Preparation method of metal lithium powder composite electrode containing BIMSM binder
By constructing a BIMSM protective layer and a three-dimensional network structure on the surface of lithium metal particles, the problems of volume expansion and interface stability of lithium metal anodes are solved, achieving high-efficiency battery performance and improved safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG CENWAY MATERIALS CO LTD
- Filing Date
- 2025-12-25
- Publication Date
- 2026-05-01
AI Technical Summary
Lithium metal anodes expand significantly in volume and exhibit poor interface stability during charging and discharging. Traditional binders cannot effectively modify the interface and pose safety hazards. Simple physical mixing processes cannot form a dense protective layer.
A stepwise strategy of pre-coating and cross-linking was adopted, using brominated isobutylene-p-methylstyrene copolymer (BIMSM) to construct a dense protective layer on the surface of lithium metal particles, and then constructing a three-dimensional network structure with styrene-butadiene rubber (SBR) and cross-linking agent. Through chemical reaction, a highly ionicly conductive LiBr interface layer was formed and the electrode cohesion was enhanced.
It effectively suppresses the volume expansion and dendrite growth of lithium metal, improves battery cycle life and coulombic efficiency, eliminates the safety risks brought by traditional aqueous binders, and ensures the stability of electrode structure and electrochemical performance.
Smart Images
Figure CN121964482A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing a lithium metal powder composite electrode, specifically a method for preparing a lithium metal powder composite electrode containing a BIMSM binder, belonging to the field of lithium metal battery technology. Background Technology
[0002] Lithium metal, due to its extremely high theoretical specific capacity and lowest redox potential, is suitable as a negative electrode material for high-energy-density batteries. However, the commercial application of lithium metal anodes faces severe challenges. First, lithium metal undergoes unlimited volume expansion and contraction during charging and discharging, leading to electrode pulverization and loss of electrical contact between the active material and the current collector. Second, uneven lithium deposition easily induces lithium dendrite growth, which can puncture the separator, causing short circuits or even safety accidents. To address these issues, lithium metal powder electrode technology attempts to reduce local current density by increasing the specific surface area. However, the high activity of lithium metal powder makes the selection of binders extremely demanding.
[0003] In existing technologies, while traditional PVDF binders are stable in organic solvents, their electronic insulation and mechanical brittleness make them ill-suited to the significant volume changes of lithium metal and ineffective at modifying interfaces. Traditional SBR (styrene-butadiene rubber) binders typically possess good elasticity, but commercially available SBRs are mostly water-emulsion systems. Since lithium metal reacts violently with water to generate hydrogen gas and lithium hydroxide, posing a significant safety hazard, even oil-soluble SBRs only provide physical bonding and lack chemically active groups, failing to induce the formation of a stable solid electrolyte interfacial film, leading to a continuous increase in interfacial impedance during cycling. Furthermore, during preparation, simple physical mixing processes cannot form a dense protective layer on the lithium powder surface, causing the lithium powder to be directly exposed to solvents or air impurities during slurry preparation and coating, resulting in activity loss. Summary of the Invention
[0004] Based on the above background, the purpose of this invention is to provide a method for preparing a lithium metal powder composite electrode containing BIMSM binder, thereby solving the technical problems of large volume expansion, poor interface stability, and incompatibility with traditional aqueous binder processes in the prior art.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0006] A method for preparing a lithium metal powder composite electrode containing BIMSM binder, the method comprising the following steps:
[0007] S1. Dissolve the brominated isobutylene-p-methylstyrene copolymer in a first organic solvent to obtain a pre-coated solution;
[0008] S2. Under an inert atmosphere, lithium metal powder is added to the pre-coated solution for dispersion and mixing, then the solvent is removed and dried to obtain modified lithium metal powder with a BIMSM layer on the surface.
[0009] S3. Disperse the modified lithium metal powder, styrene-butadiene rubber, conductive agent and crosslinking agent in a second organic solvent and mix them evenly to obtain an electrode slurry;
[0010] S4. The electrode slurry is coated onto the surface of the current collector, heated, dried, and rolled to obtain the lithium metal powder composite electrode.
[0011] The preparation method adopts a stepwise strategy of pre-coating-crosslinking. In steps S1-S2, a dense artificial organic protective layer is constructed on the surface of lithium metal particles using brominated isobutylene-p-methylstyrene copolymer (BIMSM) to isolate the lithium from subsequent solvent corrosion. In steps S3-S4, a flexible interpenetrating network structure is constructed by introducing styrene-butadiene rubber (SBR) and a crosslinking agent. The active C-Br bonds in BIMSM can not only react in situ with the lithium metal surface to generate a highly ionicly conductive LiBr interface layer, but also react with the crosslinking agent to enhance the cohesion of the electrode.
[0012] Preferably, in step S1, the benzyl bromide content in the isobutylene-p-methylstyrene copolymer is 0.5 mol%-3.0 mol%.
[0013] Limiting the content of benzyl bromide is to balance reactivity and material stability. If the content is too low, sufficient LiBr inorganic components and cross-linking points cannot be generated. If the content is too high, it may lead to excessive side reactions or premature cross-linking and hardening of the polymer, affecting flexibility.
[0014] Preferably, in step S2, the mass ratio of the lithium metal powder to the brominated isobutylene-p-methylstyrene copolymer is 100:1-5.
[0015] This ratio ensures that BIMSM primarily exists as an interface modification layer, forming a thin coating at the nanometer to submicrometer scale, without significantly increasing electron transport impedance.
[0016] Preferably, in step S3, the crosslinking agent is at least one of a polyfunctional amine compound, a polyfunctional thiol compound, or a metal oxide; the amount of crosslinking agent added is 1%-10% of the mass of the isobutylene-p-methylstyrene copolymer.
[0017] The crosslinking agent undergoes nucleophilic substitution or complexation reactions with the benzyl bromide groups on BIMSM, transforming the linear BIMSM molecular chain into a three-dimensional network structure, which significantly improves the electrode's resistance to swelling and mechanical strength under electrolyte immersion.
[0018] Preferably, in step S3, the styrene-butadiene rubber is an oil-soluble styrene-butadiene rubber; the mass ratio of the brominated isobutylene-p-methylstyrene copolymer in the modified lithium metal powder to the mass of the styrene-butadiene rubber is 6-8: 2-4.
[0019] Using oil-soluble SBR avoids the safety risks of aqueous processes. The above compounding ratio utilizes the high airtightness and adhesion of BIMSM and the high elasticity of SBR to achieve a balance between modulus and toughness.
[0020] Preferably, the first organic solvent and the second organic solvent are independently selected from one or more of toluene, xylene, cyclohexane, n-hexane or ethyl acetate.
[0021] Choosing non-polar or weakly polar solvents can effectively dissolve the polymer while maintaining chemical inertness to lithium metal, thus ensuring process safety.
[0022] Preferably, in step S4, the heating and drying temperature is 60℃-100℃, and the drying time is 2-12 hours.
[0023] This temperature range is not only used to remove solvents, but also serves as the thermal activation condition for initiating the chemical anchoring reaction between C-Br bonds and the lithium surface, as well as the crosslinking reaction of the crosslinking agent.
[0024] Preferably, in step S2, the dispersion and mixing process includes: subjecting the mixture to ultrasonic dispersion at a frequency of 20kHz-40kHz for 10-30 minutes, followed by vacuum drying under mechanical stirring; the vacuum drying temperature is 10℃-20℃ lower than the boiling point of the first organic solvent.
[0025] Ultrasonic dispersion utilizes the cavitation effect to break up the agglomeration of micron-sized lithium powder, ensuring the uniformity of BIMSM coating; low-temperature vacuum drying prevents solvent boiling from damaging the integrity of the coating layer.
[0026] Preferably, in step S3, the uniform mixing is achieved using a stepwise feeding process: the conductive agent is dispersed in a portion of the second organic solvent and subjected to high-speed shearing to obtain a conductive slurry; styrene-butadiene rubber and a crosslinking agent are added to the conductive slurry and stirred at low speed; finally, the modified lithium metal powder and the remaining second organic solvent are added and stirred under vacuum until uniform.
[0027] First, disperse the hard conductive agent, then add the soft modified lithium powder and stir gently to avoid high shear force damaging the BIMSM pre-coating layer on the surface of the lithium powder.
[0028] Preferably, in step S4, the rolling process is a hot rolling process; the roller surface temperature of the hot rolling is 45℃-75℃, and the compaction density of the electrode after rolling is controlled at 0.6 g / cm³. 3-1.0 g / cm 3 .
[0029] Hot rolling utilizes the fluidity of polymers near their glass transition temperature to fill the gaps between particles, increase the contact area, and further promote interfacial chemical bonding, reducing the elastic recovery caused by cold pressing.
[0030] Compared with the prior art, the present invention has the following advantages:
[0031] This invention discloses a method for preparing a lithium metal powder composite electrode containing BIMSM binder. Through a specific pre-coating-crosslinking process, a lithium metal powder composite electrode with a core-shell structure and a three-dimensional network framework is prepared. This lithium metal powder composite electrode effectively suppresses the volume expansion and dendrite growth of lithium metal, significantly improving the cycle life and coulombic efficiency of the battery. The active benzyl bromide groups in BIMSM can react in situ with the lithium surface during cycling to generate an inorganic interface layer rich in LiBr. LiBr has high ionic conductivity and high interface energy, which can effectively induce uniform lithium ion deposition and suppress dendrite penetration. By introducing a crosslinking agent, the linear BIMSM is connected to the SBR framework to form a three-dimensional interpenetrating network with excellent shear resistance and toughness, preventing electrode pulverization and detachment. This invention uses an all-organic solvent system, eliminating the risk of lithium metal gas explosion in traditional aqueous SBR processes. Furthermore, stepwise feeding and ultrasonic dispersion processes ensure the integrity of the micron-sized lithium powder surface coating layer, avoiding damage to the coating layer by conductive agents. Attached Figure Description
[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0033] Figure 1 This is a schematic flowchart of a method for preparing a lithium metal powder composite electrode containing BIMSM binder according to the present invention.
[0034] Figure 2 This is a comparison chart of the cycling performance of the electrodes prepared in Example 1 and Comparative Example 1 at a rate of 0.5C. Detailed Implementation
[0035] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.
[0036] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.
[0037] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this detailed description, numerous specific details are set forth to facilitate explanation and provide a thorough understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.
[0038] Example 1
[0039] like Figure 1 The preparation method of a lithium metal powder composite electrode containing BIMSM binder is shown below, with the specific steps as follows:
[0040] S1. Preparation of pre-coating solution: Dissolve 1.2 mol% benzyl bromide isobutylene-p-methylstyrene copolymer (BIMSM) in cyclohexane to prepare a 2 wt% solution.
[0041] S2. Lithium Powder Modification: Under argon protection, micron-sized lithium metal powder was added to the above solution. The mass ratio of lithium metal powder to BIMSM was controlled at 100:3. An ultrasonic disperser was turned on and treated at a frequency of 30 kHz for 20 minutes to uniformly disperse the lithium powder due to cavitation. Subsequently, vacuum drying was performed under mechanical stirring at a temperature controlled at 60℃ (below the boiling point of cyclohexane) until the solvent was completely evaporated, resulting in modified lithium metal powder with a uniform BIMSM coating on the surface.
[0042] S3. Slurry preparation (stepwise method): First, the conductive agent Super P is dispersed in xylene and dispersed by high-speed shearing for 20 minutes to obtain a conductive slurry; oil-soluble SBR and crosslinking agent diethylenetriamine are added to the conductive slurry and stirred at low speed until uniform. The mass ratio of BIMSM to SBR in the modified lithium powder is 7:3, and the amount of crosslinking agent is 5% of the mass of BIMSM; finally, the modified lithium metal powder obtained in step S2 and the remaining xylene are added and stirred at low speed in a vacuum planetary mixer for 30 minutes to obtain a uniform electrode slurry.
[0043] S4. Coating and Hot Rolling: The slurry is coated onto the copper foil current collector and vacuum dried at 80°C for 6 hours. Then, hot rolling is performed, with the roller surface temperature set at 60°C and the compaction density controlled at 0.8 g / cm³. 3 The lithium metal powder composite electrode was obtained by cutting the sheet.
[0044] Example 2
[0045] A method for preparing a lithium metal powder composite electrode containing BIMSM binder, the specific steps are the same as in Example 1, except that:
[0046] In step S2, the mass ratio of lithium metal powder to BIMSM is 100:5.
[0047] Example 3
[0048] A method for preparing a lithium metal powder composite electrode containing BIMSM binder, the specific steps are the same as in Example 1, except that:
[0049] In step S3, the crosslinking agent used is a multifunctional thiol compound, specifically pentaerythritol tetra-3-mercaptopropionate.
[0050] Comparative Example 1 (Traditional SBR Process)
[0051] The same lithium metal powder, conductive agent, and oil-soluble SBR as in Example 1 were used, but BIMSM was not used and no pre-coating treatment was performed.
[0052] Preparation process: Lithium metal powder, SBR, and conductive agent are directly mixed in xylene to form a slurry, which is then coated, dried, and cold-pressed.
[0053] Comparative Example 2 (Simple Physical Mixing)
[0054] The same raw material ratio (including BIMSM and SBR) as in Example 1 was used, but the pre-coating in step S2 and the stepwise feeding in step S3 were not performed.
[0055] Preparation process: BIMSM, SBR, conductive agent, and lithium metal powder were added to xylene in a single batch and mixed and dispersed. Due to the lack of pre-coating protection and the high shear force during the mixing process, BIMSM mainly existed in the slurry in a free form and failed to form an effective core-shell structure.
[0056] The electrodes prepared in the above examples and comparative examples were assembled into CR2032 coin cells. The counter electrode was a lithium sheet, and the electrolyte was a conventional carbonate electrolyte. Electrochemical test results are shown in Table 1. Charge-discharge cycle tests were conducted at 25°C and a rate of 0.5C. The comparative test results between Example 1 and Comparative Example 1 are shown below. Figure 2 As shown.
[0057] Table 1. Battery performance test results of Examples 1-3 and Comparative Examples 1-2
[0058]
[0059] As shown in Table 1, the ICE of Example 1 is significantly higher than that of Comparative Example 1, by approximately 8.3 percentage points. This demonstrates that the pre-coating process of BIMSM successfully constructs a dense artificial SEI film on the surface of lithium metal particles. This protective layer effectively isolates the solvent molecules and electrolyte in the electrode slurry from direct contact with the highly active lithium metal, significantly reducing the consumption of active lithium due to excessive SEI film growth and side reactions during the first charge. Comparative Example 1 uses a single SBR, which, although having a low mechanical modulus, lacks toughness and cannot chemically anchor the lithium surface. During repeated volume expansion / contraction, the SBR network rapidly breaks down, leading to the pulverization and shedding of the active material and a sharp capacity decay. In contrast, Example 1 constructs a three-dimensional interpenetrating network of BIMSM and SBR using a crosslinking agent. This network has excellent shear resistance, maintaining the integrity of the electrode structure.
[0060] Although Comparative Example 2 also contained BIMSM, the BIMSM was randomly distributed due to the simple physical mixing process, failing to form a complete coating layer. This resulted in some exposed lithium powder still undergoing side reactions, which demonstrates the necessity of the pre-coating process of this invention for achieving high coulombic efficiency. In Comparative Example 2, BIMSM was mainly free in the pores and failed to form strong chemical bonds with the lithium surface. In contrast, Example 1, through pre-coating and hot rolling, induced the C-Br bonds in BIMSM to chemically graft onto the lithium surface, achieving a transition from physical contact to chemical anchoring, thus exhibiting excellent stability during long-term cycling.
[0061] Comparing Examples 1 and 2, the ICE (ice-free ion exchange rate) decreased slightly as the BIMSM coating amount increased from 3% to 5%. This is because while a thicker polymer layer provides stronger protection, it also increases the penetration resistance of lithium ions, resulting in some lithium not being completely extracted. This indicates that the coating ratio range defined in this invention is an optimal solution balancing protection and kinetics.
[0062] Comparing Example 1 and Example 3, Example 3, which uses a thiol crosslinking agent, also maintained low impedance and high cycling stability, indicating that the crosslinking network construction strategy proposed in this invention has good universality and is not limited to a single type of crosslinking agent.
[0063] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
Claims
1. A method for preparing a lithium metal powder composite electrode containing BIMSM binder, characterized in that: The method includes the following steps: S1. Dissolve the brominated isobutylene-p-methylstyrene copolymer in a first organic solvent to obtain a pre-coated solution; S2. Under an inert atmosphere, lithium metal powder is added to the pre-coated solution for dispersion and mixing, then the solvent is removed and dried to obtain modified lithium metal powder with a BIMSM layer on the surface. S3. Disperse the modified lithium metal powder, styrene-butadiene rubber, conductive agent and crosslinking agent in a second organic solvent and mix them evenly to obtain an electrode slurry; S4. The electrode slurry is coated onto the surface of the current collector, heated, dried, and rolled to obtain the lithium metal powder composite electrode.
2. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S1, the benzyl bromide content in the isobutylene-p-methylstyrene copolymer is 0.5 mol%-3.0 mol%.
3. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S2, the mass ratio of the lithium metal powder to the brominated isobutylene-p-methylstyrene copolymer is 100:1-5.
4. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S3, the crosslinking agent is at least one of a polyfunctional amine compound, a polyfunctional thiol compound, or a metal oxide; the amount of crosslinking agent added is 1%-10% of the mass of the isobutylene-p-methylstyrene copolymer.
5. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S3, the styrene-butadiene rubber is an oil-soluble styrene-butadiene rubber; the mass ratio of the brominated isobutylene-p-methylstyrene copolymer in the modified lithium metal powder to the mass of the styrene-butadiene rubber is 6-8: 2-4.
6. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: The first organic solvent and the second organic solvent are independently selected from one or more of toluene, xylene, cyclohexane, n-hexane or ethyl acetate.
7. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S4, the heating and drying temperature is 60℃-100℃, and the drying time is 2-12 hours.
8. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S2, the dispersion and mixing process includes: subjecting the mixture to ultrasonic dispersion at a frequency of 20kHz-40kHz for 10-30 minutes, followed by vacuum drying under mechanical stirring; the vacuum drying temperature is 10℃-20℃ lower than the boiling point of the first organic solvent.
9. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S3, the uniform mixing is achieved using a stepwise feeding process: the conductive agent is dispersed in a portion of the second organic solvent and subjected to high-speed shearing to obtain a conductive slurry; styrene-butadiene rubber and a crosslinking agent are added to the conductive slurry and stirred at low speed; finally, the modified lithium metal powder and the remaining second organic solvent are added and stirred under vacuum until uniform.
10. The method for preparing a lithium metal powder composite electrode containing BIMSM binder according to claim 1, characterized in that: In step S4, the rolling process is a hot rolling process; the roller surface temperature of the hot rolling is 45℃-75℃, and the compaction density of the electrode after rolling is controlled at 0.6 g / cm³. 3 -1.0 g / cm 3 .