Positive electrode sheet and lithium ion battery comprising the same

Abstract

The present application provides a positive electrode plate for a lithium ion battery and a lithium ion battery comprising the positive electrode plate. The positive electrode plate comprises a current collector, a positive electrode active material layer and a specially designed lithium replenishing layer. The positive electrode plate of the present invention can effectively reduce the decomposition potential of lithium peroxide in an economical and simple manner, achieve an excellent lithium replenishing effect, and significantly inhibit the occurrence of side reactions, thereby significantly improving the service life and cycle performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and more specifically to a positive electrode sheet for a lithium-ion battery, and also to a battery, a battery module, a battery pack and an electrical device comprising the positive electrode sheet, and a method for manufacturing the lithium-ion battery. Background Art

[0002] With the development of related fields in recent years, rechargeable batteries (also known as secondary batteries) are increasingly used in daily consumer goods, new energy vehicles, large-scale energy storage, aerospace, ships, heavy machinery and other fields, and are even used as the main power and energy supply equipment in these fields. Among the various secondary batteries developed, lithium-ion secondary batteries have attracted widespread attention due to their excellent performance. However, lithium-ion secondary batteries themselves also have some technical problems that have not been solved so far. For example, one of the widely concerned topics is that lithium-ion batteries will consume a large amount of active lithium during the first charging process due to the formation of a solid electrolyte (SEI) film at the anode, and in the subsequent cycle process, the damage and repair of the SEI film due to graphite expansion will also further reduce the total amount of active lithium, which will cause the battery life to decay rapidly. In order to solve the above problems, the solution of the prior art is to pre-set lithium supplement materials in the battery, hoping to supplement the loss of active lithium in the above-mentioned first charge and discharge and cycle processes in this way, so as to achieve the purpose of extending the battery cycle life. However, to date, the practice of pre-setting lithium supplements has various insurmountable defects, such as the decomposition potential of the lithium supplement used is too high, too many side reactions, and a large amount of byproduct gas is generated, resulting in battery bulging, etc., which leads to significant difficulties and risks in the production and safety of lithium-ion batteries. In addition, the operation of adding additional components containing lithium supplements will further complicate the battery manufacturing process, resulting in a significant increase in production costs. The field is also in urgent need of developing a simple and economical lithium supplement technology.

[0003] Therefore, there is an urgent need for an improved technical solution in this field to effectively reduce the decomposition potential of lithium peroxide in an economical and simple manner, achieve excellent lithium replenishment effect, and significantly inhibit the occurrence of side reactions and the accumulation of harmful byproduct gases, significantly extend the service life of the battery and improve the cycle performance of the battery. Summary of the invention

[0004] The inventors of the present invention have conducted a lot of in-depth research and unexpectedly developed a unique technical solution, which solves the above-mentioned technical problems that have not been able to be solved in the prior art through a specially designed lithium replenishing layer.

[0005] The first aspect of the present application provides a positive electrode sheet for a lithium ion battery, the positive electrode sheet comprising:

[0006] i) current collector;

[0007] ii) a positive electrode active material layer located on at least one surface of the current collector, the positive electrode active material layer comprising lithium iron phosphate or a positive electrode active material represented by formula I:

[0008] LiNi x Co y A z O2 Formula I

[0009] wherein A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1; and

[0010] iii) A lithium replenishing layer located above the positive electrode active material layer, the lithium replenishing layer comprising: lithium peroxide and a transition metal oxide selected from at least one of the following elements: iron, cobalt, nickel, manganese, copper, molybdenum, titanium, vanadium, chromium, lead, scandium, yttrium, palladium, platinum and silver. The present application adopts a specially designed lithium replenishing layer in the positive electrode plate in a simple and economical manner, achieving a significant decrease in the decomposition potential of the lithium peroxide lithium replenisher, being able to achieve an excellent lithium replenishing effect under mild conditions, and effectively inhibiting the occurrence of side reactions, which is specifically manifested in an improvement in the capacity retention rate of the lithium battery. The lithium replenishing layer may further include a binder to promote the formation of each component into a layer structure and maintain close bonding between the components. The lithium replenishing layer may also further include a conductive agent so that the lithium replenishing layer has the desired conductivity.

[0011] According to any aspect of the present application, the transition metal oxide is selected from: NiO, Co3O4, MnO2, Fe2O3, CuO, and any combination thereof. By selecting the types of the above transition metal oxides, the present application further reduces the decomposition potential of the lithium peroxide supplement and helps to inhibit side reactions.

[0012] According to any aspect of the present application, there is no intermediate layer between the lithium replenishing layer and the positive electrode active material layer. Through this special design, the present application promotes the reduction of the decomposition potential of lithium peroxide and the improvement of the lithium replenishing effect in a simple and economical way. According to any aspect of the present application, one or more intermediate layers, such as a conductive layer, an adhesive layer, an adhesion promoting layer, a protective layer, a catalytic layer, etc., are provided between the lithium replenishing layer and the positive electrode active material layer, and the effects such as increasing conductivity and adhesion are achieved by adding the above intermediate layers.

[0013] According to any aspect of the present application, the weight ratio of the lithium peroxide to the transition metal oxide is 7:1 to 3:1. The selection of the above preferred ratio can achieve a further improved lithium supplementation effect, which is specifically manifested in an improvement in the capacity retention rate of the lithium battery.

[0014] According to any aspect of the present application, based on the total weight of the lithium supplement layer, the content of the lithium peroxide is 50-70% by weight, the content of the transition metal oxide is 5-30% by weight, the content of the binder is 5-20% by weight, and the content of the conductive agent is 5-20% by weight. By selecting the above component ratios, the lithium supplement effect is further improved, which is specifically manifested in the improvement of the lithium battery capacity retention rate, and the overall conductivity and mechanical strength of the positive electrode sheet are further optimized.

[0015] According to any aspect of the present application, the thickness of the lithium replenishing layer is 1-10 microns. According to any aspect of the present application, the coating weight of the lithium replenishing layer is 5-15 mg / 1540.25 cm 2 Through the design of the coating thickness and coating weight, the reduction of the decomposition voltage of lithium peroxide, the further optimization of the lithium ion migration effect and the escape of gas are achieved.

[0016] The second aspect of the present application provides a lithium-ion battery, comprising a negative electrode plate, an electrolyte, and a positive electrode plate for a lithium-ion battery as described in any one of the above aspects. The lithium-ion battery achieves an excellent lithium supplement effect due to the use of the positive electrode plate of the present invention, which is specifically manifested in a reduction in decomposition voltage, a reduction in side reactions and gas production, and an improvement in the lithium battery capacity retention rate.

[0017] A third aspect of the present invention provides a method for manufacturing the lithium ion battery described in any one of the above aspects, the method comprising:

[0018] A) providing a current collector;

[0019] B) forming a positive electrode active material layer on at least one surface of the current collector, wherein the positive electrode active material layer comprises lithium iron phosphate or a positive electrode active material represented by Formula I:

[0020] LiNi x Co y A z O2 Formula I

[0021] wherein A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1;

[0022] C) mixing lithium peroxide, a transition metal oxide, a solvent, and optionally a binder and optionally a conductive agent to form a slurry, wherein the transition metal oxide comprises an oxide of at least one element selected from the group consisting of iron, cobalt, nickel, manganese, copper, molybdenum, titanium, vanadium, chromium, lead, scandium, yttrium, palladium, platinum and silver;

[0023] D) applying the slurry onto the positive electrode active material layer to form a lithium supplement layer, thereby preparing a positive electrode sheet; and

[0024] E) The positive electrode sheet and the negative electrode sheet are placed together in a battery housing, and electrolyte is injected into the battery housing to perform formation and aging, wherein the charging current after the formation and full charging is 0.02-0.05C. The method achieves an excellent lithium supplementation effect due to the use of the positive electrode sheet of the present invention, which is specifically manifested in the reduction of decomposition voltage, reduction of side reactions and gas production, and improvement of lithium battery capacity retention rate. In addition, the specially designed charging current in the method can further reduce polarization and further reduce the decomposition voltage of lithium peroxide.

[0025] The third aspect of the present invention provides a battery module, comprising the lithium-ion battery described in any of the above aspects. The battery module achieves excellent lithium replenishment effect due to the use of the positive electrode plate of the present invention, which is specifically manifested in reduced decomposition voltage, reduced side reactions and gas production, and improved lithium battery capacity retention rate.

[0026] The fourth aspect of the present invention provides a battery pack, comprising the battery module described in any of the above aspects. The battery pack achieves excellent lithium replenishment effect due to the use of the positive electrode plate of the present invention, which is specifically manifested in reduced decomposition voltage, reduced side reactions and gas production, and improved lithium battery capacity retention rate.

[0027] The fifth aspect of the present invention provides an electric device, comprising at least one of the lithium-ion battery, battery module and battery pack described in any one of the above aspects. The electric device achieves excellent lithium replenishment effect due to the use of the positive electrode plate of the present invention, which is specifically manifested in reduced decomposition voltage, reduced side reactions and gas production, and improved lithium battery capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a cross-sectional view of a positive electrode sheet according to one embodiment of the present invention, wherein a positive electrode active material layer and a lithium supplement layer are provided on one surface of a current collector.

[0029] Figure 2 is a cross-sectional view of a positive electrode sheet according to another embodiment of the present invention, wherein a positive electrode active material layer and a lithium supplement layer are respectively disposed on both surfaces of a current collector.

[0030] Figure 3 It is a schematic diagram of an embodiment of the lithium-ion battery of the present application.

[0031] Figure 4 yes Figure 3 Exploded view of a lithium-ion battery shown.

[0032] Figure 5It is a schematic diagram of an embodiment of the battery module of the present application.

[0033] Figure 6 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0034] Figure 7 yes Figure 6 Exploded view of the battery pack shown.

[0035] Figure 8 It is a schematic diagram of an embodiment of an electric device using the lithium-ion battery of the present application as a power source.

[0036] In the specific implementation section below, the design details of the positive electrode plate designed in the present application, the lithium-ion battery including the positive electrode plate, the battery module, the battery pack and the electrical device are described. DETAILED DESCRIPTION

[0037] "Scope" disclosed herein is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a scope. For example, if a scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0038] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0039] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0040] In this application, unless otherwise specified, the terms "comprising" and "including" mentioned herein may be open-ended or closed-ended. For example, the terms "comprising" and "including" may mean that other components not listed may also be included or may only include or contain the listed components.

[0041] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and "several" in "one or several" means two or more.

[0042] In the description herein, unless otherwise specified, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0043] In this application, the terms "lithium-ion battery" and "lithium-ion secondary battery" are used interchangeably to refer to lithium-ion batteries that can be repeatedly charged and discharged. Throughout this application, the terms "negative electrode" and "anode" are used interchangeably to refer to the same electrode in a battery; the terms "positive electrode" and "cathode" are used interchangeably to refer to the same electrode in a battery.

[0044] According to one embodiment of the present invention, a positive electrode sheet for a lithium-ion battery is developed, the positive electrode sheet comprising:

[0045] i) current collector;

[0046] ii) a positive electrode active material layer located on at least one surface of the current collector, the positive electrode active material layer comprising lithium iron phosphate or a positive electrode active material represented by formula I:

[0047] LiNi x Co y A z O2 Formula I

[0048] wherein A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1; and

[0049] iii) a lithium replenishing layer located on the positive electrode active material layer, the lithium replenishing layer comprising: lithium peroxide and at least one transition metal oxide selected from the following elements: iron, cobalt, nickel, manganese, copper, molybdenum, titanium, vanadium, chromium, lead, scandium, yttrium, palladium, platinum and silver. According to one embodiment of the present invention, the lithium replenishing layer may further comprise a binder or a conductive agent, or both, wherein the binder is used to promote the formation of the lithium replenishing layer and firmly combine the various components in the lithium replenishing layer, and the conductive agent is used to make the lithium replenishing layer have the desired conductive properties.

[0050] According to one embodiment of the present application, the current collector is a metal foil, a metal alloy foil, a polymer sheet with a metal coating, or a polymer sheet with a metal alloy coating; wherein the metal in the metal foil and the metal coating is selected from copper, silver, iron, titanium, nickel, and aluminum; the metal alloy in the metal alloy foil and the metal alloy coating is selected from copper alloy, nickel alloy, titanium alloy, silver alloy, iron alloy, and aluminum alloy; the polymer sheet is selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, and mixtures or copolymers thereof.

[0051] According to one embodiment of the present application, the positive electrode active material layer contains lithium iron phosphate, a positive electrode active material represented by formula (I) or a combination thereof. For the positive electrode active material represented by formula (I), the value of x can be within the numerical range obtained by taking any two of the following numerical values ​​as the upper limit and the lower limit respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4 , 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99; the value of y can be within the range of values ​​obtained by taking any two of the following values ​​as the upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.08 5, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99; the value of z can be within the range of values ​​obtained by taking any two of the following values ​​as the upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99; and the values ​​of x, y and z satisfy x+y+z=1. According to another embodiment of the present application, the positive electrode active material layer contains only lithium iron phosphate as the positive electrode active material, that is, does not contain positive electrode active materials other than lithium iron phosphate.

[0052] According to another embodiment of the present application, the positive electrode active material layer may also optionally include one or more of a conductive agent and a binder, examples of the conductive agent include superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene graphite, mesophase carbon microspheres, soft carbon, hard carbon, carbon fiber, graphene, Super P, furnace black, vapor grown carbon fiber (VGCF) and carbon nanofibers. One or more examples of the binder include one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, polytrifluorochloroethylene, styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, sodium alginate, polyurethane, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, sodium polycarboxymethyl cellulose, acrylamide, polyvinyl alcohol, and carboxymethyl chitosan. According to one embodiment of the present invention, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material is 10 to 99.9% by weight, for example, 20 to 99% by weight, or 30 to 98% by weight, or 40 to 97% by weight, or 50 to 80% by weight, or 55 to 70% by weight, or 60 to 97% by weight, or within the numerical range composed of any two of the above end values. According to one embodiment of the present invention, based on the total weight of the positive electrode active material layer, the content of the binder is 0.01 to 50% by weight, for example, 0.02 to 45% by weight, or 0.05 to 40% by weight, or 0.1 to 35% by weight, or 0.5 to 30% by weight, or 0.75 to 20% by weight, or 1 to 15% by weight, or 1.25 to 12.5% ​​by weight, or 1.5 to 10% by weight, or 2 to 7% by weight, or 2 to 6% by weight, or within the numerical range composed of any two of the above end values. According to one embodiment of the present invention, based on the total weight of the positive electrode active material layer, the content of the conductive agent is 0.01 to 80% by weight, for example, 0.1 to 70% by weight, or 1 to 60% by weight, or 10 to 50% by weight, or 20 to 40% by weight, or 25 to 35% by weight, or 1 to 5% by weight, or within the numerical range composed of any two of the above end values. The positive electrode active material layer on the current collector can be manufactured by mixing the above-mentioned positive electrode active material, conductive agent, adhesive and other optional additives with a solvent or dispersant, such as N-methylpyrrolidone (NMP) or deionized water to form a slurry, coating the slurry on the current collector, and then drying to form a positive electrode active material layer. Examples of other additives optionally included in the positive electrode active material layer are thickeners (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.The thickness of the positive electrode active material layer formed after drying can be 1-500 microns. For example, its thickness can be within the numerical range obtained by combining any two of the following endpoints: 1 micron, 3 microns, 5 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 35 microns, 40 microns, 45 microns, 50 microns, 55 microns, 60 microns, 65 microns, 70 microns, 75 microns, 80 microns, 85 microns, 90 microns, 95 microns, 100 microns, 105 microns, 110 microns, 115 microns, 120 microns, 125 microns, 130 microns, 135 microns, 140 microns, 145 microns, 150 microns, 155 microns , 160 microns, 165 microns, 170 microns, 175 microns, 180 microns, 185 microns, 190 microns, 195 microns, 200 microns, 205 microns, 210 microns, 215 microns, 220 microns, 225 microns, 230 microns, 235 microns, 240 microns, 245 microns, 250 microns, 255 microns, 260 microns, 270 microns, 275 microns, 280 microns, 285 microns, 290 microns, 295 microns, 300 microns, 305 microns, 310 microns, 315 microns, 320 microns, 325 microns, 330 microns, 335 microns, 340 microns, 400 microns, 450 microns, 500 microns

[0053] According to one embodiment of the present application, the lithium replenishing layer located on the positive electrode active material layer comprises: lithium peroxide and a transition metal oxide selected from at least one of the following elements: iron, cobalt, nickel, manganese, copper, molybdenum, titanium, vanadium, chromium, lead, scandium, yttrium, palladium, platinum and silver. According to one embodiment of the present application, the lithium replenishing layer further comprises a binder, a conductive agent, or a combination thereof. Examples of the binder include one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, polytrifluorochloroethylene, styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, sodium alginate, polyurethane, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, sodium polycarboxymethyl cellulose, acrylamide, polyvinyl alcohol, and carboxymethyl chitosan. Examples of the conductive agent include one or more of the following: superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene graphite, mesophase carbon microspheres, soft carbon, hard carbon, carbon fiber, graphene, Super P, furnace black, vapor-grown carbon fiber (VGCF) and carbon nanofibers. The lithium peroxide is preferably in the form of particles, and its particle size can be 1-10 microns, such as 2-9 microns, or 3-8 microns, or 4-7 microns, or 5-6 microns, or the particle size is within the numerical range obtained by combining any two of the above end values. Preferably, the particle size of the lithium peroxide is less than or equal to the thickness of the positive electrode active material layer, and further preferably, the particle size of the lithium peroxide is less than the thickness of the positive electrode active material layer. The transition metal oxide preferably comprises one or more of the following: NiO, Co3O4, MnO2, Fe2O3 and CuO. According to another embodiment of the present invention, the particle size of the transition metal oxide can be 0.1-10 microns, such as 1-9 microns, or 2-8 microns, or 3-7 microns, or 4-6 microns, or within the numerical range composed of any two of the above end values. Preferably, the particle size of the transition metal oxide particles is less than or equal to the thickness of the positive electrode active material layer, and further preferably, the particle size of the transition metal oxide particles is less than the thickness of the positive electrode active material layer. According to one embodiment of the present invention, based on the total weight of the lithium supplementing layer, the content of the lithium peroxide is 40-90% by weight, such as 50-85% by weight, or 55-82% by weight, or 60-80% by weight, or 65-75% by weight, or 68-70% by weight, or within the numerical range composed of any two of the above end values. According to one embodiment of the present invention, based on the total weight of the lithium supplementing layer, the content of the transition metal oxide is 1-40% by weight, such as 2-35% by weight, or 5-30% by weight, or 7-25% by weight, or 8-20% by weight, or 9-15% by weight, or 10-12% by weight, or within the numerical range composed of any two of the above end values.According to one embodiment of the present invention, based on the total weight of the lithium replenishing layer, the content of the binder is 1-40% by weight, such as 2-35% by weight, or 5-30% by weight, or 7-25% by weight, or 8-20% by weight, or 9-15% by weight, or 10-12% by weight, or within the numerical range composed of any two of the above end values. According to one embodiment of the present invention, based on the total weight of the lithium replenishing layer, the content of the conductive agent is 1-40% by weight, such as 2-35% by weight, or 5-30% by weight, or 7-25% by weight, or 8-20% by weight, or 9-15% by weight, or 10-12% by weight, or within the numerical range composed of any two of the above end values. The lithium replenishing layer on the positive electrode active material layer can be manufactured in the following manner: the above-mentioned lithium peroxide, transition metal oxide, optional conductive agent and / or binder and other optional auxiliary agents are mixed with a solvent or dispersant, such as N-methylpyrrolidone (NMP) or deionized water, to form a slurry, the slurry is coated on the positive electrode active material layer, and then dried and cold pressed to form the lithium replenishing layer. The solid content of the formed slurry can be 40-80% by weight, such as 50-70% by weight, or 55-65% by weight. The slurry can be applied by conventional coating techniques, such as curtain coating, blade coating, cast coating, gravure roller coating, etc., and the coating weight can be controlled at 5-15 mg / 1540.25 cm. 2 , for example 6-14mg / 1540.25cm 2 , or 7-13mg / 1540.25cm 2 , or 8-12mg / 1540.25cm 2 , or 9-11mg / 1540.25cm 2 , or 9-10mg / 1540.25cm 2 The coating speed can be 5-45 m / min, for example 8-40 m / min, or 10-30 m / min, or 15-25 m / min, or 18-22 m / min; by controlling the amount of slurry applied and the coating process parameters (such as the roller pressure used in roller coating), the thickness of the lithium replenishing layer obtained after final drying is controlled to be 1-10 μm, or 2-9 μm, or 3-8 μm, or 4-7 μm, or 5-6 μm.

[0054] Figure 1 A positive electrode sheet formed according to one embodiment of the present invention is shown, wherein a positive electrode active material layer and a lithium supplement layer are sequentially formed on one surface of a current collector. Figure 2A positive electrode sheet formed according to another embodiment of the present invention is shown, wherein a positive electrode active material layer and a lithium precipitation inhibition layer are formed on two surfaces of a central current collector, respectively. According to one embodiment of the present invention, the lithium supplement layer completely covers the entire outer surface of the positive electrode active material layer (the surface of the positive electrode active material layer opposite to the current collector).

[0055] According to one embodiment of the present invention, the lithium replenishing layer is in direct contact with the positive electrode active material layer, and no other layer is arranged between the two. According to another embodiment of the present application, one or more additional intermediate layers are optionally arranged between the lithium replenishing layer and the positive electrode active material layer, for example, the intermediate layer may be a conductive primer layer (which may be composed of a binder and a conductive agent), or may contain other auxiliary agents known in the art, or may be another positive electrode active material layer containing the same or different positive electrode active materials. According to one embodiment of the present invention, there is no intermediate layer containing the transition metal oxide described above between the lithium replenishing layer and the positive electrode active material layer, that is, in the case where there is an intermediate layer between the lithium replenishing layer and the positive electrode active material layer, the intermediate layer does not contain the transition metal oxide described above.

[0056] The positive electrode sheet described in the above embodiments of the present application can be used in a lithium-ion battery. In one embodiment of the present application, the lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, etc. During the battery charging and discharging process, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.

[0057] The lithium-ion battery of the present application includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, a binder, a conductive agent and other optional additives. In one embodiment of the present application, examples of the negative electrode active material include one or more of the following: natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. The silicon-based material can be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composites. The tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. As an example, the conductive agent may include one or more of superconducting carbon, carbon black (such as acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene and carbon nanofibers; the binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). Other optional additives include thickeners (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0058] According to one embodiment of the present invention, the negative electrode plate can be manufactured in the following manner: the negative electrode active material described above and a binder, a conductive agent and other optional additives are dispersed in a solvent and stirred evenly to form a slurry with a certain solid content, wherein the solvent may be N-methylpyrrolidone (NMP) or deionized water. In addition, based on the total weight of the prepared slurry, the solid content of the slurry may be 30-80% by weight, for example, 50-70% by weight, or 55-65% by weight; the slurry is then applied to a negative electrode collector, and after drying and optionally cold pressing, a negative electrode plate is formed, wherein the negative electrode collector may be a metal foil or a composite current collector, for example, the metal foil may be a copper foil, a silver foil, an iron foil, or a foil composed of an alloy of the above metals. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. It can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base layer (such as a base layer made of materials such as polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and their copolymers).

[0059] In addition, in the battery of the present application, the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode active material layer. For example, in some embodiments, the negative electrode plate of the present application may also include a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate of the present application may also include a covering protective layer covering the surface of the negative electrode active material layer.

[0060] The electrolyte plays the role of conducting ions between the positive electrode plate and the negative electrode plate. The electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte). In some embodiments, the electrolyte adopts an electrolyte. The electrolyte comprises an electrolyte salt and a solvent. In some embodiments, the electrolyte salt can be selected from LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bisfluorosulfonyl imide), LiTFSI (lithium bistrifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoro oxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluoro dioxalate phosphate) and LiTFOP (lithium tetrafluoro oxalate phosphate) One or more. In one embodiment of the present application, the solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE). In one embodiment of the present application, based on the total weight of the electrolyte, the content of the solvent is 60-99% by weight, such as 65-95% by weight, or 70-90% by weight, or 75-89% by weight, or 80-85% by weight, or within the numerical range obtained by combining any one of the above upper limits and any one of the lower limits. In one embodiment of the present application, based on the total weight of the electrolyte, the content of the electrolyte is 1-40% by weight, such as 5-35% by weight, or 10-30% by weight, or 11-25% by weight, or 15-20% by weight, or within the numerical range obtained by combining any one of the above upper limits and any one of the lower limits.

[0061] In one embodiment of the present application, the electrolyte may optionally contain additives. For example, the additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, additives that improve battery low temperature performance, etc.

[0062] In one embodiment of the present application, the battery further comprises a separator, which separates the positive electrode side of the battery from the negative electrode side, and provides selective permeation or blocking for substances of different types, sizes and charges in the system. For example, the separator can insulate electrons, physically isolate the positive and negative active substances of the battery, prevent internal short circuits and form an electric field in a certain direction, and at the same time enable ions in the battery to pass through the separator and move between the positive and negative electrodes. In one embodiment of the present application, the material used to prepare the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0063] In one embodiment of the present application, the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly / bare cell by a winding process or a lamination process.

[0064] In one embodiment of the present application, the lithium-ion battery may include an outer packaging, also referred to as a shell, which may be used to encapsulate the electrode assembly and the electrolyte. In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. In other embodiments, the outer packaging of the battery may be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0065] The shape of the battery of the present application can be cylindrical, square or any other shape. Figure 3 The battery 5 is a square structure as an example. Figure 4 Shows Figure 3 The exploded view of the battery 5 is shown in FIG. 5 . The outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate. The bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity. The cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly is encapsulated in the receiving cavity, and the electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery 5 can be one or more.

[0066] According to one embodiment of the present invention, after the battery is assembled and the electrolyte is injected therein, a formation operation is performed on it so that a solid electrolyte interface layer (SEI film) is formed on the negative electrode surface, thereby obtaining a battery that meets product requirements. According to a preferred embodiment of the present invention, the above-mentioned formation process uses a current of 0.15-0.45C to fully charge to a full charge voltage of 3.2-4.3V, and then uses a small current charging of 0.02-0.05C to complete the formation, so as to reduce polarization and further reduce the decomposition voltage. According to one embodiment of the present invention, a current of 0.15-0.45C, or 0.20-0.40C, or 0.25-0.38C, or 0.30-0.35C, or 0.32-0.33C is used for full charging to 3.3-4.2V, or 3.4-4.0V, or 3.5-3.8V, or 3.6-3.7V, or 3.65V. The current intensity used for low-current charging is 0.02-0.05C, or 0.02-0.04C, or 0.02-0.03C.

[0067] In one embodiment of the present application, several batteries may be assembled together to form a battery module, wherein the battery module includes two or more batteries, and the specific number depends on the application of the battery module and the parameters of a single battery module.

[0068] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the multiple batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The multiple batteries 5 may further be fixed by fasteners. Optionally, the battery module 4 may further include a housing having a storage space, and the multiple batteries 5 are stored in the storage space.

[0069] In one embodiment of the present application, two or more of the above-mentioned battery modules can be assembled into a battery pack, and the number of battery modules contained in the battery pack depends on the application of the battery pack and the parameters of the individual battery modules. The battery pack can include a battery box and a plurality of battery modules arranged in the battery box, and the battery box includes an upper box body and a lower box body, and the upper box body can cover the lower box body and match well with it to form a closed space for accommodating the battery module. Two or more battery modules can be arranged in the battery box in a desired manner.

[0070] Figure 6 and Figure 7 1 is a battery pack 1 as an example. Figure 6 and Figure 7The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0071] Electrical Devices

[0072] In one embodiment of the present application, the electrical device of the present application includes at least one of the battery, battery module, or battery pack of the present application, and the battery, battery module, or battery pack can be used as a power source of the electrical device, and can also be used as an energy storage unit of the electrical device. The electrical device includes but is not limited to mobile digital devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0073] Figure 8 The device is used as an example. The device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the device for high power and high energy density, a battery pack or a battery module can be used.

[0074] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery may be used as a power source.

[0075] In the following, the influence of the positive electrode plate manufactured according to the implementation mode of the present application on the performance of the electrical device is characterized based on specific examples, but it should be pointed out in particular that the scope of protection of the present application is limited by the claims and is not limited to the above specific implementation modes.

[0076] Example

[0077] Various raw materials described in Table 1 below are used in the examples. Unless otherwise specified, the raw materials used in the examples of the present application are all commercially available products.

[0078] raw material Parameter Description Lithium Iron Phosphate The positive electrode active material, with a particle size of 1 μm, was purchased from Defang Nanotechnology Co., Ltd. Lithium Peroxide Lithium supplement, particle size 4 microns Super P Conductive agent graphite Negative electrode active material, purchased from Kaijin New Energy Technology Co., Ltd. PVDF Binder, polyvinylidene fluoride SBR Binder, styrene butadiene rubber CMC Thickener, carboxymethyl cellulose NMP Solvent, N-methylpyrrolidone, analytical grade NiO Transition metal oxides, particle size 5 microns <![CDATA[Co3O4]]> Transition metal oxides, particle size 5 microns <![CDATA[MnO2]]> Transition metal oxides, particle size 5 microns <![CDATA[Fe2O3]]> Transition metal oxides, particle size 5 microns CuO Transition metal oxides, particle size 5 microns Diaphragm Polyethylene diaphragm, 7 micron thick

[0079] The particle size of the transition metal oxide used in the present invention is measured by a laser scattering particle size analyzer.

[0080] Example 1

[0081] In this Example 1, the positive electrode sheet was synthesized by using the following steps.

[0082] Step 1: Fabrication of positive electrode active material layer.

[0083] In this step, lithium iron phosphate, Super P, PVDF and NMP as positive electrode active materials are uniformly mixed in a ratio of 97:1:2:56 to prepare a slurry, which is coated on a 60 μm thick aluminum foil current collector using a coating device. After drying and cold pressing, a 140 μm thick positive electrode active material layer is formed on the current collector.

[0084] Step 2: Fabrication of lithium replenishing layer.

[0085] In this step, lithium peroxide particles with a particle size of 4 microns, NiO particles with a particle size of 5 microns, PVDF, and Super P are mixed in a weight ratio of 7:1:1:1 and uniformly dispersed in an NMP solvent to prepare a slurry. The slurry is coated on the positive electrode active material layer obtained in step 1 using a gravure coating device to form a lithium supplement layer with a thickness of 6 microns after drying and cold pressing.

[0086] Step 3: Manufacturing of negative electrode sheet

[0087] In this step, graphite, Super P, styrene-butadiene rubber, CMC, and deionized water are uniformly mixed in a ratio of 96:1:2:1:87 to prepare a slurry, which is coated on a 6-micron thick copper foil current collector using a coating device, and then the same slurry is coated on the other side of the current collector and dried after drying. After cold pressing, a negative electrode material layer with a thickness of 0.12 mm is formed on both sides of the current collector, thereby obtaining a negative electrode sheet.

[0088] Step 4: Battery Manufacturing

[0089] In this step, the positive electrode sheet, the separator, the negative electrode sheet, the separator, and the positive electrode sheet are stacked in order (where the separator is polyethylene and has a thickness of 7 microns) to form a laminated structure. The laminated structure is placed in an aluminum-plastic film, and an electrolyte is injected into it for packaging. The electrolyte is a solution of lithium hexafluorophosphate electrolyte in a solvent mixture of EC:DMC:EMC=1:1:1 (V:V) with a concentration of 1 mol / L. Then, the battery is formed and aged, wherein the formation process is performed according to the following process: 0.33C is fully charged to 3.65V, and then charged to 4.5V with a small current of 0.05C. In this process, lithium peroxide is decomposed to release active lithium, thereby achieving the purpose of lithium supplementation.

[0090] Example 2

[0091] In this Example 2, a battery was synthesized using the same steps as in Example 1, with the only difference being that in the process of manufacturing the positive electrode sheet, the same weight of Co3O4 was used instead of NiO.

[0092] Example 3

[0093] In this Example 3, a battery was synthesized using the same steps as in Example 1, with the only difference being that in the process of manufacturing the positive electrode sheet, the same weight of MnO2 was used instead of NiO.

[0094] Example 4

[0095] In this Example 4, a battery was synthesized using the same steps as in Example 1, with the only difference being that in the process of manufacturing the positive electrode sheet, the same weight of Fe2O3 was used instead of NiO.

[0096] Example 5

[0097] In this Example 5, a battery was synthesized using the same steps as in Example 1, with the only difference being that in the process of manufacturing the positive electrode sheet, the same weight of CuO was used instead of NiO.

[0098] Example 6

[0099] In this Example 6, a battery was synthesized using the same steps as in Example 1, with the only difference being that, in the process of manufacturing the positive electrode sheet, the weight ratio of lithium peroxide particles, NiO particles, PVDF and Super P was 3:1:1:1.

[0100] Example 7

[0101] In this Example 6, a battery was synthesized using the same steps as in Example 1, with the only difference being that, in the process of manufacturing the positive electrode sheet, the weight ratio of lithium peroxide particles, NiO particles, PVDF and Super P was 5:1:2:2.

[0102] Example 8

[0103] In this Example 8, a battery was synthesized using the same steps as in Example 1, with the only difference being that, during the manufacture of the positive electrode sheet, the weight ratio of lithium peroxide particles, NiO particles, PVDF and Super P was 5:1:1:1.

[0104] Example 9

[0105] In this Example 9, a battery was synthesized using the same steps as in Example 1, with the only difference being that, in the process of manufacturing the positive electrode plate, the amount of slurry coated on the positive electrode active material layer was increased, and a lithium replenishing layer with a thickness of 8 microns was formed after drying and cold pressing.

[0106] Example 10

[0107] In this embodiment 10, the same steps as in embodiment 1 are used to synthesize a battery, except that in step 4 of manufacturing the battery, the formation process adopts the following process steps: fully charging at 0.33C to 3.65V, and then charging at a low current of 0.02C to 4.5V

[0108] Comparative Example 1

[0109] Step 1: In this step 1 of Comparative Example 1, a positive electrode active material layer was formed on a current collector in the same manner as step 1 of Example 1.

[0110] Step 2: Preparation of lithium replenishing layer.

[0111] In this step, lithium peroxide particles with a particle size of 4 microns, PVDF and Super P are mixed in a weight ratio of 8:1:1 and uniformly dispersed in an NMP solvent to prepare a slurry. The slurry is coated on the positive electrode active material layer obtained in step 1 using a gravure coating device to form a lithium supplement layer with a thickness of 6 microns after drying and cold pressing.

[0112] Step 3: The negative electrode sheet is manufactured in the same manner as step 3 of Example 1.

[0113] Step 4: A battery was manufactured in the same manner as Step 4 of Example 1.

[0114] Comparative Example 2

[0115] In this comparative example 2, the battery is manufactured by the same steps as in Example 1, except that step 2 in Example 1 is omitted, that is, the positive electrode sheet used has only a positive electrode active material layer but no lithium replenishing layer.

[0116] Experimental example: Testing of battery cycle performance

[0117] In this experimental example, the performance of the batteries prepared in the above invention examples 1-10 and comparative examples 1-2 was characterized. Specifically, the battery was tested for cycle performance by a blue-electric test system, the working environment was set to 25 degrees Celsius, the battery was charged and discharged, and the battery capacity and voltage were recorded at intervals of 30 seconds. The specific process steps of the test are as follows:

[0118] First, discharge to 2.5V with a current of 0.5C, then charge to 3.65V with 0.33C, charge to 3.65V with a constant voltage of 0.05C, and then discharge to 2.5V with 0.33C. Record the discharge capacity as C0, and then discharge to 2.5V with a small current of 0.04C for depolarization. The next cycle test is: first charge at a constant current of 1C for 48 minutes, then charge to 3.65V with 0.33C, then charge to a small current of 0.05C with a constant voltage, and then discharge to 2.5V with 1C. Cycle the above steps for 600 times, and the last discharge capacity is recorded as C600. Finally, discharge to 2.5V with a small current of 0.04C. The capacity retention rate of 600 cycles is C600 / C0. In the above process, the decomposition capacity of the battery, the average decomposition platform of lithium peroxide, and the capacity retention rate after 600 cycles are recorded. The results are summarized in the following Table 1:

[0119] Table 1: Characterization results of the batteries of Examples 1-5 and Comparative Examples 1-2 of the present application

[0120]

[0121]

[0122] From the experimental results shown in Table 1, it can be seen that compared with the comparative example, embodiments 1-10 of the present invention can all achieve lower decomposition current, lower lithium peroxide decomposition potential, and the battery capacity retention rate after 600 cycles is significantly improved. This shows that the battery of the embodiment of the present invention has a significantly extended cycle life, reduces the decomposition potential of lithium peroxide, suppresses the occurrence of side reactions, and makes the battery have more excellent cycle performance. For example, compared with other embodiments, embodiment 2 using Co3O4 achieves the lowest lithium peroxide decomposition potential and higher battery capacity retention rate, thus proving that the technical solution using Co3O4 can achieve a solution that is significantly far superior to that using other transition metal oxides. In addition, embodiments 6-10 prove that by adjusting the process parameters, further improvements can be achieved in terms of lithium peroxide decomposition potential and battery capacity retention rate.

Claims

1. A positive electrode sheet for a lithium ion battery, the positive electrode sheet comprising: i) current collector; ii) a positive electrode active material layer located on at least one surface of the current collector, the positive electrode active material layer comprising lithium iron phosphate or a positive electrode active material represented by formula I: LiNi x Co y A z O2 of formula I wherein A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1; and iii) a lithium replenishing layer located on the positive electrode active material layer, the lithium replenishing layer comprising: lithium peroxide and at least one transition metal oxide selected from the group consisting of iron, cobalt, nickel, manganese, copper, molybdenum, titanium, vanadium, chromium, lead, scandium, yttrium, palladium, platinum and silver.

2. The positive electrode sheet for lithium-ion battery according to claim 1, characterized in that: The lithium replenishing layer further comprises a binder and / or a conductive agent.

3. The positive electrode sheet for lithium-ion battery according to claim 1, characterized in that: The transition metal oxide is selected from the group consisting of: NiO, Co3O4, MnO2, Fe2O3, CuO, and any combination thereof.

4. The positive electrode sheet for lithium-ion battery according to any one of claims 1 to 3, characterized in that: There is no intermediate layer between the lithium replenishing layer and the positive electrode active material layer.

5. The positive electrode sheet for lithium ion battery according to any one of claims 1 to 3, characterized in that: The weight ratio of the lithium peroxide to the transition metal oxide is 7:1 to 3:

1.

6. The positive electrode sheet for lithium ion battery according to any one of claims 1 to 3, characterized in that: Based on the total weight of the lithium supplementing layer, the content of the lithium peroxide is 50-85% by weight.

7. The positive electrode sheet for lithium-ion battery according to claim 6, characterized in that: Based on the total weight of the lithium supplement layer, the content of the lithium peroxide is 50-70% by weight.

8. The positive electrode sheet for a lithium ion battery according to any one of claims 1 to 3, characterized in that: Based on the total weight of the lithium supplementing layer, the content of the transition metal oxide is 5-30 weight %.

9. The positive electrode sheet for lithium-ion battery according to claim 2, characterized in that: Based on the total weight of the lithium replenishing layer, the content of the binder is 5-20 weight %.

10. The positive electrode sheet for lithium-ion battery according to claim 9, characterized in that: Based on the total weight of the lithium supplementing layer, the content of the binder is 8-20 weight %.

11. The positive electrode sheet for lithium-ion battery according to claim 2, characterized in that: Based on the total weight of the lithium supplementing layer, the content of the conductive agent is 5-20 weight %.

12. The positive electrode sheet for lithium-ion battery according to claim 11, characterized in that: Based on the total weight of the lithium supplementing layer, the content of the conductive agent is 8-20 weight %.

13. The positive electrode sheet for lithium ion battery according to any one of claims 1 to 3, characterized in that: The thickness of the lithium supplement layer is 1-10 microns; and / or The coating weight of the lithium supplement layer is 5-15 mg / 1540.25 cm 2 . 14 . A lithium ion battery comprising a negative electrode sheet, an electrolyte, and a positive electrode sheet for a lithium ion battery according to any one of claims 1 to 13.

15. A method for manufacturing a lithium ion battery as claimed in claim 14, the method comprising: A) providing a current collector; B) forming a positive electrode active material layer on at least one surface of the current collector, wherein the positive electrode active material layer comprises lithium iron phosphate or a positive electrode active material represented by Formula I: LiNi x Co y A z O2 of formula I wherein A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1; C) mixing lithium peroxide, a transition metal oxide, a solvent, and optionally a binder and optionally a conductive agent to form a slurry, wherein the transition metal oxide comprises an oxide of at least one element selected from the group consisting of iron, cobalt, nickel, manganese, copper, molybdenum, titanium, vanadium, chromium, lead, scandium, yttrium, palladium, platinum and silver; D) applying the slurry onto the positive electrode active material layer to form a lithium supplement layer, thereby preparing a positive electrode sheet; as well as E) placing the positive electrode sheet and the negative electrode sheet together into a battery housing, injecting electrolyte into the battery housing, and performing formation and aging, wherein the charging current after formation and full charging is 0.02-0.05C.

16. A battery module comprising the lithium-ion battery according to claim 14.

17. A battery pack comprising the battery module according to claim 16. 18 . An electrical device comprising at least one of the lithium-ion battery according to claim 14 , the battery module according to claim 16 , and the battery pack according to claim 17 .

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