Ferrous oxalate / lithium stearate composite negative electrode material and preparation method thereof
By introducing lithium stearate during the preparation of ferrous oxalate, a stable ferrous oxalate/lithium stearate composite material is formed, which solves the problem of poor structural stability of ferrous oxalate, improves the conductivity and cycle stability of lithium-ion batteries, and enhances the electrochemical performance of the batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2024-08-29
- Publication Date
- 2026-07-21
AI Technical Summary
When ferrous oxalate is used as an anode material in lithium-ion batteries, its structural stability is poor, resulting in low conductivity and poor cycle stability.
By introducing lithium stearate into the preparation process of ferrous oxalate, mixing it using a planetary ball mill and calcining it at different temperatures, a ferrous oxalate/lithium stearate composite material is formed, which enhances the structural stability and interfacial contact of the material and forms a stable SEI film.
It improves the conductivity and ion migration rate of the material, enhances the cycle stability and electrochemical performance of the battery, and increases the discharge specific capacity and cycle life of the material.
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Figure CN121641809B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of lithium-ion battery anode materials, specifically relating to a stable rod-shaped lithium-ion battery ferrous oxalate / lithium stearate composite anode material and its preparation method. Background Technology
[0002] Due to limitations in discharge capacity and raw material scarcity of traditional lithium-ion battery (LIB) anode materials such as graphite and lithium titanate, research focusing on exploring novel anode materials has significantly increased in recent years. This includes research on silicon-based, tin-based, and transition metal oxide / oxalate (TMOs / TMOxs) materials. In various TMOs... x Ferrous oxalate has attracted much attention due to its high theoretical specific capacity, cost-effectiveness, and abundant resources. In 2008, Tirada conducted preliminary research on ferrous oxalate as an anode material for lithium-ion batteries (LIBs), demonstrating its excellent electrochemical performance, such as high discharge specific capacity, appropriate charge-discharge voltage, and good rate performance. Subsequently, ferrous oxalate, with its charge-discharge mechanism based on conversion reactions, became a widely studied subject. Researchers have also investigated the changes in electrochemical performance of ferrous oxalate with different crystal types and morphologies, focusing on the interfacial properties of the ferrous oxalate anode. These findings emphasize the importance of controlling crystal form and particle morphology to obtain ferrous oxalate anode materials with excellent electrochemical performance.
[0003] Ferrous oxalate is prone to structural damage and particle pulverization during calcination and dehydration, resulting in low initial cycle efficiency and poor cycle stability when used as a negative electrode material. Therefore, solving this problem is urgently needed. Summary of the Invention
[0004] To overcome the problems of low conductivity and poor cycle stability caused by poor structural stability in existing ferrous oxalate materials, this invention provides a ferrous oxalate / lithium stearate composite anode material and its preparation method. The objective of this invention is achieved through the following technical solution, the specific steps of which are as follows:
[0005] Step (1): Add ferrous sulfate solution to oxalic acid solution dissolved in ethanol, age in a reactor at 60°C for 12 hours, filter, wash and dry to obtain ferrous oxalate dihydrate precursor;
[0006] Step (2): Place an appropriate amount of ferrous oxalate dihydrate and lithium stearate with a mass fraction of 1-7% in a planetary ball mill and grind them thoroughly at a speed of 2500 r for 2 hours to obtain a mixed precursor.
[0007] Step (3): The mixed precursor obtained in step (2) is subjected to a first-stage calcination under an inert atmosphere (argon or nitrogen) with a heating rate of 5℃ / min, a sintering temperature of 220~240℃, and a holding time of 1h. Then, the calcination temperature is controlled at 290~300℃ and the holding time is 2h for a second-stage calcination to obtain the ferrous oxalate / lithium stearate composite anode material.
[0008] In step (2), the mass ratio of ferrous oxalate dihydrate to lithium stearate is 100:1~7.
[0009] The beneficial effects of this invention are:
[0010] Utilizing an environmentally friendly and efficient process, this invention, based on the liquid-phase precipitation method for material preparation, significantly improves the structural stability of ferrous oxalate particles by introducing stable lithium salt modification during the sintering process. During the first-stage calcination, lithium stearate completely melts and uniformly diffuses onto the surface of ferrous oxalate, preventing structural collapse and interlayer displacement caused by the loss of crystal water support during the subsequent second-stage calcination of dihydrated ferrous oxalate. Furthermore, during charge and discharge, the polar bonds of the lithium stearate particles coated on the ferrous oxalate surface increase the effective contact between the electrolyte and the material particles at the interface, enhancing the material's conductivity, ion migration rate, and structural stability. A stable SEI film can be formed during battery charge and discharge, resulting in varying degrees of improvement in battery cycle stability and electrochemical performance. This invention advances the development and practical application of ferrous oxalate in the field of lithium-ion battery anode materials. Attached Figure Description
[0011] Figure 1 This is a schematic diagram of the process of this invention;
[0012] Figure 2 In the image, ab is a magnified scanning electron microscope image of the original ferrous oxalate particles, and cd is a magnified scanning electron microscope image of the ferrous oxalate / lithium stearate composite material prepared in Example 2 of this invention.
[0013] Figure 3 In the image, ab is a transmission electron microscope (TEM) image of the original ferrous oxalate particles, and cd is a TEM image of the stable rod-shaped ferrous oxalate / lithium stearate composite material prepared in Example 2 of this invention.
[0014] Figure 4 This is a rate cycling comparison diagram of the stable rod-shaped ferrous oxalate / lithium stearate composite material prepared in Examples 1-4 of this invention and the original ferrous oxalate anode material.
[0015] Figure 5 This is a comparison of charge-discharge cycles of the stable rod-shaped ferrous oxalate / lithium stearate composite material prepared in Examples 1-4 of this invention and the original ferrous oxalate anode material. Detailed Implementation
[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0017] like Figure 1 As shown, the specific steps for preparing this stable rod-shaped ferrous oxalate / lithium stearate composite material are as follows:
[0018] Example 1:
[0019] Step 1: Add ferrous sulfate solution to oxalic acid dissolved in ethanol, age in a reaction vessel at 60°C for 12 hours, filter, wash and dry to obtain ferrous oxalate dihydrate precursor;
[0020] Step 2: Place an appropriate amount of ferrous oxalate dihydrate and lithium stearate with a mass fraction of 1% in a planetary ball mill and grind them thoroughly at a speed of 2500 r / min for 2 hours.
[0021] Step 3: The mixed precursor obtained in Step 2 is subjected to a first-stage calcination under an inert atmosphere (argon or nitrogen) with a heating rate of 5℃ / min, a calcination temperature of 240℃, and a holding time of 1h. Then, a second-stage calcination is carried out with a calcination temperature of 290℃ and a holding time of 2h to obtain the ferrous oxalate / lithium stearate composite anode material.
[0022] The rate performance of the ferrous oxalate / lithium stearate (1% by mass) composite material obtained in this embodiment in the lithium-ion battery system is shown in the figure below. Figure 4 As shown (lithium stearate additive in) Figure 4 (hereinafter referred to as LS in 5), the composite material obtained in this embodiment has good rate performance, which is good at 0.1, 0.5, 1, 2, 3 and 5 Ag. -1 The specific discharge capacities at the following values were 921.7, 792.4, 658.1, 531.8, 465.1, and 520 mAh g, respectively. -1 The efficiency was higher than that of the original ferrous oxalate anode material at the corresponding currents of 869, 801, 715, 619, 572 and 384.4 mAh g⁻¹. -1 Rate performance; from Figure 5 As can be seen from the data, this composite material exhibits good cycle performance as a negative electrode material for lithium-ion batteries, at 3A g. -1 After 300 charge-discharge cycles, it still has 918 mAh g. -1 The discharge specific capacity is higher, while the original ferrous oxalate anode material has a discharge specific capacity of only 712 mAh g. -1 The specific discharge capacity.
[0023] Example 2:
[0024] Step 1: Add ferrous sulfate solution to oxalic acid dissolved in ethanol, age in a reaction vessel at 60°C for 12 hours, filter, wash and dry to obtain ferrous oxalate dihydrate precursor;
[0025] Step 2: Place an appropriate amount of ferrous oxalate dihydrate and lithium stearate with a mass fraction of 1% in a planetary ball mill and grind them thoroughly at a speed of 2500 r / min for 2 hours.
[0026] Step 3: The mixed precursor obtained in Step 2 is subjected to a first-stage calcination under an inert atmosphere (argon or nitrogen) with a heating rate of 5℃ / min, a calcination temperature of 240℃, and a holding time of 1h. Then, a second-stage calcination is carried out with a calcination temperature of 290℃ and a holding time of 2h to obtain the ferrous oxalate / lithium stearate composite anode material.
[0027] The rate performance of the ferrous oxalate / lithium stearate (3% by mass) composite material obtained in this embodiment in the lithium-ion battery system is shown in the figure below. Figure 4 As shown, the composite material obtained in this embodiment exhibits better rate performance compared to the original ferrous oxalate anode, at rates of 0.1, 0.5, 1, 2, 3, and 5 A g. -1 The specific discharge capacities at the following values were 912, 853, 780, 711, 694, and 655 mAh g, respectively. -1 This is significantly higher than the rate performance of the original ferrous oxalate anode material at the corresponding currents of 869, 801, 715, 619, 572, and 384.4 mAh g⁻¹; from Figure 5 As can be seen from the data, this composite material exhibits good cycle performance as a negative electrode material for lithium-ion batteries, at 3A g. -1 After 300 charge-discharge cycles, it still has 984 mAh g. -1 The discharge specific capacity is higher, while the original ferrous oxalate anode material has a discharge specific capacity of only 712 mAh g. -1 The specific discharge capacity.
[0028] Example 3
[0029] Step 1: Add ferrous sulfate solution to oxalic acid dissolved in ethanol, age in a reaction vessel at 60°C for 12 hours, filter, wash and dry to obtain ferrous oxalate dihydrate precursor;
[0030] Step 2: Place an appropriate amount of ferrous oxalate dihydrate and lithium stearate with a mass fraction of 1% in a planetary ball mill and grind them thoroughly at a speed of 2500 r / min for 2 hours.
[0031] Step 3: The mixed precursor obtained in Step 2 is subjected to a first-stage calcination under an inert atmosphere (argon or nitrogen) with a heating rate of 5℃ / min, a calcination temperature of 240℃, and a holding time of 1h. Then, a second-stage calcination is carried out with a calcination temperature of 290℃ and a holding time of 2h to obtain the ferrous oxalate / lithium stearate composite anode material.
[0032] The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the original ferrous oxalate anode material and the ferrous oxalate / lithium stearate (5% by mass) composite material prepared in this embodiment are shown below. Figure 2 As shown in Figure 3, the surface morphology of the original ferrous oxalate anode and the ferrous oxalate / lithium stearate material can be clearly seen. The morphology of the ferrous oxalate / lithium stearate (5% by mass) is smoother and more complete than that of the original ferrous oxalate particles, with fewer defects. Figure 3 A comparison of the microstructures of the two materials revealed that the ferrous oxalate composite material exhibits a stable rod-like structure without particle breakage or pulverization. This provides a more stable lithium-ion diffusion channel during subsequent charge and discharge processes, facilitating faster lithium-ion transport and improving the overall electrochemical performance of the battery. Figure 4 The rate performance of the composite material in the lithium-ion battery system can be seen from the data. The composite material obtained in this embodiment has good rate performance at 0.1, 0.5, 1, 2, 3 and 5 A g. -1 The specific discharge capacities at the following values were 1016, 936, 869, 787, 749, and 680 mAh g, respectively. -1 This is significantly higher than the original ferrous oxalate anode material at the corresponding currents of 869, 801, 715, 619, 572, and 384.4 mAhg. -1 Rate performance; from Figure 5 As can be seen from the data, this composite material exhibits the best cycle performance as a lithium-ion battery anode material compared to other materials, at 3A g. -1 After 300 charge-discharge cycles, it still has 1123 mAh g. -1 The discharge specific capacity is higher, while the original ferrous oxalate anode material has a discharge specific capacity of only 712 mAh g. -1 The specific discharge capacity.
[0033] Example 4
[0034] Step 1: Add ferrous sulfate solution to oxalic acid solution dissolved in ethanol, age in a reaction vessel at 60°C for 12 hours, filter, wash and dry to obtain ferrous oxalate dihydrate precursor;
[0035] Step 2: Place an appropriate amount of ferrous oxalate dihydrate and lithium stearate with a mass fraction of 1% in a planetary ball mill and grind them thoroughly at a speed of 2500 r / min for 2 hours.
[0036] Step 3: The mixed precursor obtained in Step 2 is subjected to a first-stage calcination under an inert atmosphere (argon or nitrogen) with a heating rate of 5℃ / min, a calcination temperature of 240℃, and a holding time of 1h. Then, a second-stage calcination is carried out with a calcination temperature of 290℃ and a holding time of 2h to obtain the ferrous oxalate / lithium stearate composite anode material.
[0037] The rate performance of the ferrous oxalate / lithium stearate (7% by mass) composite material obtained in this embodiment in the lithium-ion battery system is shown in the figure below. Figure 4 As shown, its values at 0.1, 0.5, 1, 2, 3, and 5 Ag were [values missing]. -1 The specific discharge capacities at the following values were 989, 926, 861, 777, 732, and 695 mAh g, respectively. -1 The efficiency was higher than that of the original ferrous oxalate anode material at the corresponding currents of 869, 801, 715, 619, 572 and 384.4 mAh g⁻¹. -1 Rate performance; from Figure 5 As can be seen from the data, this composite material exhibits good cycle performance as a negative electrode material for lithium-ion batteries, at 3A g. -1 After 300 charge-discharge cycles, it still has 1120 mAh g. -1 The discharge specific capacity is higher, while the original ferrous oxalate anode material has a discharge specific capacity of only 712 mAh g. -1 The specific discharge capacity.
[0038] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.
Claims
1. A method for preparing a ferrous oxalate / lithium stearate composite anode material, the specific steps of which are as follows: Step (1): Add ferrous sulfate solution to oxalic acid dissolved in ethanol, age in a reaction vessel at 60°C for 12 hours, filter, wash and dry to obtain ferrous oxalate dihydrate precursor; Step (2): Place an appropriate amount of ferrous oxalate dihydrate precursor and lithium stearate in a planetary ball mill and grind them thoroughly. The speed is 2500 r / min and the grinding time is 2h to obtain a mixed precursor. The mass ratio of ferrous oxalate dihydrate precursor to lithium stearate is 100:1~7. Step (3): The mixed precursor obtained in step (2) is subjected to a first-stage calcination under an inert atmosphere, with a heating rate of 5℃ / min, a calcination temperature of 220~240℃, and a holding time of 1h; then the calcination temperature is controlled at 290~300℃ and the holding time is 2h for a second-stage calcination to obtain the ferrous oxalate / lithium stearate composite anode material.
2. The preparation method of the ferrous oxalate / lithium stearate composite anode material according to claim 1, characterized in that: The first-stage roasting temperature in step (3) is 240°C, and the second-stage roasting temperature is 290°C.
3. The preparation method of the ferrous oxalate / lithium stearate composite anode material according to claim 1, characterized in that: The inert atmosphere gas in step (3) is argon or nitrogen.
4. A composite anode material of ferrous oxalate / lithium stearate prepared by the preparation method according to any one of claims 1 to 3.