Battery monomer, battery device and electric equipment

Abstract

The invention discloses a battery monomer, a battery device and electric equipment, and belongs to the technical field of batteries. The battery monomer comprises a positive pole piece, the positive pole piece comprises a positive active material, and the positive active material comprises lithium-containing phosphate and lithium-containing transition metal oxide; the electrolyte comprises a carboxylic ester solvent, and based on the total mass of the electrolyte, the mass content A of the carboxylic ester solvent meets the condition that A is larger than or equal to 20 wt% and smaller than or equal to 80 wt%. The battery monomer provided by the invention has relatively high energy density, relatively high reliability and relatively good dynamic performance.

Description

Technical Field

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

[0002] As environmental pollution becomes increasingly serious, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor related to its development.

[0003] The development of battery technology needs to consider many design factors, such as energy density, cycle life, capacity, reliability, etc. How to provide a battery cell that takes into account energy density, reliability and dynamic performance is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery device, and an electrical equipment, wherein the battery cell has high energy density, high reliability and good dynamic performance.

[0005] In a first aspect, a battery cell is provided, the battery cell comprising: a positive electrode plate, the positive electrode plate comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate and a lithium-containing transition metal oxide; an electrolyte, the electrolyte comprising a carboxylate solvent, and based on the total mass of the electrolyte, the mass content A of the carboxylate solvent satisfies: 20wt%≤A≤80wt%.

[0006] In the embodiment of the present application, by using lithium-containing phosphate and lithium-containing transition metal oxide as positive electrode active materials, the battery cell has both high energy density and high reliability. The electrolyte of the battery cell includes a carboxylic acid ester solvent, and the mass content A of the carboxylic acid ester solvent satisfies: 20wt%≤A≤80wt%, which can improve the dynamic performance of the battery cell, so the battery cell of the embodiment of the present application has high energy density, high reliability and good dynamic performance.

[0007] In some embodiments, the battery cell includes a shell having a wall portion, the wall portion is provided with a pressure relief mechanism, the pressure relief mechanism is provided with a pressure relief notch, the pressure relief notch defines a pressure relief area, and the pressure relief area is provided with a reinforcement structure.

[0008] In the above technical solution, when the battery cell thermally runs away, the pressure relief notch cracks, so that the pressure relief mechanism forms an opening for the discharge in the battery cell to pass smoothly; the pressure relief area defined by the pressure relief notch is provided with a reinforcement structure, which can reduce the risk of the pressure relief notch cracking of the battery cell during normal use and increase the service life of the battery cell.

[0009] In some embodiments, the reinforcement structure includes a reinforcement score, and the thickness of the pressure relief mechanism at the reinforcement score is greater than the thickness of the pressure relief mechanism at the pressure relief score.

[0010] In the above technical solution, the reinforced notch can increase the overall strength of the pressure relief mechanism, reduce the risk of the pressure relief mechanism opening during normal use of the battery cell, and increase the service life of the battery cell; in addition, when the battery cell undergoes thermal runaway pressure relief, the pressure relief notch will crack before the reinforced notch. The reinforced notch can reduce the risk of the open part of the pressure relief notch being wrinkled, resulting in a small opening area and poor exhaust.

[0011] In some embodiments, the reinforcing notch extends along a first direction and connects the two ends of the pressure relief notch in the first direction, and the first direction is the width direction of the wall portion. In this way, the reinforcing notch can improve the overall strength of the pressure relief mechanism, reduce the risk of the pressure relief mechanism opening during normal use of the battery cell, and increase the service life of the battery cell; in addition, when the battery cell undergoes thermal runaway pressure relief, the pressure relief notch will crack before the reinforcing notch, and the reinforcing notch can reduce the risk of the opening area being too small and the exhaust being poor due to wrinkling of the opened part of the pressure relief notch.

[0012] In some embodiments, the reinforcement structure includes two or more reinforcement notches, and the two or more reinforcement notches are arranged at intervals along the second direction, and the second direction is the length direction of the wall portion. In this way, the pressure relief mechanism can be strengthened to a better extent, and the risk of premature pressure relief of the pressure relief mechanism can be reduced; the risk of poor exhaust caused by too small an opening of the pressure relief notch when the battery cell is in thermal runaway can also be reduced.

[0013] In some embodiments, along the second direction, the distance L1 between two adjacent reinforcing notches satisfies: 0.3 mm ≤ L1 ≤ 1.0 mm. In this way, the distance between two adjacent reinforcing notches has a suitable size, which can have a better reinforcing effect on the pressure relief mechanism.

[0014] In some embodiments, 0.5 mm ≤ L1 ≤ 0.8 mm. In this way, the distance between two adjacent reinforcement notches has a suitable size, which can have a better reinforcement effect on the pressure relief mechanism.

[0015] In some embodiments, along the second direction, the spacing L1 between adjacent reinforcing notches and the size L2 of the pressure relief notch satisfy: 0.2≤L1 / L2≤0.5. In this way, L1 / L2 has a suitable size, which can have a better reinforcing effect on the pressure relief mechanism.

[0016] In some embodiments, 0.25≤L1 / L2≤0.45. In this way, L1 / L2 has a suitable size, which can have a better strengthening effect on the pressure relief mechanism.

[0017] In some embodiments, the thickness T1 of the pressure relief mechanism at the reinforcing notch satisfies: 0.4mm≤T1≤0.6mm. Setting the thickness of the pressure relief mechanism at the reinforcing notch within a reasonable range can make the strength of the pressure relief mechanism at the reinforcing notch higher than that of the pressure relief mechanism at the pressure relief notch when the battery cell is depressurized, while the reinforcing notch is cracked later than the pressure relief notch, thereby reducing the risk of the opening area being too small and the exhaust being poor due to wrinkling of the opened part of the pressure relief mechanism.

[0018] In some embodiments, the thickness T2 of the pressure relief mechanism at the pressure relief notch satisfies: 0.3mm≤T2≤0.5mm. Setting the thickness of the pressure relief mechanism at the pressure relief notch within a reasonable range can make the pressure relief notch more likely to crack when the battery cell is depressurized, thereby allowing the battery cell to release pressure smoothly.

[0019] In some embodiments, the area S of the pressure relief area satisfies: 500mm 2 ≤S≤1000mm 2 , and / or, the capacity Q of the battery cell satisfies: 80Ah≤Q≤150Ah. In this way, the battery cell has a suitable capacity and the pressure relief area has a suitable area, which facilitates the smooth discharge of the emissions in the battery cell when the battery cell is in thermal runaway.

[0020] In some embodiments, 20 wt% ≤ A ≤ 50 wt%, and / or 500 mm 2 ≤S≤800mm 2 , and / or, 80Ah≤Q≤150Ah.

[0021] In the above technical solution, the mass content of the carboxylic acid ester solvent in the electrolyte has a suitable range, the area of ​​the pressure relief region has a suitable range, the capacity of the battery cell has a suitable range, and the battery cell has a relatively suitable capacity, high reliability and excellent dynamic performance.

[0022] In some embodiments, 50 wt% ≤ A ≤ 80 wt%, and / or 600 mm 2 ≤S≤1000mm 2 , and / or, 80Ah≤Q≤120Ah.

[0023] In the above technical solution, the mass content of the carboxylic acid ester solvent in the electrolyte has a suitable range, the area of ​​the pressure relief region has a suitable range, the capacity of the battery cell has a suitable range, and the battery cell has a relatively suitable capacity, high reliability and excellent dynamic performance.

[0024] In some embodiments, the lithium-containing phosphate comprises: LiFe a Mn b PO4, wherein a+b=1, 3:7≤a:b≤5:5. The lithium-containing phosphate satisfying the above chemical formula has high structural stability, and its application in battery cells is beneficial to improving the reliability of the battery cells.

[0025] In some embodiments, the lithium-containing transition metal oxide comprises: Li 1+c [Ni x Co y Mn z M d ]O 2-e ; Wherein, M includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.2≥c≥-0.2, 0.95≥x≥0.5, 0.2≥y≥0.05, 0.3>z>0, 0.3>d≥0, 0.5≥e≥0. The lithium-containing transition metal oxide satisfying the above chemical formula has a high gram capacity, and its application in battery cells is beneficial to improving the energy density of battery cells.

[0026] In some embodiments, based on the total mass of the positive electrode active material, the mass content C of the lithium-containing phosphate satisfies: 40wt%≤C<100wt%. In this way, the mass content of the lithium-containing phosphate is within a suitable range, and the battery cell has higher reliability.

[0027] In some embodiments, 45 wt % ≤ C ≤ 70 wt %. In this way, both the lithium-containing phosphate and the lithium-containing transition metal oxide have relatively suitable mass contents, and the battery cell has higher reliability and higher energy density.

[0028] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes the positive electrode active material, and the positive electrode current collector includes an aluminum foil, and the thickness of the aluminum foil is 10 μm to 13 μm. In this way, by controlling the thickness of the positive electrode current collector within a suitable range, it is helpful to reduce the thickness of the positive electrode sheet and help improve the energy density of the battery cell.

[0029] In some embodiments, the positive electrode sheet further includes a conductive agent, and the conductive agent includes carbon nanotubes. Thus, by selecting carbon nanotubes as the conductive agent, a linear conductive network between the conductive agent and the positive electrode active material can be constructed, thereby helping to improve the rate performance and cycle performance of the battery cell.

[0030] In some embodiments, the surface density of the positive electrode sheet is 190 g / m 2~230g / m 2 , and / or, the compaction density of the positive electrode sheet is 2.5g / cm 3 ~2.9g / cm 3 .

[0031] In the above technical scheme, by controlling the surface density of the positive electrode plate within a suitable range, the energy density of the battery cell can be improved; by controlling the compaction density of the positive electrode plate within a suitable range, it helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell during the cycle process and helping to improve the cycle performance of the battery cell.

[0032] In some embodiments, the compaction density of the positive electrode sheet is 2.8 g / cm 3 ~2.9g / cm 3 In this way, the compaction density of the positive electrode sheet is within a suitable range, which helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell during the cycle process and helping to improve the cycle performance of the battery cell.

[0033] In some embodiments, the housing has a second wall, and the second wall is provided with an electrode terminal; the battery cell includes an electrode assembly, and the electrode assembly includes a main body and a pole ear, and the pole ear is connected to one end of the main body facing the second wall; the battery cell includes a connecting member, and the connecting member is arranged between the second wall and the main body, and the connecting member includes a first connecting part and a second connecting part connected to each other, the first connecting part is connected to the electrode terminal, and the second connecting part is connected to the pole ear; wherein, along the thickness direction of the second wall, the thickness D1 of the first connecting part and the thickness D2 of the second connecting part satisfy: D1-D2≥0.1mm.

[0034] In the above technical solution, by controlling the thickness of the second connection part to be smaller than the thickness of the first connection part, the thickness of the area where the connection member is connected to the electrode terminal is greater than the thickness of the area where the connection member is connected to the pole lug. Since the thickness requirement of the area where the connection member is connected to the pole lug is less than the thickness requirement of the area where the connection member is connected to the electrode terminal, the thickness of the connection member can be effectively optimized while realizing that the connection member can connect the electrode terminal and the pole lug, so as to reduce the overall weight of the connection member and save the space occupied by the connection member, thereby improving the energy density of the battery cell. In addition, by setting the thickness of the first connection part to be greater than or equal to 0.1 mm than the thickness of the second connection part, the thickness of the area where the connection member is used to connect to the pole lug can be further reduced, so as to further optimize the thickness of the connection member, reduce the overall weight of the connection member and save the space occupied by the connection member, which is conducive to further reducing the weight of the battery cell and improving the internal space utilization of the battery cell, so as to improve the energy density of the battery cell.

[0035] In some embodiments, the thickness D1 of the first connection portion satisfies: 0.5 mm ≤ D1 ≤ 1.2 mm, and the thickness D2 of the second connection portion satisfies: 0.3 mm ≤ D2 ≤ 1 mm.

[0036] In the above technical solution, the thickness of the first connection part and the thickness of the second connection part are both controlled within a suitable range, which can improve the energy density of the battery cell while satisfying the connection strength between the first connection part and the electrode terminal and between the second connection part and the tab.

[0037] In some embodiments, the second wall includes a first through hole; the electrode terminal includes a main body and a step portion, at least a portion of the main body is passed through the first through hole, the step portion protrudes from the outer peripheral surface of the main body, and the step portion is located on the side of the second wall facing the outside of the battery cell; the battery cell includes a fixing member, and the fixing member includes a second through hole for the main body to pass through; in the thickness direction of the second wall, at least a portion of the fixing member is located between the second wall and the step portion and abuts against the step portion, the main body has a first end face facing the outside of the battery cell, and the fixing member has a second end face facing the outside of the battery cell, and the first end face exceeds the second end face.

[0038] In the above technical solution, in the thickness direction of the second wall, the surface of the battery cell that exceeds the maximum height of the outer surface of the second wall is the first end face. When electrode terminals of the same specification are used, the height of the battery cell that exceeds the second wall can be reduced accordingly, thereby increasing the proportion of the space inside the battery cell shell to the total space of the battery, thereby increasing the energy density of the battery.

[0039] In some embodiments, in the thickness direction of the second wall, a height difference D between the first end surface and the second end surface satisfies: 0.5 mm≤D≤1.5 mm.

[0040] In the above technical solution, by controlling the height difference between the first end face and the second end face in the thickness direction of the second wall within a suitable range, the battery energy density can be improved while ensuring that the connection stability between the first end face and the second end face is as good as possible.

[0041] In some embodiments, in the radial direction of the main body, a dimension W1 of the step portion protruding from the outer circumferential surface of the main body satisfies: 0.1 mm ≤ W1 ≤ 5 mm.

[0042] In the above technical solution, by controlling the size of the step portion protruding from the outer peripheral surface of the main body portion within a suitable range, it is beneficial to increase the contact area between the step portion and the fixing member, thereby facilitating the improvement of the connection strength between the step portion and the fixing member.

[0043] In some embodiments, the battery cell further includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, and the volume average particle size Dv50 of the graphite satisfies: 10μm≤Dv50≤14μm.

[0044] In the above technical solution, by controlling the average volume particle size of the negative electrode active material within a suitable range, it helps to improve the lithium ion kinetics and help improve the rate performance and cycle performance of the battery cell.

[0045] In some embodiments, the negative electrode current collector includes copper foil, and the thickness of the copper foil is 4 μm to 6 μm.

[0046] In the above technical solution, by controlling the thickness of the negative electrode current collector within a suitable range, it helps to reduce the thickness of the negative electrode plate and helps to improve the energy density of the battery cell.

[0047] In some embodiments, the surface density of the negative electrode sheet is 90 g / m 2 ~110g / m 2 , and / or, the compaction density of the negative electrode sheet is 1.3 g / cm 3 ~1.55g / cm 3 .

[0048] In the above technical scheme, by controlling the surface density of the negative electrode plate within a suitable range, the energy density of the battery cell can be improved; by controlling the compaction density of the negative electrode plate within a suitable range, it helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell during the cycle process and helping to improve the cycle performance of the battery cell.

[0049] In some embodiments, the compaction density of the negative electrode sheet is 1.4 g / cm 3 ~1.5g / cm 3 In this way, the compaction density of the negative electrode sheet is within a suitable range, which helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell during the cycle process and helping to improve the cycle performance of the battery cell.

[0050] In some embodiments, the ionic conductivity σ of the electrolyte satisfies: 8mS / cm≤σ≤14mS / cm.

[0051] In the above technical solution, selecting an electrolyte with higher ion conductivity helps to improve the lithium ion dynamics during the battery cell cycle process, thereby helping to improve the cycle performance of the battery cell.

[0052] In some embodiments, 9mS / cm≤σ≤13mS / cm. In this way, the electrolyte has a higher ion conductivity, which is beneficial to improving the cycle performance of the battery cell.

[0053] In some embodiments, the carboxylate solvent includes a compound of the structure shown in Formula I,

[0054]

[0055] Wherein, R1 and R2 each independently include at least one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

[0056] In some embodiments, the carboxylate solvent includes: one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl formate, propyl acetate, methyl acrylate or ethyl acrylate.

[0057] By selecting the above-mentioned carboxylic acid ester solvent, the electrolyte has a lower viscosity and a higher ion conductivity, which is beneficial to improving the fast charging performance of the lithium-ion battery monomer.

[0058] In some embodiments, the electrolyte includes an additive, and the additive includes at least one of FEC, PS, and VC; based on the total mass of the electrolyte, the mass content B of the additive satisfies: <B≤5wt%。

[0059] The above-mentioned additives help to form films at the positive and negative electrodes, can reduce the side reactions of carboxylic acid ester solvents at the positive and negative electrodes, and are beneficial to improving the cycle life of the battery monomer; in addition, setting the mass content of the additives within an appropriate range can take into account both the cycle life and fast charging performance of the battery monomer.

[0060] In some embodiments, 1wt%≤B≤3wt%. In this way, the mass content of the additive is within a suitable range, which can take into account both the cycle life and fast charging performance of the battery cell.

[0061] In a second aspect, a battery device is provided, comprising the battery cell in the first aspect and any possible embodiment thereof.

[0062] In a third aspect, an electrical device is provided, comprising the battery device in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0064] Figure 1 A schematic diagram of a battery cell according to an embodiment of the present application;

[0065] Figure 2 A schematic diagram of an end cap according to an embodiment of the present application;

[0066] Figure 3 A schematic diagram of a pressure relief mechanism according to an embodiment of the present application;

[0067] Figure 4 A schematic diagram of a pressure relief mechanism according to another embodiment of the present application;

[0068] Figure 5 for Figure 4 A top view of the pressure relief mechanism in FIG.

[0069] Figure 6 for Figure 5 The cross-section along the AA direction;

[0070] Figure 7 A schematic diagram of a pressure relief mechanism according to another embodiment of the present application;

[0071] Figure 8 A top view of a battery cell according to an embodiment of the present application;

[0072] Fig. 9 for Figure 8 The cross-section along the BB direction in ;

[0073] Fig.10 for Fig. 9 An enlarged schematic diagram of region C in FIG.

[0074] Fig.11 A schematic diagram of a connecting member according to an embodiment of the present application;

[0075] Fig.12 A top view of a connecting member according to an embodiment of the present application;

[0076] Fig.13 for Fig.12 The cross-section along the DD direction in ;

[0077] Fig.14 An exploded view of a portion of the structure of a battery cell according to an embodiment of the present application;

[0078] Fig.15 for Fig.14 A top view of a partial structure of a battery cell;

[0079] Fig.16 for Fig.15 A cross-sectional view along the EE direction in FIG.

[0080] Fig.17 for Fig.16 An enlarged schematic diagram of region F in FIG.

[0081] Fig.18 A schematic diagram of a battery device according to an embodiment of the present application;

[0082] Fig.19 A schematic diagram of an electrical device according to an embodiment of the present application.

[0083] Figure numerals: 1: vehicle; 30: battery device; 90: controller; 40: motor; 301: first housing; 302: second housing; 20: battery cell; 21: housing; 211: wall; 212: shell; 213: end cover; 2131: electrode terminal; 22: electrode assembly; 221: main body; 222: pole ear; 24: connecting member; 50: pressure relief mechanism; 501: pressure relief notch; 60: pressure relief area; 600: reinforcement structure; 601: reinforcement notch; 5011: first pressure relief notch; 5012: second pressure relief notch; 1001: first surface; 1002: second surface; 106: groove; 5011a: first arc segment; 5011b: second arc segment; 5011c: first arc segment a straight line segment; 5011d: a first connecting segment; 5011e: a second connecting segment; 5012a: a second straight line segment; 5012b: a third connecting segment; 5012c: a fourth connecting segment; 241: a first connecting portion; 242: a second connecting portion; 243: a bending portion; 26: a second insulating member; 261: a main body; 262: a first extending portion; 27: a sealing member; 1281: a first through hole; 25: a first insulating member; 125: a fixing member; 1251: a second through hole; 1252: a second end face; 1231: a main body; 1232: a step portion; 1282: a second groove; 2611: a third through hole; 1233: a limiting portion; 12311: a first end face; 12321: a third end face; 1234: a first groove. DETAILED DESCRIPTION

[0084] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0085] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0086] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0087] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0088] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0089] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0090] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0091] The term "multiple" as used in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).

[0092] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0093] In some embodiments, the battery cell in the embodiments of the present application may be a metal battery. Specifically, the metal battery may include a lithium metal secondary battery, which is not limited in the embodiments of the present application.

[0094] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in mixed connection through a busbar component.

[0095] In some embodiments, the battery device may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are accommodated in the case.

[0096] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0097] In some embodiments, the battery may be located in an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0098] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their generally accepted meanings in the art.

[0099] Where mentioned, "lithium-containing phosphate" refers to phosphates having an olivine structure such as lithium iron phosphate, lithium manganese iron phosphate, etc.

[0100] As mentioned, "lithium-containing transition metal oxides" refers to a class of oxides including lithium elements and transition metal elements. Structurally, it includes ternary materials with layered structures, LiCoO2, LiNiO2, etc., and also includes LiMn2O4 with spinel structure, etc. Ternary materials refer to lithium transition metal oxides including three different transition metal elements. It should be understood that trace amounts of other transition metal elements can also be doped in ternary materials, and it is generally believed that ternary materials doped with other transition metal elements are still ternary materials.

[0101] In recent years, secondary batteries have been widely used in power tools, electronic products, electric vehicles, aerospace and other fields due to their high energy density and long service life, and have achieved great development. Usually, the battery cell of a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charge and discharge process of the battery cell, the active ions are embedded and released back and forth between the positive electrode plate and the negative electrode plate. Among them, the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The separator is arranged between the positive electrode plate and the negative electrode plate, which allows the active ions to pass through while preventing the positive and negative electrodes from short-circuiting, so that the electrochemical reaction in the battery cell proceeds normally.

[0102] Improving the energy density of battery cells has always been a research focus in the battery field. Positive electrode active materials are one of the factors that directly affect the energy density of battery cells. Lithium-containing phosphates with good stability and lithium-containing transition metal oxides with high gram capacity are both commonly used positive electrode active materials, but the low gram capacity of lithium-containing phosphates is not conducive to improving the energy density of battery cells. Lithium-containing transition metal oxides are conducive to improving the energy density of battery cells, but their reliability is poor.

[0103] In some processing methods, lithium-containing phosphates and lithium-containing transition metal oxides are mixed in the hope of obtaining a battery cell that takes into account both reliability and high energy density. However, after mixing lithium-containing phosphates and lithium-containing transition metal oxides, although the reliability and energy density of the battery cell can be taken into account to a certain extent, the dynamic performance of the battery cell is poor.

[0104] In view of this, an embodiment of the present application provides a battery cell, wherein the positive electrode active material of the battery cell includes a lithium-containing phosphate and a lithium-containing transition metal oxide, the electrolyte in the battery cell includes a carboxylate solvent, and the mass content of the carboxylate solvent is controlled within a suitable range, so that the battery cell can have high energy density, high reliability and excellent dynamic performance.

[0105] [Battery Cell]

[0106] Figure 1 Schematic diagram of a battery cell according to an embodiment of the present application. The present application embodiment provides a battery cell, for example, Figure 1 As shown, the battery cell 20 includes a positive electrode sheet and an electrolyte.

[0107] The battery cell 20 may include an electrode assembly 22, which includes a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet. The electrode assembly 22 may be in a wound type or a laminated type.

[0108] The positive electrode sheet includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate and a lithium-containing transition metal oxide.

[0109] The electrolyte includes a carboxylate solvent, and based on the total mass of the electrolyte, the mass content A of the carboxylate solvent satisfies: 20wt%≤A≤80wt%.

[0110] A may be 20 wt%, 25 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 65 wt%, 70 wt%, 80 wt% or any value within the above range.

[0111] Carboxylic acid ester solvents have the characteristics of low viscosity and high ionic conductivity. Their application in electrolytes is beneficial to improving the dynamic properties of lithium-ion battery cells, such as fast charging performance.

[0112] By combining lithium-containing phosphate and lithium-containing transition metal oxide, the energy density and reliability of the battery cell can be taken into account. However, after adding lithium-containing phosphate, the dynamic performance of the battery cell is affected to a certain extent. Therefore, adding a suitable mass content of carboxylic acid ester solvent to the electrolyte can improve the dynamic performance of the battery cell 20.

[0113] In the embodiment of the present application, by using lithium-containing phosphate and lithium-containing transition metal oxide as positive electrode active materials, the battery cell 20 has both high energy density and high reliability. The electrolyte of the battery cell 20 includes a carboxylic acid ester solvent, and the mass content A of the carboxylic acid ester solvent satisfies: 20wt%≤A≤80wt%, which can improve the dynamic performance of the battery cell 20, so the battery cell 20 of the embodiment of the present application has high energy density, high reliability and good dynamic performance.

[0114] Figure 2 is a schematic diagram of an end cap according to an embodiment of the present application, Figure 3 This is a schematic diagram of a pressure relief mechanism according to an embodiment of the present application. It should be noted that: Figure 2 Only the approximate position of the pressure relief mechanism 50 is shown in FIG. 5 . The specific structure of the pressure relief mechanism 50 can be found in FIG. Figure 3 shown.

[0115] In some embodiments, for example, referring to Figures 1 to 3 As shown, the battery cell 20 includes a housing 21 having a wall portion 211 , the wall portion 211 is provided with a pressure relief mechanism 50 , the pressure relief mechanism 50 is provided with a pressure relief notch 501 , the pressure relief notch 501 defines a pressure relief area 60 , and the pressure relief area 60 is provided with a reinforcement structure 600 .

[0116] The outer shell 21 may include a shell 212 and an end cover 213. A accommodating cavity is formed inside the shell 212, and the accommodating cavity has an opening, that is, the shell 212 is a hollow structure with one end open. The end cover 213 covers the opening of the shell 212 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 22 and the electrolyte.

[0117] The wall portion 211 may be an end cover 213, or may be one of the multiple walls of the housing 212. For example, Figure 1 As shown, the wall portion 211 is the end cover 213 of the housing 21. In other embodiments, the wall portion 211 may also be the thickness direction of the housing 212 in the end cover 213 (for example Figure 1 A bottom wall arranged opposite to the end cover 213 in the X direction (in the X direction) or a side wall adjacent to and abutting against the end cover 213.

[0118] The shell 212 can be in various shapes, such as a cylinder, a cuboid, etc. The shape of the shell 212 can be determined according to the specific shape of the electrode assembly 22. For example, if the electrode assembly 22 is a cylindrical structure, the shell 212 can be a cylindrical structure; if the electrode assembly 22 is a cuboid structure, the shell 212 can be a cuboid structure. Of course, the end cap 213 can also be in various structures, such as a plate-like structure or a hollow structure with one end open. For example, in Figure 1 In the embodiment, the shell 212 is a rectangular parallelepiped structure. It should be understood that the shell 21 is not limited to the aforementioned structure, and the shell 21 may also be other structures. For example, the shell 21 includes a shell 212 and two end caps 213. The shell 212 is a hollow structure with two opposite openings. One end cap 213 is correspondingly covered at one opening of the shell 212 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 22 and the electrolyte.

[0119] The pressure relief mechanism 50 is used to discharge the internal gas of the battery cell 20 .

[0120] As an example, when the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, it is actuated to release the internal pressure or temperature. When the internal pressure or temperature of the battery cell 20 reaches a predetermined threshold, the pressure relief mechanism 50 performs an action or a weak structure provided in the pressure relief mechanism 50 is destroyed, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies according to different design requirements. The threshold may depend on one or more materials of the positive electrode sheet, the negative electrode sheet, the electrolyte and the separator in the battery cell 20.

[0121] The "actuation" mentioned in the embodiments of the present application refers to the pressure relief mechanism 50 being in action or activated to a certain state, so that the internal pressure and temperature of the battery cell 20 can be released. The action produced by the pressure relief mechanism 50 may include but is not limited to: the components in the pressure relief mechanism 50 move to form an exhaust channel, at least a part of the pressure relief mechanism 50 ruptures, breaks, is torn or opened, and so on. When the pressure relief mechanism 50 is actuated, the high-temperature and high-pressure substances inside the battery cell 20 will be discharged from the actuated part as emissions. In this way, the battery cell 20 can be depressurized and cooled under controllable pressure or temperature, thereby avoiding potential more serious accidents.

[0122] The emissions from the battery cells 20 mentioned in the embodiments of the present application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode sheets, fragments of separators, high-temperature and high-pressure gases produced by the reaction, flames, and the like.

[0123] The shape of the pressure relief mechanism 50 includes but is not limited to a circle, an ellipse, a polygon, a waist shape, etc. The shape of the pressure relief mechanism 50 can be a shape with a certain symmetry or an asymmetric shape.

[0124] The pressure relief score 501 may refer to a portion of the pressure relief mechanism 50 having a thickness and / or melting point lower than the thickness of other areas of the pressure relief mechanism 50 except the pressure relief score 501, such as a score groove or a pressure relief groove, that is, a groove is opened on the surface of the pressure relief mechanism 50, which is equivalent to thinning the thickness of the pressure relief mechanism 50 at the position where the pressure relief score 501 is set.

[0125] When the pressure relief mechanism 50 is activated, the pressure relief score 501 is broken open, so that the pressure relief mechanism 50 forms an opening for the exhaust in the battery cell 20 to pass smoothly. As an example, in the case of thermal runaway of the battery cell 20, the pressure relief score 501 is broken open to discharge the exhaust in the battery cell 20.

[0126] The pressure relief notch 501 can be formed by machining, etching, stamping, or the like.

[0127] The shape of the pressure relief notch 501 can be a straight line, a folded line, an arc line, or a combination thereof. For example, the shape of the pressure relief notch 501 is a circle; for another example, the shape of the pressure relief notch 501 is a combination of a straight line and an arc line.

[0128] The pressure relief notch 501 defines a pressure relief area 60. The number of the pressure relief areas 60 may be one or two or more. The pressure relief area 60 defined by the pressure relief notch 501 may have a closed structure or a semi-closed structure.

[0129] For example, Figure 3As shown, the shape of the pressure relief notch 501 is an oval circle, the number of the pressure relief areas 60 defined by the pressure relief notch 501 is 1, and the pressure relief area 60 is an oval circle.

[0130] Figure 4 is a schematic diagram of a pressure relief mechanism according to another embodiment of the present application. Figure 5 for Figure 4 A top view of the pressure relief mechanism in FIG. Figure 6 for Figure 5 The cross-section along the AA direction in . For example, Figures 4 to 6 As shown, the pressure relief notch 501 includes a first pressure relief notch 5011 and a second pressure relief notch 5012, the second pressure relief notch 5012 is a straight line, the first pressure relief notch 5011 is a combination of an arc and a straight line, and the second pressure relief notch 5012 connects two ends of the first pressure relief notch 5011 along the length direction of the wall portion 211. The first pressure relief notch 5011 and the second pressure relief notch 5012 define a pressure relief area 60, and the pressure relief mechanism 50 includes two pressure relief areas 60.

[0131] As an example, Figure 5 As shown, the first pressure relief notch 5011 includes a first arc segment 5011a, a second arc segment 5011b, a first straight segment 5011c, a first connecting segment 5011d, and a second connecting segment 5011e. The two ends of the first arc segment 5011a are respectively connected to the first straight segment 5011c and the first connecting segment 5011d, and the two ends of the second arc segment 5011b are respectively connected to the first connecting segment 5011d and the second connecting segment 5011e. The first straight segment 5011c, the first connecting segment 5011d, and the second connecting segment 5011e are all extended along the length direction of the wall portion 211. The second pressure relief notch 5012 includes a second straight segment 5012a, a third connecting segment 5012b and a fourth connecting segment 5012c, the second straight segment 5012a extends along the length direction of the wall portion 211, the third connecting segment 5012b and the fourth connecting segment 5012c extend along the width direction of the wall portion 211, and the two ends of the second straight segment 5012a are respectively connected to the third connecting segment 5012b and the fourth connecting segment 5012c; the first connecting segment 5011d is connected to the third connecting segment 5012b, and the second connecting segment 5011e is connected to the fourth connecting segment 5012c.

[0132] The pressure relief mechanism 50 has a first surface 1001 and a second surface 1002 which are arranged opposite to each other along its thickness direction. The first surface 1001 is provided with a groove 106 which is sunken toward the second surface 1002 . The pressure relief notch 501 is arranged on the bottom wall of the groove 106 .

[0133] The pressure relief area 60 is provided with a reinforcement structure 600. As an example, the reinforcement structure 600 is provided on the bottom wall of the groove 106, and the reinforcement structure 600 may be protruding relative to the bottom wall of the groove 106, or may be recessed relative to the bottom wall of the groove 106.

[0134] The reinforcement structure 600 can connect both ends of the pressure relief score 501 in any direction. As an example, the reinforcement structure 600 connects both ends of the pressure relief score 501 in the length direction of the wall portion 211. As another example, the reinforcement structure 600 connects both ends of the pressure relief score 501 in the width direction of the wall portion 211.

[0135] Carboxylic acid ester solvents are not resistant to oxidation and reduction, and side reactions occur in the battery cell 20, resulting in increased gas production in the battery cell 20, and the risk of premature activation of the pressure relief mechanism 50. By providing a reinforcement structure 600 in the pressure relief area 60, the structural strength of the pressure relief mechanism 50 can be improved, and the risk of premature activation of the pressure relief mechanism 50 during normal use of the battery cell 20 can be reduced, which is conducive to improving the service life of the battery cell 20.

[0136] In the above embodiment, when the pressure relief mechanism 50 is actuated, the pressure relief notch 501 is split open, thereby allowing the pressure relief mechanism 50 to form an opening for the discharge in the battery cell 20 to pass smoothly; the pressure relief area 60 defined by the pressure relief notch 501 is provided with a reinforcement structure 600, which can reduce the risk of the pressure relief notch 501 of the battery cell 20 splitting during normal use, thereby increasing the service life of the battery cell 20.

[0137] In some embodiments, reinforcement structure 600 includes reinforcement score 601 , and the thickness of pressure relief mechanism 50 at reinforcement score 601 is greater than the thickness of pressure relief mechanism 50 at pressure relief score 501 .

[0138] Reinforcement score 601 may extend in any direction and connect pressure relief score 501. As an example, reinforcement score 601 connects both ends of pressure relief score 501 in any direction.

[0139] The shape of the reinforcement notch 601 can be a straight line, an arc line or a curve line.

[0140] As an example, the shape of the reinforcement notch 601 is a straight line.

[0141] In the above embodiment, the reinforced notch 601 can increase the overall strength of the pressure relief mechanism 50, reduce the risk of the pressure relief mechanism 50 opening during normal use of the battery cell 20, and increase the service life of the battery cell 20; in addition, when the battery cell 20 experiences thermal runaway pressure relief, the pressure relief notch 501 will crack before the reinforced notch 601, and the reinforced notch 601 can reduce the risk of the opened part of the pressure relief notch 501 being wrinkled, resulting in an opening area that is too small and poor exhaust.

[0142] In some embodiments, the reinforcement notch 601 extends along a first direction and connects two ends of the pressure relief notch 501 in the first direction, and the first direction is the width direction of the wall portion 211. For example, Figure 1 As shown, the first direction is the Y direction.

[0143] In the above embodiment, the reinforced notch 601 can increase the overall strength of the pressure relief mechanism 50, reduce the risk of the pressure relief mechanism 50 opening during normal use of the battery cell 20, and increase the service life of the battery cell 20; in addition, when the battery cell 20 experiences thermal runaway pressure relief, the pressure relief notch 501 will crack before the reinforced notch 601, and the reinforced notch 601 can reduce the risk of the opened part of the pressure relief notch 501 being wrinkled, resulting in an opening area that is too small and poor exhaust.

[0144] Figure 7 This is a schematic diagram of a pressure relief mechanism of another embodiment of the present application. Figure 7 In the figure, the reinforcement structure 600 is not shown, and the second straight line segment 5012a in the second pressure relief notch 5012 extends along the width direction of the wall portion 211, and the reinforcement notch 601 extends along the second direction.

[0145] In some embodiments, the reinforcement structure 600 includes a reinforcement notch 601. As an example, the reinforcement notch 601 extends along the first direction and passes through the center position of the pressure relief mechanism 50 in the second direction.

[0146] In some embodiments, the reinforcement structure 600 includes two or more reinforcement notches 601 , and the two or more reinforcement notches 601 are spaced apart along the second direction, where the second direction is the length direction of the wall portion.

[0147] For example, Figure 6 As shown, the reinforcement structure 600 includes two reinforcement notches 601, which extend along a first direction and are spaced apart along a second direction. The first direction may be a Y direction, and the second direction may be a Z direction.

[0148] In the above embodiment, by providing two or more reinforcing notches 601, the pressure relief mechanism 50 can be better reinforced, reducing the risk of premature pressure relief of the pressure relief mechanism 50; it can also reduce the risk of poor exhaust caused by the opening of the pressure relief notch 501 being too small when the battery cell 20 thermally runs away.

[0149] In some embodiments, along the second direction, the distance L1 between two adjacent reinforcement notches 601 satisfies: 0.3 mm ≤ L1 ≤ 1.0 mm.

[0150] L1 can be 0.3 mm, 0.35 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm or any value within the above range.

[0151] When L1 is greater than or equal to 0.3 mm, there is a suitable spacing between adjacent reinforcement notches 601, which facilitates the processing of the reinforcement notches 601; when L1 is less than or equal to 1.0 mm, it can provide a better support effect for the pressure relief notch 501 and reduce the risk of premature actuation of the pressure relief mechanism 50.

[0152] In the above embodiment, 0.3 mm ≤ L1 ≤ 1.0 mm, and the distance between two adjacent reinforcement notches 601 is of a suitable size, which can have a better reinforcement effect on the pressure relief mechanism 50 .

[0153] In some embodiments, 0.5 mm ≤ L1 ≤ 0.8 mm. In this way, the distance between two adjacent reinforcement notches 601 is of a suitable size, which can have a better reinforcement effect on the pressure relief mechanism 50 .

[0154] In some embodiments, along the second direction, the spacing L1 between adjacent reinforcement notches 601 and the size L2 of the pressure relief notch 501 satisfy: 0.2≤L1 / L2≤0.5.

[0155] L1 / L2 can be 0.2, 0.3, 0.4, 0.5 or any value within the above range.

[0156] When L1 / L2 is greater than or equal to 0.2, there is a suitable spacing between adjacent reinforcement notches 601, which facilitates the processing of the reinforcement notches 601; when L1 / L2 is less than or equal to 0.5, it can provide a better support effect for the pressure relief notch 501, reducing the risk of premature actuation of the pressure relief mechanism 50.

[0157] In the above embodiment, 0.2≤L1 / L2≤0.5, L1 / L2 has a suitable size, which can have a better strengthening effect on the pressure relief mechanism 50.

[0158] In some embodiments, 0.25≤L1 / L2≤0.45. In this way, L1 / L2 has a suitable size, which can have a better strengthening effect on the pressure relief mechanism 50.

[0159] In some embodiments, the thickness T1 of the pressure relief mechanism 50 at the reinforced notch 601 satisfies: 0.4 mm≤T1≤0.6 mm.

[0160] T1 can be 0.4 mm, 0.5 mm, 0.55 mm, 0.6 mm or any value within the above range.

[0161] Setting the thickness of pressure relief mechanism 50 at reinforced notch 601 within a reasonable range can ensure that when battery cell 20 is depressurized, while reinforced notch 601 cracks later than pressure relief notch 501, the strength of pressure relief mechanism 50 at reinforced notch 601 is higher than that of pressure relief mechanism 50 at pressure relief notch 501, thereby reducing the risk of wrinkling of the opened portion of pressure relief mechanism 50, resulting in an opening area that is too small and poor exhaust.

[0162] In some embodiments, the thickness T2 of the pressure relief mechanism 50 at the pressure relief notch 501 satisfies: 0.3 mm ≤ T2 ≤ 0.5 mm.

[0163] T2 may be 0.3 mm, 0.4 mm, 0.5 mm, or any value within the above range.

[0164] By setting the thickness of the pressure relief mechanism 50 at the pressure relief notch 501 within a reasonable range, the pressure relief notch 501 can be more easily broken when the battery cell 20 is pressure relieved, thereby allowing the battery cell 20 to release pressure smoothly.

[0165] In some embodiments, the area S of the pressure relief region 60 satisfies: 500 mm 2 ≤S≤1000mm 2 , and / or, the capacity Q of the battery cell 20 satisfies: 80Ah≤Q≤150Ah.

[0166] S can be 500mm 2 、550mm 2 、600mm 2 、650mm 2 、700mm 2 , 800mm 2 , 900mm 2 , 1000mm 2 Or any value within the above range, Q can be 80Ah, 85Ah, 90Ah, 100Ah, 110Ah, 120Ah, 130Ah, 140Ah, 150Ah or any value within the above range.

[0167] Since the addition of carboxylic acid ester solvents will cause a large amount of gas to be produced in the battery cell 20, by setting the area S of the pressure relief region 60 within the above-mentioned range, the pressure relief region 60 has a larger pressure relief area, which is convenient for the discharge of emissions when the battery cell 20 thermally runs away; in addition, since the area of ​​the pressure relief region 60 is large, the strength of the pressure relief mechanism 50 can be improved by setting the reinforcement structure 600, thereby reducing the risk of valve opening during normal use of the battery cell 20 and increasing the service life of the battery cell 20.

[0168] The capacity of a battery cell may refer to the discharge capacity of the battery cell. Different battery cells 20 may have different capacities. As the capacity of a battery cell 20 increases, the amount of gas generated in the battery cell 20 also increases.

[0169] In the above embodiment, the battery cell 20 has a suitable capacity, and the pressure relief area 60 has a suitable area, so that the exhaust in the battery cell 20 can be discharged smoothly when the battery cell 20 is in thermal runaway.

[0170] In some embodiments, 20 wt% ≤ A ≤ 50 wt%, and / or 500 mm 2 ≤S≤800mm 2 , and / or, 80Ah≤Q≤150Ah.

[0171] As an example, 20wt%≤A≤50wt%, and 500mm 2 ≤S≤800mm 2 .

[0172] As an example, 20 wt % ≤ A ≤ 50 wt %, and 80 Ah ≤ Q ≤ 150 Ah.

[0173] As an example, 500mm 2 ≤S≤800mm 2 , and 80Ah≤Q≤150Ah.

[0174] As an example, 20wt%≤A≤50wt%, and 500mm 2 ≤S≤800mm 2 , and 80Ah≤Q≤150Ah.

[0175] As the mass content of the carboxylic acid ester solvent increases, the dynamic performance (such as fast charging performance) of the battery cell 20 gradually improves, but the gas generation in the battery cell 20 also gradually increases. By matching the above mass content of the carboxylic acid ester solvent and the area of ​​the pressure relief area 60 within the above range, the discharge of the exhaust is facilitated and the battery cell has a good fast charging performance.

[0176] As the capacity of the battery cell 20 increases, the gas generation in the battery cell 20 also increases. By matching the capacity within the above range and the area of ​​the pressure relief area 60 within the above range, the exhaust can be discharged smoothly.

[0177] In the above embodiments, the mass content of the carboxylic acid ester solvent in the electrolyte has a suitable range, the area of ​​the pressure relief region 60 has a suitable range, the capacity of the battery cell 20 has a suitable range, and the battery cell 20 has a relatively suitable capacity, high reliability and excellent dynamic performance.

[0178] In some embodiments, 50 wt% ≤ A ≤ 80 wt%, and / or 600 mm 2 ≤S≤1000mm 2 , and / or, 80Ah≤Q≤120Ah.

[0179] In the above embodiments, the mass content of the carboxylic acid ester solvent in the electrolyte has a suitable range, the area of ​​the pressure relief region 60 has a suitable range, the capacity of the battery cell 20 has a suitable range, and the battery cell 20 has a relatively suitable capacity, high reliability and excellent dynamic performance.

[0180] In some embodiments, the lithium-containing phosphate includes: LiFe a Mn b PO4, where a+b=1, 3:7≤a:b≤5:5.

[0181] Specifically, a:b can be one of 3:7, 4:6, and 5:5.

[0182] The lithium-containing phosphate satisfying the above chemical formula has high structural stability, and being applied to the battery cell 20 is beneficial to improving the reliability of the battery cell 20 .

[0183] In some embodiments, the lithium-containing transition metal oxide comprises: Li 1+c [Ni x Co y Mn z M d ]O 2-e ; wherein M includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.2≥c≥-0.2, 0.95≥x≥0.5, 0.2≥y≥0.05, 0.3>z>0, 0.3>d≥0, 0.5≥e≥0.

[0184] Wherein, x+y+z+d can be 1. Specifically, c can be 0.2, 0.1, 0, -0.1, -0.2 or any value within the above range, x can be 0.5, 0.65, 0.7, 0.9, 0.95 or any value within the above range, y can be 0.05, 0.1, 0.15, 0.2 or any value within the above range, z can be 0.1, 0.2, 0.29 or any value within the above range, d can be 0, 0.1, 0.2, 0.29 or any value within the above range, and e can be 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any value within the above range.

[0185] Some M elements can be doped into the lithium-containing transition metal oxide. The doping of M elements helps to improve the stability of the lithium-containing transition metal oxide, thereby helping to improve the cycle performance of the battery cell. In addition, by controlling the ratio of each metal element in the lithium-containing transition metal oxide within a suitable range, the battery cell has a suitable energy density.

[0186] The lithium-containing transition metal oxide satisfying the above chemical formula has a relatively high gram capacity, and its application in the battery cell 20 is beneficial to improving the energy density of the battery cell 20 .

[0187] In some embodiments, 0.2≥c≥-0.2, 0.7≥x≥0.65, 0.12≥y≥0.07, 0.3>z>0, 0.3>d≥0, 0.5≥e≥0. The lithium-containing transition metal oxide satisfying the above chemical formula has a high gram capacity, and its application in the battery cell 20 is beneficial to improving the energy density of the battery cell 20.

[0188] In some embodiments, based on the total mass of the positive electrode active material, the mass content C of the lithium phosphate satisfies: 40 wt % ≤ C < 100 wt %.

[0189] C can be 40wt%, 42wt%, 44wt%, 45wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, 62wt%, 64wt%, 66wt%, 68wt%, 70wt%, 80wt%, 85wt%, 90wt%, 95wt% or any value within the above range. The mass fraction of the lithium-containing transition metal oxide can be the difference between 100% and the mass content C of the lithium-containing phosphate.

[0190] In the above embodiment, the mass content of the lithium-containing phosphate is within a suitable range, and the battery cell 20 has a high reliability.

[0191] In some embodiments, 45 wt % ≤ C ≤ 70 wt %. In this way, the lithium-containing phosphate and the lithium-containing transition metal oxide both have relatively suitable mass contents, and the battery cell 20 has higher reliability and higher energy density.

[0192] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, and the positive electrode current collector includes aluminum foil, and the thickness of the aluminum foil is 10 μm to 13 μm.

[0193] The thickness of the aluminum foil can be 10μm, 10.2μm, 10.4μm, 10.6μm, 10.8μm, 11μm, 11.2μm, 11.4μm, 11.6μm, 11.8μm, 12μm, 12.2μm, 12.4μm, 12.6μm, 12.8μm, 13μm, or its value is within the range obtained by combining any two of the above values. The thinner the thickness of the current collector, the more conducive it is to reducing the thickness of the positive electrode sheet, thereby increasing the energy density of the battery cell. If the thickness of the current collector is too thin, it is not conducive to the mechanical strength of the electrode sheet and may break during the processing or use of the battery cell. This embodiment helps to improve the energy density of the battery cell by controlling the thickness of the positive electrode current collector within a suitable range.

[0194] In some embodiments, the positive electrode plate further includes a conductive agent, and the conductive agent includes carbon nanotubes.

[0195] Conductive agents have a direct impact on the internal resistance, rate performance, thermal stability, energy density, and cycle performance of battery cells. Compared with conductive agents such as conductive carbon black and Ketjen black, carbon nanotubes have linear contact with positive electrode active materials, can form a conductive network between positive electrode active materials, have high conductivity, can reduce polarization of battery cells during cycling, and improve rate performance and cycle performance of battery cells.

[0196] In the above embodiment, by selecting carbon nanotubes as the conductive agent, a linear conductive network between the conductive agent and the positive electrode active material can be constructed, thereby helping to improve the rate performance and cycle performance of the battery cell 20 .

[0197] In some embodiments, the carbon nanotubes are multi-walled carbon nanotubes, which have higher electrical conductivity than single-walled carbon nanotubes.

[0198] In some embodiments, the surface density of the positive electrode sheet is 190 g / m 2 ~230g / m 2 , and / or, the compaction density of the positive electrode sheet is 2.5g / cm 3 ~2.9g / cm 3 .

[0199] The surface density of the positive electrode can be 190g / m 2 , 195g / m 2 , 200g / m 2 , 205g / m 2 , 210g / m 2 , 215g / m 2 , 220g / m 2 , 225g / m 2 , 230g / m 2, or its value is within the range obtained by combining any two of the above values. The compaction density of the positive electrode sheet can be 2.5g / m 2 , 2.6g / cm 3 , 2.7g / cm 3 , 2.8g / cm 3 , 2.9g / cm 3 , or its value is within the range obtained by combining any two of the above values.

[0200] In the above embodiment, by controlling the surface density of the positive electrode sheet within a suitable range, the energy density of the battery cell 20 can be improved.

[0201] The greater the compaction density of the positive electrode film layer, the more conducive it is to improving the energy density of the battery cell. However, if the compaction density of the positive electrode film layer is too large, it may affect the infiltration of the electrolyte into the positive electrode active material, thereby affecting the lithium ion dynamics. In the above embodiment, by controlling the compaction density of the positive electrode sheet within a suitable range, it is helpful to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell 20 during the cycle process, and helping to improve the cycle performance of the battery cell 20.

[0202] In some embodiments, the compaction density of the positive electrode sheet is 2.8 g / cm 3 ~2.9g / cm 3 In this way, the compaction density of the positive electrode sheet is within a suitable range, which helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell 20 during the cycle process and helping to improve the cycle performance of the battery cell 20.

[0203] Figure 8 is a top view of a battery cell according to an embodiment of the present application. Fig. 9 for Figure 8 The cross-section along the BB direction in Fig.10 for Fig. 9 An enlarged schematic diagram of region C in FIG. Fig.11 is a schematic diagram of a connecting member according to an embodiment of the present application, Fig.12 is a top view of a connecting member according to an embodiment of the present application, Fig.13 for Fig.12 Cross-section along DD direction.

[0204] In some embodiments, for example, in combination Figures 8 to 13As shown, the shell 21 has a wall portion 211, and the wall portion 211 is provided with an electrode terminal 2131; the battery cell 20 includes an electrode assembly 22, and the electrode assembly 22 includes a main body 221 and a pole ear 222, and the pole ear 222 is connected to one end of the main body 221 facing the wall portion 211; the battery cell 20 includes a connecting member 24, and the connecting member 24 is arranged between the wall portion 211 and the main body 221, and the connecting member 24 includes a first connecting portion 241 and a second connecting portion 242 connected to each other, the first connecting portion 241 is connected to the electrode terminal 2131, and the second connecting portion 242 is connected to the pole ear 222; wherein, along the thickness direction of the wall portion 211, the thickness D1 of the first connecting portion 241 and the thickness D2 of the second connecting portion 242 satisfy: D1-D2≥0.1mm.

[0205] D1-D2 can be 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 1 mm or any value within the above range.

[0206] The main body 221 of the electrode assembly 22 is the main area where the electrode assembly 22 undergoes electrochemical reactions in the battery cell 20. The main body 221 is a layout formed by winding or stacking the area of ​​the positive electrode sheet coated with the positive electrode active material, the separator, and the area of ​​the negative electrode sheet coated with the negative electrode active material. The tab 222 is used to connect with the electrode terminal 2131 to achieve electrical connection between the electrode assembly 22 and the electrode terminal 2131. It should be noted that the tab 222 of the electrode assembly 22 is a component formed by stacking and connecting the areas on the positive electrode sheet that are not coated with the positive electrode active material or a component formed by stacking and connecting the areas on the negative electrode sheet that are not coated with the negative electrode active material. If the tab 222 is used to output the positive electrode of the electrode assembly 22, the tab 222 is a component formed by stacking and connecting the areas on the positive electrode sheet that are not coated with the positive electrode active material; if the tab 222 is used to output the negative electrode of the electrode assembly 22, the tab 222 is a component formed by stacking and connecting the areas on the negative electrode sheet that are not coated with the negative electrode active material. Exemplarily, the tab 222 is connected to one end of the main body 221 facing the end cover 213 in the thickness direction X of the end cover 213 .

[0207] The electrode assembly 22 contained in the housing 21 may be one or more. Figure 1 In the embodiment, the outer shell 21 of the battery cell 20 is provided with two electrode assemblies 22, and the two electrode assemblies 22 are stacked along the thickness direction thereof, that is, the two electrode assemblies 22 are stacked along the thickness direction of the battery cell 20. Of course, in other embodiments, the electrode assemblies 22 accommodated in the outer shell 21 can be one, three, four, five, six, seven or eight, etc.

[0208] The electrode terminal 2131 is a component for outputting or inputting electric energy to the battery cell 20. For example, the material of the electrode terminal 2131 can be various, for example, the material of the electrode terminal 2131 can be copper, iron, aluminum, steel, aluminum alloy, etc. The end of the electrode terminal 2131 facing the electrode assembly 22 is connected to the connecting member 24, and the end of the electrode terminal 2131 away from the electrode assembly 22 is used to connect to the busbar component to realize the input or output of electric energy of the battery cell 20.

[0209] exist Figure 8 In the embodiment, the battery cell 20 includes two electrode terminals 2131, and correspondingly, each electrode assembly 22 has two pole tabs 222, and the polarities of the two pole tabs 222 are opposite. The two electrode terminals 2131 are electrically connected to the two pole tabs 222 of the electrode assembly 22, respectively, to realize the input or output of the positive and negative electrodes of the battery cell 20.

[0210] The connecting member 24 serves to connect the electrode terminal 2131 and the pole ear 222 to achieve electrical connection between the electrode assembly 22 and the electrode terminal 2131. Exemplarily, the connecting member 24 may be made of a variety of materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The connection structure between the connecting member 24 and the electrode terminal 2131 may be of various types, such as welding, abutment or bonding, etc. Similarly, the connection structure between the connecting member 24 and the pole ear 222 may also be of various types, such as welding or abutment, etc. There are two electrode terminals 2131 and two connecting members 24, and the two connecting members 24 are arranged at intervals along the first direction Z. Each electrode terminal 2131 is connected to the electrode assembly 22 via a connecting member 24 to output the positive and negative electrodes of the battery cell 20. As shown in FIG. Fig.10 and Fig.11 As shown, the connecting member 24 may further include a bending portion 243 , and the first connecting portion 241 and the second connecting portion 242 are connected via the bending portion 243 .

[0211] In the above embodiment, by controlling the thickness of the second connecting portion 242 to be smaller than the thickness of the first connecting portion 241, the thickness of the area where the connecting member 24 is connected to the electrode terminal 2131 is greater than the thickness of the area where the connecting member 24 is connected to the pole lug 222. Since the thickness requirement of the area where the connecting member 24 is connected to the pole lug 222 is smaller than the thickness requirement of the area where the connecting member 24 is connected to the electrode terminal 2131, the thickness of the connecting member 24 can be effectively optimized while achieving the connection between the electrode terminal 2131 and the pole lug 222, so as to reduce the overall weight of the connecting member 24, save the space occupied by the connecting member 24, and improve the energy density of the battery cell 20. In addition, by setting the thickness of the first connecting portion 241 to be greater than or equal to 0.1 mm than the thickness of the second connecting portion 242, the thickness of the area of ​​the connecting member 24 used to connect to the pole ear 222 can be further reduced, so that the thickness of the connecting member 24 can be further optimized to reduce the overall weight of the connecting member 24 and save the space occupied by the connecting member 24, which is beneficial to further reduce the weight of the battery cell 20 and improve the internal space utilization of the battery cell 20, so as to improve the energy density of the battery cell 20.

[0212] In some embodiments, the thickness D1 of the first connection portion 241 satisfies: 0.5 mm ≤ D1 ≤ 1.2 mm, and the thickness D2 of the second connection portion 242 satisfies: 0.3 mm ≤ D2 ≤ 1 mm.

[0213] D1 can be 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.15mm, 1.2mm, or any combination thereof. D2 can be 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 0.95mm, 1mm, or any combination thereof.

[0214] In the above embodiment, the thickness of the first connection part 241 and the thickness of the second connection part 242 are both controlled within a suitable range, which can improve the energy density of the battery cell 20 while satisfying the connection strength between the first connection part 241 and the electrode terminal 2131 and between the second connection part 242 and the tab 222 .

[0215] Fig.14 This is an exploded view of a portion of the structure of a battery cell according to an embodiment of the present application. Fig.15 for Fig.14 A top view of the partial structure of the battery cell in FIG. Fig.16 for Fig.15 Cross-sectional view along EE direction, Fig.17 for Fig.16 An enlarged schematic diagram of area F in FIG.

[0216] In some embodiments, for example, in combination Figures 14 to 16 As shown, the wall portion 211 includes a first through hole 1281; the electrode terminal 2131 includes a main body portion 1231 and a step portion 1232, at least a portion of the main body portion 1231 is passed through the first through hole 1281, the step portion 1232 protrudes from the outer peripheral surface of the main body portion 1231, and the step portion 1232 is located on the side of the wall portion 211 facing the outside of the battery cell 20; the battery cell 20 includes a fixing member 125, and the fixing member 125 includes a second through hole 1251 for the main body portion 1231 to pass through; in the thickness direction of the wall portion 211, at least a portion of the fixing member 125 is located between the wall portion 211 and the step portion 1232 and abuts against the step portion 1232, the main body portion 1231 has a first end face 12311 facing the outside of the battery cell 20, the fixing member 125 has a second end face 1252 facing the outside of the battery cell 20, and the first end face 12311 exceeds the second end face 1252.

[0217] The outside of the battery cell 20 refers to the part outside the housing 21 of the battery cell 20. The first end face 12311 exceeds the second end face 1252, which means that, outside the battery cell 20, in the thickness direction of the wall portion 211, the second end face 1252 is located between the first end face 12311 and the outer surface of the wall portion 211. In other words, the surface farthest from the outer surface of the wall portion 211 is the first end face 12311 of the electrode terminal 2131.

[0218] The outer peripheral surface of the main body 1231 may refer to the outer peripheral surface of a cylinder, or may refer to the peripheral surface of a prism connecting the top surface and the bottom surface of the prism. Taking the main body 1231 as a quadrangular prism as an example, the main body 1231 includes a top surface, a bottom surface and four side surfaces, the four side surfaces are sequentially connected and arranged around the top surface, and the four side surfaces are respectively connected to the top surface and the bottom surface at both ends in the direction from the top surface to the bottom surface. The above four side surfaces refer to the outer peripheral surface of the main body 1231. In some embodiments, the first end surface 12311 is provided with a first groove 1234, and the side surface of the first groove 1234 may also be referred to as the outer peripheral surface of the main body 1231. In this embodiment, the main body 1231 is shaped like a "convex" character. In some embodiments, the step portion 1232 has a third end surface 12321 facing away from the wall portion 211.

[0219] The depth of the first groove 1234 is T, and T may be 0.1 mm to 5 mm.

[0220] The distance between the first groove 1234 and the outer circumference of the step portion 1232 is W2, and W2 may be 0.5 mm to 10 mm.

[0221] The outer contour of the fixing member 125 may include, but is not limited to, circular, elliptical, polygonal, semicircular, etc. The fixing member 125 is made of metal material, for example, aluminum, copper, iron, steel, alloy or composite metal. The step portion 1232 may be continuously distributed along the circumference of the main body portion 1231, that is, in a ring shape. It may also be arranged in segments along the circumference of the main body portion 1231, that is, divided into multiple parts, at least one part of which abuts against the fixing member 125. The first through hole 1281 and the second through hole 1251 may be light holes or segmented step holes. In the embodiment where the first through hole 1281 and the second through hole 1251 are step holes, the cross section of the step hole may include at least one straight line segment and / or at least one oblique line segment and / or at least one arc segment.

[0222] In the above embodiment, in the thickness direction of the wall portion 211, the surface of the battery cell 20 that exceeds the maximum height of the outer surface of the wall portion 211 is the first end face. When the electrode terminal 2131 of the same specification is used, the height of the battery cell 20 that exceeds the wall portion 211 can be reduced accordingly, thereby increasing the proportion of the space inside the outer shell 21 of the battery cell 20 to the total space of the battery, thereby increasing the energy density of the battery.

[0223] In some embodiments, the battery cell 20 may further include a first insulating member 25 and a second insulating member 26 to insulate and isolate the end cap 213 and the electrode terminal 2131. The battery cell 20 may further include a sealing member 27 to seal the gap between the electrode terminal 2131 and the hole wall of the first through hole 1281.

[0224] In some embodiments, the electrode terminal 2131 further includes a limiting portion 1233 , which protrudes from the outer circumferential surface of the main body 1231 and is located on the inner side of the wall 211 . The limiting portion 1233 is used to limit the movement of the electrode terminal 2131 to the outside of the shell 21 .

[0225] Exemplarily, the insulating member 26 includes a body 261 and a first extension portion 262, the body 261 is located between the fixing member 125 and the wall portion 211, the body 261 is provided with a third through hole 2611 through which the supply terminal 2131 passes, and the first extension portion 262 is located at the periphery of the fixing member 125 and is arranged around the edge of the body 261. The sealing member 27 is at least partially located between the wall portion 211 and the limiting portion 1233.

[0226] In some embodiments, a second groove 1282 is disposed on the outer surface of the wall portion 211 , and the body 261 is located in the second groove 1282 .

[0227] In some embodiments, in the thickness direction of the wall portion 211 , a height difference D between the first end surface 12311 and the second end surface 1252 satisfies: 0.5 mm≤D≤1.5 mm.

[0228] D can be 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm or any value within the above range.

[0229] In the above embodiment, by controlling the height difference between the first end face 12311 and the second end face 1252 in the thickness direction of the wall portion 211 within a suitable range, it is possible to improve the energy density of the battery while ensuring that the first end face 12311 and the second end face 1252 have better connection stability.

[0230] In some embodiments, the step portion 1232 has a thickness t, and t is 0.5 mm to 2.5 mm.

[0231] In some embodiments, in the radial direction of the main body 1231 , a dimension W1 of the step portion 1232 protruding from the outer circumferential surface of the main body 1231 satisfies: 0.1 mm≤W1≤5 mm.

[0232] W1 can be 0.1mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.4mm, 2.6mm, 2.8mm, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm, 4.2mm, 4.4mm, 4.6mm, 4.8mm, 5mm, or its value is within the range obtained by combining any two of the above values.

[0233] In the above embodiment, by controlling the size of the step portion 1232 protruding from the outer peripheral surface of the main body portion 1231 within an appropriate range, it is beneficial to increase the contact area between the step portion 1232 and the fixing member 125, thereby facilitating the improvement of the connection strength between the step portion 1232 and the fixing member 125.

[0234] In some embodiments, the battery cell 20 also includes a negative electrode plate, which includes a negative electrode collector and a negative electrode film layer arranged on at least one side of the negative electrode collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes graphite, and the volume average particle size Dv50 of the graphite satisfies: 10μm≤Dv50≤14μm.

[0235] Dv50 can be 10μm, 10.2μm, 10.4μm, 10.6μm, 10.8μm, 11μm, 11.2μm, 11.4μm, 11.6μm, 11.8μm, 12μm, 12.2μm, 12.4μm, 12.6μm, 12.8μm, 13μm, 13.2μm, 13.4μm, 13.6μm, 13.8μm, 14μm, or its value is within the range obtained by combining any two of the above values. The average volume particle size of the negative electrode active material affects the capacity and cycle performance of the battery cell. The smaller the average volume particle size of the negative electrode active material, the larger the specific surface area, which can provide more active sites in the electrochemical reaction, thereby facilitating the release and insertion of lithium ions and improving the capacity of the battery cell. If the average volume particle size of the negative electrode active material is too small, the contact area between the particles may be insufficient, the internal resistance of the battery cell may be increased, and the cycle performance of the battery cell may be affected. Therefore, this embodiment can help improve the capacity and cycle performance of the battery cell by controlling the average volume particle size of the negative electrode active material within a suitable range.

[0236] In some embodiments, the negative electrode current collector includes copper foil, and the thickness of the copper foil is 4 μm to 6 μm.

[0237] The thickness of the copper foil may be 4 μm, 4.2 μm, 4.6 μm, 5 μm, 5.2 μm, 5.5 μm, 6 μm, or a value within a range obtained by combining any two of the above values.

[0238] In the above embodiment, by controlling the thickness of the negative electrode current collector within a suitable range, it is helpful to reduce the thickness of the negative electrode plate and help improve the energy density of the battery cell 20 .

[0239] In some embodiments, the surface density of the negative electrode sheet is 90 g / m 2 ~110g / m 2 , and / or, the compaction density of the negative electrode sheet is 1.3g / cm 3 ~1.55g / cm 3 .

[0240] The surface density of the negative electrode sheet can be 90g / m 2 , 92g / m 2 , 94g / m 2 , 96g / m 2 , 98g / m 2 , 100g / m 2 , 102g / m 2 , 104g / m 2 , 106g / m 2 , 108g / m 2 , 110g / m 2, or its value is within the range obtained by combining any two of the above values.

[0241] The compaction density of the negative electrode sheet can be 1.3g / cm 3 , 1.32g / cm 3 , 1.34g / cm 3 , 1.35g / cm 3 , 1.36g / cm 3 , 1.38g / cm 3 , 1.4g / cm 3 , 1.42g / cm 3 , 1.44g / cm 3 , 1.46g / cm 3 , 1.48g / cm 3 , 1.5g / cm 3 , or its value is within the range obtained by combining any two of the above values.

[0242] In the above embodiments, by controlling the surface density of the negative electrode plate within a suitable range, the energy density of the battery cell 20 can be improved; by controlling the compaction density of the negative electrode plate within a suitable range, it helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell 20 during the cycle process, helping to improve the cycle performance of the battery cell 20.

[0243] In some embodiments, the compaction density of the negative electrode sheet is 1.4 g / cm 3 ~1.5g / cm 3 In this way, the compaction density of the negative electrode sheet is within a suitable range, which helps to improve the lithium ion dynamics, thereby reducing the polarization of the battery cell 20 during the cycle process and helping to improve the cycle performance of the battery cell 20.

[0244] In some embodiments, the ionic conductivity σ of the electrolyte satisfies: 8 mS / cm≤σ≤14 mS / cm.

[0245] Specifically, σ can be 8 mS / cm, 8.5 mS / cm, 9 mS / cm, 9.5 mS / cm, 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, or a value within the range obtained by combining any two of the above values.

[0246] In the above embodiment, selecting an electrolyte with higher ion conductivity helps to improve the lithium ion dynamics during the cycle of the battery cell 20 , thereby helping to improve the cycle performance of the battery cell 20 .

[0247] In some embodiments, 9 mS / cm≤σ≤13 mS / cm. In this way, the electrolyte has a relatively high ionic conductivity, which is beneficial to improving the cycle performance of the battery cell 20.

[0248] In some embodiments, the carboxylate solvent includes a compound of the structure shown in Formula I,

[0249]

[0250] Wherein, R1 and R2 each independently include at least one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

[0251] In some embodiments, the carboxylate solvent includes one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl formate, propyl acetate, methyl acrylate or ethyl acrylate.

[0252] By selecting the above-mentioned carboxylic acid ester solvent, the electrolyte has a lower viscosity and a higher ion conductivity, which is beneficial to improving the fast charging performance of the lithium-ion battery monomer.

[0253] In some embodiments, the electrolyte includes an additive, the additive includes at least one of fluoroethylene carbonate (FEC), propane sultone (PS, also referred to as 1,3-PS), and vinylene carbonate (VC); based on the total mass of the electrolyte, the mass content B of the additive satisfies: 0 <B≤5wt%。

[0254] B may be 0.05 wt%, 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or any value within the above range.

[0255] When B is greater than 0, the addition of additives helps to form films at the positive and negative electrodes, which can reduce the side reactions of carboxylic acid ester solvents at the positive and negative electrodes, and is beneficial to improving the cycle life of the battery cell 20; when B is less than or equal to 5wt%, the risk of increased impedance of the battery cell 20 due to excessive additive content can be reduced, and the battery cell has suitable fast charging performance.

[0256] The above-mentioned additives help to form a film at the positive electrode and the negative electrode, which can reduce the side reactions of carboxylic acid ester solvents at the positive electrode and the negative electrode, and is beneficial to improving the cycle life of the battery cell 20; in addition, setting the mass content of the additives within an appropriate range can take into account both the cycle life and fast charging performance of the battery cell 20.

[0257] In some embodiments, 1wt%≤B≤3wt%. In this way, the mass content of the additive is within a suitable range, which can take into account both the cycle life and the fast charging performance of the battery cell 20.

[0258] Next, taking a lithium-ion battery as a specific example, the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte in the battery cell 20 are described in detail.

[0259] [Negative electrode]

[0260] The negative electrode sheet generally includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material.

[0261] 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.

[0262] In one embodiment, 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.).

[0263] In one embodiment, the negative electrode active material may adopt the negative electrode active material for batteries 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.

[0264] In one embodiment, the negative electrode film layer further includes a binder. 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).

[0265] In one embodiment, the negative electrode film layer further includes a conductive agent, which can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0266] In one embodiment, the negative electrode film layer further includes other additives, such as a thickener (eg sodium carboxymethyl cellulose (CMC-Na)).

[0267] In one embodiment, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet are formed into a negative electrode slurry. For example, the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a negative electrode slurry. Then, the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0268] [Positive electrode]

[0269] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0270] 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.

[0271] In one embodiment, 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.).

[0272] In another embodiment, examples of lithium-containing transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and at least one of a composite material of lithium iron manganese phosphate and carbon. The battery is accompanied by the deintercalation and consumption of Li during the charging and discharging process, and the molar content of Li in the positive electrode active material is different when the battery is discharged to different states. In the enumeration of positive electrode active 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 active material is used in the battery system, and the molar content of Li will change after charge and discharge cycles. In the enumeration of positive electrode active materials in this application, the molar content of O is only an ideal state value. The release of lattice oxygen will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0273] The positive electrode active material includes Li 1+c [Ni x Co y Mn z M d ]O 2-e In the example, d is 0, and the positive electrode active material includes LiNi 0.7 Co 0.1 Mn 0.2 As another example, d>0, the positive electrode active material includes LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O2.

[0274] In one embodiment, the positive electrode active material includes: LiNi 0.90 Co 0.06 Mn 0.04 O2、LiNi 0.7 Co 0.1 Mn 0.2 O2、LiNi 0.7 Co 0.2 Mn 0.1 O2 or LiNi 0.8 Co 0.1 Mn 0.1 At least one of O2.

[0275] In one embodiment, the positive electrode film layer further includes 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.

[0276] In one embodiment, the positive electrode film layer further includes a conductive agent. As an example, the conductive agent may also include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, graphene and carbon nanofibers.

[0277] In one embodiment, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet are respectively formed into positive electrode slurries. For example, 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. Then, the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0278] [Electrolyte]

[0279] 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.

[0280] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent. Some solutions of the electrolyte solution have been mentioned above.

[0281] In addition to the aforementioned scheme, in some embodiments, the electrolyte salt can also 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.

[0282] In some embodiments, the solvent may also be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl 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, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0283] In some embodiments, the electrolyte may further include additives, such as 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.

[0284] [Isolator]

[0285] The present application has no particular limitation on the type of the separator. For example, any known porous structure separator with good chemical stability and mechanical stability may be selected.

[0286] In one embodiment, 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. When the isolation membrane is a multi-layer composite film, the isolation membrane of the present application may not contain a PVDF coating.

[0287] [Battery device]

[0288] The present application provides a battery device, including the battery cell in the above embodiment. The battery device can be a single physical module including one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in mixed connection through a busbar.

[0289] In some embodiments, the battery device may be a battery pack, wherein the battery includes a case and battery cells, and the battery cells or battery modules are accommodated in the case.

[0290] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0291] In some embodiments, the battery device may be located in an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0292] Fig.18 Schematic diagram of a battery according to an embodiment of the present application. Fig.18 As shown, the battery device 30 may include a plurality of battery cells 20 to meet different power requirements.

[0293] The battery device 30 may further include a box body, the interior of the box body is a hollow structure, and a plurality of battery cells 20 are accommodated in the box body. For example, a plurality of battery cells 20 are connected in parallel, in series, or in a mixed combination and placed in the box body. The box body may include a first box body portion 301 and a second box body portion 302, and the first box body portion 301 and the second box body portion 302 cover each other to form the box body. The shape of the first box body portion 301 and the second box body portion 302 can be determined according to the shape of the components accommodated inside, for example, it can be determined according to the shape of the combination of the plurality of battery cells 20 accommodated inside, and at least one of the first box body portion 301 and the second box body portion 302 has an opening. For example, as Fig.18 As shown, only one of the first box body 301 and the second box body 302 may be a hollow cuboid with an opening, while the other may be a plate-shaped to cover the opening. Taking the second box body 302 as a hollow cuboid with an opening and the first box body 301 as a plate-shaped example, the first box body 301 covers the opening of the second box body 302 to form a box with a closed chamber, which can be used to accommodate multiple battery cells 20.

[0294] In addition, the present application also provides an electrical device, which includes the secondary battery in the aforementioned embodiment.

[0295] For example, unlike Fig.18 As shown, the first box body 301 and the second box body 302 can both be hollow cuboids and each have an open face, the opening of the first box body 301 and the opening of the second box body 302 are arranged opposite to each other, and the first box body 301 and the second box body 302 are buckled together to form a box with a closed chamber, which can be used to accommodate multiple battery cells 20. Multiple battery cells 20 are connected in parallel, in series, or in a mixed combination and placed in the box formed by the first box body 301 and the second box body 302 buckled together.

[0296] In some embodiments, the battery device 30 may further include other components. For example, the battery device 30 may further include a busbar component, which may be used to achieve electrical connection between multiple battery cells 20, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component may achieve electrical connection between the battery cells 20 by connecting the electrode terminals of the battery cells 20; or, the busbar component may also achieve electrical connection between the battery cells 20 by connecting other components of the battery cells 20. The busbar component may be fixed to the corresponding components of the battery cell 20 by welding, for example, it may be fixed to the electrode terminals, the sealing structure, or the housing by welding, etc., but the embodiments of the present application are not limited thereto.

[0297] The battery cells 20 may directly form the battery device 30 , or may first form a battery module, and then a plurality of battery modules may form the battery device 30 .

[0298] [Electrical equipment]

[0299] An embodiment of the present application provides an electrical device, including the battery device described in the above embodiment.

[0300] Electrical equipment may be vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, electric tools, and the like. Vehicles may be fuel vehicles, gas vehicles, or new energy vehicles, and new energy vehicles may be pure electric vehicles, hybrid vehicles, or extended-range vehicles, and the like; spacecraft include airplanes, rockets, space shuttles, and spacecraft, and the like; electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like; electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical equipment.

[0301] Fig.19 Schematic diagram of an electrical device according to an embodiment of the present application. Fig.19 As shown, the present application provides an electrical device, which is a vehicle.

[0302] The vehicle 1 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 40, a controller 90 and a battery device 30 may be provided inside the vehicle 1. The controller 90 is used to control the battery device 30 to power the motor 40. For example, a battery device 30 may be provided at the bottom, front or rear of the vehicle 1. The battery device 30 may be used to power the vehicle 1. For example, the battery device 30 may be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery device 30 may not only be used as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0303] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0304] [Example]

[0305] Example 1

[0306] In Example 1, the positive electrode active material is a lithium-containing transition metal oxide LiNi 0.65 Co 0.15 Mn 0.2 O2 and LiMn containing lithium phosphate 0.6 Fe 0.4 O4, based on the total mass of the positive electrode active material, the mass of the lithium phosphate accounts for 50%. The electrolyte includes a carboxylic acid ester solvent, and the carboxylic acid ester solvent is ethyl acetate.

[0307] The pressure relief mechanism 50 is provided with reinforcement notches, the spacing L1 between two adjacent reinforcement notches is 0.3 mm, L1 / L2 is 0.2, and the area of ​​the pressure relief mechanism is 640 mm 2 The thickness T1 at the reinforcement notch is 0.5 mm, and the thickness T2 at the pressure relief notch is 0.4 mm.

[0308] Embodiment 2-4

[0309] The difference between Example 2-4 and Example 1 is that L1 is different, and accordingly, L1 / L2 is different.

[0310] Example 5

[0311] The difference between Example 5 and Example 1 is that no reinforcement notch is provided.

[0312] Comparative Example 1

[0313] The difference between Comparative Example 1 and Example 1 is that the electrolyte does not include a carboxylic acid ester solvent, and the pressure relief mechanism is not provided with a reinforced notch.

[0314] [Preparation of battery cells]

[0315] Preparation of positive electrode sheet: The positive electrode active material contains lithium phosphate LiMn 0.6 Fe 0.4 O4 and Li-containing layered metal oxides LiNi 0.65 Co 0.15 Mn 0.2 O2, binder polyvinylidene fluoride (PVDF), conductive agent acetylene black, and carbon nanotubes are mixed in a mass ratio of 96.5:2:1:0.5 (the mass ratio of lithium phosphate to lithium transition metal oxide is 5:5), NMP is added, and the mixture is stirred evenly in a blender. The slurry is then coated on a 12-micron thick aluminum foil, dried in an oven, cold pressed, and cut to obtain positive electrode sheets.

[0316] Preparation of negative electrode sheet: The negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in deionized water at a mass content ratio of 96.5:0.9:1.5:1.1, and the negative electrode slurry is prepared after being fully stirred and mixed; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain the negative electrode sheet. The surface density of the negative electrode sheet is 98g / m 2 .

[0317] Separator film: A polyethylene film with a thickness of 9 μm was used as the separator film.

[0318] Preparation of electrolyte: Ethylene carbonate (EC), ethyl acetate (EA) and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:2:5, and then LiPF6 was dissolved in the above solution to obtain an electrolyte, and the concentration of LiPF6 was 1 mol / L.

[0319] Preparation of battery cells: stack and wind the above-mentioned positive electrode sheets, separators, and negative electrode sheets in order to obtain an electrode assembly; place the electrode assembly in an outer package, add the above-prepared electrolyte, and obtain a battery cell after packaging, standing, formation, aging and other processes.

[0320] Table 1 shows the specific parameters and test results of the embodiments and comparative examples. Please refer to Table 1 for details.

[0321] Table 1 Specific parameters and test results of the embodiments and comparative examples

[0322]

[0323] As shown in Examples 1-5 and Comparative Example 1, by adding a carboxylic acid ester solvent into the electrolyte, the fast charging time of the battery monomer is shortened, and the battery monomer has better dynamic performance.

[0324] As shown in Embodiments 1-4 and Embodiment 5, providing the reinforcement notches is beneficial to improving the service life of the battery cells.

[0325] As shown in Examples 1-4, by properly setting L1 and L1 / L2, the battery cells have a longer service life.

[0326] [Battery cell parameter test method]

[0327] 1. Test of fast charging performance of battery cells

[0328] In the embodiment of the present application, the dynamic performance of the battery cell is reflected by the fast charging time. The shorter the charging time, the better the fast charging performance and the better the dynamic performance.

[0329] The battery cells of the above-mentioned embodiments and comparative examples were charged and discharged for the first time at a current of 1C (i.e., the current value at which the theoretical capacity is completely discharged within 1 hour), specifically comprising: at 35°C, the battery was charged at a constant current rate of 1C to a voltage of 4.25V, then charged at a constant voltage to a current ≤0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a voltage of 2.8V, and its actual capacity was recorded as C0. Then the battery is charged with a constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, and 5C0 in sequence to a charge cut-off voltage of 4.25V or a negative electrode cut-off potential of 0V (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to a full battery discharge cut-off voltage of 2.8V. Record the SOC (State of Charge) at different charge rates to 10%, 20%, 30%, ..., 80%. Charge, state of charge, when "SOC = 0" means the battery is fully discharged, when "SOC = 100%" means the battery is fully charged) the corresponding negative electrode potential, draw the charging rate-negative electrode potential curve under different SOC states, and obtain the charging rate corresponding to the negative electrode potential of 0V under different SOC states after linear fitting. The charging rate is the charging window under the SOC state, which is recorded as C10% SOC, C20% SOC, C30% SOC, C40% SOC, C50% SOC, C60% SOC, C70% SOC, C80% SOC, according to the formula (60 / C20% SOC+60 / C30% SOC+60 / C40% SOC+60 / C50% SOC+60 / C60% SOC+60 / C70% SOC+60 / C80% SOC)×10%, the charging time T of the battery from 10% SOC to 80% SOC is calculated in min. The shorter the time, the better the fast charging performance of the battery cell.

[0330] 2. Test of battery life

[0331] In the embodiment of the present application, the service life of the battery cell is reflected by testing the number of days the battery cell is stored at high temperature.

[0332] The high-temperature gas generation test process is as follows: the prepared battery cell is charged to 100% SOC at a rate of 0.1C, stored at 60°C, and the internal pressure of the battery is monitored online using a barometer. When the cut-off pressure is 0.35MPa, the number of days stored at 60°C is recorded.

[0333] 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, characterized in that: include: A positive electrode sheet, the positive electrode sheet comprising a positive electrode active material, the positive electrode active material comprising a lithium-containing phosphate and a lithium-containing transition metal oxide; An electrolyte, wherein the electrolyte comprises a carboxylate solvent, and based on the total mass of the electrolyte, the mass content A of the carboxylate solvent satisfies: 20wt%≤A≤80wt%.

2. The battery cell according to claim 1, characterized in that: The battery cell comprises a shell having a wall portion, the wall portion being provided with a pressure relief mechanism, the pressure relief mechanism being provided with a pressure relief notch, the pressure relief notch defining a pressure relief area, and the pressure relief area being provided with a reinforcement structure.

3. The battery cell according to claim 2, characterized in that: The reinforcement structure includes a reinforcement notch, and the thickness of the pressure relief mechanism at the reinforcement notch is greater than the thickness of the pressure relief mechanism at the pressure relief notch.

4. The battery cell according to claim 3, characterized in that: The reinforcement notch extends along a first direction and connects two ends of the pressure relief notch in the first direction, and the first direction is a width direction of the wall portion.

5. The battery cell according to claim 3, characterized in that: The reinforcement structure includes two or more reinforcement notches, and the two or more reinforcement notches are arranged at intervals along a second direction, and the second direction is the length direction of the wall portion.

6. The battery cell according to claim 5, characterized in that: Along the second direction, the distance L1 between two adjacent reinforcement notches satisfies: 0.3 mm ≤ L1 ≤ 1.0 mm.

7. The battery cell according to claim 6, characterized in that: 0.5mm≤L1≤0.8mm.

8. The battery cell according to claim 6, characterized in that: Along the second direction, the interval L1 between adjacent reinforcing notches and the size L2 of the pressure relief notch satisfy: 0.2≤L1 / L2≤0.

5.

9. The battery cell according to claim 8, characterized in that: 0.25≤L1 / L2≤0.

45.

10. The battery cell according to claim 3, characterized in that: The thickness T1 of the pressure relief mechanism at the reinforced notch satisfies: 0.4 mm ≤ T1 ≤ 0.6 mm.

11. The battery cell according to claim 2, characterized in that: The thickness T2 of the pressure relief mechanism at the pressure relief notch satisfies: 0.3mm≤T2≤0.5mm.

12. The battery cell according to claim 2, characterized in that: The area S of the pressure relief area meets the following requirements: 500mm 2 ≤S≤1000mm 2 , and / or, the capacity Q of the battery cell satisfies: 80Ah≤Q≤150Ah.

13. The battery cell according to claim 12, characterized in that: 20wt%≤A≤50wt%, and / or, 500mm 2 ≤S≤800mm 2 , and / or, 80Ah≤Q≤150Ah.

14. The battery cell according to claim 12, characterized in that: 50wt%≤A≤80wt%, and / or, 600mm 2 ≤S≤1000mm 2 , and / or, 80Ah≤Q≤120Ah.

15. The battery cell according to claim 1, characterized in that: The lithium-containing phosphate includes: LiFe a Mn b PO4, Among them, a+b=1, 3:7≤a:b≤5:

5.

16. The battery cell according to claim 1, characterized in that: The lithium-containing transition metal oxide comprises: Li 1+c [Ni x Co y Mn z M d ]O 2-e ; Wherein, M includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta or Sr, 0.2≥c≥-0.2, 0.95≥x≥0.5, 0.2≥y≥0.05, 0.3>z>0, 0.3>d≥0, 0.5≥e≥0.

17. The battery cell according to claim 1, characterized in that: Based on the total mass of the positive electrode active material, the mass content C of the lithium-containing phosphate satisfies: 40 wt % ≤ C < 100 wt %.

18. The battery cell according to claim 17, characterized in that: 45wt%≤C≤70wt%.

19. The battery cell according to claim 1, characterized in that: The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side surface of the positive electrode current collector, the positive electrode film layer comprises the positive electrode active material, the positive electrode current collector comprises aluminum foil, and the thickness of the aluminum foil is 10 μm to 13 μm.

20. The battery cell according to claim 1, characterized in that The positive electrode plate further includes a conductive agent, and the conductive agent includes carbon nanotubes.

21. The battery cell according to claim 1, characterized in that: The surface density of the positive electrode sheet is 190g / m 2 ~230g / m 2 , and / or, the compaction density of the positive electrode sheet is 2.5g / cm 3 ~2.9g / cm 3 .

22. The battery cell according to claim 21, characterized in that: The compaction density of the positive electrode sheet is 2.8 g / cm 3 ~2.9g / cm 3 .

23. The battery cell according to claim 1, characterized in that: The battery cell includes a housing having a wall portion, and the wall portion is provided with an electrode terminal; The battery cell comprises an electrode assembly, wherein the electrode assembly comprises a main body and a tab, wherein the tab is connected to one end of the main body facing the wall; The battery cell includes a connecting member, the connecting member is arranged between the wall portion and the main body portion, the connecting member includes a first connecting portion and a second connecting portion connected to each other, the first connecting portion is connected to the electrode terminal, and the second connecting portion is connected to the electrode tab; Wherein, along the thickness direction of the wall portion, the thickness D1 of the first connection portion and the thickness D2 of the second connection portion satisfy: D1-D2≥0.1 mm.

24. The battery cell according to claim 23, characterized in that: The thickness D1 of the first connection portion satisfies: 0.5 mm ≤ D1 ≤ 1.2 mm, and the thickness D2 of the second connection portion satisfies: 0.3 mm ≤ D2 ≤ 1 mm.

25. The battery cell according to claim 23, characterized in that: The wall portion includes a first through hole; The electrode terminal comprises a main body and a step portion, at least a portion of the main body is passed through the first through hole, the step portion protrudes from the outer peripheral surface of the main body, and the step portion is located on a side of the wall portion facing the outside of the battery cell; The battery cell includes a fixing member, and the fixing member includes a second through hole for the main body to pass through; In the thickness direction of the wall portion, at least a portion of the fixing member is located between the wall portion and the step portion and abuts against the step portion, the main body portion has a first end face facing the outside of the battery cell, and the fixing member has a second end face facing the outside of the battery cell, and the first end face exceeds the second end face.

26. The battery cell according to claim 25, characterized in that: In the thickness direction of the wall portion, a height difference D between the first end surface and the second end surface satisfies: 0.5 mm≤D≤1.5 mm.

27. The battery cell according to claim 25, characterized in that: In the radial direction of the main body, a dimension W1 of the step portion protruding from the outer circumferential surface of the main body satisfies: 0.1 mm ≤ W1 ≤ 5 mm.

28. The battery cell according to claim 1, characterized in that: The battery cell also includes a negative electrode plate, which includes a negative electrode collector and a negative electrode film layer arranged on at least one side of the negative electrode collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes graphite, and the volume average particle size Dv50 of the graphite satisfies: 10μm≤Dv50≤14μm.

29. The battery cell according to claim 28, characterized in that: The negative electrode current collector includes copper foil, and the thickness of the copper foil is 4 μm to 6 μm.

30. The battery cell according to claim 28, characterized in that The surface density of the negative electrode sheet is 90g / m 2 ~110g / m 2 , and / or, the compaction density of the negative electrode sheet is 1.3 g / cm 3 ~1.55g / cm 3 .

31. The battery cell according to claim 30, characterized in that: The compaction density of the negative electrode plate is 1.4 g / cm 3 ~1.5g / cm 3 .

32. The battery cell according to claim 1, characterized in that The ionic conductivity σ of the electrolyte satisfies: 8mS / cm≤σ≤14mS / cm.

33. The battery cell according to claim 32, characterized in that: 9mS / cm≤σ≤13mS / cm.

34. The battery cell according to claim 1, characterized in that The carboxylate solvent includes a compound of the structure shown in Formula I, Wherein, R1 and R2 each independently include at least one of a C1-C5 alkyl group and a C1-C5 halogenated alkyl group.

35. The battery cell according to claim 34, characterized in that: The carboxylate solvent includes: one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, isopropyl formate, propyl acetate, methyl acrylate or ethyl acrylate.

36. The battery cell according to claim 1, characterized in that The electrolyte further includes a carbonate solvent, and the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, propylene carbonate or ethyl methyl carbonate.

37. The battery cell according to claim 1, characterized in that The electrolyte includes an additive, and the additive includes at least one of FEC, PS, and VC; Based on the total mass of the electrolyte, the mass content B of the additive satisfies: <B≤5wt%。 38. The battery cell according to claim 37, characterized in that: 1wt%≤B≤3wt%.

39. A battery device, characterized in that: include: A battery cell according to any one of claims 1 to 38.

40. An electrical device, characterized in that: include: A battery device according to claim 39.

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