Silicon Core Carbon Coated Negative Active Material for Lithium Batteries
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Solution Overview
Problem
Current negative active materials for rechargeable lithium batteries, such as graphite, have limitations in energy density and capacity due to low density and agglomeration issues, leading to rapid capacity fading and poor life-cycle characteristics.
Innovation Solution
A method involving the preparation of a negative active material with a silicon core and a carbon coating layer, achieved through mixing a silicon precursor with an ammonium halide salt surfactant, initiator, and solvent, followed by heat-treatment, washing, and calcination, resulting in uniformly sized particles without agglomeration and improved dispersity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite is used as negative active material, then long life and reversibility are achieved, but energy density and capacity are limited due to low density
Solution Approach 1:
The invention changes the material parameter from graphite to silicon-based negative active material, which has higher density and capacity. The silicon core provides significantly higher energy density while the carbon coating and surface treatment maintain stability and reversibility, thus improving energy density without completely sacrificing life-cycle characteristics.
2Quantity of substance
If silicon-based negative active material is used to increase capacity, then energy density is improved, but particle agglomeration occurs leading to rapid capacity fading
Solution Approach 1:
The invention creates a composite material structure with silicon core and carbon coating layer. The silicon core provides high capacity and energy density, while the carbon coating layer prevents particle agglomeration and maintains structural stability during charge-discharge cycles. This composite structure resolves the contradiction by combining the high capacity of silicon with the stability of carbon.
Solution Approach 2:
The carbon coating layer acts as an intermediary between the silicon core and the electrolyte. It prevents direct contact between silicon particles and electrolyte that would cause agglomeration, while still allowing lithium ion transport. This intermediary layer maintains the high capacity benefits of silicon while preventing the harmful agglomeration effect.
3Ease of manufacture
If conventional mixing methods are used, then preparation is simple, but uniform particle size and dispersion are not achieved
Solution Approach 1:
The invention replaces conventional mechanical mixing methods with a chemical reaction-based synthesis approach. By controlling the chemical reaction conditions (solvent, catalyst, temperature, time), uniform silicon particles are formed in-situ with controlled size and distribution. This substitution of mechanical mixing with chemical synthesis achieves better particle uniformity while maintaining reasonable manufacturing simplicity.
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 method produces a negative active material with enhanced coulombic efficiency and life-cycle characteristics, maintaining high capacity and preventing agglomeration, which significantly improves the performance of rechargeable lithium batteries.
Implementation Method 1
the mixture may comprise 50 to 70 weight % of the silicon precursor, 5 to 20 weight % of the surfactant, 10 to 45 weight % of the initiator, and the remaining weight % of the solvent
Implementation Method 2
heat-treating the mixture
Implementation Method 3
calcining the washed product
Data Source
AI summary
The present invention provides a method of preparing a negative active material for a rechargeable lithium battery, comprising the steps of: mixing a silicon precursor, a surfactant comprising an ammonium halide salt having a organic group, an initiator, and a solvent; heat-treating the mixture; cooling the heat-treated mixture to room temperature; washing the cooled, heat treated mixture; and calcining the washed product.