High-rate sodium ion battery layered positive electrode material stable in air and water as well as preparation method and application of high-rate sodium ion battery layered positive electrode material

Abstract

The invention discloses a sodium-ion battery layered positive electrode material with high rate and stable air and water as well as a preparation method and application of the sodium-ion battery layered positive electrode material, and belongs to the technical field of sodium-ion batteries. The positive electrode material belongs to a sodium-deficient O3 type layered oxide material, the chemical formula of the positive electrode material is NaxLiaNibFecMnyO2, and x < lt > is greater than or equal to 0.8; and a + b + c + y = 1. According to the invention, the sodium content in the O3-type layered positive electrode material is regulated, the vacancy number in the sodium layer of the O3-phase material is increased, the spacing of the sodium layer is enlarged, the diffusion energy barrier of sodium ions in the O3-phase layered oxide material is reduced, the diffusion kinetics of the sodium ions is obviously improved, and excellent rate capability is obtained. Meanwhile, due to the existence of the sodium vacancy, the formation of residual alkali substances on the surface of the material and the intercalation / exchange behavior of water or carbon dioxide when the material is exposed in the air can be effectively inhibited, and the air and water stability of the O3-phase layered material is improved. The preparation method of the layered positive electrode material provided by the invention is simple and controllable, is suitable for large-scale mass production, and has a good practical application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion batteries, and in particular relates to the preparation and application of a type of high-rate, air- and water-stable layered positive electrode material for sodium ion batteries. Background Art

[0002] At this stage, the global energy shortage problem related to the consumption of fossil fuels is becoming increasingly prominent. For this reason, the development and utilization of clean energy is of vital importance. However, most clean energy is intermittent and volatile, and directly connecting clean energy power generation to the power grid will affect the stability of the power grid. Therefore, the development of efficient energy storage technology is particularly critical. Among the many energy storage technologies, lithium-ion batteries have the advantages of high energy density and long cycle life, and are considered to be one of the most promising energy storage technologies. However, the shortage and rising prices of lithium resources cannot meet the growing demand for energy storage, prompting people to explore and develop alternative energy storage technologies. Sodium-ion batteries are considered to be an ideal complementary technology to lithium-ion batteries due to their advantages such as abundant sodium resources and low cost, and are highly expected in large-scale energy storage applications.

[0003] Among the various components of sodium-ion batteries, the cathode material is one of the most important parts of the entire system and is also a key part that limits the energy density and cycle life of sodium-ion batteries. Among the cathode materials of sodium-ion batteries, layered oxide materials have become one of the most promising cathode materials due to their comprehensive advantages in specific capacity, operating voltage and cost. x TMO 2 It has the advantages of simple preparation process, high specific capacity and environmental friendliness, and has attracted widespread attention from researchers. However, for O3-type materials, sodium ions occupy the octahedral sites between transition metal layers, which means that when sodium ions migrate between octahedra, they need to pass through the tetrahedral sites between two octahedra. This greatly increases the diffusion barrier of sodium ions in the O3 structure, making the O3-type structure have slower sodium ion diffusion kinetics and relatively worse rate performance. In addition, the air and water stability of O3-type layered materials is poor, which not only seriously damages its electrochemical performance and even causes safety accidents such as battery bulging or explosion, but also increases the cost during transportation and storage, seriously limiting its commercial application. Therefore, in order to promote the industrialization of O3-type layered oxide materials for sodium-ion batteries, it is necessary to adopt appropriate modification strategies to improve their kinetic performance and air stability. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of poor rate performance and poor storage stability in air of layered oxide cathode materials for sodium ion batteries, and to provide a class of high-rate, air- and water-stable layered cathode materials for sodium ion batteries, and a preparation method and application thereof. The layered cathode material for sodium ion batteries provided by the present invention has the advantages of high rate, good stability to air and water, and is expected to be applied to commercial sodium ion batteries.

[0005] The technical solution of the present invention is as follows:

[0006] A class of high-rate, air- and water-stable layered cathode materials for sodium-ion batteries with the chemical formula O3-Na x Li a Ni b Fe c Mn y O 2 , the x, a, b, c, y are the stoichiometric ratios of the corresponding elements, wherein 0.8≤x<1, a+b+c+y=1, the positive electrode material belongs to the hexagonal crystal system, the space group is R-3m, and the arrangement of the transition metal layer is ABCABC.

[0007] The method for preparing a type of high-rate, air- and water-stable sodium ion battery layered positive electrode material comprises the following steps:

[0008] (1) high-energy ball milling, uniformly mixing the sodium source, lithium source, nickel source, iron source and manganese source according to the stoichiometric ratio of each metal element in the chemical formula, and ball milling to obtain a precursor;

[0009] (2) high temperature calcination, sintering the precursor obtained in step (1) at high temperature, and then slowly cooling to obtain the sodium ion battery layered positive electrode material.

[0010] Furthermore, in step (1), the sodium source is sodium hydroxide or sodium carbonate; the lithium source is lithium hydroxide or lithium carbonate; the nickel source is nickel acetate or nickel oxide; the iron source is iron acetate or iron trioxide; the manganese source is manganese dioxide or manganese trioxide. The excess of the sodium source is 2% to 10%, preferably 5% to 10%, and the ball milling speed is 300 to 500 rmin. -1 , preferably 350~500rmin -1 The ball milling time is 4-10 h, preferably 6-10 h.

[0011] Furthermore, in step (2), the sintering temperature is 600-1200°C, preferably 800-1000°C, the sintering atmosphere is oxygen or air, the sintering time is 8-24h, preferably 12-24h, and the heating rate is 2-10°C min -1 , preferably 5~10℃min -1 .

[0012] The present invention also provides application of the high-rate, air- and water-stable sodium ion battery layered positive electrode material in a sodium ion battery.

[0013] Furthermore, the sodium ion battery positive electrode material electrode sheet is composed of the following substances: 50% to 96% O3-Na x Li a Ni b Fe c Mn y O 2 , wherein 0.8≤x<1, a+b+c+y=1, the preferred ratio is 80% to 90%; 2% to 30% of conductive carbon black, the preferred ratio is 5% to 15%; 2% to 20% of polyvinylidene fluoride, the preferred ratio is 5% to 15%.

[0014] Furthermore, the negative electrode material is a metal sodium sheet or hard carbon, and the current collector is an aluminum foil.

[0015] Furthermore, the sodium salt in the sodium ion battery electrolyte is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate or sodium trifluoromethanesulfonate.

[0016] Furthermore, the organic solvent in the sodium ion battery electrolyte is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, trimethyl phosphate, dimethyl carbonate, diethyl carbonate, ethylene carbonate and propylene carbonate.

[0017] Furthermore, the molar concentration of sodium salt in the sodium ion battery electrolyte is 0.1 to 5 mol L -1 , preferably 0.4 to 3 mol L -1 .

[0018] Advantages and beneficial effects of the present invention:

[0019] The present invention provides a type of high-rate, air- and water-stable sodium ion battery layered positive electrode material and a preparation method and application thereof. The prepared positive electrode material O3-Na x Li a Ni b Fe c Mn y O 2 The sodium ion battery assembled using the positive electrode material provided by the present invention has high specific capacity, long cycle life and high rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The X-ray powder diffraction patterns of Examples 1-5 and Comparative Example.

[0021] Figure 2It is the constant current intermittent titration test diagram of Example 4 and the comparative example.

[0022] Figure 3 The X-ray powder diffraction pattern of Example 4 after exposure to air and immersion in deionized water.

[0023] Figure 4 The X-ray powder diffraction patterns of the comparative example after exposure in air and immersion in deionized water.

[0024] Figure 5 The figure is a rate performance diagram of the sodium ion battery prepared in Example 4 and the comparative example. DETAILED DESCRIPTION

[0025] The present invention is described in detail and completely below in conjunction with specific embodiments and drawings.

[0026] Unless otherwise specified, the experimental equipment, experimental methods and detection methods described in the following embodiments are all conventional equipment and conventional methods, and the reagents and instruments, unless otherwise specified, can be obtained from commercial channels.

[0027] The purity of the sodium source, lithium source, nickel source, iron source, manganese source, organic solvent and sodium salt used in the examples is not less than 99%.

[0028] Embodiment 1:

[0029] A high-rate, air- and water-stable layered cathode for sodium-ion batteries with O3-Na2O3 as the active material 0.95 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0030] The O3-Na 0.95 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 The detailed synthesis method of the positive electrode material is:

[0031] Weigh 30 mmol of Na according to the stoichiometric ratio of 0.95:0.12:0.2:0.2:0.48 2 CO 3 , Li 2 CO 3 , NiO, Fe 2 O 3 , Mn 2 O 3 , placed in a ball mill and milled on a planetary ball mill at a speed of 350 r min -1After ball milling for 6 h, the dried sample was ground and pressed into tablets at a pressure of 10 MPa on a tablet press. -1 The sample was heated to 900°C at a heating rate of 100°C, sintered for 24 hours, and stored for later use after natural cooling.

[0032] O3-Na 0.95 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 Positive electrode preparation: 80% Na 0.95 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 , 10% conductive carbon black and 10% polyvinylidene fluoride (PVDF) are mixed evenly, and an appropriate amount of N-methylpyrrolidone is added to make a slurry, which is then coated on an aluminum foil current collector and transferred to a vacuum drying oven and dried at 80°C for 12 hours. It is then cut into positive electrode sheets of appropriate size for use.

[0033] Preparation of electrolyte: Sodium perchlorate was selected as sodium salt, and a mixed solvent of ethylene carbonate, propylene carbonate and fluoroethylene carbonate in a volume ratio of 1:1:1 was selected as electrolyte solvent. The corresponding amount of sodium salt was dissolved in the electrolyte solvent and stirred thoroughly to obtain a concentration of 1 mol L -1 of electrolyte.

[0034] Battery assembly and testing: The prepared positive electrode, electrolyte, sodium metal sheet and other components were assembled into sodium ion button cells, and the rate performance was tested with a test voltage range of 2.0 to 4.3 V.

[0035] Embodiment 2:

[0036] A high-rate, air- and water-stable layered cathode for sodium-ion batteries with O3-Na2O3 as the active material 0.90 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0037] The O3-Na 0.90 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 The detailed synthesis method of the positive electrode material is:

[0038] Weigh 30 mmol of Na according to the stoichiometric ratio of 0.90:0.12:0.2:0.2:0.48 2 CO 3 , Li 2 CO 3 , NiO, Fe 2 O 3 , Mn 2 O 3 , placed in a ball mill and milled on a planetary ball mill at a speed of 350 r min -1 After ball milling for 6 h, the dried sample was ground and pressed into tablets at a pressure of 10 MPa on a tablet press. -1 The sample was heated to 900°C at a heating rate of 100°C, sintered for 24 hours, and stored for later use after natural cooling.

[0039] Na 0.90 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 Positive electrode preparation: The method is the same as in Example 1, except that the positive electrode active material is Na 0.90 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2。

[0040] The preparation of electrolyte, battery assembly and rate performance test are the same as those in Example 1.

[0041] Embodiment 3:

[0042] A high-rate, air- and water-stable layered cathode for sodium-ion batteries with O3-Na2O3 as the active material 0.85 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0043] The O3-Na 0.85 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 The detailed synthesis method of the positive electrode material is:

[0044] Weigh 30 mmol of Na according to the stoichiometric ratio of 0.85:0.12:0.2:0.2:0.48 2 CO 3 , Li 2 CO3 , NiO, Fe 2 O 3 , Mn 2 O 3 , placed in a ball mill and milled on a planetary ball mill at a speed of 350 r min -1 After ball milling for 6 h, the dried sample was ground and pressed into tablets at a pressure of 10 MPa on a tablet press. -1 The sample was heated to 900°C at a heating rate of 100°C, sintered for 24 hours, and stored for later use after natural cooling.

[0045] O3-Na 0.85 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 Positive electrode preparation: The method is the same as in Example 1, except that the positive electrode active material is O3-Na 0.85 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2。

[0046] The preparation of electrolyte, battery assembly and rate performance test are the same as those in Example 1.

[0047] Embodiment 4:

[0048] A high-rate, air- and water-stable layered cathode for sodium-ion batteries with O3-Na2O3 as the active material 0.80 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0049] The O3-Na 0.80 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 The detailed synthesis method of the positive electrode material is:

[0050] Weigh 30 mmol of Na according to the stoichiometric ratio of 0.80:0.12:0.2:0.2:0.48 2 CO 3 , Li 2 CO 3 , NiO, Fe 2 O 3 , Mn 2 O 3, placed in a ball mill and milled on a planetary ball mill at a speed of 350 r min -1 After ball milling for 6 h, the dried sample was ground and pressed into tablets at a pressure of 10 MPa on a tablet press. -1 The sample was heated to 900°C at a heating rate of 100°C, sintered for 24 hours, and stored for later use after natural cooling.

[0051] The prepared cathode material was subjected to X-ray powder diffraction (XRD) test. The test target was a copper target, the scanning angle range was 10-80°, and the scanning speed was 5°min -1 The prepared cathode material was exposed to ambient air for 1 day and subjected to an XRD test under the same test conditions as above; the prepared cathode powder was immersed in deionized water for 30 min and subjected to an XRD test under the same test conditions as above.

[0052] O3-Na 0.80 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 Positive electrode preparation: The method is the same as in Example 1, except that the positive electrode active material is O3-Na 0.80 Li 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0053] The preparation of electrolyte, battery assembly and rate performance test are the same as those in Example 1.

[0054] In the constant current intermittent titration test, the battery is charged and discharged at a constant current density of 0.1C for 10 minutes in the voltage range of 2.0 to 4.3V, followed by relaxation for 30 minutes, and this cycle is repeated.

[0055] Comparative Example

[0056] A layered positive electrode for sodium ion batteries, wherein the active material is O3-NaLi 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0057] The O3-NaLi 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 The detailed synthesis method is:

[0058] Weigh 30 mmol of Na according to the stoichiometric ratio of 1:0.12:0.2:0.2:0.48 2 CO 3 , Li 2 CO 3 , NiO, Fe 2 O 3 , Mn 2 O 3 , placed in a ball mill and milled on a planetary ball mill at a speed of 350 r min -1 After ball milling for 6 h, the dried sample was ground and pressed into tablets at a pressure of 10 MPa on a tablet press. -1 The sample was heated to 900°C at a heating rate of 100°C, sintered for 24 hours, and stored for later use after natural cooling.

[0059] The prepared cathode material was subjected to XRD test. The test target was a copper target, the scanning angle range was 10-80°, and the scanning speed was 5°min. -1 At the same time, the prepared positive electrode material was exposed to ambient air for 1 day and subjected to an XRD test, and the test conditions were consistent with the above; the prepared positive electrode material was immersed in deionized water for 30 minutes and subjected to an XRD test, and the test conditions were consistent with the above.

[0060] O3-NaLi 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 Positive electrode preparation: The method is the same as in Example 1, except that the positive electrode active material is NaLi 0.12 Ni 0.2 Fe 0.2 Mn 0.48 O 2 .

[0061] In the constant current intermittent titration test, the battery is charged and discharged at a constant current density of 0.1C for 10 minutes in the voltage range of 2.0 to 4.3V, followed by relaxation for 30 minutes, and this cycle is repeated.

[0062] Figure 1 The XRD patterns of Examples 1-4 and Comparative Examples are shown in Table 1. Figure 1 It can be seen that Examples 1-4 and the comparative example all have an O3-type layered structure, which can match the standard PDF card. The weak peak in the range of 17-20° can be attributed to the LiTM formed in the transition metal layer. 6 Superstructure.

[0063] Figure 2 It is the constant current intermittent titration test diagram of Example 4 and the comparative example. Figure 2It can be seen that the sodium ion battery layered material prepared by the present invention exhibits a higher sodium ion diffusion coefficient in the voltage range of 2 to 4.3 V, and its diffusion coefficient value is significantly greater than that of the comparative example, and its kinetic performance is better than that of the comparative example.

[0064] Figure 3 The XRD diagram of Example 4 after being exposed to air for 1 day and soaked in deionized water for 30 minutes. As can be seen from the figure, the XRD diagram of the positive electrode material prepared by the present invention can well correspond to the PDF card of the O3 phase, indicating that the sample of the present invention has an O3-type layered structure. When it is exposed to ambient air for one day and soaked in water for 30 minutes, it can be found that no miscellaneous peaks appear on the XRD spectrum, and the position of the diffraction peak of the (003) crystal plane is basically not offset, indicating that after storage in air or water treatment, its interlayer spacing has basically not changed, showing that the material prepared by the present invention has excellent air and water stability.

[0065] Figure 4 The XRD diagram of the comparative example after being exposed to air for 1 day and soaked in deionized water for 30 minutes. As can be seen from the figure, the comparative example also has an O3-type layered structure and can match the PDF card. After being exposed to ambient air for one day, it can be found that its (003) peak has shifted to a large extent, and the intensity is significantly reduced, indicating that the interlayer spacing has increased. In addition, an impurity peak is found at about 15.5°, indicating that other impurities are generated in the air. After the comparative example is soaked in water for 30 minutes, it can be found that the diffraction peak intensity of its different crystal planes is significantly reduced, and it is almost difficult to distinguish the crystal plane to which it belongs. In addition, the (003) peak is further shifted to a low angle, indicating that the interlayer spacing is further increased and the structure is further damaged, showing that the comparative example has relatively poorer air and water stability.

[0066] Figure 5 The figure is a rate performance diagram of the sodium ion battery prepared in Example 4 and the comparative example. It can be seen from the figure that when the current density changes at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C, Example 4 shows a higher discharge specific capacity than the comparative example, especially at a high rate of 10C. The difference is more obvious. Example 4 prepared by the present invention shows a more excellent rate performance.

[0067] It should be noted that the above-described embodiments are only part of the embodiments of the present invention and are not intended to limit the present invention. x Li a Ni b Fe c Mn y O 2The implementation method is described, but the selection of materials and process conditions in the examples do not cover all the selection ranges of the technical solution of the present invention. The implementation method only describes the selection of the stoichiometric ratio of sodium element 0.8≤x<1, and the stoichiometric ratio of sodium, lithium, nickel, iron and manganese elements in the material is a+b+c+y=1. In addition, the sodium source, lithium source, nickel source, iron source and manganese source in the preparation method, as well as ball milling and high-temperature sintering conditions, the percentage of active materials, conductive carbon black, and polyvinylidene fluoride in sodium ion batteries, sodium salt and concentration of electrolyte in sodium ion batteries, and organic solvents can all be selected within the scope of the technical solution of the present invention, and the implementation of other specific materials and process conditions within the protection scope of the technical solution has the same technical effect as Examples 1-5. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-rate, air- and water-stable layered cathode material for sodium-ion batteries, characterized in that: The positive electrode material is a sodium ion battery O3 type layered material Na x Li a Ni b Fe c Mn y O2, wherein x, a, b, c, and y are chemical ratios of corresponding elements, wherein 0.8≤x<1, and a+b+c+y=1.

2. The method for preparing the high-rate, air- and water-stable layered positive electrode material for sodium ion batteries according to claim 1, characterized in that: The following steps are involved: (1) mixing a sodium source, a lithium source, a nickel source, an iron source, and a manganese source in proportion, and ball milling to obtain a precursor; (2) The precursor obtained in step (1) is subjected to high temperature sintering, and then slowly cooled to obtain the layered positive electrode material for the sodium ion battery.

3. The preparation method according to claim 2, characterized in that: In step (1), the sodium source is selected from sodium hydroxide or sodium carbonate; the lithium source is selected from lithium hydroxide or lithium carbonate; the nickel source is selected from nickel acetate or nickel oxide; the iron source is selected from ferric acetate or ferrous oxide; and the manganese source is selected from manganese dioxide or manganese trioxide.

4. The preparation method according to claim 2, characterized in that: In step (1), the excess amount of sodium source is 2% to 10%, and the ball milling speed is 300 to 500 rmin. -1 , the ball milling time is 2-10h.

5. The preparation method according to claim 2, characterized in that: In step (2), the sintering temperature is 600-1200°C, the sintering atmosphere is oxygen or air, the sintering time is 8-24h, and the heating rate is 2-10°C min -1 .

6. Application of the high-rate, air- and water-stable layered positive electrode material for sodium-ion batteries according to claim 1.

7. The use according to claim 6, characterized in that: Active materials Na in layered oxide cathodes for sodium-ion batteries x Li a Ni b Fe c Mn y The mass percentage of O2 is 50% to 96%, the mass percentage of conductive carbon black is 2% to 30%, and the mass percentage of polyvinylidene fluoride is 2% to 20%.

8. The use according to claim 6, characterized in that: The sodium salt in the sodium ion battery electrolyte is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bistrifluoromethanesulfonimide, and sodium trifluoromethanesulfonate.

9. The use according to claim 6, characterized in that: The organic solvent in the sodium ion battery electrolyte is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, trimethyl phosphate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, fluoroethylene carbonate, and propylene carbonate.

10. The use according to claim 6, characterized in that: The molar concentration of sodium salt in the electrolyte of sodium ion battery is 0.1~5molL -1 .

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