Positive electrode material and preparation method thereof, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device

Abstract

The present application relates to the field of secondary battery technology, and in particular to a positive electrode material and preparation method, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electrical device. The positive electrode material of the present application includes a lithium oxygen-containing compound and a lithium sulfide containing a polyanion, wherein the lithium sulfide containing a polyanion has a chemical formula of LiMS (2‑x) (XO m ) x , wherein 0<x<2, 0<m≤4; M is selected from at least one of Fe, V, Nb, Zr, and Mn, and X is selected from at least one of P, Si, S, As, Mo, W, and B. The present application mixes polyanions with lithium sulfide. Due to the addition of polyanions, the p orbital energy of sulfur ions in lithium sulfide is reduced, the covalency of the compound system is reduced, the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in the redox reaction is increased, thereby improving the discharge platform of the secondary battery material and being able to improve its discharge power at low SOC.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a positive electrode material and a preparation method, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device. Background Art

[0002] With the rapid development of the new energy field, secondary batteries are widely used in various large-scale power devices, energy storage systems and various consumer products due to their excellent charging and discharging chemical properties, no memory effect, and low environmental pollution. In recent years, the popularization of power devices such as smart phones and electric vehicles has enabled the widespread use of lithium-ion secondary batteries.

[0003] However, with the increasing demand from customers, certain electrochemical properties of lithium-ion secondary batteries, especially the low discharge power of the secondary battery at low SOC, have put forward higher requirements for the development of lithium-ion secondary batteries. Summary of the invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode material and preparation method, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electrical device, so as to greatly improve the discharge power of the secondary battery in a low state of charge (full name of English: State of Charge, abbreviated as SOC).

[0005] The first aspect of the present application provides a positive electrode material, including an oxygen-containing compound of lithium and a lithium sulfide containing a polyanion, wherein the lithium sulfide containing a polyanion is a compound shown in Formula I:

[0006] LiMS (2-x) (XO m ) x Formula I

[0007] Among them, 0<x<2, 0<m≤4; M is selected from at least one of iron (Fe), vanadium (V), niobium (Nb), zirconium (Zr), and manganese (Mn); X is selected from at least one of phosphorus (P), silicon (Si), sulfur (S), arsenic (As), molybdenum (Mo), tungsten (W), and boron (B).

[0008] The present application mixes polyanions with lithium sulfide. Due to the addition of polyanions, the p-orbital energy of sulfur ions in lithium sulfide is reduced, the covalency of the compound system is reduced, the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in redox reactions is increased. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0009] In any embodiment, based on the total mass of the positive electrode material, the mass percentage of the lithium sulfide containing the polyanion is 3% to 10%, or alternatively 3% to 5%.

[0010] The present application provides good conditions for the complete reaction of ion polymerization of lithium sulfide by controlling the mass percentage of lithium sulfide containing polyanions to 3% to 10%, greatly reducing the p orbital energy of sulfur ions in lithium sulfide, and also greatly reducing the covalency in the compound system, so that the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in redox reactions is increased. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0011] In any embodiment, the specific surface area of ​​the positive electrode material is 3.5 m 2 / g~7m 2 / g. The present application can well control the particle size of the positive electrode material by reasonably controlling the specific surface area of ​​the positive electrode material, so that the discharge power performance of the secondary battery at low SOC is greatly improved.

[0012] In any embodiment, the oxygen-containing compound of lithium includes lithium transition metal oxides and / or lithium phosphates with an olivine structure, the lithium transition metal oxide is selected from at least one 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 modified compounds thereof, and the lithium phosphate with an olivine structure is selected from at least one 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0013] The present application increases the proportion of transition metal by adding lithium transition metal oxides and / or lithium phosphates with an olivine structure, thereby ensuring that a sufficient proportion of the d orbital of the transition metal in the positive electrode material participates in the redox reaction. Since the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, the total voltage platform of the system is greatly improved, thereby improving the discharge power performance of the secondary battery at low SOC.

[0014] The second aspect of the present application provides a method for preparing a positive electrode material, which comprises the following steps:

[0015] Provide Li2S, metal M, sulfur powder and Li2XO m The mixture is ball-milled, sieved and sintered to obtain a lithium sulfide containing a polyanion, and the lithium sulfide containing a polyanion is mixed with a lithium oxygen-containing compound to obtain a positive electrode material;

[0016] Wherein, the positive electrode material is a lithium sulfide containing a polyanion having formula I:

[0017] LiMS (2-x) (XO m ) x Formula I

[0018] 0<x<2, 0<m≤4; M is selected from at least one of iron (Fe), vanadium (V), niobium (Nb), zirconium (Zr), and manganese (Mn); X is selected from at least one of phosphorus (P), silicon (Si), sulfur (S), arsenic (As), molybdenum (Mo), tungsten (W), and boron (B).

[0019] The present invention relates to a method for preparing lithium sulfide (Li2S), metal M, sulfur powder and Li2XO m The two materials are mixed in a certain ratio, ball-milled, screened and sintered to obtain lithium sulfide containing polyanions, and then the lithium sulfide containing polyanions is mixed with lithium oxygen-containing compounds in a certain ratio to obtain positive electrode materials.

[0020] The present application mixes polyanions with lithium sulfide. Due to the addition of polyanions, the p-orbital energy of sulfur ions in lithium sulfide is reduced, the covalency of the compound system is reduced, the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in redox reactions is increased. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0021] In any embodiment, in the ball milling step, the ball milling time is 24h to 48h, the ball milling speed is 500r to 800r, and the ball to material ratio is 50:1 to 100:1. The present application reasonably sets the ball milling ratio, ball milling speed and ball milling time so that lithium sulfide (Li2S), metal M, sulfur powder and Li2XO m The mixing is more uniform, so that the polyanion can combine more deeply with lithium sulfide, laying a good foundation for the subsequent polyanion effect.

[0022] The third aspect of the present application provides a positive electrode plate, comprising the positive electrode material of the first aspect of the present application or the positive electrode material prepared by the preparation method of the positive electrode material of the second aspect of the present application.

[0023] The fourth aspect of the present application provides a secondary battery, comprising the positive electrode sheet of the third aspect of the present application.

[0024] A fifth aspect of the present application provides a battery module, comprising the secondary battery of the fourth aspect of the present application.

[0025] The sixth aspect of the present application provides a battery pack, comprising the battery module of the fifth aspect of the present application.

[0026] The seventh aspect of the present application provides an electrical device, comprising at least one selected from the positive electrode plate of the third aspect of the present application, the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, and the battery pack of the sixth aspect of the present application.

[0027] By adopting the above technical solution, the beneficial effects of this application are:

[0028] The present application mixes polyanions with lithium sulfide. The addition of polyanions reduces the p-orbital energy of sulfur ions in lithium sulfide, thereby reducing the covalency of the compound system, reducing the hybridization between d orbitals and p orbitals, and increasing the proportion of d orbitals of transition metals in the compound participating in redox reactions. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0029] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure.

[0030] Undoubtedly, these and other objects of the present application will become more apparent after the following detailed description of the preferred embodiment described with various figures and drawings.

[0031] In order to make the above and other purposes, features and advantages of the present application more obvious and understandable, one or several preferred implementation modes are specifically cited below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. They are used together with the implementation methods of the present application to explain the present application and do not constitute a limitation to the present application.

[0033] In the drawings, the same reference numerals are used for the same components and the drawings are schematic and not necessarily drawn to scale.

[0034] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one or several implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on such drawings without paying creative work.

[0035] Figure 1The SEM images of sulfides according to some embodiments of the present application;

[0036] Figure 2 A sulfide mechanism diagram for some embodiments of the present application;

[0037] Figure 3 A schematic diagram of the structure of a secondary battery according to some embodiments of the present application;

[0038] Figure 4 This is a structural exploded view of a secondary battery according to some embodiments of the present application;

[0039] Figure 5 This is a schematic diagram of the structure of a battery module according to some embodiments of the present application;

[0040] Figure 6 A schematic diagram of the structure of a battery pack according to some embodiments of the present application;

[0041] Figure 7 This is a structural exploded view of a battery pack according to some embodiments of the present application;

[0042] Figure 8 This is a schematic diagram of the structure of an electrical device in some embodiments of the present application.

[0043] Description of main reference numerals:

[0044] 1 battery pack;

[0045] 2 upper box;

[0046] 3 lower box;

[0047] 4 battery modules;

[0048] 5. Secondary battery;

[0049] 51 housing; 52 electrode assembly 52; 53 top cover assembly;

[0050] 6. Electrical devices. DETAILED DESCRIPTION

[0051] Below, the negative electrode active material and its preparation method, negative electrode pole piece, secondary battery, battery module, battery pack and electric device of the present application are described in detail with appropriate reference to the drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0052] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] In the description of the implementation methods of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the implementation methods of this application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0054] In the description of the implementation methods of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship. Unless otherwise specified, the "include" and "comprises" mentioned in this application may be open-ended or closed. For example, the "include" and "comprises" may mean that other components not listed may also be included or comprised, or may only include or comprise the listed components.

[0055] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0056] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0057] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "up", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the embodiments of the present application.

[0058] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0059] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0060] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0061] The depletion of energy resources has led to significant development of new energy storage devices. Secondary batteries have attracted much attention due to their high energy density, high capacity, good cycle stability and environmental protection characteristics.

[0062] At present, from the perspective of market development, the application of secondary batteries is becoming more and more extensive. Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of secondary batteries, the market demand is also constantly expanding.

[0063] The inventors of the present application noticed that the discharge platform of the existing positive electrode materials is low, which results in the secondary battery not being able to properly exert its discharge power performance at low SOC. The inventors of the present application tried to dope lithium sulfide with the existing positive electrode materials, but the discharge platform of lithium sulfide is low, and although it can improve the initial charge and discharge efficiency of the battery to a certain extent, it cannot improve the discharge power performance of the secondary battery at low SOC.

[0064] Based on the above considerations, in order to improve the discharge power performance of secondary batteries at low SOC, the inventors of the present application conducted experimental screening on the composition, ratio, elements, etc. of the positive electrode materials, and found that doping polyanions into lithium-sulfur compounds can greatly improve the discharge power performance of secondary batteries at low SOC.

[0065] Reference Figure 1-2 , Figure 1 The SEM images of sulfides according to some embodiments of the present application; Figure 2 This is a sulfide mechanism diagram for some embodiments of the present application.

[0066] According to some embodiments of the present application, the present application provides a positive electrode material, including an oxygen-containing compound of lithium and a lithium sulfide containing a polyanion, wherein the lithium sulfide containing a polyanion is a compound shown in Formula I:

[0067] LiMS (2-x) (XO m ) x Formula I

[0068] Among them, 0<x<2, 0<m≤4; M is selected from at least one of iron (Fe), vanadium (V), niobium (Nb), zirconium (Zr), and manganese (Mn); X is selected from at least one of phosphorus (P), silicon (Si), sulfur (S), arsenic (As), molybdenum (Mo), tungsten (W), and boron (B).

[0069] The oxygen-containing compounds of lithium refer to lithium compounds containing oxygen elements, including but not limited to lithium-metal oxides, lithium transition metal oxides, lithium-containing salts, and the like.

[0070] Please refer again Figure 1 , lithium sulfide containing polyanion refers to a class of compounds formed by lithium and sulfur, and this class of compounds has anions that can undergo ionic polymerization. Among them, polyanion refers to anions that can undergo ionic polymerization, and the monomer that initiates the polymerization reaction is an anion, that is, the reactive part at the end of its growing polymer chain is an anion, and the anion should be stable, must be able to chain grow, and the anion cannot be isomerized into a stable structure; lithium sulfide refers to a class of compounds formed by lithium and sulfur.

[0071] Therefore, the present application mixes polyanions with lithium sulfide. The addition of polyanions reduces the p-orbital energy of sulfur ions in lithium sulfide, thereby reducing the covalency of the compound system, reducing the hybridization between d orbitals and p orbitals, and increasing the proportion of d orbitals of transition metals in the compound participating in redox reactions. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0072] In some embodiments, optionally, based on the total mass of the positive electrode material, the mass percentage of the lithium sulfide containing the polyanion is 3% to 10%, optionally 3% to 5%.

[0073] If the mass percentage of lithium sulfide containing polyanions is less than 3%, that is, there are too few polyanions (anions capable of undergoing ionic polymerization reactions) in the lithium sulfide, resulting in incomplete ionic polymerization reactions of the lithium sulfide, and the p orbital energy of the sulfur ions in the lithium sulfide cannot be reduced, and the covalency in the compound system cannot be reduced; if the mass percentage of lithium sulfide containing polyanions is higher than 10%, that is, there are too many polyanions (anions capable of undergoing ionic polymerization reactions) in the lithium sulfide, resulting in saturation of the ionic polymerization reaction of the lithium sulfide, making the p orbital energy of the sulfur ions in the lithium sulfide too low, so that the covalency in the compound system is too low, affecting the d orbital and p orbital. Influence between orbitals; the present application provides good conditions for the complete reaction of ion polymerization of lithium sulfide by controlling the mass percentage of lithium sulfide containing polyanions to 3% to 10%, greatly reducing the p orbital energy of sulfur ions in lithium sulfide, and also greatly reducing the covalency in the compound system, so that the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in redox reactions is increased. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0074] Optionally, the mass percentage of lithium sulfide containing polyanions is 10%, 9%, 7%, 6%, 5%, 4%, 3% or a value within the range obtained by combining any two of the above values.

[0075] Furthermore, the mass percentage of lithium sulfide containing polyanions is 5%, 4.9%, 4.8%, 4.7%, 4.6%, 4.5%, 4.4%, 4.3%, 4.2%, 4.1%, 3% or a value within the range obtained by combining any two of the above values.

[0076] In some embodiments, optionally, the specific surface area of ​​the positive electrode material is 3.5 m 2 / g~7m 2 / g. Specific surface area refers to the total area per unit mass of material, and the unit is m 2 / g, usually refers to the specific surface area of ​​solid materials, such as powder, fiber, particle, sheet, block and other materials. In other words, the specific surface area is the ratio of area to volume. The present application reasonably controls the specific surface area of ​​the positive electrode material, that is, the particle size of the positive electrode material is well controlled, so that the discharge power performance of the secondary battery at low SOC is greatly improved.

[0077] Optionally, the specific surface area of ​​the positive electrode material is 7m 2 / g, 6.5m 2 / g, 6.0m 2 / g, 5.5m 2 / g, 5.0m 2 / g, 4.5m 2 / g, 4.0m 2 / g, 3.5m 2 / g or its value is within the range obtained by combining any two of the above values.

[0078] Furthermore, the specific surface area of ​​the positive electrode material is 5m 2 / g, 5.9m 2 / g, 5.8m 2 / g, 5.7m 2 / g, 5.6m 2 / g, 5.5m 2 / g, 5.4m 2 / g, 5.3m 2 / g, 5.2m 2 / g, 5.1m 2 / g, 5.0m 2 / g, 4.9m 2 / g, 4.8m 2 / g, 4.7m 2 / g, 4.6m 2 / g, 4.5m 2 / g, 4.4m 2 / g, 4.3m 2 / g, 4.2m 2 / g, 4.1m 2 / g, 4.0m 2 / g, 3.9m 2 / g, 3.8m 2 / g, 3.7m 2 / g, 3.6m 2 / g, 3.5m 2 / g or its value is within the range obtained by combining any two of the above values.

[0079] In some embodiments, the lithium oxygen-containing compound may optionally include a lithium transition metal oxide and / or a lithium-containing phosphate having an olivine structure. Specifically, the lithium oxygen-containing compound may include only a lithium transition metal oxide, or only an olivine-structured lithium-containing phosphate, or may include both a lithium transition metal oxide and an olivine-structured lithium-containing phosphate.

[0080] Lithium transition metal oxide refers to materials containing lithium, transition metal and oxide.

[0081] Transition metals refer to a series of metallic elements in the d zone of the periodic table, also known as transition elements. This area includes ten groups of elements from 3 to 12, but does not include the inner transition elements in the f zone.

[0082] The lithium-containing phosphate with an olivine structure refers to a lithium-containing phosphate with an ordered olivine structure. The lithium-containing phosphate has a chemical formula of LIMPO4, where M is manganese (Mn), cobalt (Co), or nickel (Ni).

[0083] Furthermore, the lithium transition metal oxide is selected from at least one 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 modified compounds thereof.

[0084] Furthermore, the lithium-containing phosphate with an olivine structure is selected from at least one 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0085] The present application increases the proportion of transition metal by adding lithium transition metal oxides and / or lithium phosphates with an olivine structure, thereby ensuring that a sufficient proportion of the d orbital of the transition metal in the positive electrode material participates in the redox reaction. Since the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, the total voltage platform of the system is greatly improved, thereby improving the discharge power performance of the secondary battery at low SOC.

[0086] According to some embodiments of the present application, the present application provides a method for preparing a positive electrode material, which comprises the following steps:

[0087] Provide lithium sulfide (Li2S), metal M, sulfur powder and Li2XO m The mixture is ball-milled, sieved and sintered to obtain a lithium sulfide containing a polyanion, and the lithium sulfide containing a polyanion is mixed with a lithium oxygen-containing compound to obtain a positive electrode material;

[0088] Wherein, the positive electrode material is a lithium sulfide containing a polyanion having formula I:

[0089] LiMS (2-x) (XO m ) x Formula I

[0090] 0<x<2, 0<m≤4; M is selected from at least one of iron (Fe), vanadium (V), niobium (Nb), zirconium (Zr), and manganese (Mn); X is selected from at least one of phosphorus (P), silicon (Si), sulfur (S), arsenic (As), molybdenum (Mo), tungsten (W), and boron (B).

[0091] Therefore, the present invention combines lithium sulfide (Li2S), metal M, sulfur powder and Li2XO m The two materials are mixed in a certain ratio, ball-milled, screened and sintered to obtain lithium sulfide containing polyanions, and then the lithium sulfide containing polyanions is mixed with lithium oxygen-containing compounds in a certain ratio to obtain positive electrode materials.

[0092] The present application mixes polyanions with lithium sulfide. Due to the addition of polyanions, the p-orbital energy of sulfur ions in lithium sulfide is reduced, the covalency of the compound system is reduced, the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in redox reactions is increased. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0093] In some embodiments, optionally, in the ball milling step, the ball milling time is 24h to 48h, the ball milling speed is 500r to 800r, and the ball to material ratio is 50:1 to 100:1. The present application reasonably sets the ball milling ratio, ball milling speed and ball milling time to make lithium sulfide (Li2S), metal M, sulfur powder and Li2XO m The mixing is more uniform, so that the polyanion can combine more deeply with lithium sulfide, laying a good foundation for the subsequent polyanion effect.

[0094] According to some embodiments of the present application, the present application provides a positive electrode plate, comprising the positive electrode material of the first aspect of the present application or the positive electrode material prepared by the preparation method of the positive electrode material of the second aspect of the present application.

[0095] The present invention relates to a method for preparing lithium sulfide (Li2S), metal M, sulfur powder and Li2XO m The two materials are mixed in a certain ratio, ball-milled, screened and sintered to obtain lithium sulfide containing polyanions, and then the lithium sulfide containing polyanions is mixed with lithium oxygen-containing compounds in a certain ratio to obtain positive electrode materials.

[0096] The present application mixes polyanions with lithium sulfide. Due to the addition of polyanions, the p-orbital energy of sulfur ions in lithium sulfide is reduced, the covalency of the compound system is reduced, the hybridization between d orbitals and p orbitals is reduced, and the proportion of d orbitals of transition metals in the compound participating in redox reactions is increased. At the same time, the voltage platform of the transition metal is generally higher than the voltage platform of the sulfur ion, thereby improving the total voltage platform of the system, thereby improving the discharge platform of the secondary battery material and improving its discharge power at low SOC.

[0097] Since the positive electrode plate of the present application includes the positive electrode material of the first aspect of the present application or the positive electrode material prepared by the preparation method of the second aspect of the present application, the positive electrode plate of the present application also has the beneficial effects of the positive electrode material.

[0098] Reference Figure 3-4 , Figure 3 A schematic diagram of the structure of a secondary battery according to some embodiments of the present application; Figure 4 This is a structural exploded view of a secondary battery according to some embodiments of the present application.

[0099] According to some embodiments of the present application, the present application provides a secondary battery 5 .

[0100] Generally, the secondary battery 5 includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0101]

Positive electrode

[0102] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode material of the first aspect of the present application.

[0103] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0104] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments, the positive electrode material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode materials for batteries may also be used. These positive electrode materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0106] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0107] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0108] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0109]

Negative electrode

[0110] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode material.

[0111] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0112] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0113] In some embodiments, the negative electrode material may be a negative electrode material for a battery known in the art. As an example, the negative electrode material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode materials for batteries may also be used. These negative electrode materials may be used alone or in combination of two or more.

[0114] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0115] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0116] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0117] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0118]

Electrolytes

[0119] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0120] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0121] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0122] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0123] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0124]

Isolation film

[0125] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0126] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0127] [Secondary battery 5]

[0128] The positive electrode sheet and the negative electrode sheet are assembled into a battery cell, and the secondary battery 5 is obtained after the processes of liquid injection, formation, aging, K measurement, capacity test, etc. are carried out.

[0129] In some embodiments, the secondary battery 5 may include an outer package that can be used to encapsulate the electrode assembly 52 and the electrolyte.

[0130] In some embodiments, the outer package of the secondary battery 5 may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery 5 may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0131] The present application has no particular limitation on the shape of the secondary battery 5 , which may be cylindrical, square, or any other shape.

[0132] In some embodiments, the outer package may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity. The shell has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0133] Reference Figure 5 , Figure 5 This is a schematic diagram of the structure of a battery module according to some embodiments of the present application.

[0134] According to some embodiments of the present application, the present application provides a battery module 4. The battery module 4 includes a secondary battery 5 provided in the present application. The number of secondary batteries 5 included in the battery module 4 may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module 4.

[0135] In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0136] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0137] Reference Figure 6-7 , Figure 6 A schematic diagram of the structure of a battery pack according to some embodiments of the present application; Figure 7 This is a structural exploded view of the battery pack of some embodiments of the present application.

[0138] According to some embodiments of the present application, the present application provides a battery pack 1. The battery pack 1 includes a battery module 4 provided in the present application. The number of battery modules 4 included in the battery pack 1 may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack 1.

[0139] The battery pack 1 may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0140] Reference Figure 8 , Figure 8 This is a schematic diagram of the structure of an electrical device in some embodiments of the present application.

[0141] According to some embodiments of the present application, the present application provides an electric device 6. The electric device 6 includes at least one selected from the positive electrode plate provided in the present application, the secondary battery 5 provided in the present application, the battery module 4 provided in the present application, and the battery pack 1 provided in the present application. The secondary battery 5, the battery module 4, and the battery pack 1 can be used as a power source for the electric device 6, and can also be used as an energy storage unit for the electric device 6. The electric device 6 may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0142] As the electric device 6 , a secondary battery 5 , a battery module 4 or a battery pack 1 may be selected according to its usage requirements.

[0143] The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device 6's requirements for high power and high energy density of the secondary battery 5, a battery pack 1 or a battery module 4 may be used.

[0144] In some embodiments, the power-consuming device 6 may be a mobile phone, a tablet computer, a laptop computer, etc. The power-consuming device 6 is usually required to be light and thin, and a secondary battery 5 may be used as a power source.

[0145] Example

[0146] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0147] Example 1

[0148] The positive electrode material includes lithium oxygen-containing compounds and lithium sulfide containing polyanions. The lithium oxygen-containing compounds include lithium transition metal oxides and lithium phosphates with an olivine structure. The lithium sulfide containing polyanions is LiTiS(SO4).

[0149] Wherein, based on the total mass of the positive electrode material, the mass percentage of lithium sulfide containing polyanions is 6.5%; the specific surface area of ​​the positive electrode material is 5m 2 / g.

[0150]

Preparation method of positive electrode material

[0151] Provide Li2S, metal M, sulfur powder and Li2XO m The mixture is ball-milled (ball milling time is 36 hours, ball milling speed is 650r, ball-to-material ratio is 75:1), sieved and sintered to obtain lithium sulfide containing polyanions, and the lithium sulfide containing polyanions is mixed with a lithium oxygen-containing compound to obtain a positive electrode material.

[0152]

Method for preparing secondary battery

[0153] The positive electrode material, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone solvent at a weight ratio of 96:3:1, and then coated on an aluminum foil, dried, and cold pressed to obtain a positive electrode sheet;

[0154] Artificial graphite as negative electrode material, conductive agent Super P, binder styrene-butadiene rubber (SBR) and thickener sodium carbon methyl cellulose (CMC) are fully stirred and mixed in a deionized water solvent system at a weight ratio of 97:0.5:1.5:1, and then coated on copper foil, dried, and cold pressed to obtain a negative electrode sheet;

[0155] The isolation membrane is made of polyvinylidene fluoride;

[0156] The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, the separator is placed between the positive and negative electrodes to play a role of isolation, and then wound to obtain a bare cell. The bare cell is placed in a corresponding aluminum shell, the electrolyte is injected and packaged to obtain a secondary battery.

[0157] Example 2

[0158] The difference between this embodiment and embodiment 1 is that the lithium sulfide containing polyanions is LiTiS(PO4).

[0159] Example 3

[0160] The difference between this embodiment and embodiment 1 is that the lithium sulfide containing polyanions is LiTiS(BO3).

[0161] Example 4

[0162] The difference between this embodiment and embodiment 1 is that the lithium sulfide containing polyanions is LiVS (SO4).

[0163] Example 5

[0164] The difference between this embodiment and embodiment 1 is that the lithium sulfide containing polyanions is LiZrS (SO4).

[0165] Example 6

[0166] The difference between this embodiment and embodiment 1 is that, based on the total mass of the positive electrode material, the mass percentage of the lithium sulfide containing the polyanion is 3.0%.

[0167] Example 7

[0168] The difference between this embodiment and embodiment 1 is that, based on the total mass of the positive electrode material, the mass percentage of the lithium sulfide containing the polyanion is 10.0%.

[0169] Example 8

[0170] The difference between this embodiment and embodiment 1 is that the specific surface area of ​​the positive electrode material is 3.5 m 2 / g.

[0171] Example 9

[0172] The difference between this embodiment and embodiment 1 is that the specific surface area of ​​the positive electrode material is 7m 2 / g.

[0173] Comparative Example 1

[0174] The difference between this comparative example and Example 1-1 is that the positive electrode material includes lithium oxygen-containing compounds and lithium sulfide, the lithium oxygen-containing compounds include lithium transition metal oxides and lithium phosphates with olivine structure, and the lithium sulfide is Li2S.

[0175] Comparative Example 2

[0176] The difference between this comparative example and Example 1-1 is that the positive electrode material includes an oxygen-containing compound of lithium, and the oxygen-containing compound of lithium includes a lithium transition metal oxide and a lithium-containing phosphate with an olivine structure.

[0177]

Secondary battery performance test

[0178] Secondary battery power performance test

[0179] Charge and discharge the secondary battery for a certain period of time, and then calculate the DCR (Direct Current Resistance) value, which can be obtained according to the following calculation formula:

[0180] R DCR放电 (I1, t1) = |V1-V2| / I1;

[0181] R DCR充电 (I2, t2) = |V4-V3| / I2;

[0182] Among them, I1 is the discharge current value, I2 is the charging current value, t1 is the discharge duration, t2 is the charging duration, V1 is the voltage value at the start of discharge, V2 is the voltage value at the end of discharge, V3 is the voltage value at the start of charging, and V4 is the voltage value at the end of charging.

[0183] The parameters related to the positive electrode materials and the battery performance test data of the embodiments and comparative examples are shown in Table 1.

[0184] Table 1 Related parameters of positive electrode materials and secondary battery performance test data of embodiments and comparative examples

[0185]

[0186]

Data Analysis

[0187] As can be seen from Table 1, the DCR value is calculated by charging and discharging the secondary battery for a certain period of time.

[0188] No polyanion is added to the positive electrode materials in the secondary batteries of Comparative Examples 1 and 2, resulting in the inability to reduce the p orbital energy of the sulfur ions in the lithium sulfide, and the covalency of the compound system is not reduced. There is more hybridization between the d orbital and the p orbital, and the proportion of the d orbital of the transition metal in the compound participating in the redox reaction is small, making its DCR at 10% SOC as high as 0.72, which is much higher than that of Examples 1-9.

[0189] The positive electrode material in the secondary battery of Examples 1-9 mixes polyanions with lithium sulfide. The addition of polyanions reduces the p-orbital energy of sulfur ions in lithium sulfide, thereby reducing the covalency of the compound system, reducing the hybridization between d orbitals and p orbitals, and increasing the proportion of d orbitals of transition metals in the compound participating in redox reactions, so that the DCR value at 10% SOC is between 0.46 and 0.61, that is, the discharge power performance of the secondary batteries of Examples 1-9 at low SOC is greatly improved.

[0190] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode material, characterized in that: It includes an oxygen-containing compound of lithium and a lithium sulfide containing a polyanion, wherein the lithium sulfide containing a polyanion is a compound shown in Formula I: LiMS (2-x) (XO m ) x Formula I Among them, 0<x<2, 0<m≤4; M is selected from at least one of Fe, V, Nb, Zr, and Mn, and X is selected from at least one of P, Si, S, As, Mo, W, and B.

2. The positive electrode material according to claim 1, characterized in that Based on the total mass of the positive electrode material, the mass percentage of the lithium sulfide containing polyanions is 3% to 10%.

3. The positive electrode material according to claim 2, characterized in that Based on the total mass of the positive electrode material, the mass percentage of the lithium sulfide containing polyanions is 3% to 5%.

4. The positive electrode material according to claim 1, characterized in that The specific surface area of ​​the positive electrode material is 3.5 m 2 / g~7m 2 / g.

5. The positive electrode material according to any one of claims 1 to 4, characterized in that The lithium oxygen-containing compound includes a lithium transition metal oxide and / or a lithium-containing phosphate with an olivine structure, wherein the lithium transition metal oxide is selected from at least one 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 modified compounds thereof, and the lithium-containing phosphate with an olivine structure is selected from at least one 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

6. A method for preparing a positive electrode material, characterized in that: Provide Li2S, metal M, sulfur powder and Li2XO m The mixture is ball-milled, sieved and sintered to obtain a lithium sulfide containing a polyanion, and the lithium sulfide containing a polyanion is mixed with a lithium oxygen-containing compound to obtain a positive electrode material; Wherein, the positive electrode material is a lithium sulfide containing a polyanion having formula I: LiMS (2-x) (XO m ) x Formula I 0<x<2, 0<m≤4; M is selected from at least one of Fe, V, Nb, Zr, and Mn, and X is selected from at least one of P, Si, S, As, Mo, W, and B.

7. The preparation method according to claim 6, characterized in that: In the ball milling step, the ball milling time is 24h to 48h, the ball milling speed is 500r to 800r, and the ball-to-material ratio is 50:1 to 100:

1.

8. A positive electrode sheet, characterized in that: The positive electrode material comprises the positive electrode material described in any one of claims 1 to 5 or the positive electrode material prepared by the method for preparing the positive electrode material described in any one of claims 6 to 7.

9. A secondary battery, characterized in that: Including the positive electrode sheet as described in claim 8.

10. A battery module, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

11. A battery pack, characterized in that: Comprising the battery module as claimed in claim 10.

12. An electrical device, characterized in that: It comprises at least one selected from the positive electrode sheet of claim 8, the secondary battery of claim 9, the battery module of claim 10, and the battery pack of claim 11.

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