Electrode plate and preparation method thereof, battery and power utilization device

Abstract

The invention relates to an electrode plate and a preparation method thereof, a battery and an electric device, the electrode plate comprises a current collector and an active material layer arranged on at least one surface of the current collector, the active material layer comprises an active substance, the active material layer comprises a pore-forming agent, the pore-forming agent comprises a micromolecular quinone organic compound and a derivative thereof, and the molecular weight of the micromolecular quinone organic compound is 10 Da to 1000 Da. Part of the pore-forming agent in the active material layer of the electrode plate can be dissolved in the organic solvent, pores are generated in the active material layer, transmission of active ions in the active material layer is facilitated, the rate capability of the battery is improved, and the dissolved pore-forming agent can be recycled. The pore-forming agent reserved in the active material layer of the electrode plate can be used as an active substance, part of lithium ions are stored, and the risk of lithium separation is reduced. The preparation method of the electrode plate can adapt to the existing process, reduces the pore-forming cost of the electrode plate, and also reduces the risk of active substance loss caused by an etching pore-forming means.

Description

Technical Field

[0001] The present application relates to the field of electrochemical energy storage, and in particular to an electrode sheet and a preparation method thereof, a battery and an electrical device. Background Art

[0002] Increasing the coating thickness of the electrode sheet can significantly increase the energy density of the battery (such as lithium-ion battery) cell, but as the electrode thickness increases, the electrolyte will become less wettable to the electrode, which may lead to the obstruction of the liquid phase transmission of active ions (such as lithium ions), thereby increasing the internal resistance of the battery and attenuating the battery rate performance. Therefore, the liquid phase transmission efficiency of lithium ions in thick electrodes needs to be improved. Summary of the invention

[0003] In view of this, the present application provides an electrode sheet and a preparation method thereof, a battery and an electrical device to solve at least one of the above technical problems.

[0004] To achieve the above-mentioned purpose, in a first aspect, the present application provides an electrode sheet, comprising a current collector and an active material layer disposed on at least one surface of the current collector, wherein the active material layer comprises an active substance. The active material layer comprises a pore former, wherein the pore former comprises a small molecule quinone organic compound and a derivative thereof, wherein the molecular weight of the small molecule quinone organic compound and a derivative thereof is 10 Da to 1000 Da.

[0005] The present application uses small molecule quinone organic compounds and their derivatives as pore formers for electrode sheets. By adding the pore former to the electrode sheet slurry to form an active material layer, part of the pore former in the active material layer can be dissolved in an organic solvent (such as an electrolyte), thereby generating pores in the active material layer. These pores are conducive to the transmission of active ions (such as lithium ions) in the active material layer, thereby improving the rate performance of the battery; and the dissolved pore former basically does not undergo a chemical reaction, and the pore former and the organic solvent can be separated by heating, so the separated pore former can be reused. The pore former of the present application can also be used in the positive electrode or the negative electrode according to its redox potential. For example, in the fast charging state of the battery, the undissolved part of the pore former in the active material layer of the negative electrode sheet can store lithium ions that cannot be embedded in the negative electrode active material due to insufficient kinetics, thereby reducing the risk of lithium precipitation in the negative electrode sheet and improving the safety of the battery. Controlling the molecular weight of small molecule quinone organic compounds and their derivatives within a preset range is conducive to better dissolution of the pore former and formation of pores, and is also conducive to the pore former retained in the active material layer to store more lithium ions and provide higher capacity. In addition, the electrode sheet of the present application can adapt to the existing electrode sheet preparation process, without the need to use an additional pore-forming device or to modify the pore-forming device, which reduces the cost of electrode sheet pore making and reduces the risk of active material loss caused by etching-type pore-making methods.

[0006] Based on the first aspect, in some possible implementations, the small molecule quinone organic compound and its derivatives include one or more of p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthraquinone, 9,10-phenanthrenequinone and alizarin. The above small molecule quinone organic compounds and their derivatives can be dissolved in an organic solvent to leave pores on the electrode sheet, and can also be used in the positive electrode or the negative electrode according to their redox potential, as active substances, with high rate characteristics.

[0007] Based on the first aspect, in some possible implementations, the mass content of the pore former in the active material layer is 0.1% to 20%. Controlling the mass content of the pore former within this range is conducive to forming an appropriate amount of pores in the active material layer, and is also conducive to the undissolved part of the pore former in the electrode sheet to store some lithium ions, further reducing the risk of lithium deposition in the negative electrode sheet.

[0008] Based on the first aspect, in some possible implementations, the active material layer includes a first surface facing the current collector and a second surface arranged opposite to the first surface, and the mass content of the pore former in the active material layer gradually increases along the direction from the first surface to the second surface. In thick electrodes, it is difficult to wet the bottom of the electrode sheet. If too much pore former is added, it may be difficult to completely dissolve. By setting the mass content relationship of the pore former in the active material layer, it is beneficial to control or promote the porosity of the surface layer of the electrode sheet after the pore former is dissolved to be higher, which is beneficial for the electrolyte to better contact with the underlying active material, and achieve a state similar to the contact between the surface of the electrode without a pore former and the electrolyte, thereby improving the electrolyte wettability of the underlying active material, while controlling the porosity of the electrode sheet within an appropriate range, which is beneficial for maintaining a good energy density.

[0009] Based on the first aspect, in some possible implementations, the thickness of the active material layer on any surface of the current collector is 20 μm to 300 μm. By setting the thickness of the active material layer, the rate performance of the battery and the liquid retention of the electrode sheet can be improved while increasing the energy density of the electrode sheet.

[0010] Based on the first aspect, in some possible implementations, the electrode sheet is a negative electrode sheet. When the electrode sheet is a negative electrode sheet, in the fast charging state of the battery, the undissolved part of the pore former in the active material layer of the negative electrode sheet can store lithium ions that cannot be embedded in the negative electrode active material due to insufficient kinetics, reducing the risk of lithium precipitation in the negative electrode sheet, thereby improving the safety of the battery. In particular, in some cases, the undissolved part of the pore former in the active material layer of the negative electrode sheet stores lithium ions by forming coordination bonds with lithium ions, reducing the bulk diffusion of lithium ions inside the electrode material, thereby improving the rate performance.

[0011] In a second aspect, the present application provides a method for preparing an electrode sheet, the preparation method comprising: providing an active material layer on at least one surface of a current collector, the active material layer comprising a pore former, and the pore former comprising a small molecule quinone organic compound and its derivatives.

[0012] Based on the second aspect, in some possible implementations, the preparation method further includes: contacting the active material layer with an organic solvent to dissolve the pore former in the organic solvent; and drying the active material layer to obtain an electrode sheet.

[0013] Based on the second aspect, in some possible implementations, the organic solvent includes one or more of an electrolyte solvent, acetone, toluene, dichloromethane, chloroform, ethyl acetate, acetonitrile, methanol, and petroleum ether. The organic solvent is selected from the above substances to dissolve the pore former and is conducive to reducing the dissolution of the binder in the active material layer.

[0014] The present application uses small molecule quinone organic compounds and their derivatives as pore formers for electrode sheets. The electrode sheets can adapt to the existing electrode sheet preparation process, and there is no need to use an additional pore-forming device or to modify the pore-forming device, which reduces the cost of electrode sheet pore-forming and reduces the loss of active substances caused by etching-type pore-forming methods. In the above preparation method, the electrode sheet containing the pore-forming agent in the active material layer is contacted with an organic solvent (such as soaking) to dissolve part of the pore-forming agent in the organic solvent, thereby reserving pores on the electrode sheet, and the pore-forming method is simple. Furthermore, the porosity of the electrode sheet can be controlled by controlling the contact time with the organic solvent (such as soaking time), so that the porosity is adjustable, and thus it can be applied to the pore-forming requirements of electrode sheets of different thicknesses.

[0015] In a third aspect, the present application provides a battery, which includes the above-mentioned electrode sheet, or includes the electrode sheet prepared by the above-mentioned preparation method.

[0016] After the above-mentioned electrode sheets are assembled into a battery, on the one hand, the pore-forming agent in the active material layer of the electrode sheet will be partially dissolved in the electrolyte in the battery, causing pores in the electrode sheet, which is beneficial to shorten the transmission path of lithium ions, improve the rate performance of lithium-ion batteries, and also help to increase the liquid retention of the electrode sheet, thereby helping to extend the life of the battery; on the other hand, the retained part of the pore-forming agent in the active material layer of the electrode sheet can also be used in the positive electrode or negative electrode as an active substance according to its redox potential.

[0017] In a fourth aspect, the present application provides an electrical device, which includes the above-mentioned battery. DETAILED DESCRIPTION

[0018] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present application; in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other; many specific details are explained in the following description to facilitate a full understanding of the present application, and the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0019] In the related art, pores or holes are usually set on the electrode sheet (electrode pore making) to alleviate the existing problems of the thick electrode part. At present, electrode pore making mostly uses laser or roller pressing to make pores on the electrode sheet. However, the efficiency of laser pore making is not high, and the precision control is difficult. Laser ablation may also cause the loss of active substances and also involve the modification of manufacturing equipment. Roller pressing pore making involves the fine manufacturing of roller pressing equipment, which has high requirements for processing accuracy, and the service life of the mold used for rolling is also an issue that needs to be considered in production costs. Therefore, there is a need for an electrode sheet whose preparation method is simple and easy, basically compatible with the current production process or low in cost, to make up for the shortcomings of the existing electrode sheet pore making method and achieve the purpose of improving the electrochemical performance of the resulting battery.

[0020] Based on this, an embodiment of the present application provides a battery, including a housing, an electrode assembly and an electrolyte. The battery can be a lithium ion battery, a sodium ion battery or a potassium ion battery. The electrode assembly and the electrolyte are both located in the housing.

[0021] The outer shell may be a packaging bag encapsulated by an encapsulation film (such as an aluminum-plastic film), for example, a soft-pack battery. In other embodiments, it may also be a steel shell battery, an aluminum shell battery, etc.

[0022] The electrode assembly includes an electrode sheet and a separator, the electrode sheet includes a positive electrode sheet and a negative electrode sheet, and the separator is used to separate the positive electrode sheet and the negative electrode sheet, and can be arranged between the positive electrode sheet and the negative electrode sheet. In some embodiments, the electrode assembly can be a laminated structure, for example, it is formed by alternatingly stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence. In other embodiments, the electrode assembly can also be a winding structure, for example, it is formed by stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence and then winding them.

[0023] Electrode sheet The electrode sheet includes a current collector and an active material layer disposed on at least one surface of the current collector. In the present application, the active material layer of the electrode sheet includes a pore former, and the pore former includes a small molecule quinone organic compound and its derivatives, and the molecular weight of the small molecule quinone organic compound and its derivatives is 10 Da to 1000 Da. For example, the molecular weight of the small molecule quinone organic compound and its derivatives can be 10 Da, 20 Da, 30 Da, 50 Da, 100 Da, 200 Da, 300 Da, 500 Da, 800 Da, 1000 Da or any value within the range formed by any two of the above values.

[0024] The present application uses small molecule quinone organic compounds and their derivatives as pore formers for electrode sheets. By adding the pore former to the electrode sheet slurry to form an active material layer, part of the pore former in the active material layer can be dissolved in an organic solvent (such as an electrolyte), thereby generating pores in the active material layer. These pores are conducive to the transmission of active ions (such as lithium ions) in the active material layer, thereby improving the rate performance of the battery; and the dissolved pore former basically does not undergo a chemical reaction, and the pore former and the organic solvent can be separated by heating, so the separated pore former can be reused. The pore former of the present application can also be used in the positive electrode or the negative electrode according to its redox potential. For example, in the fast charging state of the battery, the undissolved part of the pore former in the active material layer of the negative electrode sheet can store lithium ions that cannot be embedded in the negative electrode active material due to insufficient kinetics, thereby reducing the risk of lithium precipitation in the negative electrode sheet and improving the safety of the battery. Controlling the molecular weight of small molecule quinone organic compounds and their derivatives within a preset range is conducive to better dissolution of the pore former and formation of pores, and is also conducive to the pore former retained in the active material layer to store more lithium ions and provide higher capacity. In addition, the electrode sheet of the present application can adapt to the existing electrode sheet preparation process, without the need to use an additional pore-forming device or to modify the pore-forming device, which reduces the cost of electrode sheet pore making and reduces the risk of active material loss caused by etching-type pore-making methods.

[0025] It can be understood that when the molecular weight of small molecule quinone organic compounds and their derivatives is greater than the preset upper limit, the proportion of active ingredients in the pore-forming agent used for lithium storage may be relatively reduced, and the inactive ingredients may increase, thereby resulting in a decrease in the specific capacity that can be provided by the pore-forming agent retained in the active material layer.

[0026] In some embodiments, the small molecule quinone organic compound and its derivatives include one or more of p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthraquinone, 9,10-phenanthrenequinone and alizarin. The above small molecule quinone organic compounds and their derivatives can be dissolved in an organic solvent to leave pores on the electrode sheet, and can also be used in the positive electrode or negative electrode according to their redox potential, as active substances, with high rate characteristics.

[0027] In some embodiments, the mass content of the pore former in the active material layer is 0.1% to 20%. For example, the mass content of small molecule quinone organic compounds and their derivatives can be 0.1%, 0.4%, 0.50%, 0.60%, 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, or any value within the range formed by any two of the above values. Controlling the mass content of the pore former within this range is conducive to forming an appropriate amount of pores in the active material layer, and is also conducive to the undissolved part of the pore former in the electrode sheet to store some lithium ions, further reducing the risk of lithium precipitation in the negative electrode sheet.

[0028] In some embodiments, the active material layer includes a first surface facing the current collector and a second surface arranged opposite to the first surface, and the mass content of the pore former in the active material layer gradually increases along the direction from the first surface to the second surface. In thick electrodes, it is difficult to wet the bottom of the electrode sheet. If too much pore former is added, it may be difficult to completely dissolve. By setting the mass content relationship of the pore former in the active material layer, it is beneficial to control or promote the porosity of the surface of the electrode sheet after the pore former is dissolved to be higher, which is beneficial for the electrolyte to better contact with the underlying active material, and achieve a state similar to the contact between the surface of the electrode without a pore former and the electrolyte, thereby facilitating the improvement of the electrolyte wettability of the underlying active material, while controlling the porosity of the electrode sheet within a suitable range, which is beneficial to maintaining a good energy density. It can be understood that when the mass content of the pore former in the active material layer exceeds the preset relationship, the porosity of the bottom layer of the electrode sheet may increase, which may cause the overall pores of the electrode sheet to be more, resulting in a decrease in energy density.

[0029] In some embodiments, the thickness of the active material layer on any surface of the current collector is 20 μm to 300 μm. For example, the thickness of the active material layer can be 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, or any value within the range formed by any two of the above values. The thickness of the active material layer is controlled within the above range, which is beneficial to improve the energy density of the electrode sheet, such as forming a thick electrode. The present application uses small molecule quinone organic compounds and their derivatives as pore-forming agents for electrode sheets, which can improve the rate performance of the battery and the liquid retention of the electrode sheet while increasing the energy density of the electrode sheet.

[0030] The electrode sheet may be a positive electrode sheet and / or a negative electrode sheet.

[0031] When the electrode sheet is a negative electrode sheet, in the fast charging state of the battery, the undissolved part of the pore former in the active material layer of the negative electrode sheet can store lithium ions that cannot be embedded in the negative electrode active material due to insufficient kinetics, reducing the risk of lithium precipitation in the negative electrode sheet, thereby improving the safety of the battery. In particular, in some cases, the undissolved part of the pore former in the active material layer of the negative electrode sheet stores lithium ions by forming coordination bonds with lithium ions, reducing the bulk diffusion of lithium ions inside the electrode material, thereby improving the rate performance.

[0032] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector may be at least one of copper foil, nickel foil, stainless steel foil, titanium foil or a carbon-based current collector, or may be any composite current collector disclosed in the prior art, such as but not limited to a current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0033] The negative electrode active material layer includes a negative electrode material, and the negative electrode material includes graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiOx (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structured lithium titanate, lithiated TiO2-Li4Ti5O 12 , Li-Al alloy and at least one of metallic lithium.

[0034] The negative electrode active material layer also includes a binder to bind the negative electrode active material particles to facilitate the formation of a film layer, and can also improve the binding force between the negative electrode active material layer and the negative electrode current collector. In some embodiments, the binder may include but is not limited to polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon, etc.

[0035] The negative electrode active material layer may also include a conductive material, including but not limited to a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some embodiments, the carbon-based material may include but is not limited to natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material may include but is not limited to metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0036] When the electrode sheet is a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode current collector may be made of aluminum foil or nickel foil, etc., or may be any composite current collector disclosed in the prior art, such as but not limited to the current collector formed by combining the aforementioned conductive foil and the polymer substrate. The positive electrode active material layer includes a positive electrode material, and the positive electrode material includes a compound that can reversibly embed and deintercalate lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the positive electrode material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the positive electrode material may include but is not limited to lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4) or at least one of lithium iron phosphate (LiFePO4).

[0037] The positive electrode active material layer may also include a binder to bond the positive electrode active material particles to facilitate the formation of a film layer, and at the same time, to improve the bonding force between the positive electrode active material layer and the positive electrode current collector. In some embodiments, the binder may include but is not limited to at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin or nylon.

[0038] The positive electrode active material layer may also include a conductive material, including but not limited to a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some embodiments, the carbon-based material may include but is not limited to natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material may include but is not limited to metal powder or metal fiber, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0039] Isolation film The isolation membrane includes a membrane layer with a porous structure, and the material includes but is not limited to at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid. For example, the isolation membrane can be a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane.

[0040] Electrolyte The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. In some embodiments, the electrolyte includes a lithium salt and an organic solvent. The lithium salt can be selected from but not limited to one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO2CF3)2, tris(trifluoromethylsulfonyl)methyl lithium (LiC(SO2CF3)3), lithium bis(oxalatoborate) (LiBOB) and lithium difluorophosphate (LiPO2F2). For example, the lithium salt is selected from LiPF6 because it can give high ionic conductivity and improve cycle characteristics. The organic solvent can be a carbonate compound, a carboxylate compound, an ether compound, Compounds, nitrile compounds, other organic solvents or combinations thereof. Examples of carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene 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, trifluoromethylethylene carbonate or combinations thereof.

[0041] An embodiment of the present application further provides a method for preparing an electrode sheet, comprising: Step 1: an active material layer is provided on at least one surface of the current collector, wherein the active material layer comprises a pore former, and the pore former comprises a small molecule quinone organic compound and a derivative thereof.

[0042] In some embodiments, the active material layer can be provided in the following manner: providing the active material layer on the surface of the current collector includes applying a coating composition on at least one surface of the current collector, the coating composition includes a pore former, and the pore former includes a small molecule quinone organic compound and its derivatives. Then, the current collector coated with the coating composition can be preliminarily dried and rolled to obtain the active material layer. The present application uses small molecule quinone organic compounds and their derivatives as pore formers. After the coating composition including the pore former forms a coating, part of the pore former in the coating can be dissolved in an organic solvent, thereby generating pores in the coating.

[0043] In some embodiments, the small molecule quinone organic compound and its derivatives include one or more of p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthraquinone, 9,10-phenanthrenequinone and alizarin. The above small molecule quinone organic compounds and their derivatives can leave pores on the coating by dissolving in an organic solvent.

[0044] In some embodiments, the coating composition further comprises one or more of a conductive agent, a binder and an active material, and the active material comprises one of a positive electrode material and a negative electrode material. The pore-forming agent of the present application is applied to the coating slurry of the electrode sheet, and can generate pores in the coating of the electrode sheet by dissolving in an organic solvent.

[0045] In some embodiments, the active material layer includes a first surface facing the current collector and a second surface disposed opposite to the first surface, and the mass content of the pore former in the active material layer gradually increases along the direction from the first surface to the second surface. It can be understood that the layered arrangement of the above-mentioned active material layer on the current collector can be achieved by configuring coating compositions with different mass contents of the pore former, first applying a coating composition with a lower mass content of the pore former on one surface of the current collector, and then applying a coating composition with a higher mass content of the pore former.

[0046] In some embodiments, the rolled structure can also be cut to obtain an electrode sheet. In the present application, small molecule quinone organic compounds and their derivatives are used as pore-forming agents for electrode sheets. The electrode sheet can adapt to the above-mentioned existing electrode sheet preparation process, without the need for additional pore-forming devices or modification of the pore-forming devices, thereby reducing the cost of electrode sheet pore-forming and reducing the loss of active substances caused by etching-type pore-forming methods.

[0047] In some embodiments, the method for preparing the electrode sheet further comprises: Step 2: contacting the active material layer with an organic solvent to dissolve the pore former in the organic solvent; drying the active material layer to obtain an electrode sheet.

[0048] During the above-mentioned contact (such as immersion), part of the pore former in the active material layer can be dissolved in the organic solvent, thereby reserving pores on the electrode sheet, and the pore forming method is simple; moreover, the dissolved pore former basically does not undergo chemical reaction, and the organic solvent is evaporated by heating, so that the pore former and the organic solvent can be separated, and the separated pore former can be reused. In some embodiments, an additional collection device can be added to the heating process to collect the evaporated organic solvent. Since the pore former dissolved in the organic solvent basically does not undergo chemical reaction, the organic solvent can be separated by an additional collection device, and the dissolved pore former can be recovered, so as to achieve the purpose of reusing the pore former, which is conducive to cost saving.

[0049] In some embodiments, the porosity of the electrode sheet can be controlled by controlling the contact time with the organic solvent (such as the immersion time), so that the porosity is adjustable and can be applied to the pore formation requirements of electrode sheets of different thicknesses.

[0050] In some embodiments, the organic solvent includes one or more of electrolyte solvent, acetone, toluene, dichloromethane, chloroform, ethyl acetate, acetonitrile, methanol and petroleum ether. The organic solvent selected from the above substances can dissolve the pore former and is conducive to reducing the dissolution of the binder in the active material layer.

[0051] In some embodiments, the electrode sheet prepared by the above preparation method can be directly used to assemble into a battery. The preparation process of adding small molecule quinone organic compounds and their derivatives as pore-forming agents in the present application can adapt to the above existing electrode sheet preparation process, and the battery assembly and liquid injection steps are consistent with the conventional process, and the infiltration, formation, secondary injection and volume separation processes are all consistent with the conventional process.

[0052] Another embodiment of the present application provides a battery, which includes the electrode sheet provided in the above embodiment, or includes an electrode sheet prepared by the method for preparing the electrode sheet provided in the above embodiment.

[0053] After the above-mentioned electrode sheets are assembled into a battery, on the one hand, the pore-forming agent in the active material layer of the electrode sheet will be partially dissolved in the electrolyte in the battery, causing pores in the electrode sheet, which is beneficial to shorten the transmission path of lithium ions and improve the rate performance of lithium-ion batteries. It is also beneficial to increase the liquid retention capacity of the electrode sheet, thereby helping to extend the life of the battery; on the other hand, the retained part of the pore-forming agent in the active material layer of the electrode sheet can also be used in the positive electrode or negative electrode as an active substance according to its redox potential.

[0054] Another embodiment of the present application also provides an electrical device, including the above-mentioned battery. In some embodiments, the battery of the present application can be used for but not limited to the following electrical devices: laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0055] The scheme of the present application will be explained below in conjunction with the embodiments. Those skilled in the art will understand that the following examples are only used to explain the present application and cannot be construed as limiting the present application. Unless otherwise stated, the reagents, software and instruments not specifically stated in the following embodiments are all conventional commercial products or open source.

[0056] Embodiment 1: A soft pack battery, the preparation method of which comprises: S1, select LiFePO4 as the positive electrode material, mix LiFePO4, Super P and polyvinylidene fluoride (PVDF) in a mass ratio of 96:2:2, apply it on the aluminum foil current collector, dry it in an oven, and then roll it to obtain the required positive electrode sheet.

[0057] S2, select graphite as the negative electrode material, mix graphite, styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), p-benzoquinone and Super P in a mass ratio of 97.2:1.2:0.8:0.4:0.4, and apply it on the copper foil current collector as the lower layer; mix graphite, styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), p-benzoquinone and Super P in a mass ratio of 97:1.2:0.8:0.6:0.4 as the upper layer slurry, dry it in an oven, and then roll it to obtain the required negative electrode sheet.

[0058] S3, a 2.5 Ah soft-pack battery was made by the Z-shaped stacking method, the electrolyte was injected in an argon glove box with an injection coefficient of 2.6, and it was left to rest at 45 °C for 48 h.

[0059] Embodiment 2: The difference from Example 1 is that in S1, LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the positive electrode material.

[0060] Embodiment 3: The difference from Example 1 is that in S2, graphite / silicon carbon is selected as the negative electrode material.

[0061] Embodiment 4: The difference from Example 1 is that in S2, p-benzoquinone is replaced by o-benzoquinone.

[0062] Embodiment 5: The difference from Example 1 is that in S1, a certain amount of 1,2-naphthoquinone is added to the mixture, that is, LiFePO4, 1,2-naphthoquinone, Super P and polyvinylidene fluoride (PVDF) are evenly mixed in a mass ratio of 95.4:0.6:2:2; in S2, p-benzoquinone is replaced by 1,2-naphthoquinone.

[0063] Embodiment 6: The difference from Example 1 is that in S1, a certain amount of 1,4-naphthoquinone is added to the mixture, that is, LiFePO4, 1,4-naphthoquinone, Super P and polyvinylidene fluoride (PVDF) are evenly mixed in a mass ratio of 95.4:0.6:2:2; in S2, p-benzoquinone is replaced by 1,4-naphthoquinone.

[0064] Embodiment 7: The difference from Example 1 is that in S2, p-benzoquinone is replaced by 9,10-anthraquinone.

[0065] Comparative Example 1: S1, select LiFePO4 as the positive electrode material, mix LiFePO4, Super P and polyvinylidene fluoride (PVDF) in a mass ratio of 96:2:2, apply it on the aluminum foil current collector, dry it in an oven, and then roll it to obtain the required positive electrode sheet.

[0066] S2, graphite is selected as the negative electrode material, graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC) and Super P are evenly mixed in a mass ratio of 97.6:1.2:0.8:0.4, coated on a copper foil current collector, dried in an oven, and then roll-pressed to obtain the desired negative electrode sheet.

[0067] S3, a 2.5 Ah soft-pack battery was made by the Z-shaped stacking method, the electrolyte was injected in an argon glove box with an injection coefficient of 2.6, and it was left to rest at 45 °C for 48 h.

[0068] The soft pack batteries of Examples 1-7 and Comparative Example 1 of the present application were subjected to performance tests, including: 1. Capacity test of soft-pack batteries: 1 C capacity test is carried out by constant current charge and discharge; 5 C capacity test is carried out by step charging, not constant current charge and discharge, and 5 C is the equivalent rate.

[0069] 2. Capacity retention rate test of soft-pack batteries: The capacity retention rate is calculated based on the first cycle discharge capacity.

[0070] 3. DC impedance test of soft-pack battery: DC impedance is measured at 25% SOC and discharged at a rate of 2 C for 10 s.

[0071] Please refer to Table 1 for the above performance test results.

[0072] Table 1. Performance test results of Examples 1-7 and Comparative Example 1 at 25°C In the preparation process of the electrode sheets of Examples 1-7 of the present application, small molecule quinone organic compounds and their derivatives are used as pore formers and added to the surface coating of the current collector. Part of the pore former in the coating dissolves in the electrolyte, so that pores are generated on the electrode sheet, which is beneficial to shorten the transmission path of lithium ions and improve the rate performance of the soft-pack battery, which is reflected in the higher ratio of 5 C capacity (Ah) to 1 C capacity (Ah) of the battery of Examples 1-7, and the lower DC impedance of the battery after cycling. It is also beneficial to increase the liquid retention of the electrode sheet, so that the capacity cycle retention rate of the soft-pack battery is improved.

[0073] The pore-forming agent design of Examples 1-7 of the present application can adapt to existing electrode sheet or battery preparation processes, without the need for additional modification of the pore-forming device, and also reduces the loss of active substances caused by etching-type pore-forming methods, thereby reducing the cost of electrode sheet pore-forming.

[0074] The electrode sheets of the present application, the embodiment and the comparative example 1 all have good capacity retention rates. The comparative example 1 is a conventional electrode sheet, which indicates that the addition of a pore-forming agent in the preparation process of the electrode sheet in the present application has substantially no negative effect on the stability of the resulting battery. In addition, compared with the embodiment of the present application, the ratio of the 5 C capacity (Ah) to the 1 C capacity (Ah) of the comparative example 1 is significantly lower, indicating that its rate performance is not as good as that of the embodiment of the present application, and the electrode sheet of the present application has improved rate performance.

[0075] The present application also uses the negative electrode sheet of Example 7 as the experimental group, and controls the residual amount of the pore-forming agent by the length of time the electrode sheet is soaked in an organic solvent. At the same time, the negative electrode sheet of Comparative Example 1 is used as the control group, and a step charge test is performed at -10 °C (the total time of the step charge process is 120 minutes), 0.33 C discharge, 0-80% SOC interval test, and after 50 cycles, the battery is transferred to room temperature (25 °C). After reaching thermal equilibrium, it is charged and discharged 3 times with a constant current of 2 C, and the average discharge capacity is taken. The average value is compared with the capacity data of 0.33 C constant capacity before the low-temperature lithium precipitation test to obtain the capacity retention rate. The experimental group has better rate performance and less lithium precipitation, thereby maintaining a higher capacity. The battery is disassembled after full charge to observe the lithium precipitation on the negative electrode surface. The lithium precipitation area occupies less than 5% of the entire negative electrode sheet area, which is judged as low, 5% to 10% as medium, and greater than 10% as high. Please refer to Table 2 for the measurement results.

[0076] Table 2. Capacity retention and lithium plating risk test results of experimental groups 1-5 and control group of this application It can be seen from the five experimental groups of Example 7 that in the preparation method of the embodiment of the present application, the porosity of the electrode sheet can also be controlled by controlling the immersion time in the organic solvent, which is beneficial to regulating the electrochemical performance of the obtained battery. The partially undissolved pore-forming agent in the electrode sheet coating can also be used in the positive electrode or the negative electrode according to its redox potential, as an active material, with high rate characteristics, and can reduce the risk of lithium precipitation by storing lithium ions that cannot be combined with the negative electrode material due to insufficient kinetics, thereby improving the safety of the battery cell.

[0077] Compared with the experimental group, the control group (Comparative Example 1) did not use small molecule quinone organic compounds and their derivatives as pore-forming agents. Its capacity retention rate at the set rate was lower, and the risk of lithium plating was higher, and the safety of the battery cell was lower.

[0078] The above implementation modes are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred implementation modes, a person skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. An electrode sheet, comprising a current collector and an active material layer disposed on at least one surface of the current collector, wherein the active material layer comprises an active substance, characterized in that: The active material layer includes a pore former, and the pore former includes a small molecule quinone organic compound and a derivative thereof, wherein the molecular weight of the small molecule quinone organic compound and the derivative thereof is 10 Da to 1000 Da.

2. The electrode sheet according to claim 1, characterized in that: The small molecule quinone organic compound and its derivatives include one or more of p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, 9,10-anthraquinone, 9,10-phenanthrenequinone and alizarin.

3. The electrode sheet according to claim 1, characterized in that: The mass content of the pore former in the active material layer is 0.1% to 20%.

4. The electrode sheet according to claim 1, characterized in that: The active material layer includes a first surface facing the current collector and a second surface opposite to the first surface, and the mass content of the pore former in the active material layer gradually increases along a direction from the first surface to the second surface.

5. The electrode sheet according to claim 1, characterized in that The thickness of the active material layer on any one surface of the current collector is 20 μm to 300 μm.

6. A method for preparing an electrode sheet, characterized in that: include: An active material layer is disposed on at least one surface of the current collector. The active material layer includes a pore former. The pore former includes a small molecule quinone organic compound and a derivative thereof.

7. The method for preparing an electrode sheet according to claim 6, characterized in that: Also includes: contacting the active material layer with an organic solvent to dissolve the pore former in the organic solvent; The active material layer is dried to obtain the electrode sheet.

8. The method for preparing an electrode sheet according to claim 7, characterized in that: The organic solvent includes one or more of electrolyte solvent, acetone, toluene, dichloromethane, chloroform, ethyl acetate, acetonitrile, methanol and petroleum ether.

9. A battery, characterized in that: The battery comprises the electrode sheet according to any one of claims 1 to 5, or comprises an electrode sheet prepared by the method for preparing the electrode sheet according to any one of claims 6 to 8.

10. An electrical device, characterized in that: The electric device comprises the battery as claimed in claim 9.

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