Battery monomer, battery device and power utilization device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, wherein the electrode assembly comprises a positive plate, a negative plate and a non-aqueous electrolyte; the positive pole piece comprises a positive current collector and a positive film layer, and the negative pole piece comprises a negative current collector and a negative film layer; wherein the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium iron phosphate material and a nickel cobalt lithium manganate material; in the positive electrode active material, the molar ratio of the Ni element to the sum of the three elements of Ni, Co and Mn is 0.5-0.95; the non-aqueous electrolyte comprises vinylene carbonate, and the mass content of the vinylene carbonate in the non-aqueous electrolyte is 0.5%-2%; the non-aqueous electrolyte comprises at least one of linear carbonic ester and linear carboxylic ester, and the conductivity of the non-aqueous electrolyte is 9-14 mS / cm. The energy density, the cycle performance and the power performance of the battery monomer are improved at the same time.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device and an electrical device. Background Art

[0002] In recent years, as the application scope of batteries has become more and more extensive, batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance, etc. Summary of the invention

[0003] The present application is made in view of the above problems, and its purpose is to provide a battery cell, a battery device and an electric device. The energy density, cycle performance and power performance of the battery cell of the present application are improved at the same time.

[0004] In order to achieve the above-mentioned object, the first aspect of the present application provides a battery cell, including an electrode assembly, wherein the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte; the positive electrode sheet includes a positive electrode collector and a positive electrode film layer located on at least one side of the positive electrode collector, and the negative electrode sheet includes a negative electrode collector and a negative electrode film layer located on at least one side of the negative electrode collector; wherein,

[0005] The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium iron phosphate material and a nickel cobalt manganese oxide lithium material; in the positive electrode active material, the molar proportion of Ni element in the sum of the three elements of Ni, Co and Mn is 0.5-0.95;

[0006] The non-aqueous electrolyte includes vinylene carbonate, and the mass content of the vinylene carbonate in the non-aqueous electrolyte is 0.5%-2%;

[0007] The non-aqueous electrolyte includes at least one of a linear carbonate and a linear carboxylate, and the conductivity of the non-aqueous electrolyte is 9-14 mS / cm.

[0008] Therefore, the non-aqueous electrolyte of the present application includes a certain amount of vinylene carbonate, which is conducive to forming a stable component on the surface of the negative electrode to improve the stability of the negative electrode SEI film and can reduce the SEI film impedance; at the same time, the conductivity of the electrolyte is within a certain range, which is conducive to compensating for the power loss caused by the increase in SEI film impedance, and is also conducive to compensating for the power loss caused by the mixing of lithium iron phosphate materials, and is also conducive to reducing the negative impact of excessive conductivity on high-temperature cycle performance, ensuring that the battery has a high energy density while improving the battery's cycle performance and power performance.

[0009] In any embodiment, the non-aqueous electrolyte includes a linear carbonate, the linear carbonate includes dimethyl carbonate, and the mass content of the dimethyl carbonate in the non-aqueous electrolyte is 4%-20% or 8%-16%. Thus, adjusting the conductivity of the electrolyte by a certain amount of dimethyl carbonate is conducive to improving the power performance of the battery while ensuring the high temperature cycle performance of the battery.

[0010] In any embodiment, the non-aqueous electrolyte includes a linear carboxylic acid ester, and the mass content of the linear carboxylic acid ester in the non-aqueous electrolyte is 5%-25%.

[0011] In any embodiment, the linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate, and ethyl acetate.

[0012] Therefore, adjusting the conductivity of the electrolyte by adding a certain amount of linear carboxylic acid ester is beneficial to improving the power performance of the battery while ensuring the high temperature cycle performance of the battery.

[0013] In any embodiment, the viscosity of the non-aqueous electrolyte at room temperature is 1-3 mPa·s or 2-3 mPa·s.

[0014] In any embodiment, when the mass proportion of the lithium nickel cobalt manganese oxide material in the positive electrode active material is ≥10%, the non-aqueous electrolyte further includes a substance containing a sulfur-oxygen bond, and the substance containing a sulfur-oxygen bond includes at least one of vinyl sulfate and 1,3-propane sultone.

[0015] In any embodiment, the mass content of the substance containing sulfur-oxygen bonds in the non-aqueous electrolyte is 0.5%-4% or 0.5%-2%.

[0016] Therefore, when the mass proportion of nickel cobalt manganese oxide material in the positive electrode active material is ≥10%, in order to facilitate the capacity advantage of nickel cobalt manganese oxide material, the upper limit voltage of the battery is based on the nickel cobalt manganese oxide material. Under high pressure, substances containing sulfur-oxygen bonds form a film at the positive electrode, which optimizes the positive electrode interface film component, inhibits the side reaction between the residual alkali on the surface of the nickel cobalt manganese oxide material and the acidic substances in the electrolyte, and improves the battery cycle performance.

[0017] In any embodiment, in the non-aqueous electrolyte, a mass ratio of the 1,3-propane sultone to the vinyl sulfate is greater than 0 and less than 1.

[0018] Therefore, the mass of vinyl sulfate is greater than that of 1,3-propane sultone, which can reduce the impedance of the positive electrode interface film and improve the power performance of the battery.

[0019] In any embodiment, the non-aqueous electrolyte further comprises a lithium salt, and the mass content of the lithium salt in the non-aqueous electrolyte is 12%-16%.

[0020] In any embodiment, when the mass proportion of the nickel cobalt manganese oxide material in the positive electrode active material is ≥20%, the lithium salt includes lithium hexafluorophosphate and a fluorosulfonamide lithium salt, and the fluorosulfonamide lithium salt includes at least one of monofluorosulfonyl imide lithium, bisfluorosulfonyl imide lithium, and trifluorosulfonyl imide lithium.

[0021] Therefore, the inclusion of lithium hexafluorophosphate and fluorosulfonamide lithium salts in the non-aqueous electrolyte can increase the heat resistance temperature of the electrolyte, thereby reducing the risk of thermal runaway of the positive electrode caused by the heat instability of the electrolyte; at the same time, it is also beneficial to improve the cycle performance and power performance of the battery.

[0022] In any embodiment, the lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonyl imide, and the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonyl imide is 1.23:1-4.28:1.

[0023] Therefore, the ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide within the above range can, on the one hand, reduce the risk of thermal runaway of the positive electrode caused by the heat instability of the electrolyte, and on the other hand, reduce the negative impact of lithium bis(fluorosulfonyl)imide on the safety performance of the negative electrode, thereby improving the safety performance of the battery.

[0024] In any embodiment, the non-aqueous electrolyte further comprises ethylene carbonate, and the mass content of the ethylene carbonate in the non-aqueous electrolyte is 12%-35%.

[0025] Therefore, on the one hand, including ethylene carbonate in the non-aqueous electrolyte is beneficial to reducing the impedance of the interface film, thereby improving the power performance of the battery while ensuring the battery cycle performance; on the other hand, the above content can inhibit the side reaction of ethylene carbonate with the positive electrode active material, thereby improving the cycle performance and safety performance of the battery.

[0026] In any embodiment, the mass content of Ni element in the positive electrode film layer is 4.5%-25%, the mass content of Fe element in the positive electrode film layer is 15%-33%, and the mass content of vinylene carbonate in the non-aqueous electrolyte is 1%-1.5%.

[0027] In any embodiment, the mass proportion of the lithium iron phosphate material in the positive electrode active material is 50%-90%.

[0028] Therefore, when the mass proportion of lithium iron phosphate material in the positive electrode active material is high, the structural stability is increased, which can improve the cycle performance and safety performance.

[0029] In any embodiment, the mass proportion of the lithium iron phosphate material in the positive electrode active material is 60%-80%; in the positive electrode active material, the molar proportion of Ni element in the sum of the three elements Ni, Co and Mn is 0.7-0.95.

[0030] As a result, the battery has both good energy density and cycle performance while maintaining cost advantages.

[0031] In any embodiment, the lithium iron phosphate material also includes one or more elements of Al, B, Ca, Cr, K, Mg, Ni, Co, Mn, Na, Si, Ti, V, Cu, Zn, S, Sc, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Cl, C, N, and F.

[0032] In any embodiment, the lithium iron phosphate material includes one or more of the following:

[0033] The mass percentage of Al element in the lithium iron phosphate material is 0.01%-0.02%;

[0034] The mass percentage of element B in the lithium iron phosphate material is 0.08%-0.09%;

[0035] The mass percentage of Ca element in the lithium iron phosphate material is 0.0001%-0.0003%;

[0036] The mass proportion of Fe element in the lithium iron phosphate material is 16.035%-35%;

[0037] The mass proportion of K element in the lithium iron phosphate material is 0.0022%-0.0050%;

[0038] The mass proportion of Li element in the lithium iron phosphate material is 3%-4.5%;

[0039] The mass percentage of Mg element in the lithium iron phosphate material is 0.00235%-0.0052%;

[0040] The mass percentage of Mn element in the lithium iron phosphate material is 0.00205%-0.0050%;

[0041] The mass percentage of the Na element in the lithium iron phosphate material is 0.018%-0.05%;

[0042] The mass proportion of P element in the lithium iron phosphate material is 9.265%-19.5%;

[0043] The mass percentage of Si element in the lithium iron phosphate material is 0.0065%-0.02%;

[0044] The mass percentage of Ti element in the lithium iron phosphate material is 0.074%-0.16%;

[0045] The mass proportion of V element in the lithium iron phosphate material is 0.0003%-0.0008%;

[0046] The mass percentage of Cr element in the lithium iron phosphate material is 0.0004%-0.0012%;

[0047] The mass proportion of Zn element in the lithium iron phosphate material is 0.00005%-0.0003%.

[0048] In any embodiment, the lithium nickel cobalt manganese oxide material also includes one or more elements of Al, B, Fe, Sr, Ti, Y, Zr, Na, K, Mg, Si, P, S, Ca, Sc, V, Cr, Cu, Zn, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F.

[0049] In any embodiment, the lithium nickel cobalt manganese oxide material includes one or more of the following:

[0050] The mass percentage of Al element in the nickel cobalt lithium manganese oxide material is 0.0315%-0.07%;

[0051] The mass percentage of element B in the nickel cobalt manganese oxide material is 0.00195%-0.005%;

[0052] The mass percentage of Co element in the lithium nickel cobalt manganese oxide material is 3.825%-8%;

[0053] The mass percentage of Fe element in the nickel cobalt manganese oxide material is 0.0016%-0.005%;

[0054] The mass proportion of Li element in the nickel cobalt manganese oxide material is 5.5%-6.8%;

[0055] The mass percentage of Mn element in the lithium nickel cobalt manganese oxide material is 1.22%-2.8%;

[0056] The mass proportion of Ni element in the lithium nickel cobalt manganese oxide material is 24.93%-51%;

[0057] The mass percentage of Sr element in the nickel cobalt manganese oxide material is 0.00005%-0.0002%;

[0058] The mass percentage of Ti element in the nickel cobalt lithium manganese oxide material is 0.00015%-0.0004%;

[0059] The mass proportion of Y element in the nickel cobalt manganese oxide material is 0.0004%-0.0009%;

[0060] The mass proportion of Zr element in the lithium nickel cobalt manganese oxide material is 0.128%-0.3%.

[0061] In any embodiment, the lithium nickel cobalt manganese oxide material includes spherical particles, and the lithium iron phosphate material includes particles having a shape suitable for filling the gaps between the spherical particles. Thus, the compaction density of the positive electrode active material is increased, thereby improving the energy density of the battery.

[0062] In any embodiment, the nickel cobalt manganese oxide material is a polycrystalline material. Therefore, the use of polycrystalline nickel cobalt manganese oxide material is beneficial to improving the power of the battery.

[0063] In any embodiment, the nickel cobalt manganese oxide material includes particles with a maximum diameter of 4-8 μm and particles with a maximum diameter of 0.5-2 μm. Thus, the combination of nickel cobalt manganese oxide particles of different particle sizes is beneficial to increase the compaction density of the positive electrode active material and the energy density of the battery.

[0064] In any embodiment, the lithium iron phosphate material includes particles with a longest diameter of 0.1-0.3 μm and particles with a longest diameter of 1-2 μm. Thus, the combination of lithium iron phosphate particles of different particle sizes is beneficial to increase the compaction density of the positive electrode active material and improve the energy density of the battery.

[0065] In any embodiment, the positive electrode film layer further includes a lithium supplement material, and the lithium supplement material includes one or more of lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, and trilithium citrate. This is beneficial to improving the energy density of the battery.

[0066] In any embodiment, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite and silicon material, and the mass proportion of silicon in the negative electrode film layer is 0.3%-10%, which is conducive to improving the energy density of the battery.

[0067] In any embodiment, the silicon material includes one or more of silicon oxide and silicon-carbon composite.

[0068] In any embodiment, the silicon material comprises a silicon-carbon composite, and the mass proportion of silicon in the negative electrode film layer is 1%-5%, which is beneficial to improve the energy density of the battery.

[0069] In any embodiment, the surface density of the positive electrode film layer is 0.32-0.36 mg / 1540.25 mm 2 .

[0070] In any embodiment, the surface density of the negative electrode film layer is 0.169-0.190 mg / 1540.25 mm 2 .

[0071] This helps to increase the energy density of the battery.

[0072] In any embodiment, the ratio of the size of the positive electrode film layer in the first direction to the size of the battery cell in the first direction is ≥92%.

[0073] In any embodiment, the ratio of the size of the positive electrode film layer in the second direction to the size of the battery cell in the second direction is ≥93%, and the second direction is perpendicular to the first direction.

[0074] This is beneficial to improving the utilization rate of the electrode assembly.

[0075] In any embodiment, in the battery cell configured to be in a 0% SOC state, a thickness ratio of the positive electrode film layer on any side of the positive electrode collector to the positive electrode collector is 5-8.

[0076] In any embodiment, in the battery cell configured to be in a 0% SOC state, a thickness ratio of the negative electrode film layer on any side of the negative electrode current collector to the negative electrode current collector is 13-20.

[0077] As a result, the energy density and dynamic performance of the battery are improved at the same time.

[0078] In any embodiment, the negative electrode film layer includes a first negative electrode film layer located on the negative electrode current collector and a second negative electrode film layer located on the first negative electrode film layer, and the first negative electrode film layer and the second negative electrode film layer include graphite, thereby further improving the dynamic performance of the battery.

[0079] In any embodiment, the thickness of the positive electrode current collector is 10-13 μm.

[0080] In any embodiment, the thickness of the negative electrode current collector is 4-5.5 μm.

[0081] This improves the energy density of the battery.

[0082] In any embodiment, the electrode assembly includes at least two positive electrode sheets and at least two negative electrode sheets, and the positive electrode sheets and the negative electrode sheets are stacked; the positive electrode sheets and / or the negative electrode sheets include a pole ear portion and a main body portion, the pole ear portion extends from the main body portion along a first direction, and the ratio of the total dimension L1 of the connecting area between the pole ear portion and the main body portion in the second direction to the dimension L of the main body portion in the second direction is ≥50%, and the second direction is perpendicular to the first direction.

[0083] In any embodiment, the battery cell includes at least two poles of the same polarity, and the poles are directly electrically connected to the pole lugs of the corresponding polarity.

[0084] In any embodiment, the battery cell includes two positive electrode posts and two negative electrode posts, the two positive electrode posts are respectively arranged on two side surfaces of the battery cell perpendicular to the first direction, the two negative electrode posts are respectively arranged on two side surfaces of the battery cell perpendicular to the first direction, and the positive electrode posts and the negative electrode posts are arranged opposite to each other along the first direction.

[0085] This reduces the battery's DC impedance, increases the battery's current flow area, and improves the battery's fast charging performance.

[0086] In any embodiment, the electrode assembly has a dimension in the first direction of 400-1000 mm.

[0087] In any embodiment, the electrode assembly has a dimension of 90-120 mm in a second direction, the second direction being perpendicular to the first direction.

[0088] In any embodiment, the electrode assembly has a dimension of 13-25 μm in a third direction, and the third direction is perpendicular to both the first direction and the second direction.

[0089] As a result, the energy density of the battery is improved while ensuring the fast charging performance of the battery.

[0090] In any embodiment, the battery cell is configured to be discharged from 4.25V to 2.0V at 1 / 3C with a platform voltage of 3.25-3.44V or 3.32-3.44V.

[0091] This increases the platform voltage of the battery and improves the energy density of the battery.

[0092] In any embodiment, the energy density of the battery cell is 210-250Wh / kg.

[0093] In any embodiment, the upper limit charging voltage of the battery cell at room temperature is 4.2-4.3V.

[0094] The second aspect of the present application further provides a battery device, comprising the battery cell of the first aspect of the present application; the battery device comprises a battery module, a battery pack or an energy storage device.

[0095] A third aspect of the present application provides an electrical device, comprising the battery cell of the first aspect of the present application or the battery device of the second aspect of the present application.

[0096] In any embodiment, the electrical device is a vehicle, and the length direction of the battery cell or the battery device is parallel to the travel direction of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figure 1 It is a schematic diagram of the structure of a positive electrode sheet or a negative electrode sheet according to one embodiment of the present application.

[0098] Figure 2 It is a schematic diagram of the structure of a positive electrode sheet or a negative electrode sheet in another embodiment of the present application.

[0099] Figure 3 It is a schematic diagram of the structure of a positive electrode sheet or a negative electrode sheet according to another embodiment of the present application.

[0100] Figure 4 It is a schematic diagram of the battery cell and pole structure of one embodiment of the present application.

[0101] Figure 5 It is a schematic diagram of an electrode assembly according to one embodiment of the present application.

[0102] Figure 6 It is an exploded view of a battery cell according to one embodiment of the present application.

[0103] Figure 7 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0104] Figure 8 yes Figure 7 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0105] Fig. 9 Schematic diagram of an electrical device using a battery pack according to an embodiment of the present application as a power source.

[0106] Description of reference numerals:

[0107] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly; 61-ear part; 62-main body; 63-positive pole; 64-negative pole. DETAILED DESCRIPTION

[0108] Below, the embodiments of the battery cells, battery modules, battery packs and electrical devices of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0109] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0110] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0111] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0112] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0113] [Battery Cell]

[0114] A battery cell, also known as a rechargeable battery or storage battery, refers to a battery that can be recharged to activate the active materials after being discharged and continue to be used.

[0115] Normally, a battery cell includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charge and discharge process of the battery, active ions (such as lithium ions) are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, and at the same time allow active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct active ions.

[0116] One embodiment of the present application provides a battery cell, including an electrode assembly, wherein the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte; the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, and the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector; wherein,

[0117] The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium iron phosphate material and a nickel cobalt manganese oxide material; in the positive electrode active material, the molar proportion of Ni element in the sum of the three elements Ni, Co, and Mn is 0.5-0.95, for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.83, 0.85, 0.9, 0.95 or a range composed of any of the above numerical values; in some embodiments, since the lithium iron phosphate material does not contain Ni element or a trace amount of Ni element, the "molar proportion of Ni element in the sum of the three elements Ni, Co, and Mn" can also be calculated based on the element content in the nickel cobalt manganese oxide material.

[0118] The non-aqueous electrolyte includes vinylene carbonate, and the mass content of the vinylene carbonate in the non-aqueous electrolyte is 0.5%-2%, such as 0.5%, 0.8%, 1%, 1.5%, 1.8%, 2% or a range consisting of any of the above values;

[0119] The non-aqueous electrolyte comprises at least one of a linear carbonate and a linear carboxylate, and the conductivity of the non-aqueous electrolyte is 9-14 mS / cm, for example, 9 mS / cm, 9.5 mS / cm, 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm or a range consisting of any of the above values.

[0120] The mixed use of nickel cobalt manganese oxide material and lithium iron phosphate material has the advantage of high energy density at low cost, thus making up for the lack of energy density range between single lithium iron phosphate battery and single nickel cobalt manganese oxide battery. However, nickel cobalt manganese oxide material with higher nickel content has the advantage of high gram capacity, which is beneficial to improve the energy density of the battery. However, the surface residual alkali content of nickel cobalt manganese oxide material with higher nickel content is high, which is easy to react with the acid in the electrolyte to produce water. Water will aggravate the acid generation in the electrolyte. The generated acid is easy to destroy the structure of the positive electrode material, resulting in the dissolution of transition metal ions. The dissolved transition metal ions are easy to enrich on the surface of the negative electrode SEI film, catalyzing the damage of the SEI film, resulting in a decrease in the cycle performance of the battery. Moreover, the power performance of lithium iron phosphate material is not as good as that of nickel cobalt manganese oxide material. Therefore, the mixing of lithium iron phosphate material into the positive electrode active material leads to a loss of power performance of the battery.

[0121] Furthermore, by making the non-aqueous electrolyte include a certain amount of vinylene carbonate, it is beneficial to form a stable component on the surface of the negative electrode to improve the stability of the negative electrode SEI film, alleviate the problem of SEI film destruction caused by the use of nickel cobalt manganese oxide materials with a high nickel content, and an appropriate amount of vinylene carbonate can also reduce the SEI film impedance and improve the power performance lost due to the use of low-power lithium iron phosphate materials; at the same time, the conductivity of the electrolyte is within a certain range, so that the transmission resistance of lithium ions in the liquid phase is reduced, which is beneficial to compensate for the power loss caused by the increase in SEI film impedance, and is also beneficial to compensate for the power loss caused by the mixing of lithium iron phosphate materials, and is also beneficial to reduce the negative impact of excessive conductivity on high-temperature cycle performance, ensuring that the battery has a high energy density while improving the battery's cycle performance and power performance.

[0122] In the present application, the molar proportion of Ni in the sum of Ni, Co and Mn can be tested by conventional methods in the art. For example, the positive electrode sheet is disassembled from the battery cell, and the positive electrode sheet is fully cleaned with DMC (dimethyl carbonate), and the positive electrode sheet is dried, and the material in the positive electrode film layer is collected, and the mass content of Ni, Co and Mn is tested by ICP, and then the molar proportion of Ni in the sum of Ni, Co and Mn is calculated.

[0123] In the present application, the conductivity of the non-aqueous electrolyte is tested by conventional methods in the art, for example, using a conductivity meter.

[0124] In some embodiments, the non-aqueous electrolyte includes a linear carbonate, the linear carbonate includes dimethyl carbonate, and the mass content of the dimethyl carbonate in the non-aqueous electrolyte is 4%-20% or 8%-16%, such as 4%, 5%, 6%, 8%, 9%, 10%, 11%, 12%, 14%, 16%, 17%, 18%, 20% or any range of the above values. Thus, adjusting the conductivity of the electrolyte by a certain amount of dimethyl carbonate is beneficial to improving the power performance of the battery while ensuring the high temperature cycle performance of the battery.

[0125] In some embodiments, the non-aqueous electrolyte includes a linear carboxylate, and the mass content of the linear carboxylate in the non-aqueous electrolyte is 5%-25%, for example, 5%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, 22%, 23%, 25% or a range consisting of any of the above values.

[0126] In some embodiments, the linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate, and ethyl acetate.

[0127] Therefore, adjusting the conductivity of the electrolyte by adding a certain amount of linear carboxylic acid ester is beneficial to improving the power performance of the battery while ensuring the high temperature cycle performance of the battery.

[0128] In some embodiments, the viscosity of the non-aqueous electrolyte at room temperature is 1-3 mPa·s or 2-3 mPa·s, for example, 1 mPa·s, 1.5 mPa·s, 1.8 mPa·s, 2 mPa·s, 2.2 mPa·s, 2.3 mPa·s, 2.5 mPa·s, 2.7 mPa·s, 2.8 mPa·s, 3 mPa·s or a range consisting of any of the above values.

[0129] In the present application, the viscosity of the non-aqueous electrolyte can be tested by conventional methods in the art. For example, a rotational viscometer is used for testing. When a rotor (e.g., rotor No. 18) is continuously rotated at a certain speed (e.g., 70 rpm) in a sample at room temperature (e.g., 20°C-35°C), the shear force applied causes the spring to generate torque, which is proportional to the viscosity, thereby obtaining the viscosity value of the sample. For example, under the condition of ambient humidity <80%, a sample is kept at a constant temperature of 25°C for at least 30 minutes, rotor No. 18 is placed in a sample cup, a speed of 70 rpm is selected, and the reading is taken for 5 minutes to obtain the viscosity value. More than 10 data points can be collected during the test and the average value is taken. The testing instrument can specifically be a Bolefei DV-2TLV viscometer.

[0130] In some embodiments, when the mass proportion of the lithium nickel cobalt manganese oxide material in the positive electrode active material is ≥10%, the non-aqueous electrolyte further includes a substance containing a sulfur-oxygen bond, and the substance containing a sulfur-oxygen bond includes at least one of vinyl sulfate and 1,3-propane sultone.

[0131] In some embodiments, the mass content of the substance containing sulfur-oxygen bonds in the non-aqueous electrolyte is 0.5%-4% or 0.5%-2%, for example, 0.5%, 1%, 1.5%, 2%, 2.2%, 2.3%, 2.5%, 2.7%, 2.8%, 3%, 3.5%, 4% or a range consisting of any of the above values.

[0132] Therefore, when the mass proportion of nickel cobalt manganese oxide material in the positive electrode active material is ≥10%, in order to facilitate the capacity advantage of nickel cobalt manganese oxide material, the upper limit voltage of the battery is based on the nickel cobalt manganese oxide material. Under high pressure, substances containing sulfur-oxygen bonds form a film at the positive electrode, which optimizes the positive electrode interface film component, inhibits the side reaction between the residual alkali on the surface of the nickel cobalt manganese oxide material and the acidic substances in the electrolyte, and improves the battery cycle performance.

[0133] In some embodiments, in the non-aqueous electrolyte, a mass ratio of the 1,3-propane sultone to the vinyl sulfate is greater than 0 and less than 1.

[0134] Therefore, the mass of vinyl sulfate is greater than that of 1,3-propane sultone, which can reduce the impedance of the positive electrode interface film and improve the power performance of the battery.

[0135] In the present application, the mass content of vinyl sulfate and 1,3-propane sultone in the non-aqueous electrolyte is tested by conventional methods in the art, such as gas chromatography.

[0136] In some embodiments, the non-aqueous electrolyte further includes a lithium salt, and the mass content of the lithium salt in the non-aqueous electrolyte is 12%-16%, for example, 12%, 13%, 14%, 15%, 16% or a range consisting of any of the above values.

[0137] In some embodiments, when the mass proportion of the lithium nickel cobalt manganese oxide material in the positive electrode active material is ≥20%, the lithium salt includes lithium hexafluorophosphate and a fluorosulfonamide lithium salt, and the fluorosulfonamide lithium salt includes at least one of monofluorosulfonyl imide lithium, bisfluorosulfonyl imide lithium, and trifluorosulfonyl imide lithium.

[0138] Therefore, including lithium hexafluorophosphate and fluorosulfonamide lithium salts in the non-aqueous electrolyte can increase the heat resistance temperature of the electrolyte, thereby reducing the risk of thermal runaway of the positive electrode caused by the heat instability of the electrolyte.

[0139] In some embodiments, the lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonyl imide, and the mass ratio of the lithium hexafluorophosphate to the lithium bisfluorosulfonyl imide is 1.23:1-4.28:1, for example, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.7:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.1:1, 4.2:1, 4.28:1 or a range consisting of any of the above numerical values.

[0140] Therefore, the ratio of lithium hexafluorophosphate to lithium bis(fluorosulfonyl)imide within the above range can, on the one hand, reduce the risk of thermal runaway of the positive electrode caused by the heat instability of the electrolyte, and on the other hand, reduce the negative impact of lithium bis(fluorosulfonyl)imide on the safety performance of the negative electrode, thereby improving the safety performance of the battery.

[0141] In some embodiments, the non-aqueous electrolyte further includes ethylene carbonate, and the mass content of ethylene carbonate in the non-aqueous electrolyte is 12%-35%, for example, 12%, 15%, 18%, 20%, 22%, 25%, 27%, 30%, 32%, 33%, 34%, 35% or a range consisting of any of the above values.

[0142] Therefore, on the one hand, including ethylene carbonate in the non-aqueous electrolyte is beneficial to reducing the impedance of the interface film, thereby improving the power performance of the battery while ensuring the battery cycle performance; on the other hand, the above content can inhibit the side reaction of ethylene carbonate with the positive electrode active material, thereby improving the cycle performance and safety performance of the battery.

[0143] In the present application, the mass content of ethylene carbonate in the non-aqueous electrolyte is tested by conventional methods in the art, such as gas chromatography.

[0144] In some embodiments, the mass content of Ni element in the positive electrode film layer is 4.5%-25% (for example, 4.5%, 5%, 7%, 9%, 10%, 12%, 14%, 15%, 17%, 19%, 20%, 22%, 24%, 25% or any range consisting of the above values), the mass content of Fe element in the positive electrode film layer is 15%-33% (for example, 15%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 31%, 32%, 33% or any range consisting of the above values), and the mass content of vinyl carbonate in the non-aqueous electrolyte is 1%-1.5% (for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or any range consisting of the above values).

[0145] In the embodiments of the present application, the type and content of the organic components in the electrolyte are well known in the art and can be detected by using equipment and methods well known in the art, for example, the composition of the electrolyte can be measured by liquid chromatography, gas chromatography, ion chromatography, liquid phase nuclear magnetic resonance, etc. Exemplarily, the organic components in the electrolyte can be qualitatively and quantitatively analyzed by gas chromatography with reference to GB / T9722-2006 "General Rules for Gas Chromatography of Chemical Reagents".

[0146] The test sample in the embodiments of the present application can be a newly prepared electrolyte as a sample, or a free electrolyte obtained from a battery after the battery is fully discharged (discharged to the lower limit cut-off voltage so that the battery's charged state is about 0% SOC) as a sample.

[0147] In the present application, the mass content of linear carbonate, vinylene carbonate, vinyl sulfate, 1,3-propane sultone, vinyl carbonate, and linear carboxylic acid ester in the non-aqueous electrolyte can be tested by conventional methods in the art. For example, gas chromatography is used for testing. The specific operating conditions of gas chromatography may include: the main components of the gas chromatography column include fused silica, stationary phase (phenyl methyl polysiloxane, polyethylene glycol, alumina or molecular sieve), and protective layer (polyimide coating); the injection port temperature is 300°C; the column temperature is 250°C; the detector is 300°C; and the carrier flow rate is 1.5mL / min.

[0148] In the embodiments of the present application, the types and contents of the inorganic components / lithium salt concentrations in the electrolyte are well-known in the art, and can be detected by equipment and methods well-known in the art. For example, the inorganic components / lithium salt concentrations in the electrolyte can be qualitatively or quantitatively analyzed by ion chromatography analysis methods with reference to the standard JY / T020-1996 "General Rules for Ion Chromatography Analysis Methods". In the embodiments of the present application, a newly prepared electrolyte can be taken as a sample, or the battery can be fully discharged (discharged to the lower limit cut-off voltage so that the battery is charged at about 0% SOC), and the free electrolyte obtained from the battery can be used as a sample, and the ion chromatography analysis method can be used for detection.

[0149] In some embodiments, the mass percentage of the lithium iron phosphate material in the positive electrode active material is 50%-90%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or a range consisting of any of the above values.

[0150] Therefore, when the mass proportion of lithium iron phosphate material in the positive electrode active material is high, the structural stability is increased, which can improve the cycle performance and safety performance.

[0151] In this application, the mass proportion of Fe and Ni in the positive electrode film layer is tested by conventional methods in the art. For example, the battery cell is disassembled, the positive electrode sheet is taken out, the positive electrode sheet is fully cleaned with DMC (dimethyl carbonate), and the positive electrode sheet is dried, the material in the positive electrode film layer is collected, and the mass proportion of each element in the positive electrode film layer is tested by ICP.

[0152] In some embodiments, the mass proportion of the lithium iron phosphate material in the positive electrode active material is 60%-80% (for example, 60%, 65%, 70%, 75%, 80% or a range consisting of any of the above numerical values); in the positive electrode active material, the molar proportion of Ni element in the sum of the three elements Ni, Co, and Mn is 0.7-0.95, for example, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or a range consisting of any of the above numerical values.

[0153] As a result, the battery has both good energy density and cycle performance while maintaining cost advantages.

[0154] In some embodiments, the lithium iron phosphate material also includes one or more elements of Al, B, Ca, Cr, K, Mg, Ni, Co, Mn, Na, Si, Ti, V, Cu, Zn, S, Sc, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Cl, C, N, and F.

[0155] In some embodiments, the lithium iron phosphate material includes one or more of the following:

[0156] The mass percentage of Al element in the lithium iron phosphate material is 0.01%-0.02%;

[0157] The mass percentage of element B in the lithium iron phosphate material is 0.08%-0.09%;

[0158] The mass percentage of Ca element in the lithium iron phosphate material is 0.0001%-0.0003%;

[0159] The mass proportion of Fe element in the lithium iron phosphate material is 16.035%-35%;

[0160] The mass proportion of K element in the lithium iron phosphate material is 0.0022%-0.0050%;

[0161] The mass proportion of Li element in the lithium iron phosphate material is 3%-4.5%;

[0162] The mass percentage of Mg element in the lithium iron phosphate material is 0.00235%-0.0052%;

[0163] The mass percentage of Mn element in the lithium iron phosphate material is 0.00205%-0.0050%;

[0164] The mass percentage of the Na element in the lithium iron phosphate material is 0.018%-0.05%;

[0165] The mass proportion of P element in the lithium iron phosphate material is 9.265%-19.5%;

[0166] The mass percentage of Si element in the lithium iron phosphate material is 0.0065%-0.02%;

[0167] The mass percentage of Ti element in the lithium iron phosphate material is 0.074%-0.16%;

[0168] The mass proportion of V element in the lithium iron phosphate material is 0.0003%-0.0008%;

[0169] The mass percentage of Cr element in the lithium iron phosphate material is 0.0004%-0.0012%;

[0170] The mass proportion of Zn element in the lithium iron phosphate material is 0.00005%-0.0003%.

[0171] In some embodiments, the lithium nickel cobalt manganese oxide material also includes one or more elements of Al, B, Fe, Sr, Ti, Y, Zr, Na, K, Mg, Si, P, S, Ca, Sc, V, Cr, Cu, Zn, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F.

[0172] In some embodiments, the lithium nickel cobalt manganese oxide material includes one or more of the following:

[0173] The mass percentage of Al element in the nickel cobalt lithium manganese oxide material is 0.0315%-0.07%;

[0174] The mass percentage of element B in the nickel cobalt manganese oxide material is 0.00195%-0.005%;

[0175] The mass percentage of Co element in the lithium nickel cobalt manganese oxide material is 3.825%-8%;

[0176] The mass percentage of Fe element in the nickel cobalt manganese oxide material is 0.0016%-0.005%;

[0177] The mass proportion of Li element in the nickel cobalt manganese oxide material is 5.5%-6.8%;

[0178] The mass percentage of Mn element in the lithium nickel cobalt manganese oxide material is 1.22%-2.8%;

[0179] The mass proportion of Ni element in the lithium nickel cobalt manganese oxide material is 24.93%-51%;

[0180] The mass percentage of Sr element in the nickel cobalt manganese oxide material is 0.00005%-0.0002%;

[0181] The mass percentage of Ti element in the nickel cobalt lithium manganese oxide material is 0.00015%-0.0004%;

[0182] The mass proportion of Y element in the nickel cobalt manganese oxide material is 0.0004%-0.0009%;

[0183] The mass proportion of Zr element in the lithium nickel cobalt manganese oxide material is 0.128%-0.3%.

[0184] In some embodiments, the nickel cobalt manganese oxide material includes spherical particles, and the lithium iron phosphate material includes particles having a shape suitable for filling the gaps between the spherical particles. Thus, the compaction density of the positive electrode active material is increased, thereby improving the energy density of the battery. In addition, the spherical lithium cobalt manganese oxide material is mostly a secondary particle morphology, which has good power performance.

[0185] In some embodiments, the nickel cobalt manganese oxide material is a polycrystalline material. Therefore, the use of polycrystalline nickel cobalt manganese oxide material is beneficial to improving the power of the battery.

[0186] In some embodiments, the nickel cobalt manganese oxide material includes particles with a longest diameter of 4-8 μm and particles with a longest diameter of 0.5-2 μm. Thus, the combination of nickel cobalt manganese oxide particles of different particle sizes is beneficial to increase the compaction density of the positive electrode active material and improve the energy density of the battery.

[0187] In some embodiments, the lithium iron phosphate material includes particles with a longest diameter of 0.1-0.3 μm and particles with a longest diameter of 1-2 μm. Thus, the combination of lithium iron phosphate particles of different particle sizes is beneficial to increase the compaction density of the positive electrode active material and improve the energy density of the battery.

[0188] In some embodiments, the "longest diameter" refers to: cutting a positive electrode sheet including lithium phosphate particles along the thickness direction of the sheet to expose the longitudinal section of the positive electrode film layer; and determining the longest diameter of the lithium phosphate particles by performing a scanning electron microscope (SEM) test on the longitudinal section of the positive electrode film layer. Specifically, the maximum value of the distance between any two points on the peripheral edge line of the particle is the "longest diameter" of the particle.

[0189] In the present application, the longest diameter of the particles of lithium iron phosphate material (or nickel cobalt manganese oxide material) can be tested by conventional methods in the art. For example, the positive electrode sheet is disassembled from the battery cell, the positive electrode sheet is fully cleaned with DMC (dimethyl carbonate), and the positive electrode sheet is dried, and the positive electrode sheet is cut along the thickness direction to expose the longitudinal section of the positive electrode film layer. Since the particle morphology of lithium iron phosphate material and nickel cobalt manganese oxide material is different, they can be distinguished. For lithium iron phosphate particles (or nickel cobalt manganese oxide particles), SEM is used to measure multiple times from different directions of each particle, and the maximum measured value is taken as the longest diameter. Multiple (for example, 10-100) particles of each material are tested.

[0190] In some embodiments, the positive electrode film layer further includes a lithium supplement material, and the lithium supplement material includes one or more of lithium phosphate, lithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, and trilithium citrate. This is beneficial to improving the energy density of the battery.

[0191] In some embodiments, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite and silicon material, and the mass proportion of silicon in the negative electrode film layer is 0.3%-10%, such as 0.3%, 0.5%, 0.8%, 1%, 3%, 4%, 5%, 7%, 8%, 9%, 10% or any range of the above values. This is conducive to improving the energy density of the battery.

[0192] In this application, the mass percentage of silicon in the negative electrode film layer is tested by conventional methods in the art. For example, the battery cell is disassembled, the negative electrode plate is taken out, the negative electrode plate is fully cleaned with DMC (dimethyl carbonate), and the negative electrode plate is dried, the material in the negative electrode film layer is collected, and the mass percentage of silicon in the negative electrode film layer is tested by ICP.

[0193] In some embodiments, the silicon material includes one or more of silicon oxide and silicon-carbon composite.

[0194] In some embodiments, the silicon material includes a silicon-carbon composite, and the mass proportion of silicon in the negative electrode film layer is 1%-5%, which is beneficial to improve the energy density of the battery.

[0195] In some embodiments, the surface density of the positive electrode film layer is 0.32-0.36 mg / 1540.25 mm 2 , for example 0.32mg / 1540.25mm 2 , 0.34mg / 1540.25mm 2 , 0.35mg / 1540.25mm 2 , 0.36mg / 1540.25mm 2Or any range consisting of the above values.

[0196] In some embodiments, the surface density of the negative electrode film layer is 0.169-0.190 mg / 1540.25 mm 2 , for example 0.169mg / 1540.25mm 2 、0.170mg / 1540.25mm 2 、0.174mg / 1540.25mm 2 、0.176mg / 1540.25mm 2 、0.178mg / 1540.25mm 2 、0.180mg / 1540.25mm 2 , 0.182mg / 1540.25mm 2 、0.185mg / 1540.25mm 2 、0.187mg / 1540.25mm 2 、0.190mg / 1540.25mm 2 Or any range consisting of the above values.

[0197] This helps to increase the energy density of the battery.

[0198] In this application, the surface density of the positive electrode film layer (negative electrode film layer) is tested by conventional methods in the field. For example, a fixed area of ​​positive electrode sheet (negative electrode sheet) is cut and weighed, the weight of the positive electrode collector (negative electrode collector) of the same area is weighed and calculated in advance, and the average thickness of the positive electrode film layer (negative electrode film layer) on the positive electrode sheet (negative electrode sheet) is measured. The weight of the positive electrode collector (negative electrode collector) is subtracted from the weight of the positive electrode sheet (negative electrode sheet), and then divided by the fixed area to obtain the surface density of the positive electrode film layer (negative electrode film layer).

[0199] In some embodiments, the ratio of the size of the positive electrode film layer in the first direction to the size of the battery cell in the first direction is ≥92%.

[0200] In some embodiments, the ratio of the size of the positive electrode film layer in the second direction to the size of the battery cell in the second direction is ≥93%, and the second direction is perpendicular to the first direction.

[0201] This is beneficial to improving the utilization rate of the electrode assembly.

[0202] In some embodiments, when the battery cell is configured to a 0% SOC state, that is, the state achieved by discharging at 0.33C to 2.0V and then discharging at 0.05C to 2.0V at 25°C; the thickness ratio of the positive electrode film layer on either side of the positive electrode collector to the positive electrode collector is 5-8.

[0203] In some embodiments, when the battery cell is configured to a 0% SOC state, that is, a state achieved by discharging at 0.33C to 2.0V and then at 0.05C to 2.0V at 25°C; the thickness ratio of the negative electrode film layer on either side of the negative electrode current collector to the negative electrode current collector is 13-20.

[0204] As a result, the energy density and dynamic performance of the battery are improved at the same time.

[0205] In some embodiments, the negative electrode film layer includes a first negative electrode film layer located on the negative electrode current collector and a second negative electrode film layer located on the first negative electrode film layer, and the first negative electrode film layer and the second negative electrode film layer include graphite, thereby further improving the dynamic performance of the battery.

[0206] In some embodiments, the thickness of the positive electrode current collector is 10-13 μm.

[0207] In some embodiments, the thickness of the negative electrode current collector is 4-5.5 μm.

[0208] This improves the energy density of the battery.

[0209] In some embodiments, the electrode assembly includes at least two positive electrode sheets and at least two negative electrode sheets, and the positive electrode sheets and the negative electrode sheets are stacked; Figure 1 As shown (a single pole piece is shown in the figure), the positive pole piece and / or the negative pole piece includes a pole ear portion 61 and a main body portion 62, the pole ear portion 61 extends from the main body portion 62 along a first direction, and the ratio of the total dimension L1 of the connecting area between the pole ear portion 61 and the main body portion 62 in the second direction to the dimension L of the main body portion 62 in the second direction is ≥50%, and the second direction is perpendicular to the first direction.

[0210] In some embodiments, Figure 2 As shown (a single pole piece is shown in the figure), the positive pole piece and / or the negative pole piece includes a main body 62 and a plurality of pole ear portions 61, and the plurality of pole ear portions 61 extend from the main body 62 along a first direction, and the dimensions of the connecting areas of the plurality of pole ear portions 61 and the main body 62 in the second direction are L1a and L1b, respectively, and the total dimension L1 is obtained by adding L1a and L1b, and the ratio of L1 to the dimension L of the main body 62 in the second direction is ≥50%, and the second direction is perpendicular to the first direction.

[0211] In some embodiments, Figure 3As shown (a single pole piece is shown in the figure), the positive pole piece and / or the negative pole piece includes a main body 62 and a pole ear portion 61, the pole ear portion 61 extends from the main body 62 along a first direction, the pole ear portion 61 is trapezoidal, and the ratio of the total dimension L1 of the connecting area of ​​the pole ear portion 61 and the main body 62 in the second direction to the dimension L of the main body 62 in the second direction is ≥50%, and the second direction is perpendicular to the first direction.

[0212] In some embodiments, the battery cell includes at least two poles of the same polarity, and the poles are directly electrically connected to pole lugs of corresponding polarity.

[0213] In some embodiments, Figure 4 As shown, the battery cell 5 includes two positive poles 63 and two negative poles 64, the two positive poles 63 are respectively arranged on the two side surfaces of the battery cell 5 perpendicular to the first direction, the two negative poles 64 are respectively arranged on the two side surfaces of the battery cell 5 perpendicular to the first direction, and the positive poles 63 and the negative poles 64 are respectively arranged opposite to each other along the first direction.

[0214] This reduces the battery's DC impedance, increases the battery's current flow area, and improves the battery's fast charging performance.

[0215] In some embodiments, the electrode assembly has a dimension in the first direction of 400-1000 mm.

[0216] In some embodiments, a dimension of the electrode assembly in a second direction is 90-120 mm, and the second direction is perpendicular to the first direction.

[0217] In some embodiments, the electrode assembly has a dimension of 13-25 μm in a third direction, and the third direction is perpendicular to both the first direction and the second direction.

[0218] As a result, the energy density of the battery is improved while ensuring the fast charging performance of the battery.

[0219] In some embodiments, the battery cell is configured to be discharged from 4.25V to 2.0V at a 1 / 3C discharge rate to a plateau voltage of 3.25-3.44V or 3.32-3.44V.

[0220] This increases the platform voltage of the battery and improves the energy density of the battery.

[0221] When the mass proportion of lithium iron phosphate in the positive electrode film layer is 50%-90%, the platform voltage of the battery cell discharged from 4.25V to 2.0V at 1 / 3C can be 3.25-3.44V. When the mass proportion of lithium iron phosphate in the positive electrode film layer is 60%-80%, the platform voltage of the battery cell discharged from 4.25V to 2.0V at 1 / 3C can be 3.32-3.44V.

[0222] In the present application, the platform voltage is tested by charging the battery cell to 4.25V at a certain current (eg 1 / 3C), then discharging from 4.25V to 2.0V at 1 / 3C, and obtaining the platform voltage value according to the discharge curve.

[0223] In some embodiments, the energy density of the battery cell is 210-250Wh / kg.

[0224] In the present application, the energy density test of the battery cell is as follows: the battery cell is charged at a constant current to a charging cut-off voltage, then charged at a constant voltage to ≤0.05C, and then discharged at a constant current to a discharge cut-off voltage, and the discharge capacity A0 and the platform voltage V are recorded; the mass of the battery cell is weighed (generally the battery cell with a casing is weighed) M0; the energy density of the battery cell is A0×V) / M0, and the unit can be Wh / kg.

[0225] In some embodiments, the upper charging voltage limit of the battery cell at room temperature is 4.2-4.3 V, thereby increasing the energy density of the battery.

[0226] [Positive electrode]

[0227] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after charge and discharge cycles.

[0228] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0229] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0230] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0231] In some embodiments, the positive electrode active material may also be a positive electrode active material for a battery known in the art. These positive electrode active materials may be used alone or in combination of two or more. Examples include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, lithium manganese phosphate (such as LiMnPO4), and a composite material of lithium manganese phosphate and carbon.

[0232] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0233] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0234] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0235] [Negative electrode]

[0236] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0237] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0238] In some embodiments, the negative electrode active material may also adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0239] In some embodiments, the negative electrode film layer may further include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0240] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0241] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0242] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0243] [Electrolytes]

[0244] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0245] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0246] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0247] In some embodiments, the solvent can be selected from at least one of vinylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluorovinylidene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0248] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0249] [Isolation film]

[0250] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0251] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0252] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0253] In some embodiments, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0254] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0255] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 5 The electrode assembly 52 is an example of a battery cell having a square structure.

[0256] In some embodiments, reference Figure 6 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0257] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0258] In the battery module, the plurality of battery cells may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells may be fixed by fasteners.

[0259] Optionally, the battery module may further include a housing having a receiving space, and a plurality of battery cells are received in the receiving space.

[0260] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0261] Figure 7 and Figure 8 1 is a battery pack 1 as an example. Figure 7 and Figure 8The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0262] In addition, the present application also provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as power sources for electrical devices, or as energy storage units for electrical devices. Electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0263] As an electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0264] Fig. 9 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of battery cells, a battery pack or a battery module can be used.

[0265] Example 1

[0266] (1) Positive electrode sheet: The positive electrode film layer includes positive electrode active materials lithium iron phosphate (LFP) and lithium nickel cobalt manganese oxide (NCM), binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black. The mass ratio of the three is 97:2:1. The thickness of the positive electrode current collector aluminum foil is 13μm. The positive electrode film layer is located on both sides of the aluminum foil. The surface density of the positive electrode film layer is 0.34g / 1540.25mm 2 In the battery cell 0% SOC state, the thickness ratio of the positive electrode film layer on the positive electrode current collector side to the positive electrode current collector is 5.73.

[0267] (2) Negative electrode sheet: The negative electrode film layer includes natural graphite, a conductive agent, acetylene black, a binder, styrene butadiene rubber, and a thickener, sodium carboxymethyl cellulose, in a mass ratio of 96:1:2:1. The negative electrode current collector is a copper foil with a thickness of 4.5 μm, and the negative electrode film layer is located on both sides of the copper foil. The surface density of the negative electrode film layer is 0.18 g / 1540.25 mm 2 In the battery cell 0% SOC state, the thickness ratio of the negative electrode film layer on the negative electrode current collector side to the negative electrode current collector is 16.3.

[0268] (3) Separation film: A polyethylene (PE) film with a thickness of 5 μm was used as the separation film.

[0269] (4) The electrolyte includes vinylene carbonate (VC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and LiPF6, wherein the mass content of LiPF6 in the electrolyte is 12.5%, the mass content of vinylene carbonate is 1.5%, the mass content of dimethyl carbonate is 16%, the mass content of ethyl methyl carbonate is 28%, and the rest is diethyl carbonate. The conductivity of the electrolyte at 25° C. is 9.5 mS / cm.

[0270] (5) Battery cell: including stacked positive electrode sheets, separators, and negative electrode sheets to obtain an electrode assembly, the size of the electrode assembly in the first direction is 574 mm, the size in the second direction is 120 mm, and the size in the third direction is 17.9 mm. The electrode assembly is added to the outer square aluminum shell, and the electrolyte is injected after drying. After packaging, high-temperature standing, formation, secondary injection, aging, capacity and other processes, a battery cell is obtained. The ratio of the size of the positive electrode film layer in the first direction to the size of the battery cell in the first direction is 93.9%, and the ratio of the size of the positive electrode film layer in the second direction to the size of the battery cell in the second direction is 93.3%.

[0271] The battery cell also includes a pole ear portion extending from both sides of the positive pole piece and the negative pole piece along the first direction, and the ratio of the total size L1 of the connecting area between the pole ear portion and the pole piece in the second direction to the size L of the pole piece in the second direction is 70%. Figure 1 set up.

[0272] like Figure 4 As shown, the battery cell further includes two positive poles and two negative poles, the two positive poles are respectively arranged on two sides of the battery cell perpendicular to the first direction, the two negative poles are respectively arranged on two sides of the battery cell perpendicular to the first direction, and the positive poles and the negative poles are arranged opposite to each other along the first direction. The poles are directly electrically connected to the pole ears of the corresponding polarity.

[0273] The upper limit voltage of battery cell charging at room temperature is 4.2-4.3V.

[0274] The differences in parameters between Examples 2-17, Comparative Examples 1-6 and Example 1 are shown in Table 1.

[0275] Example 4

[0276] The electrolyte includes vinylene carbonate (VC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), LiPF6 and LiFSI. The mass content of LiPF6 in the electrolyte is 8.46%, the mass content of LiFSI is 4.7%, the mass content of vinylene carbonate is 1.5%, the mass content of dimethyl carbonate is 16%, the mass content of ethyl methyl carbonate is 28%, and the rest is diethyl carbonate. The conductivity of the electrolyte at 25°C is 10mS / cm. The remaining operations and parameters are the same as those in Example 1.

[0277] Example 5

[0278] The electrolyte includes vinylene carbonate (VC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), vinyl sulfate, 1,3-propane sultone, LiPF6 and LiFSI. The mass content of LiPF6 in the electrolyte is 8.46%, the mass content of LiFSI is 4.7%, the mass content of vinylene carbonate is 1.5%, the mass content of dimethyl carbonate is 16%, the mass content of vinyl sulfate is 1.2%, the mass content of 1,3-propane sultone is 1%, the mass content of ethyl methyl carbonate is 28%, and the rest is diethyl carbonate. The conductivity of the electrolyte at 25°C is 10mS / cm. The remaining operations and parameters are the same as those in Example 1.

[0279] Example 6

[0280] The electrolyte includes vinylene carbonate (VC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), diethyl carbonate (DEC), vinyl sulfate, 1,3-propane sultone, LiPF6 and LiFSI. The mass content of LiPF6 in the electrolyte is 8.46%, the mass content of LiFSI is 4.7%, the mass content of vinylene carbonate is 1.5%, the mass content of dimethyl carbonate is 16%, the mass content of ethylene carbonate is 28%, the mass content of vinyl sulfate is 1.2%, the mass content of 1,3-propane sultone is 1%, the mass content of ethyl methyl carbonate is 28%, and the rest is diethyl carbonate. The conductivity of the electrolyte at 25°C is 11mS / cm. The remaining operations and parameters are the same as those in Example 1.

[0281] The electrolytes of Examples 3, 14 and 15 contain 16% by mass of ethyl acetate, while the other Examples and Comparative Examples do not contain ethyl acetate.

[0282] In Examples 1, 4-6, 10-15, and Comparative Examples 2-5, the mass proportion of Ni in the positive electrode film layer is 19.8%. In Examples 2-3, 7-9, 16-17, Comparative Examples 1, and Comparative Example 6, the mass proportion of Ni in the positive electrode film layer is 12.02%, 23%, 12.02%, 15.6%, 23%, 14.82%, 9.88%, 7.98%, and 0%, respectively.

[0283] In Examples 1-15 and Comparative Examples 1-5, the mass proportion of Fe in the positive electrode film layer is 21.2%. In Examples 16-17 and Comparative Example 6, the mass proportion of Fe in the positive electrode film layer is 24.75%, 28.28%, and 35.36%, respectively.

[0284] In Examples 1, 4-6, 10-15 and Comparative Examples 2-5, the platform voltage is 3.396 V. In Examples 2-3, 7-9, 16-17 and Comparative Examples 1 and 6, the platform voltages are 3.39 V, 3.401 V, 3.39 V, 3.393 V, 3.401 V, 3.349 V, 3.306 V, 3.388 V, and 3.2 V, respectively.

[0285] Embodiment 18

[0286] Except for the following settings, the rest are the same as Example 6.

[0287] The positive electrode film layer also includes lithium supplement material lithium ferrite, which accounts for 0.5% by mass in the positive electrode film layer.

[0288] The negative electrode film layer comprises a first negative electrode film layer located on the negative electrode current collector and a second negative electrode film layer located on the first negative electrode film layer, and the first negative electrode film layer and the second negative electrode film layer comprise natural graphite.

[0289] The nickel cobalt manganese oxide material is a polycrystalline material, and the nickel cobalt manganese oxide material includes spherical particles with a maximum diameter of 4-8μm and spherical particles with a maximum diameter of 0.5-2μm. Based on the mass of the nickel cobalt manganese oxide material, the nickel cobalt manganese oxide material includes the following elements in mass proportion: Al element 0.063%, B element 0.004%, Co element 7.65%, Fe element 0.004%, Li element 6.14%, Mn element 2.44%, Ni element 49.86%, Sr element 0.0001%, Ti element 0.0003%, Y element 0.0008%, Zr element 0.256%.

[0290] The lithium iron phosphate material includes particles with a maximum diameter of 0.1-0.3 μm and particles with a maximum diameter of 1-2 μm, and the lithium iron phosphate includes particles with a shape suitable for filling the gaps between spherical particles. Based on the mass of the lithium iron phosphate material, the lithium iron phosphate material includes the following elements in mass proportion: Al element 0.018%, Ca element 0.0002%, Cr element 0.0009%, Fe element 32.07%, K element 0.0044%, Li element 3.92%, Mg element 0.0047%, Mn element 0.0041%, Na element 0.036%, P element 18.53%, Si element 0.013%, Ti element 0.148%, V element 0.0006%, Zn element 0.0001%.

[0291] The tested battery power density is 5.44W / Wh.

[0292] Embodiment 19

[0293] The negative electrode active material is natural graphite and silicon-carbon composite (mass ratio of silicon to carbon is 1:1, manufacturer is G14), and the mass proportion of silicon in the negative electrode active material is 2.5%. The other parameters are the same as those in Example 6.

[0294] The tested battery energy density is 230Wh / kg.

[0295] Battery Test:

[0296] (1) Battery cell energy density test: At 25°C, charge the battery cell at a constant current of 0.33C to a cut-off voltage of 4.25V, then charge it at a constant voltage of ≤0.05C, and then discharge it at a constant current of 0.33C to a cut-off voltage of 2.0V, and record the discharge energy E0 and discharge capacity C0; weigh the mass of the battery cell (usually weigh the battery cell with the casing) M0; the energy density of the battery cell is E0 / M0, and the unit can be Wh / kg.

[0297] (2) Cycle performance test of battery cells:

[0298] At 45°C, charge at 0.5C constant current to 4.25V, then charge at constant voltage to 0.05C, let stand for 10 minutes, and then discharge at 1C constant current to 2.0V. This is one charge and discharge cycle, and record the first discharge capacity. Let stand for 10 minutes, repeat the above charge and discharge cycle until the battery discharge capacity decays to 80% of the first discharge capacity, stop testing, and record the number of cycles.

[0299] (3) Power density test of battery cells:

[0300] At 25°C, charge the battery cell at a constant current of 0.33C to a cut-off voltage of 4.25V, then charge at a constant voltage of 0.05C and place for 10 minutes; discharge at a constant current of 0.33C0 for 90 minutes to adjust the battery to 50% SOC, record the voltage U1 at this time, then discharge at a pulse of 3C0 for 30 seconds, and record the voltage after discharge as U2. The corresponding DC resistance R = (U1-U2) / 3C0, power W = discharge cut-off voltage*(U1-discharge cut-off voltage) / R, power density P = W / E0. Among them, C0 and E0 are measured according to the method in item (1).

[0301] In the following table, the chemical formula of the lithium iron phosphate material also includes the M1 element in addition to Li and Fe. The mass content of the M1 element in the lithium iron phosphate material is trace, so it is not expressed in its chemical formula, but it is still considered that the M1 element is included in the lithium iron phosphate material shown in the table. The sum of the subscript of Fe in the chemical formula of the lithium iron phosphate material and the total number of moles of the M1 element in the chemical formula is 1. The chemical formula of the lithium nickel cobalt manganese oxide material also includes the M2 element in addition to Li, Ni, Co, and Mn. The mass content of the M2 element in the lithium nickel cobalt manganese oxide material is trace, so it is not expressed in its chemical formula, but it is still considered that the M2 element is included in the lithium nickel cobalt manganese oxide material shown in the table. The sum of the subscripts of Ni, Co, and Mn in the chemical formula of the lithium nickel cobalt manganese oxide material and the total number of moles of the M2 element in the chemical formula is 1. The M1 element and the M2 element may be the same or different.

[0302]

[0303]

[0304]

[0305]

[0306] Table 4

[0307]

[0308] As can be seen from the above table, compared with Example 1, the molar ratio of Ni in the sum of Ni, Co, and Mn in Example 2 is reduced, which can improve the cycle performance of the battery monomer. Compared with Example 1, the molar ratio of Ni in the sum of Ni, Co, and Mn in Example 3 is increased, which can improve the energy density and power performance of the battery monomer, and the additive VC content is increased, and the cycle performance is improved.

[0309] Table 5

[0310]

[0311] It can be seen from the above table:

[0312] Compared with Example 1, the lithium salt of the electrolyte of Example 4 is added with lithium bis(fluorosulfonyl)imide, which is beneficial to improve the cycle performance and power performance of the battery monomer. On the basis of Example 4, the electrolyte of Example 5 is added with vinyl sulfate and 1,3-propane sultone, which is beneficial to further improve the cycle performance of the battery monomer. On the basis of Example 5, the electrolyte of Example 6 is added with vinyl carbonate, which is beneficial to further improve the cycle performance and power performance of the battery monomer.

[0313] Table 6

[0314]

[0315] It can be seen from the above table:

[0316] Compared with Example 6, the molar ratio of Ni in the total of Ni, Co, and Mn in Examples 7-8 is reduced, and the cycle performance of the battery cell is improved accordingly.

[0317] Compared with Example 6, the molar ratio of Ni in the total of Ni, Co, and Mn in Example 9 is increased, and the energy density and power performance of the battery cell are improved accordingly.

[0318] Table 7

[0319]

[0320] As can be seen from the table above: compared with Example 6, the mass content of vinyl carbonate in the electrolyte of Examples 10-11 is reduced, and the power performance of the battery monomer is improved accordingly. Compared with Example 6, the mass content of vinyl carbonate in the electrolyte of Example 12 is increased, and the cycle performance of the battery monomer is improved accordingly.

[0321] Table 8

[0322]

[0323] It can be seen from the above table that: compared with Example 6, the electrolyte conductivity of Examples 14-15 is improved, which can improve the power performance of the battery cell.

[0324] Table 9

[0325]

[0326] It can be seen from the above table that: compared with Example 6, Examples 16-17 increase the mass proportion of lithium iron phosphate in the positive electrode active material, which can improve the cycle performance of the battery cell.

[0327] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, comprising an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, and the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector; wherein: The positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes a lithium iron phosphate material and a nickel cobalt manganese oxide lithium material; in the positive electrode active material, the molar ratio of Ni element in the sum of the three elements of Ni, Co and Mn is 0.5-0.95; The non-aqueous electrolyte includes vinylene carbonate, and the mass content of the vinylene carbonate in the non-aqueous electrolyte is 0.5%-2%; The non-aqueous electrolyte includes at least one of a linear carbonate and a linear carboxylate, and the conductivity of the non-aqueous electrolyte is 9-14 mS / cm.

2. The battery cell according to claim 1, wherein: The non-aqueous electrolyte includes linear carbonate, the linear carbonate includes dimethyl carbonate, and the mass content of the dimethyl carbonate in the non-aqueous electrolyte is 4%-20% or 8%-16%.

3. The battery cell according to claim 1 or 2, wherein: The non-aqueous electrolyte includes a linear carboxylate, and the mass content of the linear carboxylate in the non-aqueous electrolyte is 5%-25%.

4. The battery cell according to any one of claims 1 to 3, wherein: The linear carboxylic acid ester includes at least one of methyl formate, methyl acetate, ethyl formate and ethyl acetate.

5. The battery cell according to any one of claims 1 to 4, wherein: The viscosity of the non-aqueous electrolyte at room temperature is 1-3 mPa·s or 2-3 mPa·s.

6. The battery cell according to any one of claims 1 to 5, wherein: When the mass proportion of the lithium nickel cobalt manganese oxide material in the positive electrode active material is ≥10%, the non-aqueous electrolyte further includes a substance containing a sulfur-oxygen bond, and the substance containing a sulfur-oxygen bond includes at least one of vinyl sulfate and 1,3-propane sultone.

7. The battery cell according to claim 6, wherein: The mass content of the substance containing sulfur-oxygen bonds in the non-aqueous electrolyte is 0.5%-4% or 0.5%-2%.

8. The battery cell according to claim 6 or 7, wherein: In the non-aqueous electrolyte, the mass ratio of the 1,3-propane sultone to the vinyl sulfate is greater than 0 and less than 1.

9. The battery cell according to any one of claims 1 to 8, wherein: The non-aqueous electrolyte further comprises a lithium salt, and the mass content of the lithium salt in the non-aqueous electrolyte is 12%-16%.

10. The battery cell according to claim 9, wherein: When the mass proportion of the nickel cobalt manganese oxide material in the positive electrode active material is ≥20%, the lithium salt includes lithium hexafluorophosphate and a fluorosulfonamide lithium salt, and the fluorosulfonamide lithium salt includes at least one of lithium monofluorosulfonyl imide, lithium bisfluorosulfonyl imide, and lithium trifluorosulfonyl imide.

11. The battery cell according to claim 10, wherein: The lithium salt includes lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and the mass ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide is 1.23:1-4.28:

1.

12. The battery cell according to any one of claims 1 to 11, wherein: The non-aqueous electrolyte also includes ethylene carbonate, and the mass content of the ethylene carbonate in the non-aqueous electrolyte is 12%-35%.

13. The battery cell according to any one of claims 1 to 14, wherein: The mass content of Ni element in the positive electrode film layer is 4.5%-25%, the mass content of Fe element in the positive electrode film layer is 15%-33%, and the mass content of vinylene carbonate in the non-aqueous electrolyte is 1%-1.5%.

14. The battery cell according to claim 13, wherein: The mass proportion of the lithium iron phosphate material in the positive electrode active material is 50%-90%.

15. The battery cell according to any one of claims 1 to 14, wherein: The mass proportion of the lithium iron phosphate material in the positive electrode active material is 60%-80%; in the positive electrode active material, the molar proportion of the Ni element in the sum of the three elements Ni, Co and Mn is 0.7-0.

95.

16. The battery cell according to any one of claims 1 to 15, wherein: The lithium iron phosphate material also includes one or more elements of Al, B, Ca, Cr, K, Mg, Ni, Co, Mn, Na, Si, Ti, V, Cu, Zn, S, Sc, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, Cl, C, N, and F.

17. The battery cell according to claim 16, characterized in that One or more of the following: The mass percentage of Al element in the lithium iron phosphate material is 0.01%-0.02%; The mass percentage of element B in the lithium iron phosphate material is 0.08%-0.09%; The mass percentage of Ca element in the lithium iron phosphate material is 0.0001%-0.0003%; The mass proportion of Fe element in the lithium iron phosphate material is 16.035%-35%; The mass proportion of K element in the lithium iron phosphate material is 0.0022%-0.0050%; The mass proportion of Li element in the lithium iron phosphate material is 3%-4.5%; The mass percentage of Mg element in the lithium iron phosphate material is 0.00235%-0.0052%; The mass percentage of Mn element in the lithium iron phosphate material is 0.00205%-0.0050%; The mass percentage of the Na element in the lithium iron phosphate material is 0.018%-0.05%; The mass proportion of P element in the lithium iron phosphate material is 9.265%-19.5%; The mass percentage of Si element in the lithium iron phosphate material is 0.0065%-0.02%; The mass percentage of Ti element in the lithium iron phosphate material is 0.074%-0.16%; The mass proportion of V element in the lithium iron phosphate material is 0.0003%-0.0008%; The mass percentage of Cr element in the lithium iron phosphate material is 0.0004%-0.0012%; The mass proportion of Zn element in the lithium iron phosphate material is 0.00005%-0.0003%.

18. The battery cell according to any one of claims 1 to 17, wherein: The lithium nickel cobalt manganese oxide material also includes one or more elements of Al, B, Fe, Sr, Ti, Y, Zr, Na, K, Mg, Si, P, S, Ca, Sc, V, Cr, Cu, Zn, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce, and F.

19. The battery cell according to claim 18, characterized in that One or more of the following: The mass percentage of Al element in the lithium nickel cobalt manganese oxide material is 0.0315%-0.07%; The mass percentage of element B in the nickel cobalt manganese oxide material is 0.00195%-0.005%; The mass percentage of Co element in the lithium nickel cobalt manganese oxide material is 3.825%-8%; The mass percentage of Fe element in the nickel cobalt manganese oxide material is 0.0016%-0.005%; The mass proportion of Li element in the nickel cobalt manganese oxide material is 5.5%-6.8%; The mass percentage of Mn element in the lithium nickel cobalt manganese oxide material is 1.22%-2.8%; The mass proportion of Ni element in the lithium nickel cobalt manganese oxide material is 24.93%-51%; The mass percentage of Sr element in the nickel cobalt manganese oxide material is 0.00005%-0.0002%; The mass percentage of Ti element in the nickel cobalt manganese oxide material is 0.00015%-0.0004%; The mass proportion of Y element in the nickel cobalt manganese oxide material is 0.0004%-0.0009%; The mass proportion of Zr element in the lithium nickel cobalt manganese oxide material is 0.128%-0.3%.

20. The battery cell according to any one of claims 1 to 19, wherein: The lithium nickel cobalt manganese oxide material includes spherical particles, and the lithium iron phosphate material includes particles having a shape suitable for filling gaps between the spherical particles.

21. The battery cell according to any one of claims 1 to 20, wherein: The lithium nickel cobalt manganese oxide material is a polycrystalline material.

22. The battery cell according to any one of claims 1 to 21, wherein: The lithium nickel cobalt manganese oxide material includes particles with a longest diameter of 4-8 μm and particles with a longest diameter of 0.5-2 μm.

23. The battery cell according to any one of claims 1 to 22, wherein: The lithium iron phosphate material includes particles with a longest diameter of 0.1-0.3 μm and particles with a longest diameter of 1-2 μm.

24. The battery cell according to any one of claims 1 to 23, wherein: The positive electrode film layer also includes a lithium supplement material, which includes one or more of lithium phosphate, dilithium hydrogen phosphate, lithium sulfate, lithium sulfite, lithium molybdate, lithium oxalate, lithium titanate, lithium tetraborate, lithium metasilicate, lithium metamanganate, lithium tartrate, and trilithium citrate.

25. The battery cell according to any one of claims 1 to 24, wherein: The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite and silicon material. The mass proportion of silicon element in the negative electrode film layer is 0.3%-10%.

26. The battery cell according to claim 25, wherein: The silicon material includes one or more of silicon oxide and silicon-carbon composite.

27. The battery cell according to claim 25 or 26, wherein: The silicon material includes a silicon-carbon composite, and the mass proportion of silicon element in the negative electrode film layer is 1%-5%.

28. The battery cell according to any one of claims 1 to 27, wherein: The surface density of the positive electrode film layer is 0.32-0.36 mg / 1540.25 mm 2 .

29. The battery cell according to any one of claims 1 to 28, wherein: The surface density of the negative electrode film layer is 0.169-0.190 mg / 1540.25 mm 2 .

30. The battery cell according to any one of claims 1 to 29, wherein: The ratio of the size of the positive electrode film layer in the first direction to the size of the battery cell in the first direction is ≥92%.

31. The battery cell according to any one of claims 1 to 30, wherein: The ratio of the size of the positive electrode film layer in the second direction to the size of the battery cell in the second direction is ≥93%, and the second direction is perpendicular to the first direction.

32. The battery cell according to any one of claims 1 to 31, wherein: In the battery cell configured to be in a 0% SOC state, a thickness ratio of the positive electrode film layer on any side of the positive electrode collector to the positive electrode collector is 5-8.

33. The battery cell according to any one of claims 1 to 32, wherein: In the battery cell configured to be in a 0% SOC state, a thickness ratio of the negative electrode film layer on any side of the negative electrode current collector to the negative electrode current collector is 13-20.

34. The battery cell according to any one of claims 1 to 33, wherein: The negative electrode film layer includes a first negative electrode film layer located on the negative electrode current collector and a second negative electrode film layer located on the first negative electrode film layer, and the first negative electrode film layer and the second negative electrode film layer include graphite.

35. The battery cell according to any one of claims 1 to 34, wherein: The thickness of the positive electrode current collector is 10-13 μm.

36. The battery cell according to any one of claims 1 to 35, wherein: The thickness of the negative electrode current collector is 4-5.5 μm.

37. The battery cell according to any one of claims 1 to 36, wherein: The electrode assembly includes at least two positive electrode sheets and at least two negative electrode sheets, and the positive electrode sheets and the negative electrode sheets are stacked; the positive electrode sheets and / or the negative electrode sheets include a pole ear portion and a main body portion, the pole ear portion extends from the main body portion along a first direction, and the ratio of the total dimension L1 of the connecting area between the pole ear portion and the main body portion in the second direction to the dimension L of the main body portion in the second direction is ≥50%, and the second direction is perpendicular to the first direction.

38. The battery cell according to any one of claims 1 to 37, wherein: The battery cell includes at least two poles of the same polarity, and the poles are directly electrically connected to the pole lugs of the corresponding polarity.

39. The battery cell according to any one of claims 1 to 38, wherein: The battery cell includes two positive poles and two negative poles, the two positive poles are respectively arranged on the two side surfaces of the battery cell perpendicular to the first direction, the two negative poles are respectively arranged on the two side surfaces of the battery cell perpendicular to the first direction, and the positive poles and the negative poles are arranged opposite to each other along the first direction.

40. The battery cell according to any one of claims 1 to 39, wherein: The electrode assembly has a size of 400-1000 mm in the first direction.

41. The battery cell according to any one of claims 1 to 40, wherein: The size of the electrode assembly in a second direction is 90-120 mm, and the second direction is perpendicular to the first direction.

42. The battery cell according to any one of claims 1 to 41, wherein: The electrode assembly has a dimension of 13-25 μm in a third direction, and the third direction is perpendicular to both the first direction and the second direction.

43. The battery cell according to any one of claims 1 to 42, wherein: The battery cells are configured to be discharged from 4.25V to 2.0V at 1 / 3C with a platform voltage of 3.25-3.44V or 3.32-3.44V.

44. The battery cell according to any one of claims 1 to 43, wherein: The energy density of the battery cell is 210-250Wh / kg.

45. The battery cell according to any one of claims 1 to 44, wherein: The upper limit charging voltage of the battery cell at room temperature is 4.2-4.3V.

46. ​​A battery device comprising the battery cell according to any one of claims 1 to 45; the battery device comprises a battery module, a battery pack or an energy storage device.

47. An electrical device comprising the battery cell according to any one of claims 1 to 45 or the battery device according to claim 46.

48. The electrical device according to claim 47, wherein: The electrical device is a vehicle, and the length direction of the battery cell or the battery device is parallel to the driving direction of the vehicle.

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