High-performance lithium-rich manganese-based positive electrode material and controllable oxygen partial pressure preparation method thereof

Abstract

The invention discloses a method for accurately regulating and controlling oxygen vacancy concentration in a lithium-rich layered oxide positive electrode material and application of the method. According to the method, a controllable oxygen partial pressure environment is established by utilizing a CO / CO2 mixed gas pair on the basis of a pyrometallurgy principle, and the proportion of Mn < 4 + > / Mn < 3 + > in the material and the corresponding oxygen vacancy concentration are accurately regulated and controlled through a thermodynamic equilibrium process. According to the method, the oxygen vacancy concentration can be continuously and accurately controlled in an extremely wide oxygen partial pressure range (10 <-0.7 > to 10 <-10 > atm), and foreign impurities are not introduced. Along with the increase of oxygen vacancy concentration, lattice expansion and superstructure enhancement of the material occur, so that the activity and reversibility of the anion oxidation-reduction reaction are remarkably optimized. Experiments show that the lithium-rich positive electrode material treated by the method under the optimized condition shows higher specific capacity and improved cycle stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemical energy storage materials and devices, and particularly relates to a modification method of lithium ion battery lithium-rich manganese-based positive electrode material. More particularly, it relates to a method for precisely regulating the oxygen vacancy concentration in lithium-rich layered oxides based on controllable oxygen partial pressure heat treatment technology, as well as high-performance positive electrode materials and lithium ion batteries prepared therefrom. BACKGROUND

[0002] As the mainstream electrochemical energy storage system, rechargeable lithium ion batteries have been widely used in consumer electronics, electric vehicles and large-scale energy storage. However, the overall energy density is largely limited by the specific capacity of the positive electrode material. At present, the actual specific capacity of the commercial mainstream positive electrode material, such as lithium cobaltate, lithium iron phosphate and ternary material, is usually lower than 200 mA h g -1 , which is much lower than the theoretical specific capacity of graphite negative electrode (about 370 mA h g -1 ). This mismatch between the capacity of the positive and negative electrodes seriously restricts the further improvement of the energy density of lithium ion batteries.

[0003] Among the many candidate materials, lithium-rich layered oxides are considered one of the most promising positive electrode materials for the next generation of high-energy-density lithium ion batteries, as they can provide a high specific capacity of more than 250 mA h g -1 . This ultra-high capacity is due to the unique charge compensation mechanism, in which transition metal cations and lattice oxygen anions participate in the redox reaction together. However, the activation of anion redox reaction brings a series of severe challenges: first, the process is often accompanied by irreversible oxygen evolution and irreversible structural evolution, resulting in continuous capacity decay and significant decrease in average working voltage during the cycle; second, the anion redox reaction is usually slow in kinetics, which is due to the large charge transfer energy gap from ligand to metal. Therefore, pure phase Li2MnO3 or lithium-rich materials with low nickel / cobalt content usually exhibit limited electrochemical activity and require a long electrochemical activation process.

[0004] In order to overcome these difficulties, the academic community has proposed the strategy of introducing oxygen vacancies into the material. Theoretical studies have shown that oxygen vacancies can pre-adjust the local oxygen coordination environment, effectively inhibit the irreversible oxygen loss during the cycle, and may improve the redox kinetics of oxygen ions, thus providing a feasible way to stabilize the cycle performance and improve the oxygen activity.

[0005] Currently, there are various methods explored for introducing oxygen vacancies in lithium-rich materials. These methods can be broadly divided into two categories: 1) thermal treatment method, such as high-temperature quenching or sintering in an oxygen-deficient atmosphere; 2) chemical post-treatment method, using various reducing agents such as NH4HCO3, urea, red phosphorus, ferrous oxalate, citric acid, oleic acid, dimethyl oxalate, etc. The essence of these methods is related to the reduction of transition metal ions in lithium-rich materials, especially the reduction of Mn 4+ to Mn 3+ However, the existing technology has obvious limitations: first, it is difficult to accurately and controllably introduce the concentration of oxygen vacancies in the material; second, many methods inevitably change the bulk structure of the material or introduce other impurity components while introducing oxygen vacancies, and these concurrent changes make it difficult to separate the effects of oxygen vacancies themselves from other interfering factors, thereby hindering the in-depth understanding and accurate evaluation of the mechanism of oxygen vacancies.

[0006] Therefore, there is an urgent need in the art to develop a new method that can accurately regulate the concentration of oxygen vacancies in lithium-rich materials within a wide range. Such a method is crucial for systematically studying the intrinsic structure-activity relationship between oxygen vacancy concentration and electrochemical performance, and for developing lithium-rich manganese-based positive electrode materials with high capacity and high stability. SUMMARY

[0007] The purpose of the present application is to overcome the problems of capacity and voltage decay caused by the irreversible anion redox reaction and slow kinetics of existing lithium-rich layered oxide positive electrode materials, as well as the defects of existing oxygen vacancy introduction techniques, such as inaccurate control and introduction of interference variables.

[0008] To achieve the above-mentioned purpose, the present application provides a lithium-rich layered oxide modification method based on controllable oxygen partial pressure heat treatment. The core of the present application is to innovatively apply the gas balance principle in pyrometallurgy to battery material preparation, by using a specific CO / CO2 mixed gas pair to accurately regulate the oxygen partial pressure of the heat treatment environment within a very wide range (e.g. 10 -0.7 to 10 -10 atm). This process enables the material system to accurately adjust the ratio of Mn 4+ / Mn 3+ , thereby achieving continuous and controllable introduction of oxygen vacancy concentration within a wide range.

[0009] The lithium-rich layered oxide modification method based on controllable oxygen partial pressure heat treatment of the present application comprises the following steps:

[0010] S1. Providing a precursor mixture containing a lithium source, a manganese source and a nickel source;

[0011] S2. The precursor mixture is heat-treated under a controllable oxygen partial pressure atmosphere, wherein the controllable oxygen partial pressure atmosphere is provided by a mixed gas containing CO and CO2, and the oxygen partial pressure of the controllable oxygen partial pressure atmosphere is precisely controlled at 10 by adjusting the partial pressure ratio of CO to CO2. -0.7 atm to 10 -10.0 Within the range of atm;

[0012] S3. After the heat treatment, a lithium-rich layered oxide cathode material with a preset oxygen vacancy concentration is obtained.

[0013] Preferably, in step S1, the precursor mixture is prepared by a sol-gel method comprising the following steps:

[0014] S1.1. Dissolve the lithium source, manganese source and nickel source in a solvent to form a mixed salt solution, wherein the amount of lithium source used is 3-5 wt.% in excess of the theoretical stoichiometry to compensate for lithium loss during the high-temperature calcination process;

[0015] S1.2. An organic acid is added to the mixed salt solution as a complexing agent, and after gelation and drying, a dry gel is obtained;

[0016] S1.3. The dry gel is pre-sintered in air to obtain the precursor mixture.

[0017] As a further preferred option, the molar ratio of Mn, Ni, and Li in the precursor mixture is: Li:Mn:Ni = (1.20-1.35) : (0.60-0.66) : (0-0.20).

[0018] As a further preferred option, the organic acid mentioned in step S1.2 is acrylic acid, and its addition amount is calculated based on a 1:1 molar ratio of the total metal cations' valence. In actual operation, acrylic acid is added to the mixed salt solution obtained in step S1.1 according to a stoichiometric ratio of the total metal cations' valence to the acrylic acid's molar ratio of 1:1, and stirred until homogeneous. Subsequently, the mixed solution is continuously stirred and dried at 60-80°C for 10-24 hours until the water is completely evaporated, resulting in a dry gel.

[0019] As a further preferred option, the pre-sintering in step S1.3 is a two-step heat treatment: first, it is held at 300-400℃ for 2-4 hours, then ground, and finally held at 400-500℃ for 2-4 hours.

[0020] The present invention subjectes the dry gel obtained in step S1.2 to a two-step heat treatment to completely decompose acetate and acrylic acid: First, it is heated to 300-400°C at a heating rate of 1-3°C / min in air atmosphere and held for 2-4 hours; after natural cooling, it is ground and then heated again to 400-500°C at a heating rate of 3-7°C / min and held for 2-4 hours to obtain lithium-rich layered oxide precursor powder.

[0021] Preferably, the heat treatment temperature in step S2 is 850-950℃, and the holding time is 6-15 hours.

[0022] Preferably, the mixed gas also includes an inert gas as a carrier gas; preferably, the inert gas is argon.

[0023] In practical applications, the oxygen partial pressure is controlled at 10 by using a mixture of 1~10% CO + 90~99% Ar and CO2. -10.0 ~10 -8.0 atm.

[0024] The partial pressure of oxygen is controlled by varying the volume percentage of different gases (for example, 10). -10.0 10 -8.0 Or 10 -9.0 Using different gas volume ratios will correspond to different calcination temperatures (800-1000℃) and gas flow rates (Ar / CO2: 1-20ml).

[0025] To accurately construct and calibrate the oxygen partial pressure environment, a gas mixture with different components and proportions is introduced into the furnace before S2 heat treatment to create a precise oxygen partial pressure environment; the controlled range of the oxygen partial pressure covers 10... -0.7 Up to 10 - 10.0 Atm, specifically: when the oxygen partial pressure is 10... -0.7 At M, this is achieved by introducing compressed air; the oxygen partial pressure is 10. -5.6 At a time of 10, it is achieved by introducing pure CO2 gas; the oxygen partial pressure is 10. -8.0 atm and 10 -10.0 Atm is achieved by precisely controlling the ratio of the CO / CO2 / Ar mixed gas; preferably, a mixture of 1% CO + 99% Ar and CO2 is used to construct 10 -8.0 In an ATM environment, a mixture of 5% CO and 95% Ar and CO2 was used to construct 10 -10.0 ATM environment. The gas percentage is by volume.

[0026] In step S2, a solid electrolyte oxygen probe is used to monitor and control the actual oxygen partial pressure of the controllable oxygen partial pressure atmosphere in real time, so as to ensure that the fluctuation range of the logarithmic value of the oxygen partial pressure is within ±0.1.

[0027] After heat treatment, the theoretical average valence state of Mn element is +3.7 to +3.85. After optimization, it is +3.75 to +3.85, which includes +3.75 to +3.78, +3.78 to +3.80, +3.80 to +3.85, etc.

[0028] Preferably, in step S2, a solid electrolyte oxygen probe is used to monitor and control the actual oxygen partial pressure of the controllable oxygen partial pressure atmosphere in real time. The required oxygen partial pressure is calculated using Factsage 8.3.

[0029] In this invention, under a precisely controlled oxygen partial pressure environment, the precursor powder is heated to 850-950°C (including 890-920°C, and of course 895-905°C) at a heating rate of 3-8°C / min, and held at this temperature for 6-15 hours, followed by furnace cooling to room temperature. During this thermodynamic equilibrium process, the Mn in the material... 4+ / Mn 3+ The ratio is precisely controlled according to the oxygen partial pressure, thereby introducing a preset concentration of oxygen vacancies into the final product, resulting in a modified lithium-rich layered oxide cathode material with a specific oxygen vacancy concentration.

[0030] The lithium-rich layered oxide cathode material prepared by this invention is used as the cathode of lithium batteries.

[0031] The lithium battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode contains a lithium-rich layered oxide positive electrode material.

[0032] Beneficial effects of the present invention

[0033] 1. Achieved high-precision and purified introduction of oxygen vacancies: This invention is the first to apply the gas balance principle of pyrometallurgy to the preparation of lithium-rich cathode materials. By precisely controlling the ratio of CO / CO2 mixed gas, it is possible to achieve high-precision and purified introduction of oxygen vacancies over an extremely wide range (10). -0.7 Up to 10 -10.0 The oxygen partial pressure of the heat treatment environment can be continuously and adjustable using atm. This method utilizes thermodynamic equilibrium and directly adjusts the oxygen partial pressure by adjusting Mn. 4+ / Mn 3+ The ratio is used to accurately introduce oxygen vacancies. The entire process does not introduce any foreign chemical reagents or impurities, effectively avoiding the interference caused by changes in composition and structure in traditional methods. This provides a pure and reliable model material and research foundation for studying the intrinsic role and structure-activity relationship of oxygen vacancies.

[0034] 2. Significantly Improved Electrochemical Performance of Lithium-Rich Cathode Materials: Through the precise control described above, this invention enables "idealized" oxygen vacancy modification of the material, thereby effectively activating and stabilizing the anion redox reaction. Experiments demonstrate that the lithium-rich layered oxide cathode material treated with this optimized process exhibits significantly improved specific capacity, first-cycle efficiency, and cycle stability. This method fundamentally solves the problem of voltage and capacity decay caused by irreversible oxygen loss, providing a clear and efficient process route for preparing next-generation lithium-ion battery cathode materials with both high energy density and long lifespan. Attached Figure Description

[0035] Figure 1 This is the Mn-O2 binary phase diagram of Example 2.

[0036] Figure 2 Li in Example 2 1.29 Mn 0.64 Ni 0.07 The change of oxygen vacancy concentration in O2 materials with calcination time.

[0037] Figure 3 The Li prepared in Example 2 1.29 Mn 0.64 Ni 0.07 XPS plot of O2 material.

[0038] Figure 4 The Li prepared in Example 3 1.29 Mn 0.64 Ni 0.07 XRD pattern of O2 material.

[0039] Figure 5 The Li prepared in Example 4 1.29 Mn 0.64 Ni 0.07 Electrochemical performance (charge-discharge cycle) of O2 materials.

[0040] Figure 6 The Li prepared in Example 4 1.29 Mn 0.64 Ni 0.07 Electrochemical performance (charge-discharge rate) of O2 materials.

[0041] Figure 7 This is a graph showing the electrochemical performance (charge-discharge cycle) of the lithium-rich manganese-based cathode material (Mn:Ni=5:1, molar ratio) prepared in Example 5.

[0042] Figure 8 This is a graph showing the electrochemical performance (charge-discharge cycle) of the lithium-rich manganese-based cathode material (Mn:Ni=3:1, molar ratio) prepared in Example 5.

[0043] Figure 9 This is a graph showing the electrochemical performance (charge-discharge cycle) of the lithium-rich manganese-based cathode material (Mn:Ni=19:1, molar ratio) prepared in Example 5.

[0044] Figure 10 This is a graph showing the electrochemical performance (charge-discharge cycle) of the lithium-rich manganese-based cathode material (pure Li2MnO3, Mn:Ni=1:0, molar ratio) prepared in Example 5. Detailed Implementation

[0045] After detailing the core principles and methods of this invention, the following specific embodiments and comparative examples are provided to fully demonstrate its technical effects and universality. These embodiments systematically examine different oxygen partial pressure conditions (from 10...). -0.7 atm to 10 -10.0 The effects of atm on the crystal structure, oxygen vacancy concentration, and electrochemical performance of a series of lithium-rich layered oxide materials (including those with different Mn / Ni ratios) were demonstrated through comparison. The significant advantages and wide applicability of the thermodynamic equilibrium-based precise oxygen partial pressure control technology in improving material performance were clearly demonstrated.

[0046] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0047] Example 1

[0048] This example provides a method for preparing lithium-rich manganese-based cathode materials, specifically:

[0049] S1: The precursor was prepared using the sol-gel method.

[0050] S2: Dissolve manganese acetate tetrahydrate (C4H6O4Mn·4H2O), nickel acetate tetrahydrate (C4H6O4Ni·4H2O), and lithium acetate dihydrate (C2H3O2Li·2H2O, with an excess of 3 wt.% of lithium salt to compensate for lithium loss during high-temperature calcination) in deionized water to prepare a solution with a total cation concentration of 1 mol / L.

[0051] S3: Subsequently, acrylic acid is added to the solution as a complexing agent, characterized in that the amount of acrylic acid added is calculated stoichiometrically, and the ratio of its molar number to the total valence of all metal cations in the solution is 1:1.

[0052] S4: As a preferred embodiment of the present invention, the total valence of the total metal cations is calculated by: statistically analyzing the Li in the solution... + Mn 4+ Ni 2+The molar number of each ion is summed according to their ionic valence states, i.e.: total valence (mol) = n(Li + ) × 1 + n(Mn 4+ ) × 4 + n(Ni 2+ ) × 2.

[0053] S5: Slowly and continuously dry the mixed solution at 70°C for 20 hours to evaporate all the water.

[0054] S6: Subsequently, the sample was subjected to a two-step heat treatment to decompose acetate and acrylic acid: first, it was heated to 350°C at a heating rate of 2°C / min and held for 3 hours; after cooling and grinding, it was heated to 450°C at a rate of 5°C / min and held for 3 hours.

[0055] S7: Based on the steps described in S2, five series of cobalt-free lithium-rich samples were prepared, including manganese-nickel-based samples (manganese-nickel molar ratios of 3:1, 5:1, 9:1 and 19:1, respectively) and one nickel-free sample.

[0056] Example 2:

[0057] This example provides a method for preparing the precursor in Example 1 by precise oxygen partial pressure heat treatment, specifically as follows:

[0058] S1: Based on the Mn-O2 binary phase diagram, the precursor is placed in a high-temperature tube furnace ( Figure 1 ).

[0059] S2: The manganese-nickel molar ratio of the precursor described in S1 is approximately 9:1 (Li 1.29 Mn 0.64 Ni 0.07 O2).

[0060] S3: Before heat treatment, measure a constant temperature zone approximately 2-3 cm long inside the furnace. The temperature in this zone is relatively stable, with fluctuations of less than 2°C. Place a working thermocouple with a recrystallized alumina protective sleeve inside the constant temperature zone of the furnace to monitor the actual calcination temperature of the sample in situ.

[0061] S4: The atmosphere used to regulate the oxygen partial pressure is a mixture of 1% CO + 99% Ar and CO2, which stabilizes the oxygen partial pressure in the furnace at 10. -8.0 atm.

[0062] S5: The calcination temperature used is 900℃, and the sintering procedure is as follows: heat up to 900℃ at 5℃ / min and hold for 12 hours to ensure thermodynamic equilibrium is reached, and then cool with the furnace.

[0063] Example 3:

[0064] This embodiment details various precise and controllable oxygen partial pressure heat treatment environments constructed to achieve precise control of oxygen vacancies as described in this invention.

[0065] S1: The control range of the oxygen partial pressure (PO2) covers from 10 -0.7 atm to 10 -10.0 ATM is specifically achieved by controlling the type and flow rate of the working gas introduced into the high-temperature tubular furnace.

[0066] S2: One of the cases described in S1, where PO2 = 10 -0.7 The conditions for ATM are established by using compressed air as the working gas and controlling its flow rate at a heat treatment temperature of 900°C to create and maintain the oxygen partial pressure environment. This calcination temperature can be extended to 500-1200°C.

[0067] S3: One of the cases described in S1, where PO2 = 10 -5.6 The conditions for setting up an ATM are as follows: using pure carbon dioxide gas as the working gas, and controlling its flow rate at a heat treatment temperature of 900°C, an oxygen partial pressure environment is established and maintained.

[0068] S4: One of the conditions described in S1, low oxygen partial pressure conditions (PO2 = 10). -8.0 atm and PO2 = 10 -10.0 Construction of atm: Based on the gas-phase equilibrium relationship between carbon monoxide and carbon dioxide.

[0069] S5: PO2 = 10 -8.0 The ATM environment is achieved by introducing a mixed atmosphere consisting of 1% carbon monoxide, 99% argon, and carbon dioxide into the furnace.

[0070] S6: PO2 = 10 -10.0 The environment of the atm is achieved by introducing a mixed atmosphere consisting of a mixture of 5% carbon monoxide and 95% argon gas and carbon dioxide gas into the furnace. The corresponding flow rates in S1-6 are shown in Table 1.

[0071] S7: The oxygen vacancy (OVs) concentration (molar ratio of oxygen vacancy to stoichiometric oxygen) in the samples after heat treatment for 0-30 hours and calcination for 12 hours and 30 hours was very close to 3.8 molar percentage, which proves that the formation of oxygen vacancies reached equilibrium after 12 hours. Figure 2 ).

[0072] S8: XPS images of the lithium-rich manganese-based cathode materials described in S2-S6 ( Figure 3As the oxygen partial pressure decreases, the peak representing the binding energy of vacant oxygen in XPS (529 eV) shifts more and more towards a position with a lower binding energy, indicating that there are more and more oxygen vacancies.

[0073] S9: XRD patterns of lithium-rich manganese-based cathode materials described in S2-S6 ( Figure 4 The X-ray diffraction patterns of all samples showed a layered structure, indicating that the main crystal structure framework of the material remained stable even under different oxygen partial pressure treatment environments.

[0074] S10: The lithium-rich manganese-based cathode material described in S2-S6 (Li 1.29 Mn 0.64 Ni 0.07 The oxygen vacancy content of O2 is shown in Table 2.

[0075] Example 4:

[0076] This embodiment details the Li prepared to achieve the present invention. 1.29 Mn 0.64 Ni 0.07 O2 materials provide a method for testing electrochemical performance.

[0077] Battery assembly and electrochemical performance testing were performed using CR2032 coin cells to test the obtained Li... 1.29 Mn 0.64 Ni 0.07 The electrochemical performance of O2 materials was tested using the following steps:

[0078] S1: Preparation of the working electrode: Accurately weigh 80 mg of active material, 10 mg of conductive carbon black, and 10 mg of polyvinylidene fluoride (PVDF), and grind and mix them thoroughly in a mortar; then add 400 μL of N-methyl-2-pyrrolidone (NMP) solvent, and continue grinding until the PVDF is completely dissolved to form a uniform slurry. Coat the slurry onto an aluminum foil current collector, control the thickness with a scraper, and place it in a vacuum drying oven at 120℃ for 20 hours. Cut the dried electrode into a circular piece with a diameter of 12 mm. The surface loading of the active material in the resulting electrode piece is approximately 2 mg / cm².

[0079] S2: Battery assembly: In an argon-filled glove box, the working electrode is used as the positive electrode, the lithium metal sheet is used as the negative electrode, the Celgard 2300 polypropylene membrane is used as the separator, and a 1 mol / L LiPF6 electrolyte is used to assemble a CR2032 button battery; wherein, the electrolyte solvent is a mixed solvent composed of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1.

[0080] S3: Electrochemical Performance Testing: The assembled battery was subjected to constant current charge-discharge testing at room temperature using a multi-channel battery testing system (LandCT2001A).

[0081] S4: Charge and discharge test conditions: current density is 0.1C, voltage range is 2.0-4.8 V, and the number of tests is 300.

[0082] S5: Cyclic performance test, charge and discharge test at a current density of 0.1C ( Figure 5 The oxygen partial pressures corresponding to the test samples were PO2 = 10. -10.0 atm, PO2 = 10 -8.0 atm, PO2 = 10 -5.6 atm, PO2 = 10 -0.7 atm. After 300 cycles at a current density of 0.1C and a voltage range of 2.0-4.8 V, Li 1.29 Mn 0.64 Ni 0.07 O material (PO2 = 10) -10.0 The discharge specific capacity (atm) is 155.15 mA hg. -1 Li 1.29 Mn 0.64 Ni 0.07 O material (PO2 = 10) -8.0 The discharge specific capacity (atm) is 98.5 mA hg. -1 Li 1.29 Mn 0.64 Ni 0.07 O material (PO2 = 10) -5.6 The discharge specific capacity (atm) is 81.9 mA hg -1 Li 1.29 Mn 0.64 Ni 0.07 O material (PO2 = 10) -0.7 The discharge specific capacity (atm) is 116.9 mA hg. -1 .

[0083] S5: Rate performance test. Within the same voltage range, charge and discharge tests were conducted sequentially at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 0.1C to evaluate the material's capacity retention capability at different currents. The oxygen partial pressures corresponding to the test samples were PO2 = 10. -0.7 atm, PO2 = 10 -8.0 atm ( Figure 6 Test results show that at low oxygen partial pressure (PO2 = 10), -8.0Materials treated under conditions of atm (atm) exhibited significantly higher discharge specific capacities at all rates than samples treated under conventional air atmosphere. Particularly at high rates (5C), the capacity still reached 75 mA hg. -1 Furthermore, after recovering to 0.1C, the capacity further increased to 220 mA hg. -1 The material exhibits excellent structural stability and rate performance. In contrast, the material treated with air atmosphere shows significant capacity decay and poor rate performance.

[0084] Example 5:

[0085] This embodiment aims to illustrate the various cathode materials prepared according to the present invention—including those with a manganese-nickel molar ratio of approximately 3:1 (Li 1.29 Mn 0.53 Ni 0.18 O2), 5:1 (Li 1.29 Mn 0.59 Ni 0.12 O2) and 19:1 (Li 1.29 Mn 0.68 Ni 0.04 The specific method for electrochemical performance testing of manganese-nickel based samples (O2) and a nickel-free sample (Li2MnO3, Mn : Ni = 1 : 0, molar ratio).

[0086] The performance testing steps are the same as in Example 4, except that in this example only the charge-discharge cycle performance of the material is evaluated, and the number of cycles is limited to less than 50.

[0087] Figures 7 to 10 Samples with manganese-nickel molar ratios of 3:1, 5:1, and 19:1, as well as a nickel-free sample, are shown. These samples were processed using PO2 = 10... -0.7 atm and PO2 = 10 -8.0 Comparison of electrochemical performance data after treatment under two oxygen partial pressure conditions (ATM). When lithium-rich manganese-based cathode material (Mn:Ni = 5:1) is treated under PO2 = 10... -0.7 atm and PO2 = 10 -8.0 After ATM processing ( Figure 7 ), PO2 = 10 -0.7 After 50 cycles, the discharge specific capacity of the material corresponding to atm is 195.6 mA hg. -1 PO2 = 10 -8.0 After 50 cycles, the discharge specific capacity of the material corresponding to atm is 220.17 mA hg. -1 When lithium-rich manganese-based cathode materials (Mn:Ni = 3:1) are used in PO₂ = 10 -0.7atm and PO2 = 10 -8.0 After ATM processing ( Figure 8 ), PO2 = 10 -0.7 After 15 cycles, the discharge specific capacity of the material corresponding to atm is 213.3 mA hg. -1 PO2 = 10 -8.0 After 15 cycles, the discharge specific capacity of the material corresponding to atm is 216.6 mA hg. -1 When lithium-rich manganese-based cathode materials (Mn:Ni = 3:1) are used in PO2 = 10 -0.7 atm and PO2 = 10 -8.0 After ATM processing ( Figure 8 ), PO2 = 10 -0.7 After 15 cycles, the discharge specific capacity of the material corresponding to atm is 213.3 mA hg. -1 PO2 = 10 -8.0 After 15 cycles, the discharge specific capacity of the material corresponding to atm is 216.6 mA hg. -1 When lithium-rich manganese-based cathode materials (Mn:Ni = 19:1) are used in PO2 = 10 -0.7 atm and PO2 = 10 -8.0 After ATM processing ( Figure 9 ), PO2 = 10 -0.7 After 50 cycles, the discharge specific capacity of the material corresponding to atm is 33.23 mA hg. -1 PO2 = 10 -8.0 After 50 cycles, the discharge specific capacity of the material corresponding to atm is 82.27 mA hg. -1 Pure Li₂MnO₃ in PO₂ = 10 -0.7 atm and PO2 = 10 -8.0 After ATM processing ( Figure 10 ), PO2 = 10 -0.7 After 40 cycles, the discharge specific capacity of the material corresponding to atm is 21.87 mA hg. -1 PO2 = 10 -8.0 After 40 cycles, the discharge specific capacity of the material corresponding to atm is 39.45 mA hg. -1 .

[0088]

[0089]

[0090] The above description is only a preferred embodiment of the present invention and does not limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a lithium-rich layered oxide cathode material, characterized in that, Includes the following steps: S1. Provides a precursor mixture comprising lithium, manganese, and nickel sources; S2. The precursor mixture is heat-treated under a controllable oxygen partial pressure atmosphere, wherein the controllable oxygen partial pressure atmosphere is provided by a mixed gas containing CO and CO2, and the oxygen partial pressure of the controllable oxygen partial pressure atmosphere is precisely controlled at 10 by adjusting the partial pressure ratio of CO to CO2. -0.7 atm to 10 -10.0 Within the range of atm; S3. After the heat treatment, a lithium-rich layered oxide cathode material with a preset oxygen vacancy concentration is obtained.

2. The preparation method according to claim 1, characterized in that: In step S1, the precursor mixture is prepared by a sol-gel method comprising the following steps: S1.

1. Dissolve the lithium source, manganese source, and nickel source in a solvent to form a mixed salt solution, wherein the amount of lithium source used is 3-5 wt.% in excess of the theoretical stoichiometry. S1.

2. An organic acid is added to the mixed salt solution as a complexing agent, and after gelation and drying, a dry gel is obtained; S1.

3. The dry gel is pre-sintered in air to obtain the precursor mixture.

3. The preparation method according to claim 2, characterized in that: The organic acid mentioned in step S1.2 is acrylic acid, and its addition amount is calculated based on the total valence of metal cations at a molar ratio of 1:

1.

4. The preparation method according to claim 2, characterized in that: The pre-sintering described in step S1.3 is a two-step heat treatment: first, it is held at 300-400℃ for 2-4 hours, then ground, and finally held at 400-500℃ for 2-4 hours.

5. The preparation method according to claim 1, characterized in that: The heat treatment temperature in step S2 is 800-1000℃, and the holding time is 6-15 hours; The mixed gas also contains an inert gas as a carrier gas; preferably, the inert gas is argon.

6. The preparation method according to claim 1 or 5, characterized in that: By using a mixture of 1~10% CO + 90~99% Ar and CO2, the oxygen partial pressure is controlled at 10. -10.0 ~10 -8.0 atm.

7. The preparation method according to claim 6, characterized in that: The oxygen partial pressure is controlled by different gas volume ratios, and different combinations of gas volume ratios will correspond to different calcination temperatures and gas flow rates. In step S2, a solid electrolyte oxygen probe is used to monitor and control the actual oxygen partial pressure of the controllable oxygen partial pressure atmosphere in real time, so as to ensure that the fluctuation range of the logarithmic value of the oxygen partial pressure is within ±0.

1.

8. The preparation method according to claim 1, characterized in that: After heat treatment, the theoretical average valence state of Mn is +3.7 to +3.

85.

9. A lithium-rich layered oxide cathode material, characterized in that, The positive electrode material is prepared by any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that, It comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises the lithium-rich layered oxide positive electrode material as described in claim 9.

Images