A method for preparing a silicon negative electrode containing a conductive binder of a non-side-chain-containing n-type high-conductivity polymer material PBFDO

Abstract

The application provides a preparation method of a silicon negative electrode containing a conductive adhesive of a non-side-chain n-type high-conductivity polymer material PBFDO, and the preparation method comprises the following steps: S1, blending an organic acid, an alcohol, a salt and the PBFDO, and stirring and reacting under heating to obtain an adhesive precursor solution; S2, blending and stirring the adhesive precursor solution and an active substance, coating on a substrate, and drying to obtain the silicon negative electrode; wherein the active substance is selected from one or more of nano-silicon, micro-silicon and silicon-carbon. The adhesive is obtained by crosslinking the organic acid, the alcohol, the salt and the PBFDO with each other, the adhesive forms a three-dimensional elastic structure in situ on the surface of silicon particles, can effectively accommodate the volume change of the silicon negative electrode in the cycle process, effectively alleviates the structure damage caused by the volume change, and improves the cycle stability of the battery; meanwhile, the PBFDO effectively improves the conductivity of the silicon-based negative electrode, and realizes the practical application of the PBFDO in the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and mainly to a method for preparing a silicon anode containing a conductive binder of n-type high conductivity polymer material PBFDO without side chains. Background Technology

[0002] With the continuous development of society, people have higher requirements for the battery life of portable electronic devices and power batteries. Currently, with the continuous optimization of materials and processes, lithium-ion battery systems are gradually approaching their theoretical energy density. Therefore, in the development of high specific energy systems, it is necessary to develop anode materials with even higher theoretical specific energy.

[0003] Silicon, as a negative electrode material for lithium-ion batteries, has a low delithiation potential (approximately 0.2-0.5V, compared to Li / Li). + ) with a relatively high theoretical capacity (4200mAh g) -1 Silicon is considered a suitable anode material for next-generation high-energy-density lithium-ion batteries. However, silicon particles undergo huge volume deformation (about 300%) during charging and discharging, causing damage to the anode structure and ultimately leading to a significant reduction in cycle life. This greatly limits the use of silicon anodes.

[0004] Optimizing and improving silicon-based anode binders is a very effective and promising approach to solving the problems associated with silicon-based active materials. However, some binders currently available exhibit significant brittleness when used alone, making it difficult to resist the repeated large-volume expansion of silicon particles. Furthermore, the point contact between the conductive agent particles and silicon fails to provide sufficient electron transport efficiency. This results in significant polarization of the battery during use, hindering the full release of its capacity.

[0005] In conclusion, it is necessary to develop a new technical solution to address the defects and shortcomings of existing technologies. Summary of the Invention

[0006] This invention provides a method for preparing a silicon anode using a conductive binder containing a side-chain-free n-type high conductivity polymer material PBFDO (poly(benzodifurandione)). The method involves constructing a functional surface coating layer in situ on the surface of the silicon anode particles. Through the bonding between functional groups, an interface layer with a certain degree of elasticity is formed, exhibiting excellent mechanical properties. Furthermore, the introduction of the conductive polymer constructs a conductive network, effectively improving the conductivity of the silicon electrode and enhancing its cycle performance, thus demonstrating promising application prospects.

[0007] One object of the present invention is to provide a method for preparing a silicon anode with a conductive binder containing a side-chain-free n-type high conductivity polymer material PBFDO, characterized in that the method for preparing the silicon anode with a side-chain-free n-type high conductivity polymer material PBFDO includes the following steps:

[0008] S1. Organic acid, alcohol, salt, and PBFDO are mixed and heated and stirred to react, thus obtaining the binder precursor solution;

[0009] S2. The binder precursor liquid and active material are mixed and stirred, coated onto the substrate, and dried to obtain a silicon anode.

[0010] The active material is selected from one or more of nano-silicon, micro-silicon, and silicon carbon.

[0011] Furthermore, the organic acid is selected from one or more of ferulic acid, itaconic acid, citric acid, phytic acid, and malic acid.

[0012] Furthermore, the alcohol is selected from one or more of glycerol, ethylene glycol, isopropanol, and polyethylene glycol.

[0013] Furthermore, the salt is selected from one or more of sodium styrene sulfonate and sodium lignin sulfonate.

[0014] Furthermore, the mass ratio of the organic acid, alcohol, salt, PBFDO, and active substance is (5-20):(5-20):(1-5):(1-5):(60-80).

[0015] Furthermore, in step S1, the heating and stirring reaction is carried out at a temperature of 60-120°C for 10-15 hours.

[0016] Furthermore, in step S2, the stirring time is 0.5-2 hours.

[0017] Furthermore, in step S2, the drying temperature is 60-120℃ and the time is 16-24h.

[0018] The present invention has the following beneficial effects:

[0019] This invention provides a method for preparing a silicon anode using a conductive binder containing a side-chain-free n-type high-conductivity polymer material PBFDO. The method involves cross-linking an organic acid, alcohol, salt, and PBFDO to obtain a binder. The binder then reacts with silicon to form the silicon anode. The reaction process involves esterification between the sulfonic acid groups in the salt molecules provided in this invention, the hydroxyl groups carried by the natural oxides on the silicon particle surface, and the abundant carboxyl groups in the organic acid, resulting in cross-linking. The binder forms a three-dimensional elastic structure in situ on the silicon particle surface, effectively accommodating volume changes in the silicon anode during cycling. This effectively mitigates structural damage caused by volume changes during cycling, improving the cycle stability of silicon-based lithium-ion batteries. Simultaneously, the introduction of the n-type conductive polymer PBFDO into the binder effectively enhances the conductivity of the silicon-based anode, enabling the practical application of n-type conductive polymers in lithium-ion batteries. Attached Figure Description

[0020] Figure 1 The silicon-based anode obtained in Example 1 is shown at 0.1 mV s. -1 The CV curve.

[0021] Figure 2 The cycling performance diagram of the silicon-based anode material obtained in Example 1 when used as a lithium-ion battery anode material is shown.

[0022] Figure 3 The cycling performance diagram of the silicon-based anode material obtained in Example 2 when used as a lithium-ion battery anode material is shown.

[0023] Figure 4 The cycling performance of the silicon-based anode material obtained in Comparative Example 1 as a lithium-ion battery anode material is shown. Detailed Implementation

[0024] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0025] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0026] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0027] The following raw materials are used in this invention:

[0028] The PBFDO was developed by Professor Huang Fei, Academician Cao Yong, and Academician Ma Yuguang's team from the State Key Laboratory of Luminescent Materials and Devices at South China University of Technology. Their article, titled "A solution-processed n-type conducting polymer with ultrahigh conductivity," was published in Nature.

[0029] Polyethylene glycol, molecular weight 20,000, was purchased from Aladdin Biochemical Technology Co., Ltd.

[0030] Nano-silicon, with a particle size of 100-200nm, was purchased from Alfaesa (China) Chemical Co., Ltd.

[0031] Sodium carboxymethyl cellulose, molecular weight 700,000, was purchased from Aladdin Biochemical Technology Co., Ltd.

[0032] Carbon nanotubes, with an outer diameter of 10-20 nm, were purchased from Aladdin Biochemical Technology Co., Ltd.

[0033] Polyvinylidene fluoride, molecular weight 400,000, purchased from Aladdin Biochemical Technology Co., Ltd.

[0034] Styrene-butadiene rubber, model L-SBR-822, was purchased from Aladdin Biochemical Technology Co., Ltd.

[0035] Example 1

[0036] A method for preparing a silicon anode using a conductive binder containing a side-chain-free n-type high conductivity polymer material PBFDO includes the following steps:

[0037] S1. Mix 0.15g itaconic acid, 0.1g polyethylene glycol, 0.02g sodium lignosulfonate and 0.03g PBFDO, heat to 80℃ and stir for 10h to obtain the binder precursor liquid.

[0038] S2. The binder precursor liquid and 0.7g of nano-silicon are mixed and stirred for 0.5h, coated on the current collector copper foil, and dried at 80℃ for 16h to obtain a silicon anode sheet.

[0039] Example 2

[0040] A method for preparing a silicon anode using a conductive binder containing a side-chain-free n-type high conductivity polymer material PBFDO includes the following steps:

[0041] S1. Mix 0.2g itaconic acid, 0.05g polyethylene glycol, 0.01g sodium lignosulfonate and 0.04g PBFDO, heat to 80℃ and stir for 10h to obtain the binder precursor liquid.

[0042] S2. The binder precursor liquid and 0.7g of nano-silicon are mixed and stirred for 0.5h, coated on the current collector copper foil, and dried at 80℃ for 16h to obtain a silicon anode sheet.

[0043] Example 3

[0044] A method for preparing a silicon anode using a conductive binder containing a side-chain-free n-type high conductivity polymer material PBFDO includes the following steps:

[0045] S1. Mix 0.2g phytic acid, 0.05g polyethylene glycol, 0.01g sodium lignosulfonate and 0.04g PBFDO, heat to 80℃ and stir for 10h to obtain the binder precursor liquid.

[0046] S2. The binder precursor liquid and 0.7g of nano-silicon are mixed and stirred for 0.5h, coated on the current collector copper foil, and dried at 80℃ for 16h to obtain a silicon anode sheet.

[0047] Example 4

[0048] A method for preparing a silicon anode using a conductive binder containing a side-chain-free n-type high conductivity polymer material PBFDO includes the following steps:

[0049] S1. Mix 0.15g itaconic acid, 0.1g polyethylene glycol, 0.02g sodium lignosulfonate and 0.03g PBFDO, heat to 80℃ and stir for 10h to obtain the binder precursor liquid.

[0050] S2. The binder precursor liquid and 0.7g of nano-silicon are mixed and stirred for 0.5h, coated on the current collector copper foil, and dried at 60℃ for 16h to obtain a silicon anode sheet.

[0051] Comparative Example 1

[0052] A method for preparing a silicon anode includes the following steps:

[0053] Sodium carboxymethyl cellulose, carbon nanotubes, and nano-silicon were blended in a mass ratio of 1:2:7. Specifically, 0.05g of sodium carboxymethyl cellulose, 0.1g of carbon nanotubes, and 0.35g of nano-silicon were mixed and stirred for 0.5h, then coated onto a current collector copper foil and dried at 80℃ for 16h to obtain a silicon anode sheet.

[0054] Comparative Example 2

[0055] A method for preparing a silicon anode includes the following steps:

[0056] Polyvinylidene fluoride, carbon nanotubes, and nano-silicon were blended in a mass ratio of 1:2:7. Specifically, 0.05g of polyvinylidene fluoride, 0.1g of carbon nanotubes, and 0.35g of nano-silicon were mixed and stirred for 2.5h, coated onto a current collector copper foil, and dried at 80℃ for 16h to obtain a silicon anode sheet.

[0057] Comparative Example 3

[0058] A method for preparing a silicon anode includes the following steps:

[0059] Sodium carboxymethyl cellulose, styrene-butadiene rubber, carbon nanotubes, and nano-silicon were blended in a mass ratio of 0.5:0.5:2:7. Specifically, 0.025g of sodium carboxymethyl cellulose, 0.025g of styrene-butadiene rubber, 0.1g of carbon nanotubes, and 0.35g of nano-silicon were mixed and stirred for 0.5h. The mixture was then coated onto a copper foil current collector and dried at 80℃ for 16h to obtain a silicon anode sheet.

[0060] Comparative Example 4

[0061] The preparation method of Comparative Example 4 is the same as that of Example 1, except that:

[0062] Step S1 is modified as follows: 0.15g itaconic acid, 0.1g polyethylene glycol, 0.02g sodium lignosulfonate and 0.03g PBFDO are mixed and stirred for 10h to obtain the binder precursor solution.

[0063] Test Example 1

[0064] The performance of the silicon anodes of Examples 1-4 and Comparative Examples 1-4 was tested.

[0065] Test methods

[0066] The prepared silicon anode was transferred to an argon-filled glove box, and coin cells were assembled using lithium metal as the cathode. The separator was Celgard 2325, and the electrolyte composition was 1.0 M LiPF6 in ECD:EC = 1:1 (vol% with 5% FEC). The cells were assembled inside the glove box and sealed. After standing for 12 hours, the cells were subjected to constant current electrochemical performance testing on a charge-discharge battery testing system. Cyclic testing was performed at 0.2 Ag.-1 The current density is measured, and the voltage window is 0.01-1.5V.

[0067] Test Results

[0068] Figure 1 The silicon-based anode obtained in Example 1 is shown at 0.1 mV s. -1 The CV curve.

[0069] Figure 2 The cycling performance diagram of the silicon-based anode material obtained in Example 1 when used as a lithium-ion battery anode material is shown.

[0070] Figure 3 The cycling performance diagram of the silicon-based anode material obtained in Example 2 when used as a lithium-ion battery anode material is shown.

[0071] Figure 4 The cycling performance of the silicon-based anode material obtained in Comparative Example 1 as a lithium-ion battery anode material is shown.

[0072] Table 1 shows the cycle performance of the silicon-based anode materials obtained in Examples 1-4 and Comparative Examples 1-4 when used as anode materials for lithium-ion batteries.

[0073] Table 1. Cyclic performance test results of silicon-based anode materials obtained in Examples 1-4 and Comparative Examples 1-4 when used as anode materials for lithium-ion batteries.

[0074] project <![CDATA[Specific capacity (mAh g -1 )]]> Coulomb efficiency (%) Example 1 2032 58.66 Example 2 2016 57.45 Example 3 2011 53.45 Example 4 2019 57.95 Comparative Example 1 1409 38.24 Comparative Example 2 1699 55.44 Comparative Example 3 1912 53.79 Comparative Example 4 1458 32.78

[0075] From Table 1, Figure 1 , Figure 2 , Figure 3 It can be seen that the specific capacity of Examples 1-2 is around 2000 mAh g. -1 The silicon anode preparation method provided by this invention forms a three-dimensional elastic structure in situ on the surface of silicon particles, constructs an ester bond network with high elastic modulus and a stable SEI layer, thereby alleviating the problem of the active material of silicon anode peeling off from the current collector due to volume expansion during silicon-based battery cycling, and achieving stable operation of silicon anode with high coulombic efficiency. This has practical significance and effect on improving the cycling performance of silicon anode.

[0076] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0077] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a silicon anode using a conductive binder containing an n-type high conductivity polymer material PBFDO with no side chains, characterized in that, The method for preparing the silicon anode using the conductive binder of the n-type high conductivity polymer material PBFDO without side chains includes the following steps: S1. Organic acid, alcohol, salt, and PBFDO are mixed and heated and stirred to react, thus obtaining the binder precursor solution; S2. The binder precursor liquid and active material are mixed and stirred, coated onto the substrate, and dried to obtain a silicon anode. The active material is selected from one or more of nano-silicon, micro-silicon, and silicon carbon; The organic acid is selected from one or more of ferulic acid, itaconic acid, citric acid, phytic acid, and malic acid; The alcohol is selected from one or more of glycerol, ethylene glycol, isopropanol, and polyethylene glycol; The salt is selected from one or more of sodium styrene sulfonate and sodium lignin sulfonate; In step S1, the heating and stirring reaction is carried out at a temperature of 60-120°C for 10-15 hours.

2. The method for preparing a silicon anode with a conductive binder containing an n-type high conductivity polymer material PBFDO without side chains according to claim 1, characterized in that, The mass ratio of the organic acid, alcohol, salt, PBFDO, and active substance is (5-20):(5-20):(1-5):(1-5):(60-80).

3. The method for preparing a silicon anode with a conductive binder containing an n-type high conductivity polymer material PBFDO without side chains according to claim 1, characterized in that, In step S2, the stirring time is 0.5-2 hours.

4. The method for preparing a silicon anode with a conductive binder containing an n-type high conductivity polymer material PBFDO without side chains according to claim 1, characterized in that, In step S2, the drying temperature is 60-120℃ and the time is 16-24h.

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