Lithium ion battery silicon negative electrode binder and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly discloses a lithium ion battery silicon negative electrode binder and a preparation method and application thereof. The lithium ion battery silicon negative electrode binder comprises the following components in parts by weight: 0-10 parts of Arabic gum and / or 0-10 parts of sodium alginate. The invention discloses a lithium ion battery silicon negative electrode binder and a preparation method and application thereof, the lithium ion battery silicon negative electrode binder has high viscosity and a network cross-linked structure, effectively inhibits the volume expansion and rebound phenomena of a silicon negative electrode in the charging and discharging process, and significantly improves the stability of the silicon negative electrode in the long cycle process.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium - ion batteries, and particularly relates to a binder for a silicon anode of a lithium - ion battery, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of lithium - ion battery technology, finding high - performance anode materials to meet the increasing energy density requirements has become a research hotspot. Silicon, due to its high theoretical specific capacity (3592 mAh / g), is considered an ideal material to replace traditional graphite anodes and is expected to significantly improve the energy density of lithium - ion batteries.

[0003] However, silicon faces a serious volume expansion problem during lithiation, with an expansion rate of up to 300%. This drastic volume change can lead to the destruction of the electrode structure, thereby shortening the service life of lithium - ion batteries. Although reducing silicon particles to the nanoscale or using carbon - based coating materials can partially alleviate the volume expansion effect, these methods do not fundamentally solve the stress accumulation problem caused by volume expansion.

[0004] In terms of the mechanical properties of the electrode, existing polymer binders are difficult to stably support the mechanical strain of silicon - based anodes for a long time due to structural fatigue. The expansion and contraction of silicon particles during charge and discharge may cause them to peel off from the current collector, leading to battery short - circuit. In addition, in terms of electrode chemistry, the inherent large volume change of silicon particles during lithiation / delithiation can cause instability in the electrode microstructure and solid electrolyte interface (SEI). The continuous accumulation of SEI not only hinders the electrode reaction kinetics but also irreversibly traps lithium ions, further exacerbating the capacity decay and early failure of the battery. Summary of the Invention

[0005] The present invention aims to provide a binder for a silicon anode of a lithium - ion battery, a preparation method thereof, and an application thereof. The binder for a silicon anode of a lithium - ion battery has a high viscosity and a network cross - linked structure, effectively inhibits the volume expansion and rebound phenomenon of the silicon anode during charge and discharge, and significantly improves the stability of the silicon anode during long - term cycling.

[0006] To solve the above - mentioned technical problems, the technical solution adopted by the present invention is as follows: A binder for a silicon anode of a lithium - ion battery, comprising the following components in parts by weight: 0 - 10 parts of gum arabic and / or 0 - 10 parts of sodium alginate.

[0007] Preferably, the binder further comprises glutaraldehyde, and the addition amount of glutaraldehyde is 1% - 5% of the gum arabic.

[0008] The present invention also provides a preparation method of the binder for a silicon anode of a lithium - ion battery as described above, comprising the following steps: S1. Dissolve gum arabic in deionized water to obtain a viscous solution; S2. Add sodium alginate to the viscous solution obtained in S1, mix evenly, drop glutaraldehyde solution, stir evenly, vacuum dry, grind and sieve to obtain a silicon negative electrode binder for lithium ion batteries.

[0009] Preferably, in S1, the gum arabic is dissolved in deionized water at 80° C. to obtain a viscous solution.

[0010] Preferably, in S2, after the glutaraldehyde solution is added dropwise, the mixture is stirred at 60-120° C. for 1-5 hours.

[0011] Preferably, in S2, the vacuum drying conditions are as follows: vacuum degree is -0.1 MPa, drying temperature is 80°C, and drying time is 24 h.

[0012] The present invention also provides the use of the lithium ion battery silicon negative electrode binder or the lithium ion battery silicon negative electrode binder prepared by the preparation method in preparing lithium ion battery silicon negative electrode plate materials.

[0013] The present invention also provides a silicon negative electrode sheet material for a lithium ion battery, wherein the silicon negative electrode material contains the lithium ion battery silicon negative electrode binder.

[0014] The present invention also provides a method for preparing the silicon negative electrode sheet material for a lithium ion battery, comprising the following steps: T1, mixing silicon powder, lithium-ion battery silicon negative electrode binder and conductive agent, adding deionized water and stirring thoroughly to obtain a uniform slurry; T2. The slurry obtained in T1 is uniformly coated on the copper foil, preheated in vacuum at 80-150° C. for 3 h, and then dried in vacuum to obtain a dry silicon negative electrode sheet material.

[0015] Preferably, in T1, the mass ratio of the silicon powder, the lithium-ion battery silicon negative electrode binder and the conductive agent is 7:1:2-8:1:1.

[0016] Preferably, in T2, the specific conditions of the vacuum drying are: vacuum degree of -0.1 MPa, drying temperature of 60-120°C, and drying time of 24 h.

[0017] Preferably, the dried silicon negative electrode sheet material is cut to obtain a lithium-ion battery silicon negative electrode sheet, and the negative electrode sheet has a diameter of 12 mm.

[0018] Preferably, the silicon powder loading of each negative electrode sheet is 0.8-1.5 mg cm -2 .

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The present invention discloses a binder for silicon negative electrode of lithium-ion battery, its preparation method and application. The raw materials used for this binder for silicon negative electrode of lithium-ion battery are non-toxic, harmless, widely sourced and low-cost. The preparation process is simple, with low energy consumption, and no redundant waste or waste liquid is generated, which conforms to the concept of green environmental protection and has great commercial application prospects.

[0020] (2) For this binder for silicon negative electrode of lithium-ion battery, by adding gum arabic to form a polycationic electrolyte after dissolving in water, the conductivity of the binder is significantly improved. Its amphiphilic property of water and oil can effectively regulate the surface tension of the slurry, solve the cracking problem during the thick coating process, and at the same time ensure good wettability of the electrode sheet to the electrolyte. Crosslinking sodium alginate and gum arabic molecules through glutaraldehyde forms a stable network structure, extends the molecular chain, and forms multiple interactions of chemical bonds, hydrogen bonds and van der Waals forces with the surface of the silicon negative electrode through rich carboxyl and hydroxyl functional groups, significantly enhancing the adhesion force, effectively inhibiting the volume expansion and rebound phenomenon of the silicon negative electrode during charge and discharge, significantly improving the stability of the silicon negative electrode during long-term cycling, and extending the service life of the lithium-ion battery.

[0021] The technical solution of the present invention will be further described in detail below through the accompanying drawings and examples. Description of the Drawings

[0022] Figure 1 is the cycling performance of Example 1 at different current densities; Figure 2 is the rate performance of Example 1 at different current densities. Detailed Embodiments

[0023] The technical solution of the present invention will be further described below through the accompanying drawings and examples.

[0024] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those with ordinary skills in the field to which the present invention belongs.

[0025] In the present invention, unless otherwise specified, other test materials and instrument equipment are all conventional test materials in this field and can be obtained through commercial channels.

[0026] Example 1 A binder for silicon negative electrode of lithium-ion battery, and the preparation method includes the following steps: S1. Dissolve 0.8 g of gum arabic in 30 mL of deionized water at 80 °C to obtain a viscous solution; S2. Add 0.2 g of sodium alginate to the viscous solution obtained in S1, mix evenly, dropwise add 0.024 g of glutaraldehyde solution, stir at 80 °C for 3 h, dry at 80 °C under a vacuum of -0.1 MPa for 24 h, grind and sieve to obtain the binder for the silicon negative electrode of the lithium-ion battery.

[0027] This example also provides a silicon negative electrode sheet material for a lithium-ion battery, and the preparation method includes the following steps: T1. Mix silicon powder, the above-mentioned binder for the silicon negative electrode of the lithium-ion battery, and a conductive agent according to a mass ratio of 7:1:2, add 3 mL of deionized water and stir well to obtain a uniform slurry, wherein grind the above-mentioned binder for the silicon negative electrode of the lithium-ion battery and sieve it through a 500-mesh sieve; T2. Uniformly coat the slurry obtained in T1 on a copper foil, preheat it in a vacuum at 120 °C for 3 h, and then vacuum dry it at 80 °C under a vacuum of -0.1 MPa for 24 h to obtain a dried silicon negative electrode sheet material.

[0028] Example Two The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.9 g and the addition amount of sodium alginate is 0.1 g.

[0029] Example Three The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.7 g and the addition amount of sodium alginate is 0.3 g.

[0030] Example Four The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.6 g and the addition amount of sodium alginate is 0.4 g.

[0031] Example Five The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.5 g and the addition amount of sodium alginate is 0.5 g.

[0032] Example Six The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.4 g and the addition amount of sodium alginate is 0.6 g.

[0033] Example Seven The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.3 g and the addition amount of sodium alginate is 0.7 g.

[0034] Example Eight The preparation method is the same as that of Example One, except that the addition amount of gum arabic is 0.2 g and the addition amount of sodium alginate is 0.8 g.

[0035] Example Nine The preparation method is the same as that of Example 1, except that the addition amount of gum arabic is 0.1 g and the addition amount of sodium alginate is 0.9 g.

[0036] Example 10 The preparation method is the same as that of Example 1, except that the addition amount of glutaraldehyde is 0.008 g.

[0037] Example 11 The preparation method is the same as that of Example 1, except that the addition amount of glutaraldehyde is 0.016 g.

[0038] Example 12 The preparation method is the same as that of Example 1, except that the addition amount of glutaraldehyde is 0.032 g.

[0039] Example 13 The preparation method is the same as that of Example 1, except that the addition amount of glutaraldehyde is 0.04 g.

[0040] Comparative Example 1 An adhesive, and the preparation method includes the following steps: S1. Dissolve 1.0 g of gum arabic in 30 mL of deionized water at 80 °C to obtain a viscous solution; S2. Dry the viscous solution obtained in S1 at a vacuum degree of -0.1 MPa and 80 °C for 24 h, grind and sieve it to obtain a lithium-ion battery silicon anode binder.

[0041] A silicon anode sheet material for a lithium-ion battery, and the preparation method includes the following steps: T1. Stir 7:1:2 by mass of silicon powder, the above-mentioned binder and a conductive agent with 30 mL of deionized water to obtain a uniform slurry, wherein grind the above-mentioned lithium-ion battery silicon anode binder and sieve it through a 500-mesh sieve; T2. Uniformly coat the slurry obtained in T1 on a copper foil, preheat it in vacuum at 120 °C for 3 h, and then vacuum-dry it at a vacuum degree of -0.1 MPa and 80 °C for 24 h to obtain a dried silicon anode sheet material.

[0042] Comparative Example 2 The preparation method is the same as that of Comparative Example 1, except that the binder raw material is 1.0 g of sodium alginate.

[0043] Perform performance tests on the silicon anode sheet materials provided in the above examples and comparative examples.

[0044] Respectively cut the above-mentioned silicon anode sheet materials to obtain negative electrode sheets with a diameter of 12 mm, and the silicon powder loading amount of each negative electrode sheet is 0.8 mg cm -2 . Use the above-mentioned negative electrode sheets to prepare a lithium-ion battery, including the following steps: The assembly of the coin cell was completed in a glove box (with water and oxygen contents both below 0.01 ppm).

[0045] The fabricated negative electrode sheet was used as the negative electrode, the positive electrode was a lithium sheet (with a diameter of 15 mm), the separator was polypropylene, and the electrolyte was lithium hexafluorophosphate. Assembly was carried out in the order of negative electrode sheet, electrolyte, separator, electrolyte, and positive electrode sheet, and then it was sealed with a hydraulic sealer to obtain a lithium-ion battery.

[0046] The above-obtained lithium-ion battery was subjected to electrochemical performance tests, and the results are shown in Table 1 and Figure 1-2 as follows.

[0047] Table 1 Electrochemical performance of lithium-ion batteries

[0048] As can be seen from Table 1, compared with the comparative example, the example has higher ICE and capacity, and the capacity retention rate is more excellent after 300 cycles. Among them, the ICE of Example 1 is as high as 74.5%. After 300 cycles, the capacity retention rate is as high as 60% and the specific capacity is 1633.9 mAh / g, indicating that using gum arabic as the binder component of the silicon negative electrode of the lithium-ion battery, its amphiphilic property can effectively regulate the surface tension of the slurry and improve its electrochemical performance.

[0049] As Figure 1 can be seen, for Example 1 at a high current density of 1.0 A / g, the remaining capacity retention rate is still 60.0% after 300 cycles; as Figure 2 can be seen, for the cycling performance of Example 1 at different current densities, after returning from a current density of 3.2 A / g to a current density of 0.2 A / g, a stable capacity is still maintained during subsequent cycling, indicating that the material has excellent structural stability. At the same time, this network cross-linked structure binder makes the electrode interface not easily degrade during cycling at various rates.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A lithium ion battery silicon negative electrode binder, characterized in that: The invention comprises the following components in parts by weight: 0-10 parts of gum arabic and / or 0-10 parts of sodium alginate.

2. The lithium ion battery silicon negative electrode binder according to claim 1, characterized in that: The binder also includes glutaraldehyde, and the added amount of glutaraldehyde is 1%-5% of the gum arabic.

3. A method for preparing a silicon negative electrode binder for a lithium ion battery as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Dissolve gum arabic in deionized water to obtain a viscous solution; S2. Add sodium alginate to the viscous solution obtained in S1, mix evenly, drop glutaraldehyde solution, stir evenly, vacuum dry, grind and sieve to obtain a silicon negative electrode binder for lithium ion batteries.

4. The preparation method according to claim 3, characterized in that: In S1, gum arabic is dissolved in deionized water at 80° C. to obtain a viscous solution.

5. The preparation method according to claim 3, characterized in that: In S2, after the glutaraldehyde solution is added dropwise, the mixture is stirred at 60-120° C. for 1-5 hours.

6. The preparation method according to claim 3, characterized in that: In S2, the vacuum drying conditions are specifically as follows: vacuum degree is -0.1 MPa, drying temperature is 80°C, and drying time is 24 h.

7. Use of the lithium ion battery silicon negative electrode binder according to any one of claims 1 to 2 or the lithium ion battery silicon negative electrode binder prepared by the preparation method according to any one of claims 3 to 6 in preparing lithium ion battery silicon negative electrode sheet materials.

8. A silicon negative electrode material for a lithium-ion battery, characterized in that: The silicon negative electrode material contains the lithium ion battery silicon negative electrode binder according to any one of claims 1-2.

9. A method for preparing a silicon negative electrode sheet material for a lithium-ion battery as claimed in claim 8, characterized in that: The steps include: T1, mixing silicon powder, lithium-ion battery silicon negative electrode binder and conductive agent, adding deionized water and stirring thoroughly to obtain a uniform slurry; T2. The slurry obtained in T1 is uniformly coated on the copper foil, preheated in vacuum at 80-150°C for 3 h, vacuum dried, and cut to obtain a dry silicon negative electrode sheet material.

10. The preparation method according to claim 9, characterized in that: In T2, the specific conditions of vacuum drying are: vacuum degree of -0.1 MPa, drying temperature of 60-120°C, and drying time of 24 h.

Images