Battery and preparation method thereof, and electric device

Abstract

The application discloses a battery, a preparation method thereof and an electric device. The battery comprises a wound electrode assembly, the wound electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator arranged between the positive electrode sheet and the negative electrode sheet, the wound electrode assembly comprises a corner area, the corner area comprises a polymer layer, the polymer layer is located between the positive electrode sheet and the separator, and / or the polymer layer is located between the negative electrode sheet and the separator, the polymer layer comprises an electrically-conductive elastic polymer, the electronic conductivity of the electrically-conductive elastic polymer is 120 S / cm-600 S / cm, and the elongation at break of the electrically-conductive elastic polymer is 30%-120%. Thus, by forming the polymer layer meeting the above conditions in the corner area, the conductivity and flexibility of the positive active material layer and / or the negative active material layer in the corner area can be improved, the internal resistance of the battery and the risk of cracking of the corner can be reduced, and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to batteries and their manufacturing methods and electrical devices. Background Technology

[0002] With the rapid development of the new energy vehicle market, higher requirements have been placed on the safety of secondary batteries. Among them, wound electrode assemblies are widely used due to their advantages such as simple operation, fast production speed, and high production capacity.

[0003] In wound electrode assemblies, the concentrated current density at the corners of the cell can lead to reduced charge transfer efficiency in localized areas, increasing internal resistance and causing localized overheating, thus affecting battery cycle life. Furthermore, the corners of the electrode plates are stress concentration areas, making them prone to cracking. Summary of the Invention

[0004] This application provides a battery comprising a wound electrode assembly, the electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The wound electrode assembly includes a corner region comprising a polymer layer located between the positive electrode and the separator, and / or between the negative electrode and the separator. The polymer layer comprises a conductive elastic polymer having an electronic conductivity of 120 S / cm-600 S / cm and an elongation at break of 30%-120%. Thus, by forming a polymer layer satisfying the above conditions in the corner region, the conductivity and flexibility of the corner region of the positive and negative electrode can be improved, reducing the internal resistance of the battery and the risk of cracking of the positive and negative active material layers in the corner region, thereby improving the cycle performance of the battery.

[0005] According to some embodiments of this application, the thickness of the polymer layer is 20 μm-40 μm. This reduces the internal resistance of the battery and improves the flexibility of the active material layer at the corners.

[0006] According to some embodiments of this application, the conductive elastic polymer includes one or more of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid composite material, polyaniline, polythiophene, and conductive rubber. The aforementioned conductive elastic polymers can reduce the internal resistance of the battery while improving the toughness of the negative electrode active material layer at the corners, thus reducing the risk of cracking of the negative electrode active material layer due to stress concentration.

[0007] According to some embodiments of this application, the conductive elastic polymer comprises a poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid composite material, wherein the mass ratio of poly(3,4-ethylenedioxythiophene) to polystyrene sulfonic acid in the poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid composite material is 1:(1-3). This reduces the film resistance of the electrode and improves the flexibility of the active material layer in the electrode corner region.

[0008] According to some embodiments of this application, the polymer layer is located between the negative electrode sheet and the separator. This improves the conductivity and flexibility of the negative electrode active material layer in the corner region and reduces the risk of cracking in the corner region.

[0009] According to some embodiments of this application, the polymer layer is distributed continuously or intermittently in the corner region. This improves the conductivity and flexibility of the negative electrode corner region and reduces the risk of cracking at the corner of the negative electrode.

[0010] A second aspect of this application provides a method for preparing a battery, the method comprising: providing a positive electrode, a negative electrode, and a separator;

[0011] A polymer layer is formed between the positive electrode and the separator, and / or between the negative electrode and the separator. The positive electrode, the separator, and the negative electrode are wound together to form an electrode assembly. The electrode assembly includes a corner region, and the polymer layer is located in the corner region. The polymer layer comprises a conductive elastic polymer with an electronic conductivity of 120 S / cm-600 S / cm and an elongation at break of 30%-120% of the electronic conductivity. This improves the conductivity and flexibility of the positive and negative active material layers in the corner region, reduces the risk of cracking in the positive and / or negative active material layers in the corner region, and improves the cycle performance of the battery.

[0012] According to some embodiments of this application, a slurry containing the conductive elastic polymer is formed, and the method of forming the slurry in the corner area includes one or more of inkjet printing, spraying, screen printing, and 3D printing to form a uniform polymer layer on the surface of the active material layer.

[0013] According to some embodiments of this application, the polymer layer is formed on the surface of the negative electrode sheet, and the film resistance of the negative electrode sheet is 1.3mΩ-6mΩ, thereby improving the conductivity of the electrode sheet.

[0014] A third aspect of this application provides an electrical device, including a battery provided in the first aspect of this application or a battery prepared by the method provided in the second aspect of this application.

[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0017] Figure 1 This is a schematic diagram of the structure of the positive electrode sheet according to one embodiment of this application.

[0018] Figure 2 This is a schematic diagram of the negative electrode sheet according to one embodiment of this application.

[0019] Figure 3 This is a schematic diagram of a battery according to one embodiment of this application.

[0020] Figure 4 yes Figure 3 An exploded view of a battery according to one embodiment of this application is shown.

[0021] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application.

[0022] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0023] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown.

[0024] Figure 8 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Battery; 51 Housing; 52 Electrode assembly; 53 Cover plate; 521 Positive electrode sheet; 5210 Positive current collector; 5211 Positive active material layer; 522 Negative electrode sheet; 5220 Negative current collector; 5221 Negative active material layer; 523 Polymer layer; A Corner area; B Straight area. Detailed Implementation

[0027] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0030] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0033] The concentrated current density at the corner of the wound electrode assembly can lead to a decrease in local charge transfer efficiency, which in turn increases internal resistance and causes local overheating. In addition, the corner area is a stress concentration area, which is prone to cracking and reduces the cycle life of the battery.

[0034] By heating the corner and straight sections of the electrode in segments, the expansion of the straight and corner sections can be made more gradual, reducing the stress difference between the corner and straight sections and lowering the risk of cracking in the corner section of the electrode. However, the segmented heating process is complex and difficult to maintain. Adding more binder to the active material layer can also improve the toughness of the active material layer, but the increase in binder will reduce the conductivity of the electrode.

[0035] This application proposes a battery in which a polymer layer is formed between the positive electrode and the separator, and / or between the negative electrode and the separator. The conductive elastic polymer in the polymer layer has high conductivity and good elasticity and flexibility, which can improve the charge transport efficiency in the corner region and reduce the internal resistance of the battery. When the positive and / or negative active material layers in the corner region undergo volume changes, the polymer layer can effectively absorb and disperse the stress generated by the volume changes, reduce the stress in the active material layers in the corner region, reduce the risk of cracking in the positive and / or negative active material layers in the corner region, and thus improve the cycle performance of the battery.

[0036] The battery proposed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0037] A first aspect of this application provides a battery comprising a wound electrode assembly, the wound electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the wound electrode assembly including a corner region including a polymer layer located between the positive electrode and the separator, and / or the polymer layer located between the negative electrode and the separator, the polymer layer including a conductive elastic polymer having an electronic conductivity of 120 S / cm-600 S / cm and an elongation at break of 30%-120%.

[0038] As an example, the polymer layer is disposed between the positive electrode and the separator. The polymer layer may be disposed on the surface of the positive electrode or on the surface of the separator close to the positive electrode.

[0039] As an example, the polymer layer is disposed between the negative electrode and the separator. The polymer layer may be disposed on the surface of the negative electrode or on the surface of the separator near the negative electrode.

[0040] When the polymer layer is disposed on the surface of the positive electrode, reference Figure 1The positive electrode 521 includes a positive current collector 5210 and a positive active material layer 5211 disposed on at least one side of the positive current collector 5210. The positive electrode 521 includes a corner region A and a straight region B. The polymer layer 523 is disposed on the side of the positive active material layer 5211 away from the positive current collector 5210 and located in the corner region A.

[0041] When the polymer layer is disposed on the surface of the negative electrode sheet, reference Figure 2 The negative electrode 522 includes a negative electrode current collector 5220 and a negative electrode active material layer 5221 disposed on at least one side of the negative electrode current collector 5220. The negative electrode 522 includes a corner region A and a straight region B. The polymer layer 523 is disposed on the side of the negative electrode active material layer 5221 away from the negative electrode current collector 5220 and located in the corner region A.

[0042] By forming a polymer layer in the corner region, the conductivity of the corner region can be improved while reducing the stress in the corner region, thereby reducing the risk of cracking of the positive electrode active material layer and / or negative electrode active material layer in the corner region and improving the cycle performance of the battery.

[0043] If the electronic conductivity of the conductive elastic polymer is too small, the improvement on charge transport efficiency in the corner region will not be significant. If the electronic conductivity of the conductive elastic polymer is too large, the current density in the corner region will be too high, leading to heat accumulation and increasing the risk of short circuit in the corner region. Moreover, if the electronic conductivity of the conductive elastic polymer in the corner region is too large, the current will preferentially pass through the corner region, resulting in uneven current distribution on the positive electrode.

[0044] If the elongation at break of the conductive elastic polymer is too small, its effect on dissipating stress in the corner area will be insignificant; if the elongation at break of the conductive elastic polymer is too large, it will reduce the mechanical strength of the corner area.

[0045] In this application, when measuring the electronic conductivity and elongation at break of the conductive elastic polymer, the battery is disassembled to obtain the electrodes. The polymer layer between the positive electrode and the separator, and / or between the negative electrode and the separator, is adhered using polyimide tape. The peel strength of the tape is 1.15 N / mm-1.25 N / mm. Specifically, the polyimide tape is tightly adhered to the polymer layer, ensuring complete coverage. The tape is then slowly and evenly peeled off, and the polymer layer on the tape is scraped off. The thickness of the polymer layer is 20 μm-40 μm. Three test points are randomly selected, and the electronic conductivity is measured using a four-probe tester. The average value is taken as the electronic conductivity of the conductive elastic polymer. Similarly, three test points are randomly selected, and the elongation at break is measured using a universal testing machine. The average value is taken as the elongation at break of the conductive elastic polymer.

[0046] In this application, electronic conductivity refers to the density of electron current passing through a unit area under a unit electric field strength. As an example, the electronic conductivity of the conductive elastic polymer can be 120 S / cm, 200 S / cm, 300 S / cm, 400 S / cm, 500 S / cm, 600 S / cm, etc., or can be any range of the above values.

[0047] In this application, elongation at break refers to the ratio of the elongated length to the original length when the material breaks under tensile stress, usually expressed as a percentage. It reflects the ductility and toughness of the material under tensile force. As an example, the elongation at break of the conductive elastic polymer can be 30%, 50%, 70%, 90%, 105%, 120%, etc., or a range of any of the above values.

[0048] According to some embodiments of this application, the thickness of the polymer layer can be 20μm-40μm, for example, it can be 20μm, 25μm, 30μm, 35μm, 40μm, etc., or it can be any range of the above values. Therefore, by keeping the thickness of the polymer layer within the above range, the conductivity and flexibility of the corner area can be improved while reducing the space occupied by the polymer layer within the battery casing, thereby increasing the energy density of the battery.

[0049] According to some embodiments of this application, the conductive elastic polymer includes one or more of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid composite material (PEDOT:PSS composite material), polyaniline, polythiophene, and conductive rubber. The above-mentioned conductive elastic polymers can reduce the internal resistance of the battery while improving the toughness of the active material layer at corners, thus reducing the risk of cracking of the active material layer due to stress concentration.

[0050] According to some embodiments of this application, the conductive elastic polymer comprises a PEDOT:PSS composite material, wherein the mass ratio of PEDOT to PSS is 1:(1-3). For example, it can be 1:1, 1:2, 1:3, or any range of the above values. The composite material formed by PEDOT and PSS has high electronic conductivity, strong resistance to acid and alkali corrosion, good environmental stability, and good flexibility. When formed on the electrode, it can reduce the film resistance of the electrode, improve the flexibility of the active material layer in the corner area of ​​the electrode, reduce the risk of local overheating or cracking of the battery, and improve the cycle life of the battery. By forming PEDOT and PSS separately into polymer layers and then forming the polymer layer on the side of the active material layer away from the current collector, compared with directly adding PEDOT and PSS into the active material layer, the impact on the microstructure and conductive network of the active material layer can be reduced.

[0051] According to some embodiments of this application, the polymer layer can be continuously or discontinuously distributed. For example, when the polymer layer is formed between the negative electrode and the separator, the polymer layer can be continuously or discontinuously distributed on the surface of the negative electrode. The volume change of the negative electrode active material layer is relatively large. The polymer layer with the above structure can improve the conductivity and flexibility of the negative electrode active material layer, reduce the risk of cracking of the negative electrode active material layer, and improve the cycle performance of the battery.

[0052] A second aspect of this application provides a method for manufacturing a battery, the method comprising: providing a positive electrode, a negative electrode, and a separator; forming a polymer layer between the positive electrode and the separator, and / or between the negative electrode and the separator; winding the positive electrode, the separator, and the negative electrode to form an electrode assembly, the electrode assembly including a corner region, the polymer layer being located in the corner region, the polymer layer comprising a conductive elastic polymer having an electronic conductivity of 120 S / cm-600 S / cm and an elongation at break of 30%-120%. This improves the conductivity and flexibility of the positive and negative active material layers in the corner region, reduces the risk of cracking in the positive and / or negative active material layers in the corner region, and improves the cycle performance of the battery.

[0053] As an example, a positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0054] As an example, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0055] When forming a polymer layer on the surface of the positive or negative electrode, the conductive elastic polymer is mixed with a solvent. Heating and stirring can promote the dissolution of the conductive elastic polymer. The solution is then filtered to remove incompletely dissolved particles and impurities to form a polymer slurry. The polymer slurry is then formed in the corner area of ​​the slit positive or negative electrode and dried to form a polymer layer.

[0056] According to some embodiments of this application, the method of forming the polymer slurry in the corner area includes one or more of inkjet printing, spraying, screen printing, and 3D printing to form a uniform polymer layer on the surface of the active material layer.

[0057] According to some embodiments of this application, a polymer layer can be formed in the corner area by inkjet printing technology. The inkjet printing technology can achieve precise control of the inkjet position, inkjet volume and inkjet thickness in the corner area.

[0058] In this application, the viscosity of the slurry can be tested using a rotational viscometer. Specifically, a suitable rotor and rotation speed are selected, and the rotor speed is adjusted to accommodate different shear rates. After the slurry is stirred evenly, it is poured into the sample chamber of the viscometer, and then the rotor is immersed in the slurry to measure and record the viscosity reading.

[0059] According to some embodiments of this application, the printing speed during inkjet printing can be 10mm / s-30mm / s, the nozzle diameter can be 20μm-30μm, the inkjet frequency can be 5kHz-20kHz, and the printing temperature can be room temperature.

[0060] According to some embodiments of this application, the polymer layer is formed on the surface of the negative electrode sheet, and the film resistance of the negative electrode sheet is 1.3mΩ-6mΩ, for example, it can be 1.3mΩ, 2mΩ, 3mΩ, 4mΩ, 5mΩ, 6mΩ, etc., or it can be any range of values, so as to improve the conductivity of the electrode sheet.

[0061] In this application, the film resistance of the negative electrode can be tested using the four-probe method.

[0062] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0063] [Positive electrode plate]

[0064] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes the positive active material of the first aspect of this application.

[0065] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0066] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0067] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 )), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0068] In some implementations, such as when the battery is a sodium-ion battery, the positive electrode active material may, as an example, include, but is not limited to, at least one of layered transition metal oxides, polyanionic compounds, and Prussian blue analogues.

[0069] Examples of the aforementioned layered transition metal oxides include:

[0070] Na 1-x Cu h Fe k Mn l M 1 m O 2-y M 1 It is one or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0071] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 It is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0072] Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≤1,0<b<0.2,0<c<0.3,0.67<d+e<0.8,b+c+d+e=1。

[0073] Examples of the aforementioned polyanionic compounds include:

[0074] A 1 f M 3 g (PO4)i O j X 1 3-j , wherein A 1 is one or more selected from H, Li, Na, K and NH4, M 3 is one or more selected from Ti, Cr, Mn, Fe, Co, Ni, V, Cu and Zn, X 1 is one or more selected from F, Cl and Br, 0<f≤4, 0<g≤2, 1≤i≤3, 0≤j≤2;

[0075] Na n M 4 PO4X 2 , wherein M 4 is one or more selected from Mn, Fe, Co, Ni, Cu and Zn, X 2 is one or more selected from F, Cl and Br, 0<n≤2;

[0076] Na p M 5 q (SO4)3, wherein M 5 is one or more selected from Mn, Fe, Co, Ni, Cu and Zn, 0<p≤2, 0<q≤2;

[0077] Na s Mn t Fe 3-t (PO4)2(P2O7), wherein 0<s≤4, 0≤t≤3, for example, t is 0, 1, 1.5, 2 or 3.

[0078] As examples of the above Prussian blue analogs, there may be enumerated:

[0079] A u M 6 v [M 7 (CN)6] w ·xH2O, wherein A is H + , NH4 + , one or more selected from alkali metal cations and alkaline earth metal cations, M 6 and M 7 are each independently one or more selected from transition metal cations, 0<u≤2, 0<v≤1, 0<w≤1, 0<x<6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ and Ra 2+ One or more of them, M 6 and M 7 Each is an independent cation of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, and W.

[0080] The modified compounds for the above materials can be used to modify the materials by doping and / or by surface coating.

[0081] In some embodiments, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

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

[0083] [Negative electrode plate]

[0084] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0085] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0086] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0087] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and titanates. 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. When the battery is a lithium-ion battery, lithium titanate is used; when the battery is a sodium-ion battery, sodium titanate is used. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0088] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0089] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0090] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0091] [Electrolytes]

[0092] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0093] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0094] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0095] In some embodiments of this application, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0096] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0097] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0098] [Isolation membrane]

[0099] In some embodiments, the battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0100] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0101] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0102] In some embodiments, the battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0103] In some implementations, the battery's outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The battery's outer packaging can also be a soft pack, such as a pouch. The soft pack can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0104] This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 The battery 5 is a square structure, which serves as an example.

[0105] In some implementations, refer to Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator are formed into an electrode assembly 52 by a winding process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0106] In some implementations, the batteries can be assembled into battery modules, and the number of batteries contained in a battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0107] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In battery module 4, multiple batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple batteries 5 can be fixed in place using fasteners.

[0108] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of batteries 5 are received.

[0109] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0110] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0111] A third aspect of this application provides an electrical device, including a battery provided in the first aspect of this application or a battery prepared by the method provided in the second aspect of this application.

[0112] The electrical equipment may include, but is 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, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0113] As the electrical equipment, batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0114] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density batteries, a battery pack or battery module can be used.

[0115] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can be powered by a battery.

[0116] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0117] Example 1

[0118] 1. Preparation of positive electrode sheet

[0119] The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O2), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) solvent was added and stirred until the system was homogeneous to obtain a positive electrode slurry (solid content of 60%). The positive electrode slurry was uniformly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then rolled and cut to obtain the positive electrode sheet.

[0120] 2. Preparation of negative electrode sheet

[0121] Artificial graphite, styrene-butadiene rubber (SBR) binder, carbon black conductive agent, and sodium carboxymethyl cellulose (CMC-Na) dispersant were added to deionized water in a weight ratio of 95:1.5:1.5:2 and stirred until the system was homogeneous to obtain a negative electrode slurry (solid content of 56%). The negative electrode slurry was uniformly coated on one surface of the negative electrode current collector copper foil to form a negative electrode active material layer and dried at 120°C. The negative electrode slurry was then uniformly coated on the other surface of the negative electrode current collector copper foil to form a negative electrode active material layer and dried at 120°C. After cold pressing and slitting, the initial negative electrode sheet was obtained.

[0122] A conductive elastic polymer PEDOT:PSS ratio of 1:1 (by mass) was added to deionized water and stirred at 60°C until the elastic material was completely dissolved. The mixture was then filtered to remove undissolved conductive elastic polymer and other impurities, resulting in a 5wt% aqueous elastic slurry. The conductive elastic polymer had an electronic conductivity of 600 S / cm and an elongation at break of 30%. The aqueous conductive elastic polymer was printed onto the bending area of ​​the initial negative electrode using electrohydraulic inkjet printing, extending 2cm to each side from the bending area. The slurry was then cured at 120°C for 1 minute to form a polymer layer with a thickness of 30μm. The spray pressure was 2MPa, the printing speed was 20mm / s, the nozzle diameter was 20μm, and the inkjet frequency was 10kHz, resulting in the negative electrode.

[0123] 3. Separating membrane

[0124] Polypropylene is used as the separator membrane.

[0125] 4. Electrolyte

[0126] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the mixed solvent to obtain an electrolyte with a concentration of 1 mol / L of LiPF6.

[0127] 5. Battery fabrication

[0128] Following the sequence of "separator-positive electrode-separator-negative electrode," the positive electrode, negative electrode, and two separators are fixed at one end to the discharge roller, and the other ends are stacked together and fixed to the winding shaft. A motor is used to rotate the winding shaft, winding the positive electrode, negative electrode, and two separators to obtain a wound bare cell. Tabs are welded to the bare cell, and the cell is then placed in an aluminum casing and baked at 100°C to remove water. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. The non-charged battery then undergoes a series of processes including settling (45°C / 48h), hot and cold pressing, formation (0.02C current formation for 10h), shaping, and capacity testing to obtain a single battery cell.

[0129] Comparative Example 3

[0130] The battery is prepared using the same method as in Example 1, except that:

[0131] Graphite, conductive carbon, and CMC-Na were dry-mixed for 15 minutes, water was added and stirred for 2 hours at 1800 rpm, conductive elastic polymer PEDOT:PSS = 1:2 (mass ratio) was added, and stirred for 15 minutes at 1000 rpm. SBR was added and stirred for 30 minutes at 1000 rpm to obtain the negative electrode slurry. The mass ratio of artificial graphite, SBR, conductive carbon, conductive elastic polymer, and CMC-Na in the negative electrode slurry was 93:2:1.5:2:1.5.

[0132] In this application, when different conductive elastic polymers are used to form polymer layers, the elongation at break is tested in accordance with GB / T1701-2001 "Determination of tensile strength and elongation at break of rigid rubber".

[0133] When determining electronic conductivity, a conductive elastic polymer is placed on an insulating substrate. The sample size is 20mm × 20mm, and the thickness is greater than 4 times the probe spacing. The test is performed using a four-probe tester.

[0134] The preparation methods of the batteries in Examples 2-10 and Comparative Examples 1-3 are the same as those in Example 1, with the differences detailed in Table 1.

[0135] Table 1

[0136]

[0137] Performance testing

[0138] 1. Resistance test

[0139] The resistance of the negative electrode provided in the examples and comparative examples was tested using the four-probe method.

[0140] 2. Flexibility test

[0141] The negative electrode sheets in the examples and comparative examples were folded three times respectively, and the powder shedding of the electrode sheets was observed.

[0142] 3. Crack resistance test

[0143] The negative electrode sheets from the examples and comparative examples were placed in an oven at 80°C for baking, and it was observed whether cracks occurred on the surface of the electrode sheets when the moisture content was below 10 ppm.

[0144] 4. Cyclic performance test

[0145] (1) At 35±2℃, charge the battery at a constant current of 0.33C to 4.35V, then charge it at a constant voltage of 4.35V to a current of 0.05C, and let it stand for 10 minutes; discharge it at a constant current of 0.33C to 2.8V and record the discharge capacity C0. (2) Repeat step (1) 600 times and record the discharge capacity C of the battery after 600 cycles. 600 Calculate the battery capacity retention rate P 600 =C 600 / C0×100%.

[0146] The test results of the negative electrode sheet and battery performance in Examples 1-10 and Comparative Examples 1-3 are shown in Table 2.

[0147] Table 2

[0148]

[0149] As can be seen from the comparison between Examples 1-10 and Comparative Examples 1-3, the battery proposed in this application can reduce the probability of powder shedding after electrode bending, reduce the risk of cracking after electrode baking, and improve the cycle performance of the battery. This application demonstrates that by forming a polymer layer on the side of the active material layer away from the current collector in the corner region, and by defining the electronic conductivity and elongation at break of the conductive polymer forming the polymer layer, the charge transport efficiency in the corner region can be improved, and the internal resistance of the battery can be reduced. When the battery volume changes, the polymer layer can effectively absorb and disperse the stress generated by the volume change, reducing the stress transmitted to the active material layer, reducing the stress in the active material layer in the corner region, reducing the risk of cracking in the active material layer in the corner region, and thus improving the cycle performance of the battery.

[0150] As can be seen from Examples 1-5, by adjusting the ratio of PEDOT and PSS, conductive elastic polymers with different electronic conductivity and elongation at break can be formed, thereby adjusting the ability of the polymer layer to absorb and disperse stress, and obtaining a battery with excellent cycle performance, less powder shedding, and less cracking.

[0151] As can be seen from Examples 6 and 7, different types of conductive elastic polymers can all reduce electrode powder shedding, reduce electrode cracking, and improve battery cycle performance.

[0152] As can be seen from Examples 8-10, by adjusting the inkjet printing speed, polymer layers of different thicknesses can be formed on the side of the active material layer away from the current collector, thereby reducing electrode powder shedding, reducing electrode cracking, and improving battery cycle performance while taking into account the energy density of the battery.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery, characterized in that, The invention includes a wound electrode assembly comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The wound electrode assembly includes a corner region comprising a polymer layer located between the positive electrode and the separator, and / or located between the negative electrode and the separator. The polymer layer comprises a conductive elastic polymer having an electronic conductivity of 120 S / cm-600 S / cm and an elongation at break of 30%-120%.

2. The battery according to claim 1, characterized in that, The thickness of the polymer layer is 20μm-40μm.

3. The battery according to claim 1 or 2, characterized in that, The conductive elastic polymer includes one or more of poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid composite material, polyaniline, polythiophene, and conductive rubber.

4. The battery according to any one of claims 1-3, characterized in that, The conductive elastic polymer includes a poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid composite material, wherein the mass ratio of poly(3,4-ethylenedioxythiophene) to polystyrene sulfonic acid in the poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid composite material is 1:(1-3).

5. The battery according to any one of claims 1-4, characterized in that, The polymer layer is located between the negative electrode and the separator.

6. The battery according to any one of claims 1-5, characterized in that, The polymer layer is distributed continuously or intermittently in the corner area.

7. A method for preparing a battery, characterized in that, include: We provide positive electrode plates, negative electrode plates, and separators; A polymer layer is formed between the positive electrode and the separator, and / or between the negative electrode and the separator. The positive electrode, the separator, and the negative electrode are wound together to form an electrode assembly. The electrode assembly includes a corner region. The polymer layer is located in the corner region. The polymer layer includes a conductive elastic polymer with an electronic conductivity of 120 S / cm-600 S / cm and an elongation at break of 30%-120%.

8. The method according to claim 7, characterized in that, The method of forming a slurry containing the conductive elastic polymer and forming the slurry in the corner area includes one or more of inkjet printing, spraying, screen printing, and 3D printing.

9. The method according to claim 7 or 8, characterized in that, The polymer layer is formed on the surface of the negative electrode sheet, and the film resistance of the negative electrode sheet is 1.3mΩ-6mΩ.

10. An electrical appliance, characterized in that, Includes the battery according to any one of claims 1-6 or the battery prepared by the method according to any one of claims 7-9.

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