Silicon Electrode Crack Network for Volume Expansion
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Solution Overview
Problem
Lithium ion secondary batteries face capacity reduction due to volume expansion of silicon-containing active materials, leading to electrode deterioration and irreversible capacity loss, which limits their energy density and cycle efficiency.
Innovation Solution
The electrode for a nonaqueous electrolyte battery features an active material layer with silicon particles or silicon oxide particles, incorporating a network of cracks extending in the thickness direction to relieve stress and prevent electrolyte penetration, thereby maintaining energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as active material to increase capacity, then energy density is improved, but volume expansion causes electrode deterioration and capacity reduction
Solution Approach 1:
The active material layer is segmented into multiple regions separated by cracks. This segmentation allows each region to independently accommodate volume expansion of silicon particles during lithiation, preventing stress propagation throughout the entire electrode structure and reducing electrode deterioration.
Solution Approach 2:
Cracks are preliminarily formed in the active material layer before battery operation. These pre-formed cracks provide predetermined pathways for stress relief and prevent electrolyte penetration, addressing the volume expansion issue before it causes damage during cycling.
2Stability of the object's composition
If voids are provided in active material layer to relieve volume expansion stress, then cycle stability is improved, but electrode strength decreases and volume energy density reduces
Solution Approach 1:
Instead of creating three-dimensional voids within the active material layer, the invention uses two-dimensional cracks that extend through the layer thickness. These cracks provide stress relief pathways with minimal impact on the overall structural integrity and volume energy density of the electrode.
3Stability of the object's composition
If grooves are patterned in active material layer to divide electrode regions, then volume expansion stress is relieved, but energy density per unit volume decreases due to non-active material grooves
Solution Approach 1:
The active material layer is designed with a porous crack network structure that provides stress relief pathways. Unlike solid grooves that displace active material, these cracks are minimal-volume features that relieve stress while maintaining high active material content and energy density.
4Reliability
If cracks are formed in active material layer to manage volume expansion, then capacity loss is reduced, but electrode structural integrity may be compromised
Solution Approach 1:
The cracks act as flexible stress relief features that allow the active material layer to accommodate volume changes during cycling. The cracks are designed to be narrow and controlled, providing flexibility for stress management while maintaining sufficient structural integrity for electrode 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 crack network in the active material layer effectively manages volume expansion, reducing capacity loss and enhancing the battery's charge-discharge efficiency and cycle life without compromising energy density.
Implementation Method 1
when a silicon particle absorbs lithium, the volume thereof expands to about 3 to 4 times the original volume
Implementation Method 2
the crack network in the active material layer effectively manages volume expansion, reducing capacity loss and enhancing the battery's charge-discharge efficiency and cycle life
Data Source
AI summary
An electrode for a nonaqueous electrolyte battery of the embodiment includes a current collector; and an active material layer which includes an active material and is formed on the current collector. The active material layer includes at least one of a silicon particle and a silicon oxide particle. The active material layer has a plurality of cracks extending in a thickness direction of the active material layer.