Modified lithium-rich manganese-based positive electrode active material, method of preparation, applications and lithium-ion battery

Abstract

This invention relates to the field of battery materials, specifically to modified lithium-rich manganese-based cathode active materials, their preparation methods, applications, and lithium-ion batteries. The preparation method for the modified lithium-rich manganese-based cathode active material involves placing a lithium-rich manganese-based material in a modifying solution for modification treatment to obtain a modified precursor material, followed by heat treatment of the modified precursor material to obtain the modified lithium-rich manganese-based cathode active material. The modified solution contains modifier A and modifier B, wherein modifier A is hydrogen peroxide, and modifier B is at least one of a water-soluble phosphate, pyrophosphate, organophosphonic acid, or organophosphonate. Research in this invention shows that, based on the unique physicochemical structure of lithium-rich manganese and the synergistic effect of modifiers A and B, the air resistance, high-temperature stability, and high-pressure stability of the lithium-rich manganese-based material can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and particularly to the field of modification of lithium-rich manganese-based materials. Background Art

[0002] As a representative of new energy, lithium-ion batteries play an important role in the fields of 3C, energy storage and power batteries. As the core part of lithium-ion batteries, the cathode material plays a crucial role in the performance of lithium-ion batteries. Therefore, it is necessary to prepare a lithium-ion battery cathode material with good performance. [1] .

[0003] The cathode materials used in current commercial lithium-ion batteries are basically LiCoO2 (LCO), LiNi x Co y Mn 1-x-y O2 (NCM), LiNi x Co y Al 1-x-y O2 (NCA), LiFePO4 (LFP) and LiMn2O4 (LMO). However, the manufacturing costs of LCO, NCM and NCA are high and their safety performances are poor. The volumetric energy densities of LFP and LMO are low, which cannot meet the development requirements of the new energy industry. Therefore, it is necessary to develop cathode materials with higher energy density, lower cost and higher safety. The lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn, 0 < x < 1) is regarded as an ideal choice for the next generation of lithium-ion battery cathode materials because of its advantages of ultra-high energy density (theoretical specific capacity > 250 mAhg -1 ), high working voltage, low cost, high safety and low pollution. Although lithium-rich materials have ultra-high capacities, they also have the problem of transition metal dissolution caused by the Jahn-Teller effect, which limits the practical production and application of lithium-rich materials.

[0004] The high capacity of lithium-rich materials mainly comes from the redox of oxygen anions in the Li2MnO3 phase. The irreversible removal of oxygen anions causes the migration of transition metal ions, which destroys the internal structure of the crystal. At the same time, the inhomogeneity of the phase structure and the anisotropic change of the unit cell parameters during the charge and discharge process lead to the accumulation of micro-stress. Although these challenges lead to the gradual formation and growth of nanoscale micropores inside the crystal, the micropores can act as transfer stations for oxygen, making the redox of oxygen anions more reversible. [2]Therefore, modification of the material's mechanical stability is necessary. In addition, the interface between lithium-rich materials and the electrolyte is unstable under high voltage, easily leading to side reactions that cause electrolyte deterioration, producing substances such as HF, damaging the lithium-rich surface structure, and causing transition metal dissolution. Therefore, it is essential to improve its structural stability and electrochemical performance by modifying the material to achieve good cycle stability. Surface design is currently the simplest and most effective method to improve the electrochemical performance of lithium-rich manganese-based cathode materials. For example, Academician Chen Jun's team successfully constructed a multifunctional interface layer on the surface of lithium-rich materials using sorbic acid-assisted interface engineering, featuring a layered-spinel heterostructure and oxygen vacancies. This functional interface layer not only enhances the stability of the material's crystal structure but also improves the activity and reversibility of the lattice oxygen anion redox reaction. The optimally modified sample achieved a maximum discharge capacity of 314.5 mAh g after 150 cycles at 1C. -1 The capacity retention was approximately 87.9%. Furthermore, the treated lithium-rich manganese-based material exhibited high first-cycle coulombic efficiency (88.3%) and low voltage decay (1.26 mV per cycle). [3] Zeng et al. successfully increased the initial coulombic efficiency from 85.3% to 102.5% and achieved a specific capacity of 291.2 mAh·g by treating lithium-rich manganese-based cathode materials with glyoxal in a one-step process. -1 The cycle retention rate was significantly improved (90.1% after 150 cycles and 76.2% after 250 cycles). [4] .

[0005] Traditional surface-modified lithium-rich manganese-based materials can improve cycle performance and first-cycle coulombic efficiency, reduce oxygen release, and improve high-voltage performance. However, insufficient attention has been paid to the Mn dissolution problem, leading to further degradation of the cathode material structure and causing the electrolyte in the system to operate in an oxygen-containing and high-voltage environment. Few specific strategies can further reduce Mn dissolution on top of the above advantages.

[0006] References:

[0007] [1] J.-M. Tarascon and M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature, Vol. 414, No. 6861, pp. 359-367, Nov. 2001, doi: 10.1038 / 35104644.

[0008] [2] X. Zhang, B. Wang, S. Zhao, H. Li and H. Yu, “Oxygen anionic redoxactivated high-energy cathodes: Status and prospects”, eTransportation, Vol. 8, pp. 100118, May 2021, doi: 10.1016 / j.etran.2021.100118.

[0009] [3] P. Yang et al., "Layered-Spinel Heterogeneous Structure and OxygenVacancies Enable Superior Electrochemical Performance for Li-Rich Cathodes", Angewandte Chemie International Edition, Volume 64, Issue 30, Page 202501539, 2025, doi: 10.1002 / anie.202501539.

[0010] [4] T. Zeng et al., "Boosting Initial Coulombic Efficiency in Li-Rich Mn-based Cathodes by Tuning Orbital Hybridization", Angewandte ChemieInternational Edition, Volume 64, Issue 28, Page 202501777, 2025, doi: 10.1002 / anie.202501777. Summary of the Invention

[0011] To address the shortcomings of existing surface modification technologies, the present invention aims to provide a method for preparing modified lithium-rich manganese-based cathode active materials, thereby obtaining active materials with excellent oxygen resistance and high-pressure stability.

[0012] The second objective of this invention is to provide a modified lithium-rich manganese-based positive electrode active material prepared by the aforementioned method and its application in lithium-ion batteries.

[0013] A third objective of this invention is to provide a lithium-ion battery comprising the modified lithium-rich manganese-based cathode active material.

[0014] Lithium-rich manganese-based cathode materials possess higher energy density (>500Wh / kg) and operating voltage (>4.5V), while also offering a cost advantage per unit capacity. However, the structural degradation problem of these materials remains unresolved. To address this issue, this invention provides the following improvement:

[0015] A method for preparing a modified lithium-rich manganese-based cathode active material involves placing a lithium-rich manganese-based material in a modifying solution for modification treatment to obtain a modified precursor material, and then subjecting the modified precursor material to heat treatment to obtain the modified lithium-rich manganese-based cathode active material. The modifying solution contains modifier A and modifier B, wherein modifier A is hydrogen peroxide; and modifier B is at least one of water-soluble phosphate, pyrophosphate, organophosphonic acid, and organophosphonate.

[0016] This invention innovatively involves simultaneous modification of lithium-rich manganese-based materials in a modification solution containing modifier A and modifier B. This allows for the induction of changes in the surface physicochemical structure of the lithium-rich manganese-based materials based on the physicochemical interactions between modifier A and modifier B. For example, it optimizes surface valence states, forms a Mn(III) surface phase, creates oxygen vacancies, and generates a rich P-based gradient interface composition. Research in this invention demonstrates that, based on the unique physicochemical structure of lithium-rich manganese-based materials and the synergistic effect of modifiers A and B, the air resistance, high-temperature stability, and high-pressure stability of lithium-rich manganese-based materials can be effectively improved.

[0017] In this invention, the chemical formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiTMO2, where 0.2≤x≤0.8 and TM is at least one of Ni and Mn.

[0018] The water-soluble phosphate is, for example, a salt of at least one cation selected from sodium, potassium, and ammonium, and at least one anion selected from phosphate, hydrogen phosphate, and dihydrogen phosphate. The pyrophosphate is, for example, a pyrophosphate of at least one cation selected from sodium, potassium, and ammonium. The organophosphonic acid is, for example, a salt of an organophosphonate formed at C1-C2. 10 Organic compounds having 1 to 8 phosphonate groups on their alkyl or alkoxy chains. The organophosphonate is, for example, at least one of the sodium, potassium, or ammonium salts of an organophosphonic acid.

[0019] Preferably, the modifier B is at least one selected from pyrophosphate, organophosphonic acid, and organophosphonate. Research in this invention shows that using the preferred modifier B can further enhance the synergistic effect with modifier A, contributing to further strengthening the material's fast-charging and high-temperature cycling stability.

[0020] In this invention, modifier B includes at least one of sodium pyrophosphate, potassium pyrophosphate, ammonium pyrophosphate, and lithium phytate, more preferably in a weight ratio of 1:0.5~2, and more preferably a mixture of sodium pyrophosphate and lithium phytate in a ratio of 1:1~1.5. Studies have shown that the preferred modifier B can further enhance synergy and help to further improve the air stability, high temperature, and high pressure cycling stability of lithium-rich manganese-based compounds.

[0021] In this invention, the weight ratio of modifier A to modifier B in the modified liquid is 1:(0.5~2.5), which can further be 1:1~2; preferably 1:1.8~2.

[0022] The pH of the modified solution can be 4 to 7.

[0023] In this invention, the weight ratio of lithium-rich manganese-based material to treatment agent B in the modified liquid is 100:0.1~5.0; further, it can be 100:0.3~1; and even further, it can be 100:0.5~0.6.

[0024] In this invention, after modification treatment, the modified precursor is obtained by evaporation.

[0025] In this invention, the heat treatment temperature is 100~200℃, and can be further 150~190℃;

[0026] Preferably, the heat treatment time is 0.5 to 5 hours, and more preferably 1 to 2 hours.

[0027] Preferably, the atmosphere for the heat treatment process is at least one of air, vacuum, nitrogen, or argon.

[0028] The present invention also provides a modified lithium-rich manganese-based positive electrode active material prepared by the preparation method described above.

[0029] The present invention also provides an application of the modified lithium-rich manganese-based positive electrode active material prepared by the above preparation method, characterized in that it is used as a positive electrode active material to prepare lithium-ion batteries.

[0030] The present invention also provides a lithium-ion battery comprising a modified lithium-rich manganese-based positive electrode active material prepared by the preparation method described in the present invention.

[0031] Beneficial effects

[0032] This invention, targeting the unique physicochemical characteristics of lithium-rich manganese-based materials, innovatively employs a combined surface modification treatment using modifiers A and B. This optimizes the Mn valence state, oxygen vacancies, and phase composition of the lithium-rich manganese-based materials, thereby enhancing the structural stability of the surface layer in oxygen and high-voltage environments, reducing manganese dissolution, and providing some resistance to harmful substances such as HF generated during cycling and in the electrolyte, protecting the lithium-rich surface from damage. The modified lithium-rich manganese-based materials of this invention can improve the redox reversibility of oxygen anions, the first-cycle coulombic efficiency, and the capacity. Furthermore, the modified materials described in this invention can coordinate with surface transition metals to inhibit metal ion migration during insertion / extraction, mitigating surface phase transitions. The synergistic functional bridging modification layer can regulate the surface properties and charge transfer of the lithium-rich materials, ensuring good ion diffusion and low charge transfer impedance.

[0033] Furthermore, using one or a combination of pyrophosphate and organophosphorus sources can further synergize with modifier A, which helps to further improve the fast-charging and high-temperature performance of the prepared modified material.

[0034] Moreover, the preparation process provided by this invention is simple and easy to operate, and the electrochemical performance of the modified lithium-rich material is significantly improved, showing broad development prospects. Attached Figure Description

[0035] Figure 1 The results of XPS valence state changes in Example 1 and Comparative Example 1;

[0036] Figure 2 The images show the TEM surface differences between Example 1 and Comparative Example 1; the left image shows the material of Comparative Example 1, and the right image shows the material of Example 1.

[0037] Figure 3 For the lithium-rich material Li in Comparative Example 1 1.2 Ni 0.2 Mn 0.6 SEM image of O2;

[0038] Figure 4 SEM image of the lithium-rich material prepared in Example 1;

[0039] Figure 5 EPR test results for oxygen vacancies in Example 1 and Comparative Example 1;

[0040] Figure 6 The graphs show the 100-cycle-capacity curves of Example 1 and Comparative Example 1 at 1C rate;

[0041] Figure 7 The images show SEM images of Example 1 and Comparative Example 1 after 300 cycles; the left image shows the material of Comparative Example 1, and the right image shows the material of Example 1.

[0042] Figure 8 Analysis of dissolution components after 300 cycles for Example 1 and Comparative Example 1. Detailed Implementation

[0043] Example 1

[0044] Step 1:

[0045] Weigh 10g of lithium-rich manganese-based cathode material Li 1.2 Mn 0.6 Ni 0.2 O2 was dissolved in 15 ml of deionized water, and the mixture was sonicated for 60 min and stirred for 60 min, alternating the stirring time three times. The temperature was then raised to 70 °C and stirred continuously until a homogeneous solution was formed. Next, 0.025 g of modifier A (hydrogen peroxide, H2O2, 35%) and modifier B (0.025 g sodium pyrophosphate + 0.025 g lithium phytate) were weighed and dissolved in 10 ml of deionized water. The mixture was stirred for 30 min and then added to the lithium-rich manganese-based homogeneous solution. Stirring was maintained at 70 °C until the solvent dried. The mixture was then dried at 70 °C using forced air drying to obtain a mixture. After grinding, the mixture was treated at 160 °C in an argon atmosphere for 1 h to obtain lithium-rich Li with a stable surface coating. 1.2 Mn 0.6 Ni 0.2 O2.

[0046] Step 2:

[0047] Weigh the modified lithium-rich Li from step 1 according to a mass ratio of 8:1:1. 1.2 Mn 0.6 Ni 0.2 O2, acetylene black, and polyvinylidene fluoride (PVDF) are ground evenly, and then an appropriate amount of NMP is added to make a mixed slurry. The slurry is then evenly coated onto aluminum foil with a scraper and placed in a vacuum drying oven at 120°C for 8 hours. Finally, the electrode is rolled and stamped to obtain an electrode with a diameter of 14 mm.

[0048] Finally, 2025 coin cell half-cells were assembled in a super-clean glove box. Except for the positive electrode, the remaining components are as follows: the electrolyte is EC:DMC:DEC = 1:1:1, containing 1 mol / L LiPF6. The separator is a Celgard 2400 membrane. A lithium sheet is used as the counter electrode. In electrochemical testing, 1C = 250 mA g / g -1 To determine the nominal specific capacity, charge-discharge cycle tests were conducted at 1C rate, 25℃ or 50℃, within a voltage range of 2~4.8V; the results are shown in Table 1.

[0049] Example 2

[0050] Compared with Example 1, the only difference is that modifier B is sodium pyrophosphate; the amount of modifier B (also 0.05g) and other operations and parameters are the same as in Example 1.

[0051] Example 3

[0052] Compared with Example 1, the only difference is that the modifier B is lithium phytate; the amount of modifier B (also 0.05g) and other operations and parameters are the same as in Example 1.

[0053] Example 4

[0054] Compared with Example 1, the only difference is that the modifier B is ammonium phosphate; the amount of modifier B (also 0.05g) and other operations and parameters are the same as in Example 1.

[0055] Example 5

[0056] Weigh 10g of lithium-rich manganese-based cathode material Li 1.2 Mn 0.6 Ni 0.2 O2 was dissolved in 15 ml of deionized water, and the mixture was sonicated for 60 min and stirred for 60 min, alternating the process three times. The temperature was then raised to 75 °C and stirred continuously until a homogeneous solution was formed. Next, 0.03 g of hydrogen peroxide (H2O2, 35%) and 0.05 g of modifier B (comprising sodium pyrophosphate and lithium phytate in a 1:1.5 weight ratio) were weighed and dissolved in 10 ml of deionized water. The mixture was stirred for 30 min and then added to the lithium-rich manganese-based homogeneous solution. Stirring was maintained at 75 °C until the solvent dried. The mixture was then dried at 70 °C using forced air to obtain a mixture. After grinding, the mixture was treated at 180 °C in an argon atmosphere for 2 h to obtain lithium-rich Li with a stable surface coating. 1.2 Mn 0.6 Ni 0.2 O2.

[0057] Comparative Example 1

[0058] Compared with Example 1, the only difference is that modifier B was not added; the missing components were supplemented by an equal amount of modifier A, and all other operations and parameters were the same as in Example 1.

[0059] Comparative Example 2

[0060] Compared with Example 1, the only difference is that an equal weight of potassium permanganate is used as modifier A; all other operations and parameters are the same as in Example 1.

[0061] Comparative Example 3

[0062] Compared with Example 1, the only difference is that modifier A was not added, and the missing components were supplemented by modifier B in equal amounts. All other operations and parameters are the same as in Example 1.

[0063] Comparative Example 4

[0064] Compared with Example 1, the only difference is that modifier B is replaced with an equal weight of sorbic acid; all other operations and parameters are the same as in Example 1.

[0065] Comparative Example 5

[0066] Compared to Example 1, the only difference is that modifier A and modifier B are not treated simultaneously in one batch; the steps are as follows:

[0067] Weigh 10g of lithium-rich manganese-based cathode material Li 1.2 Mn 0.6 Ni 0.2 Dissolve O2 in 15 ml of deionized water, sonicate for 30 min and stir for 30 min, alternating the process three times, then heat to 70 °C and continue stirring until a homogeneous solution is formed.

[0068] First stage of modification: Weigh 0.025g of hydrogen peroxide (H2O2, 35%), dissolve it in 5ml of deionized water, stir for 30min, then add it to the lithium-rich manganese-based homogeneous solution, and keep stirring at 70℃ until the solvent dries up;

[0069] Second stage of modification: Weigh out 0.025g sodium pyrophosphate (Na4P2O7) + 0.025g lithium phytate (C6H6Li6O) 24 P6 was dissolved in 5 ml of deionized water and stirred for 30 min. It was then mixed with the first-stage modified product and stirred continuously at 70 °C until the solvent dried. The mixture was then dried under forced-air drying at 70 °C to obtain a final product. After grinding, the mixture was treated at 160 °C in an argon atmosphere for 1 h to obtain lithium-rich Li2O3, which underwent the first stage of modification in modifying solution A and the second stage of modification in modifying agent B. 1.2 Mn 0.6 Ni 0.2 O2.

[0070] Comparative Example 6

[0071] Compared to Example 1, the only difference is that modifier A and modifier B are not treated simultaneously in one batch; the steps are as follows:

[0072] Weigh 10g of lithium-rich manganese-based cathode material Li 1.2 Mn 0.6 Ni 0.2 Dissolve O2 in 15 ml of deionized water, sonicate for 30 min and stir for 30 min, alternating the process three times, then heat to 70 °C and continue stirring until a homogeneous solution is formed.

[0073] First stage of modification: Weigh 0.025g sodium pyrophosphate (Na4P2O7) + 0.025g lithium phytate (C6H6Li6O)24 P6), dissolved in 5 ml of deionized water, stirred for 30 min, then added to a lithium-rich manganese-based homogeneous solution, and stirred continuously at 70 °C until the solvent dries up;

[0074] Second stage modification: Weigh 0.025g of hydrogen peroxide (H2O2, 35%), dissolve it in 5ml of deionized water, stir for 30min, then add it to the first stage modified lithium-rich manganese-based solution, and continue stirring at 70℃ until the solvent dries. Dry the mixture at 70℃ using forced air to obtain a mixture, grind it, and then treat it at 160℃ in an argon atmosphere for 1h to obtain lithium-rich Li2O3 that underwent the first stage modification in modifier B and subsequently the second stage modification in modifying solution A. 1.2 Mn 0.6 Ni 0.2 O2. Other operations and parameters are the same as in Example 1.

[0075] The test results for each case are shown in Table 1:

[0076]

[0077] As demonstrated in Examples 1 and Comparative Examples 1-6, the innovative simultaneous modification of lithium-rich manganese-based materials in a modification solution containing modifier A and modifier B allows for the induction of changes in the surface physicochemical structure of the lithium-rich manganese-based materials based on the physicochemical interaction between modifier A and modifier B. This includes optimizing surface valence states, forming a Mn(III) surface phase, creating oxygen vacancies, and establishing a rich P-based gradient interface composition. This invention demonstrates that the unique physicochemical structure of lithium-rich manganese-based materials and the synergistic effect of modifiers A and B can effectively improve the air resistance, high-temperature stability, and high-pressure stability of lithium-rich manganese-based materials.

[0078] Furthermore, as can be seen from Examples 1-4, modifier B, which combines sodium pyrophosphate and lithium phytate, can further synergize with modifier A to further optimize the surface physicochemical structure of lithium-rich manganese-based materials and improve their high-pressure and high-temperature performance.

Claims

1. A preparation method of a modified lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based material is placed in a modification liquid for modification treatment to obtain a modified precursor substance, and the modified precursor substance is then heat-treated to prepare the modified lithium-rich manganese-based positive electrode active material; characterized in that, The modified liquid contains modifier A and modifier B, wherein modifier A is hydrogen peroxide; and modifier B includes at least one of sodium pyrophosphate, potassium pyrophosphate, ammonium pyrophosphate, and lithium phytate. ​ In the modified liquid, the weight ratio of modifier A to modifier B is 1:(0.5~2.5). The heat treatment temperature is 100~200℃; the heat treatment time is 0.5~5h.

2. The preparation method of the modified lithium-rich manganese-based positive electrode active material as described in claim 1, characterized in that, The chemical formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiTMO2, where 0.2≤x≤0.8 and TM is at least one of Ni and Mn.

3. The preparation method of the modified lithium-rich manganese-based positive electrode active material as described in claim 1, characterized in that, Modifier B is a mixture of sodium pyrophosphate and lithium phytate in a weight ratio of 1:0.5~2.

4. The preparation method of the modified lithium-rich manganese-based positive electrode active material as described in claim 1, characterized in that, The weight ratio of lithium-rich manganese-based material to treatment agent B in the modified liquid is 100:0.1~5.

0.

5. The preparation method of the modified lithium-rich manganese-based positive electrode active material as described in claim 4, characterized in that, The weight ratio of lithium-rich manganese-based material to treatment agent B in the modified liquid is 100:0.3~1.

6. The method for preparing the modified lithium-rich manganese-based positive electrode active material as described in claim 4, characterized in that, The weight ratio of lithium-rich manganese-based material to treatment agent B in the modified liquid is 100:0.5~0.

6.

7. The preparation method of the modified lithium-rich manganese-based positive electrode active material as described in claim 1, characterized in that, After modification, the modified precursor is obtained by evaporation.

8. The method for preparing the modified lithium-rich manganese-based positive electrode active material as described in claim 1, characterized in that, The atmosphere during the heat treatment process is at least one of air, vacuum, nitrogen, or argon.

9. A modified lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a modified lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 1 to 8, characterized in that, It is used as a positive electrode active material in the preparation of lithium-ion batteries.

11. A lithium-ion battery, characterized in that, The modified lithium-rich manganese-based positive electrode active material prepared by the preparation method according to any one of claims 1 to 8.

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