SiOx Composite Negative Electrode for Lithium Battery
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Solution Overview
Problem
Conventional lithium secondary batteries using graphite active materials have low energy density and Si-based materials suffer from large volume expansion, leading to deteriorated battery life, while SiOx materials face challenges due to low initial coulombic efficiency and side reactions with electrolytes.
Innovation Solution
A negative electrode active material comprising a silicon oxide (SiOx) composite with an alkali metal or alkaline earth metal-containing phosphate and aluminum-containing phosphate, along with lithium silicate and amorphous carbon, is developed to improve initial efficiency, capacity, and life characteristics by stabilizing the surface structure and suppressing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based material is used to improve energy density, then capacity is improved, but volume expansion occurs leading to deteriorated battery life
Solution Approach 1:
The patent applies nested doll by forming a core-shell structure where SiOx core is nested within a Li2SiO3 shell, and further nested within an AlPO4 outer layer. This multi-layer nesting structure allows the high-capacity SiOx core to be protected by successive protective shells, preventing volume expansion damage while maintaining capacity.
Solution Approach 2:
The patent uses composite materials by combining SiOx with Li2SiO3 and AlPO4 to create a composite negative electrode active material. This composite structure integrates the high capacity of SiOx with the protective and stabilizing properties of Li2SiO3 and AlPO4, resolving the contradiction between capacity and battery life.
2Reliability
If SiOx material is used to reduce volume expansion, then battery life is improved, but initial coulombic efficiency decreases due to irreversible phase formation
Solution Approach 1:
The patent applies preliminary action by pre-forming a Li2SiO3 shell around the SiOx core before battery operation. This preliminary protective layer prevents direct contact between SiOx and electrolyte, reducing irreversible phase formation and improving initial coulombic efficiency while maintaining the low volume expansion benefits of SiOx.
Solution Approach 2:
The patent uses Li2SiO3 and AlPO4 as intermediary layers between the SiOx core and the electrolyte. These intermediary layers mediate the interaction, preventing direct harmful reactions while allowing beneficial Li ion transport, thus improving initial coulombic efficiency without sacrificing battery life.
3Stability of the object's composition
If metal compound is added to SiOx particles, then surface structure is modified, but residual metal compounds cause side reactions with electrolyte
Solution Approach 1:
The patent applies taking out by removing residual metal compounds from the surface of SiOx particles through acid treatment. This extraction eliminates the harmful metal compounds that would otherwise cause side reactions with electrolyte, while preserving the beneficial surface structure modifications.
Solution Approach 2:
The patent converts the potentially harmful residual metal compounds into beneficial surface modifications by controlled acid treatment. The treatment removes harmful excess metal compounds while maintaining the structural stability benefits, thus converting a harmful factor into a beneficial one.
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 composite effectively removes residual metal compounds, stabilizes the surface structure, and enhances battery capacity and life characteristics, improving initial efficiency and slurry stability, while mitigating volume changes during charge and discharge cycles.
Implementation Method 1
stabilizing the surface structure
Implementation Method 2
effectively removes residual metal compounds
Implementation Method 3
suppressing side reactions with electrolyte produced in raising a slurry pH and in a charge and discharge process
Implementation Method 4
mitigating volume changes during charge and discharge cycles
Data Source
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AI summary
Provided is a negative electrode active material for a lithium secondary battery including: a silicon oxide (SiOx, 0<x≤2) composite including an alkali metal or alkaline earth metal-containing phosphate; and an aluminum-containing phosphate.