Silicon-Based Composite for Lithium Battery Anodes
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Solution Overview
Problem
The use of silicon-based materials as anode active materials in lithium secondary batteries leads to volume expansion and reduced battery capacity due to non-reversible phase formation during initial charge and discharge, resulting in decreased initial efficiency.
Innovation Solution
A silicon-based composite is created by coating silicon oxide with carbon and bonding it with lithium through heat treatment, forming a stable Li silicate compound that acts as a diffusion barrier, enhancing electrical conductivity and reducing volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as anode active material, then theoretical capacity is increased, but volume expansion occurs during lithium ion intercalation
Solution Approach 1:
The patent embeds silicon particles within a porous carbon matrix structure, creating a nested configuration where silicon is contained inside the carbon framework. This nesting approach allows silicon to expand during lithium intercalation while being constrained by the surrounding carbon structure, preventing excessive volume expansion that would otherwise degrade battery performance.
Solution Approach 2:
The patent creates a composite material consisting of silicon particles combined with carbon matrix and lithium oxide. This composite structure combines the high capacity advantage of silicon with the structural stability and conductivity of carbon, while lithium oxide forms protective layers that further constrain silicon expansion. The composite approach allows simultaneous achievement of high capacity and volume stability.
2Quantity of substance
If silicon-based material is used as anode active material, then theoretical capacity is increased, but charge and discharge cycle life is reduced
Solution Approach 1:
The patent incorporates lithium oxide into the composite structure beforehand, which reacts with silicon during initial cycles to form a protective lithium silicate layer. This pre-inclusion of lithium oxide provides beforehand cushioning that prevents direct contact between silicon and electrolyte, reducing side reactions and structural degradation that would otherwise limit cycle life. The protective layer is formed in advance to cushion against subsequent mechanical and chemical stresses.
Solution Approach 2:
The composite material structure provides mechanical support and structural integrity throughout charge-discharge cycles. The carbon matrix maintains a stable framework that accommodates silicon volume changes, while the integrated lithium oxide contributes to forming stable protective interfaces. This composite approach ensures long-term structural stability necessary for extended cycle life while maintaining high capacity.
3Productivity
If silicon oxide is bonded with lithium through heat treatment, then initial efficiency is increased, but manufacturing process complexity is increased
Solution Approach 1:
The patent combines multiple functions into a single heat treatment step: carbon coating of silicon oxide, lithium oxide incorporation, and lithium-silicon reaction all occur during one controlled heating process. By merging these operations, the patent achieves the beneficial lithium silicate formation and carbon coating effects without requiring separate sequential steps, thereby reducing overall process complexity while maintaining high initial efficiency.
Solution Approach 2:
The patent utilizes controlled parameter changes during heat treatment (temperature, atmosphere composition, holding time) to achieve multiple objectives simultaneously. By carefully adjusting these parameters, the process transforms silicon oxide and lithium oxide into the desired lithium silicate compound while also ensuring proper carbon coating formation. This parameter control approach simplifies the process by using a single controlled transformation rather than multiple discrete steps.
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
This approach increases the initial efficiency of lithium secondary batteries by controlling the reaction between silicon oxide and lithium, leading to improved charge and discharge performance and extended cycle life.
Implementation Method 1
when lithium ions are intercalated, since the silicon expands three times or more in volume
Implementation Method 2
bonding lithium to the silicon oxide through a heat treatment to form a compound
Implementation Method 3
a reaction between silicon oxide and lithium can be controlled by coating a surface of the silicon oxide with carbon and bonding lithium to the silicon oxide through a heat treatment
Data Source
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AI summary
The present invention relates to a silicon-based composite including a silicon oxide which is coated thereon with carbon and bonded therein to lithium. The present invention also relates to a method of producing a silicon-based composite, comprising coating a surface of silicon oxide with carbon, mixing the silicon oxide coated with carbon with lithium oxide, and heat-treating a mixture of the silicon oxide coated with carbon and the lithium oxide in an inert atmosphere.