Preparation method of red phosphorus modified lithium-rich manganese-based positive electrode material, positive electrode sheet and lithium ion battery
By using elemental doping and coating methods to modify lithium-rich manganese-based cathode materials with red phosphorus, problems such as lattice oxygen loss and interfacial side reactions have been solved, improving the electrochemical performance and cycle stability of the materials and achieving high-efficiency battery performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNIV OF SCI & TECH OF CHINA
- Filing Date
- 2024-08-30
- Publication Date
- 2026-06-19
AI Technical Summary
Existing lithium-rich manganese-based cathode materials suffer from problems such as lattice oxygen loss, interfacial side reactions, poor ionic conductivity, and spinel phase transition during long cycles, resulting in low initial coulombic efficiency, severe voltage decay, poor rate performance, and poor cycle stability, making it difficult to meet the requirements of high-energy-density batteries.
A red phosphorus modification method was used to dope and coat lithium-rich manganese-based cathode materials. By mixing with red phosphorus under vacuum and calcining at high temperature, a phosphate coating and spinel structure were formed, achieving phosphorus doping and improving the electrochemical performance of the material.
This improved the initial coulombic efficiency, reversible specific capacity, and long-cycle stability of lithium-rich manganese-based cathode materials, thereby enhancing the electrochemical performance and structural stability of the materials.
Smart Images
Figure CN119133389B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of cathode material preparation technology, and particularly relates to a method for preparing a red phosphorus-modified lithium-rich manganese-based cathode material, a cathode sheet, and a lithium-ion battery. Background Technology
[0002] Electrochemical energy storage plays an indispensable role in energy storage systems, and battery materials determine the overall performance of the battery and energy storage module. Advanced battery materials must meet five major requirements: high power density, high energy density, low cost, long lifespan, and environmental friendliness. Currently, traditional cathodes suffer from low specific capacity (<200mAh g / g). -1 The reasons for this are not fully sufficient to meet the rapid development of high-energy-density batteries. Among layered oxide cathode materials derived from LiCoO2, lithium-rich manganese-based cathodes exhibit higher actual specific capacity and energy density. To meet the increasing energy demands for longer driving ranges, the development of batteries exceeding 500 Wh / kg capacity is needed. -1 High-capacity cathode materials are essential.
[0003] Lithium-rich manganese-based cathodes stand out as the most promising next-generation cathode materials due to their extremely high specific capacity and energy density, as well as their advantages of high voltage and low cost. However, their commercialization is currently difficult due to factors such as severe lattice oxygen loss, severe interfacial side reactions, poor ionic conductivity, and spinel phase transitions during long cycles. These problems lead to low initial coulombic efficiency, severe voltage decay, and poor rate performance and cycle stability. In particular, voltage decay increases the difficulty of implementing battery management systems in practical applications.
[0004] To address these issues, researchers have proposed a series of solutions for lithium-rich manganese-based cathode materials, including elemental doping, coating and surface treatment, and optimization of synthesis methods. However, using a single solution often only solves one of the problems and is unlikely to achieve better results. Therefore, developing a solution that can simultaneously perform elemental doping and coating is of great significance for improving the cycle stability and electrochemical performance of lithium-rich cathode materials. Summary of the Invention
[0005] In view of this, the purpose of the present invention is to provide a method for preparing a lithium-rich manganese-based cathode material modified with red phosphorus, a cathode sheet and a lithium-ion battery. The preparation method achieves dual modification of element doping and coating, and the process is simple. The cycle stability and first coulombic efficiency of the lithium-rich manganese-based cathode material treated with red phosphorus at high temperature are effectively improved.
[0006] This invention provides a method for preparing a red phosphorus-modified lithium-rich manganese-based cathode material, comprising the following steps:
[0007] Lithium-rich manganese-based cathode material was mixed with red phosphorus at a mass ratio of 1:0.001 to 0.01 and calcined at 300 to 600°C for 1 to 6 hours under vacuum to obtain red phosphorus-modified lithium-rich manganese-based cathode material.
[0008] The general chemical formula of the lithium-rich manganese-based cathode material is: Li 1+x Mn 1-x1 Ni 1-x2 Co 1-x3 O2, x=0.01~0.3, 2+x=x1+x2+x3, x1=0.3~0.6, x2=0.7~1, x3=0.8~1.
[0009] Preferably, the particle size of the red phosphorus is 10–200 μm;
[0010] Red phosphorus is in a gaseous state.
[0011] Preferably, the vacuum degree under the vacuum condition is 0.01MPa to 0.2MPa.
[0012] Preferably, the temperature is increased to 300-600°C at a heating rate of 2-8°C / min.
[0013] Preferably, the lithium-rich manganese-based cathode material is: Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.
[0014] Preferably, the lithium-rich manganese-based cathode material is prepared according to the following method:
[0015] Nickel, manganese, cobalt, and lithium salts were dissolved in a mixed solution of acrylic acid and deionized water. An aqueous solution of ammonium persulfate was added, and the mixture was stirred for 55–65 minutes. The temperature was then raised to 80°C and held for 170–190 minutes to allow the reaction to proceed. The temperature was then raised to 120°C and held for 11–13 hours to allow the mixture to dry. The mixture was then ground and subjected to a two-stage calcination: the first stage calcination was carried out at 300–600°C for 3–7 hours, and the second stage calcination was carried out at 750–950°C for 9–15 hours.
[0016] This invention provides a positive electrode sheet, which is prepared by coating a positive electrode slurry onto a positive electrode current collector;
[0017] The cathode slurry includes the lithium-rich manganese-based cathode material modified with red phosphorus prepared by the above-mentioned technical solution preparation method.
[0018] This invention provides a lithium-ion battery, comprising a negative electrode, an electrolyte, a separator, and a positive electrode as described in the above technical solution.
[0019] Preferably, the separator is a PP separator; the negative electrode is a lithium metal sheet;
[0020] The electrolyte contains LiPF6 as the lithium salt and a 1:1 volume ratio EC / DEC mixed solvent.
[0021] This invention provides a method for preparing a lithium-rich manganese-based cathode material modified with red phosphorus, comprising the following steps: mixing a lithium-rich manganese-based cathode material with red phosphorus at a mass ratio of 1:0.001 to 0.01, and calcining the mixture at 300 to 600°C for 1 to 6 hours under vacuum to obtain the red phosphorus-modified lithium-rich manganese-based cathode material; the general chemical formula of the lithium-rich manganese-based cathode material is: Li 1+ x Mn 1-x1 Ni 1-x2 Co 1-x3 O2, x = 0.01–0.3, 2+x = x1+x2+x3, x1 = 0.3–0.6, x2 = 0.7–1, x3 = 0.8–1. This method uses inexpensive raw materials and has a simple reaction process. After red phosphorus is sublimated by high-temperature heating, it undergoes a gas-solid interface reaction with the lithium-rich manganese-based cathode material, forming a phosphate coating on the cathode surface. Simultaneously, spinel and oxygen vacancies are formed, achieving P doping within the cathode. This effectively improves the reversibility and structural stability of the anion redox reaction of the lithium-rich manganese-based cathode material, enhancing the initial coulombic efficiency, reversible specific capacity, and long-term cycling stability. Experimental results show that the lithium-rich manganese-based cathode material of this invention has a discharge specific capacity of 250–300 mAh / g at a current density of 0.1C and 180–250 mAh / g at a current density of 1C. The capacity retention rate after 300 cycles at a current density of 1C is 75%–95%. Attached Figure Description
[0022] Figure 1 The XRD pattern of the material prepared in Example 1 of this invention;
[0023] Figure 2 SEM image of the material prepared in Example 1 of this invention;
[0024] Figure 3 The discharge specific capacity curves of the materials prepared in Example 1 and Comparative Example 1 of this invention are shown under 0.1C charge-discharge conditions.
[0025] Figure 4 The figures show the discharge specific capacity cycling diagrams of the materials prepared in Example 1 and Comparative Example 1 under 1C charge-discharge conditions.
[0026] Figure 5 The discharge specific capacity cycling diagram of the material prepared in Example 2 of this invention under 1C charge-discharge conditions is shown.
[0027] Figure 6 The discharge specific capacity cycling diagram of the material prepared in Example 3 of this invention under 1C charge-discharge conditions is shown.
[0028] Figure 7 This is a discharge specific capacity cycling diagram of the material prepared in Comparative Example 2 of this invention under 1C charge-discharge conditions;
[0029] Figure 8 This is a discharge specific capacity cycling diagram of the material prepared in Comparative Example 3 of this invention under 1C charge-discharge conditions;
[0030] Figure 9 This is a discharge specific capacity cycling diagram of the material prepared in Comparative Example 4 of this invention under 1C charge-discharge conditions. Detailed Implementation
[0031] This invention provides a method for preparing a red phosphorus-modified lithium-rich manganese-based cathode material, comprising the following steps:
[0032] Lithium-rich manganese-based cathode material was mixed with red phosphorus at a mass ratio of 1:0.001 to 0.01 and calcined at 300 to 600°C for 1 to 6 hours under vacuum to obtain red phosphorus-modified lithium-rich manganese-based cathode material.
[0033] The general chemical formula of the lithium-rich manganese-based cathode material is: Li 1+x Mn 1-x1 Ni 1-x2 Co 1-x3 O2, x=0.01~0.3, 2+x=x1+x2+x3, x1=0.3~0.6, x2=0.7~1, x3=0.8~1.
[0034] The preparation method provided by this invention uses inexpensive raw materials and has a simple reaction process. After red phosphorus is sublimated by high-temperature heating, it undergoes a gas-solid interface reaction with lithium-rich manganese-based cathode material, forming a phosphate coating on the cathode surface and simultaneously creating spinel and oxygen vacancies, thus achieving P doping inside the cathode. This effectively improves the reversibility and structural stability of the anion redox reaction of the lithium-rich manganese-based cathode material, and enhances the material's initial coulombic efficiency, reversible specific capacity, and long-term cycle stability.
[0035] In this invention, the mass ratio of the lithium-rich manganese-based cathode material to the phosphorus source is 1:0.001 to 0.01. The red phosphorus has a particle size of 10 to 200 μm and is in a gaseous state.
[0036] The general chemical formula of the lithium-rich manganese-based cathode material described in this invention is: Li 1+x Mn 1-x1 Ni 1-x2 Co 1-x3O2, x = 0.01–0.3, 2+x = x1+x2+x3, x1 = 0.3–0.6, x2 = 0.7–1, x3 = 0.8–1. This invention uses a cobalt-containing lithium-rich manganese-based cathode material combined with red phosphorus, which can improve the material's initial coulombic efficiency, reversible specific capacity, and long-cycle stability. In a specific embodiment of this invention, the lithium-rich manganese-based cathode material used is: Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.
[0037] The lithium-rich manganese-based cathode material described in this invention is prepared by the following method:
[0038] Nickel, manganese, cobalt, and lithium salts were dissolved in a mixed solution of acrylic acid and deionized water. An aqueous solution of ammonium persulfate was added, and the mixture was stirred for 55–65 minutes. The temperature was then raised to 80°C and held for 170–190 minutes to allow the reaction to proceed. The temperature was then raised to 120°C and held for 11–13 hours to allow the mixture to dry. The mixture was then ground and subjected to a two-stage calcination: the first stage calcination was carried out at 300–600°C for 3–7 hours, and the second stage calcination was carried out at 750–950°C for 9–15 hours.
[0039] In this invention, lithium-rich manganese-based cathode material is mixed evenly with red phosphorus and then added to a quartz tube. The gas in the quartz tube is extracted, and the quartz tube opening is sealed by high-temperature melting, so that the tube is in a vacuum state; the vacuum degree in the vacuum state is 0.01MPa to 0.2MPa.
[0040] The quartz tube containing the material is then placed in a muffle furnace for calcination; the calcination temperature is 300–600°C, preferably 430–600°C; the calcination time is 1–6 h, preferably 1–5 h. Preferably, the temperature is raised to 300–600°C at a heating rate of 2–8°C / min; in specific embodiments, the heating rates are 2°C / min, 3°C / min, and 5°C / min; the calcination temperatures are 450°C, 500°C, and 600°C; and the calcination times are 3 h, 2 h, and 4 h.
[0041] This invention provides a positive electrode sheet, which is prepared by coating a positive electrode slurry onto a positive electrode current collector;
[0042] The cathode slurry includes the lithium-rich manganese-based cathode material modified with red phosphorus prepared by the preparation method described in the above technical solution.
[0043] The positive electrode slurry also includes a conductive agent, a binder, and a solvent; the mass ratio of the red phosphorus-modified lithium-rich manganese-based positive electrode material, the conductive agent, and the binder is 8:1:1. The conductive agent is Super P, the binder is polyvinylidene fluoride, and the solvent is N-methylpyrrolidone (NMP).
[0044] In this invention, the positive electrode slurry is preferably coated onto a positive electrode current collector aluminum foil with a thickness of 15 μm. The positive electrode sheet is preferably dried in an oven at a temperature of 110–130 °C, and the diameter of the positive electrode sheet is 12 mm.
[0045] The present invention also provides a lithium-ion battery, comprising a negative electrode, an electrolyte, a separator, and a positive electrode as described in the above technical solution.
[0046] The separator is a PP separator; the negative electrode is a lithium metal sheet; the lithium salt in the electrolyte is LiPF6, and the solvent is a 1:1 volume ratio EC / DEC mixed solvent; the concentration of lithium salt in the electrolyte is 1 mol / L.
[0047] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, describes a method for preparing a red phosphorus-modified lithium-rich manganese-based cathode material, a cathode sheet, and a lithium-ion battery provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.
[0048] Comparative Example 1
[0049] This comparative example demonstrates the preparation of a lithium-rich manganese-based cathode material for lithium-ion batteries. The specific process is as follows:
[0050] 0.3857 g of nickel nitrate hexahydrate, 1.9332 g of 50 wt% manganese nitrate aqueous solution, 0.3727 g of cobalt nitrate hexahydrate, and 0.5395 g of lithium hydroxide monohydrate were dissolved in a mixed solution of 2.75 ml acrylic acid and 1.25 g deionized water. 300 μL of 5 wt% ammonium persulfate aqueous solution was added, and the mixture was stirred for 1 h. The mixture was then transferred to a forced-air drying oven and heated to 80 °C for 3 h for reaction. Subsequently, the mixture was dried in a forced-air drying oven at 120 °C for 12 h. After thorough grinding, the mixture underwent two-stage calcination in a muffle furnace: the first stage calcination was at 500 °C for 6 h; the second stage calcination was at 900 °C for 12 h. After cooling to room temperature, lithium-rich manganese-based cathode material Li was obtained. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.
[0051] Preparation of positive electrode
[0052] The above-mentioned lithium-rich manganese-based cathode material, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1. N-methylpyrrolidone (NMP) solvent was added and stirred evenly to obtain a cathode slurry. The slurry was then coated onto a cathode current collector aluminum foil with a thickness of 15 μm and dried in a vacuum oven at 120°C before being punched into a cathode sheet with a diameter of 12 mm.
[0053] Preparation of negative electrode
[0054] The negative electrode uses lithium metal directly.
[0055] Preparation of electrolyte
[0056] In an argon-atmospheric glove box (H2O < 0.01 ppm, O2 < 0.01 ppm), fully dried lithium salt LiPF6 was dissolved in EC / DEC (volume ratio 1:1) organic solvent to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.
[0057] Preparation of diaphragm
[0058] Celgard 2400 (PP) was used as the diaphragm and punched into a disc with a diameter of 16 mm.
[0059] Preparation of button batteries
[0060] In an argon-atmospheric glove box, the positive electrode, separator, and lithium metal sheet are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. 60 μL of the electrolyte is then injected to assemble a CR2032 button cell.
[0061] The lithium-rich manganese-based cathode material obtained in Comparative Example 1 was assembled into a lithium-ion half-cell, and its electrochemical performance was tested, such as... Figure 3 As shown, the material exhibits an initial coulombic efficiency of 87.3% and an initial discharge specific capacity of 265.5 mAh / g. Figure 4 As shown, the discharge specific capacity at 1C is 204.3 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 154.8 mAh / g, with a capacity retention rate of 75.8%.
[0062] Example 1
[0063] The manufacturing process of button batteries is the same as that of Comparative Example 1, except that:
[0064] Preparation of positive electrode
[0065] The lithium-rich manganese-based cathode material prepared in Comparative Example 1 was uniformly mixed with red phosphorus at a mass ratio of 1:0.005 and placed in a quartz tube. The gas inside the tube was extracted, and the quartz tube opening was sealed by high-temperature melting to create a vacuum state with a vacuum degree of 0.1 MPa. The tube was then placed in a muffle furnace and heated to 500°C at a rate of 2°C / min. After constant-temperature calcination for 3 hours, the high-temperature red phosphorus-modified lithium-rich manganese-based cathode material was obtained.
[0066] The lithium-rich manganese-based cathode material modified with high-temperature red phosphorus obtained above was used to prepare a battery according to the following method:
[0067] The lithium-rich manganese-based cathode material modified with high-temperature red phosphorus, the conductive agent Super P, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1. N-methylpyrrolidone (NMP) solvent was added and stirred evenly to obtain a cathode slurry. The slurry was then coated onto a cathode current collector aluminum foil with a thickness of 15 μm and dried in a vacuum oven at 120 °C before being punched into a cathode sheet with a diameter of 12 mm.
[0068] The lithium-rich manganese-based cathode material obtained in this example was assembled into a lithium-ion half-cell, and its electrochemical performance was tested, such as... Figure 3 As shown, the material exhibits an initial coulombic efficiency of up to 91.5% and an initial discharge specific capacity exceeding 290 mAh / g. For example... Figure 4 As shown, the discharge specific capacity at 1C is 239.8 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 223.9 mAh / g, with a capacity retention rate of 93.4%. Compared with Comparative Example 1, this high-temperature red phosphorus-modified lithium-rich manganese-based cathode material exhibits better long-cycle stability and higher anion redox reversibility.
[0069] Figure 1 and Figure 2 The XRD and SEM images of the lithium-rich manganese-based lithium-ion battery cathode material prepared in this embodiment show that it consists of single-crystal particles of hundreds of nanometers in size.
[0070] Example 2
[0071] The preparation process of the button cell is the same as in Example 1, except that:
[0072] Preparation of positive electrode
[0073] The lithium-rich manganese-based cathode material prepared in Comparative Example 1 was uniformly mixed with red phosphorus at a mass ratio of 1:0.01 and placed in a quartz tube. The gas inside the tube was extracted, and the quartz tube opening was sealed by high-temperature melting to create a vacuum state with a vacuum degree of 0.1 MPa. The tube was then placed in a muffle furnace and heated to 600°C at a rate of 5°C / min. After calcination at a constant temperature for 2 hours, the sample of Example 2 was obtained after cooling.
[0074] like Figure 5 As shown, the discharge specific capacity at 1C is 234.0 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 213.8 mAh / g, with a capacity retention rate of 91.4%.
[0075] Example 3
[0076] The preparation process of the button cell is the same as in Example 1, except that:
[0077] Preparation of positive electrode
[0078] The lithium-rich manganese-based cathode material prepared in Comparative Example 1 was uniformly mixed with red phosphorus at a mass ratio of 1:0.001 and placed in a quartz tube. The gas inside the tube was extracted, and the quartz tube opening was sealed by high-temperature melting to create a vacuum state with a vacuum degree of 0.1 MPa. The tube was then placed in a muffle furnace and heated to 450°C at a rate of 3°C / min. After constant-temperature calcination for 4 hours, the sample of Example 3 was obtained after cooling.
[0079] like Figure 6 As shown, the discharge specific capacity at 1C is 228.8 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 213.7 mAh / g, with a capacity retention rate of 93.4%.
[0080] Comparative Example 2
[0081] This comparative example demonstrates the preparation of a lithium-rich manganese-based cathode material for lithium-ion batteries. The specific process is as follows:
[0082] 0.59343 g of nickel nitrate hexahydrate, 2.14800 g of 50 wt% manganese nitrate aqueous solution, and 0.53948 g of lithium hydroxide monohydrate were dissolved in a mixed solution of 2.75 ml acrylic acid and 1.25 g deionized water. 300 μL of 5 wt% ammonium persulfate aqueous solution was added, and the mixture was stirred for 1 h. The mixture was then transferred to a forced-air drying oven and heated to 80 °C for 3 h for reaction. Subsequently, the mixture was dried in a forced-air drying oven at 120 °C for 12 h. After thorough grinding, the mixture underwent two-stage calcination in a muffle furnace: the first stage calcination was at 500 °C for 6 h; the second stage calcination was at 900 °C for 12 h. After cooling to room temperature, a lithium-rich manganese-based cathode material was obtained, with the chemical formula Li. 1.2 Mn 0.6 Ni 0.2 O2.
[0083] The manufacturing process of button batteries is the same as that of Comparative Example 1.
[0084] like Figure 7 As shown, the discharge specific capacity at 1C is 199.5 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 103.85 mAh / g, with a capacity retention rate of 52.1%.
[0085] Comparative Example 3
[0086] The preparation process of the button cell is the same as in Example 1, except that:
[0087] Preparation of positive electrode
[0088] The lithium-rich manganese-based cathode material prepared in Comparative Example 1 was uniformly mixed with red phosphorus at a mass ratio of 1:0.01 and placed in a quartz tube. The gas inside the tube was extracted, and the quartz tube opening was sealed by high-temperature melting to create a vacuum inside the tube. Then, it was placed in a muffle furnace and heated to 700°C at a rate of 5°C / min. After calcination at a constant temperature for 2 hours, the sample of Comparative Example 3 was obtained after cooling.
[0089] like Figure 8 As shown, the discharge specific capacity at 1C is 224.7 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 161.8 mAh / g, with a capacity retention rate of 72.0%.
[0090] Comparative Example 4
[0091] The preparation process of the button cell is the same as in Example 1, except that:
[0092] Preparation of positive electrode
[0093] The lithium-rich manganese-based cathode material prepared in Comparative Example 1 was uniformly mixed with red phosphorus at a mass ratio of 1:0.02 and placed in a quartz tube. The gas inside the tube was extracted, and the quartz tube opening was sealed by high-temperature melting to create a vacuum inside the tube. Then, it was placed in a muffle furnace and heated to 500°C at a rate of 5°C / min. After calcination at a constant temperature for 2 hours, the sample of Comparative Example 4 was obtained after cooling.
[0094] like Figure 9 As shown, the discharge specific capacity at 1C is 211.2 mAh / g, and the discharge specific capacity after 300 cycles at 1C is 154.2 mAh / g, with a capacity retention rate of 73.0%.
[0095] As can be seen from the above embodiments, the present invention provides a method for preparing a lithium-rich manganese-based cathode material modified with red phosphorus, comprising the following steps: mixing the lithium-rich manganese-based cathode material with red phosphorus at a mass ratio of 1:0.001 to 0.01, and calcining it at 300 to 600°C for 1 to 6 hours under vacuum to obtain the red phosphorus-modified lithium-rich manganese-based cathode material; the general chemical formula of the lithium-rich manganese-based cathode material is: Li 1+x Mn 1-x1 Ni 1-x2 Co 1-x3O2, x = 0.01–0.3, 2+x = x1+x2+x3, x1 = 0.3–0.6, x2 = 0.7–1, x3 = 0.8–1. This method uses inexpensive raw materials and has a simple reaction process. Red phosphorus, after sublimation at high temperature, undergoes a gas-solid interface reaction with the lithium-rich manganese-based cathode material, forming a phosphate coating on the cathode surface and simultaneously creating spinel and oxygen vacancies, achieving P doping within the cathode. This effectively improves the reversibility and structural stability of the anion redox reaction of the lithium-rich manganese-based cathode material, enhancing its initial coulombic efficiency, reversible specific capacity, and long-term cycling stability. Experimental results show that the lithium-rich manganese-based cathode material of this invention has a discharge specific capacity of 250–300 mAh / g at a current density of 0.1C and 180–250 mAh / g at a current density of 1C. The capacity retention rate after 300 cycles at a current density of 1C is 75%–95%.
[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a red phosphorus-modified lithium-rich manganese-based cathode material, comprising the following steps: A lithium-rich manganese-based cathode material was mixed with red phosphorus at a mass ratio of 1:0.001~0.
01. Under vacuum, the mixture was heated to 300~600 °C at a heating rate of 2~8 °C / min for 1~6 h. After the red phosphorus was sublimated by high temperature, it underwent a gas-solid interface reaction with the lithium-rich manganese-based cathode material, forming a phosphate coating on the cathode surface. At the same time, spinel and oxygen vacancies were formed, resulting in a red phosphorus-modified lithium-rich manganese-based cathode material. The particle size of the red phosphorus was 10~200 μm. The vacuum level under the specified vacuum condition is 0.01 MPa to 0.2 MPa; The general chemical formula of the lithium-rich manganese-based cathode material is: Li 1+x Mn 1-x1 Ni 1-x2 Co 1-x3 O2, x=0.01~0.3, 2+x=x1+x2+x3, x1=0.3~0.6, x2=0.7~1, x3=0.8~1; The lithium-rich manganese-based cathode material is prepared by the following method: Nickel, manganese, cobalt, and lithium salts were dissolved in a mixed solution of acrylic acid and deionized water. An aqueous solution of ammonium persulfate was added, and the mixture was stirred for 55–65 min. The temperature was then raised to 80 °C and held for 170–190 min to allow the reaction to proceed. The temperature was then raised to 120 °C and held for 11–13 h to allow the mixture to dry. The mixture was then ground and subjected to a two-stage calcination: the first stage calcination was carried out at 300–600 °C for 3–7 h, and the second stage calcination was carried out at 750–950 °C for 9–15 h.
2. The preparation method according to claim 1, characterized in that, The lithium-rich manganese-based cathode material is: Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.
3. A positive electrode sheet, prepared by coating a positive electrode slurry onto a positive electrode current collector; The cathode slurry includes the lithium-rich manganese-based cathode material modified with red phosphorus prepared by any one of claims 1 to 2.
4. A lithium-ion battery, characterized by, It includes a negative electrode, an electrolyte, a separator, and the positive electrode as described in claim 3.
5. The lithium-ion battery according to claim 4, characterized in that, The separator is a PP separator; the negative electrode is a lithium metal sheet; The electrolyte contains LiPF6 as the lithium salt and a 1:1 volume ratio EC / DEC mixed solvent.