A method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure

Abstract

A method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure involves adding lithium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid monohydrate complexing agent to deionized water and mixing thoroughly. Then, aminosulfonic acid is added and stirred until homogeneous, yielding a precursor salt solution. The precursor salt solution is then subjected to spray pyrolysis to prepare precursor powder. Finally, the precursor powder is calcined at high temperature in a muffle furnace to obtain modified lithium-rich manganese-based cathode material powder. The advantages are: this method helps reduce side reactions during cycling and improves the efficiency of lithium-rich manganese cathode materials. + Improving the diffusion rate and suppressing harmful phase transitions during cycling can significantly enhance the stability of materials, slow down voltage decay, and improve cycling performance and voltage retention.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathodes, specifically relating to a method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodic alternating composite structure. Background Technology

[0002] Driven by the rapid growth in energy demand and the pursuit of sustainable development, lithium-ion batteries, with their significant advantages such as high energy density and long cycle life, have become a key force in the energy storage field, widely used in static energy storage, smart grids, and electric vehicles. As the global energy structure accelerates its transition to cleaner and lower-carbon energy, the large-scale grid connection of intermittent renewable energy sources such as wind and solar power has created unprecedented demands for efficient, safe, and long-life energy storage systems. Lithium-ion batteries mainly consist of a positive electrode, a negative electrode, a separator, and an electrolyte. Technological breakthroughs in positive electrode materials are crucial for improving battery performance, directly determining key performance indicators such as energy density, safety, cycle life, and temperature adaptability.

[0003] Traditional cathode materials, such as lithium cobalt oxide, lithium iron phosphate, and nickel-cobalt-manganese ternary materials, dominate lithium-ion battery systems. However, their theoretical specific capacity is generally limited by crystal structure and electrochemical reaction mechanisms, making it difficult to meet the development needs of next-generation high-energy-density batteries. For example, while lithium iron phosphate has good safety performance and long cycle life, its energy density is relatively low. Lithium-rich manganese-based cathode materials, with their unique anionic oxygen redox mechanism, exhibit high energy density and are considered key candidate materials for breaking through existing energy density bottlenecks. However, the commercial application of lithium-rich manganese-based cathode materials is limited by the material structural instability and voltage decay caused by transition metal migration during cycling.

[0004] Currently, the electrochemical performance of lithium-rich manganese-based cathode materials can be improved through surface modification and element doping. Although this can improve cycle stability to some extent, it still cannot effectively prevent transition metal migration and irreversible structural evolution. This will lead to continuous decay of discharge voltage during cycling. Therefore, there is an urgent need for a method to prepare lithium-rich manganese-based cathode materials that can achieve good cycle performance while slowing down voltage decay. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally alternating spinel-disordered phase composite structure. This method helps to reduce side reactions during cycling and improve the efficiency of Li-rich manganese cathode materials. + Improving the diffusion rate and suppressing harmful phase transitions during cycling can significantly enhance the stability of materials, slow down voltage decay, and improve cycling performance and voltage retention.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally alternating spinel-disordered phase composite structure, the specific steps of which are as follows: Step 1: Prepare the precursor salt solution: Lithium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid monohydrate complexing agent were added to 1L of deionized water and mixed evenly to form a metal salt solution with a total concentration of 0.6mol / L for lithium acetate, nickel acetate, cobalt acetate, and manganese acetate. Aminosulfonic acid was added and stirred evenly to obtain a precursor salt solution containing an aminosulfonic acid concentration of 0.3g / L-1.5g / L. Step 2: Preparation of precursor powder: Precursor powder was prepared by spray pyrolysis of precursor salt solution; Step 3: Preparation of modified lithium-rich manganese-based cathode materials: The precursor powder was calcined at high temperature in a muffle furnace to obtain modified lithium-rich manganese-based cathode material powder.

[0007] Furthermore, the concentration of aminosulfonic acid in the precursor salt solution is 0.9 g / L-1.5 g / L, forming a spinel-disorder phase periodically alternating composite structure to enhance the rate capability, improve the stability and cycle stability of the material.

[0008] Furthermore, the concentration of the monohydrated citric acid complexing agent in the precursor salt solution is 0.6 mol / L.

[0009] Furthermore, the molar ratio of the lithium acetate, nickel acetate, cobalt acetate, and manganese acetate is 3.7:0.4:0.4:1.6.

[0010] Furthermore, the acetate of lithium is lithium acetate dihydrate, the acetate of nickel is nickel acetate tetrahydrate, the acetate of cobalt is cobalt acetate tetrahydrate, and the acetate of manganese is manganese acetate tetrahydrate.

[0011] Furthermore, in step three, the high-temperature calcination is carried out at a temperature of 1000℃ for 20 minutes, followed by natural cooling to room temperature.

[0012] Further optimization is that during high-temperature calcination, the heating rate is 3℃ / min.

[0013] Further preferred, the concentration of aminosulfonic acid in the precursor salt solution is 0.9 g / L.

[0014] Furthermore, in step one, the stirring speed is 400 r / min and the stirring time is 2 hours.

[0015] Furthermore, in step two, the inlet and outlet temperatures during the spray drying process are set to 230℃ and 120℃, respectively, and the peristaltic speed is set to 20 rpm.

[0016] The beneficial effects of this invention are: (1) By modifying the lithium-rich manganese-based cathode material with aminosulfonic acid, an amorphous protective layer is formed on the surface during the preparation process, which can reduce the side reactions between the cathode and the electrolyte and improve the cycle stability. Within the voltage range of 2-4.8V, after 500 cycles at 1C current, the capacity retention rate reaches 90.58%, which greatly improves the cycle stability of the battery.

[0017] (2) The present invention modifies lithium-rich manganese-based cathode material with aminosulfonic acid to generate a composite structure in which spinel phase and disorder phase are alternately distributed. The spinel generated in situ can accelerate lithium-ion transport and suppress phase change during cycling to maintain the stability of the material structure, thereby improving the median discharge voltage of the material. At the same time, the disorder phase can suppress the migration of transition metals, thereby improving the structural stability of the material.

[0018] (3) The present invention only requires the addition of appropriate aminosulfonic acid when preparing the precursor metal solution. The preparation method is simple and the effect is significant. The performance is better than most lithium-rich manganese cathode materials, which is conducive to large-scale application. Attached Figure Description

[0019] Figure 1 The images are XRD patterns before cycling of the present invention (corresponding to Examples 1, 2, 3 and Comparative Examples 1, 3, 4, 5, and 6). Figure 2 This is a comparison chart of Raman spectroscopy before cycling in the present invention (corresponding to Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1); Figure 3 These are SEM images of the present invention (corresponding to Embodiment 1, Embodiment 2, Embodiment 3, and Comparative Example 1); Figure 4 These are TEM images of the present invention (corresponding to Embodiment 1, Embodiment 2, Embodiment 3 and Comparative Example 1) before cycling; Figure 5 These are in-situ XRD comparison images of the present invention (corresponding to Example 2 and Comparative Example 1); Figure 6 This is a comparison chart of the first charge and discharge at 0.1C for the present invention (corresponding to Examples 1-3 and Comparative Examples 1-6); Figure 7 This is a comparison chart of the rate performance of the present invention (corresponding to Examples 1-3 and Comparative Examples 1-2); Figure 8This is a comparison diagram of the 1C cycle of the present invention (corresponding to Examples 1-3 and Comparative Examples 1-6); Figure 9 This is a comparison chart of voltage decay after 500 cycles at 1C for the present invention (corresponding to Examples 1-3 and Comparative Example 1); Figure 10 This is a comparison diagram of lithium-ion diffusion at 0.1C for the present invention (corresponding to Example 2 and Comparative Example 1); Figure 11 The CV comparison diagrams for the present invention (corresponding to Example 2 and Comparative Example 1) are shown. Figure 12 This is a comparison of XRD patterns after 200 cycles of the present invention (corresponding to Example 2 and Comparative Example 1); Figure 13 This is a Raman comparison chart of the present invention (corresponding to Example 2 and Comparative Example 1) after 200 cycles. Detailed Implementation

[0020] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0021] Example 1 Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 0.3 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1000°C in a box furnace at a rate of 3°C / min. The temperature was held at 1000°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0022] Example 2 The difference in this embodiment is that the amount of aminosulfonic acid added in step 1 is 0.9g, while the rest is the same as in embodiment 1.

[0023] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 0.9 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1000°C in a box furnace at a rate of 3°C / min. The temperature was held at 1000°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0024] Example 3 The difference in this embodiment is that the amount of aminosulfonic acid added in step 1 is 1.5g, while the rest is the same as in embodiment 1.

[0025] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 1.5 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1000°C in a box furnace at a rate of 3°C / min. The temperature was held at 1000°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li.1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0026] Comparative Example 1 The difference in this embodiment is that aminosulfonic acid is not added in step 1; otherwise, it is the same as in embodiment 3.

[0027] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, place in a magnetic stirrer, and stir at 400 r / min for 2 h to obtain the precursor solution; Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1000°C in a box furnace at a rate of 3°C / min. The temperature was held at 1000°C for 20 min, and then naturally cooled to room temperature to obtain the lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0028] Comparative Example 2 The difference in this embodiment is that the amount of aminosulfonic acid added in step 1 is 2.1g, while the rest is the same as in embodiment 3.

[0029] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 2.1 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1000°C in a box furnace at a rate of 3°C / min. The temperature was held at 1000°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0030] Comparative Example 3 The difference in this embodiment is that in step 3, the temperature is raised to 800°C at a rate of 3°C / min in a box furnace and held at 800°C for 20 minutes. Otherwise, it is the same as in embodiment 2.

[0031] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 0.9 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 800°C in a box furnace at a rate of 3°C / min. The temperature was held at 800°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0032] Comparative Example 4 The difference in this embodiment is that in step 3, the temperature is raised to 900°C at a rate of 3°C / min in a box furnace and held at 900°C for 20 minutes. Otherwise, it is the same as in embodiment 2.

[0033] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 0.9 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 900°C in a box furnace at a rate of 3°C / min. The temperature was held at 900°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0034] Comparative Example 5 The difference in this embodiment is that in step 3, the temperature is raised to 1100°C at a rate of 3°C / min in a box furnace and held at 1100°C for 20 minutes. Otherwise, it is the same as in embodiment 2.

[0035] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate, dissolve them in 1 L of deionized water, add 126.084 g of citric acid monohydrate as a complexing agent, and add 0.9 g of aminosulfonic acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1100°C in a box furnace at a rate of 3°C / min. The temperature was held at 1100°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0036] Comparative Example 6 The difference in this embodiment is that 0.9g of fumaric acid was added in step 1, while the rest is the same as in Comparative Example 1.

[0037] Step 1: Prepare the precursor solution Weigh out 38.1963 g of lithium acetate dihydrate, 9.7048 g of nickel acetate tetrahydrate, 9.7141 g of cobalt acetate tetrahydrate and 39.7046 g of manganese acetate tetrahydrate and dissolve them in 1 L of deionized water. Add 126.084 g of citric acid monohydrate as a complexing agent and 0.9 g of fumaric acid. Place the mixture in a magnetic stirrer and stir at 400 r / min for 2 h to obtain the precursor solution. Step 2: Preparation of precursor powder The precursor solution was granulated by spray drying at a feed rate of 10 mL / min, an inlet air temperature of 230℃, an outlet air temperature of 120℃, and a peristaltic speed of 20 rpm to obtain precursor powder. Step 3: Preparation of modified lithium-rich manganese-based cathode materials The precursor powder was placed in an alumina crucible and heated to 1000°C in a box furnace at a rate of 3°C / min. The temperature was held at 1000°C for 20 min, and then naturally cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material Li. 1.2 Co 0.13 Ni 0.13 Mn 0.54 O2.

[0038] Physicochemical property testing of the embodiments and comparative examples of the present invention The pre-cycle XRD comparison images of Comparative Example 1, Example 1, Example 2, Example 3, Comparative Example 3, Comparative Example 4, Comparative Example 5 and Comparative Example 6 of this invention are shown below. Figure 1 As shown, by Figure 1 The peak shapes before and after the addition of aminosulfonic acid are consistent, and there are no obvious impurity peaks, indicating that aminosulfonic acid does not affect the structure of the lithium-rich manganese-based cathode material. The difference lies in the increased 003 / 104 ratio of the aminosulfonic acid-added sample, indicating increased orderliness. This suggests that improving orderliness is beneficial to improving electrochemical performance. Simultaneously, the 003 peak shifts to a lower angle, indicating an increase in the c-axis. From the magnified local image, a spinel peak appears at approximately 18.8° in the modified sample, indicating the in-situ formation of a spinel phase after modification. The expanded interlayer spacing and the formation of three-dimensional lithium-ion channels accelerate lithium-ion diffusion, thereby improving the rate performance of the material. Comparison of the XRD patterns of Comparative Examples 3, 4, and 5 shows that the materials prepared by calcination at 800℃ and 900℃ for 20 min cannot form a spinel phase, while calcination at 1100℃ for 20 min can form a spinel phase. Meanwhile, the effect of 0.9 g / L fumaric acid on the lithium-rich manganese structure was compared, as shown in Comparative Example 6. It was found that this substance does not promote the formation of the spinel phase.

[0039] The pre-cycle Raman plots of Comparative Example 1, Example 1, Example 2, and Example 3 of this invention are shown below. Figure 2 As shown, by Figure 2As can be seen, after modification with aminosulfonic acid, at 650 cm⁻¹ -1 The appearance of shoulder peaks on the left and right is a characteristic peak of the spinel phase, which further proves that the modified sample produced a spinel phase. An appropriate amount of spinel phase is beneficial to lithium ion transport, thereby improving rate performance.

[0040] The pre-cycle SEM images of Comparative Example 1, Example 1, Example 2, and Example 3 of this invention are shown below. Figure 3 As shown, by Figure 3 It can be seen that the particle size decreases after the addition of aminosulfonic acid, which effectively increases the specific surface area and the number of active sites. However, as the amount of aminosulfonic acid added increases, the particles agglomerate, thereby deteriorating the electrochemical performance of the material.

[0041] The TEM images of Comparative Example 1, Example 1, Example 2, and Example 3 before cycling are shown below. Figure 4 As shown in Comparative Example 1, the unmodified sample exhibited clear stripes and a distinct layered structure. With the addition of aminosulfonic acid, areas with unclear stripes appeared in Example 1. Fourier transform revealed the formation of a composite region with alternating spinel and rock salt phase regions. With further addition of aminosulfonic acid, a composite region with alternating spinel (region 1) and local disorder (region 2) appeared on the surface of Example 2, forming an amorphous protective layer on the particle surface. With further addition of aminosulfonic acid, a larger area of ​​rock salt phase formed in Example 3. From Examples 1 to 3, it can be seen that with the increase of aminosulfonic acid, the local area of ​​the material exhibits a change process of "layered phase - spinel - disordered intermediate state - rock salt phase". This periodically alternating composite structure of spinel and disordered phase in Example 2 can enhance the rate performance of the material while inhibiting the migration of transition metals, thereby improving the stability of the material.

[0042] TEM images of Comparative Example 1 and Example 2 before cycling are shown below. Figure 4 As shown, the amorphous protective layer can reduce side reactions between the material and the electrolyte, further improving the cycling stability of the material.

[0043] The in-situ XRD test images of Comparative Example 1 and Example 2 of this invention are as follows: Figure 5 As shown, by Figure 5 It can be seen that after the first cycle, the 003 peaks of Comparative Example 1 and Example 2 shifted by 0.179° and 0.164° respectively. This indicates that Example 2 has better reversibility, which is beneficial to improving cycle stability.

[0044] The initial discharge curves of Comparative Examples 1-6 and Examples 1-3 of the present invention are as follows: Figure 6 As shown, by Figure 6It can be seen that the discharge capacity at 0.1C gradually decreases with the increase of aminosulfonic acid. The first discharge capacity of the material prepared by calcination at 900℃ after modification with 0.9 g / L aminosulfonic acid is significantly improved. The lithium-rich manganese modified with 0.9 g / L fumaric acid has an adverse effect on the first discharge at 0.1C.

[0045] The magnification test charts of Comparative Examples 1-2 and Examples 1-3 of this invention are shown below. Figure 7 As shown, by Figure 7 It can be seen that with the increase of aminosulfonic acid, the rate performance first increases and then decreases, with Example 1 showing the best rate performance.

[0046] The comparison graph of the cycle performance of Comparative Examples 1-6 and Examples 1-3 of the present invention is shown in the figure. Figure 8 As shown, by Figure 8 It can be seen that after 500 cycles at 1C, Example 2 has the highest capacity.

[0047] The voltage decay comparison diagram of Comparative Example 1 and Examples 1-3 of the present invention is shown in the figure below. Figure 9 As shown in the figure, the median voltage after 500 cycles gradually increases with the increase of aminosulfonic acid. The voltage decay in Example 3 is the slowest, with a voltage retention rate of 83.60% after 500 cycles and a voltage decay rate of 1.37mV / cycle to 1.14mV / cycle.

[0048] Li of Comparative Example 1 and Example 2 of the present invention + Diffusion coefficient comparison chart as follows Figure 10 As shown in the figure, the diffusion coefficient of Example 2 is consistently higher than that of Comparative Example 1 during the charging and discharging process, indicating that aminosulfonic acid modification can significantly improve the diffusion coefficient of Li. + The diffusion coefficient of Li accelerates the diffusion of Li + The transmission.

[0049] The CV comparison diagram between Comparative Example 1 and Example 2 of this invention is shown below. Figure 11 As shown in the figure, Example 2 exhibits an oxidation peak at 3V and a reduction peak at 2.5V, which further indicates that the spinel phase was generated after modification with aminosulfonic acid. The peak current of Example 2 is higher than that of Comparative Example 1, indicating that the modified material significantly improves the kinetic performance.

[0050] The XRD comparison diagrams of Comparative Example 1 and Example 2 after 200 cycles are shown below. Figure 12 As shown in the figure, Comparative Example 1 produced a harmful spinel-like phase after 200 cycles. This spinel-like phase hindered the Li + The diffusion and embedding of the modified sample were observed in Example 1, while no similar phase transition occurred in Example 2, indicating that the modified sample did not undergo a harmful phase transition, maintaining structural stability and thus improving cycle stability.

[0051] The Raman comparison diagrams of Comparative Example 1 and Example 2 after 200 cycles are shown below. Figure 13 As shown in the figure, Comparative Example 1 is at 707cm. -1 New characteristic peaks were generated on the left and right sides, which belong to the spinel-like phase. This is consistent with the XRD characterization results after 200 cycles, further proving that the modified sample can effectively suppress harmful phase transitions during cycling.

[0052] The modified lithium-rich manganese-based cathode materials, Super-P powder, and a 1.2% (w / w) CMC aqueous solution prepared in Examples 1-3 and Comparative Examples 1-2 were mixed in a mass ratio of 253:32:1250. After ball milling for 4 hours, the mixture was coated onto aluminum foil and vacuum dried at 110°C for 20 hours. After cutting, it was vacuum dried again for 10 hours and then transferred into a glove box for assembling coin cells. Tests were conducted, and the results are shown in Table 1. Table 1 As shown in Table 1, adding a small amount of aminosulfonic acid in Example 1 had a significant impact on the capacity; in Example 2, the capacity decreased slightly after further addition, but the cycling performance was significantly improved; in Example 3, the overall performance decreased slightly after excessive addition, and as shown in Comparative Example 2, the performance decreased significantly after further addition. Example 2 had the best performance, with a capacity retention rate of 90.58% after 500 cycles at 1C.

[0053] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally alternating spinel-disordered phase composite structure, characterized in that: The specific steps are as follows: Step 1: Prepare the precursor salt solution: Lithium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid monohydrate complexing agent were added to 1L of deionized water and mixed evenly to form a metal salt solution with a total concentration of 0.6mol / L for lithium acetate, nickel acetate, cobalt acetate, and manganese acetate. Aminosulfonic acid was added and stirred evenly to obtain a precursor salt solution containing an aminosulfonic acid concentration of 0.3g / L-1.5g / L. Step 2: Preparation of precursor powder: Precursor powder was prepared by spray pyrolysis of precursor salt solution; Step 3: Preparation of modified lithium-rich manganese-based cathode materials: The precursor powder was calcined at high temperature in a muffle furnace to obtain modified lithium-rich manganese-based cathode material powder.

2. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally alternating spinel-disordered phase composite structure according to claim 1, characterized in that: The concentration of aminosulfonic acid in the precursor salt solution is 0.9 g / L-1.5 g / L.

3. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally alternating spinel-disordered phase composite structure according to claim 1, characterized in that: The concentration of the monohydrated citric acid complexing agent in the precursor salt solution is 0.6 mol / L.

4. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally alternating spinel-disordered phase composite structure according to claim 1, characterized in that: The molar ratio of the acetates of lithium, nickel, cobalt, and manganese is 3.7:0.4:0.4:1.

6.

5. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure according to claim 1, characterized in that: The acetate of lithium is lithium acetate dihydrate, the acetate of nickel is nickel acetate tetrahydrate, the acetate of cobalt is cobalt acetate tetrahydrate, and the acetate of manganese is manganese acetate tetrahydrate.

6. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure according to claim 1, characterized in that: In step three, the high-temperature calcination is carried out at a temperature of 1000℃ for 20 minutes, followed by natural cooling to room temperature.

7. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure according to claim 6, characterized in that: During high-temperature calcination, the heating rate is 3℃ / min.

8. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure according to claim 2, characterized in that: The concentration of aminosulfonic acid in the precursor salt solution was 0.9 g / L.

9. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure according to claim 1, characterized in that: In step one, the stirring speed is 400 r / min and the stirring time is 2 hours.

10. The method for constructing a lithium-rich manganese cathode material with an amorphous protective layer and a locally spinel-disordered phase periodically alternating composite structure according to claim 1, characterized in that: In step two, the inlet and outlet temperatures during the spray drying process are set to 230℃ and 120℃, respectively, and the peristaltic speed is set to 20 rpm.

Images