Silicon Anode Composite Layer for Volume Expansion and Conductivity
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Solution Overview
Problem
Silicon-based anode materials for lithium ion batteries face challenges with low reversible capacity and poor cycle stability due to severe volume expansion and poor conductivity, despite efforts like conductive polymer coating and carbon coating, which often result in unstable conductivity and complex preparation processes.
Innovation Solution
A silicon-based anode material is developed by integrating flake graphite with a flexible polymer and nano-carbon based materials, forming a composite layer that inhibits expansion and enhances conductivity stability, using a simple and cost-effective preparation method involving solvent-based coating and heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductive polymer coating is applied through in-situ polymerization to improve conductivity, then conductivity is enhanced, but the preparation process becomes complicated and conductivity stability deteriorates
Solution Approach 1:
The patent uses a binder as an intermediary substance to attach conductive polymer particles and carbon particles to the silicon-based active material surface. This binder-mediated approach simplifies the preparation process compared to in-situ polymerization while ensuring stable conductivity through proper adhesion of conductive components.
Solution Approach 2:
The patent creates a composite coating structure combining conductive polymer particles, carbon particles, and binder on the silicon-based active material surface. This composite approach provides both conductivity enhancement and stability while using a straightforward preparation process involving dispersion and coating.
2Quantity of substance
If silicon-based material is used to achieve high specific capacity, then theoretical capacity increases to 4,200 mAh/g, but volume expansion effect worsens and cycle stability deteriorates
Solution Approach 1:
The patent applies a flexible coating layer comprising conductive polymer particles, carbon particles, and binder on the silicon-based active material surface. This shell structure accommodates volume expansion during lithium insertion/extraction cycles while maintaining structural integrity and electrical conductivity, thus improving cycle stability.
Solution Approach 2:
The coating structure provides a porous network that allows buffer space for silicon volume expansion. The conductive polymer particles, carbon particles, and binder form an interconnected porous structure that maintains electrical pathways even during significant volume changes, preserving cycle stability.
3Reliability
If conductive polymer is coated to enhance conductivity, then electrical conductivity improves, but the polymer has low strength and fails to improve expansion effectively
Solution Approach 1:
The patent creates a composite coating system where conductive polymer particles are combined with carbon particles and binder. The carbon particles provide structural strength and additional conductivity pathways, while the binder ensures strong adhesion to the silicon surface, overcoming the limitations of pure polymer coatings.
Solution Approach 2:
The coating layer serves multiple functions simultaneously: the conductive polymer particles provide conductivity, the carbon particles provide structural strength and additional conductivity, and the binder provides adhesion and structural support. This multi-functional coating addresses both conductivity enhancement and mechanical strength requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The combined effect of flake graphite, flexible polymer, and nano-carbon materials results in a silicon-based anode with improved cyclic expansion performance and prolonged service life for lithium ion batteries, while the preparation method is environmentally friendly and suitable for industrial-scale production.
Implementation Method 1
the flexible polymer having high strength is coated on the surface of the silicon-based active material and of the flake graphite, and the region that is not attached and coated is filled by nano-carbon based material. The combination of the three materials mentioned-above together constitutes the composite layer, and the synergistic effect of the three materials is capable of inhibiting the expansion of silicon-based material more effectively.
Implementation Method 2
the flake graphite is integrally attached to the surface of the silicon-based active material, the flexible polymer having high strength is coated on the surface of the silicon-based active material and of the flake graphite, and the region that is not attached and coated is filled by nano-carbon based material. the silicon-based anode material obtained by coating as mentioned above has high electric conductivity and high conductivity stability.
Implementation Method 3
the combination of the three materials mentioned-above together constitutes the composite layer, and the synergistic effect of the three materials is capable of inhibiting the expansion of silicon-based material more effectively. Accordingly, the silicon-based anode material provided by the present application is particularly suitable for lithium ion batteries, and possesses excellent cyclic expansion performance.
Data Source
Figure 1
AI summary
A silicon-based negative electrode material, a preparation method therefor and a use thereof in a lithium-ion battery. The silicon-based negative electrode material comprises a silicon-based active material and a composite layer that coats the surface of the silicon-based active material and composes a flexible polymer, flake graphite and a conductive material. The method comprises: 1) dissolving the flexible polymer in a solvent; 2) adding the flake graphite and the conductive material into the flexible polymer solution obtained in step 1) while stirring; 3) adding an anti-solvent to the mixed coating solution obtained in step 2) and stirring; 4) adding the silicon-based active material to the supersaturated mixed coating solution obtained in step 3) while stirring, and then stirring and separating; and 5) carrying out thermal treatment to obtain the silicon-based negative electrode material.