Zirconium pyrophosphate surface coated and modified O3-phase sodium-nickel-manganese-iron-oxide layered composite material and preparation method thereof

Abstract

The invention belongs to the field of new energy materials and electrochemical energy storage, and particularly relates to a zirconium pyrophosphate surface coated and modified O3-phase sodium nickel manganese iron oxide layered composite material, the structural formula of the material is NaNi < 0.25 > Fe < 0.30 > Mn < 0.45 > O < 2 > (at) ZrP2O7, and the material can be used as a long-life and high-energy-density sodium ion battery positive electrode active material. A uniform and conformal zirconium-based-phosphate artificial interface layer with the thickness of 1-2 nm is constructed on the surface of a nickel-iron-manganese hydroxide precursor through an insoluble salt precipitation conversion reaction, subsequent sodium-mixed calcination is performed, the calcination conditions are regulated and controlled, and finally an O3-phase sodium-nickel-iron-manganese oxide NaNi < 0.25 > Fe < 0.30 > Mn < 0.45 > O < 2 > (at) ZrP2O7 layered material coated with zirconium pyrophosphate on the surface is synthesized to serve as the sodium-ion battery positive electrode material. The material shows excellent electrochemical performance in a high-potential interval.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy materials and electrochemical energy storage, and particularly relates to a pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese iron oxy-layer composite material and a preparation method thereof. BACKGROUND

[0002] In recent years, the increasingly serious energy crisis and environmental problems have forced researchers and academia to turn to the development of clean energy. Sodium, due to its similar chemical properties to lithium and abundant natural reserves, is one of the most promising next-generation energy storage battery systems. O3 sodium nickel manganese iron oxy-layer oxides (NaNi 0.25 Fe 0.30 Mn 0.45 O2) have become a strong candidate for commercialized positive electrode materials of sodium ion batteries (SIBs) due to their high theoretical specific capacity, easily controllable structural characteristics, abundant resources, environmental friendliness and cost advantages compatible with lithium ion battery production lines. However, the layered oxides have problems such as interlayer slippage and phase change, irreversible structural collapse, slow sodium ion diffusion kinetics, and serious interface side reactions and transition metal dissolution during charging and discharging, which limit their practical application. SUMMARY

[0003] The technical problem to be solved by the application is to design a pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese iron oxy-layer composite material and a preparation method thereof, which has a simple process and meets the requirements of green chemistry. The pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese iron oxy-layer composite material has excellent electrochemical performance when applied to sodium ion battery positive electrode materials.

[0004] A preparation method of a pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese iron oxy-layer composite material, comprising the following steps: S1, adding transition metals to a solvent and dissolving uniformly, then adding an ammonia solution and aging; S2, adding (NH4)2HPO4 solution to the solution after step S1 reaction, and after aging reaction is completed, adding ZrOCl2·8H2O solution and continuing aging treatment until the reaction is completed; S3, after the solution after step S2 reaction is sequentially subjected to suction filtration, washing and drying treatment, a precursor powder is obtained; S4, mixing the precursor powder with a sodium source, and sequentially subjecting to grinding and calcination treatment to obtain the pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese iron oxy-layer composite material.

[0005] Further, in step S1, the molar ratio of NiSO4·6H2O:FeSO4·7H2O:MnSO4·H2O is 3.0-6.0:3.6-7.2:5.4-10. The solvent is deionized water, and the volume of the solvent is 850-950 mL.

[0006] Further, in step S1, the dissolution conditions of the transition metal are performed under a water bath condition of 50-80°C, and the stirring time condition is 10-15 min; the aging time condition is 5 h.

[0007] Further, in step S1, the concentration of the ammonia solution is 1.0-1.2 mol·L -1 , the feeding speed of the ammonia solution is 10 mL·h -1 , and the volume ratio of the mixed solution to the ammonia solution is 17:1-19:1.

[0008] Further, in step S2, the concentration of the (NH4)2HPO4 solution is 0.00024-0.0024 mmol·L -1 , and the feeding speed is 10 mL·h -1 . The concentration of the ZrOCl2·8H2O solution is 0.00024-0.0024 mmol·L -1 , and the feeding speed is 10 mL·h -1 .

[0009] Further, in step S2, the time condition of the first aging reaction and the second aging reaction is 5 h.

[0010] Further, in step S3, the drying temperature condition is 60-100°C, and the time condition is 12 h.

[0011] Further, in step S4, the sodium source is sodium nitrate, and the molar ratio of the sodium source to the transition metal is 1.05-1.20:1. The calcination temperature condition is 800-900°C, and the time condition is 10-16 h.

[0012] The O3 phase sodium nickel manganese ferrite layered composite material with pyrophosphoric acid zirconium surface coating modification obtained by the above preparation method has the structural formula NaNi 0.25 Fe 0.30 Mn 0.45 O2@ZrP2O7.

[0013] The application of the above O3 phase sodium nickel manganese ferrite layered composite material with pyrophosphoric acid zirconium surface coating modification in the field of sodium ion battery positive electrode materials.

[0014] The application of the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification on the positive electrode material field of sodium ion battery.

[0015] The beneficial effects of the present application are: (1) the present application constructs a 1-2 nm thick, uniform and conformal zirconium-based-phosphate artificial interface layer on the surface of nickel-iron-manganese hydroxide precursor through a difficult salt precipitation conversion reaction, and then mixes sodium and calcines, adjusts the calcination conditions, and finally synthesizes the O3 phase sodium nickel iron manganese oxygen NaNi 0.25 Fe 0.30 Mn 0.45 O2@ZrP2O7 layered material as a positive electrode material of sodium ion battery, it shows excellent electrochemical performance in high potential interval.

[0016] (2) the positive electrode material prepared by the preparation method has a voltage interval of 2.5-4.2 V, and as a sodium ion positive electrode material, it shows excellent high specific capacity, high rate performance and excellent cycle performance, and is a potential application material of high-power and long-life sodium ion battery.

[0017] (3) the preparation method of the present application is simple, meets the requirements of green chemistry, has low requirements for equipment, and is conducive to the market application of sodium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the XRD pattern of the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification of the present application embodiment 1; Figure 2 is the XPS pattern of Zr and P elements in the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification of the present application embodiment 1; Figure 3 is the EDS mapping pattern of the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification of the present application embodiment 1; Figure 4 is the TEM pattern of the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification of the present application embodiment 1; Figure 5 is the battery cycle curve graph of the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification of the present application embodiment 1 at 48.0 mA·g -1 small current density; Figure 6 is the battery cycle curve graph of the O3 phase sodium nickel manganese iron oxide layered composite material coated by zirconium pyrophosphate surface modification of the present application embodiment 1 at 240 mA·g -1 large current density; Figure 7 is a rate performance comparison chart of the zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese ferrite layered composite material of embodiment 1 of the present application and the uncoated sodium nickel manganese ferrite layered sodium storage material. DETAILED DESCRIPTION

[0019] In order to better understand the present application, the content of the present application is further illustrated below in combination with examples, but the content of the present application is not limited only to the following examples.

[0020] The first protection of the present application is a preparation method of a zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese ferrite layered composite material, comprising the following steps: (1) adding a transition metal (TM) into 850-950 mL of deionized water, stirring for 10-15 min under the condition of a 50-80℃ water bath to make it dissolve; The transition metal is a combination of NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O; and the molar ratio of NiSO4·6H2O:FeSO4·7H2O:MnSO4·H2O is 3.0-6.0:3.6-7.2:5.4-10; specifically, the molar ratio of NiSO4·6H2O:FeSO4·7H2O:MnSO4·H2O can be 3.0:3.6:5.4, 4.5:5.4:7.7, 6.0:7.2:10; (2) feeding 1.0-1.2 mol·L -1 of ammonia solution into the solution obtained in step (1) at a speed of 10 mL·h -1 -1, and the volume ratio of the mixed solution to the ammonia solution in step (1) is 17:1-19:1, and the feeding process is kept under intense stirring, and 5 h of aging is performed after the injection is completed; The concentration of the ammonia solution is 1.0 mol·L -1 , 1.1 mol·L -1 , 1.2 mol·L -1 ; The volume ratio of the mixed solution to the ammonia solution is 17:1, 18:1, 19:1; (3) feeding 50 mL of (NH4)2HPO4 solution with a concentration of 0.00024-0.0024 mmol·L -1 at a speed of 10 mL·h -1 into the solution obtained in step (2), and the feeding process is kept under intense stirring, and 5 h of aging is performed after the injection is completed; (4) feeding 50 mL of ZrOCl2·8H2O solution with a concentration of 0.00024-0.0024 mmol·L -1 at a speed of 10 mL·h-1 The solution obtained in step (3) is fed at a speed, and the feeding is kept under intense stirring, and a 5 h aging is performed after the injection is completed; (5) The solution obtained in step (4) is suction filtered, washed, and dried at 60-100 ℃ for 12 h to obtain a precursor powder; (6) The precursor powder obtained in step (5) is mixed with a certain amount of sodium nitrate (Na: TM = 1.05-1.20) and ground, and then placed in a muffle furnace for calcination at 800-900 ℃ for 10-16 h to obtain a black powder-shaped zirconium pyrophosphate surface-coated modified O3 phase layered sodium-ion battery cathode material.

[0021] In the present application, a 1-2 nm thick, conformal, high-conductivity and chemically stable zirconium pyrophosphate artificial interface layer is constructed on the surface of the material, a mixed surface of layered and salt rock phases is formed in situ, and the strategy of zirconium pyrophosphate (ZrP2O7) coating is used to optimize the NaNi 0.25 Fe 0.30 Mn 0.45 O2 material, the dissolution of transition metals and the interface side reaction are inhibited, the ion transmission of the material under high pressure is improved, the problem of rapid increase of interface charge transfer impedance during battery cycle is relieved, and the average discharge voltage and energy density of the material are also improved by the induction effect of PO4 3- The modified material exhibits long cycle life, high energy density and low transition metal dissolution in the high potential range of 2.5-4.2 V.

[0022] The second protection of the present application is the zirconium pyrophosphate surface-coated modified O3 phase sodium nickel manganese iron-oxygen layered composite material prepared by the above preparation method, and the structural formula of the layered composite material is NaNi 0.25 Fe 0.30 Mn 0.45 O2@ZrP2O7.

[0023] The third protection of the present application is the application of the above zirconium pyrophosphate surface-coated modified O3 phase sodium nickel manganese iron-oxygen layered composite material as a sodium-ion battery cathode material.

[0024] <Example 1> The preparation method of the zirconium pyrophosphate surface-coated modified O3 phase sodium nickel manganese iron-oxygen layered composite material comprises the following steps: (1) 3 mmol of NiSO4·6H2O, 3.6 mmol of FeSO4·7H2O and 5.4 mmol of MnSO4·H2O are added to 850 mL of deionized water, and stirred at 50 ℃ water bath for 10 min to dissolve; (2) 1 mol·L -1ammonia solution at 10 mL·h -1 50 mL of the solution obtained in step (1) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (3) Use a syringe pump to dispense 50 mL of a solution prepared with 0.036 mmol (NH4)2HPO4 at a rate of 10 mL·h. -1 50 mL of the solution obtained in step (2) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (4) Use a syringe pump to dispense 50 mL of a solution prepared with 0.036 mmol ZrOCl2·8H2O at a rate of 10 mL·h. -1 50 mL of the solution obtained in step (3) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (5) The solution obtained in step (4) is filtered, washed and dried at 80 °C for 12 h to obtain precursor powder; (6) The precursor obtained in step (5) is mixed and ground with a certain amount of sodium nitrate (Na: TM = 1.13) and then placed in a muffle furnace and calcined at 800 °C for 12 h to obtain a black powder of zirconium pyrophosphate surface-coated modified O3 phase sodium nickel manganese iron oxide layered sodium storage composite material.

[0025] Taking the O3-phase sodium-nickel-manganese ferrite layered composite material with zirconium pyrophosphate surface-modified coating obtained in this embodiment as an example, its structure was determined by X-ray diffraction (XRD). Figure 1 As shown, XRD indicates that the surface-coated modified O3 phase sodium-nickel-manganese iron-oxygen sodium storage material exhibits a typical trigonal crystal structure (R-3m space group, PDF#54-0887), proving that NaNi 0.25 Fe 0.30 Mn 0.45 O2 is the main phase and there are no other impurities.

[0026] like Figure 2 As shown in the XPS spectrum, P2O7 can be observed at 132.8 eV. 2- P2p 3 / 2 Based on the binding energy, it can be determined that most P elements are in the form of P₂O₇. 2- It exists in the form of Zr3d. The binding energies of 183.83 eV and 181.58 eV represent Zr3d. 3 / 2 and Zr 3d 5 / 2 .

[0027] like Figure 3As shown in the EDS mapping diagram, the matrix elements such as Na, Ni, Mn, Fe, and O, as well as the P and Zr elements introduced by the coating, exhibit uniform distribution on the material surface. In particular, the uniform distribution of P and Zr elements can, to a certain extent, indicate the successful construction of the zirconium phosphate coating layer on the material surface, and the coating components have good dispersion on the material surface.

[0028] like Figure 4 As shown, the transmission electron microscope image reveals a uniform, conformal coating layer on the material surface.

[0029] The zirconium pyrophosphate prepared in this embodiment is coated with a modified O3 phase sodium-nickel-manganese-iron-oxygen NaNi. 0.25 Fe 0.30 Mn 0.45 The O2@ZrP2O7 layered composite material is used as the positive electrode active material for sodium-ion batteries. The remaining steps of the preparation method for sodium-ion batteries are the same as those of conventional preparation methods. The preparation method of the electrode sheet is as follows: using the layered composite material as the active material, Super P as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder, the mass ratio of active material, Super P and PVDF is 7:2:1. After thoroughly mixing them in the specified ratio, they are uniformly coated on aluminum foil and activated in an oven at 120°C for 12 hours. The resulting electrode sheets are then punched into 11 mm diameter sheets for later use. A coin cell sodium-ion battery is assembled using 1M NaClO4 in PC solvent (100 Vol%) with 5% FEC as the electrolyte, a self-made sodium sheet as the negative electrode, glass fiber as the separator, and CR2032 stainless steel as the battery casing.

[0030] The zirconium pyrophosphate prepared in this embodiment is coated with a modified O3 phase sodium-nickel-manganese-iron-oxygen NaNi. 0.25 Fe 0.30 Mn 0.45 Taking O2@ZrP2O7 layered composite material as a cathode material for sodium-ion batteries as an example, Figure 5 As shown, this material is at 48.0 mA·g -1 The test was conducted below, and the specific capacity reached 131.8 mAh·g in the first cycle. -1 In subsequent cycles, the coulomb efficiency is close to 100%, and after 100 cycles, the capacity retention rate can reach 81.2%, demonstrating excellent cycling performance.

[0031] like Figure 6 As shown, this layered composite material at 240 mA·g -1 After 100 cycles of constant current charge-discharge testing at high current density, the discharge specific capacity still reached 95.0 mA·g. -1 It has good cycle performance and long life performance.

[0032] likeFigure 7 As shown, at 24.0 mA·g -1 48.0 mA·g -1 120 mA·g -1 240 mA·g -1 480 mA·g -1 1200 mA·g -1 2400 mA·g -1 Constant current charge-discharge tests were conducted at current densities, and the discharge specific capacities reached 131.3, 124.0, 112.8, 104.7, 97.9, 87.6, and 73.0 mAh·g, respectively. -1 When the current density increases from 2400 mA·g -1 Restored to the initial value of 24.0 mA·g -1 At that time, the discharge specific capacity of the layered composite material was 124.9 mAh·g. -1 The result showed excellent rate performance, achieving 95.1% of the initial capacity. These properties indicate that the O3-phase sodium-nickel-manganese-iron-oxygen layered composite material with zirconium pyrophosphate surface coating possesses excellent high-rate characteristics and cycle performance, making it a potential material for high-power, long-life sodium-ion batteries.

[0033] <Example 2> The preparation method of O3 phase sodium nickel manganese ferrite layered composite material with zirconium pyrophosphate surface coating modification includes the following steps: (1) Add 3 mmol NiSO4·6H2O, 3.6 mmol FeSO4·7H2O and 5.4 mmol MnSO4·H2O to 850 mL of deionized water and stir for 10 min in a 50 ℃ water bath to dissolve them; (2) Use a syringe pump to deliver 1 mol·L -1 ammonia solution at 10 mL·h -1 50 mL of the solution obtained in step (1) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (3) Use a syringe pump to dispense 50 mL of a solution prepared with 0.036 mmol (NH4)2HPO4 at a rate of 10 mL·h. -1 50 mL of the solution obtained in step (2) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (4) Use a syringe pump to dispense 50 mL of a solution prepared with 0.036 mmol ZrOCl2·8H2O at a rate of 10 mL·h. -1 50 mL of the solution obtained in step (3) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (5) The solution obtained in step (4) is filtered, washed and dried at 80 °C for 12 h to obtain a precursor powder; (6) The precursor obtained in step (5) is mixed with a certain amount of sodium nitrate (Na: TM = 1.13) and ground, and then calcined in a muffle furnace at 850 °C for 12 h to obtain a black powder of zirconium pyrophosphate surface coated modified sodium nickel manganese iron-based sodium storage composite material.

[0034] The zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese iron oxide layered composite material prepared in this example is used as an example of a sodium ion battery positive electrode material. The charge-discharge test is carried out at a current density of 240 mA·g -1 -1, and after 100 cycles, the discharge specific capacity is still 87.7 mAh·g -1 -1, and has good electrochemical performance.

[0035] <Embodiment 3> A preparation method of zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese iron oxide layered composite material, comprising the following steps: (1) 3 mmol of NiSO4·6H2O, 3.6 mmol of FeSO4·7H2O and 5.4 mmol of MnSO4·H2O are added to 850 mL of deionized water, and stirred at 50 °C water bath for 10 min to dissolve; (2) 1 mol·L -1 of ammonia solution is fed into the solution obtained in step (1) at a speed of 10 mL·h -1 -1, and the stirring is kept intense during the feeding, and after the injection is completed, the aging is carried out for 5 h; (3) 0.036 mmol of (NH4)2HPO4 is configured into 50 mL of solution, and fed into the solution obtained in step (2) at a speed of 10 mL·h -1 -1, and the stirring is kept intense during the feeding, and after the injection is completed, the aging is carried out for 5 h; (4) 0.036 mmol of ZrOCl2·8H2O is configured into 50 mL of solution, and fed into the solution obtained in step (3) at a speed of 10 mL·h -1 -1, and the stirring is kept intense during the feeding, and after the injection is completed, the aging is carried out for 5 h; (5) The solution obtained in step (4) is filtered, washed and dried at 80 °C for 12 h to obtain a precursor powder; (6) The precursor obtained in step (5) is mixed with a certain amount of sodium nitrate (Na: TM = 1.13) and ground, and then placed in a muffle furnace for calcination at 900 ℃ for 12 h to obtain black powder-like pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese iron sodium storage composite material.

[0036] The O3 phase sodium nickel manganese ferrite layered composite material prepared in this example is used as an example of a sodium ion battery positive electrode material. The charge-discharge test is carried out at a current density of 240 mA·g -1 -1, and after 100 cycles, the discharge specific capacity can reach 77.7 mAh·g -1 -1, and after 100 cycles, the discharge specific capacity can reach 77.7 mAh·g -1 -1, and after 100 cycles, the discharge specific capacity can reach 77.7 mAh·g

[0037] <Embodiment 4> The preparation method of the O3 phase sodium nickel manganese ferrite layered composite material coated with pyrophosphoric acid zirconium includes the following steps: (1) 3 mmol of NiSO4·6H2O, 3.6 mmol of FeSO4·7H2O and 5.4 mmol of MnSO4·H2O are added to 850 mL of deionized water, and stirred at 50 ℃ water bath for 10 min to dissolve; (2) 1 mol·L -1 of ammonia solution is fed into the solution obtained in step (1) at a speed of 10 mL·h -1 -1, and after 100 cycles, the discharge specific capacity can reach 77.7 mAh·g (3) 0.036 mmol of (NH4)2HPO4 is configured into a 50 mL solution, which is fed into the solution obtained in step (2) at a speed of 10 mL·h -1 -1, and after 100 cycles, the discharge specific capacity can reach 77.7 mAh·g (4) 0.036 mmol of ZrOCl2·8H2O is configured into a 50 mL solution, which is fed into the solution obtained in step (3) at a speed of 10 mL·h -1 -1, and after 100 cycles, the discharge specific capacity can reach 77.7 mAh·g (5) The solution obtained in step (4) is filtered, washed and dried at 80 ℃ for 12 h to obtain a precursor powder; (6) The precursor obtained in step (5) is mixed with a certain amount of sodium nitrate (Na: TM = 1.05) and ground, and then placed in a muffle furnace for calcination at 800 ℃ for 12 h to obtain black powder-like pyrophosphoric acid zirconium surface-coated modified O3 phase sodium nickel manganese ferrite layered sodium storage composite material.

[0038] The zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese ferrite layered composite material prepared in this example was used as a positive electrode material for a sodium ion battery. The charge and discharge test was carried out at a current density of 240 mA·g -1 After 100 cycles, the discharge specific capacity was still 75.9 mAh·g -1 , and the material had good electrochemical performance.

[0039] <Embodiment 5> A preparation method of a zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese ferrite layered composite material, comprising the following steps: (1) 3 mmol of NiSO4·6H2O, 3.6 mmol of FeSO4·7H2O and 5.4 mmol of MnSO4·H2O were added to 850 mL of deionized water, and stirred at 50°C in a water bath for 10 min to dissolve them; (2) 1 mol·L -1 of ammonia solution was fed into the solution obtained in step (1) at a rate of 10 mL·h -1 , and the solution was stirred vigorously during the feeding process. After the injection was completed, the solution was aged for 5 h; (3) 0.036 mmol of (NH4)2HPO4 was dissolved in 50 mL of solution, and the solution was fed into the solution obtained in step (2) at a rate of 10 mL·h -1 , and the solution was stirred vigorously during the feeding process. After the injection was completed, the solution was aged for 5 h; (4) 0.036 mmol of ZrOCl2·8H2O was dissolved in 50 mL of solution, and the solution was fed into the solution obtained in step (3) at a rate of 10 mL·h -1 , and the solution was stirred vigorously during the feeding process. After the injection was completed, the solution was aged for 5 h; (5) The solution obtained in step (4) was filtered, washed and dried at 80°C for 12 h to obtain a precursor powder; (6) The precursor obtained in step (5) was mixed with a certain amount of sodium nitrate (Na: TM = 1.20) and ground, and then placed in a muffle furnace and calcined at 850°C for 12 h to obtain a black powder of zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese ferrite layered sodium storage composite material.

[0040] The zirconium pyrophosphate surface coated modified O3 phase sodium nickel manganese ferrite layered composite material prepared in this example was used as a positive electrode material for a sodium ion battery. The charge and discharge test was carried out at a current density of 240 mA·g -1 After 100 cycles, the discharge specific capacity was still 77.5 mAh·g -1 , and the material had good electrochemical performance.

[0041] <Comparative Example 1> O3 phase sodium-nickel-manganese-ferrooxide layered sodium storage NaNi 0.25 Fe 0.30 Mn 0.45 The preparation method of O2 material includes the following steps: (1) Add 3 mmol NiSO4·6H2O, 3.6 mmol FeSO4·7H2O and 5.4 mmol MnSO4·H2O to 850 mL of deionized water and stir for 10 min in a 50 ℃ water bath to dissolve them; (2) Use a syringe pump to deliver 1 mol·L -1 ammonia solution at 10 mL·h -1 50 mL of the solution obtained in step (1) is fed into the solution at a constant speed, and vigorous stirring is maintained during the feeding process. After the injection is completed, the solution is aged for 5 h. (3) The solution obtained in step (2) is filtered, washed and dried at 80 °C for 12 h to obtain precursor powder; (4) The precursor obtained in step (3) is mixed and ground with a certain amount of sodium nitrate (Na: TM = 1.05) and then placed in a muffle furnace and calcined at 800 °C for 12 h to obtain a black powdery O3 phase sodium-nickel-manganese-iron sodium storage composite material.

[0042] Taking the product obtained in this comparative example, the material is a nanoparticle with a particle size of 0.5~1 μm, which shortens the migration path of sodium ions during charge-discharge and discharge processes and increases the contact area between the electrode sheet and the electrolyte. Taking the O3-phase sodium-nickel-manganese-iron-oxygen layered material prepared in this comparative example as the positive electrode material for a sodium-ion battery, at 240 mA·g... -1 Under a current density of 74.1 mAh·g, after 100 cycles of charge-discharge testing, the discharge specific capacity reached 74.1 mAh·g. -1 .

[0043] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a zirconium pyrophosphate surface-coated modified O3 phase sodium nickel manganese ferrite layered composite material, characterized in that, The steps include the following: S1. After the transition metal is dissolved evenly in the solvent, an ammonia solution is added and the mixture is aged. The transition metal is a combination of NiSO4·6H2O, FeSO4·7H2O and MnSO4·H2O. S2. Add (NH4)2HPO4 solution to the solution after the reaction in step S1. After the aging reaction is completed, add ZrOCl2·8H2O solution and continue the aging process until the reaction is complete. S3. After the reaction in step S2, the solution is successively filtered, washed and dried to obtain the precursor powder. S4. After mixing the precursor powder with the sodium source, the mixture is then subjected to grinding and calcination to obtain the O3 phase sodium-nickel-manganese ferrite layered composite material with zirconium pyrophosphate surface coating modification.

2. The preparation method according to claim 1, characterized in that, In step S1, based on the amount of substance, NiSO4·6H2O:FeSO4·7H2O:MnSO4·H2O = 3.0~6.0:3.6~7.2:5.4~10; The solvent is deionized water, and the volume of the solvent is 850~950 mL.

3. The preparation method according to claim 2, characterized in that, In step S1, the dissolution of the transition metal is carried out in a water bath at 50~80℃, and the stirring time is 10~15 min; the aging time is 5 h.

4. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the ammonia solution is 1.0~1.2 mol·L⁻¹. -1 The feed rate of the ammonia solution is 10 mL / h. -1 The volume ratio of the mixed solution to the ammonia solution is 17:1 to 19:

1.

5. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the (NH4)2HPO4 solution is 0.00024~0.0024 mmol·L. -1 The feed rate is 10 mL / h -1 ; The concentration of the ZrOCl2·8H2O solution was 0.00024~0.0024 mmol·L. -1 The feed rate is 10 mL / h -1 .

6. The preparation method according to claim 1, characterized in that, In step S2, the time conditions for both the first and second aging reactions are 5 hours.

7. The preparation method according to claim 1, characterized in that, In step S3, the drying temperature is 60~100 ℃ and the drying time is 12 h.

8. The preparation method according to claim 1, characterized in that, In step S4, the sodium source is sodium nitrate, and the stoichiometric ratio of sodium source to transition metal is 1.05~1.20:

1. The calcination temperature is 800~900 ℃ and the time is 10~16 h.

9. The zirconium pyrophosphate surface-modified O3-phase sodium-nickel-manganese ferrite layered composite material obtained by the preparation method according to any one of claims 1-8, characterized in that, The structural formula of the layered composite material is NaNi 0.25 Fe 0.30 Mn 0.45 O2@ZrP2O7.

10. The application of the O3-phase sodium-nickel-manganese-iron-oxygen layered composite material with zirconium pyrophosphate surface coating as described in claim 9 in the field of sodium-ion battery cathode materials.

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