Nano-Si-RTIL Battery Anode SEI Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based anodes in lithium-ion batteries face structural degradation and instability due to volume expansion during lithiation, leading to short battery life and inefficient cycling performance, as the continuous breaking and reforming of the solid-electrolyte interphase (SEI) layer consumes lithium and depletes electrolyte, especially in full-cells with limited lithium supply.
Innovation Solution
A nano-Si-RTIL system with a cyclized-polyacrylonitrile (cPAN)-based composite architecture that forms a highly stable and resilient SEI, using room temperature ionic liquids like PYR13FSI, which stabilizes the SEI and reduces lithium consumption, enabling long-term operation of lithium-ion full-cells with bulk type nano-Si-based anodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon anodes are used to achieve high energy density, then battery capacity is improved, but structural stability deteriorates due to 300% volume expansion during lithiation
Solution Approach 1:
The silicon anode is divided into nanoscale particles (nanosilicon) to segment the overall volume expansion into many small, distributed units. This segmentation prevents catastrophic structural failure by allowing localized expansion without compromising the entire electrode structure, thus maintaining both high capacity and structural stability.
Solution Approach 2:
A thin film solid-electrolyte interphase (SEI) layer is formed on the nanosilicon surface through electrolyte decomposition. This flexible thin film accommodates the volume expansion of nanosilicon during lithiation while maintaining structural integrity, preventing electrode disintegration and enabling long-term cycling stability.
2Productivity
If conventional organic electrolytes are used with silicon anodes, then initial cycling is possible, but coulombic efficiency deteriorates due to continuous SEI reformation consuming lithium
Solution Approach 1:
The SEI layer is formed preliminarily during initial cycling cycles, creating a stable protective interface before productive cycling begins. This preliminary SEI formation prevents continuous electrolyte decomposition during subsequent cycles, eliminating ongoing lithium consumption and enabling high coulombic efficiency (>99.9%) in full-cells.
Solution Approach 2:
The patent employs room temperature ionic liquids (RTILs) with specific chemical compositions (e.g., LiFSI, LiTFSI salts in ionic liquid matrices) to change the electrolyte parameters. These compositional changes enable formation of more stable SEI layers compared to conventional organic electrolytes, reducing continuous decomposition and improving coulombic efficiency.
3Quantity of substance
If bulk type nano-Si-based anodes are used to increase energy density, then battery performance is improved, but mechanical stability deteriorates due to volume expansion
Solution Approach 1:
The bulk anode is composed of numerous nanosilicon particles distributed throughout the electrode matrix. This segmentation allows each particle to undergo volume expansion independently without transmitting excessive mechanical stress to neighboring particles or the electrode structure, maintaining mechanical stability while achieving high energy density.
Solution Approach 2:
The anode is constructed as a composite material system combining nanosilicon particles with conductive additives, binders, and a stable SEI film. This composite structure provides mechanical support and structural integrity to the nanosilicon particles during volume expansion, preventing electrode disintegration while maintaining high capacity.
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 nano-Si-RTIL system achieves high cycling stability and energy density with average coulombic efficiency above 99.9% over 200 cycles, significantly outperforming conventional organic electrolyte systems, and demonstrates structural robustness and volume control, allowing for the integration of more electro-active material in commercial batteries.
Implementation Method 1
The solid-electrolyte interphase layer forms on the anode surface through reductive decomposition of the electrolyte during charging of the battery
Implementation Method 2
While the commercialized graphite electrode expands roughly 10-13% during lithium intercalation
Implementation Method 3
silicon's expansion amounts to nearly 300%, generating structural degradation and instability of the solid-electrolyte interphase
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 2E~2H
AI summary
The disclosure includes a composition of matter including a film formed on substantially all nSi-cPAN particles included in an electrode, the film including fluorine, oxygen, sulfur, carbon and lithium.