Carbon-Coated Silicon Oxide Anode with Li2SiO3 for Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon as a negative electrode material face challenges in maintaining initial charge-discharge characteristics and cycle stability due to lithium insertion leading to low bonding-energy states and subsequent structure breakdown during repeated charge and discharge processes.
Innovation Solution
A negative electrode comprising silicon oxide particles coated with a carbon layer, containing Li2SiO3, where the O1s bonding energy peaks at 529.5 eV and 532.5 eV have a specific intensity ratio, and a crystallite size of 5.0 nm or less, inhibiting the formation of silicon and improving battery characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a main raw material of the negative electrode active material to increase battery capacity, then the theoretical capacity increases ten times or more compared to graphite, but the negative electrode active material expands and contracts during charge and discharge, easily leading to cracking near the surface layer
Solution Approach 1:
The patent uses a composite structure consisting of silicon oxide particles (providing capacity) coated with a carbon layer (providing structural stability and conductivity). This composite approach allows the negative electrode to achieve high capacity from silicon oxide while the carbon coating prevents cracking and maintains structural integrity during charge-discharge cycles.
Solution Approach 2:
The patent changes the chemical composition parameter by using silicon oxide (SiOx) instead of pure silicon, and controls the oxygen content to achieve a balance between capacity and stability. The carbon coating further modifies the surface properties, creating a stable interface that prevents electrolyte decomposition while maintaining electrochemical activity.
2Quantity of substance
If the negative electrode active material expands and contracts during charge and discharge, then the reaction area increases due to cracking, but a decomposition reaction of the electrolyte liquid occurs on the new surface, consuming electrolyte liquid and deteriorating cycle characteristics
Solution Approach 1:
The carbon coating acts as an intermediary layer between the silicon oxide particles and the electrolyte liquid. It prevents direct contact between the electrolyte and the silicon oxide surface, thereby preventing decomposition reactions while still allowing lithium ion transport. This intermediary layer maintains cycle characteristics by preventing electrolyte consumption.
Solution Approach 2:
The patent converts the harmful effect of surface cracking into a benefit by coating the cracked surface with carbon. The carbon coating seals the cracked surfaces, preventing electrolyte decomposition while maintaining the increased surface area for enhanced reaction activity. The harmful cracking is thus transformed into an opportunity for creating a stable, high-area interface.
3Productivity
If lithium is inserted into the silicon oxide particles, then the first charge-discharge efficiency improves, but the structure breaks down in repeated charge and discharge processes due to lithium being stabilized in a low bonding-energy state
Solution Approach 1:
The patent creates a composite structure where lithium-inserted silicon oxide particles are coated with carbon. The carbon coating stabilizes the lithium-containing structure by preventing direct exposure to the electrolyte and mechanical stress, thereby maintaining structural integrity during repeated charge-discharge cycles while preserving the high first efficiency achieved through lithium insertion.
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 enhances the battery's first efficiency, capacity, and cycle characteristics by stabilizing the structure and preventing decomposition, resulting in high initial charge-discharge performance and prolonged cycle life.
Implementation Method 1
silicon oxide particles coated with a carbon layer
Implementation Method 2
lithium insertion leading to low bonding-energy state
Implementation Method 3
the silicon oxide particles contain Li2SiO3
Implementation Method 4
the negative electrode active material to expand and contract during charge and discharge
Implementation Method 5
in an O1s bonding energy obtained by XPS analysis on a particle inside
Data Source
AI summary
A negative electrode including negative electrode active material particles, wherein the negative electrode is charged and discharged at least once, the negative electrode active material particles contain silicon oxide particles coated with a carbon layer, and the silicon oxide particles contain Li2SiO3, and in an O1s bonding energy obtained by XPS analysis on a particle inside, an intensity of a peak A obtained near 529.5 eV and an intensity of a peak B obtained near 532.5 eV have a relationship of (intensity of peak A)≤(intensity of peak B). Thus, a negative electrode can increase a battery capacity with improvement of initial efficiency and can achieve sufficient battery cycle characteristics.