Sodium-ion battery positive electrode material, modification method, sodium-ion battery and application

Abstract

The invention provides a sodium-ion battery positive electrode material, a modification method, a sodium-ion battery and application, the modification method comprises the following steps: stirring the sodium-ion battery positive electrode material in a modification solution, carrying out suction filtration, drying, and carrying out high temperature sintering to obtain the modified sodium-ion battery positive electrode material, wherein the modified solution comprises phytic acid and sulfoxide. The modification method provided by the invention can solve the technical problems of poor capacity, poor air stability and low rate of the sodium battery positive electrode material in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of modification of sodium-ion batteries, and more particularly, to a cathode material for sodium-ion batteries and a modification method thereof, a sodium-ion battery and an application thereof. Background Art

[0002] Due to the scarcity of lithium resources and the increasing demand in the field of power batteries, the price of raw lithium compounds has been rising continuously. At the same time, the safety of lithium-ion secondary batteries is low. Therefore, the development of secondary batteries with new ion systems has become the focus of research in recent years. Sodium and lithium are in the same main group, with similar chemical properties. Moreover, sodium has rich reserves and low prices, which makes sodium-ion batteries a feasible alternative to lithium-ion batteries for energy storage applications.

[0003] Sodium-ion battery cathode layer oxide materials have advantages such as stable structure and can provide the largest dimensional transmission channels for sodium ions. However, they are unstable in air storage, manifested as capacity decay, increased overpotential, and the formation of alkaline substances. Higher iron content results in stronger reaction with air for 03-type materials, leading to sodium dissolution and the formation of carbonates on the surface. During the air degradation process, sodium carbonate will be generated on the particle surface, which is the result of the reaction between lattice Na + and carbon dioxide in the air. At the same time, water molecules play an important role in accelerating the dissolution of Na + from the lattice through Na / H + exchange, resulting in the formation of hydrated phases or structural transitions. Therefore, finding innovative strategies to optimize the manufacturing process and minimize air protection costs is crucial for improving the commercial feasibility and widespread adoption of sodium-ion batteries.

[0004] In view of the above problems existing in the cathode layer oxide materials, the existing improvement methods mainly include surface coating and doping. These two methods can improve the air stability of the cathode material, reduce side reactions, protect the material from reacting with the electrolyte, and inhibit the generation of alkali, thereby optimizing the cycle performance, safety performance, rate performance, and sodium storage performance of the material. Regarding the modification method of the cathode material, generally, only one of coating or doping is used to improve the material performance, and the traditional solid-phase mixing of electrode materials and nanoparticles is used. This method cannot effectively control the thickness of the nanoparticles coated on the surface of the cathode material particles, and the generated alkaline substances still exist on the material surface, resulting in problems such as corrosion, performance degradation, and cracks in the cathode material particles during the cycling process of sodium batteries.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a modification method for a cathode material of a sodium-ion battery, which can solve the technical problems of poor capacity, poor air stability, and low rate performance of sodium cathode materials in the prior art, and achieve the technical effects of good ion mobility, good air stability, and not being easily corroded by the electrolyte for the sodium cathode material.

[0007] The second object of the present invention is to provide a modified layered oxide material for the cathode of a sodium-ion battery, which has better capacity, good air stability, and high rate performance.

[0008] The third object of the present invention is to provide a sodium-ion battery with good cycle stability and good rate performance.

[0009] The fourth object of the present invention is to provide an application of a sodium-ion battery, which can achieve outstanding application effects.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0011] The present invention provides a modification method for a cathode material of a sodium-ion battery, including the following steps:

[0012] First, the cathode material of the sodium-ion battery is stirred, filtered by suction, and dried in a modification solution, and then subjected to high-temperature sintering to obtain the modified cathode material of the sodium-ion battery, wherein the modification solution includes phytic acid and sulfoxide.

[0013] In the prior art, mainly because the layered oxide material of the sodium-ion battery cathode can undergo side reactions with water, resulting in structural collapse and performance degradation, the present invention uses a modification solution for modification, and specifically selects sulfoxide as the solvent. During the stirring process, phytic acid is more evenly distributed in the solution and reacts with the residual alkali on the surface at high temperature to form Na3PO4 / Na4P2O7, while achieving the effect of P element doping. Na3PO4 / Na4P2O7 has the effect of improving Na + diffusion kinetics, and at the same time, coating on the surface of the material can prevent side reactions with oxygen and water in the air and electrolyte corrosion. P element doping can improve the cycle rate performance of the material.

[0014] The modification method of the present invention not only has few operation steps, simple process, high success rate, and is suitable for large-scale popularization and production, but also solves the technical problems of poor capacity, poor air stability, and low rate performance of sodium cathode materials in the prior art, and achieves the technical effects of good ion mobility, good air stability, and not being easily corroded by the electrolyte for the sodium cathode material.

[0015] Preferably, the sulfoxide includes at least one of thionyl chloride and dimethyl sulfoxide.

[0016] Preferably, as a further feasible solution, the dosage of phytic acid is 0.1%-3% of the mass of the sodium-ion cathode material;

[0017] Preferably, as a further feasible solution, the dosage of phytic acid is 0.5%-2.5% of the mass of the sodium-ion cathode material;

[0018] Preferably, as a further feasible solution, the dosage of phytic acid is 1%-2% of the mass of the sodium-ion cathode material.

[0019] Preferably, the dosage of phytic acid can also be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%.

[0020] In the modified solution of the present invention, phytic acid is selected because it can form a homogeneous substance after mixing with sulfoxide, and can better play its role after modifying the cathode material. Moreover, as a universal solvent, sulfoxide is selected because it will not damage the material itself and cause any impact. During the stirring process, phytic acid is more evenly mixed with the material. After high-temperature sintering, phytic acid will form a coating and P element doping on the surface of the material.

[0021] Therefore, through a large number of practices, it is found that phytic acid and sulfoxide are specifically selected for a specific combination. Phytic acid is an organic acid that can eliminate residues and contains P element. Only phytic acid can achieve the acetic acid effect; and the dosage of phytic acid also has exact requirements, because only when it is controlled within the dosage range defined in the present invention can the effect of modifying the sodium-ion battery cathode layered oxide material be further improved, and it is also more beneficial to further improve the air stability and rate performance of the material. If the dosage of phytic acid is not controlled within the requirements of the present invention, when the addition amount of phytic acid is too small, its improvement of the material performance will be limited, and when the addition amount of phytic acid is too large, it will damage the layered structure of the material itself.

[0022] Preferably, as a further feasible solution, the mass ratio of phytic acid to sulfoxide is 1:(4-20); preferably 1:(4-15), and more preferably 1:(8-15).

[0023] Preferably, as a further feasible solution, the temperature of the high-temperature sintering is 300°C-700°C, and the time of the high-temperature sintering is 2h-10h.

[0024] Preferably, as a further feasible solution, the high-temperature sintering temperature is 350°C - 650°C, and the high-temperature sintering time is 2h - 8h;

[0025] Preferably, the high-temperature sintering temperature is 400°C - 600°C, and the high-temperature sintering time is 2h - 6h;

[0026] Preferably, the high-temperature sintering temperature is 450°C - 600°C, and the high-temperature sintering time is 3h - 6h.

[0027] In the present invention, typical but non-limiting sintering temperature conditions for high-temperature sintering are, for example, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C; typical but non-limiting time conditions for high-temperature sintering are, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h.

[0028] In the present invention, the temperature and time of high-temperature sintering are more conducive to further improving the cycling and rate performance of the modified material.

[0029] Preferably, as a further feasible solution, the stirring time is 0.5h - 5h; preferably, the stirring time is 1h - 4h.

[0030] Preferably, as a further feasible solution, after high-temperature sintering, cooling is carried out, and the cooling rate is 0.5°C / min - 1°C / min. For example, it can be 0.5°C / min, 0.6°C / min, 0.7°C / min, 0.8°C / min, 0.9°C / min, 1°C / min, but is not limited thereto.

[0031] The present invention also provides a modified sodium-ion battery cathode material obtained by the above modification method.

[0032] The present invention also provides a sodium-ion battery, including the above sodium-ion battery cathode material and the sodium-ion battery cathode material obtained by the modification method. The above sodium-ion battery of the present invention has good applications in device driving.

[0033] In addition to the positive electrode sheet containing the positive electrode material of the present invention, the above sodium-ion battery further includes an electrolyte and a separator;

[0034] The available electrolyte is generally obtained by dissolving a sodium salt in an organic solvent;

[0035] Among them, the available sodium salts include at least one of NaPF6 and Na-ClO4;

[0036] The organic solvents used are mainly anhydrous solvents, including at least one of carbonates (ethylene carbonate, propylene carbonate, diethyl carbonate, etc.), 1,2-dimethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran;

[0037] The available separators include at least one of a single-layer polypropylene film, a polyethylene film, a polyethylene / polypropylene / polyethylene composite film, a cellulose non-woven fabric separator, and glass fiber.

[0038] In the solution of the present invention, the sodium-ion battery cathode material is soaked and stirred in a modification solution, then suction filtration is carried out, and then high-temperature sintering is carried out. In this way, not only can the alkali residues on the surface of the sodium-ion battery cathode layer oxide (Na X TMO2) material be removed, but also the surface of the material can be coated, and at the same time, the effect of P doping can be achieved. The technical effects of good ion migration, good air stability, and not being easily corroded by the electrolyte of the sodium battery cathode material are achieved.

[0039] Specifically, phytic acid is dissolved in sulfoxide and ultrasonicated, and the cathode layer oxide material is added to the solution and stirred. During the stirring process, phytic acid can remove the alkali residues on the surface of the material and at the same time evenly distribute phytic acid. Then suction filtration and drying are carried out; through high-temperature sintering, a Na3PO4 / Na4P2O7 coating is formed on the surface of the material, and at the same time, the effect of P element doping is achieved. Na3PO4 / Na4P2O7 has the effect of improving Na + diffusion kinetics. P doping expands the layer spacing of the material. Thus, the technical problems of poor capacity, poor air stability, and low rate existing in the sodium battery cathode material in the prior art are solved; in addition, the coating method provided by the present invention has few operation steps, simple process, high success rate, and is suitable for large-scale popularization and production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0041] Figure 1 XRD pattern of the cathode layer oxide material provided in Example 1 of the present invention;

[0042] Figure 2 SEM pattern of the cathode layer oxide material provided in Example 1 of the present invention;

[0043] Figure 3 XRD pattern of the cathode layer oxide material provided in Comparative Example 1;

[0044] Figure 4SEM pattern of the cathode layered oxide material provided in Comparative Example 1;

[0045] Figure 5 XRD comparison pattern of the cathode layered oxide materials provided in Example 1 and Comparative Example 1;

[0046] Figure 6 First charge-discharge curve of the cathode layered oxide materials provided in Example 1 and Comparative Example 1;

[0047] Figure 7 Cycling performance comparison chart obtained from Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention;

[0048] Figure 8 Rate performance comparison chart obtained from Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention. Detailed implementation mode

[0049] The following will describe the implementation scheme of the present invention in detail in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0050] Example 1

[0051] A modification method for a cathode layered oxide material of a sodium-ion battery, comprising the following steps:

[0052] (1) Solid-phase sintering of sodium carbonate, nickel oxide, iron oxide and manganese tetroxide to obtain a cathode layered oxide material (NaMn 0.33 Fe 0.33 Ni 0.33 O2);

[0053] (2) Mix phytic acid and dimethyl sulfoxide and ultrasonicate them, with a mass ratio of 1:10. Then add the cathode layered oxide material and stir for 3 h, and then filter and dry;

[0054] Among them, the dosage of phytic acid is 2 wt% of the cathode layered oxide material;

[0055] (3) Sinter the stirred, filtered and dried cathode layered oxide material at 600 °C for 6 h. After high-temperature sintering, cool down at a rate of 0.5 °C / min to obtain the modified cathode layered oxide material. Its XRD pattern is shown in Figure 1 , and its SEM pattern is shown in Figure 2 .

[0056] Example 2

[0057] A modification method for a positive electrode layered oxide material of a sodium-ion battery, comprising the following steps:

[0058] (1) Sinter sodium carbonate, nickel oxide, iron oxide and manganese tetroxide by solid-phase method to obtain a positive electrode layered oxide material (NaMn 0.33 Fe 0.33 Ni 0.33 O2);

[0059] (2) Mix phytic acid and dimethyl sulfoxide and ultrasonicate them, with a mass ratio of 1:4. Subsequently, add the positive electrode layered oxide material and stir for 3 h, then filter and dry;

[0060] Among them, the dosage of phytic acid is 3 wt% of the positive electrode layered oxide material;

[0061] (3) Sinter the stirred, filtered and dried positive electrode layered oxide material at 500 °C for 6 h. After high-temperature sintering, cool down at a rate of 0.5 °C / min to obtain the modified positive electrode layered oxide material.

[0062] Example 3

[0063] A modification method for a positive electrode layered oxide material of a sodium-ion battery, comprising the following steps:

[0064] (1) Sinter sodium carbonate, nickel oxide, iron oxide and manganese tetroxide by solid-phase method to obtain a positive electrode layered oxide material (NaMn 0.33 Fe 0.33 Ni 0.33 O2);

[0065] (2) Mix phytic acid and dimethyl sulfoxide and ultrasonicate them, with a mass ratio of 1:20. Subsequently, add the positive electrode layered oxide material and stir for 3 h, then filter and dry;

[0066] Among them, the dosage of phytic acid is 2.5 wt% of the positive electrode layered oxide material;

[0067] (3) Sinter the stirred, filtered and dried positive electrode layered oxide material at 700 °C for 6 h. After high-temperature sintering, cool down at a rate of 0.5 °C / min to obtain the modified positive electrode layered oxide material.

[0068] Example 4

[0069] A modification method for a positive electrode layered oxide material of a sodium-ion battery, comprising the following steps:

[0070] (1) Sinter sodium carbonate, nickel oxide, iron oxide and manganese tetroxide by solid-phase method to obtain a positive electrode layered oxide material (NaMn0.33 Fe 0.33 Ni 0.33 O2);

[0071] (2) Mix phytic acid and dimethyl sulfoxide and sonicate them. The mass ratio of the two is 1:15. Then add the positive electrode layered oxide material and stir for 3 h, followed by suction filtration and drying;

[0072] Among them, the dosage of phytic acid is 1 wt% of the positive electrode layered oxide material;

[0073] (3) Sinter the positive electrode layered oxide material after stirring, suction filtration and drying at 600 °C for 6 h. The cooling temperature and time are 0.5 °C / min to obtain the modified positive electrode layered oxide material.

[0074] Example 5

[0075] A method for modifying a positive electrode layered oxide material for a sodium-ion battery, comprising the following steps:

[0076] (1) Perform solid-phase sintering on sodium carbonate, nickel oxide, iron oxide and manganese tetraoxide to obtain a positive electrode layered oxide material (NaMn 0.33 Fe 0.33 Ni 0.33 O2);

[0077] (2) Mix phytic acid and dimethyl sulfoxide and sonicate them. The mass ratio of the two is 1:8. Then add the positive electrode layered oxide material and stir for 3 h, followed by suction filtration and drying;

[0078] Among them, the dosage of phytic acid is 0.5 wt% of the positive electrode layered oxide material;

[0079] (3) Sinter the positive electrode layered oxide material after stirring, suction filtration and drying at 500 °C for 6 h. The cooling temperature and time are 0.5 °C / min to obtain the modified positive electrode layered oxide material.

[0080] Comparative Example 1

[0081] A positive electrode layered oxide material for a sodium-ion battery is prepared by the following method:

[0082] Perform solid-phase sintering on sodium carbonate, nickel oxide, iron oxide and manganese tetraoxide to obtain a positive electrode layered oxide material (NaMn 0.33 Fe 0.33 Ni 0.33 O2). Its XRD pattern is shown in Figure 3 , and its SEM pattern is shown in Figure 4 .

[0083] Experimental Example 1

[0084] The materials prepared in Examples 1-3 and Comparative Example 1 were used as the positive electrode, 1mol / L NaClO4 in EC:DEC = 1:1 Vol% with 5% FE was used as the electrolyte, and glass fiber was used as the separator to assemble a 2025 button cell;

[0085] The battery performance was tested under the condition of 150 mA / g, and the results are shown in Figure 7 and Figure 8 , and also shown in Table 1-2.

[0086] Table 1 Cycling Comparison Chart

[0087]

[0088] Table 2 Rate Comparison Chart

[0089]

[0090] It can be seen from Figure 5 that the XRD peak of Example 1 is more to the left than that of Comparative Example 1, indicating that the material layer spacing of Example 1 is larger and the capacity is higher; Figure 6 From the first charge-discharge diagram of Figure 7 , it can also be seen that the charge-discharge performance of Example 1 is more excellent than that of Comparative Example 1. It can be seen from

[0091] It can be seen from Figure 7 that the capacity of the battery at 1C is 124.98 mAh / g (compared with 120.99 mAh / g of Comparative Example 1).

[0092] It can be seen from Figure 8 that the capacity of the battery at 1C is 124.98 mAh / g (compared with 122.12 mAh / g of Example 2; 114.54 mAh / g of Example 3; 120.99 mAh / g of Comparative Example 1), and the capacity is still 118.37 mAh / g after 300 cycles (compared with 110.02 mAh / g of Example 2; 90.51 mAh / g of Example 3; 95.8 mAh / g of Comparative Example 1), indicating very good cycle stability.

[0093] It can be known from the specific experimental results that the performance of the battery positive electrode materials in Examples 4-5 is basically equivalent to that of Example 3.

[0094] In summary, the present invention soaks the cathode layered oxide with a modified solution, while removing the residual alkali on the material surface, and then uses high temperature to generate a uniform Na3PO4 / Na4P2O7 coating and P element doping to obtain a modified cathode layered oxide material; the present invention not only solves the problem of residual alkali on the surface of the cathode layered oxide material, but also coats a uniform Na3PO4 / Na4P2O7 protective film with high ionic conductivity on the material surface, while achieving the purpose of doping, thereby maintaining the cycling performance of the layered material, improving the rate performance and specific capacity to meet the actual use requirements of sodium ion batteries.

[0095] Although the invention has been illustrated and described with reference to specific embodiments, it will be appreciated that many other changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, this means that all such changes and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A modification method for a cathode material of a sodium-ion battery, characterized in that It includes the following steps: First, stir, filter by suction, and dry the positive electrode material of the sodium-ion battery in the modification solution, and then perform high-temperature sintering to obtain the modified positive electrode material of the sodium-ion battery, wherein the modification solution includes phytic acid and sulfoxide.

2. The modification method according to claim 1, characterized in that, The dosage of phytic acid is 0.1%-3% of the mass of the positive electrode material of sodium ions; Preferably, the dosage of phytic acid is 0.5%-2.5% of the mass of the positive electrode material of sodium ions; Preferably, the dosage of phytic acid is 1%-2% of the mass of the positive electrode material of sodium ions.

3. The modification method according to claim 1, wherein, The mass ratio of phytic acid to sulfoxide is 1:(4-20); preferably 1:(4-15), and more preferably 1:(8-15).

4. The modification method according to claim 1, wherein The temperature of the high-temperature sintering is 300°C-700°C, and the time of the high-temperature sintering is 2h-10h.

5. The modification method according to claim 1, characterized in that, The stirring time is 0.5h-5h; preferably, the stirring time is 1h-4h.

6. The modification method according to claim 1, characterized in that, The high-temperature sintering temperature is 350°C-650°C, and the high-temperature sintering time is 2h-8h; Preferably, the high-temperature sintering temperature is 400°C-600°C, and the high-temperature sintering time is 2h-6h; Preferably, the high-temperature sintering temperature is 450°C-600°C, and the high-temperature sintering time is 3h-6h.

7. The modification method according to claim 1, characterized in that, After the high-temperature sintering, cooling is carried out, and the cooling rate is 0.5°C / min-1°C / min.

8. The modified positive electrode material of the sodium-ion battery obtained by the modification method according to any one of claims 1-7.

9. A sodium-ion battery, characterized in that, The positive electrode material of the sodium-ion battery by the modification method according to any one of claims 1-7 and the modified positive electrode material of the sodium-ion battery according to claim 8.

10. An application of the sodium-ion battery according to claim 9 in device driving.

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