Preparation method and application of Cr-HEHCF sodium ion battery positive electrode material

Abstract

The invention relates to a preparation method and application of a Cr-HEHCF sodium ion battery positive electrode material, and belongs to the technical field of sodium ion batteries. The preparation method comprises the following steps: stirring and dissolving MnSO4. H2O, FeSO4. 7H2O, ZnSO4. 7H2O, NiSO4. 6H2O and Cr2 (SO4) 3 in deionized water to obtain a mixed solution A; stirring and dissolving C6FeN6. 4Na. 10H2O and sodium citrate in deionized water to obtain a mixed solution B; and under a stirring condition, dropwise adding the mixed solution B into the mixed solution A at a constant speed, stirring and reacting for 12-18 hours, standing and aging for 24-36 hours, carrying out solid-liquid separation, washing the solid with deionized water and ethanol, and carrying out vacuum drying to obtain the Cr-HEHCF sodium ion battery positive electrode material. The Cr-HEHCF sodium-ion battery positive electrode material disclosed by the invention is used as a positive electrode active material of a sodium-ion battery, and has excellent discharge performance, very good rate capability and excellent cycling stability.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a Cr-HEHCF sodium ion battery positive electrode material, belonging to the technical field of sodium ion batteries. Background Art

[0002] Prussian blue and its derivatives (PBAs) have shown significant promise as active materials for next-generation battery electrodes with improved cycle life and rate capability. First, PBAs are able to efficiently intercalate alkali and alkaline earth metals via a reversible two-electron reaction, resulting in high specific capacities. Second, their cubic geometry and nanoporous structure with wide channels and an open framework ensure fast ion transport, giving them excellent rate performance. Third, PBAs exhibit long-term stable cycle life due to their small geometric changes during ion insertion. In addition, these compounds are prepared by a simple and cost-effective co-precipitation reaction with aqueous precursors, making their production process relatively economical. Finally, their properties are highly tunable and suitable for different applications. However, the main disadvantage of PBAs is their low crystal density, which is less than half of that of high-performance lithium-ion cathodes.

[0003] At present, Prussian blue and its derivatives (PBAs) mainly have Fe(CN)6 vacancies. Water molecules will spontaneously enter the vacancies, causing changes in the structure of the material. The presence of vacancies will greatly reduce the active sites and break the electron transfer path. Excess water will hinder the migration of alkali metal ions and react with the electrolyte, causing the material to collapse during the sodium ion intercalation process, which restricts the application of PB and PBAs in sodium ion batteries. Summary of the invention

[0004] In view of the fact that the existing positive electrode materials of sodium ion batteries are generally doped with transition metal elements such as manganese, cobalt and copper, the cost is high and the Mn, Co and Cu-based Prussian blue materials are severely affected by the Jan-Taylor effect due to the corresponding transition metal elements. The dissolution of transition metals is very likely to occur during the charge and discharge process, causing structural damage, thereby reducing the material cycle stability and having the problem of poor cycle performance stability. The present invention proposes a preparation method and application of Cr-HEHCF sodium ion battery positive electrode material. The present invention utilizes an entropy engineering strategy to introduce 5 or more metals sharing N coordination to construct high entropy hexavalent ferricyanide (HE-HCF), enhance structural stability, optimize the diffusion path and energy barrier of Na ions, accelerate reaction kinetics, and thus improve reaction performance.

[0005] A method for preparing a Cr-HEHCF sodium ion battery positive electrode material, the specific steps are as follows:

[0006] (1) MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 were stirred and dissolved in deionized water to obtain a mixed solution A;

[0007] (2) stirring and dissolving C6FeN6·4Na·10H2O and sodium citrate in deionized water to obtain a mixed solution B;

[0008] (3) Under stirring conditions, the mixed solution B is uniformly dropped into the mixed solution A for stirring reaction for 12 to 18 hours, and then allowed to stand for aging for 24 to 36 hours. The solid-liquid separation is performed, and the solid is washed with deionized water and ethanol, and vacuum dried to obtain the Cr-HEHCF sodium ion battery positive electrode material.

[0009] In the step (1), the solid-to-liquid ratio of MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, Cr2(SO4)3 and deionized water, mmol:mmol:mmol:mmol:mmol:mL, is 0.7-1:0.7-1:0.7-1:1.5-2:1.5-2:50.

[0010] In the step (2), the solid-liquid ratio of C6FeN6·4Na·10H2O to deionized water is 2.5 to 3:20, and the solid-liquid ratio of sodium citrate to deionized water is 0.7 to 1:10.

[0011] The volume ratio of the mixed solution B to the mixed solution A in step (3) is 1:1.

[0012] The static aging temperature in step (3) is 15 to 35°C.

[0013] The Cr-HEHCF sodium ion battery positive electrode material can be used as a positive electrode active material to prepare a sodium ion battery positive electrode: the Cr-HEHCF sodium ion battery positive electrode material is used as the positive electrode active material, the positive electrode active material, the conductive agent and the binder are mixed evenly and then coated on the surface of the positive electrode current collector aluminum foil to form a positive electrode material active layer.

[0014] The sodium ion battery positive electrode, the sodium ion battery negative electrode (metallic sodium), the separator and the electrolyte (composed of a 1M NaClO4 solution of ethylene carbonate and diethyl carbonate (volume ratio of 1:1)) are assembled into a sodium ion battery.

[0015] The beneficial effects of the present invention are:

[0016] (1) The Cr-HEHCF sodium ion battery cathode material of the present invention has a face-centered cubic PBAs crystal structure, and the face-centered cubic PBAs crystal structure can form a three-dimensional rigid framework with open ion channels and spacious interstitial spaces, and is rich in redox active sites;

[0017] (2) The Cr-HEHCF sodium ion battery positive electrode material of the present invention has excellent charge and discharge performance, cycle performance and rate performance; at 0.1Ag -1 At this current density, its first discharge capacity reaches 70.4 mAh g -1 ,After 500 cycles, the specific capacity retention rate is 91.76%, which has high cycle stability;

[0018] (3) The Cr-HEHCF sodium ion battery positive electrode material of the present invention has a stable structure and is not easy to collapse during the charge and discharge process. The open ion channels and spacious gap space are conducive to the rapid migration of ions and improve the ion mobility. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The Cr-HEHCF sodium ion battery positive electrode material Na of Example 2 1.12 Fe 0.23 Mn 0.21 Zn 0.23 Ni 0.30 Cr 0.03

[0020] [Fe(CN)6] 0.76 · 0.24 ·3.17XRD pattern of H2O;

[0021] Figure 2 The Cr-HEHCF sodium ion battery positive electrode material Na of Example 2 1.12 Fe 0.23 Mn 0.21 Zn 0.23 Ni 0.30 Cr 0.03

[0022] [Fe(CN)6] 0.76 · 0.24 ·3.17H2O SEM image;

[0023] Figure 3 The Cr-HEHCF sodium ion battery positive electrode material Na of Example 2 1.12 Fe 0.23 Mn 0.21 Zn 0.23 Ni 0.30 Cr0.03

[0024] [Fe(CN)6] 0.76 · 0.24 ·CV curve of sodium ion battery prepared by 3.17H2O;

[0025] Figure 4 The Cr-HEHCF sodium ion battery positive electrode material Na of Example 2 1.12 Fe 0.23 Mn 0.21 Zn 0.23 Ni 0.30 Cr 0.03

[0026] [Fe(CN)6] 0.76 · 0.24 ·3.17H2O prepared sodium ion battery charge and discharge curve at room temperature;

[0027] Figure 5 The Cr-HEHCF sodium ion battery positive electrode material Na of Example 2 1.12 Fe 0.23 Mn 0.21 Zn 0.23 Ni 0.30 Cr 0.03

[0028] [Fe(CN)6] 0.76 · 0.24 ·3.17H2O prepared sodium ion battery constant current cycling performance curve at room temperature;

[0029] Figure 6 The Cr-HEHCF sodium ion battery positive electrode material Na of Example 2 1.12 Fe 0.23 Mn 0.21 Zn 0.23 Ni 0.30 Cr 0.03

[0030] [Fe(CN)6] 0.76 · 0.24 ·3.17H2O prepared sodium ion battery constant current cycling performance curves at different rates at room temperature. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0032] Example 1: A method for preparing a Cr-HEHCF sodium ion battery positive electrode material, the specific steps are as follows:

[0033] (1) MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 were stirred and dissolved in deionized water to obtain a mixed solution A; the solid-liquid ratio of MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 to deionized water, mmol:mmol:mmol:mmol:mmol:mL, was 1:1:1:1:1:50;

[0034] (2) stirring and dissolving C6FeN6·4Na·10H2O and sodium citrate in deionized water to obtain a mixed solution B; the solid-liquid ratio of C6FeN6·4Na·10H2O to deionized water is 3:20 in mmol:mL, and the solid-liquid ratio of sodium citrate to deionized water is 1:10 in mmol:mL;

[0035] (3) Under stirring conditions, a peristaltic pump was used to pump the mixed solution B at a rate of 0.55 ml min -1 The mixed solution A was added at a uniform speed and stirred for 6 hours, and then aged at room temperature for 24 hours. The solid-liquid separation was carried out, and the solid was washed with deionized water and ethanol, and vacuum dried at 60 ° C for 36 hours to obtain the Cr-HEHCF sodium ion battery positive electrode material Na 1.24 Fe 0.26 Mn 0.28 Zn 0.26 Ni 0.18 Cr 0.02 [Fe(CN)6] 0.71 · 0.19 · 3.01 H2O; the volume ratio of the mixed solution B to the mixed solution A is 1:1;

[0036] The Cr-HEHCF sodium ion battery positive electrode material of this embodiment is characterized by its abundant redox active sites, which provide more contact points for the electrolyte and the active material, thereby improving the reaction efficiency of the battery; its unique three-dimensional rigid framework structure has open ion channels and spacious gap space, which effectively improves the number and mobility of ion diffusion;

[0037] The Cr-HEHCF sodium ion battery positive electrode material can be used as a positive electrode active material to prepare a sodium ion battery positive electrode: the Cr-HEHCF sodium ion battery positive electrode material is used as a positive electrode active material, the positive electrode active material, a conductive agent and a binder are mixed evenly and then coated on the surface of a positive electrode current collector aluminum foil to form a positive electrode material active layer;

[0038] In this embodiment, sodium metal is used as the negative electrode sheet, glass fiber (Whatman, GF / A) is used as the separator, the electrolyte is composed of 1M NaClO4 ethylene carbonate and diethyl carbonate (volume ratio is 1:1) solution, and fluoroethylene carbonate is added (the mass concentration of fluoroethylene carbonate in the electrolyte is 5%), aluminum foil is used as the positive electrode current collector, and a 12mm positive electrode material active layer (active components Cr-HEHCF 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, and assembled into a sodium ion battery to optimize the performance of the sodium ion battery, including improving the energy density, cycle stability and reaction efficiency of the battery;

[0039] Sodium ion batteries with a capacity of 0.1A g -1 After 500 cycles, the discharge capacity can still maintain about 64.6 mA hg -1 The specific capacity of the battery is 91.76%, and the specific capacity retention rate reaches 91.76%, with excellent cycle stability. The material utilizes high entropy effect, hysteresis diffusion effect, lattice distortion effect and synergistic effect in performance to improve its performance in the battery.

[0040] Example 2: A method for preparing a Cr-HEHCF sodium ion battery positive electrode material, the specific steps are as follows:

[0041] (1) MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 were stirred and dissolved in deionized water to obtain a mixed solution A; the solid-liquid ratio of MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 to deionized water, mmol:mmol:mmol:mmol:mmol:mL, was 1:1:1:2:2:50;

[0042] (2) stirring and dissolving C6FeN6·4Na·10H2O and sodium citrate in deionized water to obtain a mixed solution B; the solid-liquid ratio of C6FeN6·4Na·10H2O to deionized water is 3:20 in mmol:mL, and the solid-liquid ratio of sodium citrate to deionized water is 1:10 in mmol:mL;

[0043] (3) Under stirring conditions, a peristaltic pump was used to pump the mixed solution B at a rate of 0.55 ml min -1The mixed solution A was uniformly dropped into the mixture at a speed of 1:1, stirred and reacted for 12 hours, and allowed to stand for aging at a temperature of about 25°C for 36 hours, solid-liquid separation, the solid was washed with deionized water and ethanol, and vacuum dried at a temperature of 120°C for 24 hours to obtain Cr-HEHCF sodium ion battery positive electrode material; the volume ratio of the mixed solution B to the mixed solution A was 1:1;

[0044] The XRD spectrum of the Cr-HEHCF sodium ion battery positive electrode material in this embodiment is shown in Figure 1 ,from Figure 1 It can be seen that the peak shape is relatively sharp, indicating that the prepared cathode material has a high degree of crystallinity and a small grain size;

[0045] The SEM image of the Cr-HEHCF sodium ion battery positive electrode material of this embodiment is shown in Figure 2 ,from Figure 2 It can be seen that the Cr-HEHCF sodium ion battery cathode material is a three-dimensional stacking structure with relatively regular oblate spherical nanoparticles with a diameter of about 50 to 180 nm and a small particle size;

[0046] The Cr-HEHCF sodium ion battery positive electrode material can be used as a positive electrode active material to prepare a sodium ion battery positive electrode: the Cr-HEHCF sodium ion battery positive electrode material is used as a positive electrode active material, the positive electrode active material, a conductive agent and a binder are mixed evenly and then coated on the surface of a positive electrode current collector aluminum foil to form a positive electrode material active layer;

[0047] In this embodiment, sodium metal is used as the negative electrode sheet, glass fiber (Whatman, GF / A) is used as the separator, the electrolyte is composed of 1M NaClO4 ethylene carbonate and diethyl carbonate (volume ratio is 1:1) solution, and fluoroethylene carbonate is added (the mass concentration of fluoroethylene carbonate in the electrolyte is 5%), aluminum foil is used as the positive electrode current collector, and a 12mm positive electrode material active layer (active components Cr-HEHCF 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, and assembled into a sodium ion battery to optimize the performance of the sodium ion battery, including improving the energy density, cycle stability and reaction efficiency of the battery;

[0048] The CV curve of the potassium ion battery prepared by the Cr-HEHCF sodium ion battery positive electrode material of this embodiment is shown in Figure 3 ,from Figure 3 It can be seen that in the voltage range of 2 to 4.2 V, the -1 The scan rate was cyclically tested, and an oxidation peak appeared at about 3.4V and a reduction peak appeared at about 3.1V.

[0049] The charge and discharge curves of the potassium ion battery prepared from the Cr-HEHCF sodium ion battery positive electrode material of this embodiment at room temperature are shown in FIG. Figure 4 ,from Figure 4 It can be seen that the voltage window is between 2 and 4.2 V, with a 15 mA g -1 The current density was used for charge and discharge cycle test, and the first discharge capacity was as high as 77mA hg -1 ; The third discharge capacity is 75.7mA hg -1 ; After 98 discharges, the specific capacity is 70.8 mA hg -1 ;

[0050] The constant current cycle performance curve of the sodium ion battery of this embodiment at room temperature is shown in Figure 5 ,from Figure 5 It can be seen that the voltage window is between 2 and 4.2V, with 0.1Ag -1 During the first cycle, the discharge capacity was about 70.4 mAh g -1 During the second cycle, the discharge capacity decreased slightly to about 70.3 mA h g -1 After 500 cycles, the discharge capacity can still maintain about 64.6mA hg -1 The specific capacity retention rate reaches 91.76%;

[0051] The constant current cycle performance curves of the sodium ion battery of this embodiment at different rates at room temperature are shown in Figure 6 ,from Figure 6 It can be seen that five consecutive cycle tests were carried out at rates of 1.5C, 3C, 7.5C, 15C, and 30C, and the corresponding specific capacity was 70 mAh g -1 、67.3mA hg -1 、64.4mA hg -1 、58.5mA hg -1 、42.4mA hg -1 When charged and discharged again from 30C to 1.5C, the specific capacity is almost exactly the same as before, indicating that this sodium ion battery cathode material has high rate capability and stable cycle performance;

[0052] Therefore, the Cr-HEHCF sodium ion battery positive electrode material for the sodium ion battery of this embodiment as the sodium ion battery negative electrode not only exhibits stable discharge and high rate performance, but also has excellent cycle stability performance at 0.1A g -1 After 500 cycles at a current density of , the specific capacity retention rate reached 91.76%, indicating that the sodium ion battery has good cycle stability and capacity retention performance.

[0053] Example 3: A method for preparing a Cr-HEHCF sodium ion battery positive electrode material, the specific steps are as follows:

[0054] (1) MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 were stirred and dissolved in deionized water to obtain a mixed solution A; the solid-liquid ratio of MnSO4·H2O, FeSO4·7H2O, ZnSO4·7H2O, NiSO4·6H2O, and Cr2(SO4)3 to deionized water, mmol:mmol:mmol:mmol:mmol:mL, was 1:1:1:2:3:50;

[0055] (2) stirring and dissolving C6FeN6·4Na·10H2O and sodium citrate in deionized water to obtain a mixed solution B; the solid-liquid ratio of C6FeN6·4Na·10H2O to deionized water is 3:20 in mmol:mL, and the solid-liquid ratio of sodium citrate to deionized water is 1:10 in mmol:mL;

[0056] (3) Under stirring conditions, a peristaltic pump was used to pump the mixed solution B at a rate of 0.55 ml min -1 The mixed solution A was added at a uniform speed and stirred for 12 hours, and then aged at about 25°C for 28 hours. The solid-liquid separation was carried out, and the solid was washed with deionized water and ethanol, and vacuum dried at 80°C for 30 hours to obtain the Cr-HEHCF sodium ion battery positive electrode material Na 1.22 Fe 0.25 Mn 0.25 Zn 0.21 Ni 0.21 Cr 0.13 [Fe(CN)6] 0.73 · 0.27 ·2.87H2O; the volume ratio of the mixed solution B to the mixed solution A is 1:1;

[0057] The Cr-HEHCF sodium ion battery positive electrode material of this embodiment is characterized by its abundant redox active sites, which provide more contact points for the electrolyte and the active material, thereby improving the reaction efficiency of the battery; its unique three-dimensional rigid framework structure has open ion channels and spacious gap space, which effectively improves the number and mobility of ion diffusion;

[0058] The Cr-HEHCF sodium ion battery positive electrode material can be used as a positive electrode active material to prepare a sodium ion battery positive electrode: the Cr-HEHCF sodium ion battery positive electrode material is used as a positive electrode active material, the positive electrode active material, a conductive agent and a binder are mixed evenly and then coated on the surface of a positive electrode current collector aluminum foil to form a positive electrode material active layer;

[0059] In this embodiment, sodium metal is used as the negative electrode sheet, glass fiber (Whatman, GF / A) is used as the separator, the electrolyte is composed of 1M NaClO4 ethylene carbonate and diethyl carbonate (volume ratio is 1:1) solution, and fluoroethylene carbonate is added (the mass concentration of fluoroethylene carbonate in the electrolyte is 5%), aluminum foil is used as the positive electrode current collector, and a 12mm positive electrode material active layer (active components Cr-HEHCF 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, and assembled into a sodium ion battery to optimize the performance of the sodium ion battery, including improving the energy density, cycle stability and reaction efficiency of the battery;

[0060] Sodium ion batteries with a capacity of 0.1A g -1 After 500 cycles, the discharge capacity can still maintain about 64.6 mA hg -1 The specific capacity of the battery is 91.76%, and the specific capacity retention rate reaches 91.76%, with excellent cycle stability. The material utilizes high entropy effect, hysteresis diffusion effect, lattice distortion effect and synergistic effect in performance to improve its performance in the battery.

[0061] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing a Cr-HEHCF sodium ion battery positive electrode material, It is characterized in that The specific steps are as follows: (1) MnSO 4 ·H 2 O, FeSO 4 7H 2 O、ZnSO 4 7H 2 O、NiSO 4 6H 2 O、Cr 2 (SO 4 ) 3 Stir and dissolve in deionized water to obtain a mixed solution A; (2) C 6 FeN 6 4Na 10H 2 O and sodium citrate were stirred and dissolved in deionized water to obtain a mixed solution B; (3) Under stirring conditions, the mixed solution B is uniformly dropped into the mixed solution A for stirring reaction for 12 to 18 hours, and then allowed to stand for aging for 24 to 36 hours. The solid-liquid separation is performed, and the solid is washed with deionized water and ethanol, and vacuum dried to obtain the Cr-HEHCF sodium ion battery positive electrode material.

2. The method for preparing the Cr-HEHCF sodium ion battery positive electrode material according to claim 1, Features: Step (1) MnSO 4 ·H 2 O, FeSO 4 7H 2 O、ZnSO 4 7H 2 O、NiSO 4 6H 2 O、Cr 2 (SO 4 ) 3 The solid-to-liquid ratio of mmol:mmol:mmol:mmol:mmol:mL to deionized water is 0.7~1:0.7~1:0.7~1:1.5~2:1.5~2:

50.

3. The method for preparing the Cr-HEHCF sodium ion battery positive electrode material according to claim 1, Features: Step (2) C 6 FeN 6 4Na 10H 2 The solid-liquid ratio of sodium iodide to deionized water is 2.5 to 3:20, and the solid-liquid ratio of sodium citrate to deionized water is 0.7 to 1:

10.

4. The method for preparing the Cr-HEHCF sodium ion battery positive electrode material according to claim 1, Features: The volume ratio of the mixed solution B to the mixed solution A in step (3) is 1:

1.

5. The method for preparing the Cr-HEHCF sodium ion battery positive electrode material according to claim 1, Features: The standing aging temperature in step (3) is 15 to 35°C.

6. The Cr-HEHCF sodium ion battery positive electrode material prepared by the method according to any one of claims 1 to 5 is used as a positive electrode active material to prepare a sodium ion battery positive electrode.

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