Positive electrode material for improving cycle performance of sodium battery, positive plate and battery

Abstract

The invention discloses a positive electrode material for improving the cycle performance of a sodium battery, a positive plate and a battery. The positive electrode material is a positive electrode material modified product formed by introducing fluorine, zinc, titanium elements and-SO3H groups into a sodium ion battery positive electrode material. The preparation method comprises the following modification steps for the sodium-ion battery positive electrode material: S1, introducing fluorine, zinc and titanium elements into the sodium-ion battery positive electrode material through a high-temperature calcination method to obtain a positive electrode material intermediate; and S2, introducing a-SO3H group into the positive electrode material intermediate to obtain a final positive electrode material modified product. Through multi-dimensional synergistic modification, the structural stability and the cycle life of the sodium ion battery positive electrode material are improved, and the cycle performance of the sodium battery is finally remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a cathode material, a cathode sheet and a battery for improving the cycle performance of sodium batteries Background Art

[0002] With the global energy structure transformation towards green and low-carbon, the demand for clean energy technology iteration is becoming increasingly urgent. In the field of energy storage, although lithium-ion batteries dominate, due to the scarcity of lithium resources and the pressure of mining environment, the industry has begun to turn its attention to the sodium-ion battery system with a wider resource distribution and more controllable cost. As the core component of sodium batteries, the performance optimization of cathode materials directly affects the feasibility of the overall technical route

[0003] Among the current mainstream sodium battery cathode materials, layered oxides exhibit high energy density and charge-discharge efficiency due to their unique crystal structure, and are regarded as the most promising technical direction. During the charge-discharge process, these materials allow sodium ions to rapidly intercalate and deintercalate between layers, but are prone to structural distortion or phase transformation during long-term cycling, resulting in the contact failure between the active material and the current collector, and ultimately leading to rapid capacity decay. In contrast, although polyanion-type materials have better structural stability, they are restricted by bottlenecks such as low intrinsic conductivity and insufficient working voltage platform, and it is difficult to meet the requirements of high energy density scenarios. Therefore, how to enhance the structural robustness of layered oxides while maintaining their high specific capacity characteristics and improve the cycle stability of layered oxides has become the key to breaking through the industrialization obstacles of sodium batteries Summary of the Invention

[0004] The purpose of the present invention is to provide a cathode material, a cathode sheet and a battery for improving the cycle performance of sodium batteries, which can enhance the structural stability and cycle life of the cathode material of sodium-ion batteries through multi-dimensional collaborative modification, and ultimately significantly improve the cycle performance of sodium batteries

[0005] To achieve the above purpose, the technical solution provided by the present invention is as follows

[0006] The first aspect of the present application provides a cathode material for improving the cycle performance of sodium batteries, which is characterized in that: the cathode material is a modified cathode material formed by introducing fluorine, zinc, titanium elements and -SO3H groups into the cathode material of sodium-ion batteries

[0007] The cathode material of sodium-ion batteries is a cathode material of sodium-ion batteries doped with Ni, Mn, and Fe elements

[0008] The second aspect of the present application provides a preparation method of a cathode material for improving the cycle performance of sodium batteries, including the following modification steps for the cathode material of sodium-ion batteries

[0009] S1: In the cathode material of the sodium-ion battery, fluorine, zinc, and titanium elements are introduced by means of high-temperature calcination to obtain an intermediate cathode material;

[0010] S2: Then, -SO3H groups are introduced into the intermediate cathode material to obtain a final modified cathode material product.

[0011] To optimize the above technical solution, the specific limitations adopted also include:

[0012] The introduction method of the fluorine, zinc, and titanium elements is as follows: First, a compound containing fluorine, zinc, and titanium is mechanically mixed with the cathode material of the sodium-ion battery to make the materials evenly mixed, and then the obtained mixture is subjected to high-temperature calcination treatment.

[0013] Preferably, the compound containing fluorine, zinc, and titanium is ZnF2 and TiF4.

[0014] Further, in step S1, the mass ratio of the cathode material of the sodium-ion battery to ZnF2 is 195 - 210:1; the mass ratio of the cathode material of the sodium-ion battery to TiF4 is 345 - 360:1.

[0015] The conditions for the high-temperature calcination are 700 - 1000 °C, 10 - 20 h; the heating rate of the calcination is 40 - 70 °C / min, and the annealing rate is 15 - 30 °C / min.

[0016] The introduction method of the -SO3H groups is as follows: The intermediate cathode material is subjected to plasma treatment in a SO2 gas atmosphere, and the treatment conditions are: the flow rate of the SO2 gas is 30 - 40 mL / min, the treatment ambient temperature is 20 - 30 °C, the treatment time is 0.5 - 1.5 h, and the discharge power is 80 - 150 W.

[0017] The third aspect of the present application provides a positive electrode sheet containing the above cathode material.

[0018] The fourth aspect of the present application provides a battery containing the above positive electrode sheet.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The present invention provides a cathode material for improving the cycle performance of sodium batteries. Fluorine, zinc, and titanium elements are introduced into the conventional cathode material of sodium-ion batteries by means of high-temperature calcination to obtain an intermediate material, and then the intermediate material is subjected to plasma treatment in SO2 gas to introduce -SO3H groups to obtain a final modified product.

[0021] Through Zn and Ti doping modification, the Na sites and TM sites in the cathode material of sodium-ion batteries are occupied respectively, inhibiting the migration of Ni and Fe in the traditional cathode material of sodium-ion batteries, reducing the phase transition from O3 to O'3, and improving the cycle stability of the material. At the same time, due to the strong electronegativity of fluorine, the arrangement and distribution of transition metal elements are changed, effectively inhibiting the crystal distortion caused by the Jahn-Teller effect and improving the mechanical integrity of the battery.

[0022] The present invention also surface-modifies the intermediate material introducing fluorine, zinc, and titanium elements through -SO3H groups, improving the polarity and adhesion of the surface of the cathode material for sodium-ion batteries. Moreover, the -SO3H groups form a multi-dimensional synergistic effect with F, Zn, and Ti, providing favorable conditions for the long cycle of the battery and ultimately significantly improving the cycle performance of the sodium battery. Specific Embodiments

[0023] The above content of the present invention will be further described in detail below in the form of specific embodiments. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments. All technologies implemented based on the above content of the present invention belong to the scope of the present invention.

[0024] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified. The reagents, methods, and equipment used are all conventional reagents, methods, and equipment in the technical field of the present invention unless otherwise specified.

[0025] The present invention provides a cathode material for improving the cycle performance of a sodium battery. The cathode material is a modified cathode material formed by introducing fluorine, zinc, titanium elements, and -SO3H groups into the cathode material of a sodium-ion battery.

[0026] In some embodiments, the cathode material of the sodium-ion battery is a cathode material of a sodium-ion battery doped with Ni, Mn, and Fe elements.

[0027] Through Zn and Ti doping modification, the Na sites and TM sites in the cathode material of sodium-ion batteries are occupied respectively, inhibiting the migration of Ni and Fe in the traditional cathode material of sodium-ion batteries. The migration of Ni and Fe will lead to the slip of the transition metal layer and lattice distortion, triggering irreversible phase transitions, such as the transformation from a layered structure to a spinel structure. By inhibiting the migration, the integrity of the two-dimensional ion channel of the material can be maintained, the lattice stability can be enhanced, and the accumulation of structural stress during charge and discharge can be reduced. In addition, the migration of Ni and Fe will block the interlayer sodium ion diffusion channel, and inhibiting the migration can keep the channel unobstructed and improve the sodium ion deintercalation kinetics.

[0028] The Zn and Ti doping modification of the present invention can also alleviate the phase change from O3 to O'3, improving the cycle stability of the cathode material for sodium-ion batteries; in the cathode material for sodium-ion batteries, the O3 phase is a layered structure, while the O'3 phase is a structure distortion phase caused by the insertion and extraction of sodium ions during charge and discharge, with a slight change in its stacking mode or sodium site distribution. This phase change will lead to lattice stress accumulation, ion channel blockage, and capacity decay; Zn 2+ occupies the transition metal layer, and its inactive characteristics can stabilize the lattice framework, inhibit the slip of the transition metal layer during charge and discharge, thereby reducing the irreversible phase change of O3→O'3; Ti 4+ with a high charge density can enhance the transition metal-oxygen bonding strength, reduce lattice oxygen loss and structure distortion, and at the same time inhibit the migration of Ni / Fe, maintaining the stability of the layered structure; Zn 2+ and Ti 4+ with different ionic radii can optimize the sodium layer spacing, maintain the coherence of the sodium ion diffusion channel, and reduce the channel blockage caused by phase change; The co-doping of Zn and Ti also reduces the lattice dynamic stress through the multi-element synergistic effect, such as the high-entropy effect, and alleviates the local structure collapse caused by the repeated insertion and extraction of sodium ions, thereby inhibiting the cumulative effect of the O3→O'3 phase change;

[0029] At the same time, through the strong electronegativity of fluorine, the present invention changes the arrangement and distribution of transition metal elements, thereby effectively suppressing the crystal distortion caused by the Jahn-Teller effect and improving the mechanical integrity of the battery; The Jahn-Teller effect damages the performance of sodium-ion batteries through multiple mechanisms such as irreversible phase change, active material dissolution, and interface degradation; The strong electronegativity of fluorine effectively inhibits the Jahn-Teller distortion of transition metals through electron structure regulation, bonding strengthening, and lattice ordering mechanisms, not only improving the structural stability of the material but also improving the reversibility of sodium ion insertion and extraction.

[0030] The present invention also surface-modifies the intermediate material introducing fluorine, zinc, and titanium elements through -SO3H groups, improving the polarity and adhesion of the surface of the cathode material for sodium-ion batteries. After long-term charge and discharge, the active material and the current collector still maintain excellent adhesion, providing favorable conditions for the long cycle of the battery; The -SO3H group also forms a multi-dimensional synergistic effect with the lattice anchoring, bonding strengthening, and phase change inhibition of F, Zn, and Ti through ion flux regulation, interface chemical bonding, and defect passivation, improving the structural stability and cycle life of the cathode material for sodium-ion batteries, and ultimately significantly improving the cycle performance of sodium batteries.

[0031] The present invention also provides a preparation method for a cathode material to improve the cycle performance of sodium batteries, including the following modification steps for the cathode material of sodium-ion batteries:

[0032] S1: In the cathode material of a sodium-ion battery, fluorine, zinc, and titanium elements are introduced by high-temperature calcination to obtain an intermediate of the cathode material;

[0033] S2: Then, -SO3H groups are introduced into the intermediate of the cathode material to obtain the final modified product of the cathode material.

[0034] The introduction method of fluorine, zinc, and titanium elements is to first mechanically mix the compounds containing fluorine, zinc, and titanium with the cathode material of the sodium-ion battery to make the materials evenly mixed, and then perform high-temperature calcination treatment on the obtained mixture.

[0035] In some embodiments, the compounds containing fluorine, zinc, and titanium are ZnF2 and TiF4. In step S1, the mass ratio of the cathode material of the sodium-ion battery to ZnF2 is 195 - 210:1; the mass ratio of the cathode material of the sodium-ion battery to TiF4 is 345 - 360:1.

[0036] The conditions for high-temperature calcination are 700 - 1000 °C and 10 - 20 h; the heating rate of calcination is 40 - 70 °C / min, and the annealing rate is 15 - 30 °C / min.

[0037] In some embodiments, the introduction method of -SO3H groups is to perform plasma treatment on the intermediate of the cathode material in a SO2 gas atmosphere, and the treatment conditions are: the flow rate of SO2 gas is 30 - 40 mL / min, the treatment ambient temperature is 20 - 30 °C, the treatment time is 0.5 - 1.5 h, and the discharge power is 80 - 150 W.

[0038] The present invention also provides a positive electrode sheet containing the above-mentioned cathode material.

[0039] The present invention also provides a battery containing the above-mentioned positive electrode sheet.

[0040] The technical solution of the present invention will be further described in detail with specific embodiments as follows:

[0041] The following specific embodiments take the NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 O2 material as a representative of the traditional cathode material of a sodium-ion battery for introduction, but the applicable solutions of this application are not limited thereto.

[0042] Example 1:

[0043] (1) Preparation of the modified NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 O2 material

[0044] A certain amount of traditional NaNi 2 / 3 Mn1 / 6 Fe 1 / 6 Mechanically mix the FeO₂ material, ZnF₂, and TiF₄; after mixing evenly, put the mixture into a tube furnace and calcine the mixture by calcination to obtain an intermediate material. The calcination temperature is 800 °C, the calcination temperature time is 12 h, the heating rate of calcination is 50 °C / min, and the annealing rate is 20 °C / min; put the intermediate material into a plasma device, introduce SO₂, and perform plasma treatment: the flow rate of the SO₂ gas is 35 mL / min, the treatment environment is 25 °C, the treatment time is 1 h, and the discharge power is 100 W to obtain the final modified material product;

[0045] Among them, the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the FeO₂ material to ZnF₂ is 200 - 205:1, and the traditional NaNi 2 / 3Mn 1 / 6 Fe 1 / 6 The mass ratio of the FeO₂ material to TiF₄ is 350 - 355:1;

[0046] (2) Preparation of the positive electrode paste:

[0047] The positive electrode active material is the final modified material product obtained in step (1), the binder is PVDF (Solvay 5130), and the conductive agent is Super P (TIMCAL); stir and mix according to the ratio of positive electrode active material: binder: conductive agent = 8:1:1, and after mixing evenly, coat it on a 12 - μm aluminum foil and dry it in a vacuum drying oven at 120 °C for 12 h;

[0048] (3) Assembly of the button battery:

[0049] The button battery case is of the CR2032 model, the separator is a 20 - μm separator, and the electrode sheet is a positive electrode sheet with a uniform coating. In a glove box filled with argon, assemble the button battery in the order of battery case - place the positive electrode sheet - drop the electrolyte - place the separator - drop the electrolyte - place the sodium sheet - place the gasket spring sheet - battery case;

[0050] (4) Test of the cycle charge - discharge performance:

[0051] Use a button battery charge - discharge tester (Wuhan Landian, CT2001A) to perform charge - discharge tests (10 cycles, 30 cycles, 50 cycles) on the button battery at a current of 0.2C, and the voltage range is 2.5 - 3.3V; the test results are shown in Table 1.

[0052] Example 2:

[0053] Basically the same as Example 1, the difference is: the traditional NaNi 2 / 3Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0054] Example 3:

[0055] Same as Example 1, except that: the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0056] Example 4:

[0057] Same as Example 1, except that: the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0058] Example 5:

[0059] Same as Example 1, except that: the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0060] Example 6:

[0061] Same as Example 1, except that: the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0062] Example 7:

[0063] Same as Example 1, except that: the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0064] Example 8:

[0065] Same as Example 1, except that: the traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the

[0066] Example 9:

[0067] Basically the same as Example 1, with the difference that: traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 The mass ratio of the O2 material to TiF4 is 360 - 365:1.

[0068] Comparative Example 1:

[0069] The difference from Example 1 is that: in step (1), no ZnF2 is introduced, and the others are the same as Example 1.

[0070] Comparative Example 2:

[0071] The difference from Example 1 is that: in step (1), no TiF4 is introduced, and the others are the same as Example 1.

[0072] Comparative Example 3:

[0073] The difference from Example 1 is that: traditional NaNi 2 / 3 Mn 1 / 6 Fe 1 / 6 O2 is used as the cathode material without modification, and the others are the same as Example 1.

[0074] Comparative Example 4:

[0075] The difference from Example 1 is that: the intermediate material is not subjected to plasma treatment in SO2 gas, and the others are the same as Example 1.

[0076] The test and evaluation results of each example and comparative example are as follows:

[0077] Table 1 Test results of cycle performance

[0078] Number 10-cycle performance 30-cycle performance 50-cycle performance Example 1 97.4％ 94.2％ 91.2％ Example 2 91.8％ 88.3％ 84.1％ Example 3 92.9％ 90.6％ 87.3％ Example 4 93.3％ 90.3％ 86.7％ Example 5 91.4％ 88.1％ 83.1％ Example 6 92.7％ 86.8％ 82.8％ Example 7 93.8％ 90.2％ 86.3％ Example 8 93.1％ 90.0％ 85.8％ Example 9 92.0％ 86.8％ 82.3％ Comparative Example 1 87.6％ 82.9％ 76.2％ Comparative Example 2 84.3％ 77.1％ 70.8％ Comparative Example 3 79.1％ 67.4％ 60.0％ Comparative Example 4 91.1％ 86.5％ 81.6％

[0079] The test results show that:

[0080] Comparing Examples 1 to 9, it can be seen that when Zn, Ti, and F are introduced within a certain range, the effect is better; in this solution, it is preferred to use compounds containing fluorine, zinc, and titanium, namely ZnF2 and TiF4, which will not introduce other unnecessary doping substances; however, the scope of this application is not limited to this, and other combinations of compounds containing Zn and Ti may also achieve the above effects. Directly using ZnF2 and TiF4 is only one preferred solution.

[0081] Comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be seen that in the case of no ZnF2 introduction or no TiF4 introduction, the test results of the battery cycle performance are obviously worse than those of Example 1, which also proves the synergistic effect of the co-introduction of Zn, Ti, and F.

[0082] Comparing Example 1 with Comparative Example 3, it can be seen that the cycle performance of the sodium battery containing the improved cathode material in this application is significantly better than that of the sodium battery using the traditional cathode material.

[0083] Comparing Example 1 with Comparative Example 4, it can be seen that when the plasma treatment is not carried out in SO2 gas, the obtained results are better than those of Comparative Example 3 using the traditional cathode material and Comparative Examples 1 and 2 without the introduction of ZnF2 or TiF4, but the effect is not as significant as that of Example 1, indicating the importance of the multi-dimensional synergistic effect of introducing -SO3H groups with F, Zn, and Ti.

[0084] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, any simple modifications, equivalent replacements, and improvements made to the above embodiments still fall within the protection scope of the technical solution of the present invention.

Claims

1. A positive electrode material for improving the cycle performance of a sodium battery, characterized in that: The positive electrode material is a modified positive electrode material formed by introducing fluorine, zinc, titanium elements and -SO3H groups into the positive electrode material of a sodium ion battery.

2. The positive electrode material for improving the cycle performance of sodium batteries according to claim 1, characterized in that: The positive electrode material of the sodium ion battery is a sodium ion battery positive electrode material doped with Ni, Mn, and Fe elements.

3. A method for preparing a positive electrode material for improving the cycle performance of a sodium battery, characterized in that: The method comprises the following steps for modifying the positive electrode material of a sodium ion battery: S1: Into the positive electrode material of sodium ion battery, fluorine, zinc and titanium elements are introduced by high temperature calcination to obtain a positive electrode material intermediate; S2: Then, a -SO3H group is introduced into the positive electrode material intermediate to obtain a final positive electrode material modified product.

4. The method for preparing a positive electrode material for improving the cycle performance of a sodium battery according to claim 3, characterized in that: The fluorine, zinc and titanium elements are introduced by first mechanically mixing the compounds containing fluorine, zinc and titanium with the positive electrode material of the sodium ion battery to make the materials uniform, and then subjecting the obtained mixture to high-temperature calcination treatment.

5. The method for preparing a positive electrode material for improving the cycle performance of a sodium battery according to claim 4, characterized in that: The compounds containing fluorine, zinc and titanium are ZnF2 and TiF4.

6. The method for preparing a positive electrode material for improving the cycle performance of a sodium battery according to claim 5, characterized in that: In the step S1, the mass ratio of the sodium ion battery positive electrode material to ZnF2 is 195-210:1; the mass ratio of the sodium ion battery positive electrode material to TiF4 is 345-360:

1.

7. The method for preparing a positive electrode material for improving the cycle performance of a sodium battery according to claim 3, characterized in that: The high-temperature calcination conditions are 700-1000°C for 10-20h; the calcination heating rate is 40-70°C / min, and the annealing rate is 15-30°C / min.

8. The method for preparing a positive electrode material for improving the cycle performance of a sodium battery according to claim 3, characterized in that: The method of introducing the -SO3H group is to subject the positive electrode material intermediate to plasma treatment in SO2 gas. The treatment conditions are: the flow rate of SO2 gas is 30-40 mL / min, the treatment environment temperature is 20-30°C, the treatment time is 0.5-1.5 h, and the discharge power is 80-150 W.

9. A positive electrode sheet, characterized in that: Contains the positive electrode material described in claim 1 or 2 or prepared by the method described in any one of claims 3 to 8.

10. A battery, characterized in that: A positive electrode sheet comprising the positive electrode sheet according to claim 9.