Positive pole piece and preparation method thereof, battery and power utilization device

Abstract

A positive pole piece (100) and a preparation method thereof, a battery and an electric device wherein the positive pole piece (100) comprises a positive current collector (11), at least one side of the positive pole piece (100) away from the positive current collector (11) comprises a polymer and an organic solvent, the organic solvent is located in the polymer, and an electrochemical oxidation window of the organic solvent is higher than 4V.

Description

Positive electrode sheet and preparation method thereof, battery and electrical device Technical Field

[0001] The present application belongs to the field of batteries, and specifically relates to a positive electrode plate and a preparation method thereof, a battery and an electrical device. Background Art

[0002] Secondary batteries are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. However, existing secondary batteries are prone to abnormally increased charge capacity when charged at high rates and high cutoff voltages (>4V), creating the risk of overcharging.

[0003] Public content

[0004] In view of the technical problems existing in the background technology, the present application provides a positive electrode plate, aiming to reduce the overcharging risk of a secondary battery containing the positive electrode plate.

[0005] In order to achieve the above-mentioned objectives, one aspect of the present application provides a positive electrode plate, wherein at least one side of the positive electrode plate away from the positive electrode current collector includes a polymer and an organic solvent, the organic solvent is located in the polymer, and the electrochemical oxidation window of the organic solvent is higher than 4V.

[0006] The present application includes at least the following beneficial effects: the present application adopts a positive electrode sheet comprising a polymer and an organic solvent, wherein the organic solvent is located in the polymer, and the polymer and the organic solvent are located on at least one side of the positive electrode sheet away from the positive electrode current collector. The polymer filled with the organic solvent can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo an oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, thereby no side reaction will occur on the positive electrode side. Moreover, under high rate charging, the organic solvent is not easily excited to undergo oxidative decomposition, thereby not generating additional electrons to reach the negative electrode side, and thus no abnormal increase in battery charging capacity will occur, thereby reducing the risk of battery overcharging.

[0007] In some embodiments, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer being disposed on at least one side of the positive electrode current collector, the positive electrode active material layer including positive electrode active particles, the surface of the positive electrode active particles having a polymer layer, the polymer layer including the polymer and the organic solvent. Thus, by forming a polymer layer including the polymer and the organic solvent on the surface of the positive electrode active particles, the polymer layer can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0008] In some embodiments, the positive electrode active material layer further comprises at least one of a binder and a conductive agent, thereby improving the conductivity of the positive electrode active material layer and the bonding strength with the positive electrode current collector.

[0009] In some embodiments, the mass ratio of the positive electrode active particles to the binder and the conductive agent is (90-100):(0-5):(0-5), or optionally (95-98.5):(0.5-2):(0.5-2). This can improve the conductivity of the positive electrode active material layer and the bonding strength with the positive electrode current collector.

[0010] In some embodiments, the thickness of the positive electrode active material layer is 30 μm-60 μm, and optionally 30 μm-50 μm. Thus, a positive electrode active material layer of this thickness can improve the energy density of the battery.

[0011] In some embodiments, the thickness of the polymer layer is 0.01 μm to 2 μm, and optionally 0.01 μm to 1 μm. Thus, forming a polymer layer of this thickness on the surface of the positive electrode active particles not only blocks direct contact between the positive electrode active material and the electrolyte solvent in the battery, preventing oxidative decomposition of the electrolyte solvent, but also reduces the impedance of the positive electrode sheet.

[0012] In some embodiments, the mass ratio of the polymer to the organic solvent is (0.1-99):(1-99.9), and can optionally be (0.1-15):(85-99.9). This effectively blocks direct contact between the positive electrode active material and the electrolyte solvent in the battery, preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0013] In some embodiments, the polymer layer further comprises an electrolyte salt, thereby improving the ion conductivity of the polymer layer.

[0014] In some embodiments, in the polymer layer, based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt is 0.1 mol / L-10 mol / L, optionally 0.5 mol / L-5 mol / L, thereby improving the ion conductivity of the polymer layer.

[0015] In some embodiments, the polymer layer further comprises at least one of a film-forming additive and an adsorption additive, thereby improving the cycle stability of the positive electrode sheet.

[0016] In some embodiments, the film-forming additive has an electrochemical oxidation window less than or equal to 4V.

[0017] In some embodiments, the adsorption additive has an electrochemical oxidation window greater than 4V.

[0018] In some embodiments, the mass ratio of the polymer to the film-forming additive and the adsorption additive is (10-100):(0-90):(0-90), and can be optionally (30-80):(20-70):(20-70). This can improve the cycle stability of the positive electrode.

[0019] In some embodiments, the positive electrode sheet includes a positive electrode active material layer and a protective layer, wherein the positive electrode active material layer is disposed on at least one side of the positive electrode current collector, and the protective layer is disposed on at least one side of the positive electrode active material layer, and the protective layer includes the polymer and the organic solvent. Thus, by forming a protective layer including the polymer and the organic solvent on the positive electrode active material layer, the protective layer can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0020] In some embodiments, the thickness of the protective layer is 0.1 μm to 40 μm, optionally 1 μm to 20 μm, and more preferably 1 μm to 10 μm. Thus, forming a protective layer of this thickness on the surface of the positive electrode active material layer not only blocks direct contact between the positive electrode active material and the electrolyte solvent in the battery, preventing oxidative decomposition of the electrolyte solvent, but also reduces the impedance of the positive electrode sheet.

[0021] In some embodiments, the mass ratio of the polymer to the organic solvent in the protective layer is (0.1-99):(1-99.9), and can optionally be (0.1-15):(85-99.9). This effectively blocks direct contact between the positive electrode active material and the electrolyte solvent in the battery, preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0022] In some embodiments, the protective layer further comprises an electrolyte salt, thereby improving the ion conductivity of the protective layer.

[0023] In some embodiments, the concentration of the electrolyte salt in the protective layer is 0.1 mol / L-10 mol / L, and can be 0.5 mol / L-5 mol / L, based on the total amount of the organic solvent and the electrolyte salt.

[0024] In some embodiments, the protective layer further comprises at least one of a film-forming additive and an adsorption additive, thereby improving the cycle stability of the positive electrode sheet.

[0025] In some embodiments, the film-forming additive has an electrochemical oxidation window less than or equal to 4V.

[0026] In some embodiments, the adsorption additive has an electrochemical oxidation window greater than 4V.

[0027] In some embodiments, the mass ratio of the polymer to the film-forming additive and the adsorption additive is (10-100):(0-90):(0-90), and can be optionally (30-80):(20-70):(20-70). This can improve the cycle stability of the positive electrode.

[0028] In some embodiments, the organic solvent comprises carbonate, carboxylate, C5-C 16 At least one of an alkane, an aromatic hydrocarbon having an electron-withdrawing group and / or an alkyl group, a nitrile, and a ketone, wherein the electron-withdrawing group includes at least one of a halogen, -NO2, -C≡N, -C=C, -C≡C, and -OCH3. Thus, by filling the polymer layer with this type of organic solvent, direct contact between the positive electrode active material and the electrolyte solvent in the battery can be effectively blocked, thereby avoiding oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0029] In some embodiments, the film-forming additive includes at least one of dioxalatoborate, difluorooxalatoborate, difluorophosphate, methyl trifluoroethyl carbonate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, and propylene trifluorocarbonate.

[0030] In some embodiments, the adsorption additive includes at least one of a carbonate ester, a phosphate ester, a nitrile, and an ionic liquid.

[0031] In some embodiments, the electrochemical oxidation window of the polymer is higher than 4 V. Thus, under conditions of high cut-off voltage (>4 V) and high rate charging, no oxidation reaction occurs on the positive electrode side, reducing the risk of battery overcharge.

[0032] In some embodiments, the polymer has a swelling degree of 5% to 2000%, and optionally 50% to 1500%. This improves the polymer's liquid retention properties, preventing direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0033] In some embodiments, the crosslink density of the polymer is 1%-100%, and optionally 30%-70%. This improves the polymer's liquid retention properties, preventing direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0034] In some embodiments, the polymer has a number average molecular weight of 10,000 to 1,000,000, and optionally 50,000 to 600,000. This improves the polymer's liquid absorption and retention properties, preventing direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0035] In some embodiments, the polymer comprises the following repeating units:

[0036] R1-R4 independently include H, alkyl, F, Cl, Br, I, C≡N, phenyl, pyrrolyl, pyrrolidone, sulfonic acid, sulfonate, benzenesulfonate, carboxylic acid, and carbonate.

[0037] Therefore, by filling the polymer with an organic solvent, the adsorption performance of the polymer for the organic solvent can be improved, effectively blocking the direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding the oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0038] In some embodiments, the repeating unit comprises at least one of the following structural formulas:

[0039] Therefore, by filling the polymer of this composition with an organic solvent, the adsorption performance of the polymer for the organic solvent can be improved, effectively blocking the direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding the oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharging.

[0040] In the second aspect of the present application, the present application provides a method for preparing a positive electrode plate, comprising: forming a positive electrode plate comprising a polymer and an organic solvent, wherein the polymer and the organic solvent are located on at least one side of the positive electrode plate away from the positive electrode current collector, the organic solvent is located in the polymer, and the electrochemical oxidation window of the organic solvent is higher than 4V.

[0041] Thus, the above-mentioned positive electrode sheet comprising a polymer and an organic solvent can be prepared, wherein the organic solvent is located within the polymer, and the polymer and the organic solvent are located on at least one side of the positive electrode sheet away from the positive electrode current collector. The polymer filled with the organic solvent can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo an oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, thereby no side reaction will occur on the positive electrode side, and under high rate charging, the organic solvent is not easily excited to oxidize and decompose, thereby not generating additional electrons to reach the negative electrode side, and thus the phenomenon of abnormal increase in battery charging capacity will not occur, thereby reducing the risk of battery overcharging.

[0042] In some embodiments, the method for forming a positive electrode sheet comprising a polymer and an organic solvent includes forming a positive electrode active material layer comprising positive electrode active particles on at least one side of the positive electrode current collector, and forming a polymer layer comprising the polymer and the organic solvent on the surface of the positive electrode active particles. Thus, by forming a polymer layer comprising the polymer and the organic solvent on the surface of the positive electrode active particles, the polymer layer can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0043] In some embodiments, the method for forming a positive electrode sheet comprising a polymer and an organic solvent includes: forming a positive electrode active material layer on at least one side of the positive electrode current collector; and forming a protective layer comprising a polymer and the organic solvent on at least one side of the positive electrode active material layer. Thus, by forming the protective layer comprising a polymer and an organic solvent on the positive electrode active material layer, the protective layer can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0044] A third aspect of the present application provides a battery, comprising the above-mentioned positive electrode plate.

[0045] In some embodiments, the battery includes an electrolyte, the electrolyte includes a main solvent, and the main solvent is different from the organic solvent in the positive electrode sheet.

[0046] In some embodiments, the battery comprises an electrolyte, and the electrochemical oxidation window of the main solvent is less than or equal to 4V.

[0047] A fourth aspect of the present application provides an electrical device, which includes the above-mentioned battery.

[0048] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0050] FIG1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application;

[0051] FIG2 is a schematic structural diagram of a positive electrode sheet according to another embodiment of the present application;

[0052] FIG3 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0053] FIG4 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0054] FIG5 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0055] FIG6 is an exploded view of FIG5;

[0056] FIG. 7 is a schematic diagram of an embodiment of an electric device using a battery as a power source.

[0057] Explanation of reference numerals: 100: positive electrode sheet; 11: positive electrode current collector; 12: positive electrode active material layer; 13: protective layer; 1: secondary battery; 2: battery module; 3: battery pack; 4: upper case; 5: lower case. DETAILED DESCRIPTION

[0058] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0059] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0060] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0061] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0063] With the technological development and increasing demand for electric vehicles and rechargeable mobile devices, secondary batteries, as a representative of the new energy field, have also seen rapid development in related research. As the application fields of power batteries continue to expand, their market demand is also constantly increasing.

[0064] The electrolyte plays the role of conducting ions between the positive and negative electrodes of secondary batteries. The electrolyte includes electrolyte salts and solvents. In order to promote the application of metal negative electrodes, electrolytes that are resistant to reduction and compatible with metal negative electrodes have been developed. However, the oxidation window of this type of electrolyte is difficult to adapt to high-voltage positive electrode materials. Under the condition of high cut-off voltage (>4V) charging, the solvent of this type of electrolyte is easily oxidized at the positive electrode interface, resulting in serious interfacial side reactions. At the same time, when charging at a high rate, the space charge effect on the positive electrode side is too strong, which stimulates the oxidative decomposition of the solvent. During the oxidation process of the solvent at the positive electrode interface, the solvent loses electrons. These electrons reach the negative electrode side through the external circuit, forming a loop, which is manifested as an increase in the battery charging capacity. However, these side reactions are irreversible. These electrons that reach the negative electrode side cannot return to the positive electrode during the battery discharge process, resulting in an abnormal increase in the charging capacity and a risk of overcharging.

[0065] In order to solve the above problems, the existing technology attempts to use oxidation-resistant electrolyte solvents to replace electrolyte solvents with lower electrochemical oxidation windows. However, since the oxidation-resistant electrolyte is not resistant to reduction, during the battery charging process, the oxidation-resistant electrolyte is prone to side reactions on the negative electrode side and deteriorate the negative electrode, thereby reducing the battery's cycle performance.

[0066] The present application adopts a positive electrode plate comprising a polymer and an organic solvent, wherein the organic solvent is located within the polymer. The polymer filled with the organic solvent can block direct contact between the positive electrode active material and the electrolyte solvent, thereby avoiding oxidative decomposition of the electrolyte solvent. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo an oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, thereby no side reaction will occur on the positive electrode side. Moreover, under high rate charging, the organic solvent is not easily excited to oxidize and decompose, thereby not generating additional electrons to reach the negative electrode side, thereby preventing an abnormal increase in the battery charging capacity and reducing the risk of overcharging.

[0067] The battery disclosed in the embodiments of the present application can be used in electrical devices that use the battery as a power source or various energy storage systems that use the battery as an energy storage element. The electrical device can be, but is not limited to, a mobile phone, a tablet, a laptop computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and the spacecraft can include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0068] In a first aspect, the present application provides a positive electrode plate, which includes a positive electrode collector. At least one side of the positive electrode plate away from the positive electrode collector includes a polymer and an organic solvent, wherein the organic solvent is located in the polymer, and the electrochemical oxidation window of the organic solvent is higher than 4V.

[0069] The present application adopts a positive electrode plate comprising a polymer and an organic solvent, wherein the organic solvent is located within the polymer, and the polymer and the organic solvent are located on at least one side of the positive electrode plate away from the positive electrode current collector. The polymer filled with the organic solvent can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo an oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, thereby no side reaction will occur on the positive electrode side. Moreover, under high rate charging, the organic solvent is not easily excited to undergo oxidative decomposition, thereby not generating additional electrons to reach the negative electrode side, and thus no abnormal increase in the battery charging capacity will occur, thereby reducing the risk of battery overcharging.

[0070] In this application, the term "electrochemical oxidation window" refers to the potential range in which no redox reaction occurs during voltammetry testing. The higher the electrochemical oxidation window of an organic solvent, the higher the oxidation potential of the corresponding organic solvent, i.e., the organic solvent is less likely to be oxidized. Furthermore, in order to reduce side reactions of the organic solvent on the positive electrode side, the electrochemical oxidation window of the organic solvent used in this application is higher than the cutoff voltage during the battery charging process. Furthermore, the test methods for the "electrochemical oxidation window of an organic solvent" in this application include cyclic voltammetry and linear sweep voltammetry.

[0071] In the present application, "at least one side of the positive electrode sheet away from the positive electrode current collector includes a polymer and an organic solvent" can be understood as: when the positive electrode current collector is coated on one side, the polymer and the organic solvent are located on the side of the coating layer away from the positive electrode current collector; when the positive electrode current collector is coated on both sides, the polymer and the organic solvent are located on the side of one coating layer or both sides of the coating layer away from the positive electrode current collector.

[0072] In some embodiments of the present application, referring to Figure 1, the positive electrode sheet 100 includes a positive electrode current collector 11 and a positive electrode active material layer 12, the positive electrode active material layer 12 is provided on at least one side of the positive electrode current collector 11, the positive electrode active material layer 12 includes positive electrode active particles, the surface of the positive electrode active particles has a polymer layer, and the polymer layer includes the polymer and the organic solvent.

[0073] It should be noted that, in the present application, “the organic solvent is located in the polymer” means that the polymer absorbs or adsorbs the organic solvent in its molecular network by utilizing its swelling properties.

[0074] The present application forms a polymer layer including a polymer and an organic solvent on the surface of the positive electrode active particles. The polymer layer can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, so that no side reaction will occur on the positive electrode side. Moreover, under high rate charging, the organic solvent is not easily excited to oxidize and decompose, so that no additional electrons will be generated to reach the negative electrode side, and thus the phenomenon of abnormal increase in battery charging capacity will not occur, thereby reducing the risk of battery overcharge.

[0075] In some embodiments of the present application, the positive electrode current collector 11 can be a conventional metal foil or a composite positive electrode current collector (a metal material can be disposed on a polymer substrate to form a composite positive electrode current collector). As an example, the positive electrode current collector 11 can include one or more of aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil.

[0076] In some embodiments of the present application, the specific type of the positive electrode active particle material is not limited, and active materials known in the art that can be used for battery positive electrodes can be used. Those skilled in the art can select according to actual needs.

[0077] For example, when the battery is a lithium-ion battery, as an example, the positive electrode active particle material may include, but is not limited to, one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds. These materials can all be obtained through commercial channels.

[0078] For example, when the battery is a sodium ion battery, as an example, the positive electrode active particle material may include, but is not limited to, at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analog.

[0079] Examples of the layered transition metal oxides include:

[0080] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 One or more of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn and Ba, 0 <x≤0.33,0<h≤0.24,0≤k≤0.32,0<l≤0.68,0≤m<0.1,h+k+l+m=1,0≤y<0.2;

[0081] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 is one or more of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn and Ba, 0 <z≤0.1;

[0082] Na a Lib Ni c Mn d Fe e O₂, where 0.67 < a ≤ 1, 0 < b < 0.2, 0 < c < 0.3, 0.67 < d + e < 0.8, and b + c + d + e = 1.

[0083] Examples of the above polyanion compounds include, for example:

[0084] A 1 f M 3 g (PO₄) i O j X 1 3-j , where A 1 is one or more of H, Li, Na, K, and NH₄, M 3 is one or more of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, X 1 is one or more of F, Cl, and Br, 0 < f ≤ 4, 0 < g ≤ 2, 1 ≤ i ≤ 3, 0 ≤ j ≤ 2;

[0085] Na n M 4 PO₄X 2 , where M 4 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, X 2 is one or more of F, Cl, and Br, 0 < n ≤ 2;

[0086] Na p M 5 q (SO₄)₃, where M 5 is one or more of Mn, Fe, Co, Ni, Cu, and Zn, 0 < p ≤ 2, 0 < q ≤ 2;

[0087] Na s Mn t Fe 3-t (PO₄)₂(P₂O₇), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2, or 3.

[0088] Examples of the above Prussian blue analogs include, for example: <{

[0089] A u M 6 v [M 7 (CN)₆] w ·xH₂O, where A is H+ , NH4 + , one or more of alkali metal cations and alkaline earth metal cations, M 6 and M 7 are each independently one or more of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A is H + , Li + , Na + , K + , NH4 + , Rb + , Cs + , Fr + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ and Ra 2+ one or more of, M 6 and M 7 are each independently cations of one or more transition metal elements selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn and W.

[0090] The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0091] The positive electrode active material layer usually further optionally includes at least one of a binder and a conductive agent. The conductive agent is used to improve the conductivity of the positive electrode active material layer, and the binder is used to firmly bond the positive electrode active material and the binder to the positive electrode current collector. The types of the conductive agent and the binder are not specifically limited in this application and can be selected according to actual needs.

[0092] As an example, the conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers.

[0093] As an example, the binder can include one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).

[0094] In some embodiments of the present application, the mass ratio of the positive electrode active particles to the binder and the conductive agent is (90-100): (0-5): (0-5), for example (92-99): (0-5): (0-5), (94-98): (0-5): (0-5), (95-97): (0-5): (0-5), (95-96): (0-5): (0-5), (90-100): (0.5-5): ( 0-5), (90-100): (1-4): (0-5), (90-100): (2-3): (0-5), (90-100): (0-5): (0.5-5), (90-100): (0-5): (1-4), (90-100): (0-5): (1-3), (90-100): (0-5): (1-2), (96-99): (0.5-1): (0.5-1), etc. In some embodiments of the present application, the mass ratio of the positive electrode active particles to the binder and the conductive agent is (95-98.5): (0.5-2): (0.5-2). Therefore, by using the positive electrode active particles, conductive agent and binder in the proportions of the present application to form a positive electrode slurry, the conductivity of the positive electrode active material layer and the bonding strength with the positive electrode current collector can be improved.

[0095] In some embodiments of the present application, the thickness of the positive electrode active material layer 11 in the positive electrode sheet 100 may be 30 μm to 60 μm, for example, 30 μm to 58 μm, 30 μm to 55 μm, 30 μm to 52 μm, 30 μm to 50 μm, 32 μm to 48 μm, 35 μm to 45 μm, 38 μm to 42 μm, 40 μm to 42 μm, etc. Thus, a positive electrode active material layer of this thickness can increase the energy density of the battery. In other embodiments of the present application, the thickness of the positive electrode active material layer 11 may be 30 μm to 50 μm.

[0096] In some embodiments of the present application, the thickness of the polymer layer formed on the surface of the positive electrode active particles may be 0.01 μm-2 μm, for example, 0.01 μm-1.8 μm, 0.02 μm-1.6 μm, 0.05 μm-1.5 μm, 0.08 μm-1.2 μm, 0.1 μm-1 μm, 0.1 μm-0.8 μm, 0.1 μm-0.6 μm, 0.1 μm-0.5 μm, 0.1 μm-0.4 μm, 0.1 μm-0.34 μm, 0.1 μm-0.2 μm, etc. In other embodiments of the present application, the thickness of the polymer layer formed on the surface of the positive electrode active particles may be 0.01 μm-1 μm. Therefore, the formation of a polymer layer of this thickness on the surface of the positive electrode active particles can not only effectively block the direct contact between the positive electrode active material and the electrolyte solvent in the battery, avoiding the oxidative decomposition of the electrolyte solvent, but also reduce the impedance of the positive electrode sheet.

[0097] In some embodiments of the present application, the mass ratio of the polymer to the organic solvent in the polymer layer can be (0.1-99): (1-99.9), for example, (0.5-98): (1-99.9), (1-97): (1-99.9), (5-95): (1-99.9), (10-90): (1-99.9), (15-85): (1-99.9), (20-80): (1-99.9), (25-75): (1-99.9), (30-70): (1-99.9), (40-6 99): (50-60), (0.1-99): (50-60), (0.1-99): (50-60), (0.1-99): (50-60), etc. In some other embodiments of the present application, the mass ratio of the polymer to the organic solvent in the polymer layer may be (0.1-15): (85-99.9). Therefore, using the above-mentioned ratio of polymer and organic solvent to form a polymer layer on the surface of the positive electrode active particles can effectively block the direct contact between the positive electrode active material and the electrolyte solvent in the battery, avoid oxidative decomposition of the electrolyte solvent, and reduce the risk of battery overcharge.

[0098] In some embodiments of the present application, the organic solvent includes carbonate, carboxylate, C5-C 16At least one of an alkane, an aromatic hydrocarbon having an electron-withdrawing group and / or an alkyl group, a nitrile and a ketone, wherein the electron-withdrawing group comprises at least one of halogen, -NO2, -C≡N, -C=C, -C≡C and -OCH3.

[0099] As an example, the carbonate includes but is not limited to at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, and butylene carbonate; the carboxylate includes but is not limited to at least one of propyl butyrate, propyl acetate, isopropyl acetate, ethyl propionate, propyl propionate, butyl propionate, isopropyl propionate, and ethyl butyrate; C5-C 16 The alkane represents an alkane having 5 to 16 carbon atoms, including but not limited to n-pentane, isopentane, neopentane, n-hexane, isohexane, 3-methylpentane, 2,3-dimethylbutane, 2,2-dimethylbutane, n-heptane, 2-methylhexane, 3-methylhexane, 2,4-dimethylpentane, 2,3-dimethylpentane, 2,2-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, 2,2,3-trimethylbutane, n-octane, 2-methylheptane, 3-methylheptane, 4-methylheptane, 2,2-dimethylhexane, 3,3-dimethylhexane, 2,3-dimethylpentane, At least one of methylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane, 3,4-dimethylhexane, nonane, 2-methyloctane, 3-methyloctane, 4-methyloctane, 3-ethylheptane, 4-ethylheptane, 2,2-dimethylheptane, 2,3-dimethylheptane, n-decane, 2-methylnonane, 3-methylnonane, 4-methylnonane, 3-ethyloctane, 2,3-dimethyldecane, 2,4-dimethyldecane, 2,2,3-trimethylquinane, 2,2,3,3-tetramethylquinane, 4,4-diethylquinane and 3,4,4-triethylquinane.

[0100] As an example, the role of the electron-withdrawing group in the aromatic hydrocarbon having an electron-withdrawing group and / or an alkyl group is to improve the antioxidant properties of the organic solvent, and the role of the alkyl group is to lower the melting point of the aromatic hydrocarbon and improve its boiling point and oxidation resistance, and the alkyl group may include a C1-C5 alkyl group, and the C1-C5 alkyl group can be understood as an alkyl group with 1-5 carbon atoms, such as methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3) 2), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), etc., and the aromatic hydrocarbons having electron-withdrawing groups and / or alkyl groups may include but are not limited to at least one of chlorobenzene, bromobenzene, iodobenzene, fluorobenzene, nitrobenzene, cyanobenzene, styrene, phenylacetylene, anisole, toluene, ethylbenzene, propylbenzene, p-chlorotoluene, m-chlorotoluene, 1,2-dimethyl-3-ethylbenzene, butylbenzene, p-chlorobutylbenzene, pentylbenzene, etc.

[0101] As an example, the nitrile may include but is not limited to at least one of acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, 3-methoxypropionitrile and cyclopentanenitrile; the ketone may include but is not limited to at least one of acetone, methyl butyl ketone and methyl isobutyl ketone, etc.

[0102] Therefore, by filling the polymer layer with the above-mentioned type of organic solvent, direct contact between the positive electrode active material and the electrolyte solvent in the battery can be effectively blocked, thereby avoiding oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge. At the same time, the electrochemical oxidation window of this type of organic solvent is higher than 4V, that is, the organic solvent will not undergo oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, so no side reaction will occur on the positive electrode side. Moreover, under high-rate charging, this type of organic solvent is not easily excited to oxidize and decompose, so that no additional electrons will be generated to reach the negative electrode side, and thus the phenomenon of abnormal increase in battery charging capacity will not occur, reducing the risk of battery overcharge.

[0103] In some embodiments of the present application, the electrochemical oxidation window of the polymer in the polymer layer is higher than 4 V. Thus, under conditions of high cut-off voltage (>4 V) and high rate charging, no oxidation reaction occurs on the positive electrode side, reducing the risk of battery overcharge.

[0104] In this application, the test method for the "electrochemical oxidation window of polymers" can refer to the test method for the "electrochemical oxidation window of organic solvents" described above. Furthermore, to reduce side reactions on the positive electrode side, the polymers used in this application have an electrochemical oxidation window that is higher than the cutoff voltage during the battery charging process.

[0105] In some embodiments of the present application, the swelling degree of the polymer is 5%-2000%, for example, 10%-1990%, 50%-1900%, 70%-1800%, 100%-1700%, 150%-1600%, 200%-1500%, 300%-1400%, 400%-1300%, 500%-1200%, 600%-1100%, 700%-1000%, 800%-900%, etc. In other embodiments of the present application, the swelling degree of the polymer is 50%-1500%.

[0106] In this way, the polymer's ability to adsorb organic solvents can be enhanced, thereby delaying the migration of electrolyte solvents into the polymer layer, thereby reducing the risk of battery overcharge.

[0107] In this application, the method for detecting the swelling degree of the polymer is:

[0108] The polymer was scraped onto a glass plate, and a 1 cm × 1 cm polymer film was taken and weighed with a precision balance to obtain an initial mass M1. The polymer film was added into dimethyl carbonate and soaked for 12 h. After being taken out, the mass M2 of the polymer film was weighed, and the weight gain was M2-M1.

[0109] The polymer swelling degree (C) is calculated according to the following formula: C = (M2-M1) / M1 x 100%.

[0110] In some embodiments of the present application, the crosslink density of the polymer is 1%-100%, for example, 3%-99%, 5%-98%, 7%-97%, 10%-96%, 15%-96%, 20%-95%, 25%-90%, 30%-85%, 35%-80%, 40%-75%, 45%-70%, 50%-65%, 55%-60%, etc. In some embodiments of the present application, the crosslink density of the polymer is 30%-70%. This can improve the liquid absorption and retention properties of the polymer, block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0111] In this application, "crosslink density of a polymer" is a physical quantity used to indicate the degree of crosslinking of a polymer, i.e., the fraction of crosslinked structural units Nc in the crosslinked chain to the total structural units N. The crosslink density can be measured using a nuclear magnetic crosslink density analyzer. Specifically, in the examples of this application, an IIC XLDS-15 crosslink density spectrometer can be used for measurement.

[0112] In some embodiments of the present application, the number average molecular weight of the polymer is 10,000-1,000,000, for example, 50,000-950,000, 100,000-900,000, 150,000-850,000, 200,000-800,000, 250,000-750,000, 300,000-700,000, 350,000-650,000, 400,000-600,000, 450,000-550,000, 450,000-500,000, etc. In other embodiments of the present application, the number average molecular weight of the polymer is 50,000-600,000.

[0113] In the present application, "the number average molecular weight of the polymer" can be tested by gel permeation chromatography.

[0114] In some embodiments of the present application, the polymer comprises the following repeating units:

[0115] R1-R4 independently include H, alkyl, F, Cl, Br, I, C≡N, phenyl, pyrrolyl, pyrrolidone, sulfonic acid, sulfonate, benzenesulfonate, carboxylic acid, and carbonic acid. In the present application, "alkyl" is a hydrocarbon group formed by losing one hydrogen atom in an alkane molecule, such as methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), isopentyl (-CH(CH3)CH2CH2CH3), 2-methylbutyl (-CH2CH(CH3)CH2CH3), n-hexyl (CH3(CH2)4CH2-), 2-methyl-pentyl (-CH3CH2CH2CH(CH3)2), etc. "Sulfonate" may include sodium sulfonate. The "benzenesulfonate group" may include a sodium benzenesulfonate group.

[0116] As an example, the repeating unit includes at least one of the following structural formulas:

[0117] Therefore, by filling the polymer with an organic solvent, the direct contact between the positive electrode active material and the electrolyte solvent in the battery can be effectively blocked, thereby avoiding the oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0118] In some embodiments of the present application, the polymer layer may further include an electrolyte salt, thereby improving the ion conductivity of the polymer layer.

[0119] In the present application, when the battery is a lithium-ion battery, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0120] When the battery is a sodium ion battery, as an example, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate and sodium bis(trifluoromethylsulfonyl)imide.

[0121] In some embodiments of the present application, based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt may be 0.1mol / L-10mol / L, for example, 0.5mol / L-9.5mol / L, 1mol / L-9mol / L, 1.5mol / L-8.5mol / L, 2mol / L-8mol / L, 2.5mol / L-7.5mol / L, 3mol / L-7mol / L, 3.5mol / L-6.5mol / L, 4mol / L-6mol / L, 4.5mol / L-5.5mol / L, 4.8mol / L-5mol / L, etc. In other embodiments of the present application, based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt may be 0.5mol / L-5mol / L. Thus, by adding the above-mentioned concentration of electrolyte salt to the polymer layer, the ion conductivity of the polymer layer can be improved.

[0122] In some embodiments of the present application, the polymer layer further includes at least one of a film-forming additive and an adsorption additive, wherein the electrochemical oxidation window of the film-forming additive is lower than or equal to 4V, and the electrochemical oxidation window of the adsorption additive is higher than 4V. Thus, by adopting a film-forming additive with an electrochemical oxidation window lower than or equal to 4V, under the condition of charging at a high cut-off voltage (>4V), the film-forming additive is oxidatively decomposed on the positive electrode side, thereby forming a protective film on the surface of the positive electrode active particles. The protective film can further block the direct contact between the positive electrode active material and the electrolyte solvent in the battery, avoid the oxidative decomposition of the electrolyte solvent, and reduce the risk of battery overcharge. The adsorption additive can be adsorbed on the surface of the positive electrode active material, inhibit the change of the interface structure of the positive electrode active material, and improve the cycle stability of the positive electrode sheet. In addition, the present application adopts an adsorption additive with an electrochemical oxidation window higher than 4V, which can reduce the oxidation reaction of the adsorption additive on the positive electrode side and reduce the risk of battery overcharge.

[0123] In this application, the test method for the "electrochemical oxidation window of film-forming additives and adsorption additives" can refer to the test method for the "electrochemical oxidation window of organic solvents" described above. In order to reduce side reactions on the positive electrode side, the adsorption additives used in this application have an electrochemical oxidation window higher than the cutoff voltage during the battery charging process.

[0124] In some embodiments of the present application, the mass ratio of the polymer to the film-forming additive and the adsorption additive in the polymer layer can be (10-100): (0-90): (0-90), for example, (20-90): (0-90): (0-90), (30-80): (0-90): (0-90), (40-70): (0-90): (0-90), (50-60): (0-90): (0-90), (10-100): (10-80): (0-90), (10-100): (20-70): (0-90), (10 -100): (30-60): (0-90), (10-100): (40-50): (0-90), (10-100): (0-90): (10-80), (10-100): (0-90): (20-70), (10-100): (0-90): (30-60), (10-100): (0-90): (40-50), etc. In some other embodiments of the present application, the mass ratio of the polymer to the film-forming additive and the adsorption additive in the polymer layer is (30-80): (20-70): (20-70). Therefore, by adopting the polymer layer composed of the above, on the one hand, the cycle stability of the positive electrode sheet can be improved, and on the other hand, the side reaction on the positive electrode side can be reduced, thereby reducing the risk of battery overcharge.

[0125] As an example, the film-forming additive includes but is not limited to at least one of dioxalatoborate, difluorooxalatoborate, difluorophosphate, methyl trifluoroethyl carbonate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate and trifluoropropylene carbonate. For example, when the battery is a lithium ion battery, dioxalatoborate, difluorooxalatoborate and difluorophosphate use corresponding lithium salts, i.e., lithium dioxalatoborate, lithium difluorooxalatoborate and lithium difluorophosphate. When the battery is a sodium ion battery, dioxalatoborate, difluorooxalatoborate and difluorophosphate use corresponding sodium salts, i.e., dioxalatoborate, lithium difluorooxalatoborate and lithium difluorophosphate. Sodium oxalatoborate, sodium difluorooxalatoborate, sodium difluorophosphate; the adsorption additive includes but is not limited to at least one of carbonates, phosphates, nitriles and ionic liquids, for example, carbonates include but are not limited to at least one of ethyl methyl carbonate, ethylene carbonate and propylene carbonate, phosphates include but are not limited to at least one of dimethyl phenylphosphonate and dimethyl benzylphosphonate, nitriles include but are not limited to at least one of acetonitrile and succinonitrile, and ionic liquids include but are not limited to 1-butyl-3-methylimidazolium hexafluorophosphate, such as 1-butyl-3-methylimidazolium lithium hexafluorophosphate or 1-butyl-3-methylimidazolium sodium hexafluorophosphate.

[0126] In some embodiments of the present application, referring to Figure 2, the positive electrode plate 100 of the present application includes a positive electrode current collector 11, a positive electrode active material layer 12 and a protective layer 13, the positive electrode active material layer 12 is provided on at least one side of the positive electrode current collector 11, the protective layer 13 is provided on at least one side of the positive electrode active material layer 12, and the protective layer 12 includes the polymer and the organic solvent.

[0127] Thus, by forming a protective layer 13 comprising a polymer and an organic solvent on the positive electrode active material layer 12, the protective layer 13 can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo an oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, so that no side reaction will occur on the positive electrode side, and under high rate charging, the organic solvent is not easily excited to oxidize and decompose, so that no additional electrons will be generated to reach the negative electrode side, and thus the phenomenon of abnormal increase in battery charging capacity will not occur, reducing the risk of battery overcharge.

[0128] In some embodiments of the present application, the thickness of the protective layer 13 may be 0.1 μm-40 μm, for example, 0.5 μm-40 μm, 1 μm-38 μm, 2 μm-35 μm, 3 μm-32 μm, 4 μm-30 μm, 5 μm-28 μm, 6 μm-25 μm, 7 μm-23 μm, 8 μm-20 μm, 9 μm-18 μm, 10 μm-16 μm, 12 μm-15 μm, etc. In other embodiments of the present application, the thickness of the protective layer 13 may be 1 μm-20 μm, and further, the thickness of the protective layer 13 may be 1 μm-10 μm. Thus, forming a protective layer 13 of this thickness on the surface of the positive electrode active material layer 12 can not only block direct contact between the positive electrode active material and the electrolyte solvent in the battery, avoiding oxidative decomposition of the electrolyte solvent, but also reduce the impedance of the positive electrode sheet.

[0129] In some embodiments of the present application, the mass ratio of the polymer to the organic solvent in the protective layer 13 can be (0.1-99): (1-99.9), for example, (0.5-98): (1-99.9), (1-97): (1-99.9), (5-95): (1-99.9), (10-90): (1-99.9), (15-85): (1-99.9), (20-80): (1-99.9), (25-75): (1-99.9), (30-70): (1-99.9), (40- 60): (1-99.9), (50-60): (1-99.9), (0.1-99): (2-99), (0.1-99): (4-97), (0.1-99): (5-95), (0.1-99): (10-90), (0.1-99): (15-85), (0.1-99): (20-80), (0.1-99): (25-75), (0.1-99): (30-70), (0.1-99): (40-60), (0.1-99): (50-60), etc. In other embodiments of the present application, in the protective layer 13, the mass ratio of the polymer to the organic solvent can be (0.1-15): (85-99.9). In this way, the direct contact between the positive electrode active material and the electrolyte solvent in the battery can be effectively blocked, the oxidative decomposition of the electrolyte solvent can be avoided, and the risk of battery overcharge can be reduced.

[0130] In some embodiments of the present application, the protective layer 13 may further include an electrolyte salt, thereby improving the ion conductivity of the protective layer.

[0131] In some embodiments of the present application, based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt in the protective layer 13 is 0.1mol / L-10mol / L, for example, 0.5mol / L-9.5mol / L, 1mol / L-9mol / L, 1.5mol / L-8.5mol / L, 2mol / L-8mol / L, 2.5mol / L-7.5mol / L, 3mol / L-7mol / L, 3.5mol / L-6.5mol / L, 4mol / L-6mol / L, 4.5mol / L-5.5mol / L, 4.8mol / L-5mol / L, etc. In other embodiments of the present application, based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt can be 0.5mol / -5mol / L. Thus, by adding the above-mentioned concentration of electrolyte salt to the protective layer, the ion conductivity of the protective layer can be improved.

[0132] In some embodiments of the present application, the protective layer 13 further comprises at least one of a film-forming additive and an adsorption additive, thereby improving the cycle stability of the positive electrode sheet.

[0133] In some embodiments of the present application, the mass ratio of the polymer to the film-forming additive and the adsorption additive in the protective layer 13 is (10-100): (0-90): (0-90), for example, (20-90): (0-90): (0-90), (30-80): (0-90): (0-90), (40-70): (0-90): (0-90), (50-60): (0-90): (0-90), (10-100): (10-80): (0-90), (10-100): (20-70): (0-90), (10- 100): (30-60): (0-90), (10-100): (40-50): (0-90), (10-100): (0-90): (10-80), (10-100): (0-90): (20-70), (10-100): (0-90): (30-60), (10-100): (0-90): (40-50), etc. In some other embodiments of the present application, the mass ratio of the polymer to the film-forming additive and the adsorption additive in the protective layer 13 is (30-80): (20-70): (20-70). Therefore, by adopting the protective layer composed of the above, on the one hand, the cycle stability of the positive electrode sheet can be improved, and on the other hand, the side reaction on the positive electrode side can be reduced, thereby reducing the risk of battery overcharge.

[0134] In the present application, the composition and mixing ratio of the positive electrode active material particles, binder and conductive agent in the positive electrode active material layer 12 of Figure 2 and the composition of the organic solvent, polymer, electrolyte salt, adsorption additive and film-forming additive in the protective layer 13 are the same as described above and will not be repeated here.

[0135] In some embodiments of the present application, the protective layer 13 shown in FIG. 2 can be formed on the positive electrode active material layer 12 shown in FIG. 1 , that is, a polymer layer comprising a polymer and an organic solvent is formed on the surface of the positive electrode active particles in the positive electrode active material layer 12, and then the protective layer 13 comprising a polymer and an organic solvent is formed on the positive electrode active material layer 12. Thus, both the protective layer 13 on the surface of the positive electrode sheet and the polymer layer on the surface of the positive electrode active particles can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby preventing oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0136] In the second aspect of the present application, the present application provides a method for preparing a positive electrode plate, comprising: forming a positive electrode plate comprising a polymer and an organic solvent, wherein the polymer and the organic solvent are located on at least one side of the positive electrode plate away from the positive electrode current collector, the organic solvent is located in the polymer, and the electrochemical oxidation window of the organic solvent is higher than 4V.

[0137] Thus, the above-mentioned positive electrode sheet comprising a polymer and an organic solvent can be prepared, wherein the organic solvent is located within the polymer, and the polymer and the organic solvent are located on at least one side of the positive electrode sheet away from the positive electrode current collector. The polymer filled with the organic solvent can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent. At the same time, since the electrochemical oxidation window of the organic solvent is higher than 4V, that is, the organic solvent will not undergo an oxidation reaction on the positive electrode side under the condition of high cut-off voltage (>4V) charging, thereby no side reaction will occur on the positive electrode side, and under high rate charging, the organic solvent is not easily excited to oxidize and decompose, thereby not generating additional electrons to reach the negative electrode side, and thus the phenomenon of abnormal increase in battery charging capacity will not occur, thereby reducing the risk of battery overcharging.

[0138] In some embodiments of the present application, the method for preparing a positive electrode sheet may include: forming a positive active material layer including positive active particles on at least one side of the positive current collector, and forming a polymer layer including the polymer and the organic solvent on the surface of the positive active particles.

[0139] As an example, the polymer and the positive electrode active particles are pre-mixed so that the polymer is coated on the surface of the positive electrode active particles, and then the coated positive electrode active particles are mixed with a conductive agent, a binder and a solvent NMP (N-methylpyrrolidone), or the polymer and the positive electrode active particles are directly mixed with a conductive agent, a binder and a solvent NMP (N-methylpyrrolidone), and then the positive electrode slurry is coated on the positive electrode current collector, and then the solvent NMP is removed by roller coating and drying, and finally an organic solvent is applied to the positive electrode plate by immersion, spraying or dripping, and the organic solvent enters the polymer to form a polymer layer on the surface of the positive electrode active particles, wherein the electrolyte salt, adsorption additive and film-forming additive can be introduced into the polymer layer by adding them to the organic solvent.

[0140] Therefore, by forming a polymer layer including a polymer and an organic solvent on the surface of the positive electrode active particles, the polymer layer can block the direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding the oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0141] In some embodiments of the present application, the method for preparing a positive electrode sheet may further include: forming a positive active material layer on at least one side of the positive current collector; and forming a protective layer comprising a polymer and the organic solvent on at least one side of the positive active material layer.

[0142] As an example, a positive electrode slurry obtained by mixing positive electrode active particles with a conductive agent, a binder and a solvent NMP (N-methylpyrrolidone) is coated on the positive electrode current collector, and then a mixed solution including an organic solvent and a polymer is coated on the positive electrode slurry layer, and the solvent NMP and the organic solvent are removed by roller coating and drying, or a positive electrode slurry obtained by mixing positive electrode active particles with a conductive agent, a binder and a solvent NMP (N-methylpyrrolidone) is coated on the positive electrode current collector, and then the solvent NMP is removed by roller coating and drying to form a positive electrode active material layer on the positive electrode current collector, and then a mixed solution including an organic solvent and a polymer is coated on the positive electrode active material layer, and the organic solvent is removed by roller coating and drying to form a positive electrode active material layer and a polymer layer on the surface of the positive electrode current collector in sequence, and finally the organic solvent is applied to the positive electrode sheet by immersion, spraying or dripping, and the organic solvent enters the polymer layer to form a protective layer, wherein the electrolyte salt, adsorption additive and film-forming additive can be introduced into the protective layer by adding them to the organic solvent.

[0143] Therefore, by forming a protective layer including a polymer and an organic solvent on the positive electrode active material layer, the protective layer can block direct contact between the positive electrode active material and the electrolyte solvent in the battery, thereby avoiding oxidative decomposition of the electrolyte solvent and reducing the risk of battery overcharge.

[0144] A third aspect of the present application provides a battery, which includes the positive electrode sheet of the first aspect or the positive electrode sheet obtained by the method of the second aspect.

[0145] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0146] It is understandable that the battery proposed in this application can be a lithium-ion battery or a sodium-ion battery.

[0147] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to isolate them. The electrolyte conducts ions between the positive and negative electrodes.

[0148] [Negative electrode]

[0149] In a battery, the negative electrode plate generally includes a negative electrode positive current collector and a negative electrode active material layer disposed on the negative electrode positive current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0150] The negative electrode sheet may also include only the negative electrode and positive electrode current collectors, i.e., without the negative electrode active material. Alternatively, the negative electrode sheet may include a pre-deposited metal phase on the negative electrode and positive electrode current collectors. The negative electrode and positive electrode current collectors may be made of conventional metal foil, carbon-coated metal foil, or porous metal sheet. For example, the negative electrode and positive electrode current collectors may be copper foil or aluminum foil.

[0151] There is no limitation on the specific type of the negative electrode active material, and active materials known in the art that can be used for the negative electrode of secondary batteries can be used, and those skilled in the art can select according to actual needs. As an example, the negative electrode active material may include but is not limited to one or more of lithium metal, sodium metal, carbon material, alloy material, transition metal oxide and / or sulfide, phosphorus-based material, and titanate material. Specifically, the carbon material may include one or more of hard carbon, soft carbon, amorphous carbon, and nanostructured carbon material; the alloy material may include an alloy material formed by one or more of Si, Ge, Sn, Pb, and Sb; the general formula of the transition metal oxide and sulfide is M x N y , wherein M includes one or more of Fe, Co, Ni, Mn, Sn, Mo, Sb, and V, and N includes O or S; the phosphorus-based material may include one or more of red phosphorus, white phosphorus, and black phosphorus; the titanate material may include Na2Ti3O7, Na2Ti6O 13 、Na4Ti5O 12 、Li4Ti5O 12, NaTi2(PO4)3. These materials can be obtained through commercial channels.

[0152] The negative electrode active material layer typically also optionally includes a binder and a conductive agent. The conductive agent is used to improve the conductivity of the negative electrode active material layer, and the binder is used to firmly bond the negative electrode active material and the binder to the negative electrode current collector. This application does not specifically limit the types of conductive agent and binder, and they can be selected according to actual needs.

[0153] As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0154] As an example, the binder may include one or more of styrene-butadiene rubber (SBR), styrene-butadiene rubber (SBCs), water-based acrylic resin, and carboxymethyl cellulose (CMC).

[0155] The negative electrode active material layer may also optionally include a thickener, such as carboxymethyl cellulose (CMC). However, the present application is not limited thereto, and other materials that can be used as thickeners for the negative electrode sheet of a secondary battery may also be used in the present application.

[0156] [Isolation film]

[0157] As the above-mentioned isolation membrane, the present application has no special restrictions, and any well-known porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs. For example, it can be a single-layer or multi-layer film containing one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0158] [Electrolyte]

[0159] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The electrolyte used in the battery of the present application includes a main solvent, which is different from the organic solvent in the positive electrode sheet.

[0160] In some embodiments of the present application, the electrochemical oxidation window of the main solvent is lower than or equal to 4V, so that during the battery charging process, the electrolyte of this composition is not prone to side reactions on the negative electrode side and deterioration of the negative electrode, thereby improving the cycle performance of the battery.

[0161] In this application, the test of “electrochemical oxidation window of main solvent” can refer to the test method of “electrochemical oxidation window of organic solvent” mentioned above.

[0162] As an example, the main solvent may include ether and or fluoroether, such as at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, crown ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluoro-n-butyl ether, and octafluoropentyl-tetrafluoroethyl ether.

[0163] As an example, the electrolyte used in the battery of the present application also includes an electrolyte salt, which is the same as described above and will not be repeated here.

[0164] The embodiment of the present application has no particular limitation on the shape of the battery, which can be cylindrical, square or any other shape. FIG3 shows a secondary battery 1 with a square structure as an example.

[0165] In some embodiments, the secondary battery may include an outer packaging for encapsulating the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0166] In some embodiments, the outer packaging may include a housing and a cover. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover may be positioned over the opening to seal the receiving cavity.

[0167] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly. The electrode assembly is encapsulated in the housing. The electrolyte can be an electrolyte solution, which is impregnated into the electrode assembly. The number of electrode assemblies in a sodium-ion battery can be one or more, and can be adjusted according to demand.

[0168] In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0169] The outer packaging of the battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0170] In some embodiments, batteries may be assembled into a battery module. The battery module may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0171] Figure 4 shows an example battery module 2. Referring to Figure 4 , within the battery module 2, multiple batteries 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple batteries 1 may be secured together using fasteners.

[0172] The battery module 2 may further include a housing having a housing space, wherein the housing space accommodates a plurality of batteries 1. In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0173] Figures 5 and 6 illustrate an example battery pack 3. Referring to Figures 5 and 6 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 4 and a lower case 5. The upper case 4 can be placed over the lower case 5 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0174] [Electrical devices]

[0175] The present application also provides an electrical device, which includes at least one of the above-mentioned battery, battery module and battery pack. The battery, battery module or battery pack can serve as a power source for the electrical device, and can also serve as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck), an electric train, a ship, a satellite, and an energy storage system.

[0176] The electrical device may select a battery, a battery module or a battery pack according to its usage requirements.

[0177] Figure 7 shows an example of an electric device. This device includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery 7, a battery pack or battery module can be used.

[0178] As another example, an electric device may include a mobile phone, a tablet computer, or a laptop computer. Such an electric device is generally required to be thin and light, and may use a battery as a power source.

[0179] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0180] Example 1

[0181] 1. Preparation of positive electrode sheet

[0182] The positive electrode active particles LiNi 0.8 Co 0.1 Mn 0.1 O2 is pre-mixed with polyacrylonitrile so that the polymer is coated on the surface of the positive electrode active particles, and then the coated positive electrode active particles are mixed with the conductive agent carbon black, the binder polyvinylidene fluoride and the solvent NMP to obtain the positive electrode slurry (positive electrode active particles LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 to polyacrylonitrile, conductive agent carbon black, and adhesive polyvinylidene fluoride is 97.5:0.5:1:1, and the solid content of the positive electrode slurry is 60%. The positive electrode slurry is coated on the upper and lower surfaces of the positive electrode current collector carbon-coated aluminum foil, and then the solvent NMP is removed by roller coating and drying to form a positive electrode active material layer with a thickness of 40 μm on the copper foil. Finally, the obtained electrode is immersed in a mixed solution including an electrolyte salt, an organic solvent, an adsorption additive and a film-forming additive. The organic solvent, the adsorption additive and the film-forming additive are immersed in the polymer on the surface of the positive electrode active particles to form a polymer layer to obtain a positive electrode sheet, wherein the composition and content of the polymer, organic solvent, adsorption additive and film-forming additive are shown in Table 1.

[0183] 2. Preparation of negative electrode sheet

[0184] Graphite and binder sodium carboxymethyl cellulose are added to water in a mass ratio of 4:1.6 and stirred to form a uniform negative electrode slurry. The negative electrode slurry is coated on the upper and lower surfaces of the copper foil, and then transferred to a vacuum drying oven for complete drying, and then punched to obtain the negative electrode sheet.

[0185] 3. Preparation of electrolyte

[0186] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), lithium salt lithium bis(fluorosulfonyl)imide LiFSI was dissolved in a mixed solvent of organic solvent ethylene glycol dimethyl ether DME and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and stirred evenly to obtain an electrolyte with a concentration of 4 mol / L.

[0187] 4. Isolation film

[0188] Polypropylene film is used as the isolation film.

[0189] 5. Preparation of secondary batteries

[0190] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried lithium-ion battery. After vacuum packaging, standing, formation, and shaping processes, a lithium-ion battery is obtained.

[0191] The preparation method of the lithium-ion battery of Example 2-42 is the same as that of Example 1, except that the composition of the prepared positive electrode plate is different, as shown in Table 1.

[0192] Example 43

[0193] The difference from Example 1 is that the method for preparing the positive electrode sheet is different, and the remaining steps are the same as Example 1.

[0194] The method for preparing a positive electrode sheet includes:

[0195] The positive electrode active particles LiNi 0.8 Co 0.1 Mn 0.1 O2 is mixed with conductive agent carbon black, adhesive polyvinylidene fluoride and solvent NMP to obtain positive electrode slurry (positive electrode active particles LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 to conductive agent carbon black and adhesive polyvinylidene fluoride is 98:1:1, and the solid content of the positive electrode slurry is 60%), the positive electrode slurry is coated on the upper and lower surfaces of the positive electrode current collector carbon-coated aluminum foil, and then a mixed solution including an organic solvent and a polymer is coated on the positive electrode slurry layer. The solvent NMP and the organic solvent are removed by roller coating and drying, and a positive electrode active material layer (with a thickness of 40 μm) and a polymer layer are sequentially formed on the surface of the positive electrode current collector. Finally, the obtained electrode is immersed in a mixed solution including an electrolyte salt, an organic solvent, an adsorption additive and a film-forming additive. The electrolyte salt, organic solvent, adsorption additive and film-forming additive are immersed in the polymer layer on the surface of the positive electrode active material layer to form a protective layer to obtain a positive electrode electrode, wherein the composition and content of the polymer, organic solvent, adsorption additive and film-forming additive are shown in Table 2.

[0196] The preparation method of the lithium-ion battery of Examples 44-83 is the same as that of Example 43, except that the composition of the prepared positive electrode plate is different, as shown in Table 2.

[0197] Comparative Example

[0198] The difference from Example 1 is that the method for preparing the positive electrode sheet is different, and the remaining steps are the same as Example 1.

[0199] The method for preparing a positive electrode sheet includes:

[0200] The positive electrode active particles LiNi 0.8 Co 0.1 Mn 0.1 O2 is mixed with conductive agent carbon black, adhesive polyvinylidene fluoride and solvent NMP to obtain positive electrode slurry (positive electrode active particles LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 to conductive agent carbon black and adhesive polyvinylidene fluoride is 98:1:1, and the solid content of the positive electrode slurry is 60%. The positive electrode slurry is coated on the upper and lower surfaces of the positive electrode current collector carbon-coated aluminum foil, and the solvent NMP is removed by roller coating and drying to form a positive electrode active material layer (with a thickness of 40 μm) on the surface of the positive electrode current collector to obtain a positive electrode sheet.

[0201] The changes in the charge and discharge coulombic efficiency of the batteries obtained in Examples 1-83 and the comparative example were characterized, and the characterization results are shown in Table 3.

[0202] Test of the change of coulombic efficiency of charge and discharge: The battery is charged and discharged, charged at a constant current of 2C with a charging cut-off voltage of 4.3V, then discharged at a constant current of 1C with a discharge cut-off voltage of 2.8V, and then cycled with 2C constant current charging and 1C constant current discharging for n cycles, recording the charging specific capacity C0 of the nth cycle and the discharge specific capacity C1 of the nth cycle.

[0203] The formula for calculating Coulombic efficiency (CE) is: CE = discharge specific capacity C1 / charge specific capacity C0×100%.

[0204] Table 3

[0205] Note: CE50%@15 cycles can be understood as the coulombic efficiency of the battery is 50% after 15 cycles.

[0206] As can be seen from Table 3, the coulombic efficiency of the comparative battery is 50% after 15 cycles, while the coulombic efficiency of the battery of Example 1-83 is significantly higher than that of the comparative example. This shows that the positive electrode of the present application forms a polymer layer comprising a polymer and an organic solvent on the surface of the positive electrode active material particles (the electrochemical oxidation window of the organic solvent is higher than 4V), and the organic solvent is absorbed or adsorbed in the polymer, or a protective layer comprising a polymer and an organic solvent is formed on the surface of the active material of the positive electrode, thereby improving the coulombic efficiency of the battery and reducing the risk of battery overcharge.

[0207] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0208] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A positive electrode sheet, wherein: The positive electrode plate includes a positive electrode current collector. At least one side of the positive electrode plate away from the positive electrode current collector includes a polymer and an organic solvent. The organic solvent is located in the polymer, and the electrochemical oxidation window of the organic solvent is higher than 4V.

2. The positive electrode sheet according to claim 1, wherein: The positive electrode sheet includes a positive electrode active material layer, which is arranged on at least one side of the positive electrode current collector. The positive electrode active material layer includes positive electrode active particles, and the surface of the positive electrode active particles has a polymer layer, and the polymer layer includes the polymer and the organic solvent.

3. The positive electrode sheet according to claim 2, wherein: The positive electrode active material layer further includes at least one of a binder and a conductive agent.

4. The positive electrode sheet according to claim 3, wherein: The mass ratio of the positive electrode active particles to the binder and the conductive agent is (90-100):(0-5):(0-5), and can be optionally (95-98.5):(0.5-2):(0.5-2).

5. The positive electrode sheet according to any one of claims 2 to 4, wherein: The thickness of the positive electrode active material layer is 30 μm-60 μm, and can be 30 μm-50 μm.

6. The positive electrode sheet according to any one of claims 2 to 5, wherein: The thickness of the polymer layer is 0.01 μm-2 μm, and can be optionally 0.01 μm-1 μm.

7. The positive electrode sheet according to any one of claims 2 to 6, wherein: The mass ratio of the polymer to the organic solvent is (0.1-99):(1-99.9), and can be optionally (0.1-15):(85-99.9).

8. The positive electrode sheet according to any one of claims 2 to 7, wherein: The polymer layer also includes an electrolyte salt.

9. The positive electrode sheet according to any one of claims 2 to 8, wherein: Based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt is 0.1 mol / L-10 mol / L, and can be 0.5 mol / L-5 mol / L.

10. The positive electrode sheet according to any one of claims 2 to 9, wherein: The polymer layer further includes at least one of a film-forming additive and an adsorbing additive.

11. The positive electrode sheet according to claim 10, wherein: The electrochemical oxidation window of the film-forming additive is less than or equal to 4V; and / or The electrochemical oxidation window of the adsorbent additive is higher than 4V.

12. The positive electrode sheet according to claim 10 or 11, wherein: The mass ratio of the polymer to the film-forming additive and the adsorption additive is (10-100):(0-90):(0-90), and can be optionally (30-80):(20-70):(20-70).

13. The positive electrode sheet according to any one of claims 1 to 12, wherein: The positive electrode sheet includes a positive electrode active material layer and a protective layer. The positive electrode active material layer is arranged on at least one side of the positive electrode current collector. The protective layer is arranged on at least one side of the positive electrode active material layer. The protective layer includes the polymer and the organic solvent.

14. The positive electrode sheet according to claim 13, wherein: The thickness of the protective layer is 0.1 μm-40 μm, optionally 1 μm-20 μm, and more optionally 1 μm-10 μm.

15. The positive electrode sheet according to claim 13 or 14, wherein: In the protective layer, the mass ratio of the polymer to the organic solvent is (0.1-99):(1-99.9), and can be optionally (0.1-15):(85-99.9).

16. The positive electrode sheet according to any one of claims 13 to 15, wherein: The protective layer also includes an electrolyte salt.

17. The positive electrode sheet according to any one of claims 13 to 16, wherein: Based on the total amount of the organic solvent and the electrolyte salt, the concentration of the electrolyte salt is 0.1 mol / L-10 mol / L, and can be 0.5 mol / L-5 mol / L.

18. The positive electrode sheet according to any one of claims 13 to 17, wherein: The protective layer further includes at least one of a film-forming additive and an adsorption additive.

19. The positive electrode sheet according to claim 18, wherein: The electrochemical oxidation window of the film-forming additive is less than or equal to 4V; and / or The electrochemical oxidation window of the adsorbent additive is higher than 4V.

20. The positive electrode sheet according to claim 18 or 19, wherein: The mass ratio of the polymer to the film-forming additive and the adsorption additive is (10-100):(0-90):(0-90), and can be optionally (30-80):(20-70):(20-70).

21. The positive electrode sheet according to any one of claims 1 to 20, wherein: The organic solvent includes carbonate, carboxylic acid ester, C5-C 16 At least one of an alkane, an aromatic hydrocarbon having an electron withdrawing group and / or an alkyl group, a nitrile and a ketone, wherein the electron withdrawing group comprises at least one of halogen, -NO2, -C≡N, -C=C, -C≡C and -OCH3.

22. The positive electrode sheet according to any one of claims 10 to 21, wherein: The film-forming additive includes at least one of dioxalatoborate, difluorooxalatoborate, difluorophosphate, methyl trifluoroethyl carbonate, tris(pentafluorophenyl)borane, fluoroethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate and propylene trifluorocarbonate.

23. The positive electrode sheet according to any one of claims 10 to 22, wherein: The adsorption additive includes at least one of carbonate, phosphate, nitrile and ionic liquid.

24. The positive electrode sheet according to any one of claims 1 to 23, wherein: The electrochemical oxidation window of the polymer is higher than 4V.

25. The positive electrode sheet according to any one of claims 1 to 24, wherein: The swelling degree of the polymer is 5%-2000%, and optionally 50%-1500%.

26. The positive electrode sheet according to any one of claims 1 to 25, wherein: The cross-linking density of the polymer is 1%-100%, and can be optionally 30%-70%.

27. The positive electrode sheet according to any one of claims 1 to 26, wherein: The number average molecular weight of the polymer is 10,000-1,000,000, and can be optionally 50,000-600,000.

28. The positive electrode sheet according to any one of claims 1 to 27, wherein: The polymer comprises the following repeating units: R1-R4 independently include H, alkyl, F, Cl, Br, I, C≡N, phenyl, pyrrol, pyrrolone, sulfonic acid, sulfonate, benzenesulfonate, carboxylic acid, and carbonate.

29. The positive electrode sheet according to claim 28, wherein: The repeating unit comprises at least one of the following structural formulas:

30. A method for preparing a positive electrode sheet, wherein: include: A positive electrode sheet comprising a polymer and an organic solvent is formed, wherein the polymer and the organic solvent are located on at least one side of the positive electrode sheet away from the positive electrode current collector, the organic solvent is located in the polymer, and the electrochemical oxidation window of the organic solvent is higher than 4V.

31. The method according to claim 30, wherein: include: A positive electrode active material layer including positive electrode active particles is formed on at least one side of the positive electrode current collector, and a polymer layer including the polymer and the organic solvent is formed on the surface of the positive electrode active particles.

32. The method according to claim 30 or 31, wherein: include: forming a positive electrode active material layer on at least one side of the positive electrode current collector; A protective layer including a polymer and the organic solvent is formed on at least one side of the positive electrode active material layer.

33. A battery, wherein: The battery comprises the positive electrode sheet according to any one of claims 1 to 29 or the positive electrode sheet obtained by the method according to any one of claims 30 to 32.

34. The battery according to claim 33, wherein The battery includes an electrolyte, the electrolyte includes a main solvent, and the main solvent is different from the organic solvent in the positive electrode sheet.

35. The battery according to claim 33 or 34, wherein The electrochemical oxidation window of the main solvent is lower than or equal to 4V.

36. An electrical device, wherein: The electrical device comprises the battery according to any one of claims 33-35.

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