Sodium-ion battery positive electrode layered material simultaneously doped and coated with metal elements as well as preparation method and application of sodium-ion battery positive electrode layered material

Abstract

The invention belongs to the technical field of material synthesis and energy, and particularly discloses a sodium-ion battery positive electrode layered material simultaneously doped and coated with metal elements, and a preparation method and application of the sodium-ion battery positive electrode layered material. The chemical formula of the material is NaxNiaMbMn1-a-bO2 / yMO, wherein M is one or more of copper, iron, magnesium, zirconium, zinc, aluminum, molybdenum and cobalt. According to the material prepared by the method, the M element exists in a P2 phase structure and also exists on the surface of the material in an oxide form. The method is low in process cost, simple in step and easy to operate, the reaction process of oxidizing the metal powder and doping the metal powder into the material is controlled according to the principle that the metal powder is doped and coated with the metal oxide in one step and activated carbon reacts with oxygen in one step to generate carbon monoxide, and redundant carbon is removed through the oxygen atmosphere; the prepared material not only can expand a sodium ion diffusion channel, but also can improve the rate capability and the cycling stability of the material.

Description

Technical Field

[0001] The invention belongs to the field of material synthesis and energy technology, and specifically relates to a sodium ion battery positive electrode layered material that is simultaneously doped and coated with metal elements, and a preparation method and application thereof. Background Art

[0002] In recent years, lithium-ion batteries, as a representative of energy storage technology, have been widely used in portable electronic devices, energy storage power stations, and electric vehicles, resulting in a rapid increase in their production and consumption. However, lithium resources are limited and it is difficult to meet the rapid growth in market demand for lithium-ion batteries. Therefore, the development of new energy storage technologies is particularly important. Studies have shown that sodium-ion batteries have a similar electrochemical reaction mechanism to lithium-ion batteries and have the potential to become a promising alternative.

[0003] However, the current positive electrode materials for sodium ion batteries face problems such as irreversible phase change during the charge and discharge process and insufficient water-air stability, which greatly restrict the large-scale industrial production of layered positive electrode materials. In view of the above problems, technicians in this field need to develop a new positive electrode material for sodium ion secondary batteries, which has a high initial discharge specific capacity, good rate performance, cycle performance and good water-air stability. In addition, the existing coating is generally carried out in two steps, and repeated operations and calcinations in this process will consume a lot of energy, and the requirements for equipment and sites will be further increased. Summary of the invention

[0004] In view of the problems that the positive electrode of sodium ion batteries currently has, such as poor water-air stability, irreversible phase change during the cycle, and easy release of metal elements in the material, the present invention uses metal powder as raw material and introduces activated carbon to control the reaction process of the metal powder, and designs and prepares a sodium ion battery positive electrode layered material that is doped and coated with metal elements as the positive electrode of the sodium ion battery. The method is simple in process, and the physical and chemical properties of the product are uniform. The physical properties of the material are stabilized to a certain extent by doping and coating. The presence of the coating layer isolates the contact between the core material and the outside world, thereby improving the water-air stability. At the same time, the incorporation of metal elements expands the ion channel, which is beneficial to the rate performance of the material and improves the cycle stability of the material.

[0005] To achieve the above object, the present invention proposes a sodium ion battery positive electrode layered material that is doped and coated with metal elements, which has a core-shell structure, wherein the core is a P2-type manganese-based layered oxide, the space group is P63 / mmc, and the surface is a metal oxide coating layer; the chemical formula of the positive electrode layered material is: Na x Ni a M b Mn 1-a-bO2 / yMO, 0.5≤x≤0.80, 0.1≤a≤0.4, 0<b≤0.2, 0.4≤1-ab≤0.8, 0<y≤0.2, M is a metal element, including one or more of copper, iron, magnesium, zirconium, zinc, aluminum, molybdenum and cobalt; the coating layer is a combination of one or more of copper oxide, iron oxide, magnesium oxide, zirconium oxide, zinc oxide, aluminum oxide, molybdenum oxide and cobalt oxide.

[0006] The present invention also proposes a method for preparing the above-mentioned sodium ion battery positive electrode layered material doped and coated with metal elements, comprising the following steps:

[0007] (1) According to the stoichiometric ratio, a sodium source, a nickel source, a manganese source, a metal powder and activated carbon are placed in a ball mill, a certain amount of dispersant is added, and the raw materials are mixed uniformly by ball milling. The ball milling time is 1 to 10 hours and the rotation speed is 300 to 600 rpm;

[0008] (2) The ball-milled raw material mixture is pressed into a sheet and then calcined in a tubular furnace at a temperature of 850-1000° C. The mixture is kept warm at this temperature in an atmosphere of first nitrogen and then oxygen, and then naturally cooled to room temperature to obtain a sodium ion battery positive electrode layered material.

[0009] Preferably, the sodium source in step (1) is a composite of sodium nitrate and sodium carbonate, wherein the molar ratio of sodium nitrate to sodium carbonate is 0 to 1, and the sodium salt is added at 101 wt% to 110 wt% of the stoichiometric ratio.

[0010] Preferably, the nickel source in step (1) is selected from one or more of the following compounds: nickel oxide, nickel nitrate, nickel carbonate, nickel acetate, nickel hydroxide, nickel acetate; the manganese source is selected from one or more of the following compounds: manganese dioxide, manganese nitrate, manganese carbonate, manganese acetate, manganese hydroxide, manganese acetate.

[0011] Preferably, the metal powder in step (1) comprises one or more of copper, iron, magnesium, zirconium, zinc, aluminum, molybdenum, cobalt, or alloys of the above elements; the particle size D of the metal powder is 50 Satisfy 10nm<D 50 <100nm; sphericity of metal powder Φ≥0.85; impurity content of metal powder <1%; metal powder mass accounts for 1% to 20% of the total mass of the material. M element exists both in the P2 phase structure and on the surface of the material in the form of oxide. M element replaces nickel or manganese in the lattice according to the ionic radius and valence state, replaces nickel in the lattice of copper, iron, magnesium, and zinc, and replaces manganese in the lattice of zirconium, aluminum, molybdenum, and cobalt.

[0012] Preferably, the impurity content of the activated carbon used in step (1) is less than 0.2%, and the activated carbon is one or a combination of graphite, coal-based activated carbon, wood-based activated carbon, fruit shell and core-based activated carbon, and resin-based activated carbon, and the molar ratio of the activated carbon to the metal powder M is 0.1 to 10:1.

[0013] Preferably, the dispersant in step (1) is one or a combination of ethanol, water, and acetone, wherein the volume ratio of the dispersant to the mixed raw material mass is 1.5 to 3:1, wherein the volume unit is milliliter and the mass unit is gram.

[0014] Preferably, in step (2), the temperature is raised to 850-1000° C. at a rate of 1-10° C. / min, and after being kept warm for 1-20 hours under a nitrogen atmosphere, the atmosphere is replaced with oxygen and kept warm for another 1-20 hours.

[0015] Preferably, the particle size D of the sodium ion battery positive electrode layered material is 50 Satisfy 0.5μm<D 50 <50μm, wherein the thickness of the metal oxide coating layer is between 4nm and 20nm.

[0016] The present invention also proposes to apply the above-mentioned sodium ion battery positive electrode layered material that is simultaneously doped and coated with metal elements to a sodium ion battery.

[0017] The technical solution adopted by the present invention has the following advantages compared with the prior art:

[0018] 1. The present invention can obtain the doped and coated material by one-step calcination, with a simple process and low equipment requirements.

[0019] 2. The present invention controls the reaction process of metal powder by introducing activated carbon. The activated carbon first reacts with oxygen to generate carbon monoxide, thereby controlling the oxidation process of metal powder and the reaction process of doping into the material. The residual activated carbon is removed by introducing oxygen to obtain a one-step doped and coated material.

[0020] 3. Doping and coating are helpful to improve the transmission speed of electrode materials, which not only improves the material's cycle performance, inhibits irreversible phase change, but also enhances the material's water-air stability and improves the material's stability.

[0021] 4. The sodium ion battery positive electrode layered material doped and coated with metal elements prepared by the present invention has strong cycle performance. -1 The reversible capacity retention rate reaches over 80% after 100 cycles at a high current density. At the same time, the capacity retention rate reaches over 80% after being placed in air for 14 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1is Na in Example 1 0.67 Ni 0.23 Cu 0.1 Mn 0.67 XRD pattern of O2 / 0.05CuO.

[0023] Figure 2 is Na in Example 1 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 / 0.05CuO material at 12mAg -1 Charge and discharge curves at different current densities.

[0024] Figure 3 is Na in Example 1 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 / 0.05CuO material at 120mAg -1 Long cycle performance at different current densities.

[0025] Figure 4 is Na in Comparative Example 1 0.67 Ni 0.23 Cu 0.1 Mn 0.67 XRD pattern of O2.

[0026] Figure 5 is Na in Comparative Example 1 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 material at 12mAg -1 Charge and discharge curves at different current densities.

[0027] Figure 6 is Na in Comparative Example 1 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 material at 120mAg -1 Long cycle performance at different current densities. DETAILED DESCRIPTION

[0028] The present invention will be further described below by way of examples, but is not limited thereto.

[0029] Example 1

[0030] A method for preparing a sodium ion battery positive electrode layered material doped and coated with metal elements, wherein the chemical formula is Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67O2 / 0.05CuO, the specific steps are as follows:

[0031] (1) According to the stoichiometric ratio, 0.651 g of sodium carbonate, 0.08908 g of sodium nitrate (3% excess), 0.33 g of nickel oxide, 1.11 g of manganese dioxide, 0.222 g of copper powder and 0.042 g of graphite were placed in a ball mill, 6.11 ml of ethanol was added as a dispersant, and the raw materials were mixed uniformly by ball milling for 7 h at a speed of 500 rpm;

[0032] (2) The ball-milled raw material mixture is pressed into a sheet and placed in a tubular furnace, kept at 900°C for 15 h, with a heating rate of 5°C / min, and calcined in nitrogen for 14 h, then oxygen for 1 h, and then naturally cooled to room temperature to obtain the product.

[0033] from Figure 1 It can be seen that the material has characteristic diffraction peaks of the P2 phase (space group P63 / mmc) and also contains characteristic peaks of copper oxide. Figure 2 for Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 The charge and discharge curves of the half-cell with O2 / 0.05CuO as the positive electrode material in the range of 2.0-4.25V at 12mAg -1 The first cycle discharge capacity at the current density is 108.33 mAh g -1 . 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 / 0.05CuO at 120mA g -1 The first cycle discharge capacity at the current density and the discharge capacity after 100 cycles are 96.06 mAh g -1 and 79.87mAh g -1 , the capacity retention rate was 83.1%. After being placed in air for 14 days, at 12mA g -1 The first cycle discharge capacity at the current density is 96.12 mAh g -1 , the capacity retention rate is 88.72%.

[0034] Example 2

[0035] A method for preparing a sodium ion battery positive electrode layered material doped and coated with metal elements, wherein the chemical formula is Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 / 0.1CuO, the specific steps are as follows:

[0036] (1) According to the stoichiometric ratio, 0.638 g of sodium carbonate, 0.0856 g of sodium nitrate (1% excess), 0.33 g of nickel oxide, 1.11 g of manganese dioxide, 0.322 g of copper powder, and 0.24 g of fruit shell and core activated carbon were placed in a ball mill, 1 ml of glycerol and 4.45 ml of water were added as dispersants, and the raw materials were mixed uniformly by ball milling. The ball milling time was 3 h and the rotation speed was 550 rpm;

[0037] (2) The ball-milled raw material mixture is pressed into a sheet and placed in a tube furnace, kept at 900°C for 12 h, with a heating rate of 5°C / min, and calcined in nitrogen for 10 h, then oxygen for 2 h, and then naturally cooled to room temperature to obtain the product.

[0038] Figure 5 for Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 The charge and discharge curves of the half-cell with O2 / 0.1CuO as the positive electrode material in the range of 2.0-4.25V at 12mAg -1 The first cycle discharge capacity at the current density is 105.43 mAh g -1 . 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 / 0.1CuO at 120mAg -1 The first cycle discharge capacity at the current density and the discharge capacity after 100 cycles are 92.05 mAh g -1 and 78.99mAh g -1 , the capacity retention rate was 85.8%. After being placed in air for 14 days, at 12mAg -1 The first cycle discharge capacity at the current density is 96.87 mAh g -1 , the capacity retention rate is 91.88%.

[0039] Example 3

[0040] A method for preparing a sodium ion battery positive electrode layered material doped and coated with metal elements, wherein the chemical formula is Na 0.67 Ni 0.18 Zn 0.1 Cu 0.05 Mn 0.67 O2 / 0.05ZnO, the specific steps are as follows:

[0041] (1) According to the stoichiometric ratio, 0.6088 g of sodium carbonate, 0.1781 g of sodium nitrate (5% excess), 0.2576 g of nickel oxide, 1.11 g of manganese dioxide, 0.061 g of copper, 0.324 g of zinc powder, and 0.144 g of resin-based activated carbon were placed in a ball mill, 6 ml of ethanol and 0.7 ml of water were added as dispersants, and the raw materials were mixed uniformly by ball milling for 5 h at a speed of 450 rpm;

[0042] (2) The ball-milled raw material mixture was pressed into a sheet and placed in a tube furnace, kept at 950°C for 15 h, with a heating rate of 5°C / min, and calcined in nitrogen for 14 h, then oxygen for 1 h, and then naturally cooled to room temperature to obtain the product. 0.67 Ni 0.18 Zn 0.1 Cu 0.05 Mn 0.67 O2 / 0.05ZnO at 12mAg -1 The first cycle discharge capacity at the current density is 102.54 mAh g -1 At 120mAg -1 The first cycle discharge capacity at the current density and the discharge capacity after 100 cycles are 91.51 mAh g -1 and 80.57mAh g -1 , the capacity retention rate was 88.04%. After being placed in air for 14 days, at 12mAg -1 The first cycle discharge capacity at the current density is 87.159 mAh g -1 , the capacity retention rate is 85%.

[0043] Comparative Example 1

[0044] A method for preparing a sodium ion battery positive electrode layered material doped and coated with metal elements, wherein the chemical formula is Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 specific steps are as follows:

[0045] (1) According to the stoichiometric ratio, 0.7164 sodium carbonate (5% excess), 0.33g nickel oxide, 1.11g manganese dioxide and 0.122g copper powder were placed in a ball mill, 4.55ml ethanol was added as a dispersant, and the raw materials were mixed uniformly by ball milling for 5 hours at a speed of 450 rpm;

[0046] (2) The ball-milled raw material mixture was pressed into a sheet and placed in a tube furnace, kept at 900°C for 15 h at a heating rate of 5°C / min in an oxygen atmosphere, and then naturally cooled to room temperature to obtain the product.

[0047] The Na prepared in this example 0.67 Ni 0.23 Cu 0.1 Mn 0.67 The XRD pattern of O2 material is as follows Figure 4 As shown, from Figure 4 It can be seen that the material has a characteristic diffraction peak of P2 phase (space group P63 / mmc). Figure 5 for Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 The charge and discharge curves of the half-cell with O2 as the positive electrode material in the range of 2.0-4.25V at 12mA g -1 The first cycle discharge capacity at the current density is 121.16 mAh g -1 . 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O2 at 120mAg -1 The first cycle discharge capacity at the current density and the discharge capacity after 100 cycles are 97.85 mAh g -1 and 65.62mAh g -1 After being placed in air for 14 days, the capacity retention rate was 67.06%. -1 The first cycle discharge capacity at the current density is 99.351 mAh g -1 , the capacity retention rate is 81.9%.

[0048] Comparative Example 2

[0049] Solid-phase method for preparing Na 0.67 Ni 0.33 Mn 0.67 O2 material, the specific steps are as follows:

[0050] (1) According to the stoichiometric ratio, 0.72 g of sodium carbonate (5% excess), 0.4756 g of nickel oxide and 1.12 g of manganese dioxide were placed in a ball mill, 4.63 ml of ethanol was added as a dispersant, and the raw materials were mixed uniformly by ball milling. The ball milling time was 10 h and the rotation speed was 500 rpm;

[0051] (2) The ball-milled raw material mixture was pressed into a sheet and placed in a tube furnace, kept at 920°C for 10 h at a heating rate of 5°C / min in an oxygen atmosphere, and then naturally cooled to room temperature to obtain the product. 0.67 Ni 0.33 Mn 0.67 O2 at 12mA g -1 The first cycle discharge capacity at the current density is 152 mAh g -1At 120mA g -1 The first cycle discharge capacity at the current density and the discharge capacity after 100 cycles are 110.05 mAh g -1 and 45.2mAh g -1 , the capacity retention rate was 41%. After being placed in air for 14 days, at 12mA g -1 The first cycle discharge capacity at the current density is 60.53 mAh g -1 , the capacity retention rate is 39.88%.

[0052] Table 1 Electrochemical properties of cathode materials prepared under different technical conditions

[0053]

[0054]

Claims

1. A sodium ion battery positive electrode layered material doped and coated with metal elements, characterized in that: The positive electrode layered material is a core-shell structure, the core of which is a P2-type manganese-based layered oxide, the space group is P63 / mmc, and the surface is a metal oxide coating layer; the chemical formula of the positive electrode layered material is: Na x Ni a M b Mn 1-a-b O2 / yMO, 0.5≤x≤0.80, 0.1≤a≤0.4, 0<b≤0.2, 0.4≤1-ab≤0.8, 0<y≤0.2, M is a metal element, including one or more of copper, iron, magnesium, zirconium, zinc, aluminum, molybdenum and cobalt; the coating layer is a combination of one or more of copper oxide, iron oxide, magnesium oxide, zirconium oxide, zinc oxide, aluminum oxide, molybdenum oxide and cobalt oxide.

2. A method for preparing the sodium ion battery positive electrode layered material doped and coated with metal elements as claimed in claim 1, characterized in that: The following steps are involved: (1) According to the stoichiometric ratio, a sodium source, a nickel source, a manganese source, a metal powder and activated carbon are placed in a ball mill, a certain amount of dispersant is added, and the raw materials are mixed uniformly by ball milling. The ball milling time is 1 to 10 hours and the rotation speed is 300 to 600 rpm; (2) The ball-milled raw material mixture is pressed into a sheet and then calcined in a tubular furnace at a temperature of 850-1000° C. The mixture is kept warm at this temperature in an atmosphere of first nitrogen and then oxygen, and then naturally cooled to room temperature to obtain a sodium ion battery positive electrode layered material.

3. The method according to claim 2, characterized in that: The sodium source in step (1) is a composite of sodium nitrate and sodium carbonate, wherein the molar ratio of sodium nitrate to sodium carbonate is 0-1, and the sodium salt is added at 101wt%-110wt% of the stoichiometric ratio.

4. The method according to claim 2, characterized in that: The nickel source in step (1) is selected from one or more of the following compounds: nickel oxide, nickel nitrate, nickel carbonate, nickel acetate, nickel hydroxide, and nickel acetate; the manganese source is selected from one or more of the following compounds: manganese dioxide, manganese nitrate, manganese carbonate, manganese acetate, manganese hydroxide, and manganese acetate.

5. The method according to claim 2, characterized in that: The metal powder in step (1) includes one or more of copper, iron, magnesium, zirconium, zinc, aluminum, molybdenum, and cobalt, or an alloy of the above elements; the particle size D of the metal powder is 50 Satisfy 10nm<D 50 <100nm; the sphericity of the metal powder Φ≥0.85; the impurity content of the metal powder <0.5%; the mass of the metal powder accounts for 1% to 20% of the total mass of the material.

6. The method according to claim 2, characterized in that: The impurity content of the activated carbon used in step (1) is less than 0.2%, and the activated carbon is one or a combination of graphite, coal-based activated carbon, wood-based activated carbon, fruit shell and core-based activated carbon, and resin-based activated carbon, and the molar ratio of the activated carbon to the metal powder is 0.1 to 10:

1.

7. The method according to claim 2, characterized in that: The dispersant in step (1) is one or a combination of ethanol, water, and acetone, wherein the volume ratio of the dispersant to the mixed raw material mass is 1.5 to 3:1, wherein the volume unit is milliliter and the mass unit is gram.

8. The method according to claim 2, characterized in that: In step (2), the temperature is raised to 850-1000° C. at a rate of 1-10° C. / min, and after being kept warm for 1-20 hours under a nitrogen atmosphere, the atmosphere is replaced with oxygen and kept warm for another 1-20 hours.

9. The method according to claim 2, characterized in that: The particle size D of the sodium ion battery positive electrode layered material 50 Satisfy 0.5μm<D 50 <50μm, wherein the thickness of the metal oxide coating layer is between 4nm and 20nm.

10. The sodium ion battery positive electrode layered material simultaneously doped and coated with metal elements as claimed in claim 1 is applied to a sodium ion battery.

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