A kind of adhesive for lithium battery silicon-based negative electrode and preparation method thereof
A polymerized adhesive for silicon-based electrodes in lithium-ion batteries addresses conductivity and volume expansion issues by forming a cross-linked network with conductive agents, improving electrochemical performance and energy density.
Patent Information
- Application Number
- CN202211423088.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-15
- Publication Date
- 2024-12-06
- Estimated Expiration
- 2042-11-15
AI Technical Summary
Existing silicon-based negative electrodes in lithium ion batteries suffer from the silicon-based materials in lithium-ion batteries suffer from the silicon-based materials in lithium-ion batteries suffer from the silicon-based materials in lithium-ion batteries suffer from the silicon-based materials in lithium-ion batteries suffer from poor conductivity and significant volume expansion, which adversely affect electrochemical performance and cycle life.
A polymerized adhesive is prepared by reacting polyurethane prepolymer with maleimide polyethylene glycol and a silane coupling agent to form a cross-linked network structure on the silicon-based material, incorporating conductive agents like graphene and carbon nanotubes, to enhance conductivity and mitigate volume changes.
The adhesive improves the conductivity and stability of silicon-based negative electrodes, enhancing cycle performance and specific energy density of lithium-ion batteries by buffering volume expansion and reducing agglomeration.
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Figure CN115651158B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium ion battery materials, and in particular to an adhesive for a lithium battery silicon-based negative electrode and a preparation method thereof. Background Art
[0002] At present, the negative electrode active materials used in commercial lithium-ion batteries are mostly traditional graphite negative electrode materials, with a theoretical capacity of 370mAh / g, which is difficult to support the energy density level of 300Wh / kg lithium-ion batteries. However, the emergence of silicon-based materials just makes up for the current lack of lithium-ion battery energy density. It has the highest theoretical specific capacity (4200mAh / g), moderate lithium desorption potential (<0.5V vs Li + / Li) and rich reserves of 27.6%, so it has attracted great attention from researchers. However, silicon has poor conductivity and its volume expansion is as high as 300% or more when reaching the highest specific capacity, which seriously affects the cycle performance of lithium-ion batteries and ultimately leads to the deterioration of electrochemical performance, limiting its commercial application.
[0003] In recent years, in order to solve the adverse effects of volume expansion and contraction of silicon-based materials, researchers have made extensive research results from different perspectives. Among them, most of the research is based on the synthesis of silicon nanostructured materials, but this type of research has defects such as high cost and complicated process. Binders, as a "bridge" material that effectively adheres active materials and conductive agents to the current collector, perform well in maintaining the integrity of the silicon electrode structure, and thus play a vital role in controlling the electrochemical properties of lithium-ion batteries.
[0004] The existing silicon negative electrode material polyacrylic acid binder is a water-soluble polymer with high strength, high toughness and extremely strong adhesion. Polyacrylic acid can use the large number of carboxyl groups it contains or the hydroxyl groups on other auxiliary polymers such as sodium carboxymethyl cellulose to undergo partial chemical cross-linking under high temperature, thereby improving the cycle performance of the silicon negative electrode. However, its cross-linked structure is obtained by inducing an esterification reaction under high temperature. The cross-linked network structure obtained by this type of esterification reaction will show instability as the external environmental conditions change, and the degree of cross-linking of the binder cannot be quantitatively controlled, and it is impossible to completely solve the adverse effects of repeated volume changes of the silicon negative electrode during charging and discharging, resulting in serious battery capacity attenuation. Therefore, it is urgent to develop an adhesive that can both alleviate the volume expansion of silicon-based materials and improve the conductivity of silicon-based materials. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide an adhesive for lithium battery silicon-based negative electrode which can both alleviate the volume expansion of silicon-based materials and improve the conductivity of silicon-based materials and a preparation method thereof.
[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0007] A method for preparing an adhesive for a silicon-based negative electrode of a lithium battery is designed. The adhesive is polymerized on the surface of a silicon-based material. The silicon-based material contains a large number of hydroxyl active groups. The preparation method comprises the following steps:
[0008] S1: Add the polyurethane prepolymer to a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add the catalyst dibutyltin dilaurate, raise the temperature to 75-90°C, then add the prepared maleimide polyethylene glycol solution dropwise to the reactor, stir for 2-5h, and obtain a maleimide polyurethane solution;
[0009] S2: Add the silicon-based material to the maleimide polyurethane solution prepared in step S1, reduce the temperature to 50-70°C, continue stirring for 1-3 hours, then add the conductive agent modified by the silane coupling agent to the reactor, and add the initiator azobisisobutyronitrile, stir the reaction for 5-10 hours, and the silicon-based negative electrode adhesive can be obtained.
[0010] Preferably, it is characterized in that the molecular weight of the polyurethane prepolymer in step S1 is 2000-20000.
[0011] Preferably, the structural formula of the maleimide polyethylene glycol in step S1 is as shown in Formula I,
[0012]
[0013] Wherein n=5-100.
[0014] Preferably, the structural formula of the maleimide polyurethane in step S1 is as shown in Formula II,
[0015]
[0016] Wherein m=5-100, p=10-100.
[0017] Preferably, the silicon-based material in step S2 is selected from one or more of silicon monoxide, silicon nanoparticles, silicon nanowires and silicon-carbon composites.
[0018] Preferably, the conductive agent described in step S2 is selected from one or more of graphene, single-walled carbon nanotubes, thin-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon fibers.
[0019] Preferably, the silane coupling agent described in step S2 is selected from one or more of vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tri(2-methoxyethoxy)silane, vinyl triacetoxysilane, vinyl tri-tert-butoxysilane, and vinyl tri-tert-butoxyperoxysilane.
[0020] Preferably, in step S1, the mass ratio of the polyurethane prepolymer to the maleimide polyethylene glycol is 1-10:1.
[0021] Preferably, in step S2, the mass ratio of the silicon-based material, maleimide polyurethane and the conductive agent is 30-50:50-70:0.5-5.
[0022] The adhesive for the silicon-based negative electrode of a lithium battery in the present invention is prepared by the above-mentioned preparation method.
[0023] The beneficial effects of the present invention are:
[0024] The innovation of the present invention lies in the preparation of a modified silicon-based negative electrode material that can both alleviate the volume expansion of silicon-based materials and improve the conductivity of silicon-based materials. First, the hydroxyl group of maleimide polyethylene glycol reacts with the isocyanate active group of the polyurethane prepolymer under the action of a catalyst to synthesize a maleimide polyurethane containing both isocyanate active groups and double bonds, which is used as an intermediate to connect the silicon-based material and the conductive agent. The isocyanate active group preferentially reacts with the hydroxyl group on the surface of the silicon-based material, and the maleimide polyurethane is bonded to the surface of the silicon-based material through chemical bonds. In addition, the double bonds of the maleimide polyurethane and the conductive agent modified by the vinyl silane coupling agent are free radical polymerized under the action of an initiator to form a cross-linked network structure with conductive properties. Among them, polyurethane exerts its excellent elastic properties to buffer the volume expansion and contraction of silicon-based materials during charging and discharging. The rigid structure of maleimide effectively prevents unlimited volume expansion of silicon-based negative electrodes during charging. The conductive cross-linked network structure further restrains the volume expansion of silicon-based materials and improves the conductivity of silicon-based materials. The three work synergistically to effectively solve the adverse effects of repeated volume changes of silicon-based negative electrode materials in lithium-ion batteries during charging and discharging, and improve the cycle performance and rate performance of lithium-ion batteries.
[0025] The innovation of the present invention lies in that, when preparing electrode materials, the agglomeration of silicon-based materials and conductive agents is effectively avoided, and their dispersibility in the slurry is improved. At the same time, the amount of electrode adhesive and conductive agent used can be significantly reduced, the proportion of electrode active substances can be increased, and the specific energy of lithium-ion batteries can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 These are the charge and discharge cycle test results of button cells made of silicon-based negative electrode adhesives in the examples and comparative examples. DETAILED DESCRIPTION
[0027] The specific implementation methods of the present invention are described below in conjunction with examples, but the following examples are only used to illustrate the present invention in detail and do not limit the scope of the present invention in any way. Unless otherwise specified, the equipment components involved in the following examples are all conventional equipment components; unless otherwise specified, the industrial raw materials involved are all commercially available conventional industrial raw materials.
[0028] Example 1: An adhesive for a silicon-based negative electrode of a lithium battery is prepared by the following preparation method:
[0029] S1: Add 55g of polyurethane prepolymer into a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add 0.5g of catalyst dibutyltin dilaurate, raise the temperature to 80°C, then add the prepared polyethylene glycol solution containing 11.5g of maleimide dropwise into the reactor, stir for 3h, and obtain a maleimide polyurethane solution;
[0030] S2: Add 153.4 g of silicon oxide to the maleimide polyurethane solution prepared in S1, lower the temperature to 60°C, continue stirring for 2 hours, then add 2.2 g of single-walled carbon nanotubes modified with a silane coupling agent to the reactor, add initiator azobisisobutyronitrile, stir the reaction for 6 hours, and you can get a silicon-based negative electrode adhesive.
[0031] Example 2: An adhesive for a silicon-based negative electrode of a lithium battery is prepared by the following preparation method:
[0032] S1: Add 55g of polyurethane prepolymer into a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add 0.5g of catalyst dibutyltin dilaurate, raise the temperature to 80°C, then add the prepared polyethylene glycol solution containing 11.5g of maleimide dropwise into the reactor, stir for 3h, and obtain a maleimide polyurethane solution;
[0033] S2: Add 98.4 g of silicon oxide to the maleimide polyurethane solution prepared in S1, lower the temperature to 60°C, continue stirring for 2 hours, then add 1.7 g of single-walled carbon nanotubes modified with a silane coupling agent to the reactor, add initiator azobisisobutyronitrile, stir the reaction for 6 hours, and you can get a silicon-based negative electrode adhesive.
[0034] Example 3: An adhesive for a silicon-based negative electrode of a lithium battery is prepared by the following preparation method:
[0035] S1: Add 55g of polyurethane prepolymer into a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add 0.5g of catalyst dibutyltin dilaurate, raise the temperature to 80°C, then add the prepared polyethylene glycol solution containing 11.5g of maleimide dropwise into the reactor, stir for 3h, and obtain a maleimide polyurethane solution;
[0036] S2: Add 65.4 g of silicon oxide to the maleimide polyurethane solution prepared in S1, lower the temperature to 60°C, continue stirring for 2 hours, then add 1.3 g of single-walled carbon nanotubes modified with a silane coupling agent to the reactor, add initiator azobisisobutyronitrile, stir the reaction for 6 hours, and you can get a silicon-based negative electrode adhesive.
[0037] Example 4: An adhesive for a silicon-based negative electrode of a lithium battery is prepared by the following preparation method:
[0038] S1: Add 55g of polyurethane prepolymer into a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add 0.5g of catalyst dibutyltin dilaurate, raise the temperature to 80°C, then add the prepared polyethylene glycol solution containing 11.5g of maleimide dropwise into the reactor, stir for 3h, and obtain a maleimide polyurethane solution;
[0039] S2: Add 98.4 g of silicon oxide to the maleimide polyurethane solution prepared in S1, lower the temperature to 60°C, continue stirring for 2 hours, then add 0.8 g of single-walled carbon nanotubes modified with a silane coupling agent to the reactor, add initiator azobisisobutyronitrile, stir the reaction for 6 hours, and you can get a silicon-based negative electrode adhesive.
[0040] Example 5: An adhesive for a silicon-based negative electrode of a lithium battery is prepared by the following preparation method:
[0041] S1: Add 55g of polyurethane prepolymer into a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add 0.5g of catalyst dibutyltin dilaurate, raise the temperature to 80°C, then add the prepared polyethylene glycol solution containing 11.5g of maleimide dropwise into the reactor, stir for 3h, and obtain a maleimide polyurethane solution;
[0042] S2: Add 98.4 g of silicon oxide to the maleimide polyurethane solution prepared in S1, lower the temperature to 60°C, continue stirring for 2 hours, then add 3.4 g of single-walled carbon nanotubes modified with a silane coupling agent to the reactor, add initiator azobisisobutyronitrile, stir the reaction for 6 hours, and you can get a silicon-based negative electrode adhesive.
[0043] Example 6: An adhesive for a silicon-based negative electrode of a lithium battery is prepared by the following preparation method:
[0044] S1: Add 55g of polyurethane prepolymer into a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add 0.5g of catalyst dibutyltin dilaurate, raise the temperature to 80°C, then add the prepared polyethylene glycol solution containing 11.5g of maleimide dropwise into the reactor, stir for 3h, and obtain a maleimide polyurethane solution;
[0045] S2: Add 98.4 g of silicon oxide to the maleimide polyurethane solution prepared in S1, lower the temperature to 60°C, continue stirring for 2 hours, then add 8.7 g of single-walled carbon nanotubes modified with a silane coupling agent to the reactor, add initiator azobisisobutyronitrile, stir the reaction for 6 hours, and you can get a silicon-based negative electrode adhesive.
[0046] Comparative Example: A silicon-based negative electrode adhesive is prepared by the following preparation method:
[0047] S1: 11.5 g of maleimide polyethylene glycol and 8.4 g of silicon oxide are uniformly mixed in N,N-dimethylacetamide solvent to obtain a dispersion;
[0048] S2: 8.7 g of single-walled carbon nanotubes modified with a silane coupling agent are added to a reactor, and an initiator azobisisobutyronitrile is added, and the mixture is stirred and reacted for 6 hours to obtain a silicon-based negative electrode adhesive.
[0049] The performance test was performed on the adhesive for the silicon-based negative electrode of the lithium battery in the present invention and the silicon-based negative electrode adhesive in the comparative example, and the test method was as follows:
[0050] The silicon-based material adhesive prepared in each embodiment and comparative example: SP:CMC=95:3:2 mixture is modulated into a slurry with a solid content of 45%, and then the slurry is evenly coated on a copper foil, placed in an oven at 80°C for drying, taken out and pressed into sheets to obtain a silicon-based electrode, with a metal lithium sheet as a counter electrode, an electrolyte of 1.0 mol / L LiPF6 EC:DMC:EMC (volume ratio of 1:1:1), and a diaphragm of PE film, and assembled into a button battery in a glove box filled with argon atmosphere.
[0051] Charge and discharge cycle test: The charge and discharge cut-off voltage is 0.01-2.0V, and the charge and discharge cycle test is performed at 0.1C / 0.1C. Figure 1 It can be seen that compared with the comparative example and Example 3, the material cycle performance of Example 3 is better.
[0052] The present invention has been described in detail above in conjunction with the embodiments. However, those skilled in the art will appreciate that, without departing from the spirit of the present invention, the specific parameters in the above embodiments may be changed to form a plurality of specific embodiments, which are all within the common variation range of the present invention and will not be described in detail herein.
Claims
1. A method for preparing an adhesive for a silicon-based negative electrode of a lithium battery, characterized in that: The adhesive is polymerized on the surface of a silicon-based material, and the silicon-based material contains a large number of hydroxyl active groups. The preparation method thereof comprises the following steps: S1: Add the polyurethane prepolymer to a reactor containing N,N-dimethylacetamide solvent, stir until completely dissolved, add the catalyst dibutyltin dilaurate, raise the temperature to 75-90°C, then add the prepared maleimide polyethylene glycol solution dropwise to the reactor, stir for 2-5h, and obtain a maleimide polyurethane solution; S2: adding the silicon-based material to the maleimide polyurethane solution prepared in step S1, lowering the temperature to 50-70°C, continuing stirring for 1-3 hours, then adding the conductive agent modified by the silane coupling agent to the reactor, and adding the initiator azobisisobutyronitrile, stirring and reacting for 5-10 hours, and then obtaining the silicon-based negative electrode adhesive; The structural formula of maleimide polyethylene glycol in step S1 is shown in Formula I, Where n = 5-100; The structural formula of the maleimide polyurethane in step S1 is shown in Formula II, Where m = 5-100, p = 10-100; The silane coupling agent described in step S2 is selected from one or more of vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tri(2-methoxyethoxy)silane, vinyl triacetoxysilane, vinyl tri-tert-butoxysilane, and vinyl tri-tert-butoxyperoxysilane.
2. The method for preparing an adhesive for a silicon-based negative electrode of a lithium battery as claimed in claim 1, characterized in that the molecular weight of the polyurethane prepolymer in step S1 is 2000-20000.
3. The method for preparing an adhesive for a silicon-based negative electrode of a lithium battery as claimed in claim 1, characterized in that the silicon-based material described in step S2 is selected from one or more of silicon monoxide, silicon nanoparticles, silicon nanowires and silicon-carbon composites.
4. The method for preparing an adhesive for a silicon-based negative electrode of a lithium battery as claimed in claim 1, characterized in that the conductive agent described in step S2 is selected from one or more of graphene, single-walled carbon nanotubes, thin-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon fibers.
5. The method for preparing an adhesive for a silicon-based negative electrode of a lithium battery as claimed in claim 1, characterized in that, in step S1, the mass ratio of the polyurethane prepolymer to the maleimide polyethylene glycol is 1-10:
1.
6. The method for preparing an adhesive for a silicon-based negative electrode of a lithium battery as claimed in claim 1, characterized in that, in step S2, the mass ratio of the silicon-based material, maleimide polyurethane and the conductive agent is 30-50:50-70:0.5-5.
7. An adhesive for a silicon-based negative electrode of a lithium battery, characterized in that the adhesive is prepared by the preparation method according to any one of claims 1 to 6.