Pole piece, battery and electric equipment

Abstract

The utility model discloses a pole piece, a battery and electric equipment, relates to the technical field of lithium batteries, and aims to solve the problems that the migration speed of lithium ions in the pole piece is low, and lithium is easy to separate out on the surface of a negative electrode when the lithium ions are quickly charged. The pole piece comprises a current collector and a first active material layer, at least one side of the current collector is provided with the first active material layer, the first active material layer comprises a first piezoelectric material, and the polarization direction of the first active material layer is consistent with the thickness direction of the first active material layer. When lithium ions penetrate through the first active material layer, the lithium ions and the potential difference are in the same direction, so that the migration speed of the lithium ions can be increased, and the migration speed of the lithium ions between the positive plate and the negative plate is increased. And the charging speed and the discharging speed are further improved. When the pole piece is applied to a negative pole piece and is in a charging state, uniform embedding of lithium ions is facilitated, and surface lithium precipitation during fast charging is inhibited.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium batteries, in particular to a pole piece, a battery and an electrical equipment. Background Art

[0002] A battery is an electrical energy storage and release device composed of a positive electrode plate, a negative electrode plate, a separator and an electrolyte. During charging, ions are removed from the active material of the positive electrode plate, combine with the electrolyte on its surface, pass through the pores of the separator, reach the surface of the negative active material, and are embedded in the negative active material after removing the electrolyte. The discharging process is opposite to the charging process.

[0003] The charging performance of the battery is determined by the speed of ion migration back and forth between the positive and negative electrode plates. In the prior art, there is a problem that the migration speed of ions between the positive and negative electrode plates is slow, resulting in slow charging and discharging speeds of the battery. Summary of the Utility Model

[0004] Embodiments of the utility model provide a pole piece, a battery and an electrical equipment, which are used to solve the problem of slow migration speed of ions between the positive and negative electrode plates.

[0005] To achieve the above object, the embodiments of the utility model adopt the following technical solutions:

[0006] In a first aspect, a pole piece is provided, which includes a current collector and a first active material layer. The first active material layer is provided on at least one side of the current collector. The first active material layer includes a first piezoelectric material, and the polarization direction of the first active material layer is consistent with the thickness direction of the first active material layer.

[0007] The first active material layer is in a polarized state. The polarization direction of the first active material layer refers to the moving direction of negative charges inside the active material layer. The moving of negative charges inside the active material layer forms a potential difference. When lithium ions pass through the first active material layer, the lithium ions are in the same direction as the potential difference, which can accelerate the migration speed of lithium ions, thereby improving the migration speed of lithium ions between the positive and negative electrode plates. Furthermore, the charging speed and discharging speed are improved.

[0008] In a possible implementation manner, the polarization direction of the first active material layer points from the surface of the first active material layer facing the current collector to the surface of the first active material layer facing away from the current collector.

[0009] In a possible implementation manner, the polarization direction of the first active material layer points from the surface of the first active material layer facing away from the current collector to the surface of the first active material layer facing the current collector.

[0010] In a possible implementation manner, the pole piece further includes a second active material layer, and the second active material layer is disposed between the first active material layer and the current collector.

[0011] In a possible implementation, the second active material layer does not include a piezoelectric material.

[0012] In a possible implementation, the second active material layer includes a second piezoelectric material, and the polarization direction of the second active material layer is the same as that of the first active material layer.

[0013] In a possible implementation, the thickness of the first active material layer accounts for 5%-50% of the sum of the thicknesses of the first active material layer and the second active material layer.

[0014] In a possible implementation, the thickness of the first active material layer accounts for 5%-20% of the sum of the thicknesses of the first active material layer and the second active material layer.

[0015] In a possible implementation, the thickness of the first active material layer or the second active material layer is greater than or equal to 10 μm and less than or equal to 1000 μm.

[0016] In a possible implementation, the thickness of the first active material layer or the second active material layer is greater than or equal to 50 μm and less than or equal to 250 μm.

[0017] In a possible implementation, a conductive layer is further included, and the conductive layer is located between the current collector and the first active material layer.

[0018] In a possible implementation, the electrode sheet is a positive electrode sheet or a negative electrode sheet.

[0019] In a second aspect, a battery is provided, and the battery includes the electrode sheet according to any one of the implementations in the first aspect above.

[0020] In a third aspect, an electrical device is provided, including the battery according to any one of the implementations mentioned in the second aspect above.

[0021] It should be noted that for the technical effects brought by any one of the implementations in the second aspect and the third aspect, reference can be made to the technical effects brought by the corresponding implementations in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 One of the schematic structural diagrams of a battery provided by an embodiment of the present application;

[0023] Figure 2 Another schematic structural diagram of a battery provided by an embodiment of the present application;

[0024] Figure 3 Still another schematic structural diagram of a battery provided by an embodiment of the present application;

[0025] Figure 4The fourth structural schematic diagram of a battery provided by an embodiment of the present application;

[0026] Figure 5 The fifth structural schematic diagram of a battery provided by an embodiment of the present application.

[0027] Reference numerals:

[0028] 10 - Battery;

[0029] 11 - Positive electrode sheet; 111 - Current collector of the positive electrode; 112 - First active material layer of the positive electrode; 113 - Second active material layer of the positive electrode;

[0030] 12 - Negative electrode sheet; 121 - Current collector of the negative electrode; 122 - First active material layer of the negative electrode; 123 - Second active material layer of the negative electrode;

[0031] 13 - Separator;

[0032] 1 - Current collector; 2 - First active material layer; 3 - Second active material layer; 4 - Conductive layer. Detailed implementation manners

[0033] The embodiments of the present utility model will be described in detail below with reference to the accompanying drawings.

[0034] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present utility model.

[0035] The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise specified, the meaning of "a plurality" is two or more.

[0036] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances. In addition, when describing pipelines or channels, the terms "connected" and "coupled" used in this application have the meaning of conducting. The specific meaning needs to be understood in combination with the context.

[0037] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0038] As used herein, "about", "substantially", or "approximately" includes the stated value and the average value within an acceptable deviation range of the specific value, where the acceptable deviation range is determined by those of ordinary skill in the art considering the measurement being discussed and the errors associated with the measurement of the specific quantity (i.e., the limitations of the measurement system).

[0039] The present application provides a pole piece, a battery, and an electrical device. For the convenience of the description of the following embodiments, before introducing the embodiments of the present application, some professional terms to be mentioned in the embodiments of the present application are first introduced. Specifically:

[0040] Battery: The battery mentioned in the present application is a secondary battery. A secondary battery is also called a rechargeable battery or a storage battery, which refers to a battery that can be activated by charging after discharging so as to be used continuously.

[0041] Positive electrode: It refers to the end with a higher potential (electromotive force) in a power source. In a primary battery, the device is a power source, and the electrode with a higher electrode potential where the current flows out is the positive electrode. The positive electrode plays a reduction role, that is, ions or molecules gain electrons; in an electrolytic cell, the device is an electrical appliance. Taking the connected power source as the standard, the electrode connected to the positive electrode of the power source is the positive electrode. At this time, the positive electrode plays an oxidation role, that is, ions or molecules lose electrons.

[0042] Negative electrode: It refers to the end with a lower potential (electromotive force) in a power source. In a primary battery, the electrode with a lower potential where the current flows in is the negative electrode, and the negative electrode is the electrode where oxidation occurs; in an electrolytic cell, the electrode connected to the negative electrode of the power source is the negative electrode. At this time, the negative electrode gains electrons and undergoes a reduction reaction. From a physical perspective, the negative electrode is the pole where electrons flow out in a circuit.

[0043] Electrolyte: It refers to the medium used to provide ion exchange between the positive and negative electrodes of a battery.

[0044] Separator: It refers to a thin film that separates the positive and negative electrodes of a battery during the charge and discharge reaction process to prevent the two electrodes from contacting and short-circuiting. At the same time, the separator also allows electrolyte ions to pass through.

[0045] Piezoelectric material: Piezoelectric materials have the piezoelectric effect. When this medium is deformed under the action of an external force in a certain direction, the positive and negative charges inside it shift, polarization occurs, and an electric field is generated in the direction of the deformation; when this medium is under the action of an external strong electric field, the positive and negative charges shift, and the material can undergo macroscopic deformation.

[0046] In this embodiment, the battery is an ion electrode battery, and the specific ion is a lithium ion, so it is hereinafter referred to as a lithium battery.

[0047] The core components of a lithium battery mainly include a positive electrode, a negative electrode, an electrolyte, and a separator. The separator is arranged between the positive electrode and the negative electrode. When a lithium battery is charged, lithium ions (Li + ) are removed from the active material of the positive electrode, pass through the electrolyte, and pass through the separator, and combine with electrons (e-) on the surface of the negative electrode to form lithium (Li). The reaction chemical formula at the negative electrode is: Li + +e-→Li. When a lithium battery is discharged, lithium (Li) at the negative electrode loses an electron (e-) to form a lithium ion (Li + ), and the reaction chemical formula is: Li→Li + +e-. The lithium ion (Li + ) passes through the electrolyte and passes through the separator, and inserts into the active material of the positive electrode.

[0048] When a lithium battery is discharged, the migration direction of lithium ions (Li + ) is opposite to that during charging.

[0049] In the above process, the migration speed of lithium ions (Li + ) back and forth between the positive and negative electrodes affects the charge and discharge speed of the lithium battery. In related technologies, the migration speed of lithium ions (Li + ) between the positive and negative electrodes is slow, resulting in a slow charge and discharge speed of the battery.

[0050] To solve the above problems, as Figure 1 shown, Figure 1One of the structural schematic diagrams of a battery provided by an embodiment of the present application.

[0051] The electrode sheet provided by the present application includes a current collector 1 and a first active material layer 2. The first active material layer 2 is connected to the current collector 1. The first active material layer 2 includes a first piezoelectric material, and the polarization direction of the first active material layer is consistent with the thickness direction of the first active material layer 2.

[0052] The first piezoelectric material is in a polarized state. The polarization direction of the first active material layer refers to the moving direction of negative charges inside the first active material layer. The movement of negative charges inside the first active material layer forms a potential difference. When lithium ions pass through the first active material layer, the movement direction of lithium ions is the same as the direction of the potential difference, which can accelerate the migration speed of lithium ions, thereby improving the migration speed of lithium ions between the positive and negative electrode sheets 12. Furthermore, the charging speed and the discharging speed are improved.

[0053] The embodiments of the present application will be introduced in detail below with reference to the drawings. Before introducing the embodiments of the present application in detail, the application scenarios of the embodiments of the present application will be introduced first.

[0054] Hereinafter, the current collector 111 of the positive electrode and the current collector 121 of the negative electrode will be used for distinction, and the first active material layer 112 of the positive electrode and the first active material layer 122 of the negative electrode will be used for distinction.

[0055] The present application provides an electrical device, which includes a battery 10 and an electronic device. The battery 10 is electrically connected to the electronic device. The electrical device includes, but is not limited to, a pure electric vehicle, a hybrid electric vehicle, a laptop computer, a mobile phone, a tablet, an automobile, a motorcycle, an airplane, a toy, a game console, and a backup power supply. The present application takes the electrical device as a vehicle for exemplary illustration.

[0056] Under normal charging conditions, a faster charging speed can save time for users, improve work efficiency, or increase the total charging amount within the same time, thereby increasing the usage duration of the electrical device. Improving the migration speed of lithium ions from the positive electrode to the negative electrode can increase the charging speed. When the battery 10 discharges, the ambient temperature of the battery 10 is low, resulting in high viscosity of the electrolyte and slow transmission of lithium ions between the positive and negative electrodes. It is necessary to increase the transmission speed of lithium ions from the negative electrode to the positive electrode to ensure the normal discharging speed of the battery 10.

[0057] Continue to refer to Figure 1 , the present application provides a battery 10, which includes a positive electrode sheet 11, a negative electrode sheet 12, and a separator 13. The separator 13 is located between the positive electrode sheet 11 and the negative electrode sheet 12. The present application provides an electrode sheet, which can be the positive electrode sheet 11 of the battery 10 or the negative electrode sheet 12 of the battery.

[0058] The electrode includes a current collector 1 and a first active material layer 2. The first active material layer 2 is in a polarized state, and the polarization direction of the first active material layer is from the surface of the first active material layer 2 facing the current collector 1 to the surface of the first active material layer 2 facing away from the current collector 1.

[0059] When the electrode provided in this application is used as the positive electrode 11.

[0060] During the charging process, lithium ions in the positive electrode escape from the active material of the positive electrode and migrate to the negative electrode. Figure 1 On the left side of the separator 13 is the positive electrode, and on the right side of the separator 13 is the negative electrode. The polarization direction of the first active material layer in the first active material layer 2 at the positive electrode is from the positive electrode to the negative electrode. At this time, the movement direction of lithium ions is the same as the polarization direction of the piezoelectric material. After the first active material layer 2 is polarized, a potential difference is generated, and the potential difference has an accelerating effect on the positively charged lithium ions, thereby accelerating the migration speed of lithium ions. Furthermore, the charging speed is increased.

[0061] Continue to refer to Figure 1 , during the fast charging process, there is a possible application scenario, that is, lithium metal plating is likely to occur on the side of the negative electrode close to the positive electrode. Lithium metal plating is a phenomenon in which lithium ions aggregate in one place, a part of the lithium ions are embedded in the active material, and the remaining lithium ions accumulate at the saturated active material. The lithium ions cannot be embedded inside the active material and are deposited on the surface of the negative electrode to form metallic lithium. The lithium ions are precipitated into metallic lithium, and the number of lithium ions that can migrate inside the battery 10 decreases, resulting in a reduction in the total capacity of the battery 10, weakening the energy storage capacity of the battery 10, and reducing the service life and performance of the battery 10.

[0062] When the electrode provided in this application is used as the negative electrode 12, the polarization direction of the first active material layer 122 of the negative electrode is from the surface of the first active material layer 122 of the negative electrode facing the current collector 121 of the negative electrode to the surface of the first active material layer 122 of the negative electrode facing away from the current collector 121 of the negative electrode, that is, from the negative electrode of the battery 10 to the positive electrode. At this time, the lithium metal plating phenomenon during fast charging can be alleviated.

[0063] Specifically: the potential on the side of the first active material layer 122 of the negative electrode close to the positive electrode is lower than the potential on the side close to the negative electrode, that is Figure 1 as shown by the arrow in the first active material layer 122 of the negative electrode in, the side of the first active material layer 122 of the negative electrode close to the positive electrode is negatively charged. When the positively charged lithium ions approach the surface of the negatively charged first active material layer 122, it is beneficial for the lithium ions to obtain negative charges on the surface and thus quickly embed inside the active material. For the locally saturated active material, it will undergo large deformation and generate a piezoelectric effect, increasing the potential here and inducing subsequent lithium ions to preferentially deposit in the low-potential area, that is, the unsaturated area, preventing the excessive deposition of lithium ions and the occurrence of lithium metal plating phenomenon, and making the lithium ions evenly embed into the negative electrode active material.

[0064] Continue to refer to Figure 1 During the negative electrode discharge process, lithium ions in the negative electrode escape from the active material of the negative electrode and migrate towards the positive electrode. The polarization direction of the first active material layer 122 of the negative electrode also points from the negative electrode to the positive electrode. At this time, the movement direction of the lithium ions is the same as the polarization direction of the piezoelectric material. After the first active material layer 122 of the negative electrode is polarized, a potential difference is generated. The potential difference has an accelerating effect on the positively charged lithium ions, thereby accelerating the migration speed of the lithium ions and facilitating the lithium ions to break away from the first active material layer 122 of the negative electrode. Furthermore, the discharge speed is increased.

[0065] In a possible implementation manner, the positive electrode sheet 11 provided in the present application is a sheet with a first active material layer 2 including a first piezoelectric material, and the negative electrode is a sheet with a first active material layer 2 including a first piezoelectric material.

[0066] In a possible implementation manner, the positive electrode sheet 11 provided in the present application is a sheet with a first active material layer 2 including a first piezoelectric material, and the negative electrode is a sheet with a first active material layer 2 not including a first piezoelectric material.

[0067] In a possible implementation manner, the negative electrode sheet 11 provided in the present application is a sheet with a first active material layer 2 including a first piezoelectric material, and the positive electrode is a sheet with a first active material layer 2 not including a first piezoelectric material.

[0068] The first active material layer 2 does not include a first piezoelectric material. When lithium ions pass through the first active material layer 2, there is no hindrance from the piezoelectric material to the lithium ions, which can increase the speed of lithium ions passing through the first active material layer 2.

[0069] It should be noted that the electrode sheets in the present application need to be pre-polarized by an external electric field. The field strength of the applied electric field is selected according to the strength Ec of the room temperature coercive field of the piezoelectric material. The field strength of the applied electric field is 0.1 times to 10 times the strength Ec of the room temperature coercive field. When it is lower than 0.1 times the room temperature coercive field, the piezoelectric material cannot be polarized by the external electric field. When it is higher than 10 times the strength of the room temperature coercive field, the piezoelectric material may be broken down and lose its function.

[0070] The first active material layer 112 of the positive electrode includes an active material and a piezoelectric material.

[0071] Specifically, the active material in the first active material layer 112 of the positive electrode includes at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate.

[0072] The piezoelectric material is at least one of a piezoelectric polymer, a piezoelectric ceramic, and an inorganic piezoelectric material.

[0073] Specifically, the piezoelectric polymer includes one of polyvinylidene fluoride (PVDF), vinylidene fluoride / trifluoroethylene copolymer, and vinylidene fluoride / tetrafluoroethylene copolymer. The piezoelectric ceramic includes one of barium titanate (BaTiO3), lead titanate (PbTiO3), lithium niobate (LiNbO3), and lithium tantalate (LiNbO3). The inorganic piezoelectric material includes at least one of metal oxides, nitrides, carbides, or intermetallic compounds.

[0074] Among them, the metal oxides include at least one of zinc oxide, bismuth oxide, cobalt oxide, lead oxide, nickel oxide, chromium oxide, or antimony oxide; the nitrides include at least one of aluminum nitride (AlN), aluminum gallium nitride (AlGaN), indium aluminum nitride (InAlN), gallium nitride (GaN), indium gallium nitride (InGaN), or indium nitride (InN); the carbides include silicon carbide (SiC); and the intermetallic compounds include at least one of titanium aluminide-based (Ti3Al) or titanium aluminide-based (TiAl) intermetallic compounds.

[0075] In a possible implementation, the piezoelectric material can be one of single crystals or polycrystals.

[0076] In a possible implementation, the first active material layer 112 of the positive electrode further includes a conductive agent. In this way, the conductive agent is beneficial to the connection between the active material and the piezoelectric material, and thus, the fluidity of lithium ions passing through the first active material layer 112 of the positive electrode can be improved.

[0077] The above-mentioned conductive agent includes at least one of carbon black (CB), carbon nanotubes (CNT), acetylene black (AB), graphene, and whisker carbon nanotubes (VGCF).

[0078] In a possible implementation, the first active material layer 2 of the positive electrode further includes an adhesive. In this way, the adhesive can tightly bond the piezoelectric material and the first active material.

[0079] The above-mentioned adhesive includes at least one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol, polyimide, polyamideimide, carboxymethyl cellulose salts (CMC-Li or Na or K), polyacrylates (PAA-Li or Na or K), polyvinyl butyral (PVB), and aqueous acrylic resins.

[0080] The first active material layer 122 of the negative electrode includes an active material and a piezoelectric material.

[0081] The active material in the first active material layer 122 of the negative electrode includes at least one of a carbon-based material and a silicon-based material. The carbon-based material includes at least one of graphite, soft carbon, and hard carbon. The silicon-based material includes at least one of silicon, silicon carbide, silicon oxide, and silicon monoxide.

[0082] For the piezoelectric material in the negative electrode tab, reference can be made to the piezoelectric material in the positive electrode tab, which will not be elaborated here.

[0083] In a possible implementation, the first active material layer 122 of the negative electrode further includes a conductive agent and a binder. The settings of the binder and the conductive agent can refer to the settings of the conductive agent and the binder in the first active material layer 2 of the positive electrode tab.

[0084] This application does not specifically limit the current collector 1. The current collector 1 can be aluminum foil, aluminum alloy foil, nickel foil, copper foil, carbon-coated current collector, or other composite current collectors, etc.

[0085] In a possible implementation, the thickness of the current collector 1 is greater than or equal to 2 μm and less than or equal to 25 μm. Specifically, the thickness of the positive current collector 1 can be 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm. The current collector 1 here includes the positive current collector 111 and the negative current collector 121.

[0086] The separator 13 in this application is not particularly limited as long as it can achieve the purpose of this application. For example, at least one of polyolefin (PO) - based separators 13 mainly composed of polyethylene (PE) and polypropylene (PP), polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide films (PA), or composite films, etc.

[0087] The battery 10 provided by this application further includes an electrolyte. The electrolyte includes at least one of a gel electrolyte, a solid electrolyte, and an electrolytic solution. The electrolytic solution includes a lithium salt and a non-aqueous solvent. Among them, the lithium salt can include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiCH3SO3, LiCF3SO3, LiSiF6, LiBOB, LiTFSI, or lithium difluoroborate. For example, the lithium salt can be selected as LiPF6. Among them, the non-aqueous solvent can be at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents.

[0088] The above carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound, or a combination thereof.

[0089] The above-mentioned chain carbonate compounds may be dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof.

[0090] The above-mentioned cyclic carbonate compounds may be ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene ethylene carbonate (VEC), and combinations thereof.

[0091] The above-mentioned fluorinated carbonate compounds may be fluoroethylene carbonate (FEC), (2-difluoroethylene carbonate), (1-difluoroethylene carbonate), (1,1,2-trifluoroethylene carbonate), (1,1,2,2-tetrafluoroethylene carbonate), (1,1,2,2-tetrafluoroethylene carbonate), 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, (1,2-difluoro-1-methylethylene carbonate), (1,1,2-trifluoro-2-methylethylene carbonate), trifluoromethyl ethylene carbonate, and combinations thereof.

[0092] The above-mentioned carboxylic acid ester compounds may be methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and combinations thereof.

[0093] The above-mentioned ether compounds may be dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, (1,2-dimethoxyethane), (1,2-diethoxyethane), ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0094] The above-mentioned other organic solvents may be at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters.

[0095] The provided battery 10 further includes a structural member. There is no particular limitation on the structural member of the present application as long as it can achieve the purpose of the present application. For example, an aluminum plastic film, an aluminum shell, a steel shell, a tab, a terminal, a current collector plate, etc., which are mainly used to realize the functions of the lithium-ion battery 10.

[0096] The preparation process of the lithium-ion battery 10 of the present application is well-known to those skilled in the art, and there is no special limitation in the present application. For example, it can be manufactured through the following process: The positive electrode sheet 11 and the negative electrode sheet 12 are separated by a separator 13, combined by winding or laminating, fixed with tape for the entire laminated structure, and after hot pressing, the electrode core is obtained. It is placed in a shape-matching aluminum-plastic film, and after ear heat sealing, side sealing, liquid injection, formation, air extraction, and encapsulation, the lithium-ion battery 10 is finally obtained.

[0097] As Figure 2 shown, Figure 2 This is the second structural schematic diagram of a battery provided by an embodiment of the present application.

[0098] Hereinafter, the second active material layer 113 of the positive electrode and the second active material layer 123 of the negative electrode will be used for distinction.

[0099] In a possible implementation manner, the electrode sheet further includes a second active material layer 3. The second active material layer 3 is disposed between the first active material layer 2 and the current collector 1, and the second active material layer 3 is connected to the first active material layer 2.

[0100] The setting method of the multi-layer active materials can realize the differential distribution of the types and concentrations of the materials in the thickness direction of the electrode sheet, so that the setting of the electrode sheet can meet various practical scenarios and improve the flexibility of the setting of the electrode sheet.

[0101] It can be understood that in this case, the positive electrode sheet 11 includes the first active material layer of the positive electrode and the second active material layer 113 of the positive electrode, and the negative electrode sheet 12 only includes the first active material layer 122 of the negative electrode; or the negative electrode sheet 12 includes the first active material layer 122 of the negative electrode and the second active material layer 123 of the negative electrode, and the positive electrode sheet 11 only includes the first active material layer 112 of the positive electrode; or it can also be that the positive electrode sheet 11 includes the first active material layer 112 of the positive electrode and the second active material layer 113 of the positive electrode, and the negative electrode sheet 12 includes the first active material layer 122 of the negative electrode and the second active material layer 123 of the negative electrode.

[0102] For example, continue to refer to Figure 2 , Figure 2 in which the positive electrode sheet 11 includes the first active material layer 112 of the positive electrode and the second active material layer 113 of the positive electrode, and the negative electrode sheet 12 includes the first active material layer 122 of the negative electrode and the second active material layer 123 of the negative electrode.

[0103] Here, for the positive electrode sheet 11 and the negative electrode sheet 12, the first active material layer 2 is closer to the separator 13 than the second active material layer 3, and the second active material layer 3 is closer to the current collector 1 than the first active material layer 2. Compared with the first active material layer 2, an increase in the ratio of the active material in the second active material layer 3 is beneficial to improving the energy density of the battery cell, and thus beneficial to providing a faster transmission speed for lithium ions.

[0104] The first active material layer 2 is closer to the current collector 1 and is provided with a piezoelectric material. Under the condition of satisfying the insertion and extraction of lithium ions from the active material, a faster surface transmission speed is provided for lithium ions, and surface lithium deposition is inhibited, thereby improving the charging and discharging speeds.

[0105] The second active material layer 3 is not provided with a piezoelectric material. When lithium ions pass through the second active material layer 3, there is no hindrance of the piezoelectric material to lithium ions, so that the speed of lithium ions passing through the first active material layer 2 can be increased.

[0106] In a possible implementation manner, the thickness of the first active material layer 2 accounts for 5%-50% of the sum of the thicknesses of the first active material layer 2 and the second active material layer 3.

[0107] In a possible implementation manner, the thickness of the first active material layer 2 accounts for 5%-20% of the sum of the thicknesses of the first active material layer 2 and the second active material layer 3.

[0108] Specifically, the thickness of the first active material layer 2 accounts for 5%, 10%, 15%, 20%, 25%, 35% or 50% of the sum of the thicknesses of the first active material layer 2 and the second active material layer 3.

[0109] The first active material layer 2 includes a piezoelectric material. The first active material layer 2 will provide a faster migration speed for lithium ions, but will cause a decrease in the mass ratio of the active material, resulting in a reduction in the energy storage efficiency.

[0110] Only setting the piezoelectric material in the second active material layer 3 can reduce the amount of the piezoelectric material, maximize the performance of the piezoelectric material, concentrate the action on the surface of the electrode sheet, improve the uniformity of the lithium ion distribution on the surface, inhibit the precipitation of lithium on the surface of the negative electrode sheet 12 during the fast charging process, and improve the fast charging performance of the battery cell.

[0111] In a possible implementation manner, the thickness of the first active material layer 2 or the second active material layer 3 is greater than or equal to 10 μm and less than or equal to 1000 μm.

[0112] Specifically, the thickness of the first active material layer 2 can be 10μm, 20μm, 50μm, 100μm, 150μm, 200μm, 300μm, 500μm, 750μm, 1000μm. The thickness of the second active material layer 3 can be 10μm, 20μm, 50μm, 100μm, 150μm, 200μm, 300μm, 500μm, 750μm, 1000μm. In this way, the thicknesses of the first active material layer 2 and the second active material layer 3 are appropriate, which can effectively accelerate the lithium-ion migration speed.

[0113] It should be noted that, according to factors such as the use of the battery 10, the volume of the battery 10, the power of the electrical device, the volume of the electrical setting, and the manufacturing process, the thicknesses of the first active material layer 2 and the second active material layer 3 can be set to appropriate thicknesses.

[0114] As Figure 3 shown, Figure 3 This is the third schematic structural diagram of a battery provided by an embodiment of the present application.

[0115] In a possible implementation manner, the second active material layer 3 includes a second piezoelectric material. Wherein, the polarization direction of the second active material layer 3 points from the surface facing the current collector 1 to the surface of the second active material layer 3 facing away from the current collector 1.

[0116] Continue to refer to Figure 3 , Figure 3 The positive electrode sheet 11 in [reference] includes a first active material layer 112 of the positive electrode and a second active material layer 113 of the positive electrode. The second active material layer 113 of the positive electrode includes a piezoelectric material, and the polarization direction of the second active material layer 113 points from the positive electrode to the negative electrode.

[0117] During the charging process, referring to the positive electrode sheet 11, a second active material layer 113 of the positive electrode is provided between the first active material layer 112 of the positive electrode and the current collector 111 of the positive electrode. The lithium ions are accelerated by the polarization electric field of the second active material layer 113 of the positive electrode and then by the polarization electric field of the first active material layer 112 of the positive electrode, which can make the migration speed of the lithium ions towards the separator 13 faster, thereby improving the charging speed.

[0118] Continue to refer to Figure 3 , Figure 3 The negative electrode sheet 12 in [reference] includes a first active material layer 122 of the negative electrode and a second active material layer 123 of the negative electrode. The polarization direction of the second active material layer 123 of the negative electrode points from the negative electrode to the positive electrode.

[0119] During the discharging process, lithium ions in the negative electrode are removed from the active material of the negative electrode and migrate towards the positive electrode. The polarization directions of both the first active material layer 122 and the second active material layer 123 of the negative electrode point from the negative electrode to the positive electrode. At this time, the movement direction of the lithium ions is the same as the polarization direction of the piezoelectric material.

[0120] After being accelerated by the second active material layer 123 of the negative electrode and then by the first active material layer 122 of the negative electrode, the migration speed of the lithium ions can be made faster, which is beneficial for the lithium ions to break away from the negative electrode active material, thereby improving the discharging speed.

[0121] It should be noted that the piezoelectric material and the active material included in the second active material layer 113 of the positive electrode can refer to the setting manner of the piezoelectric material and the active material in the first active material layer 112 of the positive electrode; the piezoelectric material and the active material included in the second active material layer 123 of the negative electrode can refer to the setting manner of the piezoelectric material and the active material included in the first active material layer 122 of the negative electrode.

[0122] In a possible implementation manner, the pole piece further includes a third active material layer or more active material layers. The setting of the third active material layer or more active material layers can refer to the setting manner of the second active material layer 3 relative to the first active material layer 2.

[0123] As Figure 4 shown, Figure 4 This is the fourth schematic diagram of the structure of a battery provided by an embodiment of the present application.

[0124] In a possible implementation manner, it further includes a conductive layer 4. The conductive layer 4 is located between the current collector 1 and the first active material layer 2 and is connected to the current collector 1 and the first active material layer 2.

[0125] The conductive layer 4 includes an adhesive and a conductive agent.

[0126] In a possible implementation manner, the thickness of the conductive layer 4 is greater than or equal to 0.1 μm and less than or equal to 10 μm. Specifically, the thickness of the conductive layer 4 can be 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm.

[0127] The conductive layer 4 includes an adhesive and a conductive agent.

[0128] The above-mentioned conductive agent includes at least one of carbon black (CB), carbon nanotube (CNT), acetylene black (AB), graphene, and whisker carbon nanotube (VGCF).

[0129] The above-mentioned adhesive includes at least one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol, polyimide, polyamide-imide, carboxymethyl cellulose salt (CMC-Li or Na or K), polyacrylate (PAA-Li or Na or K), polyvinyl butyral (PVB), and aqueous acrylic resin.

[0130] In the case where the second active material layer 3 is provided, the conductive layer 4 can be provided between the second active material layer 3 and the current collector 1. Specifically, the conductive layer 4 is provided between the second active material layer 113 of the positive electrode and the current collector 111 of the positive electrode, and / or the conductive layer 4 is provided between the second active material layer 123 of the negative electrode and the current collector 121 of the negative electrode.

[0131] In a possible implementation manner, and in the case where the second active material layer 3 is provided, the conductive layer 4 can be provided between the second active material layer 3 and the first active material layer 2, and the conductive layer 4 can make the migration of lithium ions smoother.

[0132] As Figure 5 shown, Figure 5 FIG. 5 is a schematic structural diagram of a battery provided by an embodiment of the present application.

[0133] In a possible implementation manner, the first active material layer 2 is in a polarized state, and the polarization direction of the first active material layer 2 points from the surface of the first active material layer 2 facing away from the current collector 1 to the surface of the first active material layer 2 facing the current collector 1.

[0134] As Figure 5 in the positive electrode sheet 11, during the discharge process, lithium ions at the negative electrode sheet 12 are released from the active material of the negative electrode and migrate to the positive electrode. When the lithium ions cross the separator 13 and migrate to one side of the positive electrode, the polarization direction of the first active material layer 112 of the positive electrode points from the negative electrode to the positive electrode. At this time, the movement direction of the lithium ions is the same as the polarization direction of the piezoelectric material. Thus, the migration speed of lithium ions to the positive electrode is accelerated, which is beneficial to embedding into the positive electrode active material, and further improves the discharge speed.

[0135] The setting method of the second active material layer 3 can refer to Figure 2 the setting method shown in the implementation, which will not be elaborated here.

[0136] The above embodiments introduce the structural forms, application scenarios, and related information of the electrode sheets provided by the embodiments of the present application. Next, the performance of the electrode sheets provided by the present application is tested through comparative experiments.

[0137] Example 1 of the present application:

[0138] A lithium-ion battery 10 is fabricated using the positive electrode sheet 11 and the negative electrode sheet 12 of the present application.

[0139] The positive electrode sheet 11 is composed of a current collector 1, a first active material layer 2, and a second active material layer. The current collector 1 is a 13 μm aluminum foil, and the active material (lithium iron phosphate): piezoelectric material (barium titanate): conductive agent (CB): adhesive (PVDF) in the first active material layer 2 is 94:2.5:1.5:2. The active material (lithium iron phosphate): conductive agent (CB): adhesive (PVDF) in the second active material layer 3 is 96.5:1.5:2, and the thickness of the first active material layer 2 accounts for 20% of the total thickness of the first active material layer 2 and the second active material layer 3.

[0140] First, PVDF is dissolved in N-methylpyrrolidone (NMP), and a conductive agent, barium titanate and lithium iron phosphate are added. After being fully stirred and dispersed, a slurry with a solid content of 55% is obtained. Then, the upper and lower slurries are coated on the surface of the current collector through a double-layer coating die to form a first active material layer 2 and a second active material layer 3. After baking and rolling, a positive electrode sheet 11 is obtained, and the thickness of the electrode sheet is 164μm. The positive electrode sheet 11 is placed in a parallel electric field for air polarization, and the polarization electric field strength is 8kV / mm, and the polarization time is 40min.

[0141] The negative electrode sheet 12 is composed of a current collector 1, a first active material layer 2, and a second active material layer 3. The current collector 1 is a 6μm copper foil. The ratio of each material in the first active material layer 2 is active material (graphite): piezoelectric material (barium titanate): conductive agent (CB): adhesive (CMC): adhesive (SBR) = 93:3:1:1:2, and the ratio of each material in the second active material layer 3 is active material (graphite): conductive agent (CB): adhesive (CMC): adhesive (SBR) = 96:1:1:2. The thickness of the first active material layer 2 accounts for 30% of the total thickness of the first active material layer 2 and the second active material layer 3. The two layers of slurry are prepared separately, and the process is the same.

[0142] First, CMC-Na is dissolved in deionized water, and a conductive agent, barium titanate and graphite are added. After being fully stirred, SBR is added to obtain a slurry with a solid content of 52%. The slurry is then coated on the surface of the copper foil through a double-layer coating process, and the negative electrode sheet 12 is obtained after baking and rolling. The thickness of the electrode sheet is 115 μm. The negative electrode sheet 12 is placed in a parallel electric field for air polarization, and the polarization electric field strength is 8 kV / mm, and the polarization time is 40 minutes.

[0143] The positive electrode sheet 11 , the negative electrode sheet 12 and the separator 13 are wound to prepare a battery cell, and then an aluminum-plastic film is placed therein for baking, liquid injection, chemical formation, degassing and sealing, so as to finally obtain a lithium-ion battery 10 .

[0144] Embodiment 2 of the present application:

[0145] Compared with Embodiment 1 of the present application, the first active material layer 2 in the positive electrode sheet 11 does not contain a piezoelectric material, and other settings are the same.

[0146] Embodiment 3 of the present application:

[0147] Compared with Embodiment 1 of the present application, the first active material layer 2 in the negative electrode sheet 12 does not contain a piezoelectric material, and other settings are the same.

[0148] Embodiment 4 of the present application:

[0149] Compared with Embodiment 1 of the present application, the first active material layer 2 in the positive electrode sheet 11 does not contain a piezoelectric material, and the negative electrode sheet 12 only includes the first active material layer 2, and the second active material layer 3 is not provided.

[0150] Comparative Example 1:

[0151] Compared with Embodiment 1 of the present application, the first active material layer 2 in the positive electrode sheet 11 does not contain a piezoelectric material, and the first active material layer 2 in the negative electrode sheet 12 does not contain a piezoelectric material, and other settings are the same as those in Embodiment 1 of the present application.

[0152] After experiments, the charging speed of Embodiment 2 of the present application is lower than that of Embodiment 1 of the present application. The charging speed of Embodiment 3 of the present application is lower than that of Embodiment 1 of the present application. The charging speed of Embodiment 4 of the present application is lower than that of Embodiment 2 of the present application.

[0153] The charging speed of Comparative Example 1 is lower than that of Embodiment 3 of the present application. And during the experiment, when comparing Comparative Example 1 with Embodiment 2 of the present application, Embodiment 2 of the present application can reduce the phenomenon of lithium plating caused by excessive deposition of lithium ions.

[0154] According to the experiments of comparing Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1 of the present application, it can be proved that the setting method of the present application can improve the charging speed. It is measured that the provided electrode sheet of the present application can accelerate the migration speed of lithium ions from the positive electrode to the negative electrode, so as to improve the charging speed of the battery 10.

[0155] According to the experimental comparison of Embodiment 2 and Comparative Example 2 of the present application, the method of setting the second active material layer 3 between the first active material layer 2 and the current collector 1 can improve the charging speed of the battery 10.

[0156] Although the present application has been described in connection with various embodiments, those skilled in the art will recognize other variations of the disclosed embodiments while practicing the claimed present application by referring to the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may implement several functions recited in the claims. Certain measures are recited in mutually different dependent claims, but this does not mean that these measures cannot be combined to produce favorable results.

[0157] Although the present application has been described in connection with specific features and their embodiments, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the present application. Accordingly, the specification and drawings are merely exemplary illustrations of the present application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the present application. Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these changes and modifications.

[0158] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of changes or substitutions within the technical scope disclosed by the present invention, and all such changes or substitutions should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the said claims.

Claims

1. A pole piece, characterized in that: include: current collector(1); A first active material layer (2), wherein the first active material layer (2) is provided on at least one side of the current collector (1), and the first active material layer (2) comprises a first piezoelectric material; and the polarization direction of the first active material layer (2) is consistent with the thickness direction of the first active material layer (2).

2. The pole piece according to claim 1, characterized in that: The polarization direction of the first active material layer (2) is from the surface of the first active material layer (2) facing the current collector (1) to the surface of the first active material layer (2) facing away from the current collector (1).

3. The pole piece according to claim 1, characterized in that: The polarization direction of the first active material layer (2) is from the surface of the first active material layer (2) facing away from the current collector (1) to the surface of the first active material layer (2) facing the current collector (1).

4. The pole piece according to claim 1, characterized in that: Also includes: A second active material layer (3), wherein the second active material layer (3) is disposed between the first active material layer (2) and the current collector (1).

5. The pole piece according to claim 4, characterized in that: The second active material layer (3) does not include a piezoelectric material.

6. The pole piece according to claim 4, characterized in that: The second active material layer (3) comprises a second piezoelectric material; the polarization direction of the second active material layer (3) is consistent with the polarization direction of the first active material layer (2).

7. The pole piece according to claim 4, characterized in that: The thickness of the first active material layer (2) accounts for 5% to 50% of the sum of the thicknesses of the first active material layer (2) and the second active material layer (3).

8. The pole piece according to claim 7, characterized in that: The thickness of the first active material layer (2) accounts for 5% to 20% of the sum of the thicknesses of the first active material layer (2) and the second active material layer (3).

9. The pole piece according to claim 4, characterized in that: The thickness of the first active material layer (2) or the second active material layer (3) is greater than or equal to 10 μm and less than or equal to 1000 μm.

10. The pole piece according to claim 9, characterized in that: The thickness of the first active material layer (2) or the second active material layer (3) is greater than or equal to 50 μm and less than or equal to 250 μm.

11. The pole piece according to claim 1, characterized in that: It also includes a conductive layer (4), which is located between the current collector (1) and the first active material layer (2).

12. The pole piece according to claim 1, characterized in that: The electrode piece is a positive electrode piece or a negative electrode piece.

13. A battery (10), characterized in that: A pole piece comprising any one of claims 1-12.

14. An electrical device, characterized in that: Comprising the battery (10) as claimed in claim 13.

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