Silicon Negative Electrode Material with CVD Carbon Coating
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high energy density and lightweight designs due to limitations in negative electrode materials, particularly with silicon-based alloys that experience volume changes during charging/discharging, leading to capacity deterioration and poor adhesion with carbon materials.
Innovation Solution
A negative electrode material is developed using a silicon material-containing amorphous carbon complex, where the silicon material is surface-treated with a silane coupling agent and then CVD carbon-coated, enhancing adhesion and dispersibility, and reducing volume changes during charging/discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon material is used as negative electrode active material to increase capacity, then charging/discharging capacity is significantly increased, but volume change during intercalation and deintercalation causes pulverization and adhesion defects
Solution Approach 1:
The patent creates a composite material consisting of silicon particles embedded in an amorphous carbon matrix. The silicon provides high capacity (4200 mAh/g theoretical discharge capacity) while the amorphous carbon matrix constrains volume expansion and prevents pulverization. This composite structure maintains adhesion to the current collector and resolves the contradiction between high capacity and cycle stability.
Solution Approach 2:
The amorphous carbon matrix acts as a flexible constraining shell around the silicon particles. This shell accommodates volume changes during lithium intercalation and deintercalation while maintaining structural integrity and adhesion, preventing the silicon from pulverizing and detaching from the current collector.
2Reliability
If transition metal elements such as Ti are used in amorphous material to improve fine structure, then cycle characteristics improve, but density increases and weight increases
Solution Approach 1:
The patent replaces heavy transition metals (Ti, Ni, Cu, Co, Fe) with lighter carbon-based amorphous material. The amorphous carbon structure provides the necessary fine structure and cycle stability without the weight penalty of transition metals, achieving the same reliability improvement with significantly reduced weight.
3Reliability
If silicon material is complexed with carbon material to reduce volume change, then pulverization is reduced, but adhesion with carbon material remains poor
Solution Approach 1:
The patent changes the structural parameters of the carbon material from crystalline graphite to amorphous carbon. This parameter change enables the carbon matrix to better adhere to silicon particles while accommodating volume changes. The amorphous structure provides a more compliant and adhesive matrix compared to crystalline carbon, resolving the adhesion problem.
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 solution results in a lightweight negative electrode with improved high-rate characteristics and energy density, along with enhanced cycle stability and reduced electrical shorts with the current collector.
Implementation Method 1
a silicon material-containing amorphous carbon complex, where the silicon material is surface-treated with a silane coupling agent
Implementation Method 2
CVD carbon coating a silicon material-containing amorphous carbon material
Data Source
AI summary
The present invention relates to a negative electrode material for a lithium secondary battery, a method for producing same, and a lithium secondary battery comprising same as a negative electrode. The present invention provides a negative electrode material for a lithium secondary battery, the material comprising a complex in which a chemical vapor deposition (CVD) carbon coating film is formed on an amorphous carbon material comprising a silicon material that has been surface treated by a silane coupling agent.