A lithium-rich manganese-based positive electrode material with a layered-rock salt phase-spinel phase composite structure and a preparation method thereof

Abstract

The present invention discloses a lithium-rich manganese-based cathode material with a layered-rock salt phase-spinel-like phase composite structure and a preparation method thereof, and improves the material performance by reducing the lithium content. The cathode material is a composite structure mainly composed of a layered phase, simultaneously containing a small amount of rock salt phase and spinel-like phase, and its chemical formula is Li (1+x / 3)·y Mn 2x / 3 M 1‑ x O 2‑δ , where 0 < x < 1, 0 < y < 1, 0 ≤ δ ≤ (1 - y)(1 + x / 3) / 2, and M is a metal element selected from one or more of Ni, Co, Fe, Cu, Sn, Al, and Mn. The present invention prepares the lithium-rich manganese-based cathode material by using the coprecipitation method and high-temperature solid-phase method which are convenient for large-scale industrial production, and improves its electrochemical performance by reducing the lithium content. Compared with Li 1.2 Ni 0.2 Mn 0.6 O2, when the lithium dosage is reduced by 10%, the discharge specific capacity, cycle performance, and rate performance of the prepared Li 1.08 Ni 0.2 Mn 0.6 O 2‑δ are significantly improved. The discharge specific capacity at 0.1C is as high as 312.5 mAh g ‑1 , and the capacity retention rate reaches 93.6% after 200 cycles at a current density of 1C; at the same time, the reduction of lithium content is very beneficial to reducing the production cost of the material, and has great application potential.

Description

Technical Field

[0001] This invention relates to lithium-rich manganese-based cathode materials and their preparation methods, and particularly to a low-lithium-content lithium-rich manganese-based cathode material with a layered-rock salt phase-spinel-like phase composite structure, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density and long lifespan, have been widely used in various industries and fields, such as 3C electronic products, new energy vehicles, and energy storage systems. Their basic components include the positive electrode, negative electrode, electrolyte, and separator. With social development and improved living standards, the market demands higher energy density from lithium-ion batteries. As a crucial component, the positive electrode material significantly limits the energy density and cycle life of lithium-ion batteries. However, the actual capacity of commercially available lithium cobalt oxide, lithium iron phosphate, and NCM ternary materials is already close to their theoretical values, leaving limited room for further growth. Therefore, developing positive electrode materials with higher capacity and longer lifespan has become key to further improving the performance of lithium-ion batteries.

[0003] The lithium-rich manganese-based material xLi₂MnO₃·(1–x)LiMO₂ (where M is a metallic element, commonly one or more of Ni, Co, Fe, Cu, Sn, Al, and Mn) exhibits both Li-O-Li and TM-O-Li configurations, giving it both anionic and cation-based charge compensation mechanisms. Its theoretical specific capacity is greater than 350 mAh g⁻¹. -1 Lithium-rich materials boast a significantly higher lithium content than traditional cathode materials such as lithium cobalt oxide, lithium iron phosphate, and NCM ternary materials, making them one of the most promising next-generation cathode materials. However, lithium-rich materials still face a series of challenges in their industrialization. First, the sluggish kinetics and poor reversibility of their anion redox reactions result in low initial coulombic efficiency, rapid capacity and voltage decay, and severe voltage hysteresis. Second, oxygen generated from surface lattice oxygen during charging and discharging exacerbates side reactions with the electrolyte, while manganese ion dissolution, spinel-like phase transitions, and cation mixing also contribute to battery performance degradation. Furthermore, the higher lithium content in lithium-rich materials necessitates the consumption of more lithium resources, and the persistently high prices of raw materials such as lithium carbonate inevitably increase production costs, hindering their large-scale commercial application. Therefore, finding a simple, reliable, low-cost synthesis method for a lithium-rich manganese-based cathode material xLi2MnO3·(1–x)LiMO2 with high specific capacity and excellent cycle stability suitable for industrial production by optimizing the preparation process and controlling the crystal structure and composition is of great significance for promoting its commercial application. Summary of the Invention

[0004] The object of the present invention is to provide a simple and reliable synthesis method for improving the charge-discharge specific capacity, cycle performance and rate performance of a material and reducing its production cost by reducing the lithium content, aiming at the disadvantages of poor cycle stability of the lithium-rich manganese-based cathode material of the current lithium-ion battery and high cost caused by high lithium content, and having good industrialization prospects.

[0005] The lithium-rich manganese-based cathode material with low lithium content provided by the present invention is a composite phase mainly composed of a layered structure, and simultaneously containing a small amount of rock salt phase and spinel-like phase, with the chemical formula Li (1+x / 3)·y Mn 2x / 3 M 1-x O 2-δ , where 0 < x < 1, 0 < y < 1, 0 ≤ δ ≤ (1 - y)(1 + x / 3) / 2, M is a metal element, and commonly one or more of Ni, Co, Fe, Cu, Sn, Al and Mn.

[0006] Further preferably, 0.6 ≤ x ≤ 0.9, 0.6 ≤ y ≤ 0.95.

[0007] Preferably, the particle size of the lithium-rich manganese-based cathode material with low lithium content mainly concentrates on 100 - 200 nm.

[0008] Due to the lithium content of the lithium-rich manganese-based cathode material of the present invention being lower than the stoichiometric ratio, a certain amount of rock salt phase and spinel-like phase with less lithium content are generated in the material, which is a composite phase of layered structure, rock salt phase and spinel-like phase. Although the initial capacity of this cathode material is low, during the process of electrochemical cycling, the initially existing lithium-deficient phase will act as a phase transformation core to induce a large number of Mn ions in the main phase layered lithium-rich structure to migrate, thereby activating the redox activity of the Mn 2+ / Mn 3+ / Mn 4+ redox couple, resulting in the gradual increase of the material capacity, and finally being able to exceed the existing conventional lithium-rich manganese-based cathode materials, showing high capacity and excellent rate performance.

[0009] The present invention also provides a preparation method for the above-mentioned lithium-rich manganese-based cathode material with low lithium content, including the following steps:

[0010] (1) Dissolve manganese salt and the salt containing M metal element according to the corresponding element ratio shown in the chemical formula Li (1+x / 3)·y Mn 2x / 3M 1-x O 2-δ of the lithium-rich manganese-based cathode material in deionized water, and mix evenly to obtain a salt solution; at the same time, dissolve sodium carbonate and / or potassium carbonate and ammonia water in deionized water, and mix evenly to obtain an alkali solution, or dissolve sodium hydroxide and / or potassium hydroxide and ammonia water in deionized water, and mix evenly to obtain an alkali solution;

[0011] (2) Using a peristaltic pump, the above salt solution and alkaline solution are added dropwise to a reaction vessel containing deionized water at a certain rate, and the reaction is carried out at a set temperature and pH value, and then aged.

[0012] (3) Wash the precipitate obtained in step (2) with deionized water several times, and then dry it to obtain the precursor material;

[0013] (4) Grind and mix the precursor material and the lithium source in a certain stoichiometric ratio, and then sinter at high temperature to obtain the lithium-rich manganese-based cathode material with low lithium content.

[0014] In step (1) above, the manganese salt and the salt containing the M metal element are completely soluble in deionized water, yielding a clear solution with a total concentration of 0.5–6.0 mol / L. -1 A salt solution. The above-mentioned manganese salt and salt containing the metal element M can be selected from one or more of the sulfate, nitrate, and chloride salts of the corresponding metal element. Preferably, the total concentration of the salt is 0.5–3.0 mol / L. -1 .

[0015] In step (1) above, the alkaline solution can be an alkaline solution prepared by mixing sodium carbonate and / or potassium carbonate with ammonia, wherein the amount of sodium carbonate and / or potassium carbonate is 1 to 2 times the total amount of salt in the salt solution, and its concentration is 0.5 to 6.0 mol / L. -1 The concentration of ammonia water is 0.1–6.0 mol / L. -1 Preferably, the concentration of sodium carbonate and / or potassium carbonate is 0.5–3.0 mol / L. -1 The concentration of ammonia water is 0.1–1.0 mol / L. -1 The alkaline solution may also be an alkaline solution prepared by mixing sodium hydroxide and / or potassium hydroxide with ammonia, wherein the amount of sodium hydroxide and / or potassium hydroxide is 2 to 3 times the total amount of salt in the salt solution, and its concentration is 1.0 to 6.0 mol / L. -1 The concentration of ammonia water is 0.1–6.0 mol / L. -1 Preferably, the concentration of sodium hydroxide and / or potassium hydroxide is 2.0–4.0 mol / L. -1 The concentration of ammonia water is 0.5–2.0 mol / L. -1 .

[0016] In step (2) above, the preferred dropping rate of the salt solution is 0.5–2 mL / min. -1For the reaction that produces carbonate precursor precipitate, the pH of the solution in the reactor should be controlled at 7.0–9.0, the temperature at 40–60℃, and the stirring speed at 500–1500 rpm. After the reaction is complete, the solution should be aged for 8–16 hours. For the reaction that produces hydroxide precursor precipitate, the pH of the solution in the reactor should be controlled at 9.0–12.0, the temperature at 40–60℃, and the stirring speed at 500–1500 rpm. After the reaction is complete, the solution should be aged for 8–16 hours.

[0017] In step (3) above, preferably, the precipitate is washed at least 6 times and then placed in a vacuum environment at 80-120°C to remove residual moisture.

[0018] In step (4) above, the lithium source is preferably lithium carbonate or lithium hydroxide, and the molar ratio of the metal element in the precursor material to the lithium in the lithium source is 1:1.5 to 1:0.8, preferably 1:1.35 to 1:1.1. The sintering method is as follows: first, sinter in air at 450 to 600°C for 3 to 7 hours, then naturally cool to room temperature, grind the product, and then sinter in air at 800 to 1000°C for 8 to 24 hours, followed by natural cooling to room temperature.

[0019] Although the lithium-rich manganese-based cathode material prepared by the above method has a reduced lithium content compared to existing lithium-rich manganese-based cathode materials, its XRD pattern still exhibits typical superlattice characteristic peaks of a lithium-rich structure between 20 and 30°. Furthermore, due to the reduced lithium content, small amounts of rock salt and spinel-like phase peaks are observed, indicating that the material is a composite structure dominated by a layered structure, while also containing small amounts of rock salt and spinel-like phases. Preferably, the particle size of the low-lithium-content lithium-rich manganese-based cathode material is mainly concentrated in the range of 100–200 nm.

[0020] The beneficial effects of this invention are:

[0021] Compared with existing technologies, the lithium-rich manganese-based cathode material provided by this invention reduces the lithium content in the material during preparation, which helps to lower the preparation cost and simplifies the preparation process. Furthermore, the prepared cathode material exhibits excellent electrochemical performance, comparable to samples with no reduction in lithium content. 1.2 Ni 0.2 Mn 0.6 Compared to O2, when the lithium content is reduced by 10%, the prepared Li 1.08 Ni 0.2 Mn 0.6 O 2-δ The discharge specific capacity, cycle performance, and rate performance are all significantly improved. At 0.1C, its discharge specific capacity can reach 312.5 mAh g. -1 When the current density increases to 5C, its discharge specific capacity is still 197 mAh g. -1After 200 cycles at 1C, its capacity retention reached 93.1%, demonstrating superior electrochemical performance and great application potential. Attached Figure Description

[0022] Figure 1 The Li prepared in Example 1 of this invention 1.08 Ni 0.2 Mn 0.6 O 2-δ XRD patterns.

[0023] Figure 2 The Li prepared in Example 1 of this invention 1.08 Ni 0.2 Mn 0.6 O 2-δ SEM image.

[0024] Figure 3 The Li prepared in Example 1 of this invention 1.08 Ni 0.2 Mn 0.6 O 2-δ Rate capability and cycle performance of cathode materials. Detailed Implementation

[0025] The present invention will be further described in detail below through embodiments, but those skilled in the art should understand that the scope of the present invention is not limited thereto. Any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the spirit and scope of the technical solutions of the present invention should be covered by the protection of the present invention.

[0026] Example 1

[0027] 64.02 g MnSO4·H2O and 33.35 g NiSO4·6H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.54, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature.-1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 1.08 Ni 0.2 Mn 0.6 O 2-δ .

[0028] Li 1.08 Ni 0.2 Mn 0.6 O 2-δ XRD patterns such as Figure 1 As shown, typical superlattice characteristic peaks of a lithium-rich structure can be observed between 20 and 30°, indicating that even after reducing the lithium content by 10%, the sintered product still retains a lithium-rich structure. SEM images of the samples are shown below. Figure 2 As shown, it can be clearly seen that the particle size is mainly concentrated in the range of 100 to 200 nm.

[0029] Li 1.08 Ni 0.2 Mn 0.6 O 2-δ Testing of the electrochemical performance of materials: First, the active material Li... 1.08 Ni 0.2 Mn 0.6 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets, along with a lithium metal negative electrode, glass fiber separator, and electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%), were then assembled into CR2032 button cells in an argon-filled glove box with water and oxygen contents both less than 0.1 ppm. Finally, the cells were tested using a battery testing system within the range of 2.0–4.8V. Their rate capability and cycle performance are as follows: Figure 3 As shown, it can be clearly seen that at current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities are 312.5, 300.6, 286.2, 271.6, 240.3, and 197 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity still reaches 252.8 mAh g. -1 The capacity retention rate was 93.6%, proving that Li 1.08 Ni 0.2 Mn 0.6 O 2-δ Excellent structural stability and electrochemical performance.

[0030] Example 2

[0031] 64.02 g MnSO4·H2O and 33.35 g NiSO4·6H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.48, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 0.96 Ni 0.2 Mn 0.6 O 2-δ .

[0032] Li 0.96 Ni 0.2 Mn 0.6 O 2-δ Electrochemical performance testing: First, the active material Li 0.96 Ni 0.2 Mn 0.6 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen contents were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 279.6, 268.2, 246.3, 222.8, 185.1, and 100.7 mAh g, respectively. -1After 200 long cycles at 1C rate, its discharge specific capacity still reaches 193.6 mAh g. -1 The capacity retention rate was 87.7%.

[0033] Example 3

[0034] 64.02 g MnSO4·H2O and 33.35 g NiSO4·6H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.42, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 0.84 Ni 0.2 Mn 0.6 O 2-δ .

[0035] Li 0.84 Ni 0.2 Mn 0.6 O 2-δ Electrochemical performance testing: First, the active material Li 0.84 Ni 0.2 Mn 0.6 O 2-δConductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen content were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 263.7, 246.3, 221.8, 192.5, 154.3, and 95.6 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity still reaches 163.4 mAh g. -1 The capacity retention rate was 85.0%.

[0036] Example 4

[0037] 64.02 g MnSO4·H2O and 33.35 g NiSO4·6H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.36, transferred to an alumina crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 0.72 Ni 0.2 Mn 0.6 O 2-δ .

[0038] Li 0.72 Ni 0.2 Mn 0.6 O2-δ Electrochemical performance testing: First, the active material Li 0.72 Ni 0.2 Mn 0.6 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen contents were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 260.4, 236.5, 202.8, 165.6, 123.5, and 75.9 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity still reaches 128.3 mAh g. -1 The capacity retention rate was 78.1%.

[0039] Example 5

[0040] 67.61 g MnSO4·H2O and 26.28 g NiSO4·6H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 40.0 g of NaOH was added to 250 mL of deionized water. After magnetic stirring, 4 mol / L of the solution was obtained. -1 A brine solution was prepared, and then 6.8 g of ammonia water (mass fraction 25-28%) was added to the brine solution. The mixture was then magnetically stirred to obtain a homogeneous brine solution. The salt solution and brine solution were then added dropwise to the reaction vessel using a peristaltic pump, with the drop rate of the salt solution set at 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 11.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.554, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 1.107 Ni 0.154Mn 0.616 O 2-δ .

[0041] Li 1.107 Ni 0.154 Mn 0.616 O 2-δ Electrochemical performance testing: First, the active material Li 1.107 Ni 0.154 Mn 0.616 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen content were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 278.6, 264.3, 250.7, 234.1, 202.9, and 152.6 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity still reaches 215.6 mAh g. -1 The capacity retention rate was 92.3%.

[0042] Example 6

[0043] 57.00 g MnSO4·H2O, 21.36 g NiSO4·6H2O, and 22.83 g CoSO4·7H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.48, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 0.96 Ni 0.13 Co 0.13 Mn 0.54 O 2-δ .

[0044] Li 0.96 Ni 0.13 Co 0.13 Mn 0.54 O 2-δ Electrochemical performance testing: First, the active material Li 0.96 Ni 0.13 Co 0.13 Mn 0.54 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DEC:EC = 7:3 Vol%, 5% FEC) in a glove box filled with argon gas, where the water and oxygen content were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 253.6, 235.9, 218.5, 202.3, 171.8, and 126.6 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity is 179.2 mAh g. -1 The capacity retention rate was 89.5%.

[0045] Example 7

[0046] 52.98 g MnSO4·H2O, 21.36 g NiSO4·6H2O, and 32.83 g FeSO4·7H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L.-1 A salt solution was prepared, and then 40.0 g of NaOH was added to 250 mL of deionized water. After magnetic stirring, 4 mol / L of the solution was obtained. -1 A brine solution was prepared, and then 6.8 g of ammonia water (mass fraction 25-28%) was added to the brine solution. The mixture was then magnetically stirred to obtain a homogeneous brine solution. The salt solution and brine solution were then added dropwise to the reaction vessel using a peristaltic pump, with the drop rate of the salt solution set at 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 11.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium hydroxide were thoroughly ground at a molar ratio of 1:1.08, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 1.08 Ni 0.14 Fe 0.12 Mn 0.54 O 2-δ .

[0047] Li 1.08 Ni 0.14 Fe 0.12 Mn 0.54 O 2-δ Electrochemical performance testing: First, the active material Li 1.08 Ni 0.14 Fe 0.12 Mn 0.54 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen contents were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 302.5, 293.6, 280.2, 261.6, 231.1, and 190.3 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity is 239.3 mAh g.-1 The capacity retention rate was 91.8%.

[0048] Example 8

[0049] 64.02 g MnSO4·H2O, 29.87 g NiSO4·6H2O, and 3.15 g CuSO4·5H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 40.0 g of NaOH was added to 250 mL of deionized water. After magnetic stirring, 4 mol / L of the solution was obtained. -1 A brine solution was prepared by adding 8.5 g of ammonia water (25-28% by mass) to the brine solution and then stirring magnetically to obtain a homogeneous brine solution. The salt solution and brine solution were then added dropwise to the reaction vessel using a peristaltic pump, with the drop rate of the salt solution set at 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 11.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium hydroxide were thoroughly ground at a molar ratio of 1:1.08, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 1.08 Ni 0.18 Cu 0.02 Mn 0.6 O 2-δ .

[0050] Li 1.08 Ni 0.18 Cu 0.02 Mn 0.6 O 2-δ Electrochemical performance testing: First, the active material Li 1.08 Ni 0.18 Cu 0.02 Mn 0.6 O 2-δConductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen content were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 314.5, 303.6, 290.3, 273.6, 243.4, and 202.3 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity is 260.7 mAh g. -1 The capacity retention rate was 95.8%.

[0051] Example 9

[0052] 60.04 g MnSO4·H2O, 33.35 g NiSO4·6H2O, and 5.73 g SnCl2·2H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium hydroxide were thoroughly ground at a molar ratio of 1:1.08, transferred to a corundum crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 1.08 Ni 0.2 Mn 0.56 Sn 0.04 O 2-δ .

[0053] Li 1.08 Ni0.2 Mn 0.56 Sn 0.04 O 2-δ Electrochemical performance testing: First, the active material Li 1.08 Ni 0.2 Mn 0.56 Sn 0.04 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in a glove box filled with argon gas, where the water and oxygen content were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 313.5, 302.9, 288.3, ​​271.9, 241.1, and 200.5 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity is 257.2 mAh g. -1 The capacity retention rate was 95.1%.

[0054] Example 10

[0055] 57.00 g MnSO4·H2O, 21.36 g NiSO4·6H2O, 17.56 g CoSO4·7H2O, and 12.5 g Al2(SO4)3·18H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 41.0 g of NaOH was added to 256 mL of deionized water. After magnetic stirring, 4 mol / L of the solution was obtained. -1 A brine solution was prepared, and then 8.7 g of ammonia water (mass fraction 25-28%) was added to the brine solution. The mixture was then magnetically stirred to obtain a homogeneous brine solution. The salt solution and brine solution were then added dropwise to the reaction vessel using a peristaltic pump, with the drop rate of the salt solution set at 2 mL / min. -1The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 11.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor was then thoroughly ground with lithium hydroxide monohydrate at a molar ratio of 1:0.96, transferred to a corundum crucible, and sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 0.96 Ni 0.13 Co 0.1 Al 0.03 Mn 0.54 O 2-δ .

[0056] Li 0.96 Ni 0.13 Co 0.1 Al 0.03 Mn 0.54 O 2-δ Electrochemical performance testing: First, the active material Li 0.96 Ni 0.13 Co 0.1 Al 0.03 Mn 0.54 O 2-δ Conductive carbon black and PVDF binder were thoroughly stirred in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. The positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DEC:EC = 7:3 Vol%, 5% FEC) in a glove box filled with argon gas, where the water and oxygen content were both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 268.6, 246.3, 233.6, 218.8, 192.5, and 152.6 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity is 197.1 mAh g. -1 The capacity retention rate was 90.8%.

[0057] Comparative Example 1

[0058] 64.02 g MnSO4·H2O and 33.35 g NiSO4·6H2O were added to 250 mL of deionized water and magnetically stirred until fully dissolved, yielding 2 mol L. -1 A salt solution was prepared, and then 52.8 g of Na₂CO₃ and 3.39 g of ammonia (mass fraction 25-28%) were added to 250 mL of deionized water. The mixture was then magnetically stirred to obtain 2 mol / L of the solution. -1 An alkaline solution was added. The salt solution and alkaline solution were added dropwise into the reaction vessel using a peristaltic pump, with the salt solution being added at a rate of 2 mL / min. -1 The temperature was set at 55℃, the stirring speed at 1000 rpm, and the pH value at 8.0. After the addition was complete, the stirring speed was reduced to 500 rpm, and the mixture was aged for another 10 hours. The precipitate was then washed six times with deionized water by vacuum filtration and dried in a 100℃ oven under vacuum for 8 hours to obtain the precursor. The precursor and lithium carbonate were thoroughly ground at a molar ratio of 1:0.6, transferred to an alumina crucible, and then sintered in a muffle furnace at 5℃ for 5 minutes from room temperature. -1 The temperature was increased to 500℃ at a constant rate, held for 5 hours, then increased to 900℃ at the same rate, held for 12 hours, and then allowed to cool naturally to room temperature to obtain Li. 1.2 Ni 0.2 Mn 0.6 O2.

[0059] Li 1.2 Ni 0.2 Mn 0.6 Electrochemical performance testing of O2: First, the active material Li 1.2 Ni 0.2 Mn 0.6 O2, conductive carbon black, and PVDF binder were mixed thoroughly in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to prepare a slurry. This slurry was then uniformly coated onto aluminum foil and dried in a 100°C forced-air drying oven for 2 hours, followed by drying under vacuum at 110°C for 10 hours before being cut into positive electrode sheets. These positive electrode sheets were then assembled with a lithium metal negative electrode, a glass fiber separator, and an electrolyte (1M LiPF6 / DMC:EC = 7:3 Vol%) in an argon-filled glove box with water and oxygen contents both less than 0.1 ppm. Finally, the batteries were tested using a battery testing system within the range of 2.0–4.8V. At current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C, the discharge specific capacities were 251.6, 228.7, 200.3, 177.5, 156.8, and 126.1 mAh g, respectively. -1 After 200 long cycles at 1C rate, its discharge specific capacity is 163.4 mAh g. -1 The capacity retention rate was 92.3%.

Claims

1. A lithium-ion battery cathode material, characterized in that, It is a lithium-rich manganese-based cathode material with a low lithium content, having a composite structure mainly composed of a layered structure and containing a small amount of rock salt phase and spinel-like phase, and the chemical formula is Li (1+x / 3)·y Mn 2x / 3 M 1- x O 2-δ , where 0 < x < 1, 0 < y < 1, 0 ≤ δ ≤ (1 - y)(1 + x / 3) / 2; M is a metal element selected from one or more of Ni, Co, Fe, Cu, Sn, Al, and Mn.

2. The lithium-ion battery cathode material as described in claim 1, characterized in that, 0.6≤x≤0.9, 0.6≤y≤0.

95.

3. The lithium-ion battery cathode material as described in claim 1, characterized in that, The particle size of the cathode material is mainly concentrated in the range of 100 to 200 nm.

4. A method for preparing the lithium-ion battery cathode material according to any one of claims 1 to 3, comprising the following steps: 1) Combine manganese salts and salts containing the metal element M according to the chemical formula Li (1+x / 3)·y Mn 2x / 3 M 1-x O 2-δ The corresponding elements shown in the figure are dissolved in deionized water and mixed evenly to obtain a salt solution; at the same time, sodium carbonate and / or potassium carbonate and ammonia are dissolved in deionized water and mixed evenly to obtain an alkaline solution, or sodium hydroxide and / or potassium hydroxide and ammonia are dissolved in deionized water and mixed evenly to obtain an alkaline solution. 2) Using a peristaltic pump, the salt solution and alkali solution prepared in step 1) are added dropwise to the reaction vessel containing deionized water at a certain rate. The reaction is carried out at the set temperature and pH value, and then aged. 3) Wash the precipitate obtained in step 2) with deionized water several times, and then dry it to obtain the precursor material; 4) Grind and mix the precursor material and lithium source in stoichiometric ratio until uniform, and then sinter at high temperature to obtain lithium-rich manganese-based cathode material with low lithium content.

5. The preparation method according to claim 4, characterized in that, The manganese salt and the salt containing metal element M described in step 1) are completely soluble in deionized water, yielding a clear solution with a total concentration of 0.5–6 mol / L. -1 In a salt solution; or in an alkaline solution prepared from sodium carbonate and / or potassium carbonate and ammonia, the amount of sodium carbonate and / or potassium carbonate is 1 to 2 times the total amount of salt in the salt solution, and its concentration is 0.5 to 6.0 mol / L. -1 The concentration of ammonia water is 0.1–6.0 mol / L. -1 In the alkaline solution prepared with sodium hydroxide and / or potassium hydroxide and ammonia, the amount of sodium hydroxide and / or potassium hydroxide is 2 to 3 times the total amount of salt in the salt solution, and its concentration is 1.0 to 6.0 mol / L. -1 The concentration of ammonia water is 0.1–6.0 mol / L. -1 .

6. The preparation method according to claim 4, characterized in that, The manganese salt and salt containing the metal element M mentioned in step 1) are selected from one or more of the sulfate, nitrate and chloride salts of the corresponding metal element.

7. The preparation method according to claim 4, characterized in that, In step 2), the salt solution is added at a rate of 0.5–2 mL / min. -1 For the reaction that generates carbonate precursor precipitate, the pH of the solution in the reactor is controlled at 7.0–9.0, the temperature is set at 40–60℃, and the reaction is allowed to proceed until the solution is fully reacted and then aged for 8–16 hours. For the reaction that generates hydroxide precursor precipitate, the pH of the solution in the reactor is controlled at 9.0–12.0, the temperature is set at 40–60℃, and the reaction is allowed to proceed until the solution is fully reacted and then aged for 8–16 hours.

8. The preparation method according to claim 4, characterized in that, The lithium source mentioned in step 4) is lithium carbonate or lithium hydroxide, and the molar ratio of the metal element in the precursor material to the lithium in the lithium source is 1:1.5 to 1:0.

8.

9. The preparation method according to claim 4, characterized in that, In step 4), the sintering method is to first sinter in air at 450-600℃ for 3-7 hours, then naturally cool to room temperature and grind the product, and then sinter in air at 800-1000℃ for 8-24 hours, and then naturally cool to room temperature.

10. A lithium-ion battery, characterized in that, Its positive electrode uses the lithium-ion battery positive electrode material as described in any one of claims 1 to 3.

Images