Sodium-ion battery hard carbon negative pole piece and sodium-ion battery

Abstract

The invention discloses a sodium ion battery hard carbon negative electrode pole piece, raw materials comprise a hard carbon negative electrode material, a water-based binder and a conductive agent, and the water-based binder is tannic acid. The first week coulombic efficiency of the sodium-ion battery prepared by using the hard carbon negative electrode plate of the sodium-ion battery can reach about 89%, the cycle performance of more than 700 circles can be stably maintained, and the hard carbon negative electrode plate has a wide commercialization prospect.

Description

Technical Field

[0001] The present invention belongs to the field of sodium ion batteries, and in particular relates to a sodium ion battery hard carbon negative electrode sheet and a sodium ion battery. Background Art

[0002] Fossil fuels have been the main source of energy since the Industrial Revolution. However, its use has caused irreversible harm to the natural environment. Limited fossil fuel reserves coupled with growing energy demand will inevitably lead to a serious energy crisis. Therefore, the development of pollution-free, renewable green energy is imminent and has broad application prospects in many energy storage systems. Sodium-ion batteries have been considered as ideal energy storage systems in recent years due to their abundant sodium resources, low cost, and similar sodium storage mechanism to lithium-ion batteries. Sodium-ion batteries have low cost, long cycle life and high safety performance, and are expected to play an important role in new energy storage technology and effectively solve the limitations of lithium-ion batteries. However, due to the low first-week coulombic efficiency of hard carbon anodes, the large-scale commercial application of hard carbon materials and sodium-ion batteries is seriously restricted.

[0003] Regulating the composition and morphology of the solid electrolyte interface (SEI) through polar functional groups is an effective method to achieve high first-cycle coulombic efficiency of hard carbon, but conventional surface coating methods and electrolyte regulation methods have disadvantages such as complex operation, high cost, and difficulty in large-scale operation.

[0004] In view of the above problems, it is very important to develop a convenient and efficient method to improve the first-cycle Coulombic efficiency of hard carbon. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a sodium ion battery hard carbon negative electrode plate and a sodium ion battery.

[0006] The raw materials of the sodium ion battery hard carbon negative electrode plate of the present invention include hard carbon negative electrode material, aqueous binder and conductive agent, and the aqueous binder is tannic acid.

[0007] The above-mentioned aqueous binder, namely tannic acid, has the advantages of low cost and environmental friendliness, and has rich polar functional groups (including ester groups and phenol groups), which can induce the decomposition of the electrolyte to form a thinner and more uniform SEI layer, effectively improving the first-week coulombic efficiency and cycle stability of the hard carbon half-cell.

[0008] The mass percentage of the hard carbon negative electrode material is 70%-95%, the mass percentage of tannic acid is 2.5%-10%, and the mass percentage of the conductive agent is 2.5%-20%.

[0009] Furthermore, the mass percentage of the hard carbon negative electrode material is 80%-90%, the mass percentage of tannic acid is 5%-10%, and the mass percentage of the conductive agent is 5%-10%.

[0010] The present invention also provides a method for preparing the above-mentioned hard carbon negative electrode sheet for a sodium ion battery, comprising the following steps:

[0011] (1) preparing a negative electrode slurry: mixing the hard carbon negative electrode material, tannic acid and conductive agent in proportion, and then adding deionized water and stirring to mix evenly to obtain a negative electrode slurry;

[0012] (2) Preparation of a sodium ion battery hard carbon negative electrode sheet: The negative electrode slurry is coated on a current collector, and dried at 60°C-100°C for 6-10 hours to obtain a sodium ion battery hard carbon negative electrode sheet.

[0013] The present invention also provides a sodium ion battery, which comprises the above-mentioned sodium ion battery hard carbon negative electrode sheet or a sodium ion battery hard carbon negative electrode sheet prepared using the above-mentioned method for preparing the sodium ion battery hard carbon negative electrode sheet.

[0014] Beneficial effects: The aqueous binder provided by the present invention, namely tannic acid, has abundant polar functional groups, which can induce the decomposition of the electrolyte in the electrochemical process to form a thin and uniform SEI layer with a high content of inorganic components. The stable SEI is beneficial to the storage and release of sodium ions by the hard carbon material in the electrochemical process; the first-week coulomb efficiency of the sodium ion half-cell using the aqueous binder, namely tannic acid, can reach about 89%, and the cycle performance of more than 700 cycles can be stably maintained, which has broad commercial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the constant current charge and discharge curve of the first cycle of the sodium ion battery of the present invention;

[0016] Figure 2 It is a schematic diagram of the capacity retention rate of the sodium ion battery cycle test curve of the present invention. DETAILED DESCRIPTION

[0017] The present invention will now be further described in detail by way of embodiments in conjunction with the accompanying drawings, but the present invention is not limited to the embodiments.

[0018] Example 1

[0019] (1) Preparation of negative electrode slurry: 80 parts by mass of hard carbon material, 10 parts by mass of conductive carbon black (Temeco, Switzerland) as a conductive agent and 10 parts by mass of tannic acid (Aladdin) as an aqueous binder are uniformly mixed, and then deionized water as a solvent is added and stirred to mix evenly, keeping the solid content at 40%-50% to prepare battery electrode slurry; the above-mentioned hard carbon material is type 2 hard carbon produced by Kuraray.

[0020] (2) Preparation of negative electrode sheets: Use a scraper to evenly apply the above battery electrode sheet slurry on the current collector aluminum foil (or copper foil), place it in a forced air drying oven at 60°C for 2 hours, and then place it in a vacuum drying oven at 80°C for 6 hours. Use a cutting machine to cut the dried battery negative electrode sheets into circular electrode sheets with a diameter of 12 mm, thus obtaining the sodium ion battery hard carbon negative electrode sheets.

[0021] Button half-cell assembly and testing: In a glove box filled with argon, the pole piece, glass fiber diaphragm, electrolyte, sodium sheet, spring and gasket are packaged with positive and negative electrode shells to obtain a button half-cell, in which the sodium sheet size is 14mm in diameter and the electrolyte is 1M NaPF6 ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) solution. At the same time, the constant current method is used to test the first cycle charge and discharge performance and cycle stability of the sodium ion half-cell, with a potential window of 0.01-2.5V, a first cycle charge and discharge test current density of 50mAg-1, and a cycle stability test current density of 200mAg-1.

[0022] Example 2

[0023] In Example 1, the process is the same as that of Example 1 except that “80 parts by mass” of the hard carbon material is changed to “85 parts by mass” and “10 parts by mass” of the conductive carbon black is changed to “5 parts by mass”.

[0024] Example 3

[0025] In Example 1, the hard carbon material "80 parts by mass" was changed to "90 parts by mass", the conductive carbon black "10 parts by mass" was changed to "5 parts by mass", and the tannic acid "10 parts by mass" was changed to "5 parts by mass". Other than this, it is the same as Example 1.

[0026] Example 4

[0027] In Example 1, the process is the same as that of Example 1 except that “80 parts by mass” of the hard carbon material is changed to “70 parts by mass” and “10 parts by mass” of the conductive carbon black is changed to “20 parts by mass”.

[0028] Example 5

[0029] In Example 1, the process is the same as Example 1 except that "type 2 hard carbon manufactured by Kuraray Co., Ltd." is replaced by "BSHC-330 hard carbon manufactured by B&T Corporation."

[0030] Example 6

[0031] In Example 1, the hard carbon material "80 parts by mass" is changed to "85 parts by mass", the conductive carbon black "10 parts by mass" is changed to "5 parts by mass", and the "type 2 hard carbon of Kuraray" is changed to "BSHC-330 hard carbon of BYD". Other than this, it is the same as Example 1.

[0032] Example 7

[0033] In Example 1, the hard carbon material "80 parts by mass" is changed to "90 parts by mass", the conductive carbon black "10 parts by mass" is changed to "5 parts by mass", the tannic acid "10 parts by mass" is changed to "5 parts by mass", and the "type 2 hard carbon of Kuraray" is changed to "BSHC-330 hard carbon of BYD". Other than this, it is the same as Example 1.

[0034] Comparative Example 1

[0035] In Example 1, the process is the same as that of Example 1 except that "tannic acid" is replaced by "polyvinylidene fluoride" and the solvent "deionized water" is replaced by "N-methylpyrrolidone". The polyvinylidene fluoride and N-methylpyrrolidone may be commercially available products.

[0036] Comparative Example 2

[0037] In Example 1, the process is the same as that of Example 1 except that "tannic acid" is changed to "carboxymethyl cellulose". The carboxymethyl cellulose may be a commercially available product.

[0038] Comparative Example 3

[0039] In Example 1, the process is the same as that of Example 1 except that "tannic acid" is changed to "polyacrylamide". The polyacrylamide may be a commercially available product.

[0040] Comparative Example 4

[0041] In Example 1, "tannic acid" is changed to "polyvinylidene fluoride", the solvent "deionized water" is changed to "N-methylpyrrolidone", and "type 2 hard carbon of Kuraray" is changed to "BSHC-330 hard carbon of B&T", and other than this, it is the same as Example 1.

[0042] Comparative Example 5

[0043] In Example 1, the process is the same as Example 1 except that “tannic acid” is replaced by “carboxymethyl cellulose” and “type 2 hard carbon manufactured by Kuraray Co., Ltd.” is replaced by “BSHC-330 hard carbon manufactured by B&T Corporation.”

[0044] Comparative Example 6

[0045] In Example 1, the process is the same as Example 1 except that “tannic acid” is replaced by “polyacrylamide” and “type 2 hard carbon manufactured by Kuraray” is replaced by “BSHC-330 hard carbon manufactured by B&T”.

[0046] Table 1 Sodium ion battery half-cell performance test results of Examples 1-7 and Comparative Examples 1-6

[0047] serial number First week coulomb efficiency Example 1 88.7％ Example 2 87.1％ Example 3 86.0％ Example 4 80.9％ Example 5 85.1％ Example 6 84.9％ Example 7 84.6％ Comparative Example 1 72.3％ Comparative Example 2 80.5％ Comparative Example 3 81.2％ Comparative Example 4 71.8％ Comparative Example 5 79.6％ Comparative Example 6 81.6％

[0048] From the data in Table 1, it can be seen that the first-week coulombic efficiency of the sodium ion half-cells of Examples 1-7 using the aqueous binder of the present invention, namely tannic acid, is generally high, and it is shown that the aqueous binder of the present invention, namely tannic acid, is suitable for a variety of commercial hard carbons.

[0049] Figure 1 The first-week charge and discharge curve comparison diagram of the sodium ion half-cell of Example 1 and Comparative Examples 1-3 shows that the binder in Example 1 significantly improves the first-week coulombic efficiency of the hard carbon negative electrode.

[0050] Figure 2 This is the cycle performance diagram of the sodium ion half-cell of Example 1. It can be seen that the hard carbon negative electrode using the aqueous binder of the present invention, namely tannic acid, has excellent cycle performance, and the excellent SEI induced by the binder is beneficial to the long cycle performance of the battery.

[0051] The above-mentioned technologies not specifically mentioned are all referred to the prior art.

[0052] Based on the above-mentioned ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above-mentioned description. The technical scope of the present invention is not limited to the contents of the specification.

Claims

1. A sodium ion battery hard carbon negative electrode plate, characterized in that: The raw materials include hard carbon negative electrode material, water-based binder and conductive agent, and the water-based binder is tannic acid.

2. The sodium ion battery hard carbon negative electrode sheet according to claim 1, characterized in that: The mass percentage of the hard carbon negative electrode material is 70%-95%, the mass percentage of tannic acid is 2.5%-10%, and the mass percentage of the conductive agent is 2.5%-20%.

3. The hard carbon negative electrode sheet for sodium ion battery according to claim 2, characterized in that: The mass percentage of the hard carbon negative electrode material is 80%-90%, the mass percentage of tannic acid is 5%-10%, and the mass percentage of the conductive agent is 5%-10%.

4. The method for preparing the hard carbon negative electrode sheet for a sodium ion battery according to any one of claims 1 to 3, comprising the following steps: (1) preparing negative electrode slurry: mixing the hard carbon negative electrode material, tannic acid and conductive agent in proportion, and then adding deionized water and stirring to mix evenly to obtain negative electrode slurry; (2) Preparing a hard carbon negative electrode sheet for a sodium ion battery: coating the negative electrode slurry on a current collector, and drying the mixture at 60° C. to 100° C. for 6 to 10 hours to obtain a hard carbon negative electrode sheet for a sodium ion battery.

5. A sodium ion battery, characterized in that: A sodium ion battery hard carbon negative electrode sheet comprising any one of claims 1 to 3 or a sodium ion battery hard carbon negative electrode sheet prepared using the method for preparing a sodium ion battery hard carbon negative electrode sheet according to claim 4.

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