Silicon-Dispersed Lithium Silicate Negative Electrode Material
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Solution Overview
Problem
Silicon-containing materials used in negative electrodes of non-aqueous electrolyte secondary batteries face issues with irreversible capacity and alkali component leaching, leading to low initial charge/discharge efficiency and structural degradation due to volume changes during charge and discharge.
Innovation Solution
A negative electrode material comprising a lithium silicate phase with silicon particles dispersed within, where the silicon particles have a crystallite size of 10 nm or more and a composition of Li2Si2O5.(x−2)SiO2, where 2<x≤18, to reduce irreversible capacity and alkali component leaching, while maintaining structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the crystallite size of silicon particles is decreased to increase surface area, then the irreversible capacity increases, but the initial charge/discharge efficiency deteriorates
Solution Approach 1:
The patent specifies a crystallite size of 10 nm or more for silicon particles, which is a specific parameter change that balances surface area (for capacity) with irreversible capacity loss. This parameter optimization resolves the contradiction by finding the optimal size range that maintains sufficient surface area while minimizing irreversible reactions.
Solution Approach 2:
The patent uses a composite structure where silicon particles are dispersed in a lithium silicate phase. This composite material approach allows the silicon to provide high capacity while the lithium silicate matrix suppresses irreversible capacity loss and alkali leaching, thereby maintaining high initial charge/discharge efficiency even with adequate surface area.
2Reliability
If the crystallite size of silicon particles is increased to 10 nm or more to reduce irreversible capacity, then the initial charge/discharge efficiency improves, but volume change during charge/discharge causes cracking and structural degradation
Solution Approach 1:
The lithium silicate phase acts as an intermediary matrix that surrounds and supports the silicon particles. This intermediary structure accommodates volume changes during charge/discharge cycles, preventing direct cracking of silicon particles while maintaining structural integrity. The lithium silicate absorbs mechanical stress and prevents alkali component leaching.
Solution Approach 2:
The composite structure of silicon particles dispersed in lithium silicate phase provides mechanical support and stress distribution. The lithium silicate matrix with composition Li2Si2O5.(x-2)SiO2 (where 2<x≤18) forms a robust framework that prevents cracking of silicon particles during volume expansion and contraction, thereby maintaining structural stability.
3Reliability
If lithium silicates such as Li4SiO4 or Li2SiO3 are used to introduce lithium in advance, then the initial charge/discharge efficiency improves, but alkali component leaching occurs during production and storage
Solution Approach 1:
The patent specifies a particular composition range for lithium silicate (Li2Si2O5.(x-2)SiO2 where 2<x≤18) that changes the chemical parameters to reduce alkali component leaching. This composition optimization maintains the ability to introduce lithium in advance while significantly reducing the harmful leaching effect during production and storage.
Solution Approach 2:
The patent converts the potentially harmful alkali component leaching into a beneficial structure by using lithium silicate with controlled composition. The lithium silicate matrix provides structural stability and reduces water reactivity, transforming what would be a harmful leaching issue into a stable, low-reactivity framework that still provides the needed lithium reservoir function.
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 achieves excellent cycle characteristics and high capacity retention by minimizing irreversible reactions and alkali component leaching, even with larger silicon particles, thereby enhancing the battery's overall performance.
Implementation Method 1
a silicon-containing material that can be alloyed with lithium is expected to be used as a negative electrode active material that has a high theoretical capacity density
Implementation Method 2
when the silicon particles have a crystallite size of 10 nm or more, a volume change that causes cracking in the silicon particles and the lithium silicate occurs during charge and discharge
Data Source
AI summary
Disclosed is a negative electrode material including: a lithium silicate phase that contains a lithium silicate; and silicon particles that are dispersed in the lithium silicate phase, wherein the silicon particles have a crystallite size of 10 nm or more, and the lithium silicate has a composition represented by the following formula: Li2Si2O5.(x−2)SiO2, where 2<x≤18 is satisfied.