Secondary battery, battery pack and energy storage system

Abstract

The utility model discloses a secondary battery, a battery pack and an energy storage system, and belongs to the technical field of batteries. The secondary battery comprises a battery cell and a shell for accommodating the battery cell, the battery cell comprises a negative pole piece, a positive pole piece, a diaphragm and an electrolyte, the negative pole piece, the positive pole piece and the diaphragm are arranged in a winding manner, and the negative pole piece and the positive pole piece are isolated by the diaphragm to form a winding type battery cell; the tail end of the negative pole piece in the winding direction respectively exceeds the tail end of the positive pole piece in the winding direction and the tail end of the diaphragm in the winding direction, and the negative pole piece forms the outermost layer of the winding type battery cell; the shell is inert relative to the active ions, and the active ions are ions which are deintercalated and intercalated between the negative pole piece and the positive pole piece through the electrolyte. The size of the battery cell of the secondary battery can be designed to be smaller, and the energy density and the heat dissipation effect of the battery cell can be improved.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of battery technology, and in particular to secondary batteries, battery packs, and energy storage systems. Background Art

[0002] Sodium ion batteries use sodium ions (Na + ) Reversible intercalation and deintercalation between the positive and negative electrodes realizes charging and discharging. Similar to the structure of lithium-ion batteries, the battery cell of sodium-ion batteries includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The positive electrode sheet and the negative electrode sheet are separated by a separator.

[0003] In the related art, the negative electrode sheet of the sodium ion battery is designed to be oversized relative to the positive electrode sheet, and the diaphragm is designed to be oversized relative to the positive electrode sheet and the negative electrode sheet. When the battery cell of the sodium ion battery is designed as a winding structure, the diaphragm wraps the tail end of the negative electrode sheet and is sequentially extended for further winding, thereby completely wrapping the outermost negative electrode sheet.

[0004] However, the diaphragm is used in large quantities, which results in a larger battery cell size, lower battery cell energy density, and is not conducive to the heat dissipation effect of the battery cell. Utility Model Content

[0005] The embodiments of the present disclosure provide a secondary battery, a battery pack, and an energy storage system, which can solve the technical problems existing in the related technologies.

[0006] On the one hand, an embodiment of the present disclosure provides a secondary battery, which comprises: a battery cell and a shell for accommodating the battery cell; the battery cell comprises: a negative electrode sheet, a positive electrode sheet, a separator and an electrolyte, the negative electrode sheet, the positive electrode sheet and the separator are wound and arranged, and the negative electrode sheet and the positive electrode sheet are separated by the separator to form a wound battery cell; the ends of the negative electrode sheet along the winding direction respectively extend beyond the ends of the positive electrode sheet along the winding direction and the ends of the separator along the winding direction, and the negative electrode sheet constitutes the outermost layer of the wound battery cell; the shell is non-reactive with respect to active ions, wherein the active ions are ions that are deintercalated and intercalated between the negative electrode sheet and the positive electrode sheet via the electrolyte.

[0007] The secondary battery provided by the embodiment of the present disclosure has an outer shell that is inert relative to the active ions released in the battery cell, and during the charge and discharge process of the secondary battery, no electrochemical reaction occurs between the outer shell and the active ions released in the battery cell. On this basis, for the wound battery cell, the negative electrode sheet constitutes the outermost layer of the wound battery cell by making the end of the negative electrode sheet along the winding direction exceed the end of the positive electrode sheet along the winding direction and the end of the diaphragm along the winding direction respectively. It can be seen that the length of the diaphragm along the winding direction enables it to cover the positive electrode sheet, avoiding the diaphragm to be extended additionally to cover the negative electrode sheet, effectively reducing the amount of diaphragm, avoiding increasing the occupied volume of inactive materials in the battery cell, and improving the space utilization rate of active materials in the battery cell. On the one hand, this is conducive to reducing the volume of the battery cell, and on the other hand, when the volume of the battery cell is designed to be greater than or equal to the volume of the related art, the proportion of the negative electrode sheet and the positive electrode sheet in the battery cell is increased compared with the related art, which is conducive to improving the energy density of the battery cell. Moreover, the reduced amount of diaphragm is also conducive to increasing the heat conduction rate between the battery cell and the shell, and improving the heat dissipation effect of the battery cell. Although the negative electrode sheet constitutes the outermost layer of the wound battery cell in the secondary battery, since the shell is non-reactive to active ions, even if the negative electrode sheet contacts the shell, it will not cause electrochemical corrosion of the shell.

[0008] In some possible implementations, the end of the separator exceeds the end of the positive electrode sheet. By making the end of the separator exceed the end of the positive electrode sheet, it is ensured that the separator completely covers the positive electrode sheet, thereby ensuring complete and reliable isolation between the negative electrode sheet and the positive electrode sheet.

[0009] In some possible implementations, the end of the separator exceeds the end of the positive electrode plate by 1 mm to 10 mm.

[0010] In some possible implementations, the battery cell further includes an insulating protective member, which is disposed at the end of the positive electrode sheet. By disposing the insulating protective member at the end of the positive electrode sheet, the end of the positive electrode sheet is separated from the negative electrode sheet, so as to prevent the negative electrode sheet and the positive electrode sheet from contacting each other and causing an internal short circuit when the end of the positive electrode sheet damages the diaphragm, thereby ensuring the safety of the battery cell.

[0011] In some possible implementations, the insulating protection member is coated on the end of the positive electrode plate, thereby improving the operating reliability of the insulating protection member.

[0012] In some possible implementations, the insulating protection member is an elastic member. Since the elastic member will produce a certain elastic deformation when under pressure, it can alleviate the local stress caused by the end of the positive electrode plate on the diaphragm when under pressure, thereby reducing the risk of damage to the diaphragm.

[0013] In some possible implementations, the secondary battery is a sodium ion battery, and the shell is a copper shell, an iron shell, a stainless steel shell, an aluminum shell, or an aluminum alloy shell.

[0014] On the other hand, an embodiment of the present disclosure provides a battery pack, which includes a plurality of secondary batteries as described above, wherein the plurality of secondary batteries are connected in series, in parallel, or in a mixed manner.

[0015] In yet another aspect, an embodiment of the present disclosure provides an energy storage system, the energy storage system comprising a power converter and at least one battery pack as described above;

[0016] The power converter is used to convert the voltage output by the battery pack into power and output it to a power grid or a load, and / or to convert the voltage output by an external power source into power and output it to the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of an exemplary secondary battery provided in an embodiment of the present disclosure;

[0018] Figure 2 A schematic diagram of a structural schematic diagram of an exemplary wound-type battery cell provided in an embodiment of the present disclosure;

[0019] Figure 3 A schematic diagram of the structure of another exemplary wound battery cell provided in an embodiment of the present disclosure;

[0020] Figure 4 A schematic diagram of the structure of an exemplary negative electrode sheet provided in an embodiment of the present disclosure;

[0021] Figure 5 A schematic diagram of the structure of an exemplary positive electrode plate provided in an embodiment of the present disclosure.

[0022] Figure 2 and Figure 3 In order to distinguish the negative electrode sheet, the positive electrode sheet and the separator, the negative electrode sheet 11 is represented by a thinner solid line, the positive electrode sheet 12 is represented by a thicker solid line, and the separator 13 is represented by a double line. The thinner line of the negative electrode sheet 11 does not mean that its thickness is thinner. It is only used to distinguish the positive and negative electrode sheets in the figure. In the embodiment of the present disclosure, the thickness of the negative electrode sheet 11 and the positive electrode sheet 12 can be the same or different (for example, the thickness of the negative electrode sheet 11 can be greater than or less than the thickness of the positive electrode sheet 12).

[0023] The reference numerals represent:

[0024] 100. Battery cell;

[0025] 11. Negative electrode;

[0026] 110. end of the negative electrode plate; 111. negative electrode current collector; 112. negative electrode tab; 113. negative electrode active material layer;

[0027] 12. Positive electrode;

[0028] 120, end of the positive electrode plate; 121, positive electrode current collector; 122, positive electrode ear; 123, positive electrode active material layer;

[0029] 13. diaphragm; 130. end of diaphragm;

[0030] 14. Insulation protection parts;

[0031] 200. outer shell; 21. casing; 22. cover. DETAILED DESCRIPTION

[0032] In the description of the embodiments of the present disclosure, it should be understood that the terms "inside", "outside", "top", "bottom", "vertical", "horizontal", "height", "depth" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. When the product is placed in different postures, the orientation may change, and therefore cannot be understood as a limitation on the embodiments of the present disclosure.

[0033] The wound battery cell involved in the embodiment of the present disclosure has a preparation method as follows: the negative electrode sheet, the positive electrode sheet and the separator are arranged in order, and the starting end of the separator is fixed on the winding needle, and as the winding needle rotates, the negative electrode sheet, the positive electrode sheet and the separator are wound from the inside to the outside into a multi-layer structure to form a wound battery cell. The rotation direction of the winding needle is also the winding direction of the wound battery cell, which can be in the clockwise direction or in the counterclockwise direction.

[0034] Correspondingly, the head end of the negative electrode sheet along the winding direction, the head end of the positive electrode sheet along the winding direction, and the head end of the separator along the winding direction involved in the embodiments of the present disclosure refer to the ends corresponding to them at the starting stage of winding, and can also be understood as the starting end of winding. The end of the negative electrode sheet along the winding direction, the end of the positive electrode sheet along the winding direction, and the end of the separator along the winding direction involved in the embodiments of the present disclosure refer to the ends corresponding to them at the ending stage of winding, and can also be understood as the ending end of winding.

[0035] In addition, for the central area of ​​the wound battery cell, please refer to Figure 2The separator is wound multiple times before the negative electrode and the positive electrode. Thus, the separator forms the central area of ​​the wound cell (the head end of the separator is located in the innermost layer of the wound cell), giving it good insulation isolation function. On this basis, the separator, the negative electrode and the positive electrode are wound together until the winding is completed.

[0036] In the related art, the structural design of the wound cell of the sodium ion battery is generally consistent with that of the wound cell of the lithium ion battery. For the lithium ion battery, the active ions released in the cell are lithium ions. When the lithium ions come into contact with the aluminum shell, an electrochemical reaction will occur, which will cause the aluminum shell to corrode. Therefore, in order to achieve insulation protection between the cell and the aluminum shell, for its wound cell, the diaphragm wraps the tail end of the negative electrode sheet and extends in sequence to further wind, so as to completely wrap the outermost negative electrode sheet. Sodium ion batteries and lithium ion batteries are secondary batteries with similar working principles. Usually, the wound cell of the sodium ion battery is also arranged in this way. For example, after completing the coating of the tail end of the negative electrode sheet, the diaphragm will continue to wind one, two or three circles, which makes the diaphragm used in large quantities, resulting in a larger cell volume and a lower cell energy density. Moreover, it is not conducive to the heat dissipation effect of the cell.

[0037] In view of the technical problems existing in the related art, the present disclosure provides a secondary battery, as shown in the attached Figure 1 As shown, the secondary battery comprises: a battery cell 100 and a housing 200 for accommodating the battery cell 100. The battery cell 100 comprises: a negative electrode sheet 11, a positive electrode sheet 12, a separator 13 and an electrolyte, further combined with Figure 2 It can be seen that the negative electrode sheet 11 , the positive electrode sheet 12 and the separator 13 are wound and arranged, and the negative electrode sheet 11 and the positive electrode sheet 12 are separated by the separator 13 to form a wound battery cell.

[0038] In the secondary battery provided by the embodiment of the present disclosure, the end 110 of the negative electrode sheet 11 along the winding direction respectively exceeds the end 120 of the positive electrode sheet 12 along the winding direction and the end 130 of the separator 13 along the winding direction, and the negative electrode sheet 11 constitutes the outermost layer of the wound battery cell. In addition, the shell 200 is inert with respect to active ions, wherein the active ions are ions that are deintercalated and intercalated between the negative electrode sheet and the positive electrode sheet via the electrolyte.

[0039] The “shell is inert with respect to the active ions” involved in the embodiments of the present disclosure means that, during the charge and discharge process of the secondary battery, no electrochemical reaction occurs between the shell 200 and the active ions released from the battery cell 100, that is, the shell 200 is non-reactive with respect to the active ions, which means that even if the negative electrode plate 11 contacts the shell 200, electrochemical corrosion of the shell 200 will not occur.

[0040] The secondary battery provided by the embodiment of the present disclosure has a shell 200 which is inert relative to the active ions released in the battery cell 100. During the charge and discharge process of the secondary battery, no electrochemical reaction occurs between the shell 200 and the active ions released in the battery cell 100. On this basis, for the wound battery cell 100, the negative electrode sheet 11 constitutes the outermost layer of the wound battery cell by making the end 110 of the negative electrode sheet 11 along the winding direction exceed the end 120 of the positive electrode sheet 12 along the winding direction and the end 130 of the diaphragm 13 along the winding direction. It can be seen that the length of the diaphragm 13 along the winding direction is sufficient to cover the positive electrode sheet 12, avoiding the diaphragm 13 from being extended additionally to cover the negative electrode sheet 11, effectively reducing the amount of the diaphragm 13, avoiding increasing the occupied volume of the inactive materials in the battery cell 100, and improving the space utilization rate of the active materials in the battery cell 100. On the one hand, this is conducive to reducing the volume of the battery cell 100. On the other hand, when the volume of the battery cell 100 is designed to be greater than or equal to the volume of the related art, the proportion of the negative electrode sheet 11 and the positive electrode sheet 12 in the battery cell 100 is increased compared with the related art, which is conducive to improving the energy density of the battery cell. Moreover, the reduction in the amount of the diaphragm 13 is also conducive to increasing the heat conduction rate between the battery cell 100 and the shell 200, and improving the heat dissipation effect of the battery cell 100. Although in this secondary battery, the negative electrode sheet 11 constitutes the outermost layer of the wound battery cell, since the shell 200 is inert relative to the active ions, even if the negative electrode sheet 11 contacts the shell 200, it will not cause electrochemical corrosion of the shell 200.

[0041] It can be seen that the embodiment of the present disclosure can directly adopt the negative electrode plate 11 as the end of the secondary battery cell 100 whose active ions will not undergo electrochemical reaction with the outer shell 200. The end 110 of the negative electrode plate 11 is overlapped with the outermost surface of the negative electrode plate 11, and the negative electrode plate 11 is coated with the diaphragm 13. Even if the negative electrode plate 11 is overlapped with the outer shell 200, it will not cause electrochemical corrosion with the outer shell 200, and the heat conduction efficiency between the battery cell 100 and the outer shell 200 can also be improved.

[0042] In addition, the active ions released by the battery cell 100 based on the secondary battery will not undergo electrochemical reaction with the outer shell 200. The outside of the wound battery cell 100 provided in the embodiment of the present disclosure does not need to be additionally arranged with an insulating layer or insulating film, such as Mylar film. Compared with related technologies, this is also beneficial to improving the heat dissipation effect of the battery cell 100.

[0043] It should be noted that, for the wound cell 100 involved in the embodiment of the present disclosure, the head end of the separator 13, that is, the starting end, is far beyond the head ends of the negative electrode sheet 11 and the positive electrode sheet 12, so that the separator 13 forms the innermost layer of the wound cell 100 to ensure that the head end of the negative electrode sheet 11 and the head end of the positive electrode sheet 12 are completely isolated by the separator 13. In addition, for one layer of negative electrode sheet 11 and one layer of positive electrode sheet 12, two layers of separator 13 are usually used to achieve insulation isolation.

[0044] In the disclosed embodiment, the end 130 of the separator 13 may extend beyond the end 120 of the positive electrode sheet 12 . It is not excluded that the end 130 of the separator 13 may also be flush with the end 120 of the positive electrode sheet 12 .

[0045] By making the end 130 of the separator 13 extend beyond the end 120 of the positive electrode sheet 12 , it is ensured that the separator 13 completely covers the positive electrode sheet 12 , thereby ensuring complete and reliable isolation between the negative electrode sheet 11 and the positive electrode sheet 12 .

[0046] In some examples, the end 130 of the diaphragm 13 exceeds the end 120 of the positive electrode plate 12 by a dimension of 1 mm to 10 mm, for example, including but not limited to 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc. Within this size range, the diaphragm 13 can not only reliably cover the positive electrode plate 12, but also avoid additional increase in the size of the diaphragm 13.

[0047] In the disclosed embodiment, the dimensions of the negative electrode sheet 11 and the positive electrode sheet 12 along the winding direction can be selected according to actual needs, and the dimension of the separator 13 along the winding direction can be adjusted according to the dimension of the positive electrode sheet 12 along the winding direction.

[0048] In some implementations, such as the attached Figure 3 As shown, the battery cell 100 provided in the embodiment of the present disclosure further includes an insulating protection member 14 , and the insulating protection member 14 is disposed at the end 120 of the positive electrode sheet 12 .

[0049] By providing an insulating protective member 14 at the end 120 of the positive electrode sheet 12, the end 120 of the positive electrode sheet 12 is isolated from the negative electrode sheet 11 to prevent the negative electrode sheet 11 and the positive electrode sheet 12 from contacting each other and causing an internal short circuit when the end 120 of the positive electrode sheet 12 damages the diaphragm 13, thereby ensuring the safety of the battery cell 100.

[0050] The insulating protective member 14 can be arranged at the end 120 of the positive electrode plate 12 in various ways. For example, the insulating protective member 14 is only arranged on the surface of the end 120 of the positive electrode plate 12 facing the diaphragm 13 (that is, the negative electrode plate 11), or, on this basis, the insulating protective member 14 is further arranged on the free end surface of the end 120 of the positive electrode plate 12.

[0051] In some examples, the insulating protective member 14 is wrapped around the end 120 of the positive electrode sheet 12. In this way, each portion of the end 120 of the positive electrode sheet 12 facing the negative electrode sheet 11 and the end surface portion of the end 120 thereof can be provided with the insulating protective member 14, so that the insulating protective member 14 can fully cover the end 120 of the positive electrode sheet 12, thereby improving the operating reliability of the insulating protective member 14.

[0052] Furthermore, the insulating protective member 14 can be an elastic member. Since the elastic member will produce a certain elastic deformation when under pressure, it can reduce the local stress caused by the end 120 of the positive electrode plate 12 on the diaphragm 13 when under pressure, thereby reducing the risk of damage to the diaphragm 13. For example, the elastic insulating protective member 14 can be prepared using a rubber material, which includes but is not limited to: styrene rubber, olefin rubber, diene rubber, vinyl chloride rubber, polyester rubber, silicone rubber, etc.

[0053] Exemplarily, the insulating protection member 14 is an elastic insulating tape, so that the insulating protection member 14 can be connected to the end 120 of the positive electrode plate 12 in an adhesive manner, making its arrangement more stable.

[0054] The housing 200 is used to provide a closed space. The battery cell 100 is accommodated in the housing 200 and its electrolyte is used as a transmission medium between the positive and negative electrodes. Figure 1 As shown, the housing 200 includes a shell 21 and a cover 22 , and the cover 22 is sealed and connected to a port of the shell 21 to form a closed space for accommodating the battery cell 100 .

[0055] The cover 22 can also be a battery cover plate, which covers the opening of the housing 21 to isolate the internal environment of the secondary battery from the external environment. The cover 22 can also be provided with functional components such as electrode terminals, pressure relief structures, and injection holes.

[0056] A sealing ring may also be provided between the port of the housing 21 and the cover 22 to achieve sealing between the housing 21 and the cover 22. The material of the sealing ring includes but is not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high in toughness and fatigue-resistant.

[0057] The shapes and sizes of the shell 21 and the cover 22 can be determined according to the specific shape and size of the battery cell 100. In addition, the shape of the cover 22 can be adapted to the shape of the shell 21 to form a housing 200 with a specific shape. For example, the shape of the housing 200 includes but is not limited to: a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc.

[0058] The shell 21 and the cover 22 may be made of a variety of materials, for example, including but not limited to metal materials such as copper, iron, stainless steel, aluminum, and aluminum alloy. In some examples, the outer surface of the shell 21 may also be provided with a coating, and the coating may be made of a variety of materials, including but not limited to corrosion-resistant materials such as Ni and Cr.

[0059] For example, the secondary battery provided in the embodiment of the present disclosure is a sodium ion battery, and the material of the shell 200 can be copper, iron, stainless steel, aluminum, aluminum alloy, etc., that is, the shell 200 is a copper shell, an iron shell, a stainless steel shell, an aluminum shell or an aluminum alloy shell. This includes that the material of the shell 21 can be copper, iron, stainless steel, aluminum, aluminum alloy, etc., and further, the material of the cover 22 can also be copper, iron, stainless steel, aluminum, aluminum alloy, etc.

[0060] In some examples, the secondary battery provided by the embodiments of the present disclosure is a battery cell.

[0061] In some examples, the secondary battery provided by the embodiments of the present disclosure may be in the form of a soft pack, such as a bag-type soft pack, and the material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0062] Taking the secondary battery involved in the above-mentioned embodiment of the present disclosure as a sodium ion battery as an example, the sodium ion battery relies on the movement of sodium ions between the positive electrode sheet 12 and the negative electrode sheet 11 to work. During the charging and discharging process, the active sodium ions are intercalated and deintercalated back and forth between the positive electrode sheet 12 and the negative electrode sheet 11. The diaphragm 13 is arranged between the positive electrode sheet 12 and the negative electrode sheet 11, which mainly plays the role of preventing the positive and negative electrodes from short-circuiting, and at the same time allows sodium ions to pass through.

[0063] In addition, although the embodiment of the present disclosure clearly states that the battery cell 100 of the sodium ion battery is a wound structure, the design of the end of the negative electrode plate 11 exceeding the end of the diaphragm 13 disclosed in the embodiment of the present disclosure is also applicable to stacked battery cells, especially when the diaphragm is adhesive.

[0064] Although the structures and arrangements of the negative electrode sheet 11 and the positive electrode sheet 12 are currently known, the embodiments of the present disclosure will still be described simply with reference to the two.

[0065] As attached Figure 4As shown, the negative electrode sheet 11 includes a negative electrode current collector 111, a negative electrode tab 112 and a negative electrode active material layer 113. The negative electrode active material layer 113 is disposed on at least one side of the negative electrode current collector 111. The negative electrode tab 112 is protrudingly disposed and connected to one side or two opposite sides of the negative electrode current collector 111. The negative electrode active material layer 113 may completely cover the corresponding surface of the negative electrode current collector 111. Figure 4 In order to illustrate the arrangement relationship of the various parts in the negative electrode sheet 11 , one side area of ​​the negative electrode active material layer 113 is cut to expose the negative electrode current collector 111 located thereunder.

[0066] The negative electrode current collector 111 may be a metal foil or a composite current collector. For example, the material of the negative electrode current collector 111 and the negative electrode tab 112 may be copper, aluminum, or a composite current collector. The composite current collector includes a polymer material base layer and a metal layer formed on at least one side of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on the surface of a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0067] The negative electrode active material in the negative electrode active material layer 113 may be a negative electrode active material such as soft carbon, hard carbon, etc. As an example, the negative electrode active material may include at least one of the following materials: organic chemicals such as carbonyl compounds, Schiff base compounds, organic free radical compounds and organic sulfides, soft carbon, hard carbon, metals that can form alloys with sodium, TiO2, etc. The metal that can form alloys with sodium may be selected from at least one of In, Si, Sn, Pb, P, As, Sb, and Bi, etc.

[0068] In some examples, the negative electrode active material layer 113 may further include a binder, which may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0069] In some examples, the negative active material layer 113 may further include a conductive agent, and the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0070] In some embodiments, the negative electrode active material layer 113 may further include an auxiliary agent, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0071] As attached Figure 5 As shown, the positive electrode sheet 12 includes a positive electrode current collector 121, a positive electrode tab 122 and a positive electrode active material layer 123. The positive electrode active material layer 123 is disposed on at least one side of the positive electrode current collector 121. The positive electrode tab 122 is protrudingly disposed and connected to one side or two opposite sides of the positive electrode current collector 121. The positive electrode active material layer 123 can completely cover the corresponding surface of the positive electrode current collector 121. Figure 5 In order to illustrate the arrangement relationship of the various parts in the positive electrode sheet 12, one side area of ​​the positive electrode active material layer 123 is cut to expose the positive electrode current collector 121 located thereunder.

[0072] The positive electrode current collector 121 may be a metal foil or a composite current collector. For example, the material of the negative electrode current collector 111 and the negative electrode tab 112 may be copper, aluminum, or a composite current collector. The composite current collector includes a polymer material base layer and a metal layer formed on at least one side of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on the surface of a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0073] The positive electrode active material in the positive electrode active material layer 123 includes, but is not limited to, layered oxide positive electrode materials, polyanion positive electrode materials, Prussian blue positive electrode materials, etc. The molecular formula of the layered oxide positive electrode material can be Na α (M x Mn y )O2, wherein M can be selected from one or more of Ni, Fe, Cu, Mg, Al, Co, Ti, Ca, and Zn. The polyanion positive electrode material can be one or more of Na4N2(PO4)2P2O7, Na3N2(PO4)3, and Na2NP2O7, and N can be selected from one or more of Fe, V, Mn, Co, Ti, Zr, and Ni.

[0074] In some examples, the positive active material layer 123 may further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0075] In some examples, the positive active material layer 123 may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0076] In some examples, the material of the diaphragm 13 can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The diaphragm 13 can be a single-layer film or a multi-layer composite film.

[0077] The battery involved in the embodiments of the present disclosure has application fields including but not limited to the following electrical devices: mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles and spacecraft, etc.

[0078] On the other hand, the embodiment of the present disclosure further provides a battery pack, which includes a plurality of any of the above-mentioned secondary batteries, and the plurality of secondary batteries are connected in series, parallel or hybrid. The "hybrid" mentioned here refers to series + parallel.

[0079] The battery pack provided by the embodiments of the present disclosure has all the advantages of the secondary batteries mentioned above.

[0080] On the other hand, an embodiment of the present disclosure further provides an energy storage system, which includes a power converter and at least one battery pack as shown above; the power converter is used to convert the voltage output by the battery pack into power and output it to a power grid or a load, and / or, convert the voltage output by an external power supply into power and output it to the battery pack.

[0081] The energy storage system provided by the embodiments of the present disclosure has all the advantages of the secondary batteries mentioned above.

[0082] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A secondary battery, characterized in that: The secondary battery comprises: a battery cell (100) and a housing (200) for accommodating the battery cell (100); The battery cell (100) comprises: a negative electrode sheet (11), a positive electrode sheet (12), a separator (13) and an electrolyte, wherein the negative electrode sheet (11), the positive electrode sheet (12) and the separator (13) are arranged in a wound manner, and the negative electrode sheet (11) and the positive electrode sheet (12) are separated by the separator (13) to form a wound battery cell; The end (110) of the negative electrode sheet (11) along the winding direction respectively exceeds the end (120) of the positive electrode sheet (12) along the winding direction and the end (130) of the separator (13) along the winding direction, and the negative electrode sheet (11) constitutes the outermost layer of the wound battery cell; The shell (200) is inert with respect to active ions, wherein the active ions are ions that are deintercalated and intercalated between the negative electrode plate and the positive electrode plate via the electrolyte.

2. The secondary battery according to claim 1, characterized in that: The end (130) of the separator (13) exceeds the end (120) of the positive electrode plate (12).

3. The secondary battery according to claim 2, characterized in that: The end (130) of the separator (13) exceeds the end (120) of the positive electrode plate (12) by a dimension of 1 mm to 10 mm.

4. The secondary battery according to claim 1, characterized in that: The battery cell (100) further comprises an insulating protection member (14), wherein the insulating protection member (14) is arranged at the end (120) of the positive electrode plate (12).

5. The secondary battery according to claim 4, characterized in that: The insulating protection member (14) is coated on the end (120) of the positive electrode plate (12).

6. The secondary battery according to claim 4, characterized in that: The insulating protection member (14) is an elastic member.

7. The secondary battery according to any one of claims 1 to 6, characterized in that: The secondary battery is a sodium ion battery, and the housing (200) is a copper shell, an iron shell, a stainless steel shell, an aluminum shell or an aluminum alloy shell.

8. A battery pack, characterized in that: The battery pack comprises a plurality of secondary batteries as described in any one of claims 1 to 7, and the plurality of secondary batteries are connected in series, in parallel or in a mixed manner.

9. An energy storage system, characterized in that: The energy storage system comprises a power converter and at least one battery pack as claimed in claim 8; The power converter is used to convert the voltage output by the battery pack into power and output it to a power grid or a load, and / or to convert the voltage output by an external power source into power and output it to the battery pack.

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