All-solid-state lithium ion battery anode particle sizing
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Solution Overview
Problem
All-solid-state lithium ion secondary batteries using alloy-based anode active materials exhibit low capacity retention rates due to aggregation of anode active material particles, which disrupts the electron conducting path and leads to deterioration in battery performance during charge-discharge cycles.
Innovation Solution
The use of anode active material particles comprising elemental silicon or SiO, with a specific parameter value A (calculated by BET specific surface area, median diameter, and density) within a defined range, ensures stable contact with electroconductive materials, maintaining ion and electron conductivity paths and enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy-based anode active material particles are used to achieve high theoretical capacity, then the battery capacity per volume is improved, but the anode active material particles aggregate during charge-discharge cycles, disrupting the electron conducting path and reducing capacity retention rate
Solution Approach 1:
A solid electrolyte is introduced as an intermediary substance between the anode active material particles and the external environment. This solid electrolyte layer prevents particle aggregation while maintaining ionic conductivity, thereby preserving both high capacity and good cycle stability. The solid electrolyte acts as a buffer that accommodates volume changes without allowing direct particle-to-particle contact that would disrupt electron pathways.
Solution Approach 2:
The patent changes the physical state of the electrolyte from liquid to solid, which fundamentally alters the interaction between electrolyte and anode particles. This parameter change (phase transition) prevents particle aggregation while maintaining necessary ionic transport, thus resolving the contradiction between high capacity utilization and capacity retention during cycling.
2Stability of the object's composition
If the anode active material particles are made smaller to improve distribution, then the electron conducting path is maintained better, but the specific surface area increases leading to more aggregation points
Solution Approach 1:
The solid electrolyte serves as a separating intermediary between fine anode particles, preventing them from aggregating despite their high specific surface area. This mediator layer maintains particle dispersion while allowing ionic transport, thus enabling the use of fine particles for stable electron conduction without the harmful aggregation effects.
Solution Approach 2:
The solid electrolyte structure provides a porous or interconnected matrix that accommodates fine particles while maintaining structural integrity. This porous structure allows ionic pathways to remain open while physically separating particles to prevent aggregation, thus maintaining both electrical conductivity and particle stability.
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 significantly improves the capacity retention rate of the battery by ensuring even distribution and contact of anode active material particles, leading to better durability and performance over repeated charge-discharge cycles.
Implementation Method 1
An active material (an alloy-based active material) containing a metal such as Si, the metal being able to form an alloy with Li
Implementation Method 2
a solid electrolyte; wherein the anode active material particles comprise at least one active material selected from the group consisting of elemental silicon and SiO
Implementation Method 3
an electroconductive material and a solid electrolyte; a value obtained by dividing, by the value A, a volume percentage (%) of the electroconductive material
Data Source
Figure 1~2
Figure 3
AI summary
Disclosed is an all-solid-state lithium ion secondary battery excellent in cycle characteristics. The battery may be an all-solid-state lithium ion secondary battery, wherein an anode comprises anode active material particles, an electroconductive material and a solid electrolyte; wherein the anode active material particles comprise at least one active material selected from the group consisting of elemental silicon and SiO; and wherein, for the anode active material particles, a value A obtained by the following formula (1) is 6.1 or more and 54.8 or less: A=SBET×dmed×D where SBET is a BET specific surface area (m2/g) of the anode active material particles; dmed is a median diameter D50 (µm) of the anode active material particles; and D is a density (g/cm3) of the anode active material particles.