A sodium ion battery positive electrode material and its preparation method and application

Abstract

The present invention belongs to the technical field of sodium ion batteries and discloses a sodium ion battery positive electrode material and a preparation method and application thereof. The general formula of the sodium ion positive electrode material is Na a M b Ni c P d O2; M is at least one of cobalt, iron, and manganese, wherein 0

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a sodium ion battery positive electrode material and a preparation method and application thereof. Background Art

[0002] Sodium-ion batteries have been widely used in the field of energy storage. Sodium-ion batteries have the advantages of abundant resources, low price, and environmental friendliness. In addition, the sodium element will not react with the aluminum current collector to form an alloy, so that the negative electrode can also use cheap aluminum instead of copper as the current collector, further reducing the system cost. However, the large ionic radius and slow kinetic rate of sodium ions have become the main factors restricting the development of sodium storage materials. The specific capacity of the positive electrode material (80-150 mAh g -1 ) is still far lower than the negative electrode material (carbon material: not less than 250mAh g -1 ; Alloy material: 400~600mAh·g -1 ), therefore, the development of high-performance sodium-intercalated cathode materials is the key to improving the specific energy of sodium-ion batteries and promoting their applications.

[0003] At present, there are still many problems that need to be improved in the performance of positive electrode materials for sodium ion batteries. When sodium ions in the positive electrode material are released, it is easy to cause structural collapse and volume change. The electrolyte and the positive electrode active material react, resulting in a decrease in specific capacity, thereby affecting the performance of the battery. Insufficient oxygen vacancies in the positive electrode material lead to the release of oxygen in the lattice, thus affecting the crystal structure.

[0004] Therefore, it is urgent to study a new combined modified positive electrode material and its preparation method, so as to improve the specific capacity and cycle performance of the positive electrode material. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a sodium ion battery positive electrode material and a preparation method and application thereof, wherein the sodium ion positive electrode material has excellent specific capacity and cycle performance.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A sodium ion positive electrode material, the general formula of which is Na a M b Ni c P d O2; wherein M is at least one of cobalt, iron, and manganese; wherein 0 <a<1,0<b<1,0<c<1,1-b-c<d<1。

[0008] Preferably, the general formula of the sodium ion positive electrode material is Na a M b Nic P d O2; said M is at least one of cobalt, iron and manganese; wherein 0.5 <a<1,0<b<0.8,0<c<1,1-b-c<d<1。

[0009] Preferably, the sodium ion positive electrode material is Na 0.4 MnNi 0.06 P 0.04 O2、Na 0.35 CoNi 0.09 P 0.06 O2、Na 0.6 FeNi 0.12 P 0.08 O2、Na 0.7 MnNi 0.17 P 0.13 One of O2.

[0010] A method for preparing a sodium ion positive electrode material comprises the following steps:

[0011] (1) Mix the M salt solution and the sodium salt solution, add a chelating agent, react, and calcine to obtain Na a M b O2;

[0012] (2) The Na a M b O2 and a solvent are mixed, nickel hypophosphite is added, reacted, and calcined to obtain the positive electrode material of the sodium ion battery; the M salt solution is at least one of a manganese salt solution, a cobalt salt solution, and an iron salt solution.

[0013] Preferably, the manganese salt solution is at least one of manganese malate, manganese oxalate and manganese acetate.

[0014] Preferably, the cobalt salt solution is at least one of cobalt acetate, cobalt malate and cobalt oxalate.

[0015] Preferably, the iron salt solution is at least one of ferric citrate, ferric acetate and ferric oxalate.

[0016] Preferably, in step (1), before adding the chelating agent, the step further includes mixing the M salt solution and the sodium salt solution and adding them to a dispersant for dispersion, wherein the dispersant is at least one of ethanol, propanol and formaldehyde resin.

[0017] Preferably, in step (1), the chelating agent is at least one of oxalic acid, oxalic acid and citric acid.

[0018] Preferably, in step (1), the reaction temperature is 40 to 60° C., and the reaction time is 12 to 24 hours.

[0019] Preferably, in step (1), the calcination is performed twice, the temperature of the first calcination is 300-500°C, and the time of the first calcination is 2-4 hours; the temperature of the second calcination is 800-1000°C, and the time of the second calcination is 12-18 hours.

[0020] Preferably, in step (2), the solvent is ethanol.

[0021] Preferably, in step (2), the reaction temperature is 40-60° C., and the reaction time is 4-8 h.

[0022] Preferably, in step (2), the calcination temperature is 500-600° C., and the calcination time is 6-12 hours.

[0023] The reaction equation in step (2) is:

[0024] Ni(H2PO2)2=NiHPO4+PH3↑;

[0025] 2NiHPO4=Ni2P2O7+H2O;

[0026] Ni2P2O7+Na a M b O2=Na a-x-y M b Ni x P y O2+Ni 2-x Na x P 2-y O7, where 0 <x<1,0<y<1。

[0027] A battery comprises the sodium ion positive electrode material.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The sodium ion positive electrode material Na of the present invention a M b Ni c P d Part of the nickel and phosphorus elements in O2 enter the sodium-rich material lattice to occupy the sodium site; it not only reduces the mixing of cations, but also increases the crystal layer spacing, improves the specific capacity and cycle performance of the positive electrode material, and the specific capacity can reach 174mAh / g; the surface is also coated with metal oxides to improve the cycle stability and safety, which not only effectively prevents the increase of total impedance, reduces the charging transfer impedance in the sodium-depleted state, but also prevents the side reactions of the electrolyte and the positive electrode material.

[0030] 2. In the preparation method of the present invention, nickel hypophosphite will produce PH3 under high temperature conditions. PH3 has strong reducing properties and can cause the release of active oxygen in the positive electrode material of the battery to generate more oxygen vacancies; oxygen vacancies are beneficial to buffering the O 2– The migration of lattice oxygen is inhibited, which provides favorable conditions for the next step of generating Ni2P2O7. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM image of the positive electrode material of Example 1 of the present invention;

[0032] Figure 2 1 and 2 are XRD diagrams of the positive electrode materials of Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0034] Example 1

[0035] The sodium ion positive electrode material of this embodiment has the formula Na 0.4 MnNi 0.06 P 0.04 O2.

[0036] The preparation method of the sodium ion positive electrode material of this embodiment has the following specific steps:

[0037] (1) 0.5 mol sodium acetate solution and 1 mol manganese acetate solution were dissolved in 100 mL ethanol, and 1 mol oxalic acid was added and mixed, and the mixture was placed in an environment of 40°C for reaction for 12 h, and then placed in an air atmosphere of 300°C for calcination for 2 h, and cooled to room temperature to synthesize Na 0.5 The intermediate of MnO2 was calcined at 800℃ for 12h in air atmosphere and then cooled to room temperature to obtain the final product Na 0.5 MnO2.

[0038] (2) 4 mol Na 0.5 MnO2 was added to 50 mL of ethanol, and then 1 mol of nickel hypophosphite was added. The mixture was reacted at 40 °C for 4 h until all the ethanol evaporated. The mixture was ground and calcined at 500 °C for 6 h under Ar atmosphere to synthesize the sodium ion battery positive electrode material Na 0.4 MnNi 0.06 P 0.04 O2.

[0039] Example 2

[0040] The sodium ion positive electrode material of this embodiment has the formula Na 0.35 CoNi 0.09 P 0.06 O2.

[0041] The preparation method of the sodium ion positive electrode material of this embodiment has the following specific steps:

[0042] (1) 0.5 mol sodium acetate solution and 1 mol cobalt acetate solution were dissolved in 100 mL ethanol, and 1.2 mol oxalic acid was added and mixed, and the mixture was placed in an environment of 45°C for reaction for 15 h, and then placed in an air atmosphere of 350°C for calcination for 2.5 h, and cooled to room temperature to synthesize Na 0.5 The intermediate of CoO2 was calcined at 800℃ for 12h in air atmosphere and then cooled to room temperature to obtain the final product Na 0.5 CoO2.

[0043] (2) 3 mol Na 0.5 CoO2 was added to 50 mL of ethanol, and then 1 mol of nickel hypophosphite was added. The mixture was reacted at 40 °C for 4 h until the ethanol was completely evaporated. The mixture was ground and calcined at 500 °C for 6 h under Ar atmosphere to synthesize the sodium ion battery positive electrode material Na 0.35 CoNi 0.09 P 0.06 O2.

[0044] Example 3

[0045] The sodium ion positive electrode material of this embodiment has the formula Na 0.6 FeNi 0.12 P 0.08 O2.

[0046] The preparation method of the sodium ion positive electrode material of this embodiment has the following specific steps:

[0047] (1) 0.8 mol sodium acetate solution and 1 mol ferric citrate solution were dissolved in 100 mL ethanol, and 1.5 mol oxalic acid was added and mixed, and the mixture was placed in an environment of 50°C for reaction for 18 h, and then placed in an air atmosphere of 300°C for calcination for 2 h, and cooled to room temperature to synthesize Na 0.8 The intermediate of FeO2 was calcined at 800℃ for 16h in air atmosphere and then cooled to room temperature to obtain the final product Na 0.8 FeO2.

[0048] (2) 2 mol Na 0.8FeO2 was added to 50 mL of ethanol, and then 1 mol of nickel hypophosphite was added. The mixture was reacted at 50 °C for 6 h until the ethanol was completely evaporated. The mixture was ground and calcined at 560 °C for 10 h under Ar atmosphere to synthesize the positive electrode material Na for sodium ion batteries. 0.6 FeNi 0.12 P 0.08 O2.

[0049] Example 4

[0050] The sodium ion positive electrode material of this embodiment has the formula Na 0.7 MnNi 0.17 P 0.13 O2.

[0051] The preparation method of the sodium ion positive electrode material of this embodiment has the following specific steps:

[0052] (1) 1 mol of sodium acetate solution and 1 mol of manganese acetate solution were dissolved in 100 mL of ethanol, and 2 mol of oxalic acid was added and mixed, and the mixture was placed in an environment of 50° C. for reaction for 18 h, and then placed in an air atmosphere of 300° C. for calcination for 2 h, and cooled to room temperature to synthesize the intermediate of NaMnO2, and then calcined at 1000° C. for 18 h in an air atmosphere, and naturally cooled to room temperature to obtain the final product NaMnO2.

[0053] (2) 1 mol of NaMnO2 was added to 50 mL of ethanol, and then 1 mol of nickel hypophosphite was added, and the mixture was reacted at 60 °C for 8 h until the ethanol was completely evaporated, and then ground and calcined at 600 °C for 12 h under Ar atmosphere to synthesize the sodium ion battery positive electrode material Na 0.7 MnNi 0.17 P 0.13 O2.

[0054] Comparative Example 1

[0055] The sodium ion positive electrode material of this comparative example has the formula Na 0.5 MnO2.

[0056] The preparation method of the sodium ion positive electrode material of this comparative example comprises the following specific steps:

[0057] (1) 0.5 mol sodium acetate solution and 1 mol manganese acetate solution were dissolved in 100 mL ethanol, and 1 mol oxalic acid was added and mixed, and the mixture was placed in an environment of 40°C for reaction for 12 h, and then placed in an air atmosphere of 300°C for calcination for 2 h, and cooled to room temperature to synthesize Na 0.5 The intermediate of MnO2 was calcined at 800℃ for 12h in air atmosphere and then cooled to room temperature to obtain the final product Na 0.5 MnO2.

[0058] Analysis of Examples 1-4 and Comparative Example 1:

[0059] The sodium ion positive electrode material, carbon black conductive agent, and polytetrafluoroethylene were mixed and dissolved in deionized water in a mass ratio of 80:10:10 to form a slurry, which was then coated on aluminum foil to form a pole piece. The pole piece was placed in a drying oven and dried at 80°C for 12 hours, and then stamped into a disc by a mold; the disc was cut into a counter electrode pole piece with a diameter of 10 mm; 1.0 mol / L NaClO4 was added to the carbonate as an electrolyte, Celgard2400 was used as a diaphragm, and the battery was assembled in a vacuum glove box under an argon atmosphere. The cycle performance was tested using an electrochemical workstation, and the current density of the test was 150 mA g -1 , tested at 2C rate.

[0060] Table 1: Effect data of Examples 1-4 and Comparative Example 1

[0061]

[0062]

[0063] from Figure 1-Figure 2 Available, Figure 1 This is a SEM image of the positive electrode material of Example 1 of the present invention. Figure 1 It can be seen that the prepared battery positive electrode material is in block shape; Figure 2 The XRD patterns of the positive electrode materials prepared in Example 1 and Comparative Example 1 of the present invention are as follows: Figure 2 It can be seen that nickel and phosphorus elements are doped into the positive electrode material of the battery.

[0064] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A sodium ion positive electrode material, characterized in that: The sodium ion positive electrode material is Na 0.4 MnNi 0.06 P 0.04 O2、Na 0.35 CoNi 0.09 P 0.06 O2、Na 0.6 FeNi 0.12 P 0.08 O2、Na 0.7 MnNi 0.17 P 0.13 One of O2.

2. The method for preparing the sodium ion positive electrode material according to claim 1, characterized in that: The following steps are involved: (1) Mix the M salt solution and the sodium salt solution, add a chelating agent, react, and calcine to obtain Na a M b O2; (2) The Na a M b O2 and a solvent are mixed, nickel hypophosphite is added, reacted, and calcined to obtain the positive electrode material of the sodium ion battery; the M salt solution is at least one of a manganese salt solution, a cobalt salt solution, and an iron salt solution.

3. The preparation method according to claim 2, characterized in that: The manganese salt solution is at least one of manganese malate, manganese oxalate and manganese acetate; the cobalt salt solution is at least one of cobalt acetate, cobalt malate and cobalt oxalate.

4. The preparation method according to claim 2, characterized in that: The iron salt solution is at least one of ferric citrate, ferric acetate and ferric oxalate.

5. The preparation method according to claim 2, characterized in that: In step (1), before adding the chelating agent, the method further comprises mixing the M salt solution and the sodium salt solution and adding the mixture into a dispersant for dispersion, wherein the dispersant is at least one of ethanol, propanol and formaldehyde resin.

6. The preparation method according to claim 2, characterized in that: In step (1), the chelating agent is at least one of oxalic acid, oxalic acid and citric acid.

7. The preparation method according to claim 2, characterized in that: In step (1), the calcination is performed twice, the temperature of the first calcination is 300-500°C, and the time of the first calcination is 2-4 hours; the temperature of the second calcination is 800-1000°C, and the time of the second calcination is 12-18 hours.

8. The preparation method according to claim 2, characterized in that: In step (2), the Na a M b The molar ratio of O2 and nickel hypophosphite is (1-4):

1.

9. A battery, characterized in that: Comprising the sodium ion positive electrode material according to claim 1.

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