Battery cell, battery apparatus and electrical apparatus

Abstract

Provided in the present application are a battery cell, a battery apparatus and an electrical apparatus. The battery cell comprises a casing and an electrode assembly located inside the casing, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet. A positive electrode active material comprises a nickel-containing lithium transition metal oxide and a lithium-containing phosphate. The battery cell is configured to have a specific discharge capacity of 145 mAh / g-210 mAh / g when discharged from 4.3 V to 2.5 V at a rate of 0.33C. The casing has two first side walls parallel to each other in a first direction and two second side walls parallel to each other in a second direction, the first direction and the second direction being perpendicular to each other, the area of each first side wall being greater than the area of each second side wall, and the thickness of each first side wall being 0.1 mm-0.8 mm.

Description

Battery cell, battery device and electric device Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411087367.1, filed on August 8, 2024, entitled “Battery cell, battery device and electric device,” and to Chinese Patent Application No. 202411293407.8, filed on September 14, 2024, entitled “Battery cell, battery device and electric device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of batteries, in particular to a battery cell, a battery device and an electric device. BACKGROUND

[0003] In recent years, the application in the field of electric vehicles has experienced explosive development, at the same time, it also faces key problems such as range anxiety, long charging time, safety performance, etc., which puts forward higher requirements on the energy density, power, cycle stability and safety performance of the battery cell. Among them, the power battery needs to solve the pain point of the range, and the main solution is to improve the energy density. SUMMARY

[0004] The present application provides a battery cell, a battery device and an electric device to improve the energy density of the battery device.

[0005] The first aspect of the present application provides a battery cell, the battery cell comprising a shell and an electrode assembly located inside the shell, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet and a separator film located between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising graphite, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprising a positive electrode active material, the positive electrode active material comprising a lithium transition metal oxide containing nickel and a lithium-containing phosphate, the battery cell being configured to discharge from 4.3V to 2.5V at a rate of 0.33C with a discharge specific capacity of 145mAh / g-210mAh / g; the shell has two first side walls parallel along a first direction and two second side walls parallel along a second direction, the first direction and the second direction being arranged perpendicularly, the area of the first side wall being greater than the area of the second side wall, the thickness of the first side wall being 0.1mm-0.8mm.

[0006] The lithium transition metal oxide containing nickel generally has a high energy density, and the energy density increases with the increase of the nickel content; the lithium-containing phosphate has good structural stability and cycle performance, and has a cost advantage. The two materials are used together in the active material, the advantages are complementary, and it is beneficial to obtain a battery cell with higher energy density, better safety performance, and higher cycle stability at a low cost.

[0007] In the battery cell including the lithium transition metal oxide containing nickel and the lithium-containing phosphate positive electrode active material, when the battery cell is discharged from 4.3V to 2.5V at a rate of 0.33C, the discharge gram capacity is 145mAh / g-210mAh / g, the energy density of the battery cell is high, at this time, the mass content of the lithium transition metal oxide containing nickel in the corresponding positive electrode active material accounts for a high proportion or the mass content of the nickel element in the positive electrode active material is high, correspondingly, at this time, the structural stability of the lithium transition metal oxide of nickel is insufficient, and the problem of nickel dissolution is prone to occur, thereby causing the side reaction of the positive electrode active material and the electrolyte, the risk of gas production is larger, and the risk of the first side wall of the battery cell swelling is increased; at this time, by matching the wall thickness of the first side wall in a reasonable thickness range, the risk of large-area swelling of the battery cell can be effectively reduced, and the battery energy density will not be affected due to the too large wall thickness. Therefore, by matching the above discharge gram capacity and the first side wall thickness, the energy density can be improved as much as possible on the basis of low cost, and the safety of the battery cell with high energy density can be improved.

[0008] In any embodiment of the first aspect, the battery cell is configured to have a discharge gram capacity of 150mAh / g-195mAh / g when discharged from 4.3V to 2.5V at a rate of 0.33C.

[0009] In any embodiment of the first aspect, the mass content of the lithium-containing phosphate in the above positive electrode active material is 50%-90%, which can be selected as 50%-70%, which can further improve the cycle life and maintain a high discharge gram capacity.

[0010] In any embodiment of the first aspect, the lithium transition metal oxide containing nickel includes manganese and cobalt elements, and the molar amount of the nickel element accounts for 50%-95% of the total molar amount of the nickel-cobalt-manganese elements in the lithium transition metal oxide containing nickel, which can be selected as 70%-95%, and further selected as 80%-95%.

[0011] In any embodiment of the first aspect, the thickness of the first side wall of the battery cell is 0.4mm-0.8mm, which can be selected as 0.6mm-0.8mm.

[0012] In any embodiment of the first aspect, the lithium transition metal oxide containing nickel includes one or more of lithium-containing nickel-cobalt-manganese oxides.

[0013] In any embodiment of the first aspect, the lithium-containing nickel transition metal oxide comprises a lithium-containing nickel cobalt manganese oxide, and the lithium-containing nickel cobalt manganese oxide comprises one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V or Y elements.

[0014] In any embodiment of the first aspect, the lithium-containing nickel cobalt manganese oxide comprises one or more of Zr, Al or B.

[0015] In any embodiment of the first aspect, the mass content of the elements in the lithium-containing nickel cobalt manganese oxide satisfies at least one of: the content of Zr is 1000-3000 ppm, the content of Al is 100-1000 ppm, and the content of B is 50-300 ppm. The above elements can exist in the lithium-containing nickel cobalt manganese oxide as dopants or coating materials.

[0016] In any embodiment of the first aspect, the lithium-containing phosphate comprises Mn elements and Fe elements, and the molar content of the Mn elements in the lithium-containing phosphate accounts for 20%-80% of the total molar content of the Mn elements and the Fe elements, which can be 30%-70%, and further can be 50%-70%, which is beneficial to the improvement of the volume energy density, and as the molar content of the Mn elements increases, the platform voltage of the lithium-containing phosphate increases, thereby the energy density of the battery cell can be improved.

[0017] In any embodiment of the first aspect, the lithium-containing phosphate comprises lithium manganese iron phosphate, and the lithium manganese iron phosphate comprises one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn elements.

[0018] In any embodiment of the first aspect, the lithium manganese iron phosphate contains one or more of Al, Ca, Na, Ti or V elements.

[0019] In any embodiment of the first aspect, the mass content of the elements in the lithium manganese iron phosphate satisfies at least one of: the mass content of Al is 100-1000 ppm, the mass content of Ca is 50-300 ppm, the mass content of Na is 50-300 ppm, the mass content of Ti is 100-1000 ppm, and the mass content of V is 1000-3000 ppm. The above elements can exist in the lithium manganese iron phosphate as dopants or coating materials.

[0020] In any embodiment of the first aspect, the positive electrode active layer of the battery cell contains lithium iron manganese phosphate and lithium-containing nickel cobalt manganese oxide, the positive electrode active material contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y or Zr elements, and the mass content of each element satisfies: Al: 0.005%-0.1%; Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V: 0.0001%-0.3%; Zr: 0.005%-0.2%; B: 0.01%-0.1%, based on the total mass of the positive electrode active material.

[0021] In any embodiment of the first aspect, the thickness of the second side wall of the shell is 0.8-1.2 mm, and the thickness of the bottom wall of the shell is 1-1.5 mm.

[0022] In any embodiment of the first aspect, the positive electrode active layer includes a first positive electrode active layer and a second positive electrode active layer, the first positive electrode active layer is arranged close to the positive electrode current collector, and the second positive electrode active layer is arranged on the side of the first positive electrode active layer away from the positive electrode current collector, and the lithium transition metal oxide containing nickel and the lithium-containing phosphate are each independently arranged in the first positive electrode active layer and / or the second positive electrode active layer. The use of a multi-layer coating can further improve the electrical performance, reduce the side reaction of the electrolyte with the positive electrode material, or improve the power performance of the battery cell by reducing the internal resistance.

[0023] In any embodiment of the first aspect, the mass ratio of the positive electrode active layer per unit area to the mass of the positive electrode current collector is (0.15-10):1, which can be (4.5-5.6):1. The positive electrode sheet with the mass ratio in the above range has good processability and lightweight positive electrode sheet arrangement, thereby fully improving the energy density.

[0024] In any embodiment of the first aspect, the negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer, the first negative electrode active layer is arranged close to the negative electrode current collector, and the second negative electrode active layer is arranged on the side of the first negative electrode active layer away from the negative electrode current collector, and the average particle size of the graphite particles arranged in the first negative electrode active layer is greater than the average particle size of the graphite particles arranged in the second negative electrode active layer; optionally, the average particle size of the graphite particles arranged in the first negative electrode active layer is 12-25 μm, and the average particle size of the graphite particles arranged in the second negative electrode active layer is 5-12 μm.

[0025] In any embodiment of the first aspect, the second side wall of the shell is provided with an explosion-proof valve, the area of the explosion-proof valve is 8%-20% of the area of the second side wall, optionally 12%-16%, which is conducive to rapid pressure relief, thereby improving the safety of the high-energy-density battery cell. In any embodiment of the first aspect, the battery cell comprises at least one top cover assembly, the top cover assembly is connected to the first side wall and the second side wall by welding; each top cover assembly comprises a positive electrode terminal and a negative electrode terminal, and the electrode assembly comprises a positive electrode tab portion and a negative electrode tab portion stacked together, the positive electrode tab portion is welded to the positive electrode terminal, and the negative electrode tab portion is welded to the negative electrode terminal, wherein the welding area between the positive electrode tab portion and the single positive electrode terminal is set to 0.5mm 2 / Ah-1 mm 2 / Ah, and / or the welding area between the negative electrode tab portion and the single negative electrode terminal is set to 0.5mm 2 / Ah-1 mm 2 / Ah.

[0026]

[0027] In any embodiment of the first aspect, the injection coefficient of the battery cell is 1.8g / Ah-3.5g / Ah, optionally 1.9g / Ah-3.1g / Ah. The injection coefficient in the above range can improve the wettability of the battery cell while inhibiting side reactions and reducing cycle gas production, thereby improving the cycle life of the battery cell.

[0028] The second aspect of the present application provides a battery device comprising a battery cell, the battery cell comprising any one of the battery cells of the first aspect, and the battery device comprising a battery module, a battery pack or an energy storage device.

[0029] The third aspect of the present application provides a power consumption device comprising any one of the battery cells of the first aspect or the battery device of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] FIG. 1 is a schematic diagram of a battery assembly according to an embodiment of the present application.

[0032] FIG. 2 is a schematic diagram of a shell according to an embodiment of the present application.

[0033] FIG. 3 is an exploded view of a battery cell according to an embodiment of the present application.

[0034] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application.

[0035] FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4.

[0036] FIG. 6 is a schematic view of an electric device using the battery pack according to an embodiment of the present application as a power source.

[0037] In the drawings, the drawings are not drawn to scale.

[0038] Explanation of Reference Numerals:

[0039] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 case; 52 electrode assembly; 53 top cap assembly; 11 first side wall; 12 second side wall; 13 explosion-proof valve. DETAILED DESCRIPTION

[0040] Embodiments of the present application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following examples and the accompanying drawings are intended to illustrate the principles of the present application by way of example, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described examples.

[0041] Hereinafter, embodiments of the battery cell, the battery device, and the electric device according to the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0042] The ranges disclosed herein are meant to be inclusive of the endpoints and include the end values in the range. Ranges can be combined to form new ranges, e.g., a range of "60-120 and 80-110" is understood to include 60-110 and 80-120. Further, if a minimum range value is listed as 1 and a maximum range value is listed as 3, then the following ranges are all contemplated: 1-3, 1-2, 2-3, 1-2, 2-3, and 1-3. In this application, unless otherwise indicated, a numerical range "a-b" is intended to indicate any and all sub-combinations of the values in that range, wherein a and b are both real numbers. For example, the numerical range "0-5" is intended to indicate that all real numbers between 0 and 5, inclusive of the endpoints, have been listed herein, and that "0-5" is merely a shorthand for listing all of those numbers. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to state that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0043] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0044] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0045] All steps of the present application can be performed in sequence or randomly, preferably in sequence, unless otherwise specified. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0046] Unless otherwise specified, "including" and "comprising" mentioned in the present application are open-ended. For example, "including" and "comprising" can mean that other components not listed can also be included or contained.

[0047] If not specifically stated, the term "or" in this application is inclusive. For example, any of the following satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0048] [Battery cell]

[0049] The structural design of the battery cell and the physical and chemical properties of the electrode assembly thereof have an important influence on the key performance indicators of the battery cell. In view of the problem of improving the energy density of the battery cell, the first embodiment of the present application provides a battery cell, which comprises a shell and an electrode assembly located inside the shell, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator film located between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, the negative electrode active material comprising graphite, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, the positive electrode active layer comprising a positive electrode active material, the positive electrode active material comprising a lithium transition metal oxide containing nickel and a lithium-containing phosphate, the battery cell being configured to have a discharge specific capacity of 145 mAh / g-210 mAh / g when discharged from 4.3 V to 2.5 V at a rate of 0.33 C; the shell has two first side walls 11 parallel along a first direction and two second side walls 12 parallel along a second direction, the first direction and the second direction being arranged perpendicularly, the area of the first side wall 11 being greater than the area of the second side wall 12, and the thickness of the first side wall 11 being 0.1 mm-0.8 mm.

[0050] During the charging and discharging process of the battery, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The separator film is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting of the positive and negative electrodes, while allowing the active ions to pass through. For example, FIG. 1 is an electrode assembly 52 of a cuboid structure as an example.

[0051] The lithium transition metal oxide containing nickel generally has a high energy density, and the energy density will correspondingly increase with the increase of the nickel content; the lithium-containing phosphate has good structural stability and cycle performance, and has a cost advantage, and the two materials are used together in the active material, complementing each other's advantages, which is conducive to obtaining a battery cell with higher energy density, more excellent safety performance, and higher cycle stability at a low cost.

[0052] When the battery monomer is configured to be discharged from 4.3V to 2.5V at a rate of 0.33C, the discharge gram capacity is 145mAh / g-210mAh / g, the energy density of the battery monomer is high, at this time, the mass content of the nickel-containing lithium transition metal oxide in the corresponding positive electrode active material accounts for a high proportion or the mass content of the nickel element in the positive electrode active material is high, accordingly, at this time, the structure stability of the nickel-containing lithium transition metal oxide is insufficient, and the problem of nickel dissolution is prone to occur, thereby causing the side reaction of the positive electrode active material and the electrolyte, the risk of gas production is larger, and the risk of the first side wall of the battery monomer swelling is increased; at this time, by matching the wall thickness of the first side wall in a reasonable thickness range, the risk of the large surface (i.e. the first side wall) of the battery monomer swelling can be effectively reduced, and the battery energy density will not be affected due to the excessively large wall thickness. Therefore, by matching the above discharge gram capacity and the first side wall thickness, the energy density can be improved as much as possible on the basis of low cost, and the safety of the high-energy-density battery monomer can be improved.

[0053] For ease of understanding, FIG. 2 shows a structural schematic diagram of a shell 51 in an embodiment. The shell is rectangular, and the shell 51 can include a bottom plate and two pairs of side plates arranged vertically to the bottom plate. One pair of side plates with a larger area constitutes a first side wall 11, and the other pair of side plates with a smaller area perpendicular to the side plates constitutes a second side wall 12. The thickness of the first side wall 11 with a larger area is 0.1mm-0.8mm (such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm or 0.8mm). When the wall thickness is large, the capacity of the battery monomer under low-temperature conditions can be improved; in addition, as the wall thickness decreases, the volume energy density of the battery monomer can be effectively improved. Moreover, the thickness of the above-mentioned first side wall 11 can meet the safety requirements of the high-energy-density battery monomer.

[0054] In some embodiments, the battery monomer is configured to be discharged from 4.3V to 2.5V at a rate of 0.33C, and the discharge gram capacity is 150mAh / g-195mAh / g, which can further improve the cycle stability while maintaining high energy density.

[0055] The determination method of the elements contained in the above-mentioned positive electrode active material is as follows:

[0056] The positive electrode active material in the positive electrode active layer is collected after the positive electrode active material is washed with dimethyl carbonate (DMC), and the positive electrode active material is dried and calcined. The positive electrode active material is tested by inductively coupled plasma atomic emission spectrometry (ICP-OES).

[0057] The determination method of the above-mentioned discharge gram capacity is as follows:

[0058] The battery monomer is placed at room temperature, and charged at a rate of 0.33C to 4.3V, and then charged at a constant voltage of 0.05C. The discharge capacity C0(unit: mAh) of the battery monomer is recorded when discharging at a rate of 0.33C from 4.3V to 2.5V, and C is the nominal capacity of the battery monomer.

[0059] The positive electrode sheet of the battery monomer is washed with dimethyl carbonate (DMC), and the positive electrode sheet is dried and calcined to collect the positive electrode material in the positive electrode active layer, weighed, and recorded as m(unit: g); the discharge gram capacity = C0 / m.

[0060] In some embodiments, the mass content of the lithium-containing phosphate in the positive electrode active material of the battery monomer is 50%-90%, and optionally 50%-70%. The lithium-containing phosphate and the lithium transition metal oxide containing nickel are combined in the above mass content range, and the advantages of the two are fully exerted, so that the energy density and cycle performance of the battery monomer are fully improved. In some embodiments, the lithium transition metal oxide containing nickel includes manganese and cobalt elements, and the molar amount of nickel elements in the lithium transition metal oxide containing nickel accounts for 50%-95%, optionally 70%-95%, and further optionally 80%-95% of the total molar amount of nickel, cobalt and manganese elements. Nickel elements help to improve the gram capacity of the positive electrode active material and play a role in improving the energy density of the battery monomer. In some embodiments, when the molar amount of nickel elements accounts for 80%-95%, the wall thickness of the first side wall can be selected to be 0.6mm-0.8mm to improve the safety performance of the battery monomer.

[0061] In some embodiments, the lithium transition metal oxide containing nickel includes one or more of lithium-containing nickel-cobalt-manganese oxides.

[0062] Examples of lithium transition metal oxides containing nickel can 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 manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to as NCM 211 ), LiNi 0.6Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 ) and modified compounds thereof, etc. Examples of lithium-containing phosphates can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0063] In some embodiments, the lithium-containing transition metal oxide containing nickel includes lithium-containing nickel cobalt manganese oxide, the lithium-containing nickel cobalt manganese oxide includes one or more of Zr, Al, B, Fe, Ca, Sr, Ti, V or Y elements, and the above elements can exist in the lithium-containing nickel cobalt manganese oxide as dopants or coating materials.

[0064] In some embodiments, the lithium-containing nickel cobalt manganese oxide includes one or more of Zr, Al, B or Fe elements, wherein Zr 4+ may simultaneously occupy the Ni 2+ site and the Li + site, reduces the mixing of Ni and Li elements, improves the ionic conductivity, the strong chemical bond between Zr-O is conducive to stabilizing the crystal structure of the layered material and plays a supporting role in the process of lithium extraction / insertion. Al 3+ dissolved in the transition metal layer of the lithium-containing nickel cobalt manganese oxide in the form of a solid solution, which can effectively improve the capacity retention during the cycle process. Boron anion doping can alleviate the strain of the lithium-containing nickel cobalt manganese oxide during the process of lithiation / delithiation, and improve the cycle stability and life.

[0065] In order to fully exert the role of each element, in some embodiments, the mass content of elements in the lithium-containing nickel cobalt manganese oxide satisfies at least one of the following: the content of Zr is 1000 ppm to 3000 ppm, the content of Al is 100 ppm to 1000 ppm, and the content of B is 50 ppm to 300 ppm.

[0066] In some embodiments, the lithium-containing phosphate includes Mn elements and Fe elements, and the molar amount of the Mn elements in the lithium-containing phosphate is 20% to 80% of the total molar amount of the Mn elements and the Fe elements, which can be optionally 30% to 70%, and further optionally 50% to 70%. The molar amount of the Mn elements is within the above range, and as the molar amount of the Mn elements increases, the platform voltage of the lithium-containing phosphate increases, thereby improving the energy density of the battery cell.

[0067] In some embodiments, the lithium-containing phosphate includes lithium iron manganese phosphate, and the lithium iron manganese phosphate includes one or more of Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V, or Zn, and optionally, the lithium iron manganese phosphate includes one or more of Al, Ca, Na, Ti, or V, which can exist in the lithium iron manganese phosphate as a dopant or a coating material.

[0068] Doping one or more of the above elements into the lithium iron manganese phosphate cathode material can promote Li + lattice migration by introducing lattice vacancies or changing atomic bond length, which can improve the electrical conductivity of the material. For example, Mg doping can improve the electrical conductivity while improving the structural stability; Al doping can improve the electrical conductivity of the material and help to inhibit phase transition under high voltage or deep discharge; Ca doping can improve the cycle stability; Na doping can promote the ion diffusion rate and improve the specific capacity; Ti doping can provide additional Li + sites, improve the specific capacity, and help to reduce the dissolution of Mn during the cycle; V doping can improve the electrical conductivity and electrochemical activity, and improve the charge and discharge performance.

[0069] To fully exert the effects of the elements, further optionally, in the lithium iron manganese phosphate, the mass content of the elements satisfies at least one of the following: the mass content of Al is 100 ppm to 1000 ppm, the mass content of Ca is 50 ppm to 300 ppm, the mass content of Na is 50 ppm to 300 ppm, the mass content of Ti is 100 ppm to 1000 ppm, and the mass content of V is 1000 ppm to 3000 ppm.

[0070] In some embodiments, the lithium iron manganese phosphate and the lithium-containing nickel cobalt manganese oxide are contained in the positive electrode active layer, and the positive electrode active material contains one or more of Al, B, Ca, Na, Sr, Ti, V, Y, or Zr, and to fully exert the effects of the elements, based on the total mass of the positive electrode active material, the mass content of each element satisfies: Al: 0.005% to 0.1%; Ca: 0.0001% to 0.02%; Na: 0.005% to 0.06%; Ti: 0.005% to 0.15%; V: 0.0001% to 0.3%; Zr: 0.005% to 0.2%; and B: 0.01% to 0.1%.

[0071] The content of each of the above elements can refer to the determination method of the elements contained in the aforementioned positive electrode active material.

[0072] In some embodiments, the positive electrode active layer comprises a first positive electrode active layer and a second positive electrode active layer, the first positive electrode active layer is arranged close to the positive electrode current collector, and the second positive electrode active layer is arranged on the side of the first positive electrode active layer away from the positive electrode current collector. The lithium-containing phosphates and the lithium-containing transition metal oxides are independently arranged in the first positive electrode active layer and / or the second positive electrode active layer.

[0073] The use of a multi-layer coating can further improve the electrical performance:

[0074] On the one hand, the lattice water in the lithium-containing phosphates is relatively high, and direct contact with the electrolyte can cause side reactions, affecting the cycle life of the battery cell. Therefore, when the positive electrode active material in the first positive electrode active layer is mainly lithium-containing phosphates, and the positive electrode active material in the second positive electrode active layer is mainly lithium-containing transition metal oxides containing nickel, the second positive electrode active layer establishes a physical barrier between the lithium-containing phosphates and the electrolyte, which can effectively reduce the probability of electrolyte side reactions.

[0075] For example, the positive electrode active material in the first positive electrode active layer is lithium-containing phosphates, and the positive electrode active material in the second positive electrode active layer is lithium-containing transition metal oxides containing nickel; or the positive electrode active material in the first positive electrode active layer is lithium-containing phosphates, and the positive electrode active material in the second positive electrode active layer is lithium-containing transition metal oxides containing nickel and a small amount of lithium-containing phosphates; or the positive electrode active material in the first positive electrode active layer is lithium-containing phosphates and a small amount of lithium-containing transition metal oxides containing nickel.

[0076] On the other hand, the ion mobility and electronic conductivity of lithium-containing phosphates are lower than those of transition metal oxides. When the positive electrode active material in the first positive electrode active layer is mainly lithium-containing transition metal oxides containing nickel, and the positive electrode active material in the second positive electrode active layer is mainly lithium-containing phosphates, the lithium-containing phosphates contact the electrolyte more quickly, shortening the ion transport distance, thereby reducing the internal resistance and facilitating the power improvement of the battery cell.

[0077] For example, the positive electrode active material in the first positive electrode active layer is lithium-containing transition metal oxides containing nickel, and the positive electrode active material in the second positive electrode active layer is lithium-containing phosphates; or the positive electrode active material in the first positive electrode active layer is lithium-containing transition metal oxides containing nickel and a small amount of lithium-containing phosphates, and the positive electrode active material in the second positive electrode active layer is lithium-containing phosphates; or the positive electrode active material in the first positive electrode active layer is lithium-containing transition metal oxides containing nickel, and the positive electrode active material in the second positive electrode active layer is lithium-containing phosphates and a small amount of lithium-containing transition metal oxides containing nickel; or the positive electrode active material in the first positive electrode active layer is lithium-containing transition metal oxides containing nickel and a small amount of lithium-containing phosphates, and the positive electrode active material in the second positive electrode active layer is lithium-containing phosphates and a small amount of lithium-containing transition metal oxides containing nickel.

[0078] In some embodiments, the positive current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, the mass ratio of the single layer of the positive active layer per unit area to the positive current collector is (0.15-10): 1, and can be (4.5-5.6): 1. The higher the mass ratio, the more conducive to the lightweight of the battery cell and the improvement of the energy density; but if the mass ratio is too high, the mechanical strength of the positive electrode sheet will be affected and it will not be easy to process.

[0080] In some embodiments, the positive active layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0081] In some embodiments, the positive active layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive current collector, and after drying, cold pressing, etc., the positive electrode sheet can be obtained.

[0083] [Negative electrode sheet]

[0084] In some embodiments, the negative active layer includes a first negative active layer and a second negative active layer, the first negative active layer is disposed close to the negative current collector, the second negative active layer is disposed on a side of the first negative active layer away from the negative current collector, the average particle size of the graphite particles disposed in the first negative active layer is greater than the average particle size of the graphite particles disposed in the second negative active layer; optionally, the average particle size of the graphite particles disposed in the first negative active layer is 12-25 μm, and the average particle size of the graphite particles disposed in the second negative active layer is 5-12 μm. The small-particle-size graphite transmission path of the second negative active layer is relatively short, has excellent kinetics, and can make the internal resistance lower to obtain better power performance. However, the small-particle-size graphite has a large contact area with the electrolyte, is prone to cause side reactions, and affects the cycle life, and therefore the first negative active layer adopts large-particle-size graphite, which is beneficial to delaying the cycle life and further optimizing the cycle life.

[0085] In some embodiments, the negative current collector can adopt a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be adopted. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can 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 base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0086] In some embodiments, the negative film layer can further optionally include a binder. As an example, the binder can 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).

[0087] In some embodiments, the negative film layer can further optionally include a conductive agent. As an example, the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative film layer can further optionally include other auxiliary agents, such as a thickening agent (such as sodium carboxymethyl cellulose CMC-Na) and the like.

[0089] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and then drying, cold-pressing, or the like to obtain the negative electrode sheet.

[0090] [Electrolyte]

[0091] In some embodiments, the above-mentioned battery cell includes an electrolyte, which functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not have a specific limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0092] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0093] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorodioxalate phosphate.

[0094] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0095] In some embodiments, the electrolyte solution can also optionally include an additive. As an example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0096] [Separator]

[0097] In some embodiments, the battery cell further includes a separator. The present application does not have a specific limitation on the type of separator, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0098] In some embodiments, the material of the separation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separation film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separation film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0099] In some embodiments, the positive electrode tab, the negative electrode tab, and the separation film can be formed into an electrode assembly by a winding process or a stacking process.

[0100] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, FIG. 1 is an electrode assembly 52 of a battery cell in a square structure as an example.

[0101] In some embodiments, referring to FIG. 2, the outer package can include a shell 51 and a top cover assembly 53. The shell 51 can 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 communicating with the receiving cavity, and the top cover assembly 53 can be arranged on the opening to close the receiving cavity. The positive electrode tab, the negative electrode tab, and the separation film can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and can be selected by a person skilled in the art according to specific actual needs. The second embodiment of the present application also provides a battery device, which includes any one of the battery cells provided by the first embodiment described above, and the battery device includes a battery module, a battery pack, or an energy storage device.

[0102] Since the battery cell of the present application has a high energy density, in order to further improve the safety of the battery cell during long-term use and control the influence of the wall thickness on the energy density of the battery cell as much as possible, in some embodiments, the thickness of the first side wall 11 of the shell is 0.4 mm to 0.8 mm, which can be selected as 0.6 mm to 0.8 mm.

[0103] The area of the second side wall 12 and the bottom wall of the battery cell shell is relatively small, so the change of the thickness has little effect on the energy density of the battery cell, but can improve the safety of the battery cell. In some embodiments, the thickness of the second side wall 12 is 0.8 mm to 1.2 mm, and / or the thickness of the bottom wall of the shell is 1 mm to 1.5 mm.

[0104] In some embodiments, the battery cell shell can be a steel shell, such as a stainless steel shell, which has a large structural strength, and accordingly can reduce the wall thickness. In some embodiments, the wall thickness of the steel shell is 0.1-0.5 mm. In some embodiments, the battery cell shell can be an aluminum alloy shell. Aluminum alloy has the characteristics of low density and corrosion resistance, and thus the aluminum alloy shell has the advantages of light weight, strong corrosion resistance, good heat dissipation, and easy processing. In some embodiments, the wall thickness of the aluminum alloy shell is 0.6-1.0 mm.

[0105] In some embodiments, as shown in FIG. 2, the second side wall of the battery cell shell is provided with an explosion-proof valve 13. Since the battery cell of the present application has a high energy density, in order to further improve the safety of the battery cell, in some embodiments, the area of the explosion-proof valve 13 is 8%-20% of the area of the second side wall 12, and optionally 12%-16%. The area of the explosion-proof valve in the present application increases relative to the area of the explosion-proof valve of a conventional battery cell, and thus is beneficial for rapid pressure relief, and can improve the safety of the high-energy-density battery cell.

[0106] In some embodiments, the battery cell includes at least one top cover assembly, and the top cover assembly is connected to the first side wall and the second side wall by welding. Each top cover assembly includes a positive electrode terminal and a negative electrode terminal, and the electrode assembly includes a positive electrode tab portion and a negative electrode tab portion stacked together. The positive electrode tab portion is welded to the positive electrode terminal, and the negative electrode tab portion is welded to the negative electrode terminal. In some embodiments, the welding area between the positive electrode tab portion and the positive electrode terminal is set to 0.5 mm 2 / Ah-1 mm 2 / Ah, and / or the welding area between the negative electrode tab portion and the negative electrode terminal is set to 0.5 mm 2 / Ah-1 mm 2 / Ah. Each top cover assembly includes a positive electrode terminal and a negative electrode terminal, which is beneficial for improving the overcurrent capacity of the battery cell and reducing the internal temperature rise of the battery cell. The welding area is designed according to the capacity of the battery cell, so as to better control the internal temperature rise of the battery cell and improve the overcurrent capacity of the battery cell. Since the discharge specific capacity of the battery cell of the present application is high, the energy density of the battery cell is high under the same weight, and the corresponding welding area is large, so as to reduce the internal resistance of the battery and improve the power capability of the battery cell.

[0107] In some embodiments, the injection coefficient of the battery cell is 1.8 g / Ah-3.5 g / Ah, and optionally 1.9 g / Ah-3.1 g / Ah.

[0108] The higher the injection coefficient of the battery cell is, the more electrolyte means. By controlling the injection coefficient, on the one hand, the content of unstable components (such as non-oxidation solvent cyclic ester, carboxylic acid ester, etc.) in the electrolyte is controlled, thereby inhibiting side reactions, reducing cycle gas production, and improving cycle life; on the other hand, the wettability of the battery cell is improved, so that the electrolyte has a high wettability effect on the pole piece even after a long time of cycle, thereby improving the cycle life of the battery cell.

[0109] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0110] In the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the thickness direction of the battery module 4. Of course, it can also be arranged in any other way. Further, the plurality of battery cells can be fixed by fasteners.

[0111] Optionally, the battery module can further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0112] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0113] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be arranged on the lower box body 3 to 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.

[0114] In addition, the application also provides a power utilization device, which includes the battery cell or the battery device provided by the application. The battery cell or the battery device can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. As the power utilization device, the battery cell, the battery module or the battery pack can be selected according to the use demand thereof.

[0115] FIG. 6 is an example of a power consuming device. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the power consuming device for the battery cell, a battery pack or a battery module can be used.

[0116] [Embodiment]

[0117] Hereinafter, an embodiment of the present application will be described. The embodiment described below is exemplary and is for the purpose of explanation of the present application only and is not to be understood as a limitation of the present application. In the embodiment, unless a specific technique or condition is specified, the technique or condition described in the literature in the art or according to the product manual is used. Unless the manufacturer of the reagent or instrument is specified, it is a conventional product that can be obtained on the market.

[0118] Embodiment 1

[0119] The battery cell was prepared as follows.

[0120] Positive electrode tab:

[0121] The positive electrode active layer includes a positive electrode active material, a binder polyvinylidene fluoride, and a conductive agent acetylene black (mass ratio of 96.7:2.3:1). In the positive electrode active material, the mass ratio of lithium transition metal oxide containing nickel and lithium-containing phosphate is 3:7. The chemical formula of the lithium transition metal oxide containing nickel is Li(Ni 0.9 Co 0.05 Mn 0.05 )O2, and the chemical formula of the lithium-containing phosphate is Li(Fe 0.5 Mn 0.5 )PO4.

[0122] The other elements in the positive electrode active material are all from the lithium transition metal oxide containing nickel, and the subscripts of Ni, Co, and Mn in the chemical formula are the data after rounding. Since the content of the other elements M is trace or even lower, these elements and the number of moles are not reflected in the chemical formula. The element M does not affect the performance of the battery cell, and in the chemical formula Li(Ni 0.90 Co 0.05 Mn 0.05 )O2, the mass content of each element in the element M is: Al: 0.081%, B: 0.091%, Na: 0.0093%, S: 0.082%, Sb: 0.014%, Sr: 0.025%, W: 0.035%, and Zr: 0.143%.

[0123] The thickness of the positive electrode current collector aluminum foil is 13 μm, and the positive electrode active layer is located on both sides of the aluminum foil. The mass ratio of the positive electrode active material in the positive electrode active layer to the current collector is 5.19:1.

[0124] The conductive primer layer between the positive active layer and the aluminum foil is a film layer formed by uniformly mixing the positive electrode conductive agent super conductive carbon, the positive electrode binder polyacrylate and the solvent, coating on the surface of the positive electrode current collector and drying, the thickness is 1 μm, the mass content of the positive electrode conductive agent in the positive electrode conductive layer is 50%, and the mass content of the positive electrode binder in the positive electrode conductive layer is 50%. The length of the positive electrode plate is 592 mm.

[0125] The area density of the positive electrode plate is 315 mg / 1540.25 mm 2 .

[0126] The negative electrode plate:

[0127] The negative active layer includes 96:1:2:1 of the negative active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber and the thickening agent sodium carboxymethyl cellulose, the negative active layer includes the first negative active layer and the second negative active layer, the average particle size of the graphite particles arranged in the first negative active layer is 25 μm, and the average particle size of the graphite particles arranged in the second negative active layer is 12 μm.

[0128] The negative electrode current collector is a copper foil of 5 μm, and there is a negative electrode conductive layer between the copper foil and the negative active layer, the conductive primer layer is a film layer formed by uniformly mixing the negative electrode conductive agent super conductive carbon, the negative electrode binder styrene butadiene rubber SBR, the thickening agent sodium carboxymethyl cellulose (CMC-Na) and the solvent water, coating on the surface of the negative electrode current collector and drying, the thickness is 1 μm, the mass content of the negative electrode conductive agent in the negative electrode conductive layer is 35%, the mass content of the negative electrode binder in the negative electrode conductive layer is 60%, and the mass content of the thickening agent in the negative electrode conductive layer is 5%.

[0129] The area density of the negative electrode plate is 165 mg / 1540.25 mm 2 .

[0130] The electrolyte includes an organic solvent, a lithium salt and an additive, wherein:

[0131] The organic solvent is a mixture of a cyclic carbonate and a linear carbonate, the cyclic carbonate is ethylene carbonate (EC), the linear carbonate is dimethyl carbonate (DMC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) mixed in a mass ratio of 13:40:12 to obtain, and the rest of the solvent is EC;

[0132] The lithium salt is lithium hexafluorophosphate (LiPF6) with a concentration of 1.2 mol / L;

[0133] The additive composition is as follows: 2.5 wt% of vinylene carbonate (VC), 1 wt% of fluoroethylene carbonate (FEC), 0.5 wt% of 1,3 propylene sulfite (PS), 0.5 wt% of vinyl sulfite (DTD), and 0.5 wt% of lithium difluorophosphate (LiPO2F2).

[0134] The separator film:

[0135] A polyethylene (PE) film coated with an alumina inorganic coating and a PVDF organic coating was used as the separator film, the thickness of the polyethylene film was 7 μm, and the separator film was purchased from Zhgaotek Technology Co., Ltd.

[0136] Assembly of the battery monomer:

[0137] The electrode assembly was obtained by stacking the positive electrode tab, the separator film, and the negative electrode tab. The top cover assembly of the electrode assembly included a positive electrode terminal and a negative electrode terminal. The positive electrode terminal was welded with the positive electrode tab, and the negative electrode terminal was welded with the negative electrode tab. The welding area between the unit discharge capacity positive electrode tab and the positive electrode terminal was 0.8 mm 2 ·Ah -1 ; the welding area between the unit discharge capacity negative electrode tab and the negative electrode terminal was 0.8 mm 2 ·Ah -1 .

[0138] The electrode assembly was added to the shell, and after drying, electrolyte was injected, the injection coefficient was 2.9 g / Ah, the shell was a square aluminum shell, and the size parameters were as follows: length was 600 mm, thickness was 19 mm, height was 105 mm, first side wall thickness was 0.6 mm, second side wall thickness was 1 mm, bottom wall thickness was 1.2 mm, and the area ratio of the explosion-proof valve on the second side wall was 16%;

[0139] After packaging, high-temperature standing, formation, secondary injection, aging, and capacity processes, the battery monomer was obtained.

[0140] [Performance test of the battery monomer]

[0141] Test method of discharge gram capacity:

[0142] The battery monomer was placed at room temperature, charged at a rate of 0.33 C to 4.3 V, and then charged at a constant voltage to 0.05 C. The discharge capacity C0 (unit: mAh) of the battery monomer was recorded when discharged at a rate of 0.33 C from 4.3 V to 2.5 V, and C was the nominal capacity of the battery monomer. The positive electrode tab of the battery monomer was thoroughly cleaned with dimethyl carbonate (DMC), and the positive electrode tab was dried and calcined to collect the positive electrode material in the positive electrode active layer, which was weighed and recorded as m (unit: g). The discharge gram capacity = C0 / m.

[0143] Test method of volume energy density:

[0144] The battery monomer is charged at room temperature at a rate of 0.33C to 4.3V, and then charged at constant voltage to 0.05C, and the discharge capacity A0 (unit: Ah) of the battery monomer discharged at a rate of 0.33C from 4.3V to 2.5V is recorded, and C is the nominal capacity of the battery monomer; the length, width and height of the battery monomer are measured using a caliper (generally calculated based on the size of the battery shell, excluding the height of the electrode terminal, and excluding the insulating film outside the shell), and the volume V0 of the battery monomer is calculated, unit L; the volume energy density VED of the battery monomer is (A0x discharge platform voltage) / V0, unit Wh / L.

[0145] Test method of cycle performance:

[0146] At room temperature, the battery monomer is charged and discharged between 2.5V and 4.3V, and the specific operation is as follows: charged at 0.33C to 4.3V, then charged at constant voltage at 4.3V to a current not higher than 0.05C, and then discharged at 1C to 2.5V, and the capacity is recorded as C m (m = 1, 2, 3…), repeat the above operation, and the capacity retention rate is C m / C3 ratio. When C m / C3x100% = 80%, record the corresponding cycle number as the examination index of cycle capacity, and the more the cycle number, the better the cycle performance of the battery monomer.

[0147] The nickel-containing lithium transition metal oxide and lithium-containing phosphate used in the examples and comparative examples are all conventional materials in the art or prepared by conventional methods.

[0148] On the basis of Example 1, Comparative Examples 1 to 3 only adjust the composition of the positive active material, and the rest of the positive electrode sheet is the same as Example 1, and the negative electrode sheet, the separator, the electrolyte and the outer packaging shell of the battery monomer are all the same as Example 1, which aims to investigate the influence of different positive electrode material design schemes on the discharge gram capacity of the positive electrode sheet.

[0149] The specific adjustment is shown in Table 1, and the battery monomer performance test results of each example are recorded in Table 1.

[0150] Table 1

[0151] From the data in Table 1, it can be seen that the positive electrode active material design of Example 1 can keep the energy density and cycle performance at a high level, and the overall performance of the battery cell is more balanced. When the positive electrode active material is essentially a lithium-containing phosphate, the discharge gram capacity of the positive electrode sheet is low, the energy density of the battery cell is limited, and the cycle performance is not as good as Example 1, and Comparative Examples 1 and 3 belong to this category. The discharge gram capacity of the positive electrode sheet in the above two comparative examples is less than 145 mAh / g. When the positive electrode active material is essentially a high-nickel lithium transition metal oxide, such as Comparative Example 2, the energy density can reach a very high level (such as higher than 210 mAh / g), which will increase the risk of thermal runaway of the battery cell in working state, in addition, it will cause the cycle performance of the battery cell to decrease significantly, which is related to the inherent structural instability of the high-nickel lithium transition metal oxide system.

[0152] In view of the safety performance of the battery cell, while improving the energy density, it is necessary to be accompanied by reasonable design of the shell of the battery cell. The following examples and comparative examples adjust the shell thickness of the battery cell according to the characteristics of the respective positive electrode active materials. The nickel-containing lithium transition metal oxides in the positive electrode active materials of each example and comparative example are different, and the lithium-containing phosphate is Li(Fe 0.5 Mn 0.5 )PO4, the mass content of the lithium-containing phosphate in the positive electrode active material is 70%, the remaining settings of the positive electrode sheet and the settings of the negative electrode sheet, electrolyte and separator are kept consistent, and the tab welding area per unit discharge capacity is 0.8 mm 2 ·Ah -1 .

[0153] Specifically, the composition of the nickel-containing lithium transition metal oxide and the shell size parameter adjustment in each example and comparative example are shown in Table 2, and the performance test results of the corresponding positive electrode sheet and battery cell are also presented in Table 2.

[0154] Table 2 Note: Comparative Example 5 experienced serious bulging of the first side wall after charge-discharge cycling.

[0155] In the nickel-containing lithium transition metal oxide with the chemical formula Li(Ni 0.93 Co 0.06 Mn 0.01 )O2, Li(Ni 0.95 Co 0.03 Mn 0.02 )O2 in Table 2, the mass content of each element in element M is: Al: 0.081%, B: 0.091%, Na: 0.0093%, S: 0.082%, Sb: 0.014%, Sr: 0.025%, W: 0.035%, Zr: 0.143%.

[0156] Li(Ni 0.50 Co 0.20 Mn 0.30 )O2, the mass content of each element in the element M is: Al: 0.0054%, B: 0.0024%, Ca: 0.0032%, Cr: 0.0001%, Cu: 0.0003%, Mg: 0.0037%, Na: 0.010%, S: 0.063%, Sr: 0.085%, Ti: 0.175%, W: 0.059%, Y: 0.0001%, Zn: 0.0002%, Zr: 0.125%.

[0157] In Table 2, the shell with a first side wall thickness of 0.4 mm or 0.08 mm is a stainless steel shell to enhance the shell strength.

[0158] In Examples 1 and 2, the mole ratio of the element nickel in the nickel-containing lithium transition metal oxide system to the elements nickel, cobalt and manganese is more than 90%, which can provide a high energy density. In order to enhance the safety of the battery monomer, a relatively thick shell is used, which increases the volume and weight of the battery monomer, which to some extent reduces the energy density of the battery monomer. A too thick shell will seriously affect the overall performance of the battery monomer. For example, the first side wall thickness of Comparative Example 4 is as high as 1.2 mm, which significantly reduces the volume energy density of the battery monomer.

[0159] In Examples 3 and Comparative Example 5, the mole ratio of the element nickel in the nickel-containing lithium transition metal oxide system to the elements nickel, cobalt and manganese is 50%, which cannot provide a high energy density like Example 1, but has excellent cycle performance, and does not need to thicken the shell to enhance the safety of the battery monomer. However, the first side wall thickness of the shell of Comparative Example 5 is only 0.08 mm, and a more serious bulging problem of the first side wall of the battery occurs during the cycle process. A too thin shell increases the risk of thermal runaway of the battery monomer. Once thermal runaway occurs, the shell may burst, causing a very high risk of out-of-control.

[0160] On the basis of Example 1, by adjusting the composition of the nickel-containing lithium transition metal oxide in the positive active material, the influence of the mole ratio of the element nickel in the nickel-containing lithium transition metal oxide to the elements nickel, cobalt and manganese on the positive electrode sheet and the battery performance is investigated.

[0161] In Examples 2 to 6, different nickel-containing lithium transition metal oxides from Example 1 are used. In order to reduce the safety risk, the thickness of the shell of the battery monomer is adjusted accordingly. The specific adjustment data are shown in Table 3. The contents not listed in Table 3 indicate that each example has the same settings as Example 1. In addition, the test results of the performance parameters of the positive electrode sheet and the battery monomer of Examples 1 to 6 are shown in Table 3.

[0162] The adjustment of the shell size parameter only affects part of the properties of the battery monomer and has no effect on the performance of the positive electrode sheet. For the examples in Table 3, the higher the molar proportion of the nickel element in the nickel-cobalt-manganese-containing lithium transition metal oxide, the greater the discharge gram capacity and energy density of the positive electrode sheet, and the fewer the cycle numbers of the battery monomer.

[0163] The energy density of the battery monomer needs to take the shell thickness into account. Taking Examples 3 and 6 as examples, even a relatively thin shell can be used to achieve a battery monomer with high volumetric energy density, such as the positive electrode active material in Example 6, which has a lower molar content of Ni element than Example 3, and the energy density of the positive electrode sheet is smaller than that of Example 3, but because the first side wall thickness of the shell is thinner, the volumetric energy density of the battery monomer is higher than that of Example 3.

[0164] The shell with a first side wall thickness of 0.4 mm or 0.1 mm in Tables 3 and 4 is a stainless steel shell to enhance the strength of the shell.

[0165] Table 3

[0166] Table 4

[0167] Further, the positive electrode active material compositions of Examples 7 and 8 are set to be the same as Example 5, i.e., the mass ratio of the nickel-containing lithium transition metal oxide Li(Ni 0.8 Co 0.1 Mn 0.1 )O2 to the lithium-containing phosphate Li(Fe 0.5 Mn 0.5 )PO4 is 3:7, and the rest of the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte are also set the same as Example 5, and only the size of the first side wall of the shell is changed. The specific settings and test results are shown in Table 4, which more clearly illustrates the effect of the increase in the thickness of the first side wall on the energy density of the battery monomer.

[0168] The lithium-containing phosphate has good cycle stability, and the nickel-containing lithium transition metal oxide can provide a higher discharge gram capacity. The use of the two types of positive electrode active materials can fully exploit the advantages of both. To investigate the effect of the change in the mass content of the lithium-containing phosphate in the positive electrode active material, based on the settings of Example 1, the mass content of the lithium-containing phosphate Li(Fe 0.5 Mn 0.5 )PO4 and the nickel-containing lithium transition metal oxide Li(Ni 0.9 Co 0.05 Mn 0.05The rest of the positive electrode tab, the negative electrode tab, the separator, the electrolyte, and the battery cell shell are the same as those in Example 1.

[0169] The variable settings and performance test results are listed in Table 5.

[0170] Table 5

[0171] According to the data in Table 5, it can be found by comparing Comparative Example 3 with each of the examples that, under the premise that other conditions remain the same, the energy density and cycle performance of the battery cell are superior to those of the battery cell using only lithium-containing phosphates as the positive active material, when the lithium-containing transition metal oxide containing nickel and the lithium-containing phosphate are mixed in a certain ratio as the positive active material. When the mass content of the lithium-containing phosphate in the positive active material is in the range of 50% to 90%, the energy density and cycle life of the battery cell can be relatively balanced, and when the mass content is in the range of 50% to 70%, the discharge capacity of the positive electrode tab can be maintained at above 160 mAh / g, the volume energy density of the battery cell can be maintained at above 450 Wh / L, and the cycle number can be maintained at above 1700 cycles, and the battery cell obtains more excellent comprehensive performance.

[0172] Further, the influence of the molar ratio of Mn element in the lithium-containing phosphate to the Mn element and Fe element on the performance of the positive electrode tab and the battery cell is investigated. For this purpose, based on Example 1, the composition of the lithium-containing phosphate in the positive active material of Examples 14 to 17 is adjusted, the mass content of the lithium-containing phosphate in the positive active material is 70%, the lithium-containing transition metal oxide Li(Ni 0.9 Co 0.05 Mn 0.05 The rest of the positive electrode tab, the negative electrode tab, the separator, the electrolyte, and the battery cell shell are the same as those in Example 1. The variable settings and performance test results are listed in Table 6.

[0173] Table 6

[0174] Comparing the performance of each example in Table 6 can be seen: when the molar amount of Mn element in the lithium-containing phosphate is 20% to 80% of the total molar amount of Mn element and Fe element, a positive electrode sheet discharge gram capacity greater than 145 mAh / g can be obtained, but when the content of Mn element is 80%, not only does the volume energy density of the battery monomer decrease significantly, but the cycle performance also deteriorates due to serious Mn element dissolution. When the molar amount of Mn element in the lithium-containing phosphate is 30% to 70% of the total molar amount of Mn element and Fe element, the energy density of the positive electrode sheet and the battery monomer both increase, and when the molar proportion of Mn element is 50% to 70%, the positive electrode sheet discharge gram capacity and the energy density of the battery monomer are both further improved.

[0175] The positive electrode current collector plays a role of carrying active material, collecting and outputting current in the electrode sheet, and is very important for maintaining structural stability. At the same time, reducing the thickness and mass of the positive electrode current collector as much as possible is beneficial to the lightweight of the battery monomer and the improvement of the energy density of the battery monomer. The following example settings aim to investigate the influence of the mass ratio of single-layer positive electrode active layer to current collector on the performance of the battery monomer. Examples 18 to 20 adjust the mass of the current collector on the basis of Example 5, the rest of the positive electrode sheet, the negative electrode sheet, the separator, the electrolyte, and the shell are set the same as in Example 5. The specific settings and test results are shown in Table 7, and Ma / Mc in Table 7 represents the mass ratio of single-layer positive electrode active layer to positive electrode current collector.

[0176] Table 7

[0177] Because the mass of the positive electrode active material in each example is the same, if the mass ratio of single-layer positive electrode active layer to positive electrode current collector Ma / Mc is greater, it means that the coating amount of positive electrode active material relative to the positive electrode current collector is greater. From the data in Table 7, it can be seen that the mass ratio of single-layer positive electrode active layer to positive electrode current collector Ma / Mc is positively correlated with the volume energy density of the battery monomer and negatively correlated with the cycle performance.

[0178] By adjusting the graphite particle size in the two negative electrode active layers, the influence of the particle size of the negative electrode active particles on the performance of the battery monomer is investigated. The adjustment of the graphite particle size of the first and second negative electrode active layers in Examples 21 and 22 is shown in Table 8, and the rest of the negative electrode sheet, the positive electrode sheet, the separator, the electrolyte, and the shell are set the same as in Example 1.

[0179] Table 8

[0180] The first negative electrode active layer is arranged close to the negative electrode current collector, and the graphite particles with large particle size can make the contact area between the graphite particles and the electrolyte smaller, and the negative electrode structure has higher stability, which is beneficial to improve the cycle life.

[0181] The selection of the liquid injection coefficient is related to the degree of electrode plate immersion and the internal pressure of the battery monomer, and is closely related to the size and structural stability of the internal resistance of the battery monomer. In order to investigate the influence of the change of the liquid injection coefficient on the performance of the battery monomer, the liquid injection coefficients of examples 23 to 26 are set differently, and the settings of the positive electrode plate, the negative electrode plate, the separator, the electrolyte composition, and the battery shell are consistent with example 1.

[0182] The specific variable settings and battery monomer performance test results are listed in table 9.

[0183] Table 9

[0184] From the data in table 9, it can be seen that the liquid injection coefficient mainly affects the cycle performance of the battery monomer, and a moderate liquid injection coefficient can fully soak the electrode plate, which is beneficial to improve the kinetics of active ions, and is not easy to have too much free electrolyte, which aggravates the degree of side reaction.

[0185] In summary, through the multidirectional design of the battery monomer, especially the adjustment and exploration of the positive electrode active material, a battery monomer with high energy density and cycle stability can be obtained, and the safety of the battery monomer is also strengthened.

[0186] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the present application, and equivalent components can be substituted therefor. In particular, the technical features mentioned in each embodiment can be combined in any way as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising a housing and an electrode assembly located inside the housing, the electrode assembly comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, wherein, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer includes a negative electrode active material, which includes graphite. The positive electrode includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer includes a positive active material, which includes a nickel-containing lithium transition metal oxide and a lithium phosphate. The battery cell is configured to have a discharge capacity of 145 mAh / g-210 mAh / g when discharged from 4.3V to 2.5V at a rate of 0.33C. The housing has two first sidewalls parallel to a first direction and two second sidewalls parallel to a second direction, the first direction and the second direction being perpendicular, the area of ​​the first sidewall being larger than the area of ​​the second sidewall, and the thickness of the first sidewall being 0.1mm-0.8mm.

2. The battery cell according to claim 1, wherein, The battery cell is configured to have a discharge capacity of 150mAh / g-195mAh / g when discharging from 4.3V to 2.5V at a rate of 0.33C.

3. The battery cell according to claim 1 or 2, wherein, In the positive electrode active material, the mass content of lithium phosphate is 50%-90%, and optionally, the mass content of lithium phosphate is 50%-70%.

4. The battery cell according to any one of claims 1 to 3, wherein, The nickel-containing lithium transition metal oxide includes manganese and cobalt elements. In the nickel-containing lithium transition metal oxide, the molar amount of nickel accounts for 50%-95% of the total molar amount of nickel, cobalt and manganese elements, optionally 70%-95%, and further optionally 80%-95%.

5. The battery cell according to any one of claims 1 to 4, wherein, The thickness of the first sidewall is 0.4mm-0.8mm, and can be selected as 0.6mm-0.8mm.

6. The battery cell according to any one of claims 1 to 5, wherein, The nickel-containing lithium transition metal oxide includes lithium-containing nickel-cobalt-manganese oxide, which includes one or more of the elements Zr, Al, B, Fe, Ca, Sr, Ti, V, or Y.

7. The battery cell according to any one of claims 1 to 6, wherein, The lithium-containing nickel-cobalt-manganese oxide includes one or more of Zr, Al, or B; optionally, in the lithium-containing nickel-cobalt-manganese oxide, the mass content of the element satisfies at least one condition: the content of Zr is 1000ppm-300ppm, the content of Al is 100ppm-1000ppm, and the content of B is 50ppm-300ppm.

8. The battery cell according to any one of claims 1 to 7, wherein, The lithium-containing phosphate includes Mn and Fe elements, and the molar amount of Mn in the lithium-containing phosphate accounts for 20%-80% of the total molar amount of Mn and Fe elements, optionally 30%-70%, and further optionally 50%-70%.

9. The battery cell according to any one of claims 1 to 8, wherein, The lithium-containing phosphate includes lithium manganese iron phosphate, which includes one or more of the elements Al, B, Ca, Cr, Cu, K, Mg, Na, P, Si, Ti, V or Zn. Optionally, the lithium manganese iron phosphate includes one or more of the elements Al, Ca, Na, Ti, or V; Further optionally, in the lithium manganese iron phosphate, the mass content of the element satisfies at least one of the following: Al mass content 100ppm to 1000ppm, Ca mass content 50ppm to 300ppm, Na mass content 50ppm to 300ppm, Ti mass content 100ppm to 1000ppm, and V mass content 1000ppm to 3000ppm.

10. The battery cell according to any one of claims 1 to 9, wherein, The positive electrode active layer contains lithium manganese iron phosphate and lithium-containing nickel cobalt manganese oxide. The positive electrode active material contains one or more of the elements Al, B, Ca, Na, Sr, Ti, V, Y, or Zr, and based on the total mass of the positive electrode active material, the mass content of each element satisfies the following: Al:0.005％-0.1％； Ca: 0.0001%-0.02%; Na: 0.005%-0.06%; Ti: 0.005%-0.15%; V:0.0001％-0.3％； Zr:0.005％-0.2％； B:0.01％-0.1％。 11. The battery cell according to any one of claims 1 to 10, wherein, The thickness of the second sidewall is 0.8mm-1.2mm, and the thickness of the bottom wall of the shell is 1mm-1.5mm.

12. The battery cell according to any one of claims 1 to 11, wherein, The positive electrode active layer includes a first positive electrode active layer and a second positive electrode active layer. The first positive electrode active layer is disposed close to the positive electrode current collector, and the second positive electrode active layer is disposed on the side of the first positive electrode active layer away from the positive electrode current collector. The nickel-containing lithium transition metal oxide and the lithium-containing phosphate are each independently disposed in the first positive electrode active layer and / or the second positive electrode active layer.

13. The battery cell according to any one of claims 1 to 12, wherein, The ratio of the mass of the positive electrode active layer per unit area to the mass of the positive electrode current collector is (0.15-10):1, and can be selected as (4.5-5.6):

1.

14. The battery cell according to any one of claims 1 to 13, wherein, The negative electrode active layer includes a first negative electrode active layer and a second negative electrode active layer. The first negative electrode active layer is disposed close to the negative electrode current collector, and the second negative electrode active layer is disposed on the side of the first negative electrode active layer away from the negative electrode current collector. The average particle size of the graphite particles disposed in the first negative electrode active layer is larger than the average particle size of the graphite particles disposed in the second negative electrode active layer. Optionally, the graphite particles disposed in the first negative electrode active layer have an average particle size of 12μm-25μm, and the graphite particles disposed in the second negative electrode active layer have an average particle size of 5μm-12μm.

15. The battery cell according to any one of claims 1 to 14, wherein, An explosion-proof valve is provided on the second side wall of the housing. The area of ​​the explosion-proof valve is 8%-20% of the area of ​​the second side wall, and can be selected as 12%-16%.

16. The battery cell according to any one of claims 1 to 15, wherein, The battery cell includes at least one top cover assembly, which is welded to the first sidewall and the second sidewall; each top cover assembly includes a positive terminal and a negative terminal, and the electrode assembly includes stacked positive and negative electrode tabs, wherein the positive electrode tab is welded to the positive terminal, and the negative electrode tab is welded to the negative terminal. The solder area between the positive electrode tab and the individual positive terminal is set to 0.5 mm. 2 / Ah-1mm 2 / Ah, and / or, the solder area between the negative electrode tab and a single negative terminal is set to 0.5 mm. 2 / Ah-1mm 2 / Ah.

17. The battery cell according to any one of claims 1 to 16, wherein, The electrolyte injection coefficient of the battery cell is 1.8g / Ah-3.5g / Ah, and can be selected as 1.9g / Ah-3.1g / Ah.

18. A battery device comprising a battery cell, the battery cell comprising any one of claims 1 to 17, the battery device comprising a battery module, a battery pack, or an energy storage device.

19. An electrical device comprising a battery cell according to any one of claims 1 to 17, or a battery device according to claim 18.

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