Secondary battery cell, secondary battery, and electric device

Abstract

The present application relates to the technical field of secondary batteries, and provides a secondary battery cell, a secondary battery, and an electric device, wherein a capacity C of the secondary battery cell satisfies C ≥ 300 Ah, and a width W and a height H of the secondary battery cell satisfy 1 ≤ W / H ≤ 2. The secondary battery cell comprises an electrode sheet, the electrode sheet comprises a main body and an electrode tab, and a distance M between a center line of the electrode tab and an edge of the main body distal to the electrode tab, and a length D of the main body, satisfies the following relationship: 0.6 ≤ M / D ≤ 0.85; the electrode sheet further comprises a positive electrode sheet, a positive electrode active material of the positive electrode sheet comprises a V-doped lithium-containing phosphate material, and a weight percentage of the V element in the positive electrode active material is 0.01%-0.25%. Coordinately controlling the width-to-height W / H ratio of a secondary battery cell, the arrangement position of an electrode tab, and the selection of an active material enables large-capacity batteries with a capacity of at least 300 Ah to achieve low DCR, thereby improving battery energy efficiency.

Description

A secondary battery cell, a secondary battery, and an electrical device. Cross-references

[0001] This application claims priority to Chinese Patent Application No. 2024114871586, filed on October 23, 2024, entitled "A Secondary Battery Cell, a Secondary Battery and an Electrical Device", the contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of secondary battery technology, and more specifically, to a secondary battery cell, a secondary battery, and an electrical device. Background Technology

[0003] Currently, energy storage batteries in the industry are trending towards larger sizes and greater capacities. Generally, increasing battery size increases the electron transport path from the electrodes to the tabs and also exacerbates the unevenness of current density, thereby leading to a deterioration in the battery's current density response (DCR) and a reduction in energy efficiency. Summary of the Invention

[0004] In view of the above problems, this application provides a secondary battery cell, a secondary battery, and an electrical device that can reduce the DCR of a large-capacity battery, thereby improving the energy efficiency of the battery.

[0005] In a first aspect, this application provides a secondary battery cell, wherein the capacity C of the secondary battery cell satisfies C≥300Ah; and the width W and height H of the secondary battery cell satisfy: 1≤W / H≤2;

[0006] The secondary battery cell includes an electrode sheet, which includes a body and a tab. The first direction is perpendicular to the extension surface of the body. When projected in the first direction X, the relationship between the distance M between the center line of the tab and the edge of the body away from the tab and the length D of the body satisfies: 0.6≤M / D≤0.85.

[0007] The electrode includes a positive electrode, and the positive electrode active material of the positive electrode includes a V-doped lithium phosphate material, wherein the weight percentage of the V element in the positive electrode active material is 0.01% to 0.25%.

[0008] Large-capacity secondary battery cells with a capacity C of 300Ah or more typically have a large overall volume and a long distance between the tabs and the farthest point of each electrode, resulting in a long electron transport path and uneven current density. However, in the technical solution of this application embodiment, by controlling the ratio of the width W to the height H of the secondary battery cell to be within the range of 1 to 2, the distance between the tabs and the farthest point of each electrode is shortened, the electron transport path is shortened, and thus the uneven current density can be improved. Simultaneously, by controlling the ratio of the distance M between the centerline of the electrode and the edge of the body furthest from the electrode to the length D of the body within the range of 0.6 to 0.85, the position of the electrode can be controlled. This ensures that the two electrodes with opposite charges maintain a certain distance while shortening the distance between the electrode and the farthest end of the body. This achieves low interference between the positive and negative electrodes while shortening the electron transport path. However, poor ion conduction performance still exists, resulting in significant polarization in large-capacity secondary battery cells. Therefore, using V-doped lithium phosphate material as the positive electrode active material, leveraging its excellent ion conduction performance, reduces the polarization of the secondary battery cell, thereby improving the battery's DCR. In summary, by synergistically controlling the ratio of the width W to the height H of the secondary battery cell, controlling the electrode placement, and controlling the selection of active materials, large-capacity batteries with a capacity of not less than 300Ah can achieve a low DCR, thus improving the battery's energy efficiency.

[0009] In some embodiments, the V element accounts for 0.1% to 0.2% of the weight of the positive electrode active material.

[0010] In the above implementation process, by controlling the weight ratio of V element in the positive electrode active material to be 0.1% to 0.2%, the secondary battery cell can achieve better ion conduction and energy density.

[0011] In some embodiments, the secondary battery cell includes an electrode terminal. Projected in the first direction X, the relationship between the distance K between the center line of the electrode terminal and the center line of the tab and the length D of the body satisfies: 0 ≤ K / D ≤ 0.12.

[0012] In the above implementation process, the smaller the distance K between the center line of the electrode terminal and the center line of the tab, the smaller the transmission resistance of electrons between the tab and the electrode terminal, which is more conducive to reducing the DCR of the battery. By controlling the ratio of the distance K between the center line of the electrode terminal and the center line of the tab to the length D of the body to be below 0.12, the battery can have a lower DCR.

[0013] In some embodiments, the body is connected to at least one of the tabs, and the lead-out position of the tab faces the end cap of the secondary battery cell.

[0014] In the above implementation process, by setting a corresponding tab on each body and making the lead-out position of the tab face the end cap, it is beneficial to shorten the electron transport path and thus reduce the DCR of the battery.

[0015] In some embodiments, the positive electrode active material comprises large particles and small particles.

[0016] In the above implementation process, small-particle positive electrode active materials are beneficial to shortening the ion transport path. By using small-particle positive electrode active materials, the DCR of the battery can be improved. At the same time, by using a combination of large-particle and small-particle positive electrode active materials, the compaction density of the positive electrode active material layer can be improved, which in turn is beneficial to the energy density.

[0017] In some embodiments, the average particle size is 100 nm to 300 nm; and / or

[0018] The average particle size of the large particles is 1.5 μm to 5 μm.

[0019] In the above implementation process, by controlling the average particle size of the small particles to be 100nm to 300nm, the battery can have a lower DCR.

[0020] In some embodiments, the width W of the secondary battery cell satisfies: 300mm ≤ W ≤ 400mm, and the height H of the secondary battery cell satisfies: 190mm ≤ H ≤ 300mm; and / or

[0021] The width of the electrode tab is 40mm to 110mm.

[0022] In some embodiments, the lithium phosphate material includes LiMPO4, M includes Fe and non-Fe elements, and the non-Fe elements include one or both of a first doping element and a second doping element, wherein the first doping element is an iron site doping and the second doping element is a phosphorus site doping.

[0023] Optionally, the first doping element includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Mn, Ni, Co, Ga, Sn, Sb, Nb, and Ge;

[0024] Optionally, the first doping element includes at least two of Mn, Ti, V, Ni, Co, and Mg;

[0025] Optionally, the second doping element includes one or more elements selected from B, S, Si, and N.

[0026] In some embodiments, the body includes a current collector, the current collector including a current collector body and a base coating, the base coating being attached to the current collector body.

[0027] In the above implementation process, by using a current collector with a base coating, the battery DCR is improved by utilizing its better conductivity.

[0028] In some embodiments, the relationship between the thickness H1 of the base coating and the thickness H2 of the current collector satisfies: 3% ≤ H1 / H2 ≤ 15%.

[0029] In the above implementation process, the thicker the base coating, the more beneficial it is to reduce the DCR of the battery, and the thinner the base coating, the more beneficial it is to the energy density of the battery. By controlling the ratio of the thickness H1 of the base coating to the thickness H2 of the current collector to 3% to 15%, the DCR and energy density of the battery can be well balanced.

[0030] Secondly, this application provides a secondary battery, which includes the secondary battery cell provided in the first aspect.

[0031] Thirdly, this application provides an electrical device, which includes a secondary battery cell provided in the first aspect or a secondary battery provided in the second aspect. Attached Figure Description

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0033] Figure 1 is a structural schematic diagram of a vehicle provided in some embodiments of this application;

[0034] Figure 2 is an exploded structural diagram of a secondary battery provided in some embodiments of this application;

[0035] Figure 3 is a schematic diagram of the structure of a secondary battery cell provided in some embodiments of this application;

[0036] Figure 4 is an exploded view of a secondary battery cell provided in some embodiments of this application;

[0037] Figure 5 is a schematic diagram showing the position arrangement of the tabs and electrode terminals provided in some embodiments of this application;

[0038] Figure 6 is a schematic diagram of the first structure of the positive electrode sheet provided in some embodiments of this application;

[0039] Figure 7 is a schematic diagram of the second structure of the positive electrode sheet provided in some embodiments of this application.

[0040] The reference numerals in the detailed embodiments are as follows:

[0041] 1000 - Vehicle; 100 - Secondary battery; 200 - Motor; 300 - Controller; 10 - Housing; 11 - Accommodation space; 12 - First part; 13 - Second part; 20 - Secondary battery cell; 21 - Shell; 211 - Opening; 22 - End cap assembly; 221 - End cap; 222 - Electrode terminal; 23 - Electrode assembly; 231 - Positive electrode; 231a - Body; 231b - Tab; 2311 - Positive current collector; 2312 - Positive active material layer; 232 - Negative electrode; 24 - Current collector component; 25 - Insulation protection component. Detailed Implementation

[0042] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0044] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0046] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0047] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0048] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0049] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0050] Currently, judging from market trends, the application of power batteries is becoming increasingly widespread. Power batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of power battery applications, market demand is also constantly increasing.

[0051] Power batteries can be lithium-ion rechargeable batteries, which are widely used in portable electronic devices, electric vehicles, and other fields. Currently, the energy storage battery industry is trending towards larger sizes and greater capacities. Generally, increasing battery size increases the electron transport path from the electrodes to the tabs and also exacerbates the unevenness of current density, leading to a deterioration in the battery's current density response (DCR) and a reduction in energy efficiency.

[0052] Based on the above considerations, in order to reduce the DCR of large-capacity batteries, this application proposes a secondary battery cell with a capacity C satisfying C≥300Ah; a width W and a height H satisfying: 1≤W / H≤2; the secondary battery cell includes an electrode, which includes a body and a tab, with a first direction perpendicular to the extension surface of the body. Projected in the first direction X, the relationship between the distance M between the center line of the tab and the edge of the body away from the tab and the length D of the body satisfies: 0.6≤M / D≤0.85; the electrode includes a positive electrode, and the positive active material of the positive electrode includes a V-doped lithium phosphate material, wherein the weight percentage of V in the positive active material is 0.01% to 0.25%.

[0053] Large-capacity rechargeable battery cells with a capacity C of 300Ah or higher typically have a large overall volume and a long distance between the tabs and the farthest point of each electrode, resulting in a long electron transport path and uneven current density. This solution shortens the distance between the tabs and the farthest point of each electrode by controlling the ratio of the width W to the height H of the rechargeable battery cell within the range of 1 to 2, thus shortening the electron transport path and improving the uneven current density, thereby reducing the battery's current density (DCR). Simultaneously, by controlling the ratio of the distance M between the centerline of the tab and the edge of the battery body furthest from the tab to the length D of the battery body within the range of 0.6 to 0.85, the position of the tabs can be controlled. This allows for both low interference between the positive and negative tabs and shortened electron transport paths, further reducing the battery's DCR. Furthermore, by using a V-doped lithium phosphate material as the positive electrode active material, its excellent ion-conducting properties are utilized to reduce the polarization of the rechargeable battery cell and improve the battery's DCR. In summary, by employing a coordinated approach that controls the ratio of the width W to the height H of the secondary battery cell, the placement of the tabs, and the selection of active materials, large-capacity batteries with a capacity of not less than 300Ah can achieve a low DCR, thereby improving the battery's energy efficiency.

[0054] The secondary battery cell can be used, but is not limited to, in electrical equipment such as vehicles, ships, or aircraft. The power system of such electrical equipment can be composed of the secondary battery disclosed in this application.

[0055] This application provides an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0056] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device according to an embodiment of this application.

[0057] Please refer to Figure 1, which is a structural schematic diagram of a vehicle provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. A secondary battery 100 is installed inside the vehicle 1000, and the secondary battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The secondary battery 100 can be used to power the vehicle 1000; for example, the secondary battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 300 and a motor 200. The controller 300 is used to control the secondary battery 100 to supply power to the motor 200, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0058] In some embodiments of this application, the secondary battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0059] In this application, the secondary battery 100 can refer to a single secondary battery cell 20, or it can refer to a single physical module comprising multiple secondary battery cells 20 to provide higher voltage and capacity, which can be in the form of a battery pack, battery module, etc. The secondary battery 100 may include a housing 10 for encapsulating multiple secondary battery cells 20, and the housing 10 can prevent liquids or other foreign objects from affecting the charging or discharging of the secondary battery cells 20.

[0060] Figure 2 is an exploded structural diagram of a secondary battery 100 provided in some embodiments of this application. Referring to Figure 2, the secondary battery 100 includes a housing 10 and a secondary battery cell 20, with the secondary battery cell 20 housed within the housing 10.

[0061] The housing 10 provides a receiving space 11 for the secondary battery cell 20. In some embodiments, the housing 10 may include a first portion 12 and a second portion 13, which overlap each other to define the receiving space 11 for accommodating the secondary battery cell 20. Of course, the connection between the first portion 12 and the second portion 13 can be sealed by a sealant (not shown), such as a sealing ring, sealant, etc.

[0062] The first part 12 and the second part 13 can be of various shapes, such as cuboids, cylinders, etc. The first part 12 can be a hollow structure with one side open to form a cavity for accommodating the secondary battery cell 20, and the second part 13 can also be a hollow structure with one side open to form a cavity for accommodating the secondary battery cell 20. The opening side of the second part 13 covers the opening side of the first part 12, thus forming a box 10 with a accommodating space 11. Of course, as shown in Figure 2, the first part 12 can also be a hollow structure with one side open, and the second part 13 can be a plate-like structure. The second part 13 covers the opening side of the first part 12, thus forming a box 10 with a accommodating space 11.

[0063] In the secondary battery 100, there can be one or more secondary battery cells 20. If there are multiple secondary battery cells 20, they can be connected in series, in parallel, or in a mixed manner. A mixed connection means that multiple secondary battery cells 20 are connected in both series and parallel. Multiple secondary battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then the whole formed by the multiple secondary battery cells 20 is housed in the housing 10. Alternatively, multiple secondary battery cells 20 can first be connected in series, in parallel, or in a mixed manner to form a battery module, and then multiple battery modules can be connected in series, in parallel, or in a mixed manner to form a whole, which is then housed in the housing 10. The secondary battery cell 20 can be cylindrical, flat, cuboid, or other shapes. Figure 2 illustrates an example of a square secondary battery cell 20.

[0064] In some embodiments, the secondary battery 100 may further include a busbar (not shown), and multiple secondary battery cells 20 may be electrically connected through the busbar to realize the series, parallel or mixed connection of multiple secondary battery cells 20.

[0065] Figure 3 is a schematic diagram of the structure of a secondary battery cell 20 provided in some embodiments of this application, and Figure 4 is an exploded view of a secondary battery cell 20 provided in some embodiments of this application. Referring to Figures 3 and 4, the secondary battery cell 20 may include a housing 21, an end cap assembly 22, and an electrode assembly 23. The housing 21 has an opening 211, the electrode assembly 23 is accommodated within the housing 21, and the end cap assembly 22 is used to seal the opening 211.

[0066] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a cuboid structure, the housing 21 can also be a cuboid structure. Figures 3 and 4 exemplarily show the case where the housing 21 and the electrode assembly 23 are square.

[0067] The outer shell 21 can also be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc. This application embodiment does not impose any special restrictions on this.

[0068] The end cap assembly 22 includes an end cap 221 and electrode terminals 222. The end cap assembly 22 is used to seal the opening 211 of the housing 21 to form a sealed mounting space (not shown) for accommodating the electrode assembly 23. The mounting space also accommodates an electrolyte, such as an electrolyte solution. As a component that outputs electrical energy to the electrode assembly 23, the end cap assembly 22 has electrode terminals 222 for electrical connection to the electrode assembly 23, specifically, the electrode terminals 222 are electrically connected to the tabs of the electrode assembly 23. For example, the electrode terminals 222 and the tabs are connected via a current collector 24 to achieve the electrical connection between the electrode terminals 222 and the tabs.

[0069] It should be noted that the opening 211 of the outer casing 21 can be one or two. If the outer casing 21 has one opening 211, the end cap assembly 22 can also be one, and two electrode terminals 222 can be provided in the end cap assembly 22. The two electrode terminals 222 are used to electrically connect to the positive electrode tab and the negative electrode tab of the electrode assembly 23, respectively. If the outer casing 21 has two openings 211, for example, the two openings 211 are located on opposite sides of the outer casing 21, the end cap assembly 22 can also be two, and the two end cap assemblies 22 respectively cover the two openings 211 of the outer casing 21. In this case, the electrode terminal 222 in one end cap assembly 22 can be a positive electrode terminal, used to electrically connect to the positive electrode tab of the electrode assembly 23; the electrode terminal 222 in the other end cap assembly 22 can be a negative electrode terminal, used to electrically connect to the negative electrode plate 231 of the electrode assembly 23.

[0070] In some embodiments, as shown in FIG4, the secondary battery cell 20 may further include an insulating protective member 25 fixed to the outer periphery of the electrode assembly 23. The insulating protective member 25 is used to insulate and isolate the electrode assembly 23 from the housing 21. Exemplarily, the insulating protective member 25 is an adhesive tape bonded to the outer periphery of the electrode assembly 23. In some embodiments, there are multiple electrode assemblies 23, and the insulating protective member 25 surrounds the outer periphery of multiple electrode assemblies 23, forming multiple electrode assemblies 23 into an integral structure to maintain the structural stability of the electrode assembly 23.

[0071] The electrode assembly 23 includes a positive electrode 231, a negative electrode 231, and a separator. The electrode assembly 23 can be a wound electrode assembly 23 or a stacked electrode assembly 23, and the embodiments of this application are not limited thereto.

[0072] The positive electrode 231 includes a positive current collector 2311 and a positive active material layer 2312. The positive active material layer 2312 is coated on the surface of the positive current collector 2311. The positive current collector 2311 without the positive active material layer 2312 protrudes from the positive current collector 2311 with the positive active material layer 2312 coated. The positive current collector 2311 without the positive active material layer 2312 coated serves as the positive electrode tab.

[0073] In some embodiments, the positive current collector 2311 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 substrate 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 (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.).

[0074] In some embodiments, when the secondary battery 100 is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811At least one of lithium nickel cobalt aluminum oxides and their modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0075] In some embodiments, the positive electrode active material layer 2312 may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0076] In some embodiments, the positive electrode active material layer 2312 may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0077] In some embodiments, the positive electrode 231 can be prepared by dispersing the components used to prepare the positive electrode 231, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g. N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive current collector 2311, and after drying, cold pressing and other processes, the positive electrode 231 can be obtained.

[0078] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. The negative electrode current collector without the negative electrode active material layer protrudes from the negative electrode current collector with the negative electrode active material layer. The negative electrode current collector without the negative electrode active material layer serves as the negative electrode tab.

[0079] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric 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 polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0080] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0081] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0082] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0083] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0084] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0085] In other embodiments, the current collector of the negative electrode sheet may also include a current collector body and a base coating. The base coating may be disposed on at least one side of the current collector body. The base coating basically does not contain negative electrode active material, but may contain a small amount of carbon material. However, the carbon material forms a thin coating and cannot function as a negative electrode active material. In this embodiment, the negative electrode sheet can be an electrode sheet without a negative electrode active material layer. For a negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not contain a base coating, the film layer of the negative electrode sheet can be disposed on the surface of at least one side of the current collector body; when the current collector of the negative electrode sheet includes a base coating, the film layer of the negative electrode sheet can be disposed on the surface of the base coating away from the current collector body.

[0086] In some implementations, in order to ensure that a large current can pass through without melting, there are multiple positive electrode tabs stacked together, and multiple negative electrode tabs stacked together.

[0087] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0088] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0089] The electrolyte acts as a conductor of ions between the positive electrode 231 and the negative electrode. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0090] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0091] In some embodiments, the electrolyte salt may 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0092] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0093] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0094] This application provides a secondary battery cell with a capacity C that satisfies C≥300Ah; and a width W and height H that satisfy: 1≤W / H≤2.

[0095] The secondary battery cell includes an electrode sheet, which includes a body and a tab. The first direction is perpendicular to the extension surface of the body. Referring to Figure 5, when projected in the first direction X, the relationship between the distance M between the center line of the tab and the edge of the body away from the tab and the length D of the body satisfies: 0.6≤M / D≤0.85.

[0096] The electrode includes a positive electrode, and the positive electrode active material of the positive electrode includes a V-doped lithium phosphate material, wherein the weight percentage of the V element in the positive electrode active material is 0.01% to 0.25%.

[0097] The capacity refers to the actual tested capacity. The test method is as follows: under normal pressure at 25℃, the secondary battery cell is discharged to 2.5V at a constant power of 0.5P, left to stand for 30 minutes, then charged to 3.65V at a constant power of 0.5P, left to stand for 30 minutes, and then discharged to 2.5V at a constant power of 0.5P. The discharge capacity C0 at this time is recorded, which is the actual measured capacity of the secondary battery cell.

[0098] Both negative and positive electrode sheets are types of electrodes with similar structures. An electrode typically includes a current collector and an active material layer, with the active material layer attached to the current collector. The current collector can be either a positive current collector 2311 or a negative current collector, and the corresponding active material layer can be either a positive active material layer 2312 or a negative active material layer. The active material layer can be attached to either one side of the current collector or both sides simultaneously. Since the negative and positive electrode sheets have similar structures, the following description focuses on the positive electrode 231. Please refer to Figure 6. In one embodiment, a positive active material layer 2312 is disposed on one surface of the positive current collector 2311. Please refer to Figure 7. In another embodiment, a positive active material layer 2312 is disposed on both surfaces of the positive current collector 2311.

[0099] The height of a secondary battery cell refers to its length parallel to the direction of electrode terminal extension. The thickness of a secondary battery cell refers to its length along the electrode stacking direction. The width of a secondary battery cell refers to its length along the large surface area, perpendicular to both the thickness and height directions.

[0100] The distance M between the centerline of the electrode and the edge of the body furthest from the electrode refers to the greater distance between the centerline of the electrode and the two adjacent edges of the body where the electrode is located. More specifically, the body includes four edges connected end to end, namely the first edge, the second edge, the third edge, and the fourth edge. The electrode is located on the second edge. In this case, the distance M between the centerline of the electrode and the edge of the body furthest from the electrode refers to the greater distance between the centerline of the electrode and the first edge and the third edge.

[0101] Lithium-containing phosphate materials can be lithium iron phosphate materials or active materials with similar or identical structures to lithium iron phosphate materials. V-doped lithium-containing phosphate materials refer to lithium-containing phosphate materials in which at least part of the iron sites are occupied by V.

[0102] Large-capacity secondary battery cells with a capacity C of 300Ah or more typically have a large overall volume and a long distance between the tabs and the farthest point of each electrode, resulting in a long electron transport path and uneven current density. However, in the technical solution of this application embodiment, by controlling the ratio of the width W to the height H of the secondary battery cell to be within the range of 1 to 2, the distance between the tabs and the farthest point of each electrode is shortened, the electron transport path is shortened, and thus the uneven current density can be improved. Simultaneously, by controlling the ratio of the distance M between the centerline of the electrode and the edge of the body furthest from the electrode to the length D of the body within the range of 0.6 to 0.85, the position of the electrode can be controlled. This ensures that the two electrodes with opposite charges maintain a certain distance while shortening the distance between the electrode and the farthest end of the body. This achieves low interference between the positive and negative electrodes while shortening the electron transport path. However, poor ion conduction performance still exists, resulting in significant polarization in large-capacity secondary battery cells. Therefore, using V-doped lithium phosphate material as the positive electrode active material, leveraging its excellent ion conduction performance, reduces the polarization of the secondary battery cell, thereby improving the battery's DCR. In summary, by synergistically controlling the ratio of the width W to the height H of the secondary battery cell, controlling the electrode placement, and controlling the selection of active materials, large-capacity batteries with a capacity of not less than 300Ah can achieve a low DCR, thus improving the battery's energy efficiency.

[0103] Those skilled in the art will understand that the larger the capacity of a single secondary battery cell, for example, a capacity of not less than 500Ah, not less than 600Ah (which is conventionally considered to be twice the capacity of a large-capacity secondary battery cell), not less than 700Ah, not less than 800Ah, etc., the larger the overall battery volume, the farther the distance from the tabs to the farthest point in each electrode, the longer the electron transport path, resulting in more uneven current density, which in turn leads to more serious problems. However, once the problems of larger-capacity secondary battery cells can be solved, the problems of smaller-capacity secondary battery cells can naturally be solved as well.

[0104] For example, the capacity C of a single secondary battery cell can be 300Ah, 350Ah, 400Ah, 450Ah, 500Ah, 550Ah, 600Ah, 650Ah, or 700Ah, or any value within the range of ≥300Ah. The ratio W / H of the width W and height H of the single secondary battery cell can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2, or any value within the range of 1 to 2. The ratio M / D of the distance M between the center line of the electrode tab and the edge of the body away from the electrode tab and the length D of the body can be 0.6, 0.65, 0.7, 0.75, 0.8, or 0.85, or any value within the range of 0.6 to 0.85. The weight percentage of V in the positive electrode active material can be 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, or 0.25%, or any value within the range of 0.01% to 0.25%.

[0105] In the technical solution of this application embodiment, the weight percentage of V element in the positive electrode active material is 0.1% to 0.2%. By controlling the weight percentage of V element in the positive electrode active material to be 0.1% to 0.2%, the secondary battery cell can achieve better ion conduction and energy density.

[0106] In the technical solution of this application embodiment, the secondary battery cell includes electrode terminals. Referring to Figure 5, projected in the first direction X, the relationship between the distance K between the center line of the electrode terminal and the center line of the tab and the length D of the body satisfies: 0 ≤ K / D ≤ 0.12. The smaller the distance K between the center line of the electrode terminal and the center line of the tab, the smaller the electron transfer resistance between the tab and the electrode terminal, which is more conducive to reducing the DCR of the battery. By controlling the ratio of the distance K between the center line of the electrode terminal and the center line of the tab to the length D of the body to be below 0.12, the battery has a lower DCR.

[0107] For example, the ratio K / D of the distance K between the center line of the electrode terminal and the center line of the tab to the length D of the body can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11 or 0.12, etc., or any value in the range of 0 to 0.12.

[0108] In the technical solution of this application embodiment, the body is connected to at least one of the tabs, and the lead-out position of the tab faces the end cap of the secondary battery cell. It should be noted that when the electrode assembly of the secondary battery cell is a wound electrode assembly, "at least one tab connected to the body" means that each layer of the body is connected to at least one tab. By providing a tab on each body and having the lead-out position of the tab face the end cap, it is beneficial to shorten the electron transport path, thereby reducing the battery's DCR.

[0109] In the technical solution of this application embodiment, the positive electrode active material includes large particles and small particles. Small particles of positive electrode active material are beneficial for shortening the ion transport path. By using small particles of positive electrode active material, the DCR of the battery can be improved. At the same time, by using a combination of large and small particles of positive electrode active material, the compaction density of the positive electrode active material layer can be improved, thereby improving the energy density.

[0110] Furthermore, the average particle size of the small particles is 100 nm to 300 nm; the average particle size of the large particles is 1.5 μm to 5 μm. By controlling the average particle size of the small particles to be 100 nm to 300 nm, the battery can have a lower DCR.

[0111] The particle size test for small particles in the electrode sheet can be performed as follows: Take an electrode sheet and perform SEM analysis on the ion-polished cross-section. Randomly select 5 fields of view and magnify the views to 10,000 times. Divide the field of view into large and small particles with a 1μm boundary, i.e., particles smaller than 1μm are defined as small particles, and particles larger than 1μm are defined as large particles. Randomly select 10 small particles in each field of view and measure the distance between the two furthest points, recording them as particle size values ​​d1, d2, ... A total of 50 particle size values ​​can be obtained. Take the average value, which is recorded as the average particle size of the small particles. Similarly, the particle size test method for large particles can refer to the above method for small particle particle size testing.

[0112] For example, the average particle size of the small particles can be 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm or 300nm, etc., or it can be any value in the range of 100nm to 300nm.

[0113] In the technical solution of this application embodiment, the body includes a current collector, which includes a current collector body and a base coating layer, the base coating layer being attached to the current collector body. By using a current collector with a base coating layer, its better conductivity is utilized to improve the battery's direct current carrying capacity (DCR).

[0114] Furthermore, the relationship between the thickness H1 of the base coating and the thickness H2 of the current collector satisfies: 3% ≤ H1 / H2 ≤ 15%. Generally, the thickness of the base coating is positively correlated with the amount of base coating material used. A thicker base coating is more beneficial for reducing the battery's DCR, while a thinner base coating is more beneficial for the battery's energy density. By controlling the ratio of the thickness H1 of the base coating to the thickness H2 of the current collector to 3%–15%, a good balance between the battery's DCR and energy density can be achieved.

[0115] For example, the ratio of the thickness H1 of the base coating to the thickness H2 of the current collector can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, etc., or it can be any value in the range of 3% to 15%.

[0116] In the technical solution of this application embodiment, the lithium phosphate material includes LiMPO4, and M includes Fe and non-Fe elements.

[0117] It should be noted that the above LiMPO4 is not a specific molecular structure formula, but a general expression of lithium iron phosphate.

[0118] In some embodiments of this application, the non-Fe element includes one or both of a first doping element and a second doping element, wherein the first doping element is an iron site doping element and the second doping element is a phosphorus site doping element.

[0119] In some embodiments of this application, the first doping element includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge.

[0120] In some embodiments of this application, the first doping element includes at least two of Mn, Ti, V, Ni, Co, and Mg.

[0121] In some embodiments of this application, the second doping element includes one or more elements selected from B, S, Si, and N.

[0122] In some embodiments of this application, the lithium phosphate material includes Li1+xFe1-yAyP1-zRzO4, where x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, and z is any value in the range of 0.001 to 0.100. The A includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Mn, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and the R includes one or more elements selected from B, S, Si, and N.

[0123] In some embodiments of this application, the preparation method of compound Li1+xFe1-yAyP1-zRzO4 may include the following steps:

[0124] (1) Dissolve and stir the iron source, the iron site doped element A source and acid in a solvent to generate a suspension of iron salt doped with element A. Filter the suspension and dry the filter cake to obtain iron salt doped with element A.

[0125] (2) The lithium source, phosphorus source, element R source, solvent and iron salt doped with element A obtained in step (1) are added to the reaction vessel, ground and mixed to obtain a slurry;

[0126] (3) The slurry obtained in step (2) is transferred to a spray drying equipment for spray drying and granulation to obtain granules;

[0127] (4) The particles obtained in step (3) are sintered to obtain the positive electrode active material.

[0128] In any embodiment, the iron source may be an iron-containing substance known in the art that can be used to prepare lithium iron phosphate, such as one or a combination of elemental iron, ferrous oxide, ferric phosphate, ferric oxalate, and ferric carbonate.

[0129] The acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and organic acids such as oxalic acid, for example, oxalic acid. The source of element R is selected from at least one of sulfates, borates, nitrates, and silicates of element R. The source of element A is selected from at least one of the elemental form, oxide, phosphate, oxalate, carbonate, and sulfate of A.

[0130] In some embodiments of this application, the lithium phosphate material includes Li a A e Fe 1-f B f P 1-g C g O 4-n D nThe lithium phosphate material is wherein A comprises one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B comprises one or more elements selected from Ti, V, Zr, Mn, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C comprises one or more elements selected from B, S, Si, and N; D comprises one or more elements selected from S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1; e is selected from the range of 0.001 to 0.1; f is selected from the range of 0.001 to 0.5; g is selected from the range of 0.001 to 0.1; n is selected from the range of 0.001 to 0.1; and the lithium phosphate material is electrically neutral.

[0131] It should be noted that Li a A e Fe 1-f B f P 1-g C g O 4-n D n The compound is actually a specific LiMPO4 material. Its preparation method can be found in the Li... 1+x Fe 1-y A y P 1-z R z O4 is not specified here.

[0132] The following uses Li 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001 The preparation process is further explained as follows: 1. Preparation of doped material: 1.3 mol of MnSO4·H2O and 0.7 mol of FeSO4·H2O were thoroughly mixed in a mixer for 6 hours. The mixture was transferred to a reaction vessel, and 10 L of deionized water and 2 mol of oxalic acid dihydrate (calculated as oxalic acid) were added. The reaction vessel was heated to 80°C and stirred at 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated), resulting in a doped suspension. The suspension was then filtered, and the filter cake was dried at 120°C and then ground to obtain the median particle size Dv. 50 The doped particles are approximately 100 nm in size. 2. Preparation of Li 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.0011 mol of the above-mentioned doped particles, 0.497 mol of lithium carbonate, 0.001 mol of Mo(SO4)3, an 85% phosphoric acid aqueous solution containing 0.999 mol of phosphoric acid, 0.001 mol of H4SiO4, 0.0005 mol of NH4HF2, and 0.005 mol of sucrose were added to 20 L of deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was then transferred to a spray drying equipment for spray drying granulation. The drying temperature was set at 250°C and the drying time was 4 hours to obtain granules. Under a protective atmosphere of nitrogen (90 vol%) + hydrogen (10 vol%), the above powder was sintered at 700°C for 10 hours to obtain carbon-coated Li. 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001 .

[0133] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery. The Li content in the positive electrode varies depending on the state of discharge. The Li content can be measured in molar content, but is not limited to this. Simultaneously, when a positive electrode material is applied to the positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. In the examples of positive electrode materials listed in this application, unless otherwise specified, the Li content refers to the initial state of the material. Regarding "Li content refers to the initial state of the material," the initial state refers to the state before the material is added to the positive electrode slurry or the state after the battery is fully discharged within a specified charge-discharge range (at which point lithium ions are intercalated into the positive electrode as much as possible). It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0134] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0135] In the technical solution of this application embodiment, the width W of the secondary battery cell satisfies: 300mm≤W≤400mm, and the height H of the secondary battery cell satisfies: 190mm≤H≤300mm.

[0136] For example, the width W of the secondary battery cell can be 300mm, 305mm, 310mm, 315mm, 320mm, 325mm, 330mm, 335mm, 340mm, 345mm, 350mm, 355mm, 360mm, 365mm, 370mm, 375mm, 380mm, 385mm, 390mm, 395mm or 400mm, etc., or it can be any value in the range of 300mm to 400mm. The height H of a single secondary battery cell can be 190mm, 195mm, 200mm, 205mm, 210mm, 215mm, 220mm, 225mm, 230mm, 235mm, 240mm, 245mm, 250mm, 255mm, 260mm, 265mm, 270mm, 275mm, 280mm, 285mm, 290mm, 295mm, or 300mm, or any value within the range of 190mm to 300mm.

[0137] In the technical solution of this application embodiment, the width of the electrode tab is 40mm to 110mm.

[0138] The following examples will describe one or more embodiments in more detail. Of course, these examples do not limit the scope of the one or more embodiments.

[0139] Examples and Comparative Examples

[0140] Preparation of the positive electrode sheet

[0141] Lithium iron phosphate positive electrode active material, polyvinylidene fluoride binder, and acetylene black conductive agent are mixed in a weight ratio of 97:2:1 and dissolved in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The slurry is then coated onto a current collector aluminum foil, dried, and subjected to cold pressing, edge trimming, cutting, and slitting to produce a positive electrode sheet.

[0142] Preparation of the negative electrode sheet

[0143] The negative electrode active material graphite, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na), and conductive agent carbon black (Super P) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The slurry is then coated onto the current collector copper foil, dried, and then cold-pressed, trimmed, cut, and slit to obtain the negative electrode sheet.

[0144] Preparation of Electrolyte

[0145] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, thoroughly dried LiPF6 was dissolved in this organic solvent to obtain an electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0146]

Isolation Film

[0147] Porous polyethylene film is used as the separator.

[0148] Preparation of secondary battery cells

[0149] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery cell is obtained.

[0150] The main parameter controls for each embodiment and comparative example are shown in the table below:

[0151] The secondary battery cells provided in each embodiment and comparative example were tested, including:

[0152] Energy efficiency test method: Under normal temperature and pressure, the battery cell is discharged to 2.5V at a constant power of 0.5P and left to stand for 30 minutes; then it is charged to 3.65V at a constant power of 0.5P, and the charging energy E1 is recorded, and left to stand for 30 minutes; then it is discharged to 2.5V at a constant power of 0.5P and the discharge energy E2 is recorded. The energy efficiency of the battery cell at a 0.5P rate is calculated as E2 / E1*100%.

[0153] The test results are shown in the table below:

[0154] As can be seen from the table above, the secondary battery cell provided in the embodiments of this application has high energy efficiency.

[0155] By comparing the data from Examples 1 to 3 and Comparative Examples 3 to 4, it can be seen that as the ratio of the width W to the height H of the secondary battery cell gradually increases, the energy efficiency of the secondary battery cell shows a trend of first increasing and then decreasing. By controlling the ratio of the width W to the height H of the secondary battery cell to be between 1 and 2, the energy efficiency of the secondary battery cell is above 93.7%.

[0156] By comparing the data from Examples 1, 4 to 5, and Comparative Examples 1 to 2, it can be seen that as the ratio of the distance M between the center line of the electrode and the edge of the body away from the electrode to the length D of the body gradually decreases, the energy efficiency of the secondary battery cell shows a trend of first increasing and then decreasing. By controlling the ratio of the distance M between the center line of the electrode and the edge of the body away from the electrode to the length D of the body to be between 0.6 and 0.85, the energy efficiency of the secondary battery cell is above 94.3%.

[0157] By comparing the data from Examples 1, 6 to 9 and Comparative Examples 5 to 6, it can be seen that as the weight percentage of V in the positive electrode active material gradually increases, the energy efficiency of the secondary battery cell shows a trend of first increasing and then decreasing. By controlling the weight percentage of V in the positive electrode active material to be between 0.01% and 0.25%, the energy efficiency of the secondary battery cell is above 93.5%.

[0158] By comparing the data from Examples 1 and 10 to 11, it can be seen that as the ratio of the distance K between the center line of the electrode terminal and the center line of the tab to the length D of the body gradually increases, the energy efficiency of the secondary battery cell shows a gradual decreasing trend. By controlling the ratio of the distance K between the center line of the electrode terminal and the center line of the tab to the length D of the body to be below 0.12, the energy efficiency of the secondary battery cell is above 93.6%.

[0159] The above are merely specific embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A secondary battery cell, characterized in that, The capacity C of the secondary battery cell satisfies C≥300Ah; the width W and height H of the secondary battery cell satisfy: 1≤W / H≤2; The secondary battery cell includes an electrode sheet, which includes a body and a tab. The first direction is perpendicular to the extension surface of the body. When projected in the first direction X, the relationship between the distance M between the center line of the tab and the edge of the body away from the tab and the length D of the body satisfies: 0.6≤M / D≤0.

85. The electrode includes a positive electrode, and the positive electrode active material of the positive electrode includes a V-doped lithium phosphate material, wherein the weight percentage of the V element in the positive electrode active material is 0.01% to 0.25%.

2. The secondary battery cell according to claim 1, characterized in that, The V element accounts for 0.1% to 0.2% of the weight of the positive electrode active material.

3. The secondary battery cell according to any one of claims 1 to 2, characterized in that, The secondary battery cell includes electrode terminals. When projected in the first direction X, the relationship between the distance K between the center line of the electrode terminal and the center line of the tab and the length D of the body satisfies: 0 ≤ K / D ≤ 0.

12.

4. The secondary battery cell according to any one of claims 1 to 3, characterized in that, The body is connected to at least one of the tabs, and the lead-out position of the tab is facing the end cap of the secondary battery cell.

5. The secondary battery cell according to any one of claims 1 to 4, characterized in that, The positive electrode active material includes large particles and small particles.

6. The secondary battery cell according to claim 5, characterized in that, The average particle size of the small particles is 100 nm to 300 nm; and / or The average particle size of the large particles is 1.5 μm to 5 μm.

7. The secondary battery cell according to any one of claims 1 to 6, characterized in that, The width W of the secondary battery cell satisfies: 300mm ≤ W ≤ 400mm, and the height H of the secondary battery cell satisfies: 190mm ≤ H ≤ 300mm; and / or The width of the electrode tab is 40mm to 110mm.

8. The secondary battery cell according to any one of claims 1 to 7, characterized in that, The lithium iron phosphate material includes LiMPO4, where M includes Fe and non-Fe elements. The non-Fe elements include one or both of a first doping element and a second doping element. The first doping element is iron site doping, and the second doping element is phosphorus site doping.

9. The secondary battery cell according to claim 8, characterized in that, The first doping element includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Mn, Ni, Co, Ga, Sn, Sb, Nb, and Ge; and / or The second doping element includes one or more elements selected from B, S, Si, and N.

10. The secondary battery cell according to any one of claims 1 to 9, characterized in that, The body includes a current collector, which includes a current collector body and a base coating, the base coating being attached to the current collector body.

11. The secondary battery cell according to claim 10, characterized in that, The relationship between the thickness H1 of the base coating and the thickness H2 of the current collector satisfies: 3% ≤ H1 / H2 ≤ 15%.

12. A secondary battery, characterized in that, The secondary battery comprises any one of the secondary battery cells according to claims 1 to 11.

13. An electrical appliance, characterized in that, The electrical equipment includes a secondary battery cell as described in any one of claims 1 to 11 or a secondary battery as described in claim 12.

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