode active materials in the positive electrode plate, and graphite and silicon-containing materials are used in combination in the negative electrode plate, and the amount of silicon-containing material added in the negative electrode plate and the thickness ratio of the current collector in the negative electrode plate are controlled within an appropriate range, so that the battery cell can have both high energy density and long cycle life.

[0191] Combining Examples 1 to 5, Comparative Examples 1 and 2, it can be seen that as the silicon content in the negative electrode sheet increases, the volume energy density of the battery cell shows a trend of first increasing and then decreasing, while the cycle capacity retention rate and high-temperature storage performance of the battery cell show a downward trend. The reason for this may be the cracking or damage of the active material layer of the negative electrode sheet caused by excessive silicon-containing material content. This shows that controlling the amount of silicon-containing material in the negative electrode active material within an appropriate range can better balance the energy density and cycle performance of the battery cell, thereby facilitating a longer service life.

[0192] Combining Example 1, Example 7 to Example 9, and Comparative Example 3 and Comparative Example 4, it can be seen that as the thickness ratio of the current collector in the negative electrode sheet increases, the cycle capacity retention rate and high temperature storage performance of the battery cell first increase and then tend to stabilize, while the volume energy density of the battery cell shows a downward trend. This shows that appropriately increasing the thickness ratio of the current collector in the negative electrode sheet can not only improve the cycle capacity retention rate of the battery cell, but also take into account the volume energy density of the battery cell, so that the battery cell has both high energy density and good cycle performance, which is conducive to obtaining a longer service life.

[0193] It can be seen from the combination of Example 1 and Example 6 that the use of silicon-carbon materials instead of silicon-oxygen materials in combination with graphite can also improve the energy density of battery cells.

[0194] Example 10, Example 11, Example 12, Example 13, Example 14

[0195] The negative electrode sheet and electrolyte in the battery cell are the same as those in Example 1, except that the thickness of the positive electrode collector in the positive electrode sheet is different, and the thickness ratio of the positive electrode collector in the positive electrode sheet is also different.

[0196] The differences between Examples 10 to 14 and Example 1 are shown in Table 2.

[0197] Table 2

[0198]

[0199] Combining Example 1, Example 10 to Example 14, it can be seen that as the thickness ratio of the current collector in the positive electrode sheet increases, the cycle capacity retention rate and high temperature storage performance of the battery cell first increase and then tend to stabilize, while the volume energy density of the battery cell decreases. This shows that appropriately increasing the thickness ratio of the positive electrode current collector can further improve the cycle capacity retention rate of the battery cell, while taking into account the volume energy density of the battery cell, so that the battery cell has both higher energy density and better cycle performance, which is conducive to obtaining a longer service life.

[0200] Embodiment 15

[0201] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 1, except that the type of ternary active material in the positive electrode plate is different. The ternary active material in Example 15 is lithium nickel cobalt aluminum oxide (metal oxide), and the molar ratio of nickel, cobalt and aluminum in the lithium nickel cobalt aluminum oxide is 0.91:0.05:0.04.

[0202] Comparative Example 5

[0203] The electrolyte in the battery cell is the same as that in Example 15, except that in the positive electrode sheet, the thickness of the positive electrode collector is different, and the thickness ratio of the positive electrode collector in the positive electrode sheet is also different; in the negative electrode sheet, the thickness of the negative electrode collector is different, and the thickness ratio of the negative electrode collector in the negative electrode sheet is also different.

[0204] Comparative Example 6, Comparative Example 7

[0205] The positive electrode plate and electrolyte in the battery cell are the same as those in Example 10, except that in the negative electrode plate, the mass proportion of the silicon-containing material in the negative electrode active material is different, and the mass proportion of the silicon element in the negative electrode active material is also different, but the mass proportion of the negative electrode active material in the negative electrode active material layer is the same as that in Example 15.

[0206] The differences between Example 15, Comparative Example 5, Comparative Example 6 and Comparative Example 7 are shown in Table 3.

[0207] Table 3

[0208]

[0209] Example 16, Example 17, Example 18, Example 19

[0210] 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, a lithium supplement is also added to the positive electrode active material, that is, the positive electrode active material includes a ternary active material and a lithium supplement, but the mass proportion of the positive electrode active material in the positive electrode active material layer is the same as in Example 1.

[0211] Comparative Example 8

[0212] The electrolyte in the battery cell is the same as that in Example 1, except that, in the positive electrode plate, a lithium supplement is further added to the positive electrode active material, that is, the positive electrode active material includes a ternary active material and a lithium supplement, but the mass proportion of the positive electrode active material in the positive electrode active material layer is the same as in Example 1; in the negative electrode plate, the negative electrode active material only includes natural graphite and does not contain silicon-containing material, and the mass proportion of silicon element in the negative electrode active material is also different, but the mass proportion of the negative electrode active material in the negative electrode active material layer is the same as in Example 1.

[0213] The differences between Example 16, Example 17, Example 18, Example 19 and Comparative Example 8 and Example 1 are shown in Table 4.

[0214] Table 4

[0215]

[0216]

[0217] It can be seen from Example 1 and Example 16 to Example 19 that the addition of a lithium supplement can significantly improve the cycle capacity retention rate and high-temperature storage capacity retention rate of the battery cell, and as the amount of the lithium supplement increases, the cycle capacity retention rate and high-temperature storage capacity retention rate of the battery cell also increase accordingly, but 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 content of the lithium supplement is relatively high, the relative amount of the ternary active material decreases, and the improvement effect of the lithium supplement on the energy density of the battery cell is not enough to compensate for the effect of the reduction in the amount of the ternary active material on the energy density of the battery cell. This shows that appropriately increasing the amount of the lithium supplement is beneficial to further enable the battery cell to have both higher energy density, better cycle performance and high-temperature storage performance. In addition, based on Example 16 and in combination with Comparative Example 8, it can be further illustrated that the energy density and cycle performance of the battery cell can be balanced by adjusting the amount of silicon-containing material in the negative electrode plate.

[0218] Embodiment 20

[0219] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 16, except that in the positive electrode plate, the particle size distribution of the positive electrode active material is different. The particle size distribution diagram of the positive electrode active material in Example 20 presents a bimodal distribution, and the peak value of the small particle size peak corresponds to a particle size of 1 μm, and the peak value of the large particle size peak corresponds to a particle size of 9 μm.

[0220] Embodiment 21

[0221] The positive electrode plate and electrolyte in the battery cell are the same as those in Example 16, except that in the negative electrode plate, the surface of the silicon-containing material is coated with carbon material.

[0222] The differences between Example 16, Example 20 and Example 21 are shown in Table 5.

[0223] Table 4

[0224]

[0225] Combining Example 16 and Example 20, it can be seen that the energy density of the battery cell with a bimodal distribution diagram of the positive electrode active material particle size is improved, indicating that using a combination of large and small particle sizes of the positive electrode active material in the positive electrode plate is beneficial to further enable the battery cell to have both higher energy density and better cycle performance, thereby extending the service life of the battery cell.

[0226] It can be seen from Example 16 and Example 21 that coating the surface of the silicon-containing material in the negative electrode plate with carbon material is beneficial to further improve the energy density and cycle performance of the battery cell. In addition, the high-temperature storage performance of the battery cell is also improved.

[0227] Example 22, Example 23, Example 24, Example 25, Example 26

[0228] The negative electrode plate and electrolyte in the battery cell are the same as those in Example 16, except that in the positive electrode plate, the ternary active material lithium nickel cobalt manganese oxide has doped elements.

[0229] Example 27, Example 28

[0230] The positive electrode plate and electrolyte in the battery cell are the same as those in Example 16, except that in the negative electrode plate, the silicon oxide material is doped with metal elements.

[0231] The differences between Examples 22 to 28 and Example 16 are shown in Table 6.

[0232] Table 6

[0233]

[0234] It can be seen from Example 16 and Examples 22 to 26 that doping a small amount of other elements, such as Al, Zr, B, etc., into the ternary active material lithium nickel cobalt manganese oxide is beneficial to further improve the cycle performance of the battery cell.

[0235] It can be seen from Example 16 and Examples 27 to 28 that doping a small amount of metal elements, such as Fe or Co, into the silicon-containing material is beneficial to further improve the energy density of the battery.

[0236] 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, comprising a positive electrode sheet and a negative electrode sheet, characterized in that: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, wherein: The positive electrode active material comprises nickel-cobalt-manganese metal oxide, and the molar proportion of nickel in the nickel-cobalt-manganese metal oxide is 80% to 96% based on the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese metal oxide, or, The positive electrode active material comprises nickel-cobalt-aluminum metal oxide, and based on the total molar amount of nickel, cobalt and aluminum elements in the nickel-cobalt-aluminum metal oxide, the molar proportion of nickel element in the nickel-cobalt-aluminum metal oxide is 80% to 96%; The negative electrode active material includes graphite and silicon-containing material. Based on the total mass of the negative electrode active material, the mass proportion of silicon element in the negative electrode active material is 0.1% to 10%, and the thickness of the negative electrode collector is 3% to 8% of the total thickness of the negative electrode sheet.

2. The battery cell according to claim 1, characterized in that: Based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material is 0.5% to 9.5%, and can be optionally 2% to 9.5%.

3. The battery cell according to claim 1 or 2, characterized in that: The thickness of the negative electrode current collector is 4% to 7% of the total thickness of the negative electrode plate.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The thickness of the positive electrode current collector is 7.5% to 15% of the total thickness of the positive electrode plate, and can be optionally 10% to 13.5%.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The positive electrode active material comprises nickel-cobalt-manganese metal oxide, and based on the total molar amount of nickel, cobalt and manganese elements in the nickel-cobalt-manganese metal oxide, the molar proportion of nickel in the nickel-cobalt-manganese metal oxide is 83% to 91%; or The positive electrode active material comprises nickel-cobalt-aluminum metal oxide, and based on the total molar amount of nickel, cobalt and aluminum elements in the nickel-cobalt-aluminum metal oxide, the molar proportion of nickel element in the nickel-cobalt-aluminum metal oxide is 83% to 91%.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The silicon-containing material includes silicon-oxygen material and / or silicon-carbon material.

7. The battery cell according to any one of claims 1 to 6, characterized in that: Based on the total mass of the negative electrode active material, the mass proportion of silicon in the negative electrode active material is 2% to 6%, and can be optionally 3% to 5%.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The silicon-containing material further includes metal elements, and the metal elements include one or more elements of Na, Li, Ti, Fe, and Co.

9. The battery cell according to claim 8, characterized in that: The mass of the metal element is 0.1% to 0.6% of the mass of the silicon element.

10. The battery cell according to any one of claims 1 to 9, characterized in that: At least a portion of the surface of the silicon-containing material includes a carbon coating layer.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The graphite includes natural graphite.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The positive active material includes a polycrystalline material.

13. The battery cell according to any one of claims 1 to 12, characterized in that: The particle size distribution diagram of the positive electrode active material presents a bimodal distribution, and the particle sizes corresponding to the peak values ​​of the two peaks are D1 and D2, respectively, 0.5 μm≤D1≤1.5 μm, 7 μm≤D2≤12 μm.

14. The battery cell according to any one of claims 1 to 13, characterized in that: The positive electrode active material also includes a lithium supplement.

15. The battery cell according to claim 14, characterized in that: The lithium supplement comprises Li x M y O z , 1≤x≤5, 1≤y≤3, 1≤z≤8, M includes one or more elements selected from Ni, Co, V, Cr, Mn, Fe, Mo, Cu, and Zn.

16. The battery cell according to claim 14 or 15, characterized in that: The lithium supplement includes Li2NiO2 and / or Li5FeO4.

17. The battery cell according to claim 14 or 15, 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.

18. The battery cell according to claim 14 or 15, 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.

19. The battery cell according to any one of claims 14 to 18, characterized in that: Based on the total mass of the positive electrode active material, the mass proportion of the lithium supplement agent is 0.5% to 5%, and can be optionally 1% to 3%.

20. The battery cell according to any one of claims 1 to 19, characterized in that: The positive electrode active material includes nickel cobalt manganese metal oxide, and the nickel cobalt manganese metal oxide includes one or more elements of Na, K, Mg, B, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F, and may optionally include one or more elements of Al, Zr, B, P, and Ti.

21. The battery cell according to claim 20, characterized in that: The nickel-cobalt-manganese metal oxide includes Al element, and based on the total mass of the positive electrode active material, the mass proportion of the Al element is 0.01% to 0.1%.

22. The battery cell according to claim 20 or 21, characterized in that: The nickel-cobalt-manganese metal oxide includes a Zr element, and based on the total mass of the positive electrode active material, the mass proportion of the Zr element is 0.1% to 0.5%.

23. The battery cell according to any one of claims 20 to 22, characterized in that: The nickel-cobalt-manganese metal oxide includes a B element, and based on the total mass of the positive electrode active material, the mass proportion of the B element is 0.01% to 0.15%.

24. The battery cell according to any one of claims 20 to 23, characterized in that: The nickel-cobalt-manganese metal oxide includes a P element, and based on the total mass of the positive electrode active material, the mass proportion of the P element is 0.05% to 0.2%.

25. The battery cell according to any one of claims 1 to 24, characterized in that: The single-sided coating density of the positive electrode active material layer is 20 mg / cm 2 ~30mg / cm 2 .

26. The battery cell according to any one of claims 1 to 25, characterized in that: The compaction density of the positive electrode active material layer is 3.3 g / cm 3 ~3.6g / cm 3 .

27. The battery cell according to any one of claims 1 to 26, characterized in that: The thickness of the positive electrode current collector is 13 μm to 19 μm, and can be optionally 15 μm to 17 μm.

28. The battery cell according to any one of claims 1 to 27, characterized in that: The single-sided coating density of the negative electrode active material layer is 10 mg / cm 2 ~18mg / cm 2 , optional 13mg / cm 2 ~15mg / cm 2 .

29. The battery cell according to any one of claims 1 to 28, characterized in that: The compaction density of the negative electrode active material layer is 1.3 g / cm 3 ~1.7g / cm 3 , optional 1.4g / cm 3 ~1.55g / cm 3 .

30. The battery cell according to any one of claims 1 to 29, characterized in that: The thickness of the negative electrode current collector is 6 μm to 13 μm, and can be 8 μm to 11 μm.

31. The battery cell according to any one of claims 1 to 30, characterized in that: Also includes: The electrolyte comprises an organic solvent, wherein the organic solvent comprises a cyclic carbonate and a linear carbonate.

32. The battery cell according to claim 31, characterized in that: The cyclic carbonate includes EC and / or PC, and the linear carbonate includes one or more of EMC, DMC and DEC.

33. The battery cell according to claim 31 or 32, characterized in that: Based on the total mass of the electrolyte, the mass proportion of the cyclic carbonate is 15% to 25%, and the mass proportion of the linear carbonate is 50% to 70%.

34. The battery cell according to any one of claims 31 to 33, characterized in that: The electrolyte further comprises: an additive, wherein the additive comprises FEC and / or VC.

35. The battery cell according to any one of claims 1 to 34, characterized in that: Also includes: A separator, wherein a ceramic coating containing an inorganic oxide is disposed on a side of the separator facing the positive electrode plate.

36. The battery cell according to claim 35, characterized in that The isolation membrane is also provided with a first bonding coating, and the first bonding coating is located between the isolation membrane and the ceramic coating.

37. The battery cell according to claim 35 or 36, characterized in that: A second bonding coating is provided on a side of the separator facing the negative electrode plate.

38. The battery cell according to any one of claims 35 to 37, characterized in that: The total thickness of the isolation film is 7 μm to 14 μm, and can be optionally 7 μm to 10 μm.

39. The battery cell according to any one of claims 1 to 38, characterized in that: The battery cell is a cylindrical battery, which includes a shell, which includes an upper cover, a lower cover and a side wall, and the thickness of the side wall is 0.2 mm to 0.4 mm, and can be optionally 0.25 mm to 0.3 mm.

40. The battery cell according to claim 39, characterized in that The thickness of the shell wall of the upper cover or the lower cover is 0.25 mm to 0.45 mm, and can be optionally 0.27 mm to 0.33 mm.

41. A battery device, characterized in that: The invention comprises a battery cell as claimed in any one of claims 1 to 40, wherein the electrical device comprises at least one of a battery module, a battery pack and an energy storage device.

42. An electrical device, characterized in that: The invention comprises the battery cell according to any one of claims 1 to 40 or the battery device according to claim 41, wherein the battery cell or the battery device is used to provide electrical energy.

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