Battery positive electrode sheet, preparation method thereof and sodium ion battery

Abstract

The application relates to a battery positive pole piece, a preparation method thereof and a sodium ion battery. The preparation method of the battery positive pole piece comprises the following steps: adding a positive pole active substance, a positive pole conductive agent and a positive pole adhesive into a positive pole sodium supplement additive solution, stirring to obtain a positive pole slurry, coating the obtained positive pole slurry on a positive pole current collector, and performing drying, rolling and slitting treatment to obtain the battery positive pole piece; the positive pole sodium supplement additive comprises at least one of sodium glutamate, sodium glycerate, sodium benzenesulfonate, sodium nitrilotriacetate and sodium succinate.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery cathode material preparation technology, specifically relating to a battery cathode sheet and its preparation method, and a sodium-ion battery. Background Technology

[0002] In recent years, sodium-ion batteries have attracted much attention due to the abundance, wide distribution, and low cost of sodium resources. Compared with lithium-ion batteries, they exhibit a significant cost advantage in large-scale energy storage. However, in the initial cycle of sodium-ion batteries, the negative electrode irreversibly consumes the limited sodium source released from the positive electrode, leading to a decrease in the first-cycle coulombic efficiency and thus reducing the energy density.

[0003] In a full-cell system, fully releasing the inherent capacity of the cathode material is difficult and challenging, especially when matched with the mainstream hard carbon anode. The low first-cycle coulombic efficiency of hard carbon often inevitably leads to the irreversible loss of active sodium, resulting in a significant decrease in the full-cell capacity.

[0004] Given the problem of active sodium consumption and loss, developing efficient and controllable sodium replenishment technology has become a key approach to improve the performance and energy density of full batteries, and has important research and application value. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a positive electrode sheet for a battery, a method for preparing the same, and a sodium-ion battery.

[0006] In a first aspect, the present invention provides a method for preparing a positive electrode sheet for a battery, the method comprising the following steps: adding a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder to a positive electrode sodium supplementation additive solution and stirring to obtain a positive electrode slurry; then coating the obtained positive electrode slurry onto a positive electrode current collector; and then drying, rolling, and slitting the slurry to obtain the positive electrode sheet for the battery.

[0007] Preferably, the positive electrode sodium supplementation additive includes at least one of monosodium glutamate, sodium glycerate, sodium benzenesulfonate, sodium hypotriacetate, and sodium succinate.

[0008] Preferably, the solvent in the positive electrode sodium supplementation additive solution includes N-methylpyrrolidone; more preferably, the mass fraction of the positive electrode sodium supplementation additive in the solution is 1-5 wt%.

[0009] Preferably, the positive electrode active material includes at least one of layered metal oxides, Prussian blue materials, polyanionic materials, and sulfate materials; the positive electrode conductive agent includes at least one of Super P, acetylene black, carbon nanotubes, and Ketjen black; and the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0010] Preferably, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is 90-96:5-2:5-1, and the amount of the positive electrode sodium supplementing additive is 1-10 wt% of the positive electrode active material.

[0011] Preferably, the stirring rate is 200-500 rpm, the temperature is 25-35°C, and the time is 5-60 min; The positive electrode current collector is a carbon-coated aluminum foil with a thickness of 13-15 micrometers; The drying process employs vacuum drying at a temperature of 80-120℃. The temperature of the roller pressing is 80-120℃.

[0012] Secondly, the present invention provides a sodium-ion battery, the sodium-ion battery comprising the above-mentioned positive electrode sheet with sodium replenishment function.

[0013] Preferably, the initial discharge capacity of the sodium-ion battery is 70-170 mAh g. -1 Preferably, the capacity is 91-170 mAh g. -1 More preferably 100-170mAh g -1 The initial efficacy is 70-95%, preferably 80-95%, more preferably 87-95%, and the capacity retention rate after 2000 cycles at 1C is 70-95%, preferably 80-95%, more preferably 88-95%.

[0014] Beneficial effects This invention provides a novel sodium-ion battery cathode sodium replenishment agent. The sodium replenishment method is simple and easy to operate, and can be applied on a large scale in industry. Moreover, the cathode active material containing the aforementioned sodium-ion battery cathode sodium replenishment agent results in high initial coulombic efficiency and excellent cycle stability of the sodium-ion battery. Attached Figure Description

[0015] Figure 1 This is a long-cycle stability graph of the sodium-ion full cell prepared in Example 1; Figure 2 This is a long-cycle stability graph of the sodium-ion full cell prepared in Example 2. Detailed Implementation

[0016] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0017] The following is an exemplary description of a method for preparing the positive electrode sheet of a battery provided by the present invention. The preparation method may include the following steps: adding a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder to a positive electrode sodium-supplementing additive solution and stirring to obtain a positive electrode slurry; then coating the obtained positive electrode slurry onto a positive electrode current collector; and finally drying, rolling, and slitting the slurry to obtain the positive electrode sheet of the battery.

[0018] In some embodiments, the positive electrode sodium supplementation additive may include at least one of monosodium glutamate, sodium glycerate, sodium benzenesulfonate, sodium hypotriacetate, and sodium succinate.

[0019] The sodium-ion battery sodium replenishment agent provided by this invention has low environmental requirements, high safety and simple process flow. The sodium-ion battery after sodium replenishment using the positive electrode sodium replenishment additive has not only high initial coulombic efficiency and cycle stability.

[0020] In some embodiments, the solvent in the positive electrode sodium supplementation additive solution may include N-methylpyrrolidone; preferably, the mass fraction of the positive electrode sodium supplementation additive in the solution may be 1-5 wt%. The quality of the positive electrode sheet can be ensured by controlling the amount of sodium supplementation additive.

[0021] In some embodiments, the positive electrode active material may include at least one of layered metal oxides, Prussian blue materials, polyanionic materials, and sulfate materials; the positive electrode conductive agent may include at least one of Super P, acetylene black, carbon nanotubes, and Ketjen black; and the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene.

[0022] In some embodiments, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder can be 90-96:5-2:5-1, and the amount of the positive electrode sodium supplement additive can be 1-10 wt% of the positive electrode active material. By controlling the sodium supplement additive within this range, the sodium loss of the battery during the first cycle can be effectively compensated. However, if the mass is too high, it will affect the energy density of the battery.

[0023] In some embodiments, the stirring rate can be 200-500 rpm, the temperature can be 25-35°C, and the time can be 5-60 min.

[0024] In some embodiments, the positive current collector can be a carbon-coated aluminum foil with a thickness of 13-15 micrometers.

[0025] In some embodiments, the drying can be performed using vacuum drying at a temperature of 80-120°C.

[0026] In some embodiments, the temperature of the rolling process can be 80-120°C.

[0027] Furthermore, the present invention also provides a sodium-ion battery. The sodium-ion battery includes the aforementioned positive electrode sheet with sodium replenishment function.

[0028] In some embodiments, the initial discharge capacity of the sodium-ion battery can be 70-170 mAh g. -1 Preferably, it has a capacity of 91-170 mAh g. -1 More preferably 100-170mAh g -1 The initial efficacy can be 70-95%, preferably 80-95%, more preferably 87-95%, and the capacity retention rate after 2000 cycles at 1C can be 70-95%, preferably 80-95%, more preferably 88-95%.

[0029] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0030] Example 1 The method for preparing the positive electrode sheet of the battery provided in this embodiment includes the following steps: Prepare a 3 wt% sodium glutamate N-methylpyrrolidone solution, then mix the positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Super P, binder PVDF and sodium glutamate in a mass percentage of 94% : 2% : 1% : 3% until the system is homogeneous. The stirring speed is 400 rpm and the temperature is 25℃ to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil with a thickness of 14 micrometers. After drying at room temperature, it is transferred to an oven for further drying. Then, after rolling (at a temperature of 100°C) and slitting processes, the positive electrode sheet of the battery is obtained.

[0031] The prepared positive electrode was combined with hard carbon to assemble a sodium-ion full cell (components include: positive electrode, negative electrode, separator, gasket, spring sheet, and electrolyte) and electrochemical tests were performed.

[0032] Example 2 The method for preparing the positive electrode sheet of the battery provided in this embodiment includes the following steps: Prepare a 4 wt% sodium glycerate N-methylpyrrolidone solution. Then, mix the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Ketjen black, the binder PVDF, and sodium glycerate in a mass percentage ratio of 93% : 2% : 1% : 4% until the system is homogeneous. The stirring speed is 300 rpm and the temperature is 25℃ to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil with a thickness of 13 micrometers. After drying at room temperature, it is transferred to an oven for further drying. Then, after rolling (at a temperature of 120°C) and slitting processes, the positive electrode sheet of the battery is obtained.

[0033] The prepared positive electrode was combined with hard carbon to assemble a sodium-ion full cell (components include: positive electrode, negative electrode, separator, gasket, spring sheet, and electrolyte) and electrochemical tests were performed.

[0034] Example 3 The method for preparing the positive electrode sheet of the battery provided in this embodiment includes the following steps: Prepare a 5wt% sodium succinate N-methylpyrrolidone solution, then mix the positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Ketjen black, binder PVDF and sodium succinate in a mass percentage ratio of 92% : 2% : 1% : 5% until the system is homogeneous. The stirring speed is 300 rpm and the temperature is 25℃ to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil with a thickness of 13 micrometers. After drying at room temperature, it is transferred to an oven for further drying. Then, after rolling (at a temperature of 120°C) and slitting processes, the positive electrode sheet of the battery is obtained.

[0035] The prepared positive electrode was combined with hard carbon to assemble a sodium-ion full cell (components include: positive electrode, negative electrode, separator, gasket, spring sheet, and electrolyte) and electrochemical tests were performed.

[0036] Example 4 The method for preparing the positive electrode sheet of the battery provided in this embodiment includes the following steps: Prepare a 3wt% solution of trisodium hypotriacetate and N-methylpyrrolidone. Then, mix the positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Ketjen Black, the binder PVDF, and trisodium hypotriacetate in a mass percentage ratio of 94% : 2% : 1% : 3% until the system is homogeneous. The stirring speed is 300 rpm and the temperature is 25℃ to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil with a thickness of 13 micrometers. After drying at room temperature, it is transferred to an oven for further drying. Then, after rolling (at a temperature of 120°C) and slitting processes, the positive electrode sheet of the battery is obtained.

[0037] The prepared positive electrode was combined with hard carbon to assemble a sodium-ion full cell (components include: positive electrode, negative electrode, separator, gasket, spring sheet, and electrolyte) and electrochemical tests were performed.

[0038] Comparative Example 1 The method for preparing the positive electrode sheet of the battery provided in this comparative example includes the following steps: The positive electrode active material Na4Fe3(PO4)2P2O7, the conductive agent Ketjen black, and the binder PVDF were mixed in a mass percentage of 97% : 2% : 1% until the system was homogeneous. The stirring speed was 300 rpm and the temperature was 25℃ to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil with a thickness of 13 micrometers. After drying at room temperature, it is transferred to an oven for further drying. Then, it undergoes a rolling process (at a temperature of 120°C) and a slitting process to obtain the positive electrode sheet of the battery.

[0039] The prepared positive electrode was combined with hard carbon to assemble a sodium-ion full cell (components include: positive electrode, negative electrode, separator, gasket, spring sheet, and electrolyte) and electrochemical tests were performed.

[0040] Comparative Example 2 The method for preparing the positive electrode sheet of the battery provided in this comparative example includes the following steps: Prepare a 5wt% sodium oxalate N-methylpyrrolidone solution, then mix the positive electrode active material Na4Fe3(PO4)2P2O7, conductive agent Ketjen black, binder PVDF and sodium oxalate in a mass percentage ratio of 92% : 2% : 1% : 5% until the system is homogeneous. The stirring speed is 300 rpm and the temperature is 25℃ to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto carbon-coated aluminum foil with a thickness of 13 micrometers. After drying at room temperature, it is transferred to an oven for further drying. Then, after rolling (at a temperature of 120°C) and slitting processes, the positive electrode sheet of the battery is obtained.

[0041] The prepared positive electrode was combined with hard carbon to assemble a sodium-ion full cell (components include: positive electrode, negative electrode, separator, gasket, spring sheet, and electrolyte) and electrochemical tests were performed.

[0042] The full cells prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to cycle performance tests within a reasonable voltage range. The specific test methods were as follows: Charging method: After resting for 60 minutes, the cells were charged to 3.4V using a constant current of 0.1C and then rested for 10 minutes; subsequently, they were charged to 4.3V using a constant current and constant voltage of 0.05C, and the charging capacity was obtained with a cutoff current of 0.02C; Discharging method: The full cells were discharged to 2.0V using a 0.05C method, and the discharge capacity of the first cycle was obtained; Cyclic performance test: The 1C / 1C cycle performance was tested within the voltage range of 2.0V-3.4V at room temperature.

[0043] The specific capacity, first-cycle efficiency, and capacity retention after cycling of the full cells prepared in the examples and comparative examples are shown in Table 1 below: .

[0044] Comparative Example 2 uses a conventional sodium oxalate additive. Since the main decomposition voltage of sodium oxalate is above 4.3V, the battery capacity hardly changes within the test range. The sodium additive with a lower decomposition voltage used in this patent has great practical value.

[0045] Figure 1 This is a long-cycle stability graph of the sodium-ion full battery prepared in Example 1. As can be seen from the graph, the capacity of Example 1 in the first cycle is 91.35 mAh g⁻¹. -1 After 2000 cycles, the capacity retention rate was 93.6%, demonstrating good cycling stability.

[0046] Figure 2 This is a long-cycle stability graph of the sodium-ion full cell prepared in Example 2. As can be seen from the graph, the capacity of Example 2 in the first cycle is 95.30 mAh g⁻¹. -1 After 2000 cycles, the capacity retention rate was 89.2%, demonstrating good cycling stability.

[0047] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a positive electrode sheet for a battery, characterized in that, The preparation method includes the following steps: adding positive electrode active material, positive electrode conductive agent, and positive electrode binder to the positive electrode sodium supplementation additive solution and stirring to obtain a positive electrode slurry; then coating the obtained positive electrode slurry onto the positive electrode current collector; and then drying, rolling, and slitting to obtain the battery positive electrode sheet.

2. The preparation method according to claim 1, characterized in that, The positive electrode sodium supplementation additive includes at least one of monosodium glutamate, sodium glycerate, sodium benzenesulfonate, sodium hypotriacetate, and sodium succinate.

3. The preparation method according to claim 1 or 2, characterized in that, The solvent in the positive electrode sodium supplementation additive solution includes N-methylpyrrolidone; preferably, the mass fraction of the positive electrode sodium supplementation additive in the solution is 1-5 wt%.

4. The preparation method according to any one of claims 1-3, characterized in that, The positive electrode active material includes at least one of layered metal oxides, Prussian blue materials, polyanionic materials, and sulfate materials; the positive electrode conductive agent includes at least one of Super P, acetylene black, carbon nanotubes, and Ketjen black; and the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

5. The preparation method according to any one of claims 1-4, characterized in that, The mass ratio of the positive electrode active material, positive electrode conductive agent, and positive electrode binder is 90-96:5-2:5-1, and the amount of the positive electrode sodium supplement additive is 1-10 wt% of the positive electrode active material.

6. The preparation method according to any one of claims 1-5, characterized in that, The stirring rate is 200-500 rpm, the temperature is 25-35℃, and the time is 5-60 min; The positive electrode current collector is a carbon-coated aluminum foil with a thickness of 13-15 micrometers; The drying process employs vacuum drying at a temperature of 80-120℃. The temperature of the roller pressing is 80-120℃.

7. A sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode sheet with sodium replenishment function obtained by the preparation method of any one of claims 1-6.

8. The sodium-ion battery according to claim 7, characterized in that, The initial discharge capacity of the sodium-ion battery is 70-170 mAh g. -1 Preferably, it has a capacity of 91-170 mAh g. -1 More preferably 100-170mAh g -1 The initial efficacy is 70-95%, preferably 80-95%, more preferably 87-95%, and the capacity retention rate after 2000 cycles at 1C is 70-95%, preferably 80-95%, more preferably 88-95%.

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