WO2024040472A1 - 二次电池、电池模块、电池包和用电装置 - Google Patents

二次电池、电池模块、电池包和用电装置 Download PDF

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Publication number
WO2024040472A1
WO2024040472A1 PCT/CN2022/114517 CN2022114517W WO2024040472A1 WO 2024040472 A1 WO2024040472 A1 WO 2024040472A1 CN 2022114517 W CN2022114517 W CN 2022114517W WO 2024040472 A1 WO2024040472 A1 WO 2024040472A1
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Prior art keywords
positive electrode
negative electrode
piece
secondary battery
width direction
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PCT/CN2022/114517
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English (en)
French (fr)
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毛恒山
李彦朋
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/114517 priority Critical patent/WO2024040472A1/zh
Publication of WO2024040472A1 publication Critical patent/WO2024040472A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of batteries, and specifically to a secondary battery, a battery module, a battery pack and an electrical device.
  • Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic equipment, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools etc.
  • the space occupancy rate of the positive electrode plate in the secondary battery is an important indicator that determines the performance of the secondary battery. Therefore, how to improve the space occupancy rate of the positive electrode plate is an urgent technical issue in battery technology that needs to be solved. .
  • This application was made in view of the above-mentioned problems, and its purpose is to provide a secondary battery, a battery module, a battery pack, and an electrical device.
  • a first aspect of the present application provides a secondary battery.
  • the secondary battery includes a casing assembly and an electrode assembly; the electrode assembly is disposed in the casing assembly, and the electrode assembly includes a positive electrode plate, a negative electrode plate and a positive electrode plate. and the isolation film between the negative electrode piece and the projection of the negative electrode piece along the first direction is located within the projection of the positive electrode piece along the first direction, wherein the first direction is perpendicular to the height direction of the housing assembly.
  • the positive electrode piece has a higher space occupation rate and can fully improve the density of the cathode active material on the positive electrode piece. quality; and can also improve the energy density of secondary batteries.
  • the projection of the negative electrode plate along the first direction overlaps the projection of the positive electrode plate along the first direction.
  • the area of the negative electrode piece of the present application is relatively large and can cover each other with the positive electrode piece, which can further ensure that the metal ions released from the positive electrode piece can be embedded into the negative active material of the negative electrode piece, reducing the precipitation of metal ions. risk on the surface of the negative active material, thereby improving the safety performance of the secondary battery.
  • the size of the negative electrode piece along its own width direction is less than or equal to the size of the positive electrode piece along its own width direction; optionally, the size of the negative electrode piece along its own width direction is A1, and the size of the positive electrode piece along its own width direction is A1.
  • the size along its own width direction is A2, -15mm ⁇ A1-A2 ⁇ -2mm.
  • this application improves the space occupancy rate of the positive electrode piece by regulating the size of the negative electrode piece and the positive electrode piece, thereby increasing the energy density of the secondary battery.
  • the positive electrode piece includes two first edges opposite to each other along its own width direction. From the first edge to the direction of the center line of the positive electrode piece, the gram capacity of the positive electrode piece gradually increases.
  • the gram capacity of the end of the positive electrode piece in the width direction is relatively low, which increases the CB value of the capacity ratio of the ends of the positive and negative electrode pieces, so that the metal vacancies provided by the negative electrode piece can accept more metal ions, thereby It can reduce the risk of metal ions precipitating at the ends of the negative electrode plates to form metal dendrites, and improve the safety performance of secondary batteries.
  • the positive electrode piece includes a first positive electrode part, a second positive electrode part and a positive electrode connection part; the gram capacity of the first positive electrode part is C11; the second positive electrode part and the first positive electrode part are along the width direction of the positive electrode piece Opposite to each other, the gram capacity of the second positive electrode part is C12; and the positive electrode connecting part is disposed between the first positive electrode part and the second positive electrode part and connects the first positive electrode part and the second positive electrode part, and the gram capacity of the positive electrode connecting part is It is C13, and the positive electrode plate meets: 1mAh/g ⁇ C12-C11 ⁇ 500mAh/g; and/or 1mAh/g ⁇ C12-C13 ⁇ 500mAh/g.
  • the gram capacity of the positive electrode connection part is greater than the gram capacity of the first positive electrode part, and the gram capacity of the first positive electrode part is relatively low.
  • the first positive electrode part is located at the center of the positive electrode sheet end, so that the ratio CB value of the capacity at the ends of the positive and negative electrode pieces is increased, so that the metal vacancies provided by the negative electrode pieces can accept more metal ions, thereby reducing the precipitation of metal ions at the ends of the negative electrode pieces.
  • the risk of forming metal dendrites improves the safety performance of secondary batteries.
  • the gram capacity of the positive electrode connection part is greater than the gram capacity of the second positive electrode part, which can reduce the risk of metal ions precipitating and forming metal dendrites at the end of the negative electrode piece, and improve the safety performance of the secondary battery.
  • the first positive electrode portion and the second positive electrode portion have the same size in the width direction of the positive electrode tab.
  • the first positive electrode part and the second positive electrode part are the two ends of the positive electrode plate, and their dynamic properties during the charging and discharging process of the secondary battery are basically the same. Therefore, the width direction of the first positive electrode part and the second positive electrode part is The size is set to be basically the same, which can further ensure the consistency of the overall dynamic performance of the positive electrode piece. Moreover, it is beneficial to the processing and forming of the positive electrode film layer.
  • the first positive electrode part and the second positive electrode part are made of the same material.
  • the reactions that occur during the lithium deintercalation process of the same material are basically the same, which is helpful to further ensure the consistency of the overall dynamic performance of the positive electrode piece. Moreover, it is beneficial to the processing and forming of the positive electrode film layer.
  • the negative electrode piece includes two second edges opposite to each other along its own width direction, with the second edge pointing in the direction of the center line of the negative electrode piece, and the gram capacity of the negative electrode piece shows a gradually decreasing trend.
  • the gram capacity of the end of the negative electrode piece in the width direction is relatively high, which can increase more metal vacancies and accept more metal ions, thus reducing the risk of metal ions precipitating to form metal dendrites at the ends of the negative electrode piece. risk and improve the safety performance of secondary batteries.
  • the negative electrode piece includes a first negative electrode part, a second negative electrode part and a negative electrode connection part; the gram capacity of the first negative electrode part is C21; the second negative electrode part and the first negative electrode part are along the width direction of the negative electrode piece Opposite to each other, the gram capacity of the second negative electrode part is C22; and the negative electrode connecting part is disposed between the first negative electrode part and the second negative electrode part and connects the first negative electrode part and the second negative electrode part, and the gram capacity of the negative electrode connecting part is C23, the negative electrode piece meets: 1mAh/g ⁇ C21-C22 ⁇ 500mAh/g; and/or 1mAh/g ⁇ C23-C22 ⁇ 500mAh/g.
  • the gram capacity of the negative electrode connection part is smaller than the gram capacity of the first negative electrode part, and the gram capacity of the first negative electrode part is relatively high.
  • the first negative electrode part is located between the negative electrode sheet end, so that the ratio CB value of the capacity at the ends of the positive and negative electrode pieces is increased, so that the metal vacancies provided by the negative electrode pieces can accept more metal ions, thereby reducing the precipitation of metal ions at the ends of the negative electrode pieces.
  • the risk of forming metal dendrites improves the safety performance of secondary batteries.
  • the gram capacity of the negative electrode connection part is smaller than the gram capacity of the second negative electrode part, which can reduce the risk of metal ions precipitating and forming metal dendrites at the end of the negative electrode piece, and improve the safety performance of the secondary battery.
  • the first negative electrode portion and the second negative electrode portion have the same size in the width direction of the negative electrode tab.
  • the first negative electrode part and the second negative electrode part are the two ends of the negative electrode piece, and their dynamic properties during the charging and discharging process of the secondary battery are basically the same. Therefore, the width directions of the first negative electrode part and the second negative electrode part are The size is set to be basically the same, which can further ensure the consistency of the overall dynamic performance of the negative electrode piece. Moreover, it is beneficial to the processing and forming of the negative electrode film layer.
  • the first negative electrode part and the second negative electrode part are made of the same material.
  • the reactions that occur during the lithium deintercalation process of the same materials are basically the same, which is helpful to further ensure the consistency of the overall dynamic performance of the negative electrode piece. Moreover, it is beneficial to the processing and forming of the negative electrode film layer.
  • the projection of the positive electrode plate along the first direction is located within the projection of the isolation film along the first direction.
  • the isolation film can cover the positive electrode piece and insulate the positive electrode piece and the negative electrode piece. It can ensure that the ends of the positive electrode piece and the end of the negative electrode piece are basically not in contact, resulting in short circuits and other situations. Improve the safety performance of secondary batteries.
  • the size of the positive electrode piece along its own width direction is less than or equal to the size of the isolation film along its own width direction; optionally, the size of the positive electrode piece along its own width direction is A2, and the size of the isolation film along its own width direction is A2.
  • the size in its own width direction is A3, 0mm ⁇ A3-A2 ⁇ 6mm.
  • the isolation film of the present application can effectively insulate the positive electrode piece and the negative electrode piece in the width direction.
  • the isolation film can effectively isolate the positive electrode piece and the negative electrode piece, reduce the end contact between the two and cause The risk of short circuit further improves the safety performance of secondary batteries.
  • a second aspect of the application also provides a battery module, including the secondary battery according to any embodiment of the first aspect of the application.
  • a third aspect of the present application also provides a battery pack, including the battery module according to the embodiment of the second aspect of the present application.
  • the fourth aspect of the present application also provides an electrical device, including a secondary battery as in any embodiment of the first aspect of the present application, a battery module as in the second embodiment of the present application, or a third embodiment of the present application. battery pack.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery shown in FIG. 1 .
  • FIG. 3 is a schematic plan view of an embodiment of the electrode assembly of the secondary battery of the present application.
  • Figure 4 is a schematic cross-sectional view of an embodiment of the electrode assembly of the secondary battery of the present application.
  • Figure 5 is a schematic cross-sectional view of another embodiment of the electrode assembly of the secondary battery of the present application.
  • Figure 6 is a schematic cross-sectional view of another embodiment of the electrode assembly of the secondary battery of the present application.
  • Figure 7 is a schematic cross-sectional view of yet another embodiment of the electrode assembly of the secondary battery of the present application.
  • Figure 8 is a schematic cross-sectional view of yet another embodiment of the electrode assembly of the secondary battery of the present application.
  • Figure 9 is a schematic cross-sectional view of yet another embodiment of the electrode assembly of the secondary battery of the present application.
  • FIG. 10 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 11 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 12 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 11 .
  • FIG. 13 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • X height direction
  • Y first direction
  • Z width direction
  • Secondary battery 51. Outer packaging; 52. Electrode assembly; 52a, pole lug part; 52b, main body part;
  • Positive electrode piece 5211. First positive electrode part; 5212. Second positive electrode part; 5213. Positive electrode connection part;
  • Negative electrode piece 5221. First negative electrode part; 5222. Second negative electrode part; 5223. Negative electrode connection part;
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: 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).
  • connection should be understood in a broad sense.
  • connection can be a fixed connection, a detachable connection, or an integral connection.
  • Connection can be a direct connection, or an indirect connection through an intermediary, or an internal connection between two components.
  • connection can be a direct connection, or an indirect connection through an intermediary, or an internal connection between two components.
  • the secondary battery includes an electrode assembly.
  • the electrode assembly includes a positive electrode piece and a negative electrode piece.
  • electrons on the positive electrode piece can migrate to the negative electrode piece through an external circuit, and metal ions such as lithium ions can move from the positive electrode piece to the negative electrode piece.
  • the sheet migrates to the electrolyte and through the electrolyte to the negative electrode sheet and combines with electrons to form a metal such as lithium. If lithium ions cannot migrate to the negative electrode sheet, lithium ions will precipitate on the surface of the negative electrode sheet, forming lithium dendrites that pierce the isolation film, causing an internal short circuit in the secondary battery and causing safety risks.
  • the size of the negative electrode piece is usually designed to be larger than the size of the positive electrode piece to ensure that lithium ions can basically migrate into the negative electrode active material of the negative electrode piece; although the above method can improve There is a problem of lithium precipitation, but the inventor found that the above design makes the space inside the secondary battery unable to be fully utilized, and the space utilization rate is poor.
  • the inventor has improved the secondary battery and improved the internal dimensions of the electrode assembly.
  • the size of the positive electrode piece is greater than or equal to The size of the negative electrode plate can effectively utilize the space of the secondary battery and improve the energy density of the secondary battery.
  • this application proposes a secondary battery.
  • the secondary battery 5 includes a housing assembly and an electrode assembly 52; the electrode assembly 52 is disposed in the housing assembly.
  • the housing assembly may also be used to contain an electrolyte, such as an electrolyte.
  • the housing assembly can be of various construction forms.
  • the shell assembly may include an outer package 51 and a cover plate 53.
  • the outer package 51 is a hollow structure with one side open.
  • the cover plate 53 covers the opening of the outer package 51 and forms a sealed connection to form a sealing connection.
  • a housing chamber housing the electrode assembly 52 and the electrolyte.
  • the outer package 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a containing cavity.
  • the outer package 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the outer packaging 51 can be in various shapes, such as cylinder, cuboid, etc.
  • the shape of the outer package 51 can be determined according to the specific shape of the electrode assembly 52 .
  • a cylindrical outer packaging may be used; if the electrode assembly 52 has a rectangular parallelepiped structure, a rectangular parallelepiped outer packaging may be used.
  • This application has no particular limitation on the shape of the secondary battery 5, which may be cylindrical, square or any other shape. As shown in FIG. 1 , a square-structured secondary battery 5 is shown as an example.
  • the cover plate 53 includes an end cap 531 , and the end cap 531 covers the opening of the outer package 51 .
  • the end cap 531 may have a variety of structures.
  • the end cap 531 may be a plate-shaped structure, a hollow structure with one end open, etc.
  • the outer package 51 has a rectangular parallelepiped structure
  • the end cover 531 has a plate-like structure
  • the end cover 531 covers the opening at the top of the outer package 51 .
  • the end cap 531 can be made of insulating material (such as plastic) or conductive material (such as metal).
  • the cover plate 53 may also include an insulating member located on the side of the end cap 531 facing the electrode assembly 52 to insulate the end cap 531 from the electrode assembly 52 .
  • the cover plate 53 may further include electrode terminals 532 mounted on the end cap 531 .
  • electrode terminals 532 There are two electrode terminals 532 , and the two electrode terminals 532 are respectively defined as a positive electrode terminal and a negative electrode terminal. Both the positive electrode terminal and the negative electrode terminal are used to electrically connect with the electrode assembly 52 to output the electric energy generated by the electrode assembly 52 .
  • the shell assembly can also be of other structures.
  • the shell assembly includes an outer package 51 and two cover plates 53 .
  • the outer package 51 is a hollow structure with openings on opposite sides, and one cover plate 53 corresponds to the cover plate 53 .
  • a sealed connection is formed at an opening of the outer package 51 to form a containing cavity for containing the electrode assembly 52 and the electrolyte.
  • one cover plate 53 may be provided with two electrode terminals 532 and the other cover plate 53 may not be provided with any electrode terminal 532 , or the two cover plates 53 may each be provided with one electrode terminal 532 .
  • the secondary battery 5 there may be one electrode assembly 52 housed in the case assembly, or there may be a plurality of electrode assemblies 52 .
  • the electrode assembly 52 includes a positive electrode piece 521, a negative electrode piece 522, and an isolation film 523; the isolation film 523 is disposed on the positive electrode piece 521 and the negative electrode piece between 522.
  • the electrode assembly 52 may be a wound electrode assembly, a laminated electrode assembly, or other forms of electrode assembly.
  • electrode assembly 52 is a rolled electrode assembly.
  • the positive electrode piece 521, the negative electrode piece 522 and the isolation film 523 are all in a strip structure.
  • the positive electrode piece 521 , the isolation film 523 and the negative electrode piece 522 can be sequentially stacked and wound more than two times to form the electrode assembly 52 .
  • the electrode assembly 52 is a stacked electrode assembly. Specifically, the electrode assembly 52 includes a plurality of positive electrode pieces 521 and a plurality of negative electrode pieces 522. The positive electrode pieces 521 and the negative electrode pieces 522 are alternately stacked, and the stacking direction is parallel to the thickness direction of the positive electrode pieces 521 and the negative electrode pieces 522. thickness direction.
  • the electrode assembly 52 includes a main body part 52b and a tab part 52a connected to the main body part 52b.
  • the pole portion 52a extends from an end of the main body portion 52b close to the cover plate.
  • pole tabs 52 a there are two pole tabs 52 a , and the two pole tabs 52 a are respectively defined as a positive pole tab and a negative pole tab.
  • the positive electrode tab part and the negative electrode tab part may extend from the same end of the main body part 52b, or may respectively extend from opposite ends of the main body part 52b.
  • the main body part 52b is the core part of the electrode assembly 52 to realize the charging and discharging function, and the tab part 52a is used to draw out the current generated by the main body part 52b.
  • the main body part 52 b includes a positive current collecting part of the positive current collector, a positive electrode film layer, a negative current collecting part of the negative current collector, a negative electrode film layer, and a separator 523 .
  • the positive electrode tab portion includes a plurality of positive electrode tabs
  • the negative electrode tab portion includes a plurality of negative electrode tabs.
  • the tab portion 52a is used to electrically connect to the electrode terminal 532.
  • the tab part 52a may be directly connected to the electrode terminal 532 by welding or other methods, or may be indirectly connected to the electrode terminal 532 through other members.
  • the electrode assembly 52 further includes a current collecting member for electrically connecting the electrode terminal 532 and the tab portion 52a.
  • the positive current collecting member is used to electrically connect the positive electrode terminal and the positive electrode lug, and the negative current collecting member is used for electrical connection. Negative electrode terminal and negative electrode lug.
  • the positive electrode current collecting members of the plurality of electrode assemblies 52 may be integrally provided, and the negative electrode current collecting members of the plurality of electrode assemblies 52 may be integrally provided.
  • the positive electrode sheet 521 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 current collector has two surfaces facing each other in its own 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.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can 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 base layer.
  • Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for the secondary battery 5 .
  • the cathode active material may include at least one of the following materials: layered structure cathode active material (such as ternary, lithium/sodium nickelate, lithium/sodium cobaltate, lithium/sodium manganate, rich lithium/sodium layer and rock salt phase layered materials), olivine-type phosphate active materials, spinel structure cathode active materials (such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel manganese Lithium oxide and lithium nickel manganate, etc.).
  • layered structure cathode active material such as ternary, lithium/sodium nickelate, lithium/sodium cobaltate, lithium/sodium manganate, rich lithium/sodium layer and rock salt phase layered materials
  • olivine-type phosphate active materials such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spine
  • the general formula of the layered structure cathode active material is: Li x A y Ni a Co b Mn c M (1-abc) Y z , where 0 ⁇ x ⁇ 2.1, 0 ⁇ y ⁇ 2.1, and 0.9 ⁇ x+y ⁇ 2.1; 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, and 0.1 ⁇ a+b+c ⁇ 1; 1.8 ⁇ z ⁇ 3.5;
  • A is selected from Na, K, Mg One or more of them;
  • M is selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd , one or more of Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce;
  • Y is selected from one or more of O and F.
  • the layered structure cathode active material may include lithium cobalt oxide LCO, lithium nickel oxide LNO, lithium manganate LMO, LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.8 Co 0.1 Mn 0.1 One or more of O 2 (NCM811) and LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523).
  • the general formula of the olivine-type phosphate active material is: Li x A y Me a M b P 1-c X c Y z , where 0 ⁇ x ⁇ 1.3, 0 ⁇ y ⁇ 1.3, and 0.9 ⁇ x+y ⁇ 1.3; 0.9 ⁇ a ⁇ 1.5, 0 ⁇ b ⁇ 0.5, and 0.9 ⁇ a+b ⁇ 1.5; 0 ⁇ c ⁇ 0.5; 3 ⁇ z ⁇ 5;
  • A is selected from one of Na, K and Mg One or more;
  • Me is selected from one or more of Mn, Fe, Co, and Ni;
  • M is selected from B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, One or more of Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce;
  • X is selected from S, Si, Cl, B, One or more of C and N;
  • Y is selected from one or more
  • the olivine-type phosphate active material includes one or more of LiFePO 4 , LiMnPO 4 , LiNiPO 4 , and LiCoPO 4 .
  • the general formula of the spinel structure cathode active material is: Li x A y Mn a M 2-a Y z , where 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, and 0.9 ⁇ x+y ⁇ 2; 0.5 ⁇ a ⁇ 2; 3 ⁇ z ⁇ 5; A is selected from one or more of Na, K, Mg; M is selected from Ni, Co, B, Mg, Al, Si, P, S, One of Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce or Several; Y is selected from one or more of O and F.
  • the spinel structure cathode active materials include LiMn 2 O 4 , LiNi 0.5 Mn 1.5 O 4 , LiCr 0.3 Mn 1.7 O 4 , Li 1.1 Al 0.1 Mn 1.9 O 4 , Li 2 Mn 2 O 4 and Li 1.5 Mn One or more of 2 O 4 .
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet 521 can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet 521, such as positive active materials, conductive agents, binders and any other components in a solvent (for example, N-methylpyrrolidone) is used to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece 521 can be obtained.
  • a solvent For example, N-methylpyrrolidone
  • the negative electrode sheet 522 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 including a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own 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.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • 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 base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • 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.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes 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.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet 522 may be prepared by dispersing the above-mentioned components used to prepare the negative electrode sheet 522 , such as negative active materials, conductive agents, binders, and any other components in a solvent (e.g., deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece 522 can be obtained.
  • a solvent e.g., deionized water
  • the secondary battery 5 further includes a separator 523.
  • This application has no particular limitation on the type of isolation membrane 523, and any well-known porous structure isolation membrane 523 with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane 523 can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film 523 may be a single-layer film or a multi-layer composite film, and is not particularly limited.
  • the materials of each layer may be the same or different, and are not particularly limited.
  • the projection of the negative pole piece 522 along the first direction Y is located within the projection of the positive pole piece 521 along the first direction Y, where the first direction Y is perpendicular to the height direction of the housing assembly.
  • the height direction X of the shell component may specifically be the height direction X of the outer package.
  • the first direction Y can be any direction perpendicular to the height direction X of the outer package, that is, the first direction Y can be perpendicular to the height direction X of the outer package.
  • the projection of the negative electrode piece 522 along the first direction Y is located within the projection of the positive electrode piece 521 along the first direction Y, which includes two forms.
  • the first form is that the projection of the negative electrode piece 522 completely overlaps the projection of the positive electrode piece 521.
  • the area of the negative electrode piece 522 and the area of the positive electrode piece 521 can be the same, that is, it can be considered that the positive electrode piece 521 can cover the negative electrode piece 522. .
  • the second form is that the projection of the negative electrode piece 522 is smaller and the projection of the positive electrode piece 521 is larger, that is, the area of the positive electrode piece 521 is relatively larger, and the positive electrode piece 521 can cover the negative electrode piece 522; in this case , it can be that the size of the positive electrode piece 521 in its own width direction is larger than the size of the negative electrode piece 522 in its own width direction; it can also be that the size of the positive electrode piece 521 in its own length direction is larger than the size of the positive electrode piece 521 in its own width direction. The size along its own length.
  • the space occupancy rate of the positive electrode piece 521 is higher, and the space on the positive electrode piece 521 can be fully improved.
  • the quality of the positive active material; and the energy density of the secondary battery 5 can also be improved.
  • the projection of the negative pole piece 522 along the first direction Y overlaps with the projection of the positive pole piece 521 along the first direction Y.
  • the area of the negative electrode piece 522 is relatively large and can cover each other with the positive electrode piece 521, which can further ensure that the metal ions released from the positive electrode piece 521 can be embedded in the negative active material of the negative electrode piece 522, reducing the precipitation of metal ions in the negative electrode. risk on the surface of the active material, thereby improving the safety performance of the secondary battery 5.
  • the size of the negative electrode piece 522 along its own width direction is less than or equal to the size of the positive electrode piece 521 along its own width direction.
  • FIG. 4 shows that the size of the negative electrode piece 522 along its own width direction is equal to the size of the positive electrode piece 521 along its own width direction.
  • FIG. 5 shows that the size of the negative electrode piece 522 along its own width direction is smaller than the size of the positive electrode piece 521 .
  • the width direction of the positive electrode piece 521 is parallel to the width direction of the negative electrode piece, and the Z direction in the figure represents the width direction.
  • the space occupancy rate of the positive electrode piece 521 is increased, thereby increasing the energy density of the secondary battery 5 .
  • the size of the negative electrode piece 522 along its own width direction is A1
  • the size of the positive electrode piece 521 along its own width direction is A2, -15mm ⁇ A1-A2 ⁇ -2mm; for example, A1-A2 can be It is -15mm, -10mm, -8mm, -7mm, -6mm, -5mm, -4mm, -3mm or -2mm; or a range consisting of any two of the above values.
  • the positive electrode piece 521 includes two first edges opposite to each other along its own width direction. From the first edge to the direction of the center line of the positive electrode piece 521, the gram capacity of the positive electrode piece 521 is gradually increased. increasing trend.
  • the gram capacity of the end of the positive electrode piece 521 in the width direction is relatively low, and the metal ions released from the end of the positive electrode piece 521 are relatively small, so that the ratio CB of the capacities of the positive and negative electrode pieces 521 is increased, thereby increasing
  • This allows the metal vacancies provided by the negative electrode piece 522 to accept more metal ions, thereby reducing the risk of metal ions precipitating to form metal dendrites at the ends of the negative electrode piece 522 and improving the safety performance of the secondary battery.
  • the centerline of the positive electrode piece 521 refers to the centerline perpendicular to the width direction, that is, the two first edges are symmetrical with respect to the centerline.
  • the positive electrode piece 521 includes a first positive electrode part 5211, a second positive electrode part 5212 and a positive electrode connection part 5213; the gram capacity of the first positive electrode part 5211 is C11; the second positive electrode part 5212 Opposite to the first positive electrode portion 5211 along the width direction of the positive electrode piece 521, the second positive electrode portion 5212 has a gram capacity of C12; and the positive electrode connection portion 5213 is disposed between the first positive electrode portion 5211 and the second positive electrode portion 5212, and The first positive electrode part 5211 and the second positive electrode part 5212 are connected.
  • the gram capacity of the positive electrode connecting part 5213 is C13.
  • the positive electrode piece 521 satisfies: 1mAh/g ⁇ C12-C11 ⁇ 500mAh/g; and/or 1mAh/g ⁇ C12- C13 ⁇ 500mAh/g.
  • the first positive electrode part 5211 and the second positive electrode part 5212 are located at the end of the positive electrode piece 521 along its own width direction Z.
  • the first positive electrode part 5211 can be disposed close to the positive electrode lug and is electrically connected to the positive electrode lug.
  • the positive electrode portion 5212 can be disposed far away from the positive electrode lug; of course, the second positive electrode portion 5212 can be disposed close to the cathode lug and electrically connected to the positive electrode lug, and the first positive electrode portion 5211 can be disposed far away from the cathode lug.
  • the positive electrode tab 521 may include a positive electrode tab, that is, the positive electrode tab may be integrally formed with the positive electrode current collector.
  • the positive electrode tab may also be independently arranged and connected to the positive electrode current collector.
  • the first positive electrode part 5211, the second positive electrode part 5212 and the positive electrode connecting part 5213 can be coated with positive electrode active materials respectively, and the materials of the positive electrode active materials can be all the same, or can be different from each other; optionally, the first positive electrode part 5211 and the third positive electrode part 5211 can be coated with positive electrode active materials.
  • the two positive electrode parts 5212 can be made of the same material.
  • the coating weights of the first positive electrode part 5211, the second positive electrode part 5212 and the positive electrode connecting part 5213 can all be the same, or of course they can be different; optionally, the first positive electrode part 5211 and the second positive electrode part 5212 can use the same coating weight. Coating weight.
  • first positive electrode part 5211, the second positive electrode part 5212 and the positive electrode connecting part 5213 use the same positive electrode active material, different coating weights can be applied to different areas so that the gram capacity of each area is different.
  • first positive electrode part 5211, the second positive electrode part 5212 and the positive electrode connecting part 5213 adopt the same coating weight, positive electrode active materials of different materials can be coated in different areas to make the gram capacity of each area different;
  • the thickness of the positive electrode film layer in different areas formed by this method is basically the same, which is more conducive to forming a stable positive electrode film layer.
  • the gram capacity of the positive electrode connecting part 5213 is greater than the gram capacity of the first positive electrode part 5211, and the gram capacity of the first positive electrode part 5211 is relatively low.
  • the A positive electrode part 5211 is located at the end of the positive electrode piece 521, so that the ratio CB of the capacity at the ends of the positive and negative electrode pieces 522 is increased, so that the metal vacancies provided by the negative electrode piece 522 can accept more metal ions, thereby This can reduce the risk of metal ions precipitating to form metal dendrites at the end of the negative electrode piece 522 and improve the safety performance of the secondary battery 5 .
  • C12-C11 can be 1mAh/g, 5mAh/g, 10mAh/g, 20mAh/g, 50mAh/g, 80mAh/g, 100mAh/g, 120mAh/g, 150mAh/g, 180mAh/g, 200mAh /g, 250mAh/g, 280mAh/g, 300mAh/g, 320mAh/g, 350mAh/g, 400mAh/g, 450mAh/g or 500mAh/g; or a range consisting of any two of the above values.
  • the gram capacity of the positive electrode connection part 5213 is greater than the gram capacity of the second positive electrode part 5212, and the gram capacity of the second positive electrode part 5212 is relatively low.
  • the two positive electrode parts 5212 are located at the ends of the positive electrode piece 521, so that the ratio CB of the capacities at the ends of the positive and negative electrode pieces 522 is increased, so that the metal vacancies provided by the negative electrode piece 522 can accept more metal ions, thereby This can reduce the risk of metal ions precipitating to form metal dendrites at the end of the negative electrode piece 522 and improve the safety performance of the secondary battery 5 .
  • C12-C13 can be 1mAh/g, 5mAh/g, 10mAh/g, 20mAh/g, 50mAh/g, 80mAh/g, 100mAh/g, 120mAh/g, 150mAh/g, 180mAh/g, 200mAh /g, 250mAh/g, 280mAh/g, 300mAh/g, 320mAh/g, 350mAh/g, 400mAh/g, 450mAh/g or 500mAh/g; or a range consisting of any two of the above values.
  • the first positive electrode portion 5211 and the second positive electrode portion 5212 have the same size in the width direction of the positive electrode piece 521 .
  • the first positive electrode part 5211 and the second positive electrode part 5212 are the two ends of the positive electrode plate 521. Their dynamic properties during the charging and discharging process of the secondary battery 5 are basically the same. Therefore, the first positive electrode part 5211 and the second positive electrode part 5211 are The size of the portion 5212 in the width direction is set to be substantially the same, which can further ensure the consistency of the overall dynamic performance of the positive electrode piece 521. Moreover, it is beneficial to the processing and forming of the positive electrode film layer.
  • the first positive electrode part 5211 and the second positive electrode part 5212 are made of the same material.
  • the reactions of the same material during the lithium deintercalation process are basically the same, which is helpful to further ensure the consistency of the overall dynamic performance of the positive electrode piece 521 .
  • the negative electrode piece 522 includes two second edges opposite to each other along its own width direction, with the second edges pointing in the direction of the center line of the negative electrode piece 522 , and the gram capacity of the negative electrode piece 522 is Gradually decreasing trend.
  • the gram capacity of the end of the negative electrode piece 522 in the width direction is relatively high, which can increase more metal vacancies and accept more metal ions, thereby reducing the precipitation of metal ions at the end of the negative electrode piece 522 to form metal branches. reduce the risk of crystals and improve the safety performance of secondary batteries.
  • the center line of the negative electrode piece 522 refers to the center line perpendicular to the width direction, that is, the two second edges are symmetrical with respect to the center line.
  • the negative electrode piece 522 includes a first negative electrode part 5221, a second negative electrode part 5222 and a negative electrode connecting part 5223; the gram capacity of the first negative electrode part 5221 is C21; the second negative electrode part 5222 The first negative electrode part 5221 is opposite to each other along the width direction of the negative electrode piece 522, the gram capacity of the second negative electrode part 5222 is C22; and the negative electrode connection part 5223 is disposed between the first negative electrode part 5221 and the second negative electrode part 5222, and The first negative electrode part 5221 and the second negative electrode part 5222 are connected.
  • the gram capacity of the negative electrode connecting part 5223 is C23.
  • the negative electrode piece 522 satisfies: 1mAh/g ⁇ C21-C22 ⁇ 500mAh/g; and/or 1mAh/g ⁇ C23- C22 ⁇ 500mAh/g.
  • the first negative electrode part 5221 and the second negative electrode part 5222 are located at the ends of the negative electrode piece 522 along its own width direction.
  • the first negative electrode part 5221 can be disposed close to the negative electrode lug and is electrically connected to the negative electrode lug.
  • the second negative electrode The second negative electrode portion 5222 can be disposed far away from the negative electrode lug; of course, the second negative electrode portion 5222 can be disposed close to the negative electrode lug and electrically connected to the negative electrode lug, and the first negative electrode portion 5221 can be disposed far away from the negative electrode lug.
  • the negative electrode tab 522 may include a negative electrode tab, that is, the negative electrode tab may be integrally formed with the negative electrode current collector.
  • the negative electrode tab may also be independently arranged and connected to the negative electrode current collector.
  • the first negative electrode part 5221, the second negative electrode part 5222 and the negative electrode connecting part 5223 can be coated with negative electrode active materials respectively, and the materials of the negative electrode active materials can all be the same, or they can be different; optionally, the first negative electrode part 5221 and the negative electrode connecting part 5223 can be coated with negative electrode active materials.
  • the two negative electrode parts 5222 can be made of the same material.
  • the coating weights of the first negative electrode part 5221, the second negative electrode part 5222 and the negative electrode connecting part 5223 can all be the same, or of course they can be different; optionally, the first negative electrode part 5221 and the second negative electrode part 5222 can use the same coating weight. Coating weight.
  • first negative electrode part 5221, the second negative electrode part 5222 and the negative electrode connecting part 5223 use the same negative electrode active material, different coating weights can be applied to different areas so that the gram capacity of each area is different.
  • first negative electrode part 5221, the second negative electrode part 5222 and the negative electrode connecting part 5223 adopt the same coating weight, negative electrode active materials of different materials can be coated in different areas to make the gram capacity of each area different;
  • the thickness of the negative electrode film layer in different areas formed by this method is basically the same, which is more conducive to forming a stable negative electrode film layer.
  • the gram capacity of the negative electrode connection part 5223 is smaller than the gram capacity of the first negative electrode part 5221, and the gram capacity of the first negative electrode part 5221 is relatively high.
  • the ratio CB of the capacity at the ends of the positive and negative electrode pieces 522 is increased, so that the metal vacancies provided by the negative electrode piece 522 can accept more metal ions, thereby This can reduce the risk of metal ions precipitating to form metal dendrites at the end of the negative electrode piece 522 and improve the safety performance of the secondary battery 5 .
  • C21-C22 can be 1mAh/g, 5mAh/g, 10mAh/g, 20mAh/g, 50mAh/g, 80mAh/g, 100mAh/g, 120mAh/g, 150mAh/g, 180mAh/g, 200mAh /g, 250mAh/g, 280mAh/g, 300mAh/g, 320mAh/g, 350mAh/g, 400mAh/g, 450mAh/g or 500mAh/g; or a range consisting of any two of the above values.
  • the gram capacity of the negative electrode connection part 5223 is smaller than the gram capacity of the second negative electrode part 5222, and the gram capacity of the second negative electrode part 5222 is relatively high.
  • the two negative electrode portions 5222 are located at the ends of the negative electrode piece 522, so that the ratio CB of the capacities at the ends of the positive and negative electrode pieces 522 is increased, so that the metal vacancies provided by the negative electrode piece 522 can accept more metal ions, thereby This can reduce the risk of metal ions precipitating to form metal dendrites at the end of the negative electrode piece 522 and improve the safety performance of the secondary battery 5 .
  • C23-C22 can be 1mAh/g, 5mAh/g, 10mAh/g, 20mAh/g, 50mAh/g, 80mAh/g, 100mAh/g, 120mAh/g, 150mAh/g, 180mAh/g, 200mAh /g, 250mAh/g, 280mAh/g, 300mAh/g, 320mAh/g, 350mAh/g, 400mAh/g, 450mAh/g or 500mAh/g; or a range consisting of any two of the above values.
  • the first negative electrode portion 5221 and the second negative electrode portion 5222 have the same size in the width direction of the negative electrode plate 522 .
  • the first negative electrode part 5221 and the second negative electrode part 5222 are the two ends of the negative electrode plate 522. Their dynamic properties during the charging and discharging process of the secondary battery 5 are basically the same. Therefore, the first negative electrode part 5221 and the second negative electrode part 5221 are The size of the portion 5222 in the width direction is set to be substantially the same, which can further ensure the consistency of the overall dynamic performance of the negative electrode piece 522 . Moreover, it is beneficial to the processing and forming of the negative electrode film layer.
  • the first negative electrode part 5221 and the second negative electrode part 5222 are made of the same material.
  • the reactions of the same material during the lithium deintercalation process are basically the same, which is helpful to further ensure the consistency of the overall dynamic performance of the negative electrode piece 522 .
  • the positive electrode piece 521 may include a first positive electrode part 5211 , a second positive electrode part 5212 and a positive electrode connection part 5213 .
  • the negative electrode piece 522 includes a first negative electrode part 5221 , a second negative electrode part 5222 and a negative electrode connecting part 5223 .
  • the projection of the positive electrode plate 521 along the first direction Y is located within the projection of the isolation film 523 along the first direction Y.
  • the isolation film 523 can cover the positive electrode piece 521 to insulate the positive electrode piece 521 and the negative electrode piece 522, and can ensure that the ends of the positive electrode piece 521 and the ends of the negative electrode piece 522 basically do not come into contact, causing short circuit, thereby improving the safety performance of the secondary battery 5.
  • the size of the positive electrode plate 521 along its own width direction is less than or equal to the size of the isolation film 523 along its own width direction.
  • FIG. 8 shows that the size of the isolation film 523 along its own width direction is larger than the size of the positive electrode piece 521 along its own width direction.
  • FIG. 9 shows that the size of the isolation film 523 along its own width direction is equal to the size of the positive electrode piece 521 Dimensions along its own width.
  • the width direction of the positive electrode plate 521 is parallel to the width direction of the isolation film 523, and the Z direction in the figure represents the width direction.
  • the isolation film 523 can effectively insulate the positive electrode piece 521 and the negative electrode piece 522 in the width direction, especially when the width of the positive electrode piece 521 is larger than the width of the negative electrode piece 522, the isolation film 523 It can effectively isolate the positive electrode piece 521 and the negative electrode piece 522, reduce the risk of their ends contacting and causing a short circuit, and further improve the safety performance of the secondary battery 5.
  • the size of the positive electrode piece 521 along its own width direction is A2
  • the size of the isolation film 523 along its own width direction is A3, 0mm ⁇ A3-A2 ⁇ 6mm; optionally, 0 ⁇ A3-A2 ⁇ 6mm .
  • A3-A2 can be 0, 1mm, 2mm, 3mm, 4mm, 5mm or 6mm; or it can be a range consisting of any two of the above values.
  • the secondary battery 5 further includes an electrolyte.
  • the electrolyte plays a role in conducting metal ions between the positive electrode plate 521 and the negative electrode plate 522.
  • the electrolyte solution in this application can be an electrolyte solution known in the art and used for the secondary battery 5.
  • the electrolyte includes lithium salt and organic solvent.
  • the lithium salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the organic solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dimethyl carbonate, Propyl ester (DPC), methylpropyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), Propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4 - One or a combination of butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).
  • EC
  • the electrolyte solution of the present application can be prepared according to conventional methods in this field.
  • additives, solvents, electrolyte salts, etc. can be mixed uniformly to obtain an electrolyte solution.
  • the order of adding each material is not particularly limited.
  • additives, electrolyte salts, etc. can be added to the non-aqueous solvent and mixed evenly to obtain a non-aqueous electrolyte.
  • each component and its content in the electrolyte can be determined according to methods known in the art. For example, it can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), or the like.
  • GC-MS gas chromatography-mass spectrometry
  • IC ion chromatography
  • LC liquid chromatography
  • NMR nuclear magnetic resonance spectroscopy
  • An exemplary method of obtaining electrolyte from the secondary battery 5 includes the following steps: discharging the secondary battery 5 to the discharge cutoff voltage (for safety reasons, the battery is generally in a fully discharged state), then centrifuging, and then centrifuging an appropriate amount.
  • the liquid obtained by the treatment is the non-aqueous electrolyte.
  • the non-aqueous electrolyte can also be obtained directly from the liquid filling port of the secondary battery 5 .
  • the positive electrode piece 521 , the isolation film 523 , the negative electrode piece 522 and the electrolyte can be assembled to form the secondary battery 5 .
  • the positive electrode piece 521, the isolation film 523, and the negative electrode piece 522 can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is placed in an outer package, dried, and then injected with electrolyte and vacuumed.
  • the secondary battery 5 is obtained through processes such as packaging, standing, formation, and shaping.
  • the secondary batteries 5 according to the present application can be assembled into a battery module.
  • the number of secondary batteries 5 contained in the battery module can be multiple. The specific number can be adjusted according to the application and capacity of the battery module. .
  • FIG. 10 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application provides an electrical device.
  • the electrical device includes at least one of a secondary battery, a battery module and a battery pack of the present application.
  • Secondary batteries, battery modules and battery packs can be used as power sources for power-consuming devices, and can also be used as energy storage units for power-consuming devices.
  • Electric devices can be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf balls). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electrical device can select secondary batteries, battery modules or battery packs according to its usage requirements.
  • FIG. 1 is a schematic diagram of an electrical device as an example.
  • the electric device 6 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack 1 or a battery module can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • An aluminum foil with a thickness of 12 ⁇ m was used as the positive electrode current collector.
  • a copper foil with a thickness of 8 ⁇ m was used as the negative electrode current collector.
  • a porous polyethylene (PE) film is used as the isolation membrane.
  • the non-aqueous organic solvents ethylene carbonate EC and diethyl carbonate DMC are mixed at a volume ratio of 1:1 to obtain an electrolyte solvent, and then the lithium salt and the mixed solvent are mixed to form The electrolyte with a lithium salt concentration of 1mol/L.
  • the above-mentioned positive electrode piece, isolation film and negative electrode piece in order so that the isolation film is between the positive electrode piece and the negative electrode piece to play an isolation role, and then wind it to obtain the electrode assembly; place the electrode assembly in the outer packaging shell After drying, the electrolyte is injected, and through processes such as vacuum packaging, standing, formation, and shaping, a lithium-ion battery is obtained.
  • Examples 2-1 to 2-4 were prepared in a similar manner to Example 1. The difference from Example 1 is that the width dimension A2 of the positive electrode piece was adjusted in Examples 2-1 to 2-4.
  • Examples 3-1 to 3-3 were prepared in a similar manner to Example 1. The difference from Example 1 is that the width dimension A3 of the isolation film was adjusted in Examples 3-1 to 2-3.
  • Examples 4-1 to 4-5 were prepared in a similar manner to Example 1. The difference from Example 1 is that Examples 4-1 to 4-5 adjusted the gram capacity C12 of the positive electrode connection part.
  • Examples 5-1 to 5-5 were prepared in a similar manner to Example 1. The difference from Example 1 is that the gram capacity C22 of the negative electrode connection part was adjusted in Examples 5-1 to 5-5.
  • the comparative example was prepared in a similar manner to Example 1. The difference from Example 1 is that the width dimension A1 of the negative electrode piece was adjusted in the comparative example.
  • the testing methods of the first positive electrode part, the second positive electrode part and the positive electrode connection part are similar. Taking the first positive electrode part as an example Explain the testing process:
  • the materials of the first positive electrode part, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of solvent NMP in a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry;
  • the slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained; then, a metal lithium sheet is used as the counter electrode, and a polyethylene (PE) film is used as the isolation film, and a few drops are added.
  • PE polyethylene
  • the obtained button cell was left to stand for 12 hours, it was discharged at 25°C to a constant current of 0.05C to 0.005V, left to stand for 10 minutes, and then discharged to a constant current of 50 ⁇ A to 0.005V, left to stand for 10min, and then again to a constant current of 10 ⁇ A. Discharge to 0.005V; then charge to 2V with a constant current of 0.1C, and record the charging capacity.
  • the ratio of the charging capacity to the mass of the first positive electrode part is the initial gram capacity of the first negative electrode part.
  • the testing methods for the first negative electrode part, the second negative electrode part, and the negative electrode connecting part are similar. Taking the first negative electrode part as an example, Explain the testing process:
  • the obtained button cell was left to stand for 12 hours, it was discharged at 25°C with a constant current of 0.05C to 0.005V, left to stand for 10 minutes, and then discharged to a constant current of 0.005V with a current of 50 ⁇ A, left to stand for 10min, and then discharged to a constant current of 10 ⁇ A. Discharge to 0.005V; then charge to 2V with a constant current of 0.1C, and record the charging capacity.
  • the ratio of the charging capacity to the mass of the first negative electrode part is the initial gram capacity of the first negative electrode part.
  • the lithium-ion batteries prepared in the Examples and Comparative Examples were fully charged at a rate of 1C and fully discharged at a rate of 1C, and the actual discharge energy at this time was recorded; at 25°C, an electronic balance was used to measure the lithium-ion batteries. Weigh; the ratio of the actual discharge energy of the lithium-ion battery 1C to the weight of the lithium-ion battery is the actual energy density of the lithium-ion battery.
  • the actual energy density of the battery when the actual energy density is less than 80% of the expected energy density, the actual energy density of the battery is considered to be very low; when the actual energy density is greater than or equal to 80% of the expected energy density and less than 95% of the expected energy density, the actual energy density of the battery is considered to be low. ; When the actual energy density is greater than or equal to 95% of the expected energy density and less than 105% of the expected energy density, the actual energy density of the battery is considered moderate; when the actual energy density is greater than or equal to 105% of the expected energy density and less than 120% of the expected energy density, the battery is considered to be moderate. The actual energy density of the battery is considered to be high; when the actual energy density is more than 120% of the expected energy density, the actual energy density of the battery is considered to be very high.
  • Example 1 175.0
  • Example 2-1 173.5 Example 2-2 177.5
  • Example 2-3 180.0
  • Example 2-4 172.5
  • Example 3-1 175.25 Example 3-2 174.50
  • Example 3-3 173.75
  • Example 4-1 174.0 Example 4-2 185.0
  • Example 4-3 205.0
  • Example 5-1 176.0 Example 5-2 166.0
  • the size of the positive electrode piece in the comparative example is smaller than the size of the negative electrode piece, and the space utilization rate of the positive electrode piece is low.
  • the positive electrode is Setting the size of the piece to be larger than or equal to the size of the negative electrode piece can significantly improve the space utilization of the positive electrode piece.
  • Embodiment 3-1 to Embodiment 3-3 adjust the size of the separator, which can significantly improve the isolation effect of the separator between the positive electrode piece and the negative electrode piece, and can ensure the energy density of the secondary battery.
  • Examples 4-1 to 4-5 adjust the gram capacity of the positive electrode piece. As the gram capacity of the positive electrode piece increases, the energy density of the secondary battery is improved. However, when the gram capacity distribution on the overall structure of the positive electrode plate approaches uniformity, the overall performance of the positive electrode plate will be more uniform and stable.
  • Embodiment 5-1 to Embodiment 5-5 adjust the gram capacity of the negative electrode piece, which can correspondingly improve the gram capacity of the positive electrode piece, thereby adjusting the energy density of the secondary battery.

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Abstract

提供了一种二次电池（5）、电池模块（4）、电池包（1）和用电装置（6）。二次电池（5）包括外壳组件和电极组件（52）；电极组件（52）设置于外壳组件内，电极组件（52）包括正极极片（521）、负极极片（522）和设置于正极极片（521）和负极极片（522）之间的隔离膜（523），负极极片（522）沿第一方向的投影位于正极极片（521）沿第一方向的投影内，其中，第一方向垂直于外壳组件的高度方向。正极极片（521）的空间占用率较高，能够充分提高正极极片（521）上的正极活性材料的质量，从而提高二次电池（5）的能量密度。

Description

二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池领域，具体涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
二次电池具有容量高、寿命长等特性，因此广泛应用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。
在电池技术的发展中，二次电池中正极极片的空间占用率是决定二次电池性能的重要指标，因此，如何提高正极极片的空间占用率，是电池技术中一个亟待解决的技术问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供了一种二次电池，所述二次电池包括外壳组件和电极组件；电极组件设置于外壳组件内，电极组件包括正极极片、负极极片和设置于正极极片和负极极片之间的隔离膜，负极极片沿第一方向的投影位于正极极片沿第一方向的投影内，其中，第一方向垂直于外壳组件的高度方向。
由此，本申请通过将负极极片沿第一方向的投影设置于正极极片沿第一方向的投影内，正极极片的空间占用率较高，能够充分提高正极极片上的正极活性材料的质量；并且还能够提高二次电池的能量密度。
在任意实施方式中，负极极片沿第一方向的投影与正极极片沿第一方向的投影重叠。
由此，本申请的负极极片的面积相对较大，能够和正极极片相互覆盖，能够进一步保证由正极极片脱出的金属离子能够嵌入至负极极片的负极活性材料中，降低金属离子析出在负极活性材料表面的风险，从而提高二次电池的安全性能。
在任意实施方式中，负极极片沿其自身宽度方向的尺寸小于或等于正极极片沿其自身宽度方向的尺寸；可选地，负极极片沿其自身宽度方向的尺寸为A1，正极极片沿其自身宽度方向的尺寸为A2，-15mm≤A1-A2≤-2mm。
由此，本申请通过对负极极片和正极极片的尺寸的调控，提高正极极片的空间 占用率，从而提高二次电池的能量密度。
在任意实施方式中，正极极片包括沿其自身宽度方向彼此相对的两个第一边缘，由第一边缘指向正极极片的中心线的方向上，正极极片的克容量呈逐渐增加趋势。正极极片宽度方向上的端部的克容量相对较低，使得正负极极片端部的容量的比值CB值得以提升，从而使得负极极片提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。
在任意实施方式中，正极极片包括第一正极部、第二正极部和正极连接部；第一正极部的克容量为C11；第二正极部与第一正极部沿正极极片的宽度方向彼此相对，第二正极部的克容量为C12；以及正极连接部，设置于第一正极部和第二正极部之间，且连接第一正极部和第二正极部，正极连接部的克容量为C13，正极极片满足：1mAh/g≤C12-C11≤500mAh/g；和/或1mAh/g≤C12-C13≤500mAh/g。
由此，本申请的正极极片满足上述公式时，正极连接部的克容量大于第一正极部的克容量，第一正极部的克容量相对较低，鉴于第一正极部位于正极极片的端部，使得正负极极片端部的容量的比值CB值得以提升，从而使得负极极片提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。相应的，正极连接部的克容量大于第二正极部的克容量，能够降低金属离子在负极极片的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。
在任意实施方式中，第一正极部和第二正极部在正极极片宽度方向的尺寸相同。第一正极部和第二正极部为正极极片的两个端部，其在二次电池充放电过程中的动力学性能基本相同，故将第一正极部和第二正极部的宽度方向的尺寸设置为基本相同，可以进一步保证正极极片整体动力学性能的一致性。并且，有利于正极膜层的加工成型。
在任意实施方式中，第一正极部和第二正极部采用相同的材质。相同材质的脱嵌锂过程发生的反应基本相同，有利于进一步保证正极极片整体动力学性能的一致性。并且，有利于正极膜层的加工成型。
在任意实施方式中，负极极片包括沿其自身宽度方向彼此相对的两个第二边缘，由第二边缘指向与负极极片的中心线的方向上，负极极片的克容量呈逐渐减少趋势。负极极片宽度方向上的端部的克容量相对较高，能够提高更多的金属空位，接受更多的金属离子，从而能够降低金属离子在负极极片的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。
在任意实施方式中，负极极片包括第一负极部、第二负极部和负极连接部；第一负极部的克容量为C21；第二负极部与第一负极部沿负极极片的宽度方向彼此相对，第二负极部的克容量为C22；以及负极连接部设置于第一负极部和第二负极部之间，且连接第一负极部和第二负极部，负极连接部的克容量为C23，负极极片满足：1mAh/g≤C21-C22≤500mAh/g；和/或1mAh/g≤C23-C22≤500mAh/g。
由此，本申请的负极极片满足上述公式时，负极连接部的克容量小于第一负极部的克容量，第一负极部的克容量相对较高，鉴于第一负极部位于负极极片的端部，使得正负极极片端部的容量的比值CB值得以提升，从而使得负极极片提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。相应的，负极连接部的克容量小于第二负极部的克容量，能够降低金属离子在负极极片的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。
在任意实施方式中，第一负极部和第二负极部在负极极片宽度方向的尺寸相同。第一负极部和第二负极部为负极极片的两个端部，其在二次电池充放电过程中的动力学性能基本相同，故将第一负极部和第二负极部的宽度方向的尺寸设置为基本相同，可以进一步保证负极极片整体动力学性能的一致性。并且，有利于负极膜层的加工成型。
在任意实施方式中，第一负极部和第二负极部采用相同的材质。相同材质的脱嵌锂过程发生的反应基本相同，有利于进一步保证负极极片整体动力学性能的一致性。并且，有利于负极膜层的加工成型。
在任意实施方式中，正极极片沿第一方向的投影位于隔离膜沿第一方向的投影内。隔离膜能够覆盖正极极片，起到对正极极片和负极极片的隔绝作用，能够保证正极极片的端部和负极极片的端部基本不会接触而导致发生短路等情况，由此提高二次电池的安全性能。
在任意实施方式中，正极极片沿其自身宽度方向的尺寸小于或等于隔离膜沿其自身宽度方向的尺寸；可选地，正极极片沿其自身宽度方向的尺寸为A2，隔离膜沿其自身宽度方向的尺寸为A3，0mm≤A3-A2≤6mm。
由此，本申请的隔离膜能够在宽度方向上对正极极片和负极极片起到良好的隔绝作用，隔离膜能够有效隔绝正极极片和负极极片，降低二者的端部接触并导致短路的风险，进一步提高二次电池的安全性能。
本申请的第二方面还提供了一种电池模块，包括如本申请第一方面任一实施方式的二次电池。
本申请的第三方面还提供了一种电池包，包括如本申请第二方面实施方式的电池模块。
本申请第四方面还提供了一种用电装置，包括如本申请第一方面任一实施方式的二次电池、如本申请第二方面实施方式的电池模块或如本申请第三方面实施方式的电池包。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图 获得其他的附图。
图1是本申请的二次电池的一实施方式的示意图。
图2是图1所示的二次电池的实施方式的分解示意图。
图3是本申请的二次电池的电极组件的一实施方式的俯视示意图。
图4是本申请的二次电池的电极组件的一实施方式的剖面示意图；
图5是本申请的二次电池的电极组件的另一实施方式的剖面示意图；
图6是本申请的二次电池的电极组件的又一实施方式的剖面示意图；
图7是本申请的二次电池的电极组件的再一实施方式的剖面示意图；
图8是本申请的二次电池的电极组件的再一实施方式的剖面示意图；
图9是本申请的二次电池的电极组件的再一实施方式的剖面示意图；
图10是本申请的电池模块的一实施方式的示意图。
图11是本申请的电池包的一实施方式的示意图。
图12是图11所示的电池包的实施方式的分解示意图。
图13是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
附图未必按照实际的比例绘制。
附图标记说明如下：
X、高度方向；Y、第一方向；Z、宽度方向；
1、电池包；2、上箱体；3、下箱体；4、电池模块；
5、二次电池；51、外包装；52、电极组件；52a、极耳部；52b、主体部；
521、正极极片；5211、第一正极部；5212、第二正极部；5213、正极连接部；
522、负极极片；5221、第一负极部；5222、第二负极部；5223、负极连接部；
523、隔离膜；
53、盖板；531、端盖；532、电极端子；
6、用电装置。
具体实施方式
以下，详细说明具体公开了本申请的二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、 1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。本申请的说明书和权利要求书或上述附图中的术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序或主次关系。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
如果没有特别的说明，在本申请中，术语“安装”、“相连”、“连接”、“附接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
二次电池包括电极组件，电极组件包括正极极片和负极极片，在二次电池充电过程中，正极极片上的电子可以通过外部电路迁移至负极极片，金属离子例如锂离子能够从正极极片迁移至电解液，并通过电解液迁移至负极极片并与电子结合形成金属例如锂。如果锂离子不能迁移至负极极片上，将会导致锂离子在负极极片表面析出，从而形成锂枝晶刺穿隔离膜，造成二次电池内部短路，引发安全风险等。
为了降低锂离子在负极极片表面析出的风险，通常设计负极极片的尺寸大于正极极片的尺寸，以保证锂离子基本都能够迁移至负极极片的负极活性材料中；虽然上述方法能够改善析锂的问题，但是发明人发现上述设计使得二次电池内部的空间无法得到充足的利用，空间利用率较差。
鉴于此，发明人对二次电池进行了改进，对电极组件的内部尺寸进行改进，在 确保正极极片脱出的锂离子基本嵌入至负极极片的基础上，使得正极极片的尺寸大于或等于负极极片的尺寸，从而有效地利用二次电池的空间，提高二次电池的能量密度。接下来对本申请的二次电池进行详细说明。
二次电池
第一方面，本申请提出了一种二次电池。
如图1和图2所示，所述二次电池5包括外壳组件和电极组件52；电极组件52设置于外壳组件内。
在一些实施例中，外壳组件还可用于容纳电解质，例如电解液。外壳组件可以是多种结构形式。
在一些实施例中，外壳组件可以包括外包装51和盖板53，外包装51为一侧开口的空心结构，盖板53盖合于外包装51的开口处并形成密封连接，以形成用于容纳电极组件52和电解质的容纳腔。其中，外包装51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。外包装51具有与容纳腔连通的开口，盖板53用于盖设开口，以封闭容纳腔。
外包装51可以是多种形状，比如，圆柱体、长方体等。外包装51的形状可根据电极组件52的具体形状来确定。比如，若电极组件52为圆柱体结构，则可选用为圆柱体外包装；若电极组件52为长方体结构，则可选用长方体外包装。本申请对二次电池5的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，盖板53包括端盖531，端盖531盖合于外包装51的开口处。端盖531可以是多种结构，比如，端盖531为板状结构、一端开口的空心结构等。示例性的，在图4中，外包装51为长方体结构，端盖531为板状结构，端盖531盖合于外包装51顶部的开口处。
端盖531可以由绝缘材料(例如塑胶)制成，也可以由导电材料(例如金属)制成。当端盖531由金属材料制成时，盖板53还可包括绝缘件，绝缘件位于端盖531面向电极组件52的一侧，以将端盖531和电极组件52绝缘隔开。
在一些实施例中，盖板53还可以包括电极端子532，电极端子532安装于端盖531上。电极端子532为两个，两个电极端子532分别定义为正极电极端子和负极电极端子，正极电极端子和负极电极端子均用于与电极组件52电连接，以输出电极组件52所产生的电能。
在另一些实施例中，外壳组件也可以是其他结构，比如，外壳组件包括外包装51和两个盖板53，外包装51为相对的两侧开口的空心结构，一个盖板53对应盖合于外包装51的一个开口处并形成密封连接，以形成用于容纳电极组件52和电解质的容纳腔。在这种结构中，可以一个盖板53上设有两个电极端子532，而另一个盖板53上未设置电极端子532，也可以两个盖板53各设置一个电极端子532。
在二次电池5中，容纳于外壳组件内的电极组件52可以是一个，也可以是多个。
如图2和图3所示，在一些实施方式中，电极组件52包括正极极片521、负极极片522和隔离膜523；隔离膜523设置于所述正极极片521和所述负极极片522之间。电极组件52可以是卷绕式电极组件、叠片式电极组件或其它形式的电极组件。
在一些实施例中，电极组件52为卷绕式电极组件。正极极片521、负极极片522和隔离膜523均为带状结构。本申请实施例可以将正极极片521、隔离膜523以及负极极片522依次层叠并卷绕两圈以上形成电极组件52。
在另一些实施例中，电极组件52为叠片式电极组件。具体地，电极组件52包括多个正极极片521和多个负极极片522，正极极片521和负极极片522交替层叠，层叠的方向平行于正极极片521的厚度方向和负极极片522的厚度方向。
从电极组件52的外形来看，电极组件52包括主体部52b和连接于主体部52b的极耳部52a。示例性地，极耳部52a从主体部52b的靠近盖板的一端延伸出。
在一些实施例中，极耳部52a为两个，两个极耳部52a分别定义为正极极耳部和负极极耳部。正极极耳部和负极极耳部可以从主体部52b的同一端延伸出，也可以分别从主体部52b的相反的两端延伸出。
主体部52b为电极组件52实现充放电功能的核心部分，极耳部52a用于将主体部52b产生的电流引出。主体部52b包括正极集流体的正极集流部、正极膜层、负极集流体的负极集流部、负极膜层以及隔离膜523。正极极耳部包括多个正极极耳，负极极耳部包括多个负极极耳。
极耳部52a用于电连接于电极端子532。极耳部52a可以通过焊接等方式直接连接于电极端子532，也可以通过其它构件间接地连接于电极端子532。例如，电极组件52还包括集流构件，集流构件用于电连接电极端子532和极耳部52a。集流构件为两个，两个集流构件分别定义为正极集流构件和负极集流构件，正极集流构件用于电连接正极电极端子和正极极耳部，负极集流构件用于电连接负极电极端子和负极极耳部。当电池单体设有多个电极组件52时，多个电极组件52的正极集流构件可以一体设置，多个电极组件52的负极集流构件可以一体设置。
[正极极片]
正极极片521包括正极集流体和设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于二次电池5的正极 活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：层状结构正极活性材料(例如三元、镍酸锂/钠、钴酸锂/钠、锰酸锂/钠、富锂/钠层状和岩盐相层状等材料)、橄榄石型磷酸盐活性材料、尖晶石结构的正极活性材料(例如尖晶石锰酸锂、尖晶石镍锰酸锂、富锂的尖晶石锰酸锂和镍锰酸锂等)。示例性地，层状结构正极活性材料的通式为：Li xA yNi aCo bMn cM (1-a-b-c)Y z，其中，0≤x≤2.1，0≤y≤2.1，且0.9≤x+y≤2.1；0≤a≤1，0≤b≤1，0≤c≤1，且0.1≤a+b+c≤1；1.8≤z≤3.5；A选自Na、K、Mg中的一种或几种；M选自B、Mg、Al、Si、P、S、Ca、Sc、Ti、V、Cr、Fe、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ce中的一种或几种；Y选自O、F中的一种或几种。具体地，层状结构正极活性材料可以包括钴酸锂LCO、镍酸锂LNO、锰酸锂LMO、LiNi 1/3Co 1/3Mn 1/3O 2(NCM333)、LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)和LiNi 0.5Co 0.2Mn 0.3O 2(NCM523)中的一种或多种。示例性地，橄榄石型磷酸盐活性材料的通式为：Li xA yMe aM bP 1-cX cY z，其中，0≤x≤1.3，0≤y≤1.3，且0.9≤x+y≤1.3；0.9≤a≤1.5，0≤b≤0.5，且0.9≤a+b≤1.5；0≤c≤0.5；3≤z≤5；A选自Na、K、Mg中的一种或几种；Me选自Mn、Fe、Co、Ni中的一种或几种；M选自B、Mg、Al、Si、P、S、Ca、Sc、Ti、V、Cr、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ce中的一种或几种；X选自S、Si、Cl、B、C、N中的一种或几种；Y选自O、F中的一种或几种。具体地，橄榄石型磷酸盐活性材料包括LiFePO 4、LiMnPO 4、LiNiPO 4、和LiCoPO 4中的一种或多种。示例性地，尖晶石结构的正极活性材料的通式为：Li xA yMn aM 2-aY z，其中，0≤x≤2，0≤y≤1，且0.9≤x+y≤2；0.5≤a≤2；3≤z≤5；A选自Na、K、Mg中的一种或几种；M选自Ni、Co、B、Mg、Al、Si、P、S、Ca、Sc、Ti、V、Cr、Fe、Cu、Zn、Sr、Y、Zr、Nb、Mo、Cd、Sn、Sb、Te、Ba、Ta、W、Yb、La、Ce中的一种或几种；Y选自O、F中的一种或几种。具体地，尖晶石结构的正极活性材料包括LiMn 2O 4、LiNi 0.5Mn 1.5O 4、LiCr 0.3Mn 1.7O 4、Li 1.1Al 0.1Mn 1.9O 4、Li 2Mn 2O 4和Li 1.5Mn 2O 4中的一种或多种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片521：将上述用于制备正极极片521的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片521。
[负极极片]
负极极片522包括负极集流体以及设置在负极集流体至少一个表面上的负极膜 层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片522：将上述用于制备负极极片522的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片522。
[隔离膜]
在一些实施方式中，二次电池5中还包括隔离膜523。本申请对隔离膜523的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜523。
在一些实施方式中，隔离膜523的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜523可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜523为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
如图4所示，在一些实施方式中，负极极片522沿第一方向Y的投影位于正极 极片521沿第一方向Y的投影内，其中，第一方向Y垂直于外壳组件的高度方向X。
在本文中，外壳组件的高度方向X具体可以为外包装的高度方向X。第一方向Y可以为垂直于外包装的高度方向X的任一方向，即第一方向Y能够垂直于外包装的高度方向X即可。
负极极片522沿第一方向Y的投影位于正极极片521沿第一方向Y的投影内，其包括两种形式。第一种形式为负极极片522的投影和正极极片521的投影完全重叠，负极极片522的面积和正极极片521的面积可以相同，即可以认为正极极片521能够覆盖负极极片522。第二种形式为负极极片522的投影较小，正极极片521的投影较大，即正极极片521的面积相对较大，正极极片521能够覆盖负极极片522；在这种情况下，可以是正极极片521在其自身宽度方向上的尺寸大于负极极片522在其自身宽度方向上的尺寸；也可以是正极极片521在其自身长度方向上的尺寸大于正极极片521在其自身长度方向上的尺寸。
本申请通过将负极极片522沿第一方向Y的投影设置于正极极片521沿第一方向Y的投影内，正极极片521的空间占用率较高，能够充分提高正极极片521上的正极活性材料的质量；并且还能够提高二次电池5的能量密度。
在一些实施方式中，负极极片522沿第一方向Y的投影与正极极片521沿第一方向Y的投影重叠。负极极片522的面积相对较大，能够和正极极片521相互覆盖，能够进一步保证由正极极片521脱出的金属离子能够嵌入至负极极片522的负极活性材料中，降低金属离子析出在负极活性材料表面的风险，从而提高二次电池5的安全性能。
如图4和图5所示，在一些实施方式中，负极极片522沿其自身宽度方向的尺寸小于或等于正极极片521沿其自身宽度方向的尺寸。图4示出了负极极片522沿其自身宽度方向的尺寸等于正极极片521沿其自身宽度方向的尺寸的情况，图5示出了负极极片522沿其自身宽度方向的尺寸小于正极极片521沿其自身宽度方向的尺寸的情况。在本申请中，正极极片521的宽度方向和负极极片的宽度方向平行，图中的Z方向表示宽度方向。
通过对负极极片522和正极极片521的尺寸的调控，提高正极极片521的空间占用率，从而提高二次电池5的能量密度。可选地，负极极片522沿其自身宽度方向的尺寸为A1，正极极片521沿其自身宽度方向的尺寸为A2，-15mm≤A1-A2≤-2mm；示例性地，A1-A2可以为-15mm、-10mm、-8mm、-7mm、-6mm、-5mm、-4mm、-3mm或-2mm；或者是上述任意两个数值组成的范围。
在一些实施方式中，正极极片521包括沿其自身宽度方向彼此相对的两个第一边缘，由第一边缘指向正极极片521的中心线的方向上，正极极片521的克容量呈逐渐增加趋势。正极极片521宽度方向上的端部的克容量相对较低，从正极极片521的端部脱出的金属离子相对较少，使得正负极极片端部的容量的比值CB值得以提升，从而使得负极极片522提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片522的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。在本申请 中，正极极片521的中心线是指垂直于宽度方向的中心线，即两个第一边缘相对于该中心线对称。
如图6所示，在一些实施方式中，正极极片521包括第一正极部5211、第二正极部5212和正极连接部5213；第一正极部5211的克容量为C11；第二正极部5212与第一正极部5211沿正极极片521的宽度方向彼此相对，第二正极部5212的克容量为C12；以及正极连接部5213设置于第一正极部5211和第二正极部5212之间，且连接第一正极部5211和第二正极部5212，正极连接部5213的克容量为C13，正极极片521满足：1mAh/g≤C12-C11≤500mAh/g；和/或1mAh/g≤C12-C13≤500mAh/g。
第一正极部5211和第二正极部5212位于正极极片521沿其自身宽度方向Z的端部，例如第一正极部5211可以靠近正极极耳部设置并与正极极耳部电连接，第二正极部5212可以远离正极极耳部设置；当然，第二正极部5212可以靠近正极极耳部设置并与正极极耳部电连接，第一正极部5211可以远离正极极耳部设置。在本申请中正极极片521可以包括正极极耳部，即正极极耳部可以与正极集流体一体成型，当然，正极极耳部也可以与正极集流体独立设置后连接为一体。
第一正极部5211、第二正极部5212和正极连接部5213可以分别涂覆正极活性材料，正极活性材料的材质可以全部相同，也可以两两不同；可选地，第一正极部5211和第二正极部5212可以采用相同的材质。第一正极部5211、第二正极部5212和正极连接部5213的涂布重量可以全部相同，当然也可以两两不同；可选地，第一正极部5211和第二正极部5212可以采用相同的涂布重量。在第一正极部5211、第二正极部5212和正极连接部5213采用相同的正极活性材料时，可以在不同的区域涂覆不同的涂布重量，以使各区域的克容量不同。在第一正极部5211、第二正极部5212和正极连接部5213采用相同的涂布重量时，可以在不同的区域涂覆不同材质的正极活性材料，以使各区域的克容量不同；此种方式所形成的不同区域的正极膜层的厚度基本相同，更有利于形成稳定的正极膜层。
正极极片521满足公式1mAh/g≤C12-C11≤500mAh/g时，正极连接部5213的克容量大于第一正极部5211的克容量，第一正极部5211的克容量相对较低，鉴于第一正极部5211位于正极极片521的端部，使得正负极极片522端部的容量的比值CB值得以提升，从而使得负极极片522提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片522的端部发生析出形成金属枝晶的风险，提高二次电池5的安全性能。示例性地，C12-C11可以为1mAh/g、5mAh/g、10mAh/g、20mAh/g、50mAh/g、80mAh/g、100mAh/g、120mAh/g、150mAh/g、180mAh/g、200mAh/g、250mAh/g、280mAh/g、300mAh/g、320mAh/g、350mAh/g、400mAh/g、450mAh/g或500mAh/g；或者是上述任意两个数值组成的范围。
正极极片521满足公式1mAh/g≤C12-C13≤500mAh/g时，正极连接部5213的克容量大于第二正极部5212的克容量，第二正极部5212的克容量相对较低，鉴于第二正极部5212位于正极极片521的端部，使得正负极极片522端部的容量的比值CB值得以提升，从而使得负极极片522提供的金属空位能够接受更多的金属离子，从而能够降 低金属离子在负极极片522的端部发生析出形成金属枝晶的风险，提高二次电池5的安全性能。示例性地，C12-C13可以为1mAh/g、5mAh/g、10mAh/g、20mAh/g、50mAh/g、80mAh/g、100mAh/g、120mAh/g、150mAh/g、180mAh/g、200mAh/g、250mAh/g、280mAh/g、300mAh/g、320mAh/g、350mAh/g、400mAh/g、450mAh/g或500mAh/g；或者是上述任意两个数值组成的范围。
在一些实施方式中，第一正极部5211和第二正极部5212在正极极片521宽度方向的尺寸相同。
第一正极部5211和第二正极部5212为正极极片521的两个端部，其在二次电池5充放电过程中的动力学性能基本相同，故将第一正极部5211和第二正极部5212的宽度方向的尺寸设置为基本相同，可以进一步保证正极极片521整体动力学性能的一致性。并且，有利于正极膜层的加工成型。
在一些实施方式中，第一正极部5211和第二正极部5212采用相同的材质，相同材质的脱嵌锂过程发生的反应基本相同，有利于进一步保证正极极片521整体动力学性能的一致性。并且，有利于正极膜层的加工成型。
在一些实施方式中，负极极片522包括沿其自身宽度方向彼此相对的两个第二边缘，由第二边缘指向与负极极片522的中心线的方向上，负极极片522的克容量呈逐渐减少趋势。负极极片522宽度方向上的端部的克容量相对较高，能够提高更多的金属空位，接受更多的金属离子，从而能够降低金属离子在负极极片522的端部发生析出形成金属枝晶的风险，提高二次电池的安全性能。在本申请中，负极极片522的中心线是指垂直于宽度方向的中心线，即两个第二边缘相对于该中心线对称。
如图7所示，在一些实施方式中，负极极片522包括第一负极部5221、第二负极部5222和负极连接部5223；第一负极部5221的克容量为C21；第二负极部5222与第一负极部5221沿负极极片522的宽度方向彼此相对，第二负极部5222的克容量为C22；以及负极连接部5223设置于第一负极部5221和第二负极部5222之间，且连接第一负极部5221和第二负极部5222，负极连接部5223的克容量为C23，负极极片522满足：1mAh/g≤C21-C22≤500mAh/g；和/或1mAh/g≤C23-C22≤500mAh/g。
第一负极部5221和第二负极部5222位于负极极片522沿其自身宽度方向的端部，例如第一负极部5221可以靠近负极极耳部设置并与负极极耳部电连接，第二负极部5222可以远离负极极耳部设置；当然，第二负极部5222可以靠近负极极耳部设置并与负极极耳部电连接，第一负极部5221可以远离负极极耳部设置。在本申请中负极极片522可以包括负极极耳部，即负极极耳部可以与负极集流体一体成型，当然，负极极耳部也可以与负极集流体独立设置后连接为一体。
第一负极部5221、第二负极部5222和负极连接部5223可以分别涂覆负极活性材料，负极活性材料的材质可以全部相同，也可以两两不同；可选地，第一负极部5221和第二负极部5222可以采用相同的材质。第一负极部5221、第二负极部5222和负极连接部5223的涂布重量可以全部相同，当然也可以两两不同；可选地，第一负极部5221和第二负极部5222可以采用相同的涂布重量。在第一负极部5221、第二负极 部5222和负极连接部5223采用相同的负极活性材料时，可以在不同的区域涂覆不同的涂布重量，以使各区域的克容量不同。在第一负极部5221、第二负极部5222和负极连接部5223采用相同的涂布重量时，可以在不同的区域涂覆不同材质的负极活性材料，以使各区域的克容量不同；此种方式所形成的不同区域的负极膜层的厚度基本相同，更有利于形成稳定的负极膜层。
负极极片522满足公式1mAh/g≤C21-C22≤500mAh/g时，负极连接部5223的克容量小于第一负极部5221的克容量，第一负极部5221的克容量相对较高，鉴于第一负极部5221位于负极极片522的端部，使得正负极极片522端部的容量的比值CB值得以提升，从而使得负极极片522提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片522的端部发生析出形成金属枝晶的风险，提高二次电池5的安全性能。示例性地，C21-C22可以为1mAh/g、5mAh/g、10mAh/g、20mAh/g、50mAh/g、80mAh/g、100mAh/g、120mAh/g、150mAh/g、180mAh/g、200mAh/g、250mAh/g、280mAh/g、300mAh/g、320mAh/g、350mAh/g、400mAh/g、450mAh/g或500mAh/g；或者是上述任意两个数值组成的范围。
负极极片522满足公式1mAh/g≤C23-C22≤500mAh/g时，负极连接部5223的克容量小于第二负极部5222的克容量，第二负极部5222的克容量相对较高，鉴于第二负极部5222位于负极极片522的端部，使得正负极极片522端部的容量的比值CB值得以提升，从而使得负极极片522提供的金属空位能够接受更多的金属离子，从而能够降低金属离子在负极极片522的端部发生析出形成金属枝晶的风险，提高二次电池5的安全性能。示例性地，C23-C22可以为1mAh/g、5mAh/g、10mAh/g、20mAh/g、50mAh/g、80mAh/g、100mAh/g、120mAh/g、150mAh/g、180mAh/g、200mAh/g、250mAh/g、280mAh/g、300mAh/g、320mAh/g、350mAh/g、400mAh/g、450mAh/g或500mAh/g；或者是上述任意两个数值组成的范围。
在一些实施方式中，第一负极部5221和第二负极部5222在负极极片522宽度方向的尺寸相同。
第一负极部5221和第二负极部5222为负极极片522的两个端部，其在二次电池5充放电过程中的动力学性能基本相同，故将第一负极部5221和第二负极部5222的宽度方向的尺寸设置为基本相同，可以进一步保证负极极片522整体动力学性能的一致性。并且，有利于负极膜层的加工成型。
在一些实施方式中，第一负极部5221和第二负极部5222采用相同的材质，相同材质的脱嵌锂过程发生的反应基本相同，有利于进一步保证负极极片522整体动力学性能的一致性。并且，有利于负极膜层的加工成型。
如图8所示，在一些实施方式中，正极极片521可以包括第一正极部5211、第二正极部5212和正极连接部5213。负极极片522包括第一负极部5221、第二负极部5222和负极连接部5223。
如图8和图9所示，在一些实施方式中，正极极片521沿第一方向Y的投影位于隔离膜523沿第一方向Y的投影内。隔离膜523能够覆盖正极极片521，起到对正极 极片521和负极极片522的隔绝作用，能够保证正极极片521的端部和负极极片522的端部基本不会接触而导致发生短路等情况，由此提高二次电池5的安全性能。
在一些实施方式中，正极极片521沿其自身宽度方向的尺寸小于或等于隔离膜523沿其自身宽度方向的尺寸。图8示出了隔离膜523沿其自身宽度方向的尺寸大于正极极片521沿其自身宽度方向的尺寸的情况，图9示出了隔离膜523沿其自身宽度方向的尺寸等于正极极片521沿其自身宽度方向的尺寸的情况。在本申请中，正极极片521的宽度方向和隔离膜523的宽度方向平行，图中的Z方向表示宽度方向。
隔离膜523能够在宽度方向上对正极极片521和负极极片522起到良好的隔绝作用，尤其是在正极极片521的宽度尺寸大于负极极片522的宽度尺寸的情况下，隔离膜523能够有效隔绝正极极片521和负极极片522，降低二者的端部接触并导致短路的风险，进一步提高二次电池5的安全性能。可选地，正极极片521沿其自身宽度方向的尺寸为A2，隔离膜523沿其自身宽度方向的尺寸为A3，0mm≤A3-A2≤6mm；可选地，0＜A3-A2≤6mm。示例性地，A3-A2可以为0、1mm、2mm、3mm、4mm、5mm或6mm；或者是上述任意两个数值组成的范围。
在一些实施方式中，二次电池5还包括电解液。
电解液在正极极片521和负极极片522之间起到传导金属离子的作用，本申请的电解液可采用本领域公知的用于二次电池5的电解液。电解液包括锂盐和有机溶剂。
作为示例，锂盐可包括选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)和四氟草酸磷酸锂(LiTFOP)中的一种或多种的组合。
作为示例，有机溶剂可包括选自碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)中的一种或多种的组合。
本申请的电解液可以按照本领域常规的方法制备。例如，可以将添加剂、溶剂、电解质盐等混合均匀，得到电解液。各物料的添加顺序并没有特别的限制，例如，可以将添加剂、电解质盐等加入到非水溶剂中混合均匀，得到非水电解液。
在本申请中，电解液中各组分及其含量可以按照本领域已知的方法测定。例如，可以通过气相色谱-质谱联用法(GC-MS)、离子色谱法(IC)、液相色谱法(LC)、核磁共振波谱法(NMR)等进行测定。
需要说明的是，本申请的电解液测试时，可直接取新鲜制备的电解液，也可以从二次电池5中获取电解液。从二次电池5中获取电解液的一个示例性方法包括如下步 骤：将二次电池5放电至放电截止电压(为了安全起见，一般使电池处于满放状态)后进行离心处理，之后取适量离心处理得到的液体即为非水电解液。也可以从二次电池5的注液口直接获取非水电解液。
本申请的二次电池5的制备方法是公知的。在一些实施例中，可将正极极片521、隔离膜523、负极极片522和电解液组装形成二次电池5。作为示例，可将正极极片521、隔离膜523、负极极片522经卷绕工艺或叠片工艺形成电极组件52，将电极组件52置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池5。
在本申请的一些实施例中，根据本申请的二次电池5可以组装成电池模块，电池模块所含二次电池5的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图10是作为一个示例的电池模块4的示意图。如图10所示，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图11和图12是作为一个示例的电池包1的示意图。如图11和图12所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
第二方面，本申请提供一种用电装置，用电装置包括本申请的二次电池、电池模块和电池包中的至少一种。二次电池、电池模块和电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图1是作为一个示例的用电装置的示意图。该用电装置6为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包1或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说 明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
1、正极极片的制备
采用厚度为12μm的铝箔作为正极集流体。
将正极活性材料NCM333、导电剂炭黑、粘结剂聚偏氟乙烯(PVDF)按重量比97.5:1.4:1.1在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。
2、负极极片的制备
采用厚度为8μm的铜箔作为负极集流体。
将负极活性材料石墨、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)、导电剂炭黑(Super P)按重量比96.2:1.8:1.2:0.8在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
3、隔离膜
采用多孔聚乙烯(PE)膜作为隔离膜。
4、电解液的制备
在含水量小于10ppm的环境下，将非水有机溶剂碳酸乙烯酯EC、碳酸二乙酯DMC按照体积比1:1进行混合得到电解液溶剂，随后将锂盐和混合后的溶剂混合，配置成锂盐浓度为1mol/L的电解液。
5、二次电池的制备
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离作用，然后卷绕得到电极组件；将电极组件置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到锂离子电池。
实施例2
实施例2-1至实施例2-4按照实施例1类似的方法制备，与实施例1不同的是，实施例2-1至实施例2-4调整了正极极片的宽度尺寸A2。
实施例3
实施例3-1至实施例3-3按照实施例1类似的方法制备，与实施例1不同的是，实施例3-1至实施例2-3调整了隔离膜的宽度尺寸A3。
实施例4
实施例4-1至实施例4-5按照实施例1类似的方法制备，与实施例1不同的是，实施例4-1至实施例4-5调整了正极连接部的克容量C12。
实施例5
实施例5-1至实施例5-5按照实施例1类似的方法制备，与实施例1不同的是，实施例5-1至实施例5-5调整了负极连接部的克容量C22。
对比例
对比例按照实施例1类似的方法制备，与实施例1不同的是，对比例调整了负极极片的宽度尺寸A1。
实施例1至实施例5以及对比例的参数如表1和表2所示。
表1
Figure PCTCN2022114517-appb-000001
表2
Figure PCTCN2022114517-appb-000002
Figure PCTCN2022114517-appb-000003
测试部分
1、初始克容量测定
第一正极部、第二正极部、正极连接部的测试方法类似，以第一正极部为例说 明其测试过程：
将第一正极部的材料、导电剂炭黑、粘结剂聚偏氟乙烯(PVDF)按重量比97.5:1.4:1.1在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片；之后以金属锂片为对电极，以聚乙烯(PE)薄膜作为隔离膜，滴入几滴与上述二次电池相同的电解液，并在氩气保护的手套箱中组装成CR2430型扣式电池。
将所得扣式电池静置12h后，在25℃下，以0.05C恒流放电至0.005V，静置10min，以50μA的电流再恒流放电至0.005V，静置10min，以10μA再恒流放电至0.005V；然后以0.1C恒流充电至2V，记录充电容量。充电容量与第一正极部的质量的比值即为第一负极部的初始克容量。
第一负极部、第二负极部、负极连接部的测试方法类似，以第一负极部为例说 明其测试过程：
将第一负极部的材料、导电剂炭黑、粘结剂聚偏氟乙烯(PVDF)按质量比91.6:1.8:6.6与溶剂N-甲基吡咯烷酮(NMP)中混合均匀，制成浆料；将制备好的浆料涂覆于铜箔上，于烘箱中干燥后备用；之后以金属锂片为对电极，以聚乙烯(PE)薄膜作为隔离膜，滴入几滴与上述二次电池相同的电解液，并在氩气保护的手套箱中组装成CR2430型扣式电池。
将所得扣式电池静置12h后，在25℃下，以0.05C恒流放电至0.005V，静置10min，以50μA的电流再恒流放电至0.005V，静置10min，以10μA再恒流放电至0.005V；然后以0.1C恒流充电至2V，记录充电容量。充电容量与第一负极部质量的比 值即为第一负极部的初始克容量。
2、正极极片、负极极片和隔离膜的尺寸测定
将上述制备的正极极片、负极极片或隔离膜，采用万分尺测量其宽度尺寸。
3、能量密度测定
在25℃下，将实施例和对比例制备得到的锂离子电池以1C倍率满充、以1C倍率满放，记录此时的实际放电能量；在25℃下，使用电子天平对该锂离子电池进行称重；锂离子电池1C实际放电能量与锂离子电池重量的比值即为锂离子电池的实际能量密度。
其中，实际能量密度小于预期能量密度的80％时，认为电池实际能量密度非常低；实际能量密度大于等于预期能量密度的80％且小于预期能量密度的95％时，认为电池实际能量密度偏低；实际能量密度大于等于预期能量密度的95％且小于预期能量密度的105％时，认为电池实际能量密度适中；实际能量密度大于等于预期能量密度的105％且小于预期能量密度的120％时，认为电池实际能量密度偏高；实际能量密度为预期能量密度的120％以上时，认为电池实际能量密度非常高。
测试结果
本申请改善二次电池的能量密度性能方面的作用如表3所示。
表3
项目 能量密度
实施例1 175.0
实施例2-1 173.5
实施例2-2 177.5
实施例2-3 180.0
实施例2-4 172.5
实施例3-1 175.25
实施例3-2 174.50
实施例3-3 173.75
实施例4-1 174.0
实施例4-2 185.0
实施例4-3 205.0
实施例4-4 225.0
实施例4-5 235.0
实施例5-1 176.0
实施例5-2 166.0
实施例5-3 146.0
实施例5-4 126.0
实施例5-5 116.0
对比例 170.0
对比例中的正极极片的尺寸小于负极极片的尺寸，其正极极片的空间利用率较低，本申请实施例如实施例1、实施例2-1至实施例2-4通过将正极极片的尺寸设置为大于或等于负极极片的尺寸，可以显著提高正极极片的空间利用率。
实施例3-1至实施例3-3对隔离膜的尺寸进行了调节，可以显著改善隔离膜对正极极片和负极极片之间的隔绝作用，且能够保证二次电池的能量密度。
实施例4-1至实施例4-5对正极极片的克容量进行调节，随着正极极片的克容量的增多，二次电池的能量密度得到提升。但是正极极片整体结构上克容量分布趋近于均匀时，正极极片的整体性能较为均一和稳定。
实施例5-1至实施例5-5对负极极片的克容量进行调节，可以对应改善正极极片的克容量，从而调节二次电池的能量密度。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种二次电池，包括：
    外壳组件；
    设置于所述外壳组件内的电极组件，所述电极组件包括正极极片、负极极片和设置于所述正极极片和所述负极极片之间的隔离膜，所述负极极片沿第一方向的投影位于所述正极极片沿所述第一方向的投影内，其中，所述第一方向垂直于所述外壳组件的高度方向。
  2. 根据权利要求1所述的二次电池，其中，
    所述负极极片沿所述第一方向的投影与所述正极极片沿所述第一方向的投影重叠。
  3. 根据权利要求1或2所述的二次电池，其中，
    所述负极极片沿其自身宽度方向的尺寸小于或等于所述正极极片沿其自身宽度方向的尺寸；
    可选地，所述负极极片沿其自身宽度方向的尺寸为A1，所述正极极片沿其自身宽度方向的尺寸为A2，-15mm≤A1-A2≤-2mm。
  4. 根据权利要求1至3中任一项所述的二次电池，其中，所述正极极片包括沿其自身宽度方向彼此相对的两个第一边缘，由所述第一边缘指向所述正极极片的中心线的方向上，所述正极极片的克容量呈逐渐增加趋势。
  5. 根据权利要求1至4中任一项所述的二次电池，其中，所述正极极片包括：
    第一正极部，所述第一正极部的克容量为C11；
    第二正极部，其与所述第一正极部沿所述正极极片的宽度方向彼此相对，所述第二正极部的克容量为C12；以及
    正极连接部，其设置于所述第一正极部和所述第二正极部之间，且连接所述第一正极部和所述第二正极部，所述正极连接部的克容量为C13，
    所述正极极片满足：1mAh/g≤C12-C11≤500mAh/g；和/或1mAh/g≤C12-C13≤500mAh/g。
  6. 根据权利要求5所述的二次电池，其中，
    所述第一正极部和所述第二正极部在所述正极极片宽度方向的尺寸相同。
  7. 根据权利要求5或6所述的二次电池，其中，
    所述第一正极部和所述第二正极部采用相同的材质。
  8. 根据权利要求1至7中任一项所述的二次电池，其中，所述负极极片包括沿其自身宽度方向彼此相对的两个第二边缘，由所述第二边缘指向与所述负极极片的中心线的方向上，所述负极极片的克容量呈逐渐减少趋势。
  9. 根据权利要求1至8中任一项所述的二次电池，其中，所述负极极片包括：
    第一负极部，所述第一负极部的克容量为C21；
    第二负极部，其与所述第一负极部沿所述负极极片的宽度方向彼此相对，所述第二负极部的克容量为C22；以及
    负极连接部，其设置于所述第一负极部和所述第二负极部之间，且连接所述第一负极部和所述第二负极部，所述负极连接部的克容量为C23，
    所述负极极片满足：1mAh/g≤C21-C22≤500mAh/g；和/或1mAh/g≤C23-C22≤500mAh/g。
  10. 根据权利要求9所述的二次电池，其中，
    所述第一负极部和所述第二负极部在所述负极极片宽度方向的尺寸相同。
  11. 根据权利要求9或10所述的二次电池，其中，
    所述第一负极部和所述第二负极部采用相同的材质。
  12. 根据权利要求1至11中任一项所述的二次电池，其中，
    所述正极极片沿所述第一方向的投影位于所述隔离膜沿所述第一方向的投影内。
  13. 根据权利要求12所述的二次电池，其中，
    所述正极极片沿其自身宽度方向的尺寸小于或等于所述隔离膜沿其自身宽度方向的尺寸；
    可选地，所述正极极片沿其自身宽度方向的尺寸为A2，所述隔离膜沿其自身宽度方向的尺寸为A3，0mm≤A3-A2≤6mm。
  14. 一种电池模块，包括根据权利要求1至13中任一项所述的二次电池。
  15. 一种电池包，包括根据权利要求14所述的电池模块。
  16. 一种用电装置，包括根据权利要求1至13中任一项所述的二次电池、权利要求14所述的电池模块或权利要求15所述的电池包。
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JP2015095412A (ja) * 2013-11-13 2015-05-18 トヨタ自動車株式会社 二次電池の電極体および二次電池
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CN114430018A (zh) * 2022-01-19 2022-05-03 宁德新能源科技有限公司 一种电化学装置及包含该电化学装置的电子装置
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Publication number Priority date Publication date Assignee Title
US20110129722A1 (en) * 2008-07-09 2011-06-02 Tetsuya Yoneda Flat secondary battery and method of manufacturing the same
JP2015095412A (ja) * 2013-11-13 2015-05-18 トヨタ自動車株式会社 二次電池の電極体および二次電池
CN205231171U (zh) * 2015-11-30 2016-05-11 上海比亚迪有限公司 一种锂离子电池负极极片及电池
CN214384767U (zh) * 2021-03-18 2021-10-12 郭彬彬 一种安全型锂离子电池
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