Secondary battery cell and electric device

Abstract

The embodiment of the invention provides a secondary battery monomer and a power utilization device, the secondary battery monomer comprises an electrode assembly, the electrode assembly comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive pole active material, the positive pole active material comprises lithium-containing phosphate and lithium-containing transition metal oxide, the negative pole piece comprises a negative pole active material, and the negative pole piece comprises lithium-containing phosphate and lithium-containing transition metal oxide. The negative electrode active material comprises graphite; and the discharge plateau voltage v of the secondary battery monomer at 25 DEG C within the voltage range of 2.5-4.25 V at the discharge rate of 1 / 3C meets the condition that v is more than or equal to 3.6 V and less than or equal to 3.67 V. The secondary battery monomer provided by the invention can give consideration to relatively high energy density and good cycle performance.

Description

Technical Field

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

[0002] In recent years, secondary batteries, mainly lithium-ion batteries, have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields, and have thus achieved great development.

[0003] Improving the energy density of secondary battery cells is the research focus of lithium-ion batteries. However, while improving the energy density, other properties of the secondary battery cells may be affected, such as cycle performance and safety performance. Therefore, how to balance the energy density and cycle performance of secondary battery cells has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application is made in view of the above technical problems, and its purpose is to provide a secondary battery cell and an electrical device, wherein the secondary battery cell can effectively improve the cycle performance under the premise of higher energy density.

[0005] In a first aspect, a secondary battery cell is provided, the secondary battery cell comprising: an electrode assembly, the electrode assembly comprising a positive electrode plate and a negative 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, the negative electrode plate comprising a negative electrode active material, the negative electrode active material comprising graphite; the secondary battery cell at 25°C, at a discharge rate of 1 / 3C in a voltage range of 2.5V-4.25V, has a discharge platform voltage v that satisfies: 3.6V≤v≤3.67V.

[0006] In an embodiment of the present application, the positive electrode active material includes both lithium-containing phosphate and lithium-containing transition metal oxide, the negative electrode active material includes graphite, and the discharge platform voltage of the secondary battery cell is controlled within a specific range of 3.6V-3.67V, thereby effectively improving the cycle performance of the secondary battery cell under the premise of higher energy density.

[0007] In some embodiments, the lithium-containing phosphate comprises a lithium-containing transition metal phosphate.

[0008] In some embodiments, the lithium-containing phosphate comprises a lithium phosphate having a molecular formula of Li 1+a Mn b A 1-b P 1-c R cO4 or one or more of its modified compounds, -0.2≤a<1, 0.3≤b≤0.9, 0≤c≤0.1, A includes one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and R includes one or more of B, Si, N, S, F, Cl and Br.

[0009] In some embodiments, the lithium-containing transition metal oxide comprises a molecular formula of Li x Ni y Co z M k Me p O r E s ; wherein, the M includes one or more elements of Mn and Al, the Me includes one or more elements of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W or Nb, and the E includes one or more elements of N, F, S and Cl; 0.8≤x≤1.15, 0<y<1, 0<z<1, 0<k<1, 0≤p≤0.1, 1≤r≤2, 0≤s≤1.

[0010] In the embodiments of the present application, by controlling the ratio of each metal element in the lithium-containing phosphate and the lithium-containing transition metal oxide within a suitable range, the discharge voltage platform of the secondary battery cell can be affected so that the discharge voltage platform of the secondary battery cell is within a designed range.

[0011] In some embodiments, the volume distribution particle size Dv501 of the positive electrode active material satisfies: 1.5 μm≤Dv501≤3 μm.

[0012] In some embodiments, the lithium-containing phosphate satisfies at least one of the following conditions (1)-(2): (1) the lithium-containing phosphate includes one or more elements of Al, Ti, and V; (2) the lithium-containing phosphate includes a first lithium-containing phosphate and a second lithium-containing phosphate, and the volume distribution particle size Dv50 of the first lithium-containing phosphate is 1-1 Meet: 0.05μm≤Dv50 1-1 ≤0.3 μm; and / or, the volume distribution particle size Dv50 of the second lithium-containing phosphate 1-2 Satisfy: 1μm≤Dv50 1-2 ≤3μm; (3) the volume distribution particle size of the lithium-containing phosphate Dv50 1-3 Meet: 0.8μm≤Dv50 1-3 ≤1.2μm.

[0013] In some embodiments, the lithium-containing transition metal oxide satisfies at least one of the following conditions (1)-(4): (1) the volume distribution particle size Dv50 of the lithium-containing transition metal oxide 1-4 Meet: 3μm≤Dv50 1-4 ≤5μm; (2) the volume distribution particle size Dv101 of the lithium-containing transition metal oxide satisfies: 1.5μm≤Dv101≤2.5μm; (3) the volume distribution particle size Dv901 of the lithium-containing transition metal oxide satisfies: 7.5μm≤Dv901≤9.5μm; (4) the particle size distribution of the lithium-containing transition metal oxide satisfies: 0.95≤(Dv901-Dv10 1-4 ) / Dv50 1-4 ≤1.5.

[0014] The particle size of the lithium-containing phosphate and / or lithium-containing transition metal oxide is within a suitable range, which helps to regulate the discharge voltage platform of the secondary battery monomer so that the discharge voltage platform of the secondary battery monomer is within the designed range, thereby further improving the energy density and cycle performance of the battery.

[0015] In some embodiments, based on the total mass of the positive electrode active material, the mass content m1 of the lithium-containing phosphoric acid satisfies: 40%≤m1≤70%.

[0016] When the mass fraction of lithium phosphate in the positive electrode active material is within an appropriate range, the discharge voltage platform of the secondary battery cell can be effectively adjusted within the designed range, thereby further improving the energy density and cycle performance of the battery; at the same time, the structure of lithium phosphate is relatively stable and it is not easy to release oxygen when the battery thermally runs away, thereby further improving the thermal safety performance of the battery.

[0017] In some embodiments, the positive electrode plate includes a conductive agent, the conductive agent includes carbon nanotubes, and the diameter d of the carbon nanotubes satisfies: 7 μm≤d≤13 μm.

[0018] Using carbon nanotubes with a diameter within a suitable range as a conductive agent can effectively construct a conductive network between the conductive agent and the positive electrode active material, thereby helping to improve the rate performance and cycle performance of the secondary battery cell.

[0019] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material.

[0020] In some embodiments, the coating weight ρ1 of a single side of the positive electrode film layer satisfies: 190 g / m 2 ≤ρ1≤230g / m 2 .

[0021] In the embodiments of the present application, by controlling the coating weight of the positive electrode film layer within a suitable range, it can help improve the energy density of the secondary battery cell and also affect the discharge voltage platform of the secondary battery cell so that the discharge voltage platform of the secondary battery cell is within the designed range.

[0022] In some embodiments, the compaction density P1 of the positive electrode film layer satisfies: 2.5 g / cm 3 ≤P1≤2.9g / cm 3 ; Optionally, 2.8 g / cm 3 ≤P1≤2.9g / cm 3 .

[0023] In the embodiments of the present application, by controlling the compaction density of the positive electrode film layer within a suitable range, it helps to improve the lithium ion dynamics, thereby reducing the polarization of the secondary battery cell during the cycle process, and helping to improve the cycle performance of the secondary battery cell.

[0024] In some embodiments, the thickness h1 of the positive electrode current collector satisfies: 10 μm≤h1≤13 μm.

[0025] In the embodiments of the present application, by controlling the thickness of the positive electrode current collector within a suitable range, it helps to reduce the thickness of the positive electrode plate and helps to improve the energy density of the secondary battery cell.

[0026] In some embodiments, the average volume particle size Dv502 of the negative electrode active material satisfies: 10 μm≤Dv502≤14 μm.

[0027] In the embodiments of the present application, 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 helps to improve the rate performance and cycle performance of the secondary battery cell.

[0028] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes the negative electrode active material.

[0029] In some embodiments, the coating weight ρ2 of a single side of the negative electrode film layer satisfies: 90 g / m 2 ≤ρ2≤110g / m 2 .

[0030] In the embodiments of the present application, controlling the coating weight of the negative electrode film layer within a suitable range helps to improve the energy density of the secondary battery cell.

[0031] In some embodiments, the compaction density P2 of the negative electrode film layer satisfies: 1.3 g / cm 3 ≤P2≤1.55g / cm 3; Optionally, 1.4 g / cm 3 ≤P2≤1.5g / cm 3 .

[0032] In the embodiments of the present application, by controlling the compaction density of the negative electrode film layer within a suitable range, it helps to improve the lithium ion dynamics, thereby reducing the polarization of the secondary battery cell during the cycle process, and helping to improve the cycle performance of the secondary battery cell.

[0033] In some embodiments, the thickness h2 of the negative electrode current collector satisfies: 4 μm≤h2≤6 μm.

[0034] In the embodiments of the present application, 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 secondary battery cell.

[0035] In some embodiments, the electrode assembly is a laminated electrode assembly.

[0036] In the embodiments of the present application, the energy density of the secondary battery cell can be further improved by adopting a laminated electrode assembly.

[0037] In some embodiments, the secondary battery cell includes a shell, and the electrode assembly is accommodated in the shell; the shell includes a first wall, and the electrode terminal is arranged on the first wall; 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 first wall; the secondary battery cell includes a current collecting component, and the current collecting component 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 first wall, the thickness D1 of the first connecting part satisfies: 0.5mm≤D1≤1.2mm; the thickness D2 of the second connecting part satisfies: 0.3mm≤D2≤1mm.

[0038] In the embodiment of the present application, 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 current collecting member is connected to the electrode terminal is greater than the thickness of the area where the current collecting member is connected to the tab. Since the thickness requirement of the area where the current collecting member is connected to the tab is less than the thickness requirement of the area where the current collecting member is connected to the electrode terminal, the thickness of the current collecting member can be effectively optimized while the current collecting member can be connected to the electrode terminal and the tab, so as to reduce the overall weight of the current collecting member and save the space occupied by the current collecting member, and improve the energy density of the secondary battery cell. The thickness of the first connection part and the thickness of the second connection part are both controlled within a suitable range, so as to meet the connection strength between the first connection part and the electrode terminal, and between the second connection part and the tab while improving the energy density of the secondary battery cell.

[0039] In some embodiments, the first 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, and the step portion protrudes from the outer peripheral surface of the main body and is arranged outside the secondary battery cell; the secondary 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 first wall, at least a portion of the fixing member is located between the first wall and the step portion and abuts against the step portion, the main body has a first end face facing the outside of the secondary battery cell, and the fixing member has a second end face facing the outside of the secondary battery cell, and the first end face exceeds the second end face.

[0040] In the embodiment of the present application, in the thickness direction of the first wall, the surface of the secondary battery cell that exceeds the outer surface of the first wall by the maximum height is the first end face. When electrode terminals of the same specification are used, the height of the secondary battery cell that exceeds the first wall can be reduced accordingly, thereby increasing the proportion of the space inside the secondary battery cell casing to the total space of the battery, thereby increasing the energy density of the battery.

[0041] In some embodiments, in the thickness direction of the first wall, a height difference H between the first end surface and the second end surface satisfies: 0.5 mm≤H≤1.5 mm.

[0042] In the embodiment of the present application, by controlling the height difference between the first end face and the second end face within a suitable range in the thickness direction of the first wall, it is possible to improve the energy density of the battery while ensuring that the connection stability between the first end face and the second end face is as good as possible.

[0043] 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.

[0044] In the embodiment of the present application, by controlling the size of the step portion protruding from the outer peripheral surface of the main body within a suitable range, it is helpful to increase the contact area between the step portion and the fixing member, thereby helping to improve the connection strength between the step portion and the fixing member.

[0045] In some embodiments, the secondary battery cell includes an electrolyte, and the ion conductivity σ of the electrolyte satisfies: 7mS / cm≤σ≤10mS / cm.

[0046] In the embodiments of the present application, the selection of an electrolyte with a higher ion conductivity helps to improve the lithium ion dynamics during the cycle of the secondary battery cell, thereby helping to improve the cycle performance of the secondary battery cell.

[0047] In some embodiments, the electrolyte includes: a solvent, wherein the solvent includes a linear carbonate; and based on the total mass of the electrolyte, a mass content m2 of the linear carbonate satisfies 40wt%≤m2≤70wt%.

[0048] In the embodiments of the present application, by selecting a linear carboxylate as a solvent and controlling its mass content in the electrolyte within a suitable range, it helps to reduce the viscosity of the electrolyte, thereby helping to improve the lithium ion kinetics.

[0049] In some embodiments, the electrolyte includes: a lithium salt, the lithium salt includes LiPF6 and LiFSI; based on the total mass of the electrolyte, the mass content m3 of the lithium salt satisfies 13wt%≤m3≤18wt%.

[0050] In the embodiments of the present application, by selecting LiPF6 and LiFSI as lithium salts, it helps to improve the lithium ion conductivity and high temperature resistance of the electrolyte, thereby helping to improve the lithium ion dynamics during the cycle of the secondary battery cells and improve the cycle performance of the secondary battery cells.

[0051] In some embodiments, based on the total amount of the lithium salt, the molar content of LiPF6 accounts for n and satisfies: 50%≤n≤70%.

[0052] In the embodiment of the present application, by controlling the molar content of LiPF6 in the lithium salt to be within a relatively high range, it helps to form a stable SEI film on the surface of the negative electrode plate, thereby helping to improve the cycle performance of the secondary battery cell 20.

[0053] In some embodiments, the secondary battery cell includes a separator, the separator includes a porous substrate, and the thickness h3 of the porous substrate satisfies: h3≤7μm; optionally, 3μm≤h3≤5μm. Controlling the thickness of the porous substrate within the given range helps to further improve the energy density of the secondary battery cell.

[0054] In a second aspect, a secondary battery is provided, wherein the secondary battery comprises the secondary battery cell according to any implementation of the first aspect.

[0055] In a third aspect, an electrical device is provided, wherein the electrical device comprises a secondary battery cell in any implementation manner of the first aspect, and / or a secondary battery in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] 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.

[0057] Figure 1 It is a cross-sectional schematic diagram of a laminated electrode assembly.

[0058] Figure 2 A cross-sectional schematic diagram of another laminated electrode assembly.

[0059] Figure 3 A cross-sectional schematic diagram of a wound electrode assembly.

[0060] Figure 4 A schematic structural diagram of a secondary battery cell.

[0061] Figure 5 for Figure 4 An exploded view of a secondary battery cell is shown.

[0062] Figure 6 It is a partial schematic diagram of a secondary battery cell.

[0063] Figure 7 A partial exploded view of a secondary battery cell.

[0064] Figure 8 A partial cross-sectional view of a secondary battery cell.

[0065] Fig. 9 for Figure 8 Schematic diagram of a local area.

[0066] Fig.10 A schematic diagram of a secondary battery. DETAILED DESCRIPTION

[0067] Hereinafter, the embodiments of the secondary battery cell and the electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0068] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0069] In the description of this application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating directions or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting this application. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0070] If not otherwise specified, in this application, the phrase "A and / or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A and / or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0071] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0072] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0073] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their generally accepted meanings in the art.

[0074] Where mentioned, "lithium-containing phosphate" refers to a class of salts including the element lithium and phosphate ions.

[0075] When the “lithium-containing phosphate” further includes a transition metal, it may be referred to as a “lithium-containing transition metal phosphate”.

[0076] “Lithium-containing phosphates” may include, for example, lithium iron phosphate materials, lithium iron manganese phosphate materials, and the like.

[0077] 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, for example, lithium-containing nickel-cobalt-manganese oxides and lithium-containing nickel-cobalt-aluminum oxides. It should be understood that ternary materials can also be doped or coated with trace amounts of other transition metal elements, and it is generally believed that ternary materials doped or coated with other transition metal elements are still ternary materials.

[0078] If mentioned, "discharge rate" refers to the current value required for a secondary battery cell to discharge its rated capacity within a specified time. It is numerically equal to a multiple of the rated capacity and is usually represented by the letter C. Discharge rate = discharge current / rated capacity. Discharge rate is a measure of how fast a secondary battery cell discharges. For example, if the rated capacity of a battery is discharged in 1 hour, the discharge rate of the secondary battery cell is 1C.

[0079] As mentioned, "discharge platform voltage" refers to the voltage corresponding to the "platform area" in the voltage-capacity or voltage-time curve under constant current discharge conditions. In the voltage-capacity or voltage-time curve of the discharge process, the voltage first drops rapidly as the discharge capacity or discharge time increases, then the voltage remains almost unchanged or changes very little, and then the voltage drops rapidly to the cut-off voltage. The part of the curve where the voltage remains almost unchanged or changes very little is the "platform area". The discharge platform voltage can be the voltage corresponding to the platform area (voltage remains almost unchanged) or the median of the voltage range corresponding to the platform area (voltage changes). The discharge platform voltage of a secondary battery cell can also be approximately calculated using the ratio of the discharge energy to the discharge capacity of the secondary battery cell, that is, discharge platform voltage = discharge energy / discharge capacity, where the unit of discharge energy is Wh and the unit of discharge capacity is Ah.

[0080] If mentioned, "linear carbonate" refers to a class of substances with a chain structure and containing carbonate groups (-OCO-O-), such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc.

[0081] Next, embodiments of the present application are introduced.

[0082] 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 secondary 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 secondary 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 secondary battery cell proceeds normally.

[0083] Improving the energy density of secondary battery cells has always been a research focus in the battery field. Positive electrode active materials are one of the direct factors that directly affect the energy density of secondary battery cells. Lithium-containing phosphates with good thermal 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 secondary battery cells. Lithium-containing transition metal oxides are beneficial to improving the energy density of secondary battery cells, but their safety performance is poor. At present, there are some solutions for mixing the two in the hope of obtaining secondary battery cells that take into account both safety performance and high capacity.

[0084] In addition, from the perspective of practical application, in addition to the energy density and safety performance of secondary battery cells, the cycle performance of secondary battery cells is also an important performance indicator. When a mixed material containing lithium phosphate and lithium transition metal oxide is selected as the positive electrode active material, the cycle performance of the secondary battery cells may not meet the application requirements.

[0085] In view of this, the embodiments of the present application provide a secondary battery cell, a secondary battery and an electrical device, wherein the discharge platform voltage of the secondary battery cell is controlled within a suitable range, so that the secondary battery cell can have both high energy density and good cycle performance.

[0086] Next, the secondary battery cell provided by the present application is introduced.

[0087] [Secondary battery cell]

[0088] First, a secondary battery cell is provided, the secondary battery cell includes an electrode assembly, the electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate and a lithium-containing transition metal oxide, and the negative electrode plate 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, and the negative electrode active material includes graphite. The discharge platform voltage v of the secondary battery cell at 25°C and at a discharge rate of 1 / 3C in the voltage range of 2.5V-4.25V satisfies: 3.6V≤v≤3.67V.

[0089] The secondary battery cell of the present application, under the premise that the positive electrode active material includes a lithium-containing phosphate and a lithium-containing transition metal oxide, controls the discharge platform voltage of the secondary battery cell in a specific voltage interval within a specific range, which can effectively improve the cycle performance of the battery under the premise of having a higher energy density. Specifically, under the same mass or volume, the higher the discharge platform voltage, the higher the energy that the secondary battery can release. However, if the discharge platform voltage is too high, the electrolyte of the secondary battery cell will undergo a redox reaction to produce gas, consume the active lithium ions in the electrolyte, and affect the cycle performance of the secondary battery cell. Specifically, when the positive electrode active material includes both a lithium-containing phosphate and a lithium-containing transition metal oxide, if the discharge platform voltage is too low (for example, lower than 3.6V), the energy density of the battery cell is low. The possible reason is that the content of the lithium-containing transition metal oxide in the positive electrode active material is low or the structure has collapsed, and the discharge capacity contributed to the discharge process is very limited. If the discharge platform voltage is too high (for example, higher than 3.67V), it may lead to poor battery cycle performance. The possible reason is that the proportion of lithium-containing transition metal oxides in the positive electrode active material is high, which makes the discharge platform voltage of the secondary battery monomer high. Excessive discharge platform voltage will cause the electrolyte to produce gas by side reaction, affecting the cycle performance of the secondary battery monomer. Therefore, when the positive electrode active material includes both lithium-containing phosphate and lithium-containing transition metal oxide, controlling the discharge platform voltage within the given range can effectively improve the battery cycle performance while having a higher energy density.

[0090] The discharge platform voltage of a secondary battery cell can be adjusted by adjusting the active material and the electrode preparation process parameters, such as the type, ratio, and particle size of the active material, the coating weight and compaction density of the electrode, etc.

[0091] It should be understood that, taking into account the normal error of the test conditions, the discharge platform voltage tested under the above conditions within the range of 25℃±2℃, if it falls within the range specified in this application, can be equivalent to the test result at 25℃ and is deemed to fall within the scope of this application.

[0092] In some embodiments, the mass fraction m1 of the lithium-containing phosphate in the positive electrode active material satisfies: 40wt%≤m1≤70wt%; optionally, 45wt%≤m1≤70wt%.

[0093] Specifically, m1 can be 40wt%, 42wt%, 44wt%, 45wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, 62wt%, 64wt%, 66wt%, 68wt%, 70wt%, or its value is within the range obtained by combining any two of the above values.

[0094] By controlling the mass content of lithium-containing phosphate within a suitable range, the ratio of lithium-containing phosphate and lithium-containing transition metal oxide in the positive electrode active material is indirectly regulated, which helps to adjust the discharge platform voltage of the secondary battery cell within a specific range, so that the secondary battery cell has both high energy density and good cycle performance. In addition, lithium-containing phosphate has good thermal stability. When the positive electrode active material includes both lithium-containing phosphate and lithium-containing transition metal oxide, controlling the content of lithium-containing phosphate within the above range can further improve the energy density and cycle performance of the secondary battery while maintaining high safety. Because the thermal stability of lithium-containing transition metal oxide is generally not as good as that of lithium-containing phosphate, it is easy to react with the electrolyte at high temperature, which may affect the safety performance and cycle performance of the secondary battery cell.

[0095] In some embodiments, the lithium-containing phosphate includes a lithium-containing transition metal phosphate.

[0096] In some embodiments, the lithium-containing phosphate includes a molecular formula of Li 1+a Mn b A 1-b P 1-c R c O4 or one or more of its modified compounds, -0.2≤a<1, 0.3≤b≤0.9, 0≤c≤0.1, A includes one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, R includes one or more of B, Si, N, S, F, Cl and Br; and / or, the lithium-containing transition metal oxide includes a molecular formula of Li x Ni y Co z M k Me p O r E s ; wherein M includes one or more elements of Mn and Al, Me includes one or more elements of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W or Nb, and E includes one or more elements of N, F, S and Cl; 0.8≤x≤1.15, 0<y<1, 0<z<1, 0<k<1, 0≤p≤0.1, 1≤r≤2, 0≤s≤1.

[0097] Specifically, the manganese element in the positive electrode active material helps to increase the discharge platform voltage of the secondary battery cell. In this embodiment, by selecting a lithium-containing phosphate containing manganese elements and mixing it with a lithium-containing transition metal oxide, it helps to increase the discharge platform voltage of the secondary battery cell, thereby further improving the energy density of the secondary battery cell. In addition, the lithium-containing transition metal oxide may contain some Me elements, which help to improve the stability of the lithium-containing transition metal oxide, thereby helping to improve the cycle performance of the secondary battery cell. In addition, by controlling the proportion of each metal element in the lithium-containing transition metal oxide within a suitable range, the discharge voltage platform of the secondary battery cell can also be affected, so that the discharge voltage platform of the secondary battery cell is within the designed range, so that the secondary battery cell has both high energy density and good cycle performance.

[0098] In other embodiments, 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 0.2 O2 (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 0.05O2) and at least one of its modified compounds. Examples of lithium-containing phosphates 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.

[0099] The positive electrode active material includes Li 1+d [Ni f Co g Mn h M i ]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.

[0100] In some embodiments, 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.

[0101] In some embodiments, the volume distribution particle size Dv501 of the positive electrode active material satisfies: 1.5 μm≤Dv501≤3 μm.

[0102] Specifically, Dv501 can be 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, or its value is within the range obtained by combining any two of the above values.

[0103] In some embodiments, the lithium-containing phosphate includes one or more elements of Al, Ti, and V. Specifically, the lithium-containing phosphate may also include trace elements such as Al, Ti, and V, which help to improve the structural stability of the lithium-containing phosphate, thereby further improving the cycle performance of the secondary battery cell.

[0104] In some embodiments, the lithium-containing phosphate includes a first lithium-containing phosphate and a second lithium-containing phosphate, and the volume distribution particle size Dv50 of the first lithium-containing phosphate is 1-1 Meet: 0.05μm≤Dv50 1-1 ≤0.3μm; Volume distribution particle size Dv50 of the second lithium-containing phosphate 1-2 Satisfy: 1μm≤Dv50 1-2 ≤3μm. Specifically, Dv50 1-1 It can be 0.05μm, 0.08μm, 0.1μm, 0.12μm, 0.14μm, 0.16μm, 0.18μm, 0.2μm, 0.22μm, 0.24μm, 0.26μm, 0.28μm, 0.3μm, or a value within the range obtained by combining any two of the above values. Dv50 1-2 The particle size can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, or any value within the range obtained by combining any two of the above values. The combination of two lithium-containing phosphates with different particle sizes helps to increase the compaction density of the positive electrode sheet, thereby further increasing the energy density of the secondary battery.

[0105] In some embodiments, the volume distribution particle size Dv50 of the lithium phosphate 1-3 Meet: 0.8μm≤Dv50 1-3 ≤1.2μm.

[0106] Specifically, Dv50 1-3It can be 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, or its value is within the range obtained by combining any two of the above values. The particle size of the lithium-containing phosphate has a certain influence on the discharge platform voltage of the secondary battery cell. The smaller the volume distribution particle size of the lithium-containing phosphate, the smaller the diffusion path of the lithium ions, the more conducive to the diffusion of lithium ions, and the higher the discharge platform voltage of the secondary battery cell. However, if the volume distribution particle size of the lithium-containing phosphate is too small, the particles are easy to agglomerate, thereby increasing the internal resistance of the battery cell, which is not conducive to the cycle stability of the secondary battery cell. Therefore, this embodiment can further improve the energy density and cycle performance of the secondary battery cell by controlling the volume distribution particle size of the lithium-containing phosphate within a suitable range.

[0107] In some embodiments, the volume distribution particle size Dv50 of the lithium-containing transition metal oxide is 1-4 Meet: 3μm≤Dv50 1-4 ≤5μm.

[0108] In some embodiments, the volume distribution particle size Dv101 of the lithium-containing transition metal oxide satisfies: 1.5 μm≤Dv101≤2.5 μm.

[0109] In some embodiments, the volume distribution particle size Dv901 of the lithium-containing transition metal oxide satisfies: 7.5 μm≤Dv901≤9.5 μm.

[0110] In some embodiments, the particle size distribution of the lithium-containing transition metal oxide satisfies: 0.95≤(Dv901-Dv10 1-4 ) / Dv50 1-4 ≤1.5.

[0111] Specifically, Dv50 1-4 It can be 3μm, 3.2μm, 2.4μm, 2.6μm, 2.8μm, 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, or its value is within the range obtained by combining any two of the above values. Dv101 can be 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, or its value is within the range obtained by combining any two of the above values. Dv901 can be 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9μm, or any value within the range obtained by combining any two of the above values. (Dv901-Dv10 1-4 ) / Dv50 1-4It can be 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or a value within the range obtained by combining any two of the above values.

[0112] The particle size of the lithium-containing transition metal oxide has a certain influence on the discharge platform voltage of the secondary battery cell. The smaller the volume distribution particle size of the lithium-containing transition metal oxide, the higher the discharge platform voltage of the secondary battery cell. At the same time, if the volume distribution particle size of the lithium-containing transition metal oxide is too small, the side reactions between it and the electrolyte may increase, which may affect the cycle performance of the secondary battery cell. Therefore, this embodiment can further improve the energy density and cycle performance of the secondary battery cell by controlling the volume distribution particle size of the lithium-containing transition metal oxide within a suitable range.

[0113] In some embodiments, the positive electrode plate includes a conductive agent, the conductive agent includes carbon nanotubes, and the diameter d of the carbon nanotubes satisfies: 7 μm≤d≤13 μm.

[0114] Specifically, the carbon nanotubes include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes. d can be 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, or its value is within the range obtained by combining any two of the above values. The conductive agent has a certain influence on the internal resistance, rate performance, cycle performance, etc. of the secondary battery cell. Compared with conductive agents such as conductive carbon black and Ketjen black, the carbon nanotubes and the positive electrode active materials are in linear contact, which can form a better conductive network between the positive electrode active materials, have higher conductivity efficiency, can reduce the polarization of the secondary battery cell during the cycle, and improve the rate performance and cycle performance of the secondary battery cell.

[0115] Generally speaking, the smaller the diameter of carbon nanotubes, the better the conductivity. However, the smaller the diameter, the more difficult it is to prepare, which is not conducive to improving production efficiency. Therefore, in this embodiment, by selecting carbon nanotubes with a smaller diameter but within a suitable range as the conductive agent, it is helpful to improve the rate performance, cycle performance and production efficiency of the secondary battery monomer.

[0116] The carbon nanotubes may be at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0117] In some embodiments, the coating weight ρ1 of a single side of the positive electrode film layer satisfies: 190 g / m 2 ≤ρ1≤230g / m 2 .

[0118] Specifically, ρ1 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.

[0119] According to the present application, the coating weight of the film layer on the pole piece also has a certain influence on the discharge platform voltage of the secondary battery cell. The smaller the coating weight of the film layer, the higher the discharge platform voltage; however, if the coating weight of the film layer is too small, it is not conducive to the energy density of the secondary battery cell. Therefore, by controlling the coating weight of the positive electrode film layer within a suitable range, the present embodiment can make the discharge voltage platform of the secondary battery cell within the designed range, thereby further improving the energy density and cycle performance of the secondary battery cell.

[0120] In some embodiments, the compaction density P1 of the positive electrode film layer satisfies: 2.5 g / cm 3 ≤P1≤2.9g / cm 3 .

[0121] Specifically, P1 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. The greater the compaction density of the positive electrode film layer, the more conducive it is to improving the energy density of the secondary 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 film layer, thereby affecting the dynamics of lithium ions. Therefore, in this embodiment, by controlling the compaction density of the positive electrode film layer within a suitable range, the energy density of the secondary battery cell can be improved, and it is helpful for the electrolyte to infiltrate the positive electrode film layer, thereby reducing polarization, improving the dynamics of lithium ions at the positive electrode, and thus improving the cycle performance of the secondary battery cell.

[0122] In some embodiments, the thickness h1 of the positive electrode current collector satisfies: 10 μm≤h1≤13 μm.

[0123] Specifically, h1 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 plate, thereby increasing the energy density of the secondary battery cell. If the thickness of the current collector is too thin, it will affect the mechanical strength of the electrode plate, and it may break during the processing or use of the secondary battery cell, resulting in a sudden decrease in the capacity of the secondary battery cell, which is not conducive to the energy density of the secondary battery cell. This embodiment helps to improve the energy density of the secondary battery cell by controlling the thickness of the positive electrode current collector within a suitable range.

[0124] In some embodiments, in addition to the graphite mentioned above, the negative electrode active material may also include negative electrode active materials for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: 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.

[0125] In some embodiments, the average volume particle size Dv502 of the negative electrode active material satisfies: 10 μm≤Dv502≤14 μm.

[0126] Specifically, Dv502 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 secondary 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 extraction and embedding of lithium ions and improving the capacity of the secondary 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 secondary battery cell may be increased, and the cycle performance of the secondary battery cell may be affected. Therefore, this embodiment can help improve the capacity and cycle performance of the secondary battery cell by controlling the average volume particle size of the negative electrode active material within a suitable range.

[0127] In some embodiments, the coating weight ρ3 of a single side of the negative electrode film layer satisfies: 90 g / m 2 ≤ρ3≤110g / m 2 .

[0128] Specifically, ρ3 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. The coating weight of the negative electrode film layer will also affect the discharge platform voltage of the secondary battery cell. The greater the single-sided coating weight of the negative electrode film layer, the lower the discharge platform voltage of the secondary battery cell. This embodiment controls the coating weight of the negative electrode film layer within a suitable range, so that the discharge voltage platform of the secondary battery cell is within the designed range, so that the secondary battery cell has good cycle performance under the premise of having a higher energy density.

[0129] In some embodiments, the compaction density P2 of the negative electrode film layer satisfies: 1.3 g / cm 3 ≤P2≤1.55g / cm 3 ; Optionally, 1.4 g / cm3 ≤P2≤1.5g / cm 3 .

[0130] Specifically, ρ4 can be 1.3 g / 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. The greater the compaction density of the negative electrode film layer, the more conducive it is to improving the energy density of the secondary battery cell. However, if the compaction density of the negative electrode film layer is too large, it may affect the infiltration of the electrolyte into the negative electrode active material, thereby affecting the lithium ion dynamics. Therefore, in this embodiment, by controlling the compaction density of the negative electrode film layer within a suitable range, the energy density of the secondary battery cell can be improved, and the electrolyte can be helped to infiltrate the negative electrode plate to reduce polarization, thereby improving the dynamics of lithium ions at the negative electrode plate and improving the cycle performance of the secondary battery cell.

[0131] In some embodiments, the thickness h2 of the negative electrode current collector satisfies: 4 μm≤h2≤6 μm.

[0132] Specifically, h2 can be 4μm, 4.2μm, 4.4μm, 4.6μm, 4.8μm, 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, or a value within the range obtained by combining any two of the above values. This embodiment helps to improve the energy density of the secondary battery cell by controlling the thickness of the negative electrode collector within a suitable range.

[0133] Figure 1 and Figure 2 It is a cross-sectional schematic diagram of a laminated electrode assembly. Figure 3 FIG. 1 is a cross-sectional schematic diagram of a wound electrode assembly. For ease of explanation, the pole ears included in each pole piece are not shown here. Figure 1-3 As shown, the electrode assembly 10 includes a positive electrode sheet 11 and a negative electrode sheet 12 and a separator 13 disposed between the positive electrode sheet 11 and the negative electrode sheet 12 .

[0134] In some embodiments, Figure 1As shown in the figure, the electrode assembly 10 is a laminated electrode assembly. The electrode assembly 10 includes a plurality of positive electrode sheets 11 and a plurality of negative electrode sheets 12; the plurality of positive electrode sheets 11 and the plurality of negative electrode sheets 12 are alternately stacked in the direction indicated by the arrows in the figure. In another embodiment, as shown in the figure Figure 2 As shown, the electrode assembly 10 includes a plurality of positive electrode sheets 11 and negative electrode sheets 12, the negative electrode sheets 12 may include at least one bending section and a plurality of stacking sections, each bending section is used to connect two stacking sections, and the plurality of positive electrode sheets 11 and the plurality of stacking sections of the negative electrode sheets 12 are alternately stacked in the direction indicated by the arrow in the figure to form another stacked electrode assembly 10. Alternatively, the electrode assembly 10 includes a plurality of negative electrode sheets 12 and positive electrode sheets 11, the positive electrode sheets 11 may include at least one bending section and a plurality of stacking sections, each bending section is used to connect two stacking sections, and the plurality of negative electrode sheets 12 and the plurality of stacking sections of the positive electrode sheets 11 are alternately stacked in the direction indicated by the arrow in the figure to form another stacked electrode assembly 10.

[0135] In some embodiments, Figure 3 As shown, the electrode assembly 10 may also be a wound electrode assembly. The positive electrode sheet 11 , the separator 13 and the negative electrode sheet 12 of the electrode assembly 10 are wound to form the electrode assembly 10 .

[0136] According to the present application, the electrode assembly 10 is preferably a laminated electrode assembly. Compared with a wound electrode assembly, a laminated electrode assembly has a higher space utilization rate inside the shell of the secondary battery cell 20. When the shell is the same, the laminated electrode assembly can accommodate more active materials in the shell, thereby further improving the energy density of the secondary battery cell.

[0137] Figure 4-Figure 5 Schematic diagram of the structure of a secondary battery cell 20 of the present application.

[0138] like Figure 4-5 As shown, in some embodiments, the secondary battery cell 20 includes a housing 21 , the electrode assembly 10 is accommodated in the housing 21 , the housing 21 includes a first wall 211 , and the electrode terminal 22 is disposed on the first wall 211 .

[0139] More specifically, the housing 21 may include a shell 212 and an end cap 213. The shell 212 is formed with a receiving cavity inside, and the receiving cavity has an opening 2121, that is, the shell 212 is a hollow structure with one end open, and the end cap 213 covers the opening 2121 of the shell 212 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 10 and the electrolyte. Optionally, the first wall 211 for mounting the electrode terminal 22 may be the end cap 213, or may be one of the multiple walls of the shell 212. Exemplarily, in Figure 4 and Figure 5In the figure, the first wall 211 is the end cover 213 of the shell 21. Of course, in other embodiments, the first wall 211 can also be the bottom wall of the shell 212 arranged opposite to the end cover 213 in the thickness direction X of the end cover 213 or the side wall adjacent to the end cover 213 and abutting against each other.

[0140] 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 10. For example, if the electrode assembly 10 is a cylindrical structure, the shell 212 can be a cylindrical structure; if the electrode assembly 10 is a cuboid structure, the shell 212 can be a cuboid structure. Of course, the end cap 213 can also be a variety of structures, such as a plate-like structure or a hollow structure with one end open. For example, in Figure 4 and Figure 5 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 openings 2121 on opposite sides. One end cap 213 is correspondingly covered at one opening 2121 of the shell 212 to form a sealed connection, so as to form a sealed space for accommodating the electrode assembly 10 and the electrolyte.

[0141] Figure 6 It is a partial schematic diagram of a secondary battery cell 20 in the electrode terminal 22 area of ​​the present application.

[0142] refer to Figure 4-6 In some embodiments, the electrode assembly 10 includes a main body 101 and a tab 102, wherein the tab 102 is connected to one end of the main body 101 facing the first wall 211. The secondary battery cell 20 includes a current collecting member 24, which is disposed between the first wall 211 and the main body 101. The current collecting member 24 includes a first connecting portion 241 and a second connecting portion 242 connected to each other, wherein the first connecting portion 241 is connected to the electrode terminal 22, and the second connecting portion 242 is connected to the tab 102. Along the thickness direction X of the first wall 211, the thickness D1 of the first connecting portion 241 satisfies: 0.5 mm ≤ D1 ≤ 1.2 mm; the thickness D2 of the second connecting portion 242 satisfies: 0.3 mm ≤ D2 ≤ 1 mm.

[0143] Specifically, the main body 101 of the electrode assembly 10 is the main area where the electrochemical reaction of the electrode assembly 10 occurs in the secondary battery cell 20. The main body 101 is a layout formed by winding or stacking the area of ​​the positive electrode plate 11 coated with the positive electrode active material, the separator, and the area of ​​the negative electrode plate 12 coated with the negative electrode active material. The tab 102 is used to output or input the positive or negative electrode of the electrode assembly 10. The tab 102 is used to connect to the electrode terminal 22 to achieve electrical connection between the electrode assembly 10 and the electrode terminal 22. It should be noted that the tab 102 of the electrode assembly 10 is a component formed by stacking and connecting the areas on the positive electrode plate 11 that are not coated with the positive electrode active material or a component formed by stacking and connecting the areas on the negative electrode plate 12 that are not coated with the negative electrode active material. If the tab 102 is used for the positive electrode of the output electrode assembly 10, the tab 102 is a component formed by the regions on the positive electrode sheet 11 that are not coated with the positive electrode active material being stacked and connected to each other; if the tab 102 is used for the negative electrode of the output electrode assembly 10, the tab 102 is a component formed by the regions on the negative electrode sheet 12 that are not coated with the negative electrode active material being stacked and connected to each other. Exemplarily, the tab 102 is connected to one end of the body 101 facing the end cover 213 in the thickness direction X of the end cover 213.

[0144] The electrode assembly 10 contained in the housing 21 may be one or more. Figure 5 In the embodiment, the outer shell 21 of the secondary battery cell 20 is provided with two electrode assemblies 10, and the two electrode assemblies 10 are stacked along the thickness direction thereof, that is, the two electrode assemblies 10 are stacked along the thickness direction of the secondary battery cell 20. Of course, in other embodiments, the electrode assemblies 10 accommodated in the outer shell 21 may be one, three, four, five, six, seven or eight, etc.

[0145] The electrode terminal 22 is a component for outputting or inputting electric energy to the secondary battery cell 20. For example, the material of the electrode terminal 22 can also be multiple, for example, the material of the electrode terminal 22 can be copper, iron, aluminum, steel, aluminum alloy, etc. The end of the electrode terminal 22 facing the electrode assembly 10 is connected to the current collecting member 24, and the end of the electrode terminal 22 away from the electrode assembly 10 is used to connect to the current collecting member to realize the input or output of electric energy of the secondary battery cell 20. The end cover 213 is provided with a first through hole 2111, and the first through hole 2111 penetrates both sides of the end cover 213 along the thickness direction X of the end cover 213. The electrode terminal 22 is penetrated in the first through hole 2111 to install the electrode terminal 22 on the end cover 213, and the first through holes 2111 are extended from both ends of the electrode terminal 22. The electrode terminal 22 is installed on the end cover 213 in an insulated manner, that is, no electrical connection is formed between the electrode terminal 22 and the end cover 213. The secondary battery cell 20 may further include an insulating member 26 to insulate and separate the end cap 213 and the electrode terminal 22. The secondary battery cell 20 may further include a sealing member 27 to seal a gap between the electrode terminal 22 and a hole wall surface of the first through hole 2111.

[0146] exist Figure 4 and Figure 5 In the embodiment, the secondary battery cell 20 includes two electrode terminals 22, and correspondingly, each electrode assembly 10 has two tabs 102, and the polarities of the two tabs 102 are opposite. The two electrode terminals 22 are electrically connected to the two tabs 102 of the electrode assembly 10, respectively, to realize the input or output of the positive and negative electrodes of the secondary battery cell 20.

[0147] The current collecting component 24 serves to connect the electrode terminal 22 and the tab 102 to achieve electrical connection between the electrode assembly 10 and the electrode terminal 22. Exemplarily, the material of the current collecting component 24 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. The connection structure between the current collecting component 24 and the electrode terminal 22 can be various, such as welding, abutment or bonding, etc. Similarly, the connection structure between the current collecting component 24 and the tab 102 can also be various, such as welding or abutment, etc. There are two electrode terminals 22 and two current collecting components 24, and the two current collecting components 24 are arranged at intervals along the first direction Z. Each electrode terminal 22 is connected to the electrode assembly 10 through a current collecting component 24 to output the positive and negative electrodes of the secondary battery cell 20. As shown Figure 6 As shown, the current collecting member 24 may further include a bending portion 243 , and the first connection portion 241 and the second connection portion 242 are connected via the bending portion 243 .

[0148] For example, D1 can be 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.15 mm, 1.2 mm, or a value thereof within the range obtained by combining any two of the above values. D2 can be 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 0.95 mm, 1 mm, or a value thereof within the range obtained by combining any two of the above values.

[0149] In this embodiment, the thickness of the region of the current collecting member 24 used for connecting the electrode terminal 22 is greater than the thickness of the region of the current collecting member 24 used for connecting the electrode tab 102. Since the thickness requirement of the region where the current collecting member 24 is connected to the electrode tab 102 is less than the thickness requirement of the region where the current collecting member 24 is connected to the electrode terminal 22, the thickness of the current collecting member 24 can be effectively optimized while the current collecting member 24 can be connected to the electrode terminal 22 and the electrode tab 102, so as to reduce the overall weight of the current collecting member 24 and save the space occupied by the current collecting member 24, thereby optimizing the weight and internal space utilization of the secondary battery cell 20, which is conducive to improving the energy density of the secondary battery cell 20.

[0150] Furthermore, by setting the thickness of the first connection part 241 and the thickness of the second connection part 242 within a suitable range, on the one hand, the structural strength of the first connection part 241 and the second connection part 242 can be improved, so that the first connection part 241 and the second connection part 242 have sufficient thickness to be connected to the electrode terminal 22 and the pole tab 102, which is conducive to improving the connection stability and reliability between the first connection part 241 and the second connection part 242 and the electrode terminal 22 and the pole tab 102, and reducing the phenomenon of insufficient overcurrent between the current collecting member 24 and the electrode terminal 22, and between the current collecting member 24 and the pole tab 102. On the other hand, the connection difficulty between the first connection part 241 and the electrode terminal 22, and between the second connection part 242 and the pole tab 102 can be reduced, and the space occupied by the current collecting member 24 in the housing 21 can be reduced, which is conducive to improving the energy density of the secondary battery cell 20.

[0151] Figure 7 It is an exploded view of a partial structure of a secondary battery cell 20 of the present application. Figure 8 This is a cross-sectional view of a partial structure of a secondary battery cell 20 of the present application. Fig. 9 for Figure 8 Schematic diagram of a local area.

[0152] like Figure 7-9As shown, in some embodiments, the first wall 211 includes a first through hole 2111, and the electrode terminal 22 includes a main body 221 and a step portion 222, the step portion 222 protrudes from the outer peripheral surface of the main body 221, and the step portion 222 is located on the side of the first wall 211 facing the outside of the secondary battery cell 20. The secondary battery cell 20 includes a fixing member 28, and the fixing member 28 includes a second through hole 281 for the main body 221 to pass through. In the thickness direction of the first wall 211, at least a portion of the fixing member 28 is located between the first wall 211 and the step portion 222 and abuts against the step portion 222. The main body 221 has a first end face 2211 facing the outside of the secondary battery cell 20, and the fixing member 28 has a second end face 282 facing the outside of the secondary battery cell 20, and the first end face 2211 exceeds the second end face 282.

[0153] Specifically, the exterior of the secondary battery cell 20 refers to the portion outside the housing 21 of the secondary battery cell 20. The first end face 2211 exceeds the second end face 282, which means that, outside the secondary battery cell 20, in the thickness direction of the first wall 211, the second end face 282 is located between the first end face 2211 and the outer surface of the first wall 211. In other words, the surface farthest from the outer surface of the first wall 211 is the first end face 2211 of the electrode terminal 22.

[0154] The outer peripheral surface of the main body 221 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 221 as a quadrangular prism as an example, the main body 221 includes a top surface, a bottom surface and four side surfaces, the four side surfaces are sequentially connected and surrounded by 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 221. In some embodiments, the first end surface 2211 is provided with a first groove 2212, and the side surface of the first groove 2212 may also be referred to as the outer peripheral surface of the main body 221. In this embodiment, the main body 221 is shaped like a "convex" character. In some embodiments, the step portion 222 has a third end surface 2221 facing away from the first wall 211.

[0155] The outer contour of the fixing member 28 may include, but is not limited to, a circle, an ellipse, a polygon, a semicircle, etc. The fixing member 28 is made of a metal material, for example, aluminum, copper, iron, steel, an alloy or a composite metal. The step portion 222 may be continuously distributed along the circumference of the main body portion 221, that is, in a ring shape. It may also be arranged in segments along the circumference of the main body portion 221, that is, divided into a plurality of parts, at least one part of which abuts against the fixing member 28. The first through hole 2111 and the second through hole 281 may be a light hole or a segmented step hole. In the embodiment where the first through hole 2111 and the second through hole 281 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.

[0156] In the present embodiment, in the thickness direction of the first wall 211, the surface of the secondary battery cell 20 that exceeds the maximum height of the outer surface of the first wall 211 is the first end surface 2211. When the electrode terminals 22 of the same specification are used, the height of the secondary battery cell 20 that exceeds the first wall 211 can be reduced accordingly, thereby increasing the proportion of the space inside the shell 21 of the secondary battery cell 20 to the total space of the secondary battery cell 20, thereby increasing the energy density of the secondary battery cell 20.

[0157] The electrode terminal 22 further includes a limiting portion 223 , which protrudes from the outer peripheral surface of the main body 221 and is located inside the first wall 211 . The limiting portion 223 is used to limit the movement of the electrode terminal 22 to the outside of the housing 21 .

[0158] Exemplarily, the insulating member 26 includes a body portion 261 and a first extension portion 262, the body portion 261 is located between the fixing member 28 and the first wall 211, the body portion 261 is provided with a third through hole 2611 through which the supply terminal 22 passes, and the first extension portion 262 is located at the periphery of the fixing member 28 and is arranged around the edge of the body portion 261. The sealing member 27 is at least partially located between the first wall 211 and the limiting portion 223.

[0159] In some embodiments, in the thickness direction of the first wall 211 , a height difference H between the first end surface 2211 and the second end surface 282 satisfies: 0.5 mm≤H≤1.5 mm.

[0160] Specifically, D can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, or any value thereof within the range obtained by combining any two of the above values. By controlling H within a suitable range, the energy density of the secondary battery cell 20 can be increased while ensuring good connection stability between the first end face 2211 and the second end face 282 as much as possible.

[0161] In some embodiments, in the radial direction of the main body 221 , a dimension W1 of the step portion 222 protruding from the outer circumferential surface of the main body 221 satisfies: 0.1 mm≤W1≤5 mm.

[0162] Specifically, 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. By controlling the size of the step portion 222 protruding from the outer peripheral surface of the main body 221 within a suitable range, it is beneficial to increase the contact area between the step portion 222 and the fixing member 28, and then it is beneficial to improve the connection strength between the step portion 222 and the fixing member 28.

[0163] In some embodiments, the secondary battery cell 20 includes an electrolyte, and the ion conductivity σ of the electrolyte satisfies: 7 mS / cm≤σ≤10 mS / cm.

[0164] Specifically, σ can be 7mS / cm, 7.5mS / cm, 8mS / cm, 8.5mS / cm, 9mS / cm, 9.5mS / cm, 10mS / cm, or its value is within the range obtained by combining any two of the above values. The higher the ionic conductivity of the electrolyte, the more favorable it is to the lithium ion dynamics inside the secondary battery cell 20, and the cycle performance of the secondary battery cell 20 can be improved. Too high ionic conductivity of the electrolyte is not conducive to the stability of the electrolyte, and may cause an increase in side reactions inside the battery cell 20, affecting the cycle stability of the secondary battery cell 20. In this embodiment, by controlling the ionic conductivity of the electrolyte within a suitable range, it is helpful to improve the lithium ion dynamics during the cycle of the secondary battery cell 20, and help improve the cycle performance of the secondary battery cell 20.

[0165] In some embodiments, the electrolyte includes: a solvent, the solvent includes a linear carbonate; based on the total mass of the electrolyte, the mass content m2 of the linear carbonate satisfies 40wt%≤m2≤70wt%.

[0166] Specifically, m2 can be 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, or a value thereof within the range obtained by combining any two of the above values. In this embodiment, by selecting a linear carboxylate as a solvent and controlling its mass content in the electrolyte within a suitable range, it helps to reduce the viscosity of the electrolyte, thereby helping to improve lithium ion dynamics.

[0167] In some embodiments, the electrolyte includes: a lithium salt, the lithium salt includes LiPF6 and LiFSI; based on the total mass of the electrolyte, the mass content m3 of the lithium salt satisfies 13wt%≤m3≤18wt%.

[0168] Specifically, m3 can be 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, or a value thereof within the range obtained by combining any two of the above values.

[0169] LiFSI has high ion conductivity and good high temperature stability, which helps to improve the high temperature cycle performance of the battery cell. By selecting LiPF6 and LiFSI as lithium salts and controlling their content within a suitable range, it helps to improve the lithium ion conductivity and high temperature resistance of the electrolyte, thereby helping to improve the lithium ion dynamics during the cycle of the secondary battery cell 20 and improve the cycle performance of the secondary battery cell 20.

[0170] In some embodiments, based on the total amount of the lithium salt, the molar content of LiPF6 accounts for n and satisfies: 50%≤n≤70%.

[0171] Specifically, it can be 50%, 55%, 60%, 65%, 70%, or any value within the range obtained by combining any two of the above values. LiPF6 has good film-forming stability. By controlling the molar content of LiPF6 within a higher range, it helps to form a stable SEI film on the surface of the negative electrode, helping to improve the cycle performance of the secondary battery cell 20.

[0172] 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 secondary battery cell 20 are described in detail. It should be understood that the lithium-ion battery is only used as an example, and the solution provided in this application can also be applied to other types of secondary batteries, such as sodium-ion batteries, magnesium-ion batteries, lithium-sulfur batteries, etc.

[0173] [Negative electrode]

[0174] The negative electrode sheet 12 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, and the negative electrode active material includes graphite.

[0175] In some embodiments, the graphite material may be at least one of artificial graphite and natural graphite.

[0176] 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.

[0177] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0178] In some embodiments, the negative electrode film layer further comprises 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).

[0179] In some embodiments, 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.

[0180] In some embodiments, the negative electrode film layer further includes other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0181] In some embodiments, the negative electrode sheet 12 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 12 can be obtained.

[0182] [Positive electrode]

[0183] The positive electrode plate 11 includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode material includes a lithium-containing phosphate and a lithium-containing transition metal oxide.

[0184] 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.

[0185] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0186] In some embodiments, 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.

[0187] In some embodiments, 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.

[0188] In some embodiments, the positive electrode sheet 11 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 11 can be obtained.

[0189] [Electrolyte]

[0190] The electrolyte plays a role in conducting ions between the positive electrode plate 11 and the negative electrode plate 12. The present application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0191] In addition to the types of lithium salts mentioned in the previous embodiments, 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.

[0192] 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.

[0193] 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.

[0194] [Isolation film]

[0195] The present application has no particular limitation on the type of the isolation membrane 13 . For example, any known isolation membrane 13 with a porous structure having good chemical stability and mechanical stability may be selected.

[0196] In some embodiments, the isolation film 13 includes a porous substrate, and the material of the porous substrate can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The porous substrate can be a single-layer film or a multi-layer composite film, without particular limitation. When the porous substrate is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0197] In some embodiments, the thickness h3 of the porous substrate satisfies: h3≤7 μm; optionally, 3 μm≤h3≤5 μm.

[0198] Specifically, h3 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or any value within the range obtained by combining any two of the above values. Controlling the thickness of the porous substrate within the given range helps to further improve the energy density of the secondary battery cell.

[0199] In some embodiments, the isolation film 13 further includes a porous coating layer, which can play a role of heat resistance and / or adhesion.

[0200] In some embodiments, the porous coating layer includes heat-resistant particles. The heat-resistant particles may include at least one of inorganic particles and organic particles.

[0201] In some embodiments, the inorganic particles may include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ion conductivity but not storing ions, or inorganic particles capable of electrochemical reactions.

[0202] In some embodiments, the inorganic particles having a dielectric constant of 5 or more may include boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb1-mLamZr1-nTinO3 (abbreviated as PLZT, 0<m<1, 0<n<1), Pb(Mg3Nb 2 / 3 )O3-PbTiO3 (abbreviated as PMN-PT), and one or more of their respective modified inorganic particles. Optionally, the modification of each inorganic particle can be chemical modification and / or physical modification.

[0203] In some embodiments, inorganic particles having ion conductivity but not storing ions may include Li3PO4, lithium titanium phosphate, Li x1 Ti y1 (PO4)3, Lithium Aluminum Titanate Phosphate Li x2 Al y2 Ti z1 (PO4)3, (LiAlTiP) x3 O y3 Type glass, lanthanum lithium titanate Li x4 La y4 TiO3, Lithium Germanium Phosphate Thiophosphate x5 Ge y5 P z2 S w 、Lithium Nitride Li x6 N y6 、SiS2 glass Li x7 Si y7 S z3 and P2S5 glass Li x8 P y8 S z4 One or more of 0<x1<2, 0<y1<3, 0<x2<2, 0<y2<1, 0<z1<3, 0<x3<4, 0<y3<13, 0<x4<2, 0<y4<3, 0<x5<4, 0<y5<1, 0<z2<1, 0<w<5, 0<x6<4, 0<y6<2, 0<x7<3, 0<y7<2, 0<z3<4, 0<x8<3, 0<y8<3, 0<z4<7. This can improve the ion conductivity of the isolation membrane.

[0204] In some embodiments, the inorganic particles capable of undergoing an electrochemical reaction may include one or more of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.

[0205] In some embodiments, the organic particles may include at least one of a thermoplastic resin polymer, a thermosetting resin polymer, or a cross-linked polymer.

[0206] In some embodiments, the thermoplastic resin polymer may include one or more of polycarbonate organic particles, polymethyl methacrylate organic particles, polyoxymethylene organic particles, polyamide organic particles, styrene-acrylonitrile copolymer, polyphenylene sulfide organic particles, polyetheretherketone organic particles, polyimide organic particles, polysulfone organic particles, polyethersulfone organic particles, polyphenylene sulfone organic particles, polybenzimidazole organic particles, polyamideimide organic particles, and polyethyleneimine organic particles.

[0207] In some embodiments, the thermosetting resin polymer may include one or more of phenolic resin organic particles, polymer particles containing triazine ring structural units, epoxy resin organic particles, unsaturated polyester resin organic particles, urea-formaldehyde resin organic particles, and furan resin organic particles.

[0208] In some embodiments, the cross-linked polymer may include one or more of cross-linked styrene-based organic particles and silicon-containing organic cross-linked resin particles.

[0209] In some embodiments, the porous coating layer includes binder particles. The binder particles may include homopolymers or copolymers of acrylate monomer units, homopolymers or copolymers of acrylic acid monomer units, homopolymers or copolymers of styrene monomer units, polyurethane compounds, rubber compounds, homopolymers or copolymers of fluorinated olefin monomer units, homopolymers or copolymers of olefin monomer units, homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of alkylene oxide monomer units, and one or more of the modified compounds of the above homopolymers or copolymers.

[0210] In some embodiments, the binder particles may include copolymers of acrylic acid ester monomer units and styrene monomer units, copolymers of acrylic acid monomer units and styrene monomer units, copolymers of acrylic acid monomer units and acrylic acid ester monomer units and styrene monomer units, copolymers of styrene monomer units and unsaturated nitrile monomer units, copolymers of styrene monomer units and olefin monomer units and unsaturated nitrile monomer units, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, copolymers of different fluorine-containing olefin monomer units, copolymers of fluorine-containing olefin monomer units and vinyl monomer units, copolymers of fluorine-containing olefin monomer units and acrylic acid monomer units, copolymers of fluorine-containing olefin monomer units and acrylic acid ester monomer units, and one or more of the modified compounds of the above homopolymers or copolymers.

[0211] In some embodiments, the binder particles may include butyl acrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate copolymer, isooctyl methacrylate-styrene copolymer, methacrylate-methacrylic acid-styrene copolymer, methyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, methyl acrylate-styrene-acrylonitrile copolymer, isooctyl methacrylate-styrene-acrylonitrile copolymer, styrene-vinyl acetate copolymer, styrene-vinyl acetate-pyrrolidone copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer, and one or more of the modified compounds of the above copolymers.

[0212] In some embodiments, the coating may further include a dispersant, for example, may include but is not limited to one or more of dispersants such as alkylphenol polyoxyethylene ether, polyacrylic acid dispersants, and cellulose dispersants. As an example, the dispersant may include but is not limited to one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0213] [Secondary battery]

[0214] The embodiment of the present application provides a secondary battery, including the secondary battery cell 20 in the above embodiment. The secondary battery can be a single physical module including one or more secondary battery cells to provide higher voltage and capacity. When there are multiple secondary battery cells 20, the multiple secondary battery cells 20 are connected in series, in parallel or in mixed connection through a busbar component.

[0215] In some embodiments, the secondary battery may be a battery pack. The secondary battery includes a case and secondary battery cells 20 . The secondary battery cells 20 or battery modules are accommodated in the case.

[0216] 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.

[0217] In some embodiments, the secondary battery may be located in an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0218] Fig.10 Schematic diagram of a battery according to an embodiment of the present application. Fig.10 As shown, the battery 30 may include a plurality of secondary battery cells 20 to meet different power usage requirements.

[0219] The battery 30 may also include a casing, the interior of which is a hollow structure, and a plurality of secondary battery cells 20 are accommodated in the casing. For example, a plurality of secondary battery cells 20 are connected in parallel, in series, or in a mixed combination and placed in the casing. The casing may include a first casing portion 301 and a second casing portion 302, which cover each other to form the casing. The shapes of the first casing portion 301 and the second casing portion 302 may be determined according to the shapes of the components accommodated therein, for example, they may be determined according to the shape of the combination of the plurality of secondary battery cells 20 accommodated therein, and at least one of the first casing portion 301 and the second casing portion 302 may have an opening. For example, as Fig.10 As shown, only one of the first box body 301 and the second box body 302 may be a hollow rectangular parallelepiped with an opening, and the other may be a plate-shaped to cover the opening. Taking the second box body 302 as a hollow rectangular parallelepiped 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 secondary battery cells 20.

[0220] In addition, the present application also provides an electrical device, which includes the secondary battery in the aforementioned embodiment.

[0221] For example, different from Fig.10As 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 secondary battery cells 20. Multiple secondary battery cells 20 are connected in parallel, in series, or in mixed combination and placed in the box formed by the first box body 301 and the second box body 302 buckled together.

[0222] In some embodiments, the secondary battery may further include other components. For example, the secondary battery may further include a busbar component, which may be used to realize electrical connection between multiple secondary battery cells 20, such as parallel connection, series connection, or mixed connection. Specifically, the busbar component may realize electrical connection between the secondary battery cells 20 by connecting the electrode terminals of the secondary battery cells 20; or, the busbar component may also realize electrical connection between the secondary battery cells 20 by connecting other components of the secondary battery cells 20. The busbar component may be fixed to the corresponding components of the secondary battery cell 20 by welding, for example, it may be fixed to the electrode terminal, the sealing structure, or the housing by welding, etc., and the embodiments of the present application are not limited thereto.

[0223] The secondary battery cells 20 may directly form the secondary battery 30 , or may first form a battery module, and then a plurality of battery modules may form the secondary battery 30 .

[0224] [Electrical devices]

[0225] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0226] The electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. The vehicle may be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, and the like; the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, and the like; the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, and the like; the electric tool may include a metal cutting electric tool, a grinding electric tool, an assembly electric tool, and an electric tool for railways, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator, and an electric planer, and the like. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0227] The present application provides an electrical device, which is a vehicle.

[0228] The vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor, a controller and a secondary battery 30 can be arranged inside the vehicle, and the controller is used to control the secondary battery 30 to power the motor. For example, a secondary battery 30 can be arranged at the bottom, front or rear of the vehicle. The secondary battery 30 can be used to power the vehicle. For example, the secondary battery 30 can be used as an operating power source for the vehicle, for the circuit system of the vehicle, for example, for the working power requirements during the start-up, navigation and operation of the vehicle. In another embodiment of the present application, the secondary battery 30 can not only be used as an operating power source for the vehicle, but also as a driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0229] 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.

[0230] [Examples and Comparative Examples]

[0231] Example 1

[0232] (1) Preparation of positive electrode sheet

[0233] The positive electrode active material (containing lithium phosphate LiMn 0.6 Fe 0.4 O4 and Li-containing layered metal oxides LiNi 0.65 Co 0.15 Mn 0.20 O2 in a mass ratio of 80wt%:20wt%), binder polyvinylidene fluoride (PVDF), conductive agent acetylene black, carbon nanotubes in a mass ratio of 96.5:2:1:0.5, add NMP, stir evenly in a blender, then coat the slurry on a 12-micron thick aluminum foil, dry in an oven, cold press, and cut to obtain a positive electrode sheet. Among them, the volume distribution particle size Dv50 of the lithium-containing phosphate is 1.1μm, the volume distribution particle size Dv50 of the lithium-containing transition metal oxide is 3.8μm, the Dv50 of the positive electrode active material after the lithium-containing phosphate and the lithium-containing transition metal oxide are mixed is 1.68μm, and the single-sided coating weight of the positive electrode film layer is ρ1=214g / m 2 , the compaction density of the positive electrode film layer P1 = 2.46g / cm 3 .

[0234] (2) Preparation of negative electrode sheet

[0235] The negative electrode active material artificial graphite, sodium carboxymethyl cellulose, styrene butadiene rubber and acetylene black are mixed in a mass ratio of 96:1:1:2, deionized water is added, and the mixture is stirred evenly in a blender. The slurry is then coated on a 6-micron thick copper foil, dried in an oven, cold pressed, and cut to obtain a negative electrode sheet. The volume distribution particle size Dv50 of the artificial graphite is 12 μm, and the coating weight of a single side of the negative electrode film layer is ρ1 = 99 g / m 2 , the compaction density of the negative electrode film layer P1 = 1.4g / cm 3 .

[0236] (3) Preparation of electrolyte

[0237] In an argon atmosphere glove box with a water content of less than 10ppm, ethylene carbonate (EC) and ethyl methyl carbonate (DEC) were mixed in a volume ratio of 1:2, and then lithium salts of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI) were uniformly dissolved in the solvent, and then additives PS and VC were added to obtain an electrolyte. The molar concentration of lithium salt in the electrolyte is 1 mol / L, and the molar content of LiPF6 and LiFSI is 2:1. The mass percentages of additives PS and VC in the electrolyte are 1.5% and 1.0%, respectively.

[0238] (4) Isolation film

[0239] Polyethylene is used as the isolation membrane.

[0240] (5) Preparation of secondary battery monomers

[0241] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, and then wound to obtain an electrode assembly, which is placed in a shell, injected with electrolyte, and then packaged to obtain a secondary battery cell. The battery cell has a thickness of 63 mm, a width of 280 mm, and a height of 82 mm.

[0242] Examples 2-6, Comparative Example 1

[0243] Compared with Example 1, the difference is that the parameters of the positive electrode active material or the positive electrode plate are different from those in Example 1, as shown in Table 1 for details.

[0244] Product parameters and performance parameters of Examples 1-6 and Comparative Example 1.

[0245] Table 1: Product parameters and performance parameters of Examples 1-6 and Comparative Example 1

[0246] In Table 1, "m%" indicates the mass content of the corresponding substance in the positive electrode active material, "Dv50" indicates the volume distribution particle size Dv50 of the corresponding substance, "positive electrode Dv50" indicates the volume distribution particle size Dv50 of the positive electrode active material, "coating weight" indicates the single-sided coating weight of the positive electrode film layer on the positive electrode sheet, "compacted density" indicates the compacted density of the positive electrode film layer, "energy density" indicates the volume energy density of the battery cell, and "cycle performance" indicates the number of cycles of the battery cell under normal temperature cycle test. The specific process of the cycle test is detailed in the test section below.

[0247] According to the comparative analysis of the embodiment and the comparative example, the embodiment adjusts various parameters to make the discharge platform voltage of the battery cell 20 within a limited range, which can effectively improve the cycle performance of the battery with a higher energy density. However, the discharge platform voltage of the comparative example is not within the limited range, and its cycle performance is poor.

[0248] The following is a brief introduction to the test methods of the physical and chemical parameters and performance parameters involved in the embodiments of the present application. It should be understood that the following test methods are only examples, and other test methods known in the art may also be used for testing.

[0249] 1. Test method of discharge platform voltage

[0250] At 25°C, the secondary battery cell was charged at a constant current of 1 / 3C to a cut-off voltage of 4.25V, then charged at a constant voltage to a current ≤ 0.05C, and then discharged at a constant current of 1 / 3C to a cut-off voltage of 2.5V. The discharge energy E0 and discharge capacity C0 were recorded, and the discharge platform voltage v = E0 / C0.

[0251] 2. Test method for mass content

[0252] The mass ratio of Ni, Co, and Mn in the material to be tested is measured by CP-EDS, and the specific type of lithium-containing transition metal oxide is confirmed based on the mass ratio. The mass ratio of Mn and Fe in the material to be tested is measured by CP-EDS, and the specific type of lithium-containing phosphate is confirmed based on the mass ratio. Then, the mass content of lithium-containing transition metal oxide is calculated by the mass content of Ni in the ICP of the material to be tested, and the mass content of lithium-containing phosphate is calculated by the mass content of Fe.

[0253] 3. Test method for element molar ratio

[0254] Test equipment: Inductively coupled plasma emission spectrometer (ICP).

[0255] Test method: Digestion: 1+1 aqua regia, digestion method: plate / acid digestion / microwave digestion (high temperature and high pressure ~ 200°C). Test the element mass fractions of nickel, cobalt, manganese and doping elements, calculate the molar amount based on the molar mass of each element, and finally normalize and calculate the molar ratio of nickel, cobalt and manganese.

[0256] 4.Dv50 test method

[0257] Testing equipment: particle size testing instrument.

[0258] Pretreatment: Take a clean beaker, add an appropriate amount of the sample to be tested, add a surfactant dropwise and then add a dispersant, and perform ultrasound at 120W / 5min to ensure that the sample is completely dispersed in the dispersant.

[0259] Test: After the sample is poured into the injection tower, it circulates with the solution to the test optical system. When the particles are irradiated by the laser beam, the particle size distribution characteristics (shading degree: 8%-12%) can be obtained by receiving and measuring the energy distribution of the scattered light.

[0260] Calculation: Calculate the particle size at the 50% position on the volume particle size distribution curve from small to large, which is Dv50.

[0261] 5. Test method for film coating weight

[0262] Cut and weigh the positive electrode sheet (negative electrode sheet) of a fixed area, and weigh and calculate the weight of the positive electrode collector (negative electrode collector) of the same area in advance. Subtract the weight of the positive electrode collector (negative electrode collector) from the weight of the positive electrode sheet (negative electrode sheet), and then divide it by the fixed area to obtain the coating weight of the positive electrode film layer (negative electrode film layer).

[0263] 6. Test method for compacted density of membrane layer

[0264] Take a unit area of ​​the electrode to be tested, weigh the mass m1 of the material on the unit area of ​​the electrode except the current collector, measure the electrode thickness T1 and the current collector thickness T0, and the compaction density = m1 / (T1-T0).

[0265] 7. Test method for volume energy density of secondary battery cells

[0266] On the charge and discharge device, charge and discharge for 3 cycles at a current density of 0.33C in the range of 2.5-4.25V, and take the discharge energy Q of the third cycle.

[0267] Measuring the volume V of the secondary battery cell 20: Take a CT scan image of the secondary battery cell 20. Based on the CT scan image, the length T, height h (excluding the height of the electrode terminal), width L, diameter d of the electrode terminal, height H and other data of the secondary battery cell 20 can be measured. The volume of the secondary battery cell 20 can be calculated by the formula V = T × h × L + 2 × π × (d / 2) 2 ×H, the energy density of the secondary battery cell 20 is Q / V (unit: Wh / L). If the shape of the electrode terminal is irregular, the volume of the electrode terminal can be calculated by fitting the irregular shape into a regular shape on a computer and then using the volume calculation formula of the regular shape.

[0268] 8. Cycle performance test method

[0269] The secondary battery cell 20 to be tested is charged to 4.25V at a charging current of 0.5C, and after CV to 0.02C, it is discharged to 2.5V at a discharge current of 1C, and the cycle is continued until the capacity of the secondary battery cell 20 is 80% of the initial capacity, and the charging and discharging are stopped. At this time, the number of cycles of the secondary battery cell 20 is the number of cycles when the secondary battery cell 20 cycles to 80% SOH.

[0270] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery cell, characterized in that: The secondary battery cell comprises: An electrode assembly, the electrode assembly comprising a positive electrode sheet and a negative 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, the negative electrode sheet comprising a negative electrode active material, the negative electrode active material comprising graphite; The discharge platform voltage v of the secondary battery cell at 25° C. and at a discharge rate of 1 / 3C within a voltage range of 2.5V-4.25V satisfies: 3.6V≤v≤3.67V.

2. The secondary battery cell according to claim 1, characterized in that: The lithium-containing phosphate includes a lithium-containing transition metal phosphate; Optionally, the lithium-containing phosphate includes a molecular formula of Li 1+a Mn b A 1-b P 1-c R c O4 or one or more of its modified compounds, -0.2≤a<1, 0.3≤b≤0.9, 0≤c≤0.1, A includes one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, R includes one or more of B, Si, N, S, F, Cl and Br; and / or, The lithium-containing transition metal oxide includes a molecular formula of Li x Ni y Co z M k Me p O r E s ; wherein, the M includes one or more elements of Mn and Al, the Me includes one or more elements of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W or Nb, and the E includes one or more elements of N, F, S and Cl; 0.8≤x≤1.15, 0<y<1, 0<z<1, 0<k<1, 0≤p≤0.1, 1≤r≤2, 0≤s≤1.

3. The secondary battery cell according to claim 1 or 2, characterized in that: The volume distribution particle size Dv501 of the positive electrode active material satisfies: 1.5 μm≤Dv501≤3 μm.

4. The secondary battery cell according to any one of claims 1 to 3, characterized in that: The lithium-containing phosphate satisfies at least one of the following conditions (1)-(3): (1) The lithium-containing phosphate includes one or more elements of Al, Ti, and V; (2) The lithium-containing phosphate comprises a first lithium-containing phosphate and a second lithium-containing phosphate, wherein the volume distribution particle size Dv50 of the first lithium-containing phosphate is 1-1 Meet: 0.05μm≤Dv50 1-1 ≤0.3 μm; and / or, the volume distribution particle size Dv50 of the second lithium-containing phosphate 1-2 Satisfy: 1μm≤Dv50 1-2 ≤3μm; (3) The volume distribution particle size Dv50 of the lithium-containing phosphate 1-3 Meet: 0.8μm≤Dv50 1-3 ≤1.2μm.

5. The secondary battery cell according to any one of claims 1 to 4, characterized in that: The volume distribution particle size Dv50 of the lithium-containing transition metal oxide 1-4 Meet: 3μm≤Dv50 1-4 ≤5μm; and / or, The volume distribution particle size Dv101 of the lithium-containing transition metal oxide satisfies: 1.5 μm≤Dv101≤2.5 μm; and / or, The volume distribution particle size Dv901 of the lithium-containing transition metal oxide satisfies: 7.5 μm≤Dv901≤9.5 μm; and / or, The particle size distribution of the lithium-containing transition metal oxide satisfies: 0.95≤(Dv901-Dv10 1-4 ) / Dv50 1-4 ≤1.

5.

6. The secondary battery cell according to any one of claims 1 to 5, characterized in that: Based on the total mass of the positive electrode active material, the mass content m1 of the lithium-containing phosphoric acid satisfies: 40wt%≤m1≤70wt%.

7. The secondary battery cell according to any one of claims 1 to 6, characterized in that: The positive electrode plate includes a conductive agent, and the conductive agent includes carbon nanotubes; The diameter d of the carbon nanotubes satisfies: 7 μm≤d≤13 μm.

8. The secondary battery cell according to any one of claims 1 to 7, characterized in that: The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material.

9. The secondary battery cell according to claim 8, characterized in that: The coating weight ρ1 of the positive electrode film on one side satisfies: 190 g / m 2 ≤ρ1≤230g / m 2 .

10. The secondary battery cell according to claim 8 or 9, characterized in that: The compaction density P1 of the positive electrode film layer satisfies: 2.5 g / cm 3 ≤P1≤2.9g / cm 3 ; Optional: 2.8g / cm 3 ≤P1≤2.9g / cm 3 .

11. The secondary battery cell according to any one of claims 8 to 10, characterized in that: The thickness h1 of the positive electrode current collector satisfies: 10 μm≤h1≤13 μm.

12. The secondary battery cell according to any one of claims 1 to 11, characterized in that: The average volume particle size Dv502 of the negative electrode active material satisfies: 10 μm≤Dv502≤14 μm.

13. The secondary battery cell according to any one of claims 1 to 12, characterized in that: The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes the negative electrode active material.

14. The secondary battery cell according to claim 13, characterized in that: The coating weight ρ2 of the negative electrode film on one side satisfies: 90 g / m 2 ≤ρ2≤110g / m 2 .

15. The secondary battery cell according to claim 13 or 14, characterized in that: The compaction density P2 of the negative electrode film layer satisfies: 1.3 g / cm 3 ≤P2≤1.55g / cm 3 ; Optional: 1.4g / cm 3 ≤P2≤1.5g / cm 3 .

16. The secondary battery cell according to any one of claims 13 to 15, characterized in that: The thickness h2 of the negative electrode current collector satisfies: 4 μm≤h2≤6 μm.

17. The secondary battery cell according to any one of claims 1 to 16, characterized in that: The electrode assembly is a laminated electrode assembly.

18. The secondary battery cell according to any one of claims 1 to 17, characterized in that: The secondary battery cell comprises a housing; the housing comprises a first wall, and the electrode terminal is arranged on the first wall; the electrode assembly comprises a main body and a tab, and the tab is connected to one end of the main body facing the first wall; The secondary battery cell includes a current collecting member, the current collecting member includes a first connection portion and a second connection portion connected to each other, the first connection portion is connected to the electrode terminal, and the second connection portion is connected to the electrode tab; Wherein, along the thickness direction of the first wall, the thickness D1 of the first connecting portion satisfies: 0.5 mm ≤ D1 ≤ 1.2 mm; and the thickness D2 of the second connecting portion satisfies: 0.3 mm ≤ D2 ≤ 1 mm.

19. The secondary battery cell according to claim 18, characterized in that: The first wall includes a first through hole; The electrode terminal includes a main body and a step portion, wherein at least a portion of the main body is inserted into the first through hole, and the step portion protrudes from the outer peripheral surface of the main body and is disposed outside the secondary battery cell; The secondary 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 first wall, at least a portion of the fixing member is located between the first wall and the step portion and abuts against the step portion, the main body portion has a first end face facing the outside of the secondary battery cell, and the fixing member has a second end face facing the outside of the secondary battery cell, and the first end face exceeds the second end face.

20. The secondary battery cell according to claim 19, characterized in that: In the thickness direction of the first wall, a height difference H between the first end surface and the second end surface satisfies: 0.5 mm≤H≤1.5 mm.

21. The secondary battery cell according to claim 19 or 20, characterized in that: In the radial direction of the main body, a dimension W1 of the step portion protruding from the outer peripheral surface of the main body satisfies: 0.1 mm ≤ W1 ≤ 5 mm.

22. The secondary battery cell according to any one of claims 1 to 21, characterized in that: The secondary battery cell includes an electrolyte, and the ion conductivity σ of the electrolyte satisfies: 7mS / cm≤σ≤10mS / cm.

23. The secondary battery cell according to claim 22, characterized in that: The electrolyte comprises: a solvent, the solvent comprising a linear carbonate; Based on the total mass of the electrolyte, the mass content m2 of the linear carbonate satisfies 40wt%≤m2≤70wt%.

24. The secondary battery cell according to claim 22 or 23, characterized in that: The electrolyte comprises: Lithium salt, the lithium salt comprising LiPF6 and LiFSI; Optionally, based on the total mass of the electrolyte, the mass content m3 of the lithium salt satisfies 13wt%≤m3≤18wt%.

25. The secondary battery cell according to claim 24, characterized in that: Based on the total amount of the lithium salt, the molar content of LiPF6 accounts for n and satisfies: 50%≤n≤70%.

26. The secondary battery cell according to any one of claims 1 to 25, characterized in that: The secondary battery cell comprises a separator, the separator comprises a porous substrate, and a thickness h3 of the porous substrate satisfies: h3≤7 μm; optionally, 3 μm≤h3≤5 μm.

27. An electrical device, characterized in that: The electric device comprises the secondary battery cell according to any one of claims 1 to 26.

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