Positive electrode composite material, preparation method thereof, secondary battery and electric device
By coating lithiated organic sulfur compounds on lithium iron phosphate materials, the existing lithium supplementation methods have solved the complex process and high cost problems, the specific energy and electrochemical performance of lithium batteries have been improved, and process simplification and cost reduction have been achieved.
Patent Information
- Application Number
- CN202311766965.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-20
- Publication Date
- 2025-06-20
AI Technical Summary
The existing lithium supplementation method has complex processes and high cost, and the electrochemical performance of lithium iron phosphate positive electrode materials is poor, which limits the increase in the energy density of lithium-ion batteries.
Lithium iron phosphate material is coated with lithiated organic sulfur compounds to form a cladding layer, which improves interface conductivity and provides an additional lithium source.
Through the use of the lithiated organic sulfur compound coating, the specific energy of the lithium battery is improved, the electrochemical performance is improved, the process is simplified, and the cost is reduced.
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Figure BDA0004620990820000091
Abstract
Description
Technical Field
[0001] The present invention relates to the field of preparation of cathode materials for lithium - ion batteries. Specifically, it relates to a cathode composite material, a preparation method thereof, a secondary battery, and an electrical device. Background Art
[0002] With the popularization of new - energy vehicles, consumers and vehicle manufacturers have higher and higher requirements for the cruising range, which puts forward higher requirements for the energy density of lithium - ion batteries. Lithium iron phosphate batteries are favored by manufacturers due to their high safety, low price, long life, etc. However, the actual application capacity of lithium iron phosphate cathode materials has approached their theoretical specific capacity, which brings a bottleneck to the improvement of the energy density of lithium iron phosphate batteries. Especially in the application of silicon - doped anodes, a large amount of reversible lithium is consumed for film formation, so it is necessary to develop a lithium - supplementing technology for the lithium iron phosphate battery system to provide an additional lithium source for film - forming consumption. Summary of the Invention
[0003] The present invention aims to provide a cathode composite material, a preparation method thereof, a secondary battery, and an electrical device to solve the problems that the existing lithium - supplementing methods are complex in process, high in cost, and the electrochemical performance of the cathode material is poor.
[0004] In the first aspect of the present application, a cathode composite material is provided. The cathode composite material includes a cathode material body and a coating layer coated on the surface of the cathode material body. The coating layer includes a lithiated organic sulfur compound.
[0005] In the second aspect of the present application, a preparation method of a cathode composite material is also provided. The preparation method includes: Step S1: Mix an organic sulfur polymer and a lithium - containing compound and carry out a lithiation reaction to obtain a lithiated organic sulfur compound; Step S2: Make the lithiated organic sulfur compound coat on the surface of the cathode material body to form a coating layer, and obtain the cathode composite material.
[0006] In the third aspect of the present application, a secondary battery is also provided, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The positive electrode plate includes the above - mentioned cathode composite material or the cathode composite material prepared by the above - mentioned preparation method of the cathode composite material.
[0007] In the fourth aspect of the present application, an electrical device is also provided. The electrical device includes the above - mentioned secondary battery.
[0008] Advantageous Effects:
[0009] Coating lithium iron phosphate materials with lithiated organic sulfur compounds has two functions: First, the lithiated organic sulfur compounds have a conductive polymer as the main chain and have good conductivity themselves. Using this as a coating layer can not only improve the interfacial conductivity, but also slow down the destruction of the surface structure of the cathode material body (lithium iron phosphate particles). Second, the above coating layer can act as a lithium source to provide additional lithium. When the above cathode composite material is first charged during battery formation, the lithium in the coating layer will be released (the de-lithiation platform is about 2.0 V), which is used for the consumption or insertion reaction of the negative electrode film formation, so as to make up for the consumption of lithium during the first charging process of the negative electrode surface film formation and improve the specific energy of the lithium battery. In addition, compared with the existing cathode materials, the cathode composite material with the above structure has more excellent electrochemical performance, and the preparation process is also simpler and the cost is lower. Detailed implementation mode
[0010] For the sake of simplicity, only some numerical ranges are specifically disclosed in this article. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recorded.
[0011] In the description of this article, unless otherwise specified, "above" and "below" include the present number.
[0012] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various common measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of this application). It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other.
[0013] Existing lithium compensation methods have problems such as complex processes, high costs, and poor electrochemical performance of the cathode materials. In order to overcome the above technical problems, this application provides a cathode composite material, which includes a cathode material body and a coating layer coated on the surface of the cathode material body, and the coating layer includes lithiated organic sulfur compounds.
[0014] Coating the lithium iron phosphate material with a lithiated organic sulfur compound has two functions: First, the lithiated organic sulfur compound has a conductive polymer as the main chain and has good electrical conductivity itself. As a coating layer, it can not only improve the interfacial conductivity, but also slow down the destruction of the surface structure of the cathode material body (lithium iron phosphate particles). Second, the above coating layer can serve as a lithium source to provide additional lithium. When the above cathode composite material is first charged during battery formation, the lithium in the coating layer will be removed (the de-lithiation platform is about 2.0 V), which is used for film formation consumption or insertion reaction at the negative electrode, so as to make up for the lithium consumption of the film formation on the negative electrode surface during the first charging process of the battery and improve the specific energy of the lithium battery. In addition, compared with the existing cathode materials, the cathode composite material with the above structure has more excellent electrochemical performance, and the preparation process is also simpler and the cost is lower.
[0015] There are many types of organic sulfides suitable for preparing the lithiated organic sulfur compound of the present application. Taking polyacrylonitrile sulfide as an example, the principle of lithium deintercalation and intercalation is as follows: during electrochemical reduction, sulfur atoms gain electrons to break the S-S bond, forming sulfur anions, which combine with Li + ; during electrochemical oxidation, the product formed by sulfur anions and Li + loses electrons and reforms the S-S bond, and Li + is removed. This electrochemical reaction is reversible. Therefore, sulfur-containing organic compounds have a function similar to that of the cathode material for lithium deintercalation and intercalation. In order to enable the coating layer to provide an additional lithium source, the sulfur-containing organic compound is pre-lithiated by a chemical method, that is, sulfur anions are combined with Li + ; during the first electrochemical reduction, Li + can be removed and used for film formation consumption or insertion into the negative electrode at the negative electrode, thus realizing the lithium compensation function.
[0016] In some embodiments of the present application, polyacrylonitrile sulfide can be prepared by the following method: appropriate amounts of monomer acrylonitrile and sublimed sulfur are subjected to low-energy ball milling, wherein the weight ratio of monomer acrylonitrile to sublimed sulfur is 1:3 to 1:8, the ball milling speed is 50 r / min to 1000 r / min, and the ball milling time is 4 h to 20 h; the ball-milled mixture is sintered, the sintering temperature is 200 °C to 500 °C, and the sintering time is 5 h to 24 h.
[0017] In some embodiments of the present application, in the cathode composite material, the mass percentage content of the coating layer is 0.5% to 5%. Compared with other ranges, limiting the content of the coating layer within the above range is beneficial to further improving the structural stability of the cathode composite material, and thus can extend its cycle life.
[0018] In some embodiments of the present application, the mass percentage of lithium element in the coating layer is 0.5% to 5%. Compared with other ranges, limiting it within the above range is beneficial to better achieve the effect of lithium supplementation, thereby improving the specific energy of the lithium battery.
[0019] In some embodiments of the present application, the mass percentage of sulfur element in the coating layer is 3% to 8%. The sulfur content with lithium will affect the conductivity of the positive electrode composite material. If the content is too high, the conductivity of the positive electrode composite material is poor; if the sulfur content is too low, the capacity of the positive electrode composite material will decrease. The mass percentage of sulfur element in the coating layer includes but is not limited to the above range, and limiting it within the above range is beneficial to obtaining a positive electrode composite material with both good conductivity and capacity. The mass percentage of lithium element in the coating layer is 3%, 4%, 5%, 6%, 7%, 8%, or the range formed by any two of the above values.
[0020] In some embodiments of the present application, the lithiated organic sulfur compound is prepared from an organic sulfur polymer and a lithium-containing compound. Exemplarily, the organic sulfur polymer includes one or more of benzene-based organic sulfur polymers, heterocyclic organic sulfur polymers, and olefin-based organic sulfur polymers. Preferably, the organic sulfur polymer includes one or more of polystyrene sulfide, epoxy group-substituted polystyrene sulfide, and polypropylene sulfide. Compared with chain-like lithiated organic sulfur compounds, benzene-based organic sulfur polymers and heterocyclic organic sulfur have a more stable structure of the coating layer formed on the positive electrode composite material due to the presence of benzene rings and heterocyclic rings, which is beneficial to further extending the cycle life of the battery and improving its capacity retention rate during subsequent applications.
[0021] In some embodiments of the present application, the lithium-containing compound includes an aryl lithium compound, and the aryl lithium compound includes at least one of phenyl lithium and biphenyl lithium, preferably one or more of 1-methylphenyl lithium, biphenyl lithium, and ethyl biphenyl lithium.
[0022] The second aspect of the present application also provides a method for preparing a positive electrode composite material, the method comprising:
[0023] Step S1: Mix the organic sulfur polymer and the lithium-containing compound and then carry out a lithiation reaction to obtain a lithiated organic sulfur compound;
[0024] Step S2: Coat the lithiated organic sulfur compound on the surface of the positive electrode material body to form a coating layer, thereby obtaining a positive electrode composite material.
[0025] In some embodiments of the present application, the method for preparing the positive electrode composite material satisfies at least one of the following conditions:
[0026] (1) Step S1 includes: preparing a first solution comprising an organic sulfur polymer, a lithium-containing compound, and an organic solvent, and heating the first solution at a preset temperature under an inert atmosphere for reaction to obtain a lithiated organic sulfur compound;
[0027] (2) Step S2 includes: mixing the lithiated organic sulfur compound with the main body of the positive electrode material and subjecting it to ball milling treatment or hydrothermal treatment, so that the lithiated organic sulfur compound coats the surface of the main body of the positive electrode material to form a coating layer.
[0028] Compared with the existing method, the present application uses a chemical method to form a coating layer with a lithium deintercalation function. The whole method has a simple process, is suitable for mass production, has a relatively short process flow, is easy to control the composition during the reaction process, and has a low cost.
[0029] In some embodiments of the present application, in order to further improve the reaction rate and the conversion rate of raw materials, in Step S1, the volume ratio of the lithium-containing compound to the organic solvent is 1:5 to 1:20, and the mass percentage of the organic sulfur polymer in the first solution is 5 wt% to 20 wt%. Optionally, the volume ratio of the lithium-containing compound to the organic solvent is 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, or the range formed by any two of the above values.
[0030] In some embodiments of the present application, in Step S1, the preset temperature is 60°C to 120°C. The preset temperature includes but is not limited to the above range, and limiting it within the above range is beneficial to further improving the conversion rate of the lithiated organic sulfur compound, and at the same time can also inhibit the generation of other substances that are not conducive to lithium ion deintercalation. Optionally, the preset temperature is 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or the range formed by any two of the above values.
[0031] In some embodiments of the present application, in order to further improve the coating effect during the ball milling process, in Step S2, during the ball milling treatment, the ball milling speed is 1500 r / min to 5000 r / min, the particle size of the grinding medium is 5 mm to 35 mm, and the grinding time is 10 h to 48 h; Optionally, the ball milling speed is 1500 r / min, 2000 r / min, 2500 r / min, 3000 r / min, 3500 r / min, 4000 r / min, 4500 r / min, and 5000 r / min, or the range formed by any two of the above values; the grinding time is 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 48 h, or the range formed by any two of the above values.
[0032] In some embodiments of the present application, in step S2, the hydrothermal treatment includes mixing the cathode material body, the lithiated organic sulfur compound, and a 1,2-dimethoxyethane solution, and placing them in a hydrothermal reaction kettle for hydrothermal reaction. After filtration and drying, a cathode composite material is obtained. Among them, the hydrothermal reaction temperature is 60-90 °C, and the reaction time is 4h-26h. Limiting the temperature and time of the hydrothermal reaction within the above ranges is beneficial to further improving the coating amount and coating uniformity of the coating layer.
[0033] In some embodiments of the present application, the cathode material body can be selected from the types commonly used in the art, including but not limited to one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, and lithium manganate.
[0034] The third aspect of the present application also provides a secondary battery, including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The positive electrode plate includes the above-mentioned cathode composite material or the cathode composite material prepared by the above-mentioned preparation method.
[0035] According to some embodiments of the present application, the secondary battery is a lithium metal secondary battery. In some embodiments, the lithium metal secondary battery includes, but is not limited to: lithium ion secondary battery, lithium polymer secondary battery, or lithium ion polymer secondary battery.
[0036] According to some embodiments of the present application, the secondary battery may include an outer package, and the outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as one or several of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
[0037] According to some embodiments of the present application, the shape of the secondary battery is not particularly limited, and it can be cylindrical, square, or any other shape.
[0038] The fourth aspect of the present application also provides an electrical device, and the electrical device includes the above-mentioned secondary battery.
[0039] In some embodiments, the above-mentioned electrical device includes, but is not limited to: electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, energy storage systems, etc. In order to meet the high power and high energy density requirements of the device for the secondary battery, a battery pack or a battery module can be used.
[0040] In some other embodiments, the device can be a mobile phone, a tablet computer, a laptop computer, etc. The device usually requires thin and light, and a secondary battery can be used as the power source.
[0041] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.
[0042] Example 1
[0043] A method for lithium supplementation of lithium iron phosphate cathode, the method comprising the following steps:
[0044] (1) Preparation of sulfurized polyacrylonitrile:
[0045] Perform low-energy ball milling on monomer acrylonitrile and sublimed sulfur, wherein the weight ratio of monomer acrylonitrile to sublimed sulfur is 1:5, the ball milling speed is 800 r / min, and the ball milling time is 12 h; sinter the ball-milled mixture, the sintering temperature is 300 °C, and the sintering time is 12 h to obtain sulfurized polyacrylonitrile.
[0046] (2) Prelithiation reaction:
[0047] Mix lithium-containing biphenyl with 1,2-dioxymethylethane in a volume ratio of 1:8 to obtain a mixed solution, add sulfurized polyacrylonitrile to the mixed solution to obtain a first solution with a mass percentage of sulfurized polyacrylonitrile of 6 wt%, and react the first solution in an argon environment, the preset temperature is 80 °C, to obtain a lithiated organic sulfur compound.
[0048] (3) Coating:
[0049] Mix the cathode lithium iron phosphate with lithiated sulfur-containing polyacrylonitrile to obtain a mixture, wherein the weight ratio of the cathode lithium iron phosphate to lithiated sulfur-containing polyacrylonitrile is 1:0.008; ball mill the above mixture, the ball milling speed is 3000 r / min, and the ball milling time is 24 h.
[0050] Example 2
[0051] The difference from Example 1 is that the organic sulfur polymer is sulfurized polystyrene propylene. Others are the same as in Example 1.
[0052] Example 3
[0053] The difference from Example 1 is that the organic sulfur polymer is polystyrene propylene sulfide substituted with epoxy groups. Others are the same as in Example 1.
[0054] Example 4
[0055] The difference from Example 1 is that the organic sulfur polymer is sulfurized polypropylene. Others are the same as in Example 1.
[0056] Example 5
[0057] The difference from Example 1 is that the preset temperature is 60 °C, and the volume ratio of the lithium-containing compound to the organic solvent is 1:20.
[0058] Example 6
[0059] The differences from Example 1 are as follows: the preset temperature is 120 °C, and the volume ratio of the lithium-containing compound to the organic solvent is 1:5.
[0060] Example 7
[0061] The differences from Example 1 are as follows: the preset temperature is 140 °C, and the volume ratio of the lithium-containing compound to the organic solvent is 1:3.
[0062] Example 8
[0063] The differences from Example 1 are as follows:
[0064] The specific process of coating by hydrothermal method is as follows: mix the cathode lithium iron phosphate material, lithiated sulfur-containing polyacrylonitrile and 1,2-dimethoxyethane solution evenly in a hydrothermal reaction kettle. The weight ratio of the lithium iron phosphate material to the lithiated sulfur-containing polyacrylonitrile is 1:0.008, the hydrothermal reaction temperature is 85 °C, and the reaction time is 12 h; filter and dry the reacted material to obtain lithium iron phosphate with a coating layer.
[0065] Example 9
[0066] The differences from Example 8 are as follows: the sulfur element content in the coating layer is 2%.
[0067] Example 10
[0068] The differences from Example 8 are as follows: the lithium element content in the coating layer is 0.3%.
[0069] Comparative Example 1
[0070] Directly mix lithiated sulfurized polyacrylonitrile with the cathode material lithium iron phosphate as the cathode active material, and the others are the same as in Example 1.
[0071] Prepare the cathode active materials obtained in the examples and comparative examples into lithium-ion batteries. The performance is shown in Table 1. The control group is a lithium-ion battery prepared from lithium iron phosphate without a coating layer, and other parameters remain unchanged.
[0072] Preparation of lithium-ion battery:
[0073] Preparation of the cathode electrode sheet: Respectively take the cathode active materials obtained in the examples and comparative examples as the cathode active material, mix them with the binder polyvinylidene fluoride (PVDF) and the conductive agent conductive carbon black according to the weight ratio of cathode active material: binder PVDF: conductive agent = 96:2:2, add N-methylpyrrolidone (NMP), and mix them by a high-speed mixer to obtain a cathode slurry. The viscosity of the cathode slurry is 5500 cps, the fineness is 6 μm, and the solid content is 68 wt%. Uniformly coat the cathode slurry on one surface of a cathode current collector aluminum foil with a thickness of 12 μm, dry and roll it to obtain the cathode electrode sheet.
[0074] Preparation of the negative electrode sheet: Graphite and silicon oxide (SiO x , where 0.5 ≤ x ≤ 1.5) are blended as the negative electrode active material (Si / C = 5:95). The negative electrode active material, binder (a mixture of styrene-butadiene rubber SBR, thickener sodium carboxymethyl cellulose CMCNa, and polyacrylic acid PAA, with a mass ratio of 1:1:0.5), and conductive agent conductive carbon black are mixed according to the ratio of negative electrode active substance: binder: conductive agent (mass ratio) = 96:2.5:1.5. Ultra-pure water is added, and the negative electrode slurry is obtained through a high-speed mixer. The viscosity of the negative electrode slurry is 6000 cps, the fineness is 20 μm, and the solid content is 40 wt%. The negative electrode slurry is uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 8 μm, dried, and rolled to obtain the negative electrode sheet.
[0075] Preparation of the electrolyte: Dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 1:1:1 as the solvent, 1 mol / L LiPF6 is used as the lithium salt, and 5% by mass of vinylene carbonate (VC) is added as an additive to obtain the electrolyte.
[0076] Separator: A 11-μm-thick PE porous polymer separator is used.
[0077] Preparation of the lithium-ion battery: After cutting the negative electrode sheet into a size of 48 mm × 57 mm and the positive electrode sheet into a size of 46 mm × 54 mm, they are stacked together with the separator. After assembling into a bare battery cell, the electrode tabs are welded, and it is assembled into an aluminum-plastic film. Then, liquid injection, standing, formation, and grading are carried out to manufacture the lithium-ion battery.
[0078] The performance tests are as follows:
[0079] (1) Determination of the cycle capacity retention rate:
[0080] 1) The lithium-ion battery is left standing at 25°C for 3 h;
[0081] 2) Discharge at 1.0C to 2.5V;
[0082] 3) After standing for 30 min, charge at 0.5C CC-CV to 3.75V, with a cut-off current of 0.05C;
[0083] 4) After standing for 30 min, discharge at 1.0C CC to 2.5V;
[0084] 5) Repeat steps 3) and 4) for a total of 1000 times;
[0085] 6) The cycle capacity retention rate after 1000 cycles = the discharge capacity at the 1000th cycle / the discharge capacity at the first cycle * 100%.
[0086] (2) Specific energy test:
[0087] 1) Weigh the lithium-ion battery;
[0088] 2) Let the lithium-ion battery stand still at 25 °C for 3 h;
[0089] 3) Discharge at 0.33C until 2.5V;
[0090] 4) After standing still for 30 min, charge at 0.33C CC-CV to 3.75V, and the cut-off current is 0.05C;
[0091] 5) After standing still for 30 min, discharge at 0.33C CC until 2.5V;
[0092] 6) The specific energy of the battery is the discharge energy in step 5) / the weight of the battery cell.
[0093] (3) Determination of the contents of sulfur and lithium elements in the coating layer
[0094] Measured by the Plasma 3000 ICP tester of GRNAR.
[0095] The test results are shown in Table 1.
[0096] Table 1
[0097]
[0098] By comparing Examples 1 to 10, Comparative Example 1 and the control group, it can be seen that the positive electrode composite material provided by this application has more excellent electrochemical performance. At the same time, using the preferred types of organic sulfur compounds and the preferred preset temperature range in this application is beneficial to further improving the electrochemical performance of the positive electrode composite material.
[0099] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order other than those described here.
[0100] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A positive electrode composite material, characterized in that, The positive electrode composite material includes a positive electrode material body and a coating layer coated on the surface of the positive electrode material body, and the coating layer includes a lithiated organic sulfur compound.
2. The positive electrode composite material according to claim 1, characterized in that, The positive electrode composite material satisfies at least one of the following conditions: (1) In the positive electrode composite material, the mass percentage of the coating layer is 0.5% to 5%; (2) In the coating layer, the mass percentage of lithium element is 0.5% to 5%; (3) In the coating layer, the mass percentage of sulfur element is 3% to 8%.
3. The positive electrode composite material according to claim 1, characterized in that, The lithiated organic sulfur compound is prepared from an organic sulfur polymer and a lithium-containing compound.
4. The positive electrode composite material according to claim 3, characterized in that, The organic sulfur polymer includes one or more of benzene-based organic sulfur polymers, heterocyclic organic sulfur polymers, and olefin-based organic sulfur polymers; The lithium-containing compound includes aryl lithium compounds.
5. The positive electrode composite material according to claim 4, characterized in that, The organic sulfur polymer includes one or more of polystyrene sulfide, epoxy group-substituted polystyrene sulfide, and polypropylene sulfide; The lithium-containing compound includes one or more of phenyl lithium and biphenyl lithium.
6. A method for preparing the positive electrode composite material according to any one of claims 1 to 5, characterized in that, The preparation method includes: Step S1: Mix the organic sulfur polymer and the lithium-containing compound and carry out a lithiation reaction to obtain a lithiated organic sulfur compound; Step S2: Coating the lithiated organic sulfur compound on the surface of the positive electrode material body to form a coating layer to obtain the positive electrode composite material.
7. The method for preparing the positive electrode composite material according to claim 6, characterized in that, The preparation method satisfies at least one of the following conditions: (1) Step S1 includes: preparing a first solution including an organic sulfur polymer, a lithium-containing compound, and an organic solvent, and heating the first solution at a preset temperature under an inert atmosphere for reaction to obtain the lithiated organic sulfur compound; (2) Step S2 includes: mixing the lithiated organic sulfur compound with the positive electrode material body and performing ball milling treatment or hydrothermal treatment to coat the lithiated organic sulfur compound on the surface of the positive electrode material body to form the coating layer.
8. The method for preparing the positive electrode composite material according to claim 7, characterized in that, The preparation method satisfies at least one of the following conditions; (1) In Step S1, the volume ratio of the lithium-containing compound to the organic solvent is 1:5 to 1:20, and the mass percentage of the organic sulfur polymer in the first solution is 5wt% to 20wt%; (2) In Step S1, the preset temperature is 60°C to 120°C; (3) In Step S2, in the ball milling treatment, the rotation speed of the ball milling treatment is 1500r / min to 5000r / min, and the time of the ball milling treatment is 10h to 48h; (4) In Step S2, the hydrothermal treatment includes: performing a hydrothermal reaction on the lithiated organic sulfur compound, the positive electrode material body, and a 1,2-dimethoxyethane solution in a hydrothermal reactor to obtain the positive electrode composite material, the reaction temperature of the hydrothermal reaction is 60°C to 90°C, and the reaction time of the hydrothermal reaction is 4h to 26h.
9. A secondary battery, comprising a positive electrode plate, a negative electrode plate, a separator and an electrolyte, characterized in that, The positive electrode sheet includes the positive electrode composite material according to any one of claims 1 to 5 or the positive electrode composite material prepared by the preparation method of the positive electrode composite material according to any one of claims 6 to 8.
10. An electrical device, characterized in that, The electrical device includes the secondary battery according to claim 9.