Flower-like iron fluoride nanosheet assembled high-performance lithium battery cathode material and application thereof
By preparing nanosheets to assemble flower-like iron fluoride materials, the problems of low capacity and poor cycle stability of lithium-ion battery cathode materials were solved, achieving high capacity and good cycle performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF NEW MATERIALS & IND TECH WENZHOU UNIV
- Filing Date
- 2023-11-20
- Publication Date
- 2026-07-07
AI Technical Summary
Existing lithium-ion battery cathode materials have low capacity, poor conductivity, and rapid capacity decay during cycling. Furthermore, there is an undesirable interaction between the electrolyte and the metal fluoride cathode, leading to increased battery resistance and structural changes.
A flower-like structure of fluoride material assembled from nanosheets was prepared by synthesizing the precursor via a solvothermal method and then carbonizing and fluorinating it at high temperature. This produced a morphologically regular and uniformly sized flower-like fluoride material assembled from nanosheets. The material was then combined with conductive agents and binders to prepare lithium-ion batteries.
It improves the capacity and cycle stability of lithium-ion batteries, shortens the diffusion distance of lithium ions, enhances conductivity, and achieves high-performance lithium storage.
Smart Images
Figure CN117682564B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrode material technology, specifically relating to a high-performance lithium storage material and battery made of nanosheet-assembled flower-shaped iron fluoride. Background Technology
[0002] For decades, lithium-ion batteries (LIBs) have been widely used for energy supply and storage in portable electronic devices due to their high energy density, high operating voltage, and long lifespan. However, with the continuous development of the smart grid era, there is an urgent need for electrode materials with higher capacity and power density to provide higher energy to meet people's needs. Although researchers have conducted extensive research and development on anode materials for lithium-ion batteries in the past decade, research on cathode materials has been minimal. Currently, the cathode materials for commercially available lithium-ion batteries are mainly intercalated compounds such as lithium cobalt oxide (LiCoO2) and lithium iron phosphate (LiFePO4), with capacities of 150 and 170 mAh g, respectively. -1 .
[0003] Due to the electrode capacity and the Li transferred during the electrochemical reaction... + Regarding the amount of Li that can be stored per 1 mol of metal ions based on the intercalation mechanism. + Since the number of electrons in a lithium-ion battery is less than 1 mol, the theoretical capacity provided is relatively small. Therefore, to improve the capacity of lithium-ion batteries, researchers have turned their attention to conversion compounds with multi-electron conversion mechanisms, mainly including chalcogenide elements and their compounds, as well as halides. Among them, transition metal fluorides (such as FeF3, CuF2, CoF2, NiF2, etc.) can be used as positive electrode materials for lithium batteries due to the high potential brought about by the strong ionicity of the MF bond. Iron-based fluorides, such as ferrous fluoride (FeF2~571 mAhg), can also be used. -1 ) and ferric fluoride (FeF3~712 mAh g) -1 Due to its advantages such as high theoretical capacity, low cost, abundant resources, and environmental friendliness, it has attracted widespread attention.
[0004] Iron fluoride, as a member of iron-based fluorides, is considered a promising alternative cathode material due to its unique tunnel structure. Studies have shown that trace water molecules at the center of one-dimensional tunneled open-framework iron fluoride compounds help improve conductivity and promote Li... +Diffusion and structural stabilization are important factors. However, the lithium storage performance of iron fluoride still falls short of application requirements. This is mainly because the strong ionicity between the MF bonds results in a large band gap, leading to poor conductivity in transition metal fluorides. Furthermore, during cycling, the poor interaction between the electrolyte and the metal fluoride cathode increases battery resistance and promotes Fe degradation and dissolution, resulting in rapid capacity decay and irreversible structural changes. Simultaneously, the separation of the Fe and LiF phases during cycling can also lead to capacity decay and increased battery polarization. Current methods for improving the electrochemical performance of metal fluorides mainly include the following:
[0005] I. Nanoscale Material Size. By reducing the size of iron fluoride particles, the electron and lithium-ion transport paths can be effectively shortened, thereby improving the electrochemical performance of iron fluoride cathode materials. Chen et al. prepared self-assembled octagonal wafer-like iron fluoride using a liquid-phase method. The preferentially oriented, multi-layered microstructures can shorten the ion transport path and promote electron transfer. After 100 cycles at 0.1C, the capacity remained at 172 mAh g⁻¹. -1 Lin et al. prepared layered iron fluoride nanoparticles using a soft template method, achieving a yield of 23.7 mA g⁻¹. -1 After 100 cycles at the current density, it still has 236.6 mAh g⁻¹. -1 Zeng et al. synthesized layered iron fluoride nanospheres using a one-step hydrothermal method with the aid of different surfactants. The layered structure increased the contact area between the active material and the electrolyte, and the capacity remained at 109.4 mAh g after 100 cycles at 1C. -1 .
[0006] II. Composite Conductive Materials. Combining fluorides with various conductive materials such as carbonaceous materials, metal oxides, and conductive polymers can effectively improve the inherent poor electronic conductivity and large voltage hysteresis of fluorides. Yang et al. prepared iron fluoride materials encapsulated in nano-carbon cages using Fe(NO3)3•9H2O and glucose via a hydrothermal method. The structure of the nano-carbon cages effectively suppressed the volume expansion of FeF3 during the conversion reaction, while also playing a role in electronic conduction. At 100 mAg... -1 After 120 cycles at current density, it still has 410 mAh g. -1 The material exhibits excellent cycling stability. Kitajou et al. prepared a novel FeF3-V2O5 material using a high-temperature solid-state method and ball milling process. Compared with FeF3, it has a lower overpotential, better cycling performance, and higher rate performance. Furthermore, the addition of LiF compensates for irreversible reactions during cycling. After 30 cycles at 0.5C, it still retains 478 mAh g⁻¹.-1 The capacity.
[0007] III. Doping Improves Band Gap and Enhances Conductivity. Fe was prepared by mechanical ball milling. 1-x Co x F3 nanocomposite material, with the addition of acetylene black, further improved Fe 1-x Co x Electrochemical reversibility of F3 materials (x = 0, 0.03, 0.05, and 0.07). Introducing Co... 2+ Subsequently, its electrochemical performance was significantly improved, with discharge capacities of 150, 140, and 125 mA hg at 1, 2, and 5C rates, respectively. -1 After 100 cycles, the capacity retention rates reached 92.0%, 92.2%, and 91.7%, respectively. Zhang et al. doped FeF3 in LIBs with Co. Co doping successfully formed Co in a hexagonal tungsten bronze structure. x Fe 1-x The F3 system (x = 0.08, 0.17, or 0.25). Studies have shown that the band structure drops sharply after Co doping, which may be due to the Co nanosheet assembly hybridization energy levels between the conduction and valence bands.
[0008] IV. Electrolyte Optimization. When testing the electrochemical performance of fluoride cathode materials using traditional electrolytes, it was found that their specific capacity still differed significantly from the theoretical value, and their cycle performance was poor. This was due to significant side reactions and dissolution of active materials during cycling, leading to the consumption of organic electrolyte and a continuous increase in the thickness of the solid ion interface layer on the electrode surface. To overcome the problem of active material dissolution in fluoride cathodes, researchers developed novel electrolytes suitable for fluorides based on material design, improving the reaction environment and significantly enhancing their electrochemical performance. Gu et al. discovered that the lithium difluorosulfonylimide and 1,2-dimethoxyethane (LiFSI-DME) electrolyte system forms a solid electrolyte layer capable of transporting lithium ions in situ on the FeF2 cathode, effectively limiting the dissolution of active materials. This protective layer was formed at 4.6 mol L... -1 The redox reaction of the electrolyte during the first charge-discharge cycle induced by a high-concentration electrolyte resulted in a reduction of capacity loss during cycling and suppression of lithium dendrite growth. Huang et al. systematically investigated the lithium salt composition (LiPF6, LiFSI, and LiTFSI) and lithium salt concentration (1.0, 2.0, and 3.0 mol·L⁻¹). -1 The effects of solvent composition (FEC-EMC and DME) and cycling voltage range on the FeF2 cathode were investigated, revealing that FeF2 at 3 mol·L⁻¹ -1LiFSI exhibits optimal performance in DME solution, retaining a capacity of 400 mAh g after 100 charge-discharge cycles. -1 With a coulombic efficiency close to 100%, a stable solid electrolyte layer can be effectively formed under these conditions, limiting the dissolution of active substances.
[0009] In summary, designing synthetic methods to control the structural composition of iron fluoride materials is the most effective and crucial strategy for improving their performance as cathode materials in lithium-ion batteries. Summary of the Invention
[0010] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a high-performance lithium storage cathode material and lithium battery with nanosheet-assembled flower-shaped iron fluoride.
[0011] The technical solution adopted in this invention is as follows: A high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride, the preparation method of which includes the following steps:
[0012] S1: Dissolve anhydrous ferric chloride and urea in ethylene glycol in a certain proportion to obtain a reaction solution. Place the reaction solution in a reaction vessel and react at an appropriate temperature for a period of time.
[0013] S2: After the reaction in step S1 is completed, the pressure is released to normal pressure and the mixture is allowed to cool naturally to room temperature. The resulting solid is then washed and vacuum dried to obtain a dry sample.
[0014] S3: The dried sample obtained in step S2 is subjected to high-temperature treatment under inert gas protection to obtain iron(III) oxide composite carbon material.
[0015] S4: Fluoride the iron oxide composite carbon material obtained in step S3 using a fluorine source to obtain a high-performance lithium storage cathode material with nanosheet-assembled flower-shaped iron fluoride.
[0016] Preferably, the molar ratio of urea to anhydrous ferric chloride in step S1 is 4-15:1.
[0017] Preferably, in step S1, the reactor is placed in an oven, the oven is set to a reaction temperature of 120~220℃, and the reaction time is 4~16h.
[0018] Preferably, the high-temperature treatment temperature in step S3 is 300-700℃, and most preferably 500℃.
[0019] Preferably, in step S4, the fluorine source used is one of hydrogen fluoride solution, ammonium fluoride and ammonium hydrogen fluoride, with ammonium fluoride being the most preferred.
[0020] Preferably, in step S4, the mass ratio of ammonium fluoride to iron oxide composite carbon is 1-4:1, with the most preferred ratio being 2:1.
[0021] Preferably, in step S4, the fluorination temperature is 220-320°C, and most preferably 270°C.
[0022] The present invention also provides the application of lithium-ion batteries assembled with the above-mentioned nanosheet-assembled flower-shaped iron fluoride cathode material.
[0023] Preferably, the method for preparing the lithium-ion battery includes the following steps:
[0024] (A) Using the above-mentioned nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage material as the positive electrode material, weigh the nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil.
[0025] (B) The aluminum foil coated with the positive electrode material is dried, sliced, assembled, and pressed to obtain the lithium-ion battery.
[0026] The beneficial effects of the present invention are as follows: The present invention uses a simple solvothermal method, with ethylene glycol as solvent, and a certain amount of anhydrous ferric chloride and urea as raw materials to synthesize a precursor at a certain temperature, and then synthesizes a high-performance lithium storage material with nanosheet-assembled flower-like ferric fluoride through high-temperature carbonization and fluorination.
[0027] The high-performance lithium-ion cathode material with nanosheet-assembled flower-like iron fluoride prepared by this invention has a regular morphology, uniform size, and uniform particle size distribution. Compared with existing reports, the method of this invention is simple and easy to control, non-toxic and harmless, and easier to mass-produce and promote. Moreover, the nanosheet-assembled flower-like structure constructed from nanosheets not only provides abundant lithium-ion active sites, but also shortens the diffusion distance of lithium ions and improves the bulk transport capability of ions, so that the high-performance lithium-ion cathode material with nanosheet-assembled flower-like iron fluoride has higher capacity and better cycle stability.
[0028] In some embodiments of the present invention, at 100 mA g -1 At the specified current density, the battery capacity stabilized at 173.1 mAh g after 70 charge-discharge cycles. -1 Even in 1 Ag -1 Under high current density, the capacity remains stable at 144.8 mAh g after 100 charge-discharge cycles. -1 . Attached Figure Description
[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.
[0030] Figure 1 (a) is a scanning electron microscope (SEM) image of the nanosheet-assembled flower-shaped high-performance lithium fluoride cathode material prepared in Example 1; (b) is a SEM image of the lithium fluoride cathode material prepared in Comparative Example 3; (c) is a SEM image of the lithium fluoride cathode material prepared in Comparative Example 4.
[0031] Figure 2 (a) is a SEM image of the lithium iron fluoride cathode material prepared in Comparative Example 1; (b) is a SEM image of the lithium iron fluoride cathode material prepared in Comparative Example 2.
[0032] Figure 3 The X-ray diffraction patterns are shown for the lithium iron fluoride cathode materials prepared in Examples 1, 1, and 2 of this invention.
[0033] Figure 4 The lithium iron fluoride cathode materials prepared in Examples 1, 1, 2, 3, and 4 of this invention were tested at 100 mA g. -1 Cyclic stability test results at current density;
[0034] Figure 5 The lithium iron fluoride cathode materials prepared in Examples 1, 1, 2, 3, and 4 of this invention were tested at 1000 mA g. -1 Cyclic stability test results at current density;
[0035] Figure 6 The graphs show the rate cycling performance of lithium iron fluoride cathode materials prepared in Examples 1, 1, 2, 3 and 4 of this invention at different current densities.
[0036] Figure 7 The nanosheet-assembled flower-like high-performance lithium-ion cathode material prepared in Example 1 of this invention was tested at 100 mA g. -1 Charge-discharge curves under current. Detailed Implementation
[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.
[0038] A high-performance lithium-ion cathode material with nanosheet-assembled flower-like iron fluoride, the preparation method of which includes the following steps:
[0039] Example 1
[0040] S1: Weigh 0.6500g FeCl3 and 1.4424g urea and add them to 70mL ethylene glycol. Mix them evenly by sonication. Place the reaction solution into a reaction vessel and heat it at 180℃ for 10h. Then centrifuge, wash and dry to obtain a light green powder.
[0041] S2: The dried sample is subjected to high-temperature treatment under argon protection to obtain iron oxide composite carbon material; wherein the high-temperature treatment temperature is 500℃ and the treatment time is 2 hours.
[0042] S3: The iron oxide composite carbon material obtained in step S2 is ground and mixed with ammonium fluoride in a mortar at a mass ratio of 1:2. The mixture is then fluorinated at 270°C under argon protection for 2 hours to obtain a high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride.
[0043] S4: Weigh out the nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage cathode material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil; dry, slice, assemble and press the aluminum foil coated with cathode material to obtain a lithium-ion battery.
[0044] Comparative Example 1
[0045] S1: Weigh 0.6500g FeCl3 and 1.4424g urea and add them to 70mL ethylene glycol. Mix them evenly by sonication. Place the reaction solution into a reaction vessel and heat it at 180℃ for 10h. Then centrifuge, wash and dry.
[0046] S2: The dried sample is subjected to high-temperature treatment under argon protection to obtain iron oxide composite carbon material; wherein the high-temperature treatment temperature is 500℃ and the treatment time is 2 hours.
[0047] S3: Place the iron(III) oxide composite carbon material obtained in step S2 into a 15 mL uncovered polytetrafluoroethylene (PTFE) liner. Pour 10 mL of 40 wt% HF solution into a 100 mL PTFE liner and place the PTFE liner inside. React at 110 °C for 4 h. After the reaction vessel cools to room temperature, remove it, wash it three times with anhydrous ethanol, centrifuge, and dry it in a vacuum oven at 60 °C to obtain FeF3·3H2O.
[0048] S4: FeF3·3H2O was placed in a tube furnace and annealed at 225℃ for 10 h at a heating rate of 5℃ / min to remove some of the water of crystallization, thus obtaining iron fluoride lithium storage material.
[0049] S4: Weigh out lithium iron fluoride storage material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil; dry, slice, assemble and press the aluminum foil coated with positive electrode material to obtain a lithium-ion battery.
[0050] Comparative Example 2
[0051] S1: Weigh 0.6500g FeCl3 and 0.4800g sodium hydroxide and add them to 70mL ethylene glycol. Mix them evenly by sonication. Place the reaction solution into a reaction vessel and heat it at 180℃ for 10h. Then centrifuge, wash and dry.
[0052] S2: The dried sample is subjected to high-temperature treatment under argon protection to obtain iron oxide composite carbon material; wherein the high-temperature treatment temperature is 500℃ and the treatment time is 2 hours.
[0053] S3: The iron oxide composite carbon material obtained in step S2 is ground and mixed with ammonium fluoride in a mortar at a mass ratio of 1:2. The mixture is then fluorinated at 270°C under argon protection for 2 hours to obtain iron fluoride lithium storage cathode material.
[0054] S4: Weigh out lithium iron fluoride storage material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil; dry, slice, assemble and press the aluminum foil coated with positive electrode material to obtain a lithium-ion battery.
[0055] Comparative Example 3
[0056] S1: Weigh 1.082g FeCl3·6H2O and 1.4424g urea and add them to 70mL ethylene glycol. Mix them evenly by sonication. Place the reaction solution into a reaction vessel and heat it at 180℃ for 10h. Then centrifuge, wash and dry to obtain a light green powder.
[0057] S2: The dried sample is subjected to high-temperature treatment under argon protection to obtain iron oxide composite carbon material; wherein the high-temperature treatment temperature is 500℃ and the treatment time is 2 hours.
[0058] S3: The iron oxide composite carbon material obtained in step S2 is ground and mixed with ammonium fluoride in a mortar at a mass ratio of 1:2. The mixture is then fluorinated at 270°C under argon protection for 2 hours to obtain iron fluoride lithium storage cathode material.
[0059] S4: Weigh out the lithium iron fluoride cathode material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil; dry, slice, assemble and press the aluminum foil coated with cathode material to obtain a lithium-ion battery.
[0060] Comparative Example 4
[0061] S1: Weigh 1.616g Fe(NO3)3·9H2O and 1.4424g urea and add them to 70mL ethylene glycol. Mix them evenly by sonication. Place the reaction solution into a reaction vessel and heat it at 180℃ for 10h. Then centrifuge, wash and dry to obtain a brownish-yellow powder.
[0062] S2: The dried sample is subjected to high-temperature treatment under argon protection to obtain iron oxide composite carbon material; wherein the high-temperature treatment temperature is 500℃ and the treatment time is 2 hours.
[0063] S3: The iron oxide composite carbon material obtained in step S2 is ground and mixed with ammonium fluoride in a mortar at a mass ratio of 1:2. The mixture is then fluorinated at 270°C under argon protection for 2 hours to obtain iron fluoride lithium storage cathode material.
[0064] S4: Weigh out lithium iron fluoride storage material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil; dry, slice, assemble and press the aluminum foil coated with positive electrode material to obtain a lithium-ion battery.
[0065] Microscopic characterization
[0066] Figure 1 The images in 'ac' correspond to the SEM images of the products synthesized in Example 1 and Comparative Examples 3 and 4, respectively. It can be seen that the product synthesized in Example 1 using FeCl3 as the iron source presents as flower-shaped iron fluoride composed of nanosheets with a size of about 3~4 μm. The product synthesized in Comparative Example 3 using FeCl3·6H2O as the iron source presents as a stack of two-dimensional nanosheets. The product synthesized in Comparative Example 4 using Fe(NO3)3·9H2O as the iron source presents as a micron-sized block.
[0067] Figure 2 In Figures a and b, SEM images of the products synthesized in Comparative Example 1 and Comparative Example 2 are compared. It can be seen that the product synthesized in Comparative Example 1 without urea exhibits nanoparticle aggregates, while the product synthesized in Comparative Example 2 with HF as the fluorine source exhibits micron-sized bulk particles.
[0068] Figure 3The XRD diffraction results of the products synthesized in Example 1, Comparative Example 1 and Comparative Example 2 are shown in the comparison diagram with the standard data of iron fluoride crystals (JCPDS 76-1265). It can be seen that the iron fluoride obtained by fluorination with NH4F is pure and has good crystallinity, while the iron fluoride obtained by fluorination with HF has poor crystallinity.
[0069] Electrochemical performance characterization
[0070] Figure 4-5 A comparison of the electrochemical performance of the products synthesized in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 shows that the nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage cathode material exhibits higher capacity and better cycle stability. The nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage cathode material prepared in Example 1 achieves high capacity and better cycle stability in the 2–4.5 V voltage range at 100 mA g / L. -1 At the specified current density, the battery capacity after 70 charge-discharge cycles is 173.1 mAh g. -1 In contrast, the iron fluoride synthesized using sodium hydroxide as a precipitant in Comparative Example 1 was at 100 mA g. -1 At the specified current density, the battery capacity after 100 charge-discharge cycles is 61.5 mAh g. -1 In Comparative Example 2, the iron fluoride obtained by HF fluorination had a high initial capacity, reaching 213.6 mAh g. -1 However, its capacity decays relatively quickly, with a discharge capacity of 126.3 mAh g after 70 cycles. -1 In Comparative Example 3, the capacity of the two-dimensional sheet-like iron fluoride synthesized using ferric chloride hexahydrate as the iron source after 70 cycles was 148 mAh g. -1 The capacity of the blocky ferric fluoride synthesized in Comparative Example 4 using ferric nitrate nonahydrate as the iron source after 70 cycles was 118 mAh g, which is lower than that of the flower-shaped ferric fluoride. -1 Even at 1000 mAg -1 At the current density, after 100 cycles, it still has 144.8 mAh g⁻¹. -1 The reversible capacity, while the iron fluoride synthesized in Comparative Example 1 using sodium hydroxide as a precipitant, has a capacity of 1000 mA g. -1 At the current density, the capacity rapidly decays to 53 mAhg after 100 charge-discharge cycles. -1 In Comparative Example 2, iron fluoride obtained by fluorination with HF was at 1000 mA g. -1 At the current density, the discharge capacity after 100 cycles is 112 mAh g. -1 After 100 cycles, the iron fluoride synthesized in Comparative Examples 3 and 4 had capacities of 114 and 87 mAh g, respectively. -1
[0071] As can be seen from Figure 6, the nanosheet-assembled flower-like iron fluoride high-performance lithium storage cathode material prepared in Example 1 exhibits high performance at 100, 200, 500, 1000, and 2000 mA g. -1 They have 177, 172, 163, 154, and 142 mAh g, respectively. -1 The reversible capacity, even at 2000 mA g -1 Even at high current densities, it still maintains an 80.2% capacity retention rate, and when the current returns to 100 mA g... -1 At that time, it had 180 mAh g -1 Reversible capacity.
[0072] from Figure 7 As can be seen from the data, the nanosheet-assembled flower-like iron fluoride high-performance lithium storage cathode material prepared in Example 1 exhibits high performance at 100 mA g / L. -1 During current charging and discharging, the charging and discharging platform is stable, and the charging and discharging curves show a high degree of overlap, demonstrating excellent cycle stability.
[0073] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.
Claims
1. A high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride, characterized in that... The preparation method includes the following steps: S1: Dissolve anhydrous ferric chloride and urea in ethylene glycol in a certain proportion to obtain a reaction solution. Place the reaction solution in a reaction vessel and heat it to 150-220℃ to carry out the reaction. S2: After the reaction in step S1 is completed, the pressure is released to normal pressure and the mixture is allowed to cool naturally to room temperature. The resulting solid is then washed and vacuum dried to obtain a dry sample. S3: The dried sample obtained in step S2 is heated to 400-700℃ under inert gas protection for high-temperature treatment to obtain iron oxide composite carbon material; S4: Fluoride the iron oxide composite carbon material obtained in step S3 using a fluorine source to obtain a nanosheet-assembled flower-shaped iron fluoride lithium storage cathode material.
2. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 1, characterized in that: In step S1, the molar ratio of urea to anhydrous ferric chloride is 4-10:
1.
3. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 2, characterized in that: In step S1, the molar ratio of urea to anhydrous ferric chloride is 6:
1.
4. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 1, characterized in that: In step S3, the temperature of the high-temperature treatment is 500°C.
5. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 1, characterized in that: In step S4, the fluorine source used is one of hydrogen fluoride solution, ammonium fluoride, and ammonium hydrogen fluoride.
6. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 5, characterized in that: In step S4, the fluorine source used is ammonium fluoride.
7. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 6, characterized in that: In step S4, the mass ratio of ammonium fluoride to iron oxide composite carbon is 1-4:
1.
8. The high-performance lithium storage cathode material with nanosheet-assembled flower-like iron fluoride as described in claim 1, characterized in that: In step S4, the fluorination temperature is 250-300°C.
9. The application of the nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage cathode material as described in any one of claims 1 to 8 in the preparation of lithium-ion batteries.
10. The application according to claim 9, characterized in that: The method for preparing the lithium-ion battery includes the following steps: (A) Using the nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage cathode material as described in any one of claims 1 to 8 as the cathode material, weigh the nanosheet-assembled flower-shaped iron fluoride high-performance lithium storage cathode material, Ketjen black and polyvinylidene fluoride, add an appropriate amount of N-methylpyrrolidone, mix evenly, grind and stir into a paste, and coat it onto aluminum foil. (B) The aluminum foil coated with the positive electrode material is dried, sliced, assembled, and pressed to obtain the lithium-ion battery.