Silicon-Carbon Solid Sol for Lithium Battery Anodes
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Solution Overview
Problem
Current nano-silicon-based anode materials for lithium batteries face challenges due to large particle sizes and oxidation issues, leading to poor cycle stability and capacity, as existing preparation methods struggle to produce highly dispersed silicon-carbon composites with ultra-fine nano-silicon particles.
Innovation Solution
A method involving the preparation of a highly dispersed silicon-carbon solid sol, where silicon is coated with a continuous carbon layer or buried in a continuous carbon phase, using a process that includes anodic polarization of metal carbide and metal silicide in a molten salt medium, allowing for the production of silicon with particle sizes less than 80 nm and high yield with low energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nano-silicon particle size is reduced to less than 80 nm, then capacity and cycle stability are improved, but oxidation resistance becomes worse
Solution Approach 1:
The patent creates a silicon-carbon composite material where ultra-fine silicon particles (less than 80 nm) are embedded in a carbon matrix. This composite structure allows the silicon to maintain its high capacity benefits while the carbon phase provides oxidation protection, resolving the contradiction between small particle size and oxidation resistance.
Solution Approach 2:
The patent uses a carbon-rich molten salt environment during synthesis that creates a reducing/atmosphere protective of the silicon particles. The carbon phase acts as a barrier preventing oxygen exposure, effectively creating an inert environment that protects the ultra-fine silicon from oxidation while maintaining its small particle size.
2Manufacturing precision
If conventional preparation methods are used, then production cost is reduced, but manufacturing precision of ultra-fine dispersed particles becomes worse
Solution Approach 1:
The patent changes the synthesis parameters by using a carbon-rich molten salt system at controlled temperatures (400-800°C). This parameter change enables the formation of ultra-fine silicon particles with precise size control (less than 80 nm) while maintaining a relatively simple and cost-effective manufacturing process compared to conventional high-precision methods.
Solution Approach 2:
The patent introduces a carbon-rich molten salt as an intermediary medium during synthesis. This intermediary facilitates the formation of ultra-fine silicon particles with controlled size and distribution, acting as a template or mediator that enables precise manufacturing without requiring complex equipment or expensive procedures.
3Reliability
If silicon particles are dispersed in porous carbon structure, then cycle stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the silicon formation and carbon structure creation into a single simultaneous synthesis process using the carbon-rich molten salt method. Instead of separately preparing silicon particles and then dispersing them in carbon structures, the method combines both steps, reducing manufacturing complexity while achieving the desired dispersed silicon-carbon composite with improved cycle stability.
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 resulting silicon-carbon solid sol exhibits high capacity and cycle stability as an anode material, preventing oxidation of nano-silicon and reducing production costs compared to existing methods, while avoiding the need for expensive precursors and complex equipment.
Implementation Method 1
performing an anodic polarization to the solid-state composite electrode of metal carbide M1C and metal silicide M2Si under a condition of 300-750° C. to dissolve metals M1 and M2 in the metal carbide M1C and metal silicide M2Si
Implementation Method 2
a molten salt containing alkali halide or alkaline earth halide or a mixture of the alkali halide and the alkaline earth halide is used as an electrolyte
Implementation Method 3
performing a cathodic polarization to the solid-state composite electrode at 300-950° C. to make silicon and carbon react with dissolved metals M1 and M2
Data Source
AI summary
A highly dispersed silicon-carbon solid sol, a preparation method and application thereof. In the high-dispersion silicon-carbon solid sol, the silicon is a dispersed substance, the carbon is a dispersion medium. The silicon is covered by a continuous carbon layer or buried in a continuous carbon phase; a size of the silicon is less than 80 nm at least in one of dimensions, and a mass percentage of the silicon in the highly dispersed silicon-carbon solid sol is 5% to 90%. The nano-silicon particles are covered by the continuous carbon phase, which is not only conducive to obtaining nano-silicon particles with very small sizes, but also can effectively prevent the late oxidation of nano-silicon.