Preparation method and application of FeMnHCF-FeMnNiHCF sodium ion battery positive electrode material
By using the FeMnHCF@FeMnNiHCF core-shell structure and Ni doping, the structural collapse problem of iron-manganese-based Prussian blue sodium-ion battery cathode material was solved, achieving high discharge specific capacity and good cycle stability, thus improving the electrochemical performance of sodium-ion batteries.
Patent Information
- Application Number
- CN202510939602.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-08
- Publication Date
- 2025-10-31
AI Technical Summary
Existing iron-manganese-based Prussian blue sodium-ion battery cathode materials suffer from disordered distribution of crystal water and vacancies, poor electronic conductivity, and the Jahn-Teller effect with Mn content. This leads to lattice distortion or structural collapse during sodium ion insertion/extraction, resulting in rapid capacity decay and poor battery performance.
A core-shell structure design with FeMnHCF as the core and FeMnNiHCF as the shell is adopted. By doping with Ni, FeMnHCF@FeMnNiHCF sodium-ion battery cathode material is formed. The Jahn-Teller effect of Mn is suppressed and structural collapse is reduced by utilizing the dual mechanism of core-shell separation and Ni doping.
The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material achieved good rate performance and long cycle life, with high specific capacity in the first discharge cycle, good cycle stability, and 80% specific capacity retention after 1300 cycles.
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Abstract
Description
Technical Field
[0001] The present invention relates to a preparation method and application of a FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, belonging to the technical field of sodium-ion batteries. Background Art
[0002] Compared with other sodium-ion battery (SIB) cathode materials (such as layered oxides and polyanionic compounds), Prussian blue analogues (PBAs) have open three-dimensional channels and face-centered cubic structures. Due to their advantages such as high specific capacity, stable electrochemical performance, environmental friendliness, and low cost, PBAs are considered to be promising energy storage cathode materials. The molecular formula of PBA is usually Na x M[Fe(CN)6] 1-y O y nH2O (0 < x < 2, 0 < y < 1), where M is a transition metal element, such as Fe, Mn, Co, Ni, and Cu, O represents the vacancy of [Fe(CN)6]. When M is FeMn, it is usually called iron manganese hexacyanoferrate (FeMnHCF). However, this material has problems such as disordered distribution of crystal water and vacancies, poor electronic conductivity, and the Mn-containing Jahn-Teller effect inside, resulting in lattice distortion or structural collapse during sodium ion deintercalation and intercalation, and thus causing rapid capacity decay, poor battery rate performance and cycle life.
[0003] Therefore, it is of great significance to optimize the synthesis process of the iron manganese-based Prussian blue sodium-ion battery cathode material to improve its electrochemical performance. Summary of the Invention
[0004] Aiming at the problems of the existing iron manganese-based Prussian blue sodium-ion battery cathode material, such as disordered distribution of crystal water and vacancies, poor electronic conductivity, and the Mn-containing Jahn-Teller effect, the present invention proposes a preparation method and application of a FeMnHCF@FeMnNiHCF sodium-ion battery cathode material with FeMnHCF as the core and FeMnNiHCF as the shell. The present invention utilizes the dual action mechanisms of core-shell separation and Ni doping to effectively inhibit the Jahn-Teller effect of Mn and reduce the structural collapse problem of iron manganese hexacyanoferrate (FeMnHCF) during repeated sodium ion deintercalation and intercalation in the charge and discharge process. Thus, the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material obtained has good rate performance and long cycle life.
[0005] A preparation method of a FeMnHCF@FeMnNiHCF sodium-ion battery cathode material is as follows: (1) Dissolve FeSO4·7H2O, MnSO4·H2O and sodium citrate in deionized water to obtain solution A; dissolve C6FeN6·4Na·10H2O in deionized water to obtain solution B; (2) At room temperature, solution A is added dropwise to solution B and stirred for 12-36 hours, then allowed to stand and age for 12-24 hours to obtain solution C; (3) Dissolve MnSO4·H2O, FeSO4·7H2O, NiSO4·6H2O and sodium citrate in deionized water to obtain solution D; dissolve C6FeN6·4Na·10H2O in deionized water to obtain solution F; (4) At room temperature, solution D and solution F were added dropwise to solution C and stirred for 12-24 h. Then, the mixture was allowed to stand for 12-36 h and dried under vacuum to obtain FeMnHCF@FeMnNiHCF sodium-ion battery cathode material.
[0006] Preferably, the solid-liquid ratio of FeSO4·7H2O, MnSO4·H2O, sodium citrate, and deionized water in step (1) is 0.6~10:0.6~1:1~15:30~100.
[0007] Preferably, the molar concentration of C6FeN6·4Na in solution B in step (1) is 10~150 mol / L.
[0008] Preferably, the dropping rate of solution A in step (2) is 0.33~1.6 ml·min. -1 The volume ratio of solution A to solution B is 0.5 to 1:1.
[0009] Preferably, the solid-liquid ratio (mmol:mmol:mmol:ml) of MnSO4·H2O, FeSO4·7H2O, NiSO4·6H2O, sodium citrate and deionized water in step (3) is 0.6~10:0.6~1:0.6~1:1~15:30~100.
[0010] Preferably, the molar concentration of C6FeN6·4Na in solution F is 10~150 mol / L.
[0011] Preferably, in step (4), the dropping rate of solution D and solution F is 0.33~1.6 ml·min. -1 The volume ratio of solutions D, F and C is 0.5~1:0.5~1:1.
[0012] Application of FeMnHCF@FeMnNiHCF sodium-ion battery cathode material as positive electrode active material in the preparation of sodium-ion battery cathode: FeMnHCF@FeMnNiHCF sodium-ion battery cathode material is used as positive electrode active material. After the positive electrode active material, conductive agent and binder are mixed evenly, the mixture is coated on the surface of the positive electrode current collector aluminum foil to form the positive electrode material active layer.
[0013] Preferably, the present invention assembles the sodium-ion battery positive electrode, sodium-ion battery negative electrode (sodium sheet), separator (glass fiber (Whatman, GF / A)) and electrolyte (1M NaClO4 solution of ethylene carbonate and diethyl carbonate (v / v=1:1) with 5% fluoroethylene carbonate as electrolyte) into a sodium-ion battery.
[0014] The beneficial effects of this invention are: (1) The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of the present invention also has a face-centered cubic PBA crystal structure. The face-centered cubic PBA crystal structure forms a three-dimensional rigid framework with open ion channels and spacious interstitial spaces, which can accommodate larger alkali metal cations (such as Na+). + K + ); (2) The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of the present invention has a core-shell double-layer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of iron-manganese-based ferricyanide (FeMnHCF) during repeated sodium ion insertion and extraction during charging and discharging. As a cathode material of sodium-ion battery, it has good rate performance and long cycle life. (3) The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of the present invention not only exhibits high discharge specific capacity in the first cycle, but also has relatively good cycle stability, at 1Ag -1 After 1300 cycles at a current density, the discharge specific capacity still remains at 50.9 mAh g. -1 The discharge specific capacity retention rate reaches 80%. Attached Figure Description
[0015] Figure 1 The XRD pattern of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in Example 3 is shown. Figure 2 This is a SEM image of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material from Example 3. Figure 3 The CV curve of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in Example 3 is shown. Figure 4The charge-discharge curves of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in Example 3 are shown at room temperature. Figure 5 Cycling performance curves of sodium-ion batteries prepared using FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in Example 3 at different rates; Figure 6 The constant current cycling performance curve of the sodium-ion battery prepared using the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of Example 3 at room temperature. Detailed Implementation
[0016] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.
[0017] Example 1: A method for preparing FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, the specific steps of which are as follows: (1) Dissolve 1 mmol MnSO4·H2O, 1 mmol FeSO4·7H2O and 5 mmol sodium citrate in 50 mL of deionized water to obtain solution A; dissolve 7 mmol C6FeN6·4Na·10H2O in 50 mL of deionized water to obtain solution B; (2) At room temperature, solution A is added at a rate of 0.33 mL / min. -1 The solution was added dropwise to solution B and stirred for 12 hours, then allowed to stand and age for 24 hours to obtain solution C; the volume ratio of solution A to solution B was 1:1. (3) Dissolve 1 mmol MnSO4·H2O, 1 mmol FeSO4·7H2O, 1 mmol NiSO4·6H2O, and 5 mmol sodium citrate in 50 mL of deionized water to obtain solution D; dissolve 7 mmol C6FeN6·4Na·10H2O in 50 mL of deionized water to obtain solution F; (4) At room temperature, both solutions D and F were dispensed at a rate of 0.33 mL / min. -1 The solution was added dropwise to solution C and stirred for 12 hours, then allowed to stand for 24 hours. After washing three times with deionized water and twice with anhydrous ethanol, the solution was vacuum dried at 80°C for 12 hours to obtain the sodium-ion battery cathode material Na. 1.15 Fe 0.50 Mn 0.50 [Fe(CN)6]· 3.02 H2O@Na 1.45 Fe 0.33 Mn 0.33 Ni 0.34 [Fe(CN)6]· 2.78H2O (FeMnHCF@FeMnNiHCF sodium-ion battery cathode material); the volume ratio of solution D, solution F and solution C is 1:1:2; The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of this embodiment has a three-dimensional rigid framework structure with open ion channels and spacious interstitial spaces, which can effectively promote sodium ion insertion; it has a core-shell bilayer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of iron-manganese-based ferricyanide (FeMnHCF) during repeated sodium ion insertion and extraction during charging and discharging. The FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material is used as the positive electrode active material to prepare the positive electrode of the sodium-ion battery: using FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material as the positive electrode active material, the positive electrode active material, conductive agent (SP) and binder (PVDF) are mixed evenly in a mass ratio of 7:2:1 and then coated on the surface of the positive electrode current collector aluminum foil to form the positive electrode material active layer; In this embodiment, metallic sodium is used as the negative electrode, glass fiber (Whatman, GF / A) is used as the separator, and the electrolyte is composed of a 1M NaClO4 solution of ethylene carbonate and diethyl carbonate (volume ratio 1:1), with the addition of fluorinated ethylene carbonate (mass concentration of fluorinated ethylene carbonate in the electrolyte is 5%). Aluminum foil is used as the positive electrode current collector, and a 13mm positive electrode material active layer (active components FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material (70wt.%), conductive agent (SP) (20wt.%), binder (PVDF) (10wt.%)) is coated on the surface of the aluminum foil to form a positive electrode sheet, which is then assembled into a button sodium-ion battery to optimize the performance of the iron-manganese-based Prussian blue (FeMnHCF) sodium-ion battery, including improving the battery's energy density, cycle stability, and reaction efficiency. Sodium-ion batteries with 1Ag -1 Cyclic testing was conducted at a current density of approximately 40.6 mAh g. After 1300 cycles, the discharge specific capacity remained at approximately 40.6 mAh g. -1 The specific capacity is high, with a specific capacity retention rate of 71%, and it has good cycle stability. The material has a core-shell double-layer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of FeMnHCF during repeated sodium ion intercalation and deintercalation during charge and discharge. As a positive electrode for sodium-ion batteries, it has good rate performance and long cycle life, thus improving its performance in batteries.
[0018] Example 2: A method for preparing FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, the specific steps of which are as follows: (1) Dissolve 1 mmol MnSO4·H2O, 2 mmol FeSO4·7H2O and 5 mmol sodium citrate in 50 mL of deionized water to obtain solution A; dissolve 7 mmol C6FeN6·4Na·10H2O in 50 mL of deionized water to obtain solution B; (2) At room temperature, solution A is added at a rate of 0.33 mL / min. -1 The solution was added dropwise to solution B and stirred for 12 hours, then allowed to stand and age for 24 hours to obtain solution C; the volume ratio of solution A to solution B was 1:1. (3) Dissolve 1 mmol MnSO4·H2O, 2 mmol FeSO4·7H2O, 1 mmol NiSO4·6H2O, and 5 mmol sodium citrate in 50 mL of deionized water to obtain solution D; dissolve 7 mmol C6FeN6·4Na·10H2O in 50 mL of deionized water to obtain solution F; (4) At room temperature, both solutions D and F were dispensed at a rate of 0.33 mL / min. -1 The solution was added dropwise to solution C and stirred for 12 hours, then allowed to stand for 24 hours. After washing three times with deionized water and twice with anhydrous ethanol, the solution was vacuum dried at 80°C for 14 hours to obtain the sodium-ion battery cathode material Na. 1.15 Fe 0.60 Mn 0.40 [Fe(CN)6]· 3.02 H2O@Na 1.45 Fe 0.33 Mn 0.33 Ni 0.34 [Fe(CN)6]· 2.78 H2O (FeMnHCF@FeMnNiHCF sodium-ion battery cathode material); the volume ratio of solution D, solution F and solution C is 1:1:2; The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of this embodiment has a three-dimensional rigid framework structure with open ion channels and spacious interstitial spaces, which can effectively promote sodium ion insertion; it has a core-shell bilayer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of iron-manganese-based ferricyanide (FeMnHCF) during repeated sodium ion insertion and extraction during charging and discharging. The FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material is used as the positive electrode active material to prepare the positive electrode of the sodium-ion battery: using FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material as the positive electrode active material, the positive electrode active material, conductive agent (SP) and binder (PVDF) are mixed evenly in a mass ratio of 7:2:1 and then coated on the surface of the positive electrode current collector aluminum foil to form the positive electrode material active layer; In this embodiment, metallic sodium is used as the negative electrode, glass fiber (Whatman, GF / A) is used as the separator, and the electrolyte is composed of a 1M NaClO4 solution of ethylene carbonate and diethyl carbonate (volume ratio 1:1), with the addition of fluorinated ethylene carbonate (mass concentration of fluorinated ethylene carbonate in the electrolyte is 5%). Aluminum foil is used as the positive electrode current collector, and a 13mm positive electrode material active layer (active components FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material (70wt.%), conductive agent (SP) (20wt.%), binder (PVDF) (10wt.%)) is coated on the surface of the aluminum foil to form a positive electrode sheet, which is then assembled into a button sodium-ion battery to optimize the performance of the iron-manganese-based Prussian blue (FeMnHCF) sodium-ion battery, including improving the battery's energy density, cycle stability, and reaction efficiency. Sodium-ion batteries with 1Ag -1 Cyclic testing was conducted at a current density of approximately 45.6 mAh g. After 1300 cycles, the discharge specific capacity remained at approximately 45.6 mAh g. -1 The specific capacity is high, with a specific capacity retention rate of 73%, and good cycle stability. The material has a core-shell double-layer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of FeMnHCF during repeated sodium ion intercalation and deintercalation during charge and discharge. As a positive electrode for sodium-ion batteries, it has good rate performance and long cycle life, thus improving its performance in batteries.
[0019] Example 3: A method for preparing FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, the specific steps of which are as follows: (1) Dissolve 3 mmol MnSO4·H2O, 6 mmol FeSO4·7H2O and 10 mmol sodium citrate in 100 mL of deionized water to obtain solution A; dissolve 15 mmol C6FeN6·4Na·10H2O in 100 mL of deionized water to obtain solution B; (2) At room temperature, solution A is added at a rate of 0.55 mL / min. -1 The solution was added dropwise to solution B and stirred for 12 hours, then allowed to stand and age for 36 hours to obtain solution C; the volume ratio of solution A to solution B was 1:1. (3) Dissolve 1 mmol MnSO4·H2O, 3 mmol FeSO4·7H2O, 1 mmol NiSO4·6H2O, and 5 mmol sodium citrate in 50 mL of deionized water to obtain solution D; dissolve 7 mmol C6FeN6·4Na·10H2O in 50 mL of deionized water to obtain solution F; (4) At room temperature, both solution D and solution F are dispensed at a rate of 0.55 mL / min. -1The solution was added dropwise to solution C and stirred for 12 hours, then allowed to stand for 36 hours. After washing three times with deionized water and twice with anhydrous ethanol, the solution was vacuum dried at 80°C for 14 hours to obtain the sodium-ion battery cathode material Na. 1.15 Fe 0.74 Mn 0.26 [Fe(CN)6]· 3.02 H2O@Na 1.45 Fe 0.33 Mn 0.33 Ni 0.34 [Fe(CN)6]· 2.78 H2O (FeMnHCF@FeMnNiHCF sodium-ion battery cathode material); the volume ratio of solution D, solution F and solution C is 1:1:4; The XRD pattern of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in this embodiment is as follows: Figure 1 As shown in the figure, the XRD peaks of this material are quite sharp, indicating that it has high crystallinity and small grain size. The SEM image of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in this embodiment is as follows: Figure 2 As shown in the figure, the material exhibits a three-dimensional block-like stacked structure, and its block-shaped nanoparticles are uniform in size, with a diameter of approximately 15 to 60 nanometers, and the particles are relatively small. The FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material is used as the positive electrode active material to prepare the positive electrode of the sodium-ion battery: using FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material as the positive electrode active material, the positive electrode active material, conductive agent (SP) and binder (PVDF) are mixed evenly in a mass ratio of 7:2:1 and then coated on the surface of the positive electrode current collector aluminum foil to form the positive electrode material active layer; In this embodiment, metallic sodium is used as the negative electrode, glass fiber (Whatman, GF / A) is used as the separator, and the electrolyte is composed of a 1M NaClO4 solution of ethylene carbonate and diethyl carbonate (volume ratio 1:1), with the addition of fluorinated ethylene carbonate (mass concentration of fluorinated ethylene carbonate in the electrolyte is 5%). Aluminum foil is used as the positive electrode current collector, and a 13mm positive electrode material active layer (active components FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material (70wt.%), conductive agent (SP) (20wt.%), binder (PVDF) (10wt.%)) is coated on the surface of the aluminum foil to form a positive electrode sheet, which is then assembled into a button sodium-ion battery to optimize the performance of the iron-manganese-based Prussian blue (FeMnHCF) sodium-ion battery, including improving the battery's energy density, cycle stability, and reaction efficiency. The CV curve of the sodium-ion battery prepared using the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in this embodiment is shown in the figure. Figure 3 ,from Figure 3 It can be seen that within the voltage range of 2~4.2V, at a rate of 0.1mVs -1 Cyclic testing was performed at the scan rate, and two redox peaks appeared at approximately 3.56V / 1.16V and 3.73V / 3.54V. The charge-discharge curves of the sodium-ion battery prepared using the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material in this embodiment at room temperature are shown below. Figure 4 ,from Figure 4 It can be seen that within the voltage window of 2~4.2V, with 20mAg -1 Charge-discharge cycle tests were conducted using current density, and the initial discharge specific capacity reached 89.1 mAh g. -1 The second discharge specific capacity was 87.9 mAhg. -1 The specific capacity during the 7th discharge was 85.4 mAhg. -1 The charging and discharging platform is stable; The constant current cycling performance curves of the sodium-ion battery at different rates at room temperature in this embodiment are shown in the figure. Figure 6 ,from Figure 6 It can be seen that after five consecutive cycles at rates of 1C, 3C, 5C, 10C, and 20C, the corresponding specific capacity is 78.4 mAh g. -1 72.5mAhg -1 69.1mAhg -1 63.4mAhg -1 49.9mAhg -1 When charged and discharged from 20C to 1C again, the discharge specific capacity is 77.9mAhg. -1 The difference is almost the same as before, indicating that this sodium-ion battery cathode material has high rate capability and stable cycle performance. The constant current cycling performance curve of the sodium-ion battery at room temperature in this embodiment is shown in [reference needed]. Figure 6 ,from Figure 6 It can be seen that within the voltage window of 2~4.2V, with 1Ag -1 Cyclic testing was conducted using the current density; during the first cycle, the discharge specific capacity was approximately 60.6 mAh g. -1 During the 7th cycle, the discharge specific capacity decreased slightly to approximately 60.5 mAh g. -1 After 1300 cycles, the discharge specific capacity still remains at approximately 50.9 mAh g. -1 The specific capacity is high, and the specific capacity retention rate reaches 80%, indicating that the sodium-ion battery has good cycle stability and capacity retention performance. Therefore, the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material used in this embodiment not only exhibits high initial discharge specific capacity but also good cycle stability at 1Ag. -1 After 1300 cycles at a current density, the specific capacity remained basically unchanged, with a specific capacity retention rate of 80%. This indicates that the material effectively suppresses the Jahn-Teller effect of Mn, reduces the structural collapse problem of iron-manganese ferricyanide (FeMnHCF) during repeated sodium ion insertion and extraction during charging and discharging, and has good rate performance and long cycle life as a positive electrode for sodium-ion batteries.
[0020] Example 4: A method for preparing FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, the specific steps of which are as follows: (1) Dissolve 2 mmol MnSO4·H2O, 10 mmol FeSO4·7H2O and 10 mmol sodium citrate in 100 mL of deionized water to obtain solution A; dissolve 15 mmol C6FeN6·4Na·10H2O in 100 mL of deionized water to obtain solution B; (2) At room temperature, solution A is added at a rate of 0.55 mL / min. -1 The solution was added dropwise to solution B and stirred for 12 hours, then allowed to stand and age for 36 hours to obtain solution C; the volume ratio of solution A to solution B was 1:1. (3) Dissolve 1 mmol MnSO4·H2O, 3 mmol FeSO4·7H2O, 1 mmol NiSO4·6H2O, and 5 mmol sodium citrate in 50 mL of deionized water to obtain solution D; dissolve 7 mmol C6FeN6·4Na·10H2O in 50 mL of deionized water to obtain solution F; (4) At room temperature, both solution D and solution F are dispensed at a rate of 0.55 mL / min. -1 The solution was added dropwise to solution C and stirred for 12 hours, then allowed to stand for 12 hours. After washing three times with deionized water and twice with anhydrous ethanol, the solution was vacuum dried at 80°C for 12 hours to obtain the sodium-ion battery cathode material Na. 1.15 Fe 0.83 Mn 0.17 [Fe(CN)6]· 3.02 H2O@Na 1.45 Fe 0.33 Mn 0.33 Ni 0.34 [Fe(CN)6]· 2.78 H2O (FeMnHCF@FeMnNiHCF sodium-ion battery cathode material); the volume ratio of solution D, solution F and solution C is 1:1:4; The FeMnHCF@FeMnNiHCF sodium-ion battery cathode material of this embodiment has a three-dimensional rigid framework structure with open ion channels and spacious interstitial spaces, which can effectively promote sodium ion insertion; it has a core-shell bilayer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of iron-manganese-based ferricyanide (FeMnHCF) during repeated sodium ion insertion and extraction during charging and discharging. The FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material is used as the positive electrode active material to prepare the positive electrode of the sodium-ion battery: using FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material as the positive electrode active material, the positive electrode active material, conductive agent (SP) and binder (PVDF) are mixed evenly in a mass ratio of 7:2:1 and then coated on the surface of the positive electrode current collector aluminum foil to form the positive electrode material active layer; In this embodiment, metallic sodium is used as the negative electrode, glass fiber (Whatman, GF / A) is used as the separator, and the electrolyte is composed of a 1M NaClO4 solution of ethylene carbonate and diethyl carbonate (volume ratio 1:1), with the addition of fluorinated ethylene carbonate (mass concentration of fluorinated ethylene carbonate in the electrolyte is 5%). Aluminum foil is used as the positive electrode current collector, and a 13mm positive electrode material active layer (active components FeMnHCF@FeMnNiHCF sodium-ion battery positive electrode material (70wt.%), conductive agent (SP) (20wt.%), binder (PVDF) (10wt.%)) is coated on the surface of the aluminum foil to form a positive electrode sheet, which is then assembled into a button sodium-ion battery to optimize the performance of the iron-manganese-based Prussian blue (FeMnHCF) sodium-ion battery, including improving the battery's energy density, cycle stability, and reaction efficiency. Sodium-ion batteries with 1Ag -1 Cyclic testing was conducted at a current density of approximately 48.3 mAh g. After 1300 cycles, the discharge specific capacity remained at approximately 48.3 mAh g. -1 The material exhibits a high specific capacity with a specific capacity retention rate of 75% and good cycle stability. It possesses a core-shell bilayer structure, which effectively suppresses the Jahn-Teller effect of Mn and reduces the structural collapse problem of FeMnHCF during repeated sodium ion intercalation and deintercalation during charge and discharge. As a cathode material for sodium-ion batteries, it has excellent rate performance and long cycle life, thereby improving its performance in batteries.
[0021] Comparative Example: Preparation method of FeMnHCF sodium-ion battery cathode material, the specific steps are as follows: Solution A was obtained by mixing 1 mmol MnSO4·H2O, 3 mmol FeSO4·7H2O, 5 mmol sodium citrate, and 50 mL deionized water; solution B was obtained by mixing 7 mmol C6FeN6·4Na·10H2O and 50 mL deionized water; and solution B was obtained by mixing solution A with water at a concentration of 0.33 mL / min. -1 Add the solution to solution B dropwise and stir continuously for 12 hours. Let it stand and age for 24 hours. Centrifuge three times with deionized water and twice with anhydrous ethanol. Dry in a vacuum drying oven at 80°C for 12 hours to obtain the FeMnHCF sodium-ion battery cathode material Na. 1.15 Fe 0.74 Mn 0.26 [Fe(CN)6]· 3.02 H2O; The FeMnHCF sodium-ion battery cathode material can be used as a cathode active material to prepare sodium-ion battery cathodes: using FeMnHCF sodium-ion battery cathode material as the cathode active material, the cathode active material, conductive agent (SP) and binder (PVDF) are mixed evenly in a mass ratio of 7:2:1 and then coated on the surface of the cathode current collector aluminum foil to form a cathode material active layer. This comparative example uses metallic sodium as the negative electrode, glass fiber (Whatman, GF / A) as the separator, and the electrolyte consists of a 1M NaClO4 solution of ethylene carbonate and diethyl carbonate (volume ratio 1:1), with the addition of fluorinated ethylene carbonate (mass concentration of fluorinated ethylene carbonate in the electrolyte is 5%). Aluminum foil is used as the positive electrode current collector, and a 13mm positive electrode material active layer (active components FeMnHCF sodium-ion battery positive electrode material (70wt.%), conductive agent (SP) (20wt.%), binder (PVDF) (10wt.%)) is coated on the surface of the aluminum foil to form the positive electrode sheet. The sodium-ion battery is assembled and constant current charge-discharge test is performed, with the test voltage range being 2 to 4.2V. Sodium-ion batteries with 1Ag -1 Cyclic testing was conducted at a current density of approximately 43.9 mAh g. After 1300 cycles, the discharge specific capacity remained at approximately 43.9 mAh g. -1 The specific capacity is high, and the discharge specific capacity retention rate reaches 69%, but the discharge specific capacity decays relatively quickly. Iron-manganese-based ferricyanide (FeMnHCF) has problems such as disordered distribution of crystal water and vacancies, poor electronic conductivity, and Jahn-Teller effect of Mn, which lead to lattice distortion or structural collapse during sodium ion insertion and extraction, resulting in rapid capacity decay and poor battery rate performance and cycle life.
[0022] Therefore, this invention presents FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, which uses FeMnHCF as the core and FeMnNiHCF as the shell. Utilizing the dual mechanisms of core-shell separation and Ni doping, this FeMnHCF@FeMnNiHCF sodium-ion battery cathode material not only exhibits high initial discharge specific capacity but also good cycle stability at 1Ag. -1 After 1300 cycles at a current density, the specific capacity remained basically unchanged, with a specific capacity retention rate of 80%. This indicates that the material effectively suppresses the Jahn-Teller effect of Mn, reduces the structural collapse problem of iron-manganese ferricyanide (FeMnHCF) during repeated sodium ion insertion and extraction during charging and discharging, and has good rate performance and long cycle life as a positive electrode for sodium-ion batteries.
[0023] The specific embodiments of the present invention have been described in detail above. 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 FeMnHCF@FeMnNiHCF sodium-ion battery cathode material, characterized in that, The specific steps are as follows: (1) Dissolve FeSO4·7H2O, MnSO4·H2O and sodium citrate in deionized water to obtain solution A; dissolve C6FeN6·4Na·10H2O in deionized water to obtain solution B; (2) At room temperature, solution A is added dropwise to solution B and stirred for 12-36 hours, then allowed to stand and age for 12-24 hours to obtain solution C; (3) Dissolve MnSO4·H2O, FeSO4·7H2O, NiSO4·6H2O and sodium citrate in deionized water to obtain solution D; dissolve C6FeN6·4Na·10H2O in deionized water to obtain solution F; (4) At room temperature, solution D and solution F were added dropwise to solution C and stirred for 12-24 h. Then, the mixture was allowed to stand for 12-36 h and dried under vacuum to obtain FeMnHCF@FeMnNiHCF sodium-ion battery cathode material.
2. The preparation method of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material according to claim 1, characterized in that: Step (1) The solid-liquid ratio of FeSO4·7H2O, MnSO4·H2O, sodium citrate and deionized water is 0.6~10:0.6~1:1~15:30~100 mmol:mmol:mmol:ml.
3. The preparation method of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material according to claim 1, characterized in that: In step (1), the molar concentration of C6FeN6·4Na in solution B is 10~150 mol / L.
4. The method for preparing the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material according to claim 1, characterized in that: In step (2), the dropping rate of solution A is 0.33~1.6 ml·min. -1 The volume ratio of solution A to solution B is 0.5 to 1:
1.
5. The method for preparing the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material according to claim 1, characterized in that: Step (3) The solid-liquid ratio of MnSO4·H2O, FeSO4·7H2O, NiSO4·6H2O, sodium citrate and deionized water is 0.6~10:0.6~1:0.6~1:1~15:30~100 mmol:mmol:ml.
6. The method for preparing the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material according to claim 1, characterized in that: The molar concentration of C6FeN6·4Na in solution F is 10~150 mol / L.
7. The method for preparing the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material according to claim 1, characterized in that: In step (4), the dropping rate of solutions D and F is 0.33~1.6 ml·min. -1 The volume ratio of solutions D, F and C is 0.5~1:0.5~1:
1.
8. The application of the FeMnHCF@FeMnNiHCF sodium-ion battery cathode material prepared by the method according to any one of claims 1 to 7 as a cathode active material in the preparation of sodium-ion battery cathodes.