Positive electrode sheet, battery, and electric device

Abstract

The application relates to a positive electrode sheet, a battery and an electric device. The positive electrode sheet comprises a positive current collector, a first positive active material layer and a second positive active material layer, and the second positive active material layer is located on the side of the first positive active material layer away from the current collector; the first positive active material comprises a polyanion positive material containing Mn elements; the second positive active material layer comprises a second positive active material and a manganese ion adsorbent; and the second positive active material comprises a layered ternary material. The polyanion positive material containing Mn elements is sandwiched by the current collector and the layered ternary material, and the manganese ion adsorbent is arranged in the second positive active material layer; when Mn in the polyanion positive material containing Mn elements is dissolved and diffuses outward, it must pass through the second positive active material layer, so that the diffusion of Mn to the negative electrode can be limited.

Description

TECHNICAL FIELD

[0001] The application relates to a positive electrode sheet, a battery and an electric device. BACKGROUND

[0002] In recent years, with the development of lithium ion secondary battery technology, lithium ion secondary batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Because lithium ion secondary batteries have developed greatly, higher requirements have been put forward for their battery performance. SUMMARY

[0003] The application aims to provide a positive electrode sheet, a battery and an electric device.

[0004] Embodiments of the application are implemented as follows:

[0005] In a first aspect, the embodiments of the application provide a positive electrode sheet, which comprises: the positive electrode sheet comprises a positive electrode current collector, a first positive electrode active material layer and a second positive electrode active material layer, the second positive electrode active material layer is located on the side of the first positive electrode active material layer away from the positive electrode current collector; the first positive electrode active material layer comprises a first positive electrode active material; the first positive electrode active material comprises a polyanion positive electrode material containing Mn elements; the second positive electrode active material layer comprises a second positive electrode active material and a manganese ion adsorbent; the second positive electrode active material comprises a layered ternary material.

[0006] The polyanion positive electrode material containing Mn elements has better cycle performance; and the polyanion positive electrode material containing Mn elements is beneficial to reduce the probability of thermal runaway of the battery; and the layered ternary material has higher energy density; in the above technical solution, the first positive electrode active material comprising the polyanion positive electrode material containing Mn elements and the second positive electrode active material comprising the layered ternary material are formed on the surface of the current collector; the characteristics of the polyanion positive electrode material containing Mn elements and the layered ternary material can be synergistically utilized to improve the comprehensive performance of the battery.

[0007] Further, through research, it is found that the polyanion positive electrode material containing Mn element has a phenomenon of manganese dissolution, and the dissolved manganese can block the separator between the positive electrode and the negative electrode, or form a manganese compound on the negative electrode, thereby destroying the SEI film of the negative electrode, causing the battery resistance to rise, and seriously affecting the cycle life of the battery. In the above technical solution, the polyanion positive electrode material containing Mn element is arranged close to the current collector, and the layered ternary material is arranged in the upper layer; the polyanion positive electrode material containing Mn element is sandwiched by the current collector and the layered ternary material, and the manganese ion adsorbent is arranged in the second positive electrode active material layer; when the Mn in the polyanion positive electrode material containing Mn element is dissolved and diffuses outward, it must pass through the second positive electrode active material layer, so as to be adsorbed by the manganese ion adsorbent in the second positive electrode active material layer.

[0008] In the above technical solution, such a structure can limit the diffusion of Mn to the negative electrode, and can use the layered ternary material as a carrier of the manganese ion adsorbent, without the need to additionally increase a layer of carrier of the Mn adsorbent to affect the energy density.

[0009] In some optional embodiments, the manganese ion adsorbent includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, disodium iminotriacetate, 1,2-cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, citric acid, or tartaric acid.

[0010] In the above technical solution, each manganese ion adsorbent can effectively adsorb manganese ions, limit the diffusion of Mn to the negative electrode, thereby reducing the damage of the dissolved manganese to the SEI film of the negative electrode, and being beneficial to the cycle life of the battery.

[0011] In some optional embodiments, the content of Mn in the first positive electrode active material accounts for f of the total metal ion content;

[0012] The mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b;

[0013] The mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a;

[0014] Wherein b≥0.9%*f*a.

[0015] In the above technical solution, by limiting the relationship between the content of Mn in the first positive electrode active material and the manganese ion adsorbent, the dissolution of Mn in the first positive electrode active material can be better reduced, and the cycle life of the battery can be more improved.

[0016] In some alternative embodiments, the mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a, and a is 30% to 70%.

[0017] In some alternative embodiments, the mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b; b is 0.1% to 0.5%.

[0018] In some alternative embodiments, the content of Mn in the first positive electrode active material accounts for f of the total metal ions; f is 30% to 70%.

[0019] In some alternative embodiments, the first positive electrode active material comprises LiMPO4, M comprises Mn and a non-Mn element;

[0020] Optionally, the non-Mn element comprises one or both of a first doping element and a second doping element, the first doping element is manganese site doping, and the second doping element is phosphorus site doping;

[0021] Optionally, the first doping element comprises one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge;

[0022] Optionally, the first doping element comprises at least two of Fe, Ti, V, Ni, Co, and Mg;

[0023] Optionally, the second doping element comprises one or more of B, S, Si, and N;

[0024] Optionally, the first positive electrode active material comprises Li 1+x Mn 1-y A y P 1-z R z O4, wherein x is any number in the range of -0.100 to 0.100, y is any number in the range of 0.001 to 0.500, z is any number in the range of 0.001 to 0.100, A comprises one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and R comprises one or more of B, S, Si, and N;

[0025] Optionally, the first positive electrode active material comprises Li a A e Mn 1-f B f P 1-g C g O 4-n D n;

[0026] A comprises one or more elements of Zn, Al, Na, K, Mg, Nb, Mo and W;

[0027] B comprises one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge;

[0028] C comprises one or more elements of B, S, Si and N;

[0029] D comprises one or more elements of S, F, Cl and Br;

[0030] a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the first positive electrode active material is electrically neutral.

[0031] In some optional embodiments, the layered ternary material comprises: Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y , wherein 0≤a<0.65, 0≤b≤1, 0≤c≤1, 0≤d<1, 0≤y≤1, 0.2≤x≤1.2; M is at least one of Al, Mn, Mg, Nb, Ti, Ba, B.

[0032] In a second aspect, the embodiments of the present application provide a battery, which comprises the positive electrode sheet provided in the first aspect.

[0033] In a third aspect, the embodiments of the present application provide a power utilization device, which comprises the battery provided in the second aspect.

[0034] In the above technical solution, the power utilization device is provided with the battery provided in the second aspect, and has better electrical performance. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0036] Figure 1A structural schematic diagram of a vehicle provided for some embodiments of the present application;

[0037] Figure 2 An exploded view of a battery provided for some embodiments of the present application;

[0038] Figure 3 An exploded view of a battery cell provided for some embodiments of the present application; Figure 2 An exploded view of a battery cell provided for some embodiments of the present application;

[0039] Figure 4 A partial structural schematic diagram of an electrode assembly provided for some embodiments of the present application;

[0040] Figure 5 A partial structural schematic diagram of a positive electrode provided for some embodiments of the present application.

[0041] Icon:

[0042] A vehicle 1000;

[0043] A battery 100; a controller 200; a motor 300;

[0044] A box body 10; a first part 11; a second part 12; a containing space 13;

[0045] A battery cell 20; a shell 21; an electrode assembly 22; an electrode terminal 23; a pressure relief structure 24;

[0046] A shell 211; a cover 212; a positive electrode 221; a negative electrode 222; a separator 223;

[0047] A positive current collector 2211; a positive active material layer 2212; a first positive active material layer 2213; a second positive active material layer 2214;

[0048] A negative current collector 2221; a negative active material layer 2222. DETAILED DESCRIPTION

[0049] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0051] In the description of the embodiments of the present application, the technical terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0052] In the description of the embodiments of the present application, the technical terms "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the embodiments of the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0053] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be directly connected, or can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0054] Reference herein to "embodiments" means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily all refer to the same embodiment, nor is it independent or alternative to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0055] In the embodiments of the present application, the same reference signs represent the same components, and for the sake of brevity, detailed description of the same components is omitted in different embodiments. It should be understood that the height, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall height, length, width and other dimensions of integrated devices, are only exemplary and should not constitute any limitation on the present application.

[0056] It is found through research that the use of a single positive active material cannot balance the performance of the battery in all aspects.

[0057] Further research found that the poly-anion positive electrode material containing Mn element has better cycle performance; and the poly-anion positive electrode material containing Mn element is beneficial to reduce the probability of thermal runaway of the battery; but the energy density of the poly-anion positive electrode material containing Mn element is lower than that of the layered ternary material; and the layered ternary material has higher energy density, but the cycle performance of the layered ternary material is lower than that of the poly-anion positive electrode material containing Mn element, and the layered ternary material is not conducive to reducing the probability of thermal runaway of the battery. Therefore, the poly-anion positive electrode material containing Mn element and the layered ternary material can be used at the same time to balance the cycle performance and the energy density.

[0058] Further research found that when the poly-anion positive electrode material containing Mn element and the layered ternary material are used at the same time, the poly-anion positive electrode material containing Mn element has manganese dissolution, and the dissolved manganese can block the separator between the positive electrode and the negative electrode, or form a manganese compound on the negative electrode, thereby destroying the SEI film of the negative electrode, causing the battery resistance to rise, and seriously affecting the cycle life of the battery.

[0059] At present, for the problem of manganese dissolution, the manganese iron lithium phosphate is usually modified by doping or coating, or the electrolyte is optimized in composition. However, this method needs to coat a protective layer on the surface of the active material or the negative electrode, which effectively reduces the dissolution of manganese ions, and further worsens the battery impedance; but has certain influence on the energy density.

[0060] Based on the above findings, the embodiment of the present application provides a positive electrode sheet, which comprises: the positive electrode sheet comprises a positive electrode current collector, a first positive electrode active material layer and a second positive electrode active material layer, and the second positive electrode active material layer is located on the side of the first positive electrode active material layer away from the positive electrode current collector. The first positive electrode active material layer comprises a first positive electrode active material; the first positive electrode active material comprises a poly-anion positive electrode material containing Mn element; the second positive electrode active material layer comprises a second positive electrode active material and a manganese ion adsorbent; and the second positive electrode active material comprises a layered ternary material.

[0061] In the above technical solution, the poly-anion positive electrode material containing Mn element is arranged close to the current collector, and the layered ternary material is arranged in the upper layer; so that the poly-anion positive electrode material containing Mn element is sandwiched between the current collector and the layered ternary material, and the manganese ion adsorbent is arranged in the second positive electrode active material layer; when the Mn in the poly-anion positive electrode material containing Mn element dissolves and diffuses outward, it must pass through the second positive electrode active material layer, so as to be adsorbed by the manganese ion adsorbent in the second positive electrode active material layer.

[0062] In the technical solution, the structure can limit the diffusion of Mn to the negative electrode, and can use the layered ternary material as a carrier of the Mn ion adsorbent, without adding an additional carrier layer of the Mn adsorbent (the carrier layer is not an active material) to affect the energy density.

[0063] The battery provided in the application comprises the positive electrode plate provided in the application, and the comprehensive performance of the battery is improved.

[0064] The electric equipment provided in the application comprises the battery provided in the application, and the electric performance of the electric equipment is improved.

[0065] The following embodiments are described by taking a lithium ion battery as an example for the convenience of description.

[0066] Referring to Figure 1 , Figure 1 A structural schematic diagram of a vehicle 1000 is provided in some embodiments of the application. The vehicle 1000 can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid automobile, or a range extended automobile. The vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom, the head, or the tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further comprise a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation, and driving.

[0067] In some embodiments of the application, the battery 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0068] In the application, the battery 100 refers to a single physical module comprising one or more battery monomers 20 to provide voltage and capacity. The battery 100 generally comprises a box 10 for packaging one or more battery monomers 20. The box 10 can avoid the influence of liquid or other foreign matters on the charging or discharging of the battery monomer 20.

[0069] Referring to Figure 2 , Figure 2An exploded view of the battery 100 provided for some embodiments of the present application can include a box 10 and a battery cell 20, wherein the battery cell 20 is accommodated in the box 10. The box 10 is used to accommodate the battery cell 20, and the box 10 can be of various structures. In some embodiments, the box 10 can include a first part 11 and a second part 12, the first part 11 and the second part 12 are mutually covered, and the first part 11 and the second part 12 jointly define an accommodation space 13 for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 is a plate-like structure, which is covered on the open side of the second part 12 to form the box 10 with the accommodation space 13; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 is covered on the open side of the second part 12 to form the box 10 with the accommodation space 13. Of course, the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0070] In the battery 100, the battery cell 20 can be one or multiple. If the battery cell 20 is multiple, the multiple battery cells 20 can be connected in series, in parallel or in a mixed manner, wherein the mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel or in a mixed manner, and then the whole of the multiple battery cells 20 is accommodated in the box 10. Alternatively, the multiple battery cells 20 can be connected in series, in parallel or in a mixed manner to form a module, and then multiple modules are connected in series, in parallel or in a mixed manner to form a whole, which is accommodated in the box 10. The battery 100 can also include other structures, for example, the multiple battery cells 20 can be electrically connected through a busbar to realize the parallel or series or mixed connection of the multiple battery cells 20.

[0071] Each battery cell 20 can be a lithium ion battery, such as a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium ion battery or a magnesium ion battery, but is not limited thereto.

[0072] Referring to Figure 3 , Figure 3 for Figure 2 an exploded view of the battery cell 20. The battery cell 20 refers to the smallest unit constituting the battery 100. The battery cell 20 can include a shell 21, an electrode assembly 22 and an electrolyte, wherein the electrode assembly 22 and the electrolyte are accommodated in the shell 21.

[0073] The shell 21 can include a shell body 211 and a cover body 212. The shell body 211 is a component for cooperating with the cover body 212 to form an internal sealed space of the battery monomer 20, wherein the formed sealed space can be used to accommodate the electrode assembly 22, the electrolyte and other components. The cover body 212 refers to a component that is covered on the opening of the shell body 211 to isolate the internal environment of the battery monomer 20 from the external environment. The shape of the cover body 212 can be adapted to the shape of the shell body 211 to cooperate with the shell body 211. The cover body 212 can also be provided with functional components such as the electrode terminal 23 and the pressure relief structure 24. A sealing ring can be arranged between the opening of the shell body 211 and the cover body 212 to realize the sealing between the shell body 211 and the cover body 212.

[0074] The shell body 211 and the cover body 212 can be various shapes and sizes, such as a cuboid, a cylinder, a hexagonal prism, etc. Specifically, the shape of the shell body 211 and the cover body 212 can be determined according to the specific shape and size of the electrode assembly 22. The material of the shell body 211 and the cover body 212 can be various, such as but not limited to copper, iron, aluminum, stainless steel, aluminum alloy, etc. The material of the sealing ring can be various, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate), etc. The outer surface of the shell body 211 can form a plating layer, and the material of the plating layer can be various, such as but not limited to Ni, Cr, etc. corrosion-resistant materials.

[0075] Referring to Figure 4 , the electrode assembly 22 can be composed of a positive electrode sheet 221, a negative electrode sheet 222 and a separator 223. The separator 223 is between the positive electrode sheet 221 and the negative electrode sheet 222 to play a role of isolation. The electrode assembly 22 can be a wound structure or a stacked structure, and the embodiments of the present application are not limited thereto.

[0076] Referring to Figure 4 , the negative electrode sheet 222 includes a negative electrode current collector 2221 and a negative electrode active material layer 2222. The material of the negative electrode current collector 2221 can be copper, and the negative electrode active material layer 2222 includes a negative electrode active material. The negative electrode active material includes at least one of graphite, silicon, silicon alloy or tin alloy.

[0077] Referring to Figure 4 , the positive electrode sheet 221 includes a positive electrode current collector 2211 and a positive electrode active material layer 2212. Taking the lithium ion battery monomer 20 as an example, the material of the positive electrode current collector 2211 can be aluminum.

[0078] Further, referring to Figure 5In some embodiments of the present application, a positive electrode tab is provided, the positive electrode tab comprising: the positive electrode tab comprising a positive electrode current collector 2211, a first positive electrode active material layer 2213, and a second positive electrode active material layer 2214, the second positive electrode active material layer 2214 being located on a side of the first positive electrode active material layer 2213 away from the positive electrode current collector 2211.

[0079] The first positive electrode active material layer 2213 comprises a first positive electrode active material; the first positive electrode active material comprises a polyanion positive electrode material containing Mn elements.

[0080] The second positive electrode active material layer 2214 comprises a second positive electrode active material and a manganese ion adsorbent; the second positive electrode active material comprises a layered ternary material.

[0081] In the above technical solution, by forming the first positive electrode active material comprising the polyanion positive electrode material containing Mn elements and the second positive electrode active material comprising the layered ternary material on the surface of the current collector, the characteristics of the polyanion positive electrode material containing Mn elements and the layered ternary material can be synergistically utilized to improve the comprehensive performance of the battery.

[0082] In the above technical solution, the polyanion positive electrode material containing Mn elements is arranged in a layer close to the current collector, and the layered ternary material is arranged in an upper layer; the polyanion positive electrode material containing Mn elements is sandwiched between the current collector and the layered ternary material, and the manganese ion adsorbent is arranged in the second positive electrode active material layer; when Mn in the polyanion positive electrode material containing Mn elements is dissolved and diffuses outward, it must pass through the second positive electrode active material layer, so that it can be adsorbed by the manganese ion adsorbent in the second positive electrode active material layer.

[0083] In the above technical solution, such a structure arrangement can limit the diffusion of Mn to the negative electrode on the one hand, and can use the layered ternary material as a carrier of the manganese ion adsorbent on the other hand, without the need to additionally increase a layer of the carrier of the Mn adsorbent to affect the energy density.

[0084] Further, in the above technical solution, by adding the manganese ion adsorbent in the second positive electrode active material layer, the Mn ions can be adsorbed in a relatively short diffusion path after being dissolved; thereby facilitating the improvement of the adsorption efficiency.

[0085] Further, in the above technical solution, the polyanion positive electrode material refers to a series of compounds containing tetrahedral or octahedral anion structural units (XO m ) n- (X=P, S, As, Mo, W).

[0086] Further optionally, in some embodiments of the present application, the above-mentioned polyanion positive electrode material can be selected from: lithium phosphate salt of olivine structure.

[0087] These materials have the characteristics of reducing the probability of battery thermal runaway, and better cycle performance.

[0088] Further, in some embodiments of the present application, the first positive electrode active material described above comprises LiMPO4, M comprises Mn and a non-Mn element.

[0089] The LiMPO4 described above is not a specific molecular formula, but a general expression of lithium manganese phosphate.

[0090] Further optionally, in some embodiments of the present application, the non-Mn element described above comprises one or both of a first doping element and a second doping element, the first doping element is manganese site doping, and the second doping element is phosphorus site doping.

[0091] Further optionally, in some embodiments of the present application, the first doping element described above comprises one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge.

[0092] Further optionally, in some embodiments of the present application, the first doping element described above comprises at least two of Fe, Ti, V, Ni, Co and Mg.

[0093] Further optionally, in some embodiments of the present application, the second doping element described above comprises one or more elements of B, S, Si and N.

[0094] Further optionally, in some embodiments of the present application, the first positive electrode active material described above comprises Li 1+ x Mn 1-y A y P 1-z R z O4, wherein x is any numerical value in the range of -0.100 to 0.100, y is any numerical value in the range of 0.001 to 0.500, z is any numerical value in the range of 0.001 to 0.100, A comprises one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and R comprises one or more elements of B, S, Si and N.

[0095] Further optionally, in some embodiments of the present application, the first positive electrode active material described above comprises Li a A e Mn 1-f B f P 1-g C g O4-n D n ;

[0096] wherein A comprises one or more elements selected from the group consisting of Zn, Al, Na, K, Mg, Nb, Mo and W;

[0097] B comprises one or more elements selected from the group consisting of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge;

[0098] C comprises one or more elements selected from the group consisting of B, S, Si and N;

[0099] D comprises one or more elements selected from the group consisting of S, F, Cl and Br;

[0100] a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the first positive electrode active material is electrically neutral.

[0101] Further, in some embodiments of the present application, the compound Li a A e Mn 1-f B f P 1-g C g O 4-n D n A method of preparing the compound Li

[0102] (1) dissolving and stirring a manganese source, an element A source doped with manganese, and an acid in a solvent to form a suspension of a manganese salt doped with element A, filtering the suspension and drying the filter cake to obtain a manganese salt doped with element A;

[0103] (2) adding a lithium source, a phosphorus source, and an element R source, a solvent, and the manganese salt doped with element A obtained from step (1) into a reaction vessel to grind and mix to obtain a slurry;

[0104] (3) transferring the slurry obtained from step (2) to a spray drying device to perform spray drying granulation to obtain granules;

[0105] (4) sintering the granules obtained from step (3) to obtain a positive electrode active material.

[0106] In any embodiment, the manganese source can be a manganese-containing substance known in the art that can be used to prepare lithium manganese phosphate, for example, the manganese source can be selected from one or a combination of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, manganese carbonate.

[0107] The acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, an organic acid such as oxalic acid, and the like, and can be, for example, oxalic acid. The source of the element R is selected from at least one of a sulfate, a borate, a nitrate, and a silicate of the element R. The source of the element A is selected from at least one of an elemental form, an oxide, a phosphate, an oxalate, a carbonate, and a sulfate of the element A.

[0108] In some embodiments, the positive active material comprises Li a A e Mn 1-f B f P 1-g C g O 4-n D n wherein A comprises one or more elements of Zn, Al, Na, K, Mg, Nb, Mo, and W, B comprises one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge, C comprises one or more elements of B, S, Si, and N, D comprises one or more elements of S, F, Cl, and Br, a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the positive active material is charge neutral.

[0109] It is to be noted that Li a A e Mn 1-f B f P 1-g C g O 4-n D n The compound is actually a specific LiMPO4material. Its preparation method can refer to Li a A e Mn 1-f B f P 1-g C g O 4-n D n , which is not limited here.

[0110] The battery will be accompanied by Li deintercalation and consumption during charging and discharging. The molar content of Li is different when the battery is discharged to different states.

[0111] In the enumeration of the positive active material in this application, the molar content of Li is the initial state of the material, i.e., the state before feeding. The positive active material is applied to the battery system, and the molar content of Li will change after charging and discharging cycles.

[0112] In addition, the molar content of O element is not strictly the coefficient of O element in the chemical formula, and fluctuation may occur, for example, Li 1+x Mn 1-y A y P 1-z R z The molar content of O element in O4 is not strictly 4.

[0113] Further, in some embodiments of the present application, the above-mentioned manganese ion adsorbent includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium salt of ethylenediaminetetraacetate, disodium iminodiacetic acid, 1,2-cyclohexanediaminetetraacetic acid, diethylenetriamine pentaacetic acid, hydroxyethyl ethylenediamine triacetic acid, citric acid or tartaric acid.

[0114] In the above technical solution, each manganese ion adsorbent can effectively adsorb manganese ions, limit the diffusion of Mn to the negative electrode, thereby reducing the dissolution of manganese to damage the negative electrode SEI film, and being beneficial to the cycle life of the battery.

[0115] Further, in the above technical solution, the N or O with a lone pair of electrons in each manganese ion adsorbent can form a coordination bond with Mn 2+ to achieve the adsorption of dissolved manganese ions, thereby being beneficial to the cycle life of the battery.

[0116] Further, in some embodiments of the present application, the above-mentioned manganese ion adsorbent selects any one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium salt of ethylenediaminetetraacetate, disodium iminodiacetic acid, 1,2-cyclohexanediaminetetraacetic acid, diethylenetriamine pentaacetic acid, hydroxyethyl ethylenediamine triacetic acid, citric acid or tartaric acid.

[0117] Further, in some embodiments of the present application, the above-mentioned manganese ion adsorbent selects a mixture of ethylenediaminetetraacetic acid and disodium ethylenediaminetetraacetate. In the mixture, each substance can be mixed in any ratio.

[0118] Further, in some embodiments of the present application, the above-mentioned manganese ion adsorbent selects a mixture of tetrasodium salt of ethylenediaminetetraacetate, disodium iminodiacetic acid, 1,2-cyclohexanediaminetetraacetic acid and diethylenetriamine pentaacetic acid. In the mixture, each substance can be mixed in any ratio.

[0119] Further, in some embodiments of the present application, the above-mentioned manganese ion adsorbent selects a mixture of hydroxyethyl ethylenediamine triacetic acid, citric acid and tartaric acid. In the mixture, each substance can be mixed in any ratio.

[0120] Further, in some embodiments of the present application, the manganese ion adsorbent is a mixture of ethylenediaminetetraacetic acid and citric acid. The mixture can be mixed in any ratio.

[0121] Further, in some embodiments of the present application, the content of Mn in the first positive electrode active material accounts for f of the total metal ions;

[0122] The mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b;

[0123] The mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a;

[0124] Wherein b≥0.9%*f*a.

[0125] In the above technical solution, by limiting the content of Mn in the manganese ion adsorbent and the first positive electrode active material to satisfy the above relationship, the Mn elution in the first positive electrode active material can be better reduced, and the battery cycle life can be more improved.

[0126] Further optionally, b≥1.0%*f*a.

[0127] For example, in some embodiments of the present application, b=0.9%*f*a, or b=1.0%*f*a, or b=1.1%*f*a, or b=1.2%*f*a, or b=1.5%*f*a, or b=2.0%*f*a, or b=2.5%*f*a, or b=3%*f*a.

[0128] Further, in some embodiments of the present application, the mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a, and a is 30% to 70%.

[0129] In the above technical solution, the mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is within the above range, which is beneficial to obtain a battery with good comprehensive performance.

[0130] Further optionally, in some embodiments of the present application, the mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a, and a is 50% to 70%.

[0131] For example, in some embodiments of the present application, the mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a, and a is 51%, 55%, 60%, 65%, 68%, or 69%.

[0132] Further, in some embodiments of the present application, the mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b; b is 0.1% to 0.5%.

[0133] In the above technical solution, the mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is within the above range, which can effectively adsorb the dissolved manganese, reduce the probability of the dissolved manganese blocking the separator between the positive electrode and the negative electrode or forming a manganese compound on the negative electrode, and improve the cycle life of the battery.

[0134] Further optionally, in some embodiments of the present application, the mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b; b is 0.11% to 0.49%.

[0135] Exemplarily, in some embodiments of the present application, the mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b; b is 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, 0.30%, 0.32%, 0.35%, 0.38%, 0.40%, 0.42%, 0.45% or 0.48%.

[0136] Further, in some embodiments of the present application, the content of Mn in the first positive electrode active material accounts for f of the total metal ions; f is 30% to 70%.

[0137] In the above technical solution, the content of Mn in the first positive electrode active material accounts for f of the total metal ions within the above range, which can be matched with the manganese ion adsorbent, reduce the probability of the dissolved manganese blocking the separator between the positive electrode and the negative electrode or forming a manganese compound on the negative electrode, and improve the cycle life of the battery.

[0138] Further optionally, in some embodiments of the present application, the content of Mn in the first positive electrode active material accounts for f of the total metal ions; f is 31% to 69%.

[0139] Exemplarily, in some embodiments of the present application, the content of Mn in the first positive electrode active material accounts for f of the total metal ions; f is 32%, 35%, 38%, 40%, 42%, 45%, 50%, 52%, 55%, 60% or 65%.

[0140] Further, in some embodiments of the present application, the layered ternary material comprises: Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y wherein 0≤a<0.65, 0≤b≤1, 0≤c≤1, 0≤d<1, 0≤y≤1, 0.2≤x≤1.2; M is at least one of Al, Mn, Mg, Nb, Ti, Ba, B.

[0141] In the above technical solution, the materials have the characteristics of high energy density, which is beneficial to improve the battery capacity of the battery.

[0142] It should be noted that the battery will be accompanied by Li deintercalation and consumption during charging and discharging, and the molar content of Li is different when the battery is discharged to different states. The limitation of x in the above chemical formula includes the molar content of Li in different charging and discharging states of the battery (usually the battery voltage is between 2-5V).

[0143] Some specific embodiments are listed below to better illustrate the present application.

[0144]

First positive electrode active material

[0145] A, compound Li 0.945 Mn 0.6 Fe 0.4 P 0.995 S 0.005 O4

[0146] Step S1: According to the mass ratio of the compound, manganese carbonate and ferrous carbonate are added to the mixer and mixed for 6h. Then the obtained mixture is transferred into a reaction kettle, 5L deionized water and oxalic acid dihydrate are added, heated to 80℃, and stirred at a speed of 500rpm for 6h. The mixture is uniformly mixed until the reaction is terminated and no bubbles are generated, obtaining a Fe-doped manganese oxalate suspension. Then the suspension is filtered, dried at 120℃, and then sand milled to obtain manganese oxalate particles with a particle size of 100nm.

[0147] Step S2: Take the manganese oxalate prepared in step S1 and lithium carbonate, ammonium dihydrogen phosphate and dilute sulfuric acid, and add them to 20L deionized water, stir well, and mix uniformly at 80℃ for 10h to obtain a slurry. The slurry is transferred into a spray drying device for spray drying and granulation, and dried at a temperature of 250℃ to obtain a powder. The powder is sintered in a roller kiln at 700℃ for 4h in a protective atmosphere (90% nitrogen and 10% hydrogen) to obtain Li 0.997 Mn 0.60 Fe 0.39 3V 0.004 Co 0.003 P 0.997 S 0.003 O4.

[0148] B, compound Li0.947 Mn 0.7 Fe 0.38 Mg 0.02 P 0.994 S 0.005 B 0.001 O4

[0149] Step S1 : According to the mass ratio of compound ingredients, manganese carbonate, magnesium sulfate, ferrous carbonate are added into a mixer and mixed for 6h. Then the obtained mixture is transferred into a reaction kettle, 5L deionized water and oxalic acid dihydrate are added, heated to 80°C, and stirred at 500rpm for 6h until the reaction is terminated without bubble generation, obtaining a Mg, Fe doped manganese oxalate suspension. Then the suspension is filtered, dried at 120°C, and sand milled to obtain manganese oxalate particles with a particle size of 100nm.

[0150] Step S2: The manganese oxalate prepared in step S1 and lithium carbonate, ammonium dihydrogen phosphate, boric acid and dilute sulfuric acid are taken and added into 20L deionized water, stirred well, and uniformly mixed at 80°C for 10h to obtain a slurry. The slurry is transferred into a spray drying device for spray drying and granulation, dried at a temperature of 250°C to obtain a powder. The powder is sintered in a roller kiln at 700°C for 4h in a protective atmosphere (90% nitrogen and 10% hydrogen) to obtain Li 0.947 Mn 0.7 Fe 0.38 Mg 0.02 P 0.994 S 0.005 B 0.001 O4.

[0151] C, compound Li 0.907 Mn 0.3 Fe 0.66 V 0.04 P 0.995 S 0.005 O4

[0152] Step S1 : According to the mass ratio of compound ingredients, manganese carbonate, vanadium dichloride, ferrous carbonate are added into a mixer and mixed for 6h. Then the obtained mixture is transferred into a reaction kettle, 5L deionized water and oxalic acid dihydrate are added, heated to 80°C, and stirred at 500rpm for 6h until the reaction is terminated without bubble generation, obtaining a V, Fe doped manganese oxalate suspension. Then the suspension is filtered, dried at 120°C, and sand milled to obtain manganese oxalate particles with a particle size of 100nm.

[0153] Step S2: Take the manganese oxalate prepared in step S1 and lithium carbonate, 1 ammonium dihydrogen phosphate and dilute sulfuric acid, add them to 20 L of deionized water, stir well, and mix uniformly at 80°C for 10 h to obtain a slurry. The slurry is transferred to a spray drying device for spray drying granulation, and dried at a temperature of 250°C to obtain a powder. The powder is sintered in a roller kiln at 700°C for 4 h in a protective atmosphere (90% nitrogen and 10% hydrogen) to obtain Li 0.907 Mn 0.3 Fe 0.6 6V 0.04 P 0.995 S 0.005 O4.

[0154] or obtained by commercial purchase.

[0155]

Second positive electrode active material

[0156] The layered ternary material is obtained by commercial purchase.

[0157]

Method for preparing positive electrode sheet

[0158] The first positive electrode active material described above is selected and mixed with a conductive agent and a binder in a certain mass ratio, and dispersed in N-methyl pyrrolidone to prepare a first positive electrode active material slurry;

[0159] The second positive electrode active material described above is selected and mixed with a manganese ion adsorbent, a conductive agent and a binder in a certain mass ratio, and dispersed in N-methyl pyrrolidone to prepare a second positive electrode active material slurry;

[0160] The first positive electrode active material slurry prepared as described above is coated on both sides of an aluminum foil, and at the same time, the second positive electrode active material slurry prepared as described above is coated on the surface of the positive electrode which has been coated with the first positive electrode active material slurry to obtain a positive electrode sheet.

[0161] Examples 1-13

[0162] A positive electrode sheet is provided, which is prepared according to the method for preparing a positive electrode sheet described above; the parameters of the positive electrode sheets of each example are shown in Table 1.

[0163] Comparative Examples 1-3

[0164] A positive electrode sheet is provided, which is prepared according to the method for preparing a positive electrode sheet described above; the parameters of the positive electrode sheets of each example are shown in Table 1.

[0165] The positive electrode sheet provided in each of the examples or comparative examples described above is detected:

[0166] The positive electrode sheet of each example or comparative example was dissolved in 100 ml of reverse aqua regia (concentrated hydrochloric acid: concentrated nitric acid = 1:3) (concentration of concentrated hydrochloric acid ~ 37%, concentration of concentrated nitric acid ~ 65%), and the content of each element in the solution was measured by ICP. XRD was used to assist in confirming the material phase

[0167] 1. The content of manganese element was measured and converted; f = the amount of manganese element / the total amount of metal ions of the first active material * 100%.

[0168] 2. The content of manganese ion adsorbent was measured and converted; b = the content of manganese ion adsorbent / the total mass of the first positive electrode active material and the second positive electrode active material * 100%.

[0169] 3. The content of the first positive electrode active material was measured and converted; a = the first positive electrode active material / the total mass of the first positive electrode active material and the second positive electrode active material * 100%.

[0170]

Preparation of lithium ion battery

[0171] 1) Preparation of negative electrode sheet

[0172] The negative electrode active material artificial graphite, hard carbon, conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickening agent sodium carboxymethyl cellulose (CMC) were mixed in deionized water according to the weight ratio of 90:5:2:2:1, and then coated on a copper foil, dried and cold-pressed to obtain a negative electrode sheet. The coating amount was 0.2 g / cm 2 , and the compacted density was 1.7 g / cm 3 .

[0173] 2) Preparation of separator

[0174] A polyethylene film was used as a substrate, and a coating layer was coated on the substrate to obtain a separator.

[0175] 3) Preparation of lithium ion battery

[0176] The positive electrode sheet provided by each of the foregoing examples or comparative examples was stacked in order with the separator and the negative electrode sheet, with the separator between the positive and negative electrodes to serve as a separation function, and was wound to obtain a bare cell. The bare cell was placed in an outer package, electrolyte was injected and packaged to obtain a battery. The electrolyte was a solution of 1 mol / L LiPF6 in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1.

[0177]

Test of lithium ion battery

[0178] Cycling method:

[0179] The full battery was charged at 1C to 4.3V at 2.5V in a constant temperature environment at 45°C, and then charged at 4.3V until the current was less than or equal to X mA (X = 0.05*capacity of the cell). After standing for 5 minutes, it was discharged at 1C to 2.5V, and the discharge capacity at this time was recorded as D0. The foregoing charge and discharge cycle was repeated until the discharge capacity decreased to 90% of D0. The number of cycles the battery had undergone at this time was recorded.

[0180] 1. The calculation formula of "cycle life improvement range" is M / (N-1), wherein M is the number of cycles of each embodiment when the cycle capacity decays to 90% of the initial capacity at 45°C, and N is the number of cycles of Comparative Example 1 when the cycle capacity decays to 90% of the initial capacity.

[0181] 2. The test method of Mn dissolution amount is as follows: the lithium ion battery with a cycle capacity decayed to 90% of the initial capacity is fully charged at 0.1C to the actual upper limit voltage of the cell, then the cell is disassembled, the anode is cleaned by soaking in a DMC (dimethyl carbonate) solution, and then the ICP of Mn element is tested to obtain the data, which is the dissolution amount of Mn.

[0182] The test results are shown in Table 2.

[0183] Table 1

[0184]

[0185] Table 2

[0186]

[0187] From the above table, it can be seen that:

[0188] Compared with Comparative Example 1, the Mn dissolution amount of the battery of each embodiment of the application is significantly lower than that of Comparative Example 1, which shows that the embodiment scheme of the application effectively improves the Mn dissolution problem of the positive electrode material.

[0189] Further, compared with Comparative Example 1, the cycle life improvement range of the battery of each embodiment of the application is improved.

[0190] Further, compared with the other embodiments, it can be seen that when b≥0.9%*f*a, it is more conducive to the improvement of the cycle life improvement range.

[0191] Further, by comparing Example 2, Example 3 and Example 4 with each other, it can be seen that when the content of Mn and the content of the first positive electrode active material remain unchanged, the greater the proportion of the manganese ion adsorbent, the lower the Mn dissolution amount, and the greater the improvement of the cycle life improvement range.

[0192] The embodiments described above are only part of the embodiments of the present application, rather than all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

Claims

1. A positive electrode sheet, characterized by, The positive electrode plate comprises a positive electrode current collector, a first positive electrode active material layer, and a second positive electrode active material layer, the second positive electrode active material layer being located on a side of the first positive electrode active material layer away from the positive electrode current collector; The first positive electrode active material layer comprises a first positive electrode active material; the first positive electrode active material comprises a polyanion positive electrode material containing Mn elements; The second positive electrode active material layer comprises a second positive electrode active material and a manganese ion adsorbent; the second positive electrode active material comprises a layered ternary material; The content of Mn in the first positive electrode active material accounts for f of the total metal ions; The mass ratio of the manganese ion adsorbent to the total mass of the first positive electrode active material and the second positive electrode active material is b; The mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a; Wherein b≥0.9%*f*a; b is 0.1%~0.5%.

2. The positive electrode plate of claim 1, wherein The manganese ion adsorbent comprises at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium salt of ethylenediaminetetraacetic acid, disodium salt of nitrilotriacetic acid, 1,2-cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, citric acid, or tartaric acid.

3. The positive electrode plate of any one of claims 1-2, wherein The mass ratio of the first positive electrode active material to the total mass of the first positive electrode active material and the second positive electrode active material is a, and a is 30%~70%.

4. The positive electrode plate of any one of claims 1-2, wherein The content of Mn in the first positive electrode active material accounts for f of the total metal ions; f is 30%~70%.

5. The positive electrode plate of any one of claims 1-2, wherein The first positive electrode active material comprises LiMPO4, and M comprises Mn and non-Mn elements.

6. The positive electrode plate of claim 5, wherein The non-Mn elements comprise one or both of a first doping element and a second doping element, the first doping element being manganese site doping, and the second doping element being phosphorus site doping.

7. The positive electrode plate of claim 6, wherein The first doping element comprises one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge.

8. The positive electrode plate of claim 6, wherein The first doping element comprises at least two of Fe, Ti, V, Ni, Co, and Mg.

9. The positive electrode plate of claim 6, wherein The second doping element comprises one or more of B, S, Si, and N.

10. The positive electrode plate of claim 5, wherein The first positive electrode active material includes Li 1+x Mn 1-y A y P 1-z R z O4, wherein x is an arbitrary value in the range of -0.100 to 0.100, y is an arbitrary value in the range of 0.001 to 0.500, z is an arbitrary value in the range of 0.001 to 0.100, the A includes one or more elements of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb, and Ge, and the R includes one or more elements of B, S, Si, and N.

11. The positive electrode plate of claim 5, wherein The first positive electrode active material includes Li a A e Mn 1-f B f P 1-g C g O 4-n D n ; Wherein, the A comprises one or more of Zn, Al, Na, K, Mg, Nb, Mo, and W. The B includes one or more elements of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; The C includes one or more elements of B, S, Si, and N; The D includes one or more elements of S, F, Cl, and Br; The a is selected from the range of 0.9 to 1.1, the e is selected from the range of 0.001 to 0.1, the f is selected from the range of 0.001 to 0.5, the g is selected from the range of 0.001 to 0.1, the n is selected from the range of 0.001 to 0.1, and the first positive electrode active material is electrically neutral.

12. The positive electrode sheet of claim 1, wherein, The layered ternary material comprises: Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y , wherein 0≤a<0.65, 0≤b≤1, 0≤c≤1, 0≤d<1, 0≤y≤1, 0.2≤x≤1.2; M is at least one of Al, Mn, Mg, Nb, Ti, Ba, B.

13. A battery, characterized by The battery includes the positive electrode sheet of any one of claims 1-12.

14. An electrical device, characterized by The electrical device includes the battery of claim 13.

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