Silicon Negative Electrode Material with Glassy Matrix for Battery Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing non-aqueous electrolyte secondary batteries face reduced cycle characteristics due to cracking in the lithium silicate phase caused by stress from silicon particle expansion and contraction during charge/discharge, leading to decreased current collecting efficiency and side reactions.
Innovation Solution
Incorporating a low-melting point inorganic oxide, such as boron oxide, into the voids of the lithium silicate phase to form a denser particle agglomerate, which enhances the strength of the negative electrode and suppresses cracking, thereby improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are dispersed in a lithium silicate phase to achieve high capacity, then the theoretical capacity density is improved, but cracking occurs in the lithium silicate phase due to stress from expansion and contraction during charge/discharge
Solution Approach 1:
The patent changes the physical state of the lithium silicate phase from a rigid solid matrix to a flexible glassy phase by controlling the composition and thermal processing. This parameter change allows the matrix to accommodate volume changes of silicon particles during charge/discharge without cracking, while still maintaining high capacity density through silicon dispersion.
Solution Approach 2:
The patent creates a composite material system consisting of silicon particles dispersed in a lithium silicate glassy phase. This composite structure combines the high capacity advantage of silicon with the flexibility and stress-absorption capability of the glassy matrix, resolving the contradiction between capacity and structural strength.
2Quantity of substance
If silicon particles expand and contract during charge/discharge, then high capacity is achieved, but stress causes cracking in the lithium silicate phase leading to reduced cycle characteristics
Solution Approach 1:
The patent transforms the lithium silicate phase into a glassy state through compositional adjustment and thermal processing. This parameter change enables the matrix to flexibly accommodate silicon particle volume changes during cycling, preventing crack formation and maintaining both high capacity and excellent cycle characteristics.
Solution Approach 2:
The lithium silicate glassy phase acts as an intermediary matrix that mediates between the silicon particles and the external environment. It absorbs and distributes the stress generated by silicon expansion and contraction, preventing stress concentration and crack propagation, thereby maintaining reliability over many cycles.
3Productivity
If the lithium silicate phase is used as a matrix for silicon particles, then current collecting efficiency is improved, but side reactions increase due to cracking
Solution Approach 1:
The patent changes the physical state of the lithium silicate phase to a glassy matrix, which maintains good electrical contact and current collection efficiency while simultaneously providing flexibility to accommodate silicon volume changes. This eliminates cracking that would otherwise lead to increased side reactions.
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 use of low-melting point inorganic oxide fills voids in the lithium silicate phase, increasing the strength of the particle agglomerate and reducing the occurrence of cracking, thus enhancing the battery's cycle characteristics and maintaining capacity retention over charge/discharge cycles.
Implementation Method 1
a low-melting point inorganic oxide that has a lower melting point than lithium silicate forming the lithium silicate particles
Implementation Method 2
heated to a temperature greater than or equal to a temperature at which the raw materials change into a liquid phase, quenched to a temperature lower than a temperature at which spinodal decomposition occurs
Data Source
AI summary
A negative electrode material for a non-aqueous electrolyte secondary battery includes: a lithium silicate phase including lithium silicate particles; silicon particles dispersed in the lithium silicate phase; and a low-melting point inorganic oxide that has a lower melting point than lithium silicate forming the lithium silicate particles, and that is solid at room temperature. The lithium silicate particles and the silicon particles form a particle agglomerate, and the low-melting point inorganic oxide is filled in at least a portion of voids included in the particle agglomerate.