Carbon-Coated Silicon-Carbon Anode Particles With Controlled Size Distribution
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Solution Overview
Problem
Lithium secondary batteries face challenges with mechanical and chemical damage during repeated charging and discharging, leading to poor contact between active material particles, short-circuits, and reduced stability and capacity due to the reactivity of silicon-based anode materials with electrolytes.
Innovation Solution
An anode active material comprising a composite of silicon-based and carbon-based materials with a carbon coating, which controls particle size distribution, suppresses side reactions, and enhances structural stability, while the carbon coating prevents electrolyte contact and volume expansion, improving the battery's energy density and charge/discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase energy density, then capacity is improved, but structural stability deteriorates due to volume expansion and reactivity with electrolyte
Solution Approach 1:
Silicon-based active material particles are embedded within carbon-based active material particles, creating a core-shell structure where the silicon core provides high energy density while the carbon shell maintains structural stability and prevents electrolyte contact
Solution Approach 2:
The anode active material uses a composite structure combining silicon-based and carbon-based materials, where silicon provides high capacity and carbon provides structural stability and chemical inertness, achieving both high energy density and structural stability
2Quantity of substance
If silicon-based active material is used to increase capacity, then energy density is improved, but reliability deteriorates due to mechanical damage and short-circuits
Solution Approach 1:
Silicon particles are nested within carbon particles, where the carbon matrix prevents mechanical damage to silicon during volume changes and prevents direct contact between silicon and electrolyte, thereby preventing short-circuits and improving reliability
Solution Approach 2:
The carbon-based active material surrounding the silicon particles acts as a cushioning matrix that accommodates volume expansion of silicon during lithiation, preventing mechanical damage and maintaining structural integrity over repeated cycles
3Power
If particle size is reduced to improve power properties, then charge/discharge rate is improved, but harmful factors increase due to greater surface area reacting with electrolyte
Solution Approach 1:
The composite structure of carbon-based active material containing silicon-based active material allows small particle sizes for high power properties while the carbon matrix protects the reactive silicon surface from electrolyte contact, reducing harmful side reactions
Solution Approach 2:
The carbon-based active material acts as an intermediary layer between silicon and electrolyte, enabling small particle sizes for fast charge/discharge while preventing direct harmful interactions between silicon and electrolyte
Data Source
AI summary
An anode active material and a secondary battery including the anode active material are disclosed. In an implementation, an anode active material for a secondary battery includes a plurality of composite active material particles, each composite active material particle containing a first active material that includes silicon and a second active material that includes carbon, and a carbon coating covering at least a portion of a surface of at least one of the plurality of composite active material particles. The anode active material has a volume-based particle size distribution represented as a ratio D10/D50 ranging from 0.40 to 0.75 and a ratio Dmin/D50 ranging from 0.3 to 1, wherein D10 indicates a particle diameter corresponding to a volume fraction of 10%, D50 indicates a particle diameter corresponding to a volume fraction of 50%, and Dmin indicates a minimum particle diameter.