Silicon Nanoparticle Anode with Polymeric SEI for Cycle Stability
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Solution Overview
Problem
Lithium ion batteries face limitations in energy and power density due to the low theoretical storage capacity of graphite and the degradation of silicon-based anode materials caused by volume changes during lithium alloying and de-alloying, leading to performance degradation.
Innovation Solution
A lithium ion anode material comprising metal or metal alloy nanoparticulates with a solid electrolyte interface (SEI) is developed, where each nanoparticle is individually coated with a polymeric SEI, enhancing ionic conductivity and preventing silicon or germanium oxidation, combined with conductive carbon and optionally graphite and a binder, to form a film on an electrical substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode materials are used to achieve high theoretical specific capacity, then energy density is improved, but volume change during lithium alloying and de-alloying causes pulverization and performance degradation
Solution Approach 1:
The patent embeds silicon nanoparticulates within a porous carbon matrix structure, creating a nested configuration where the silicon particles are contained within the carbon framework. This nesting approach allows the silicon to undergo volume expansion during lithiation while the surrounding carbon matrix provides structural confinement, preventing pulverization and maintaining electrode integrity over multiple cycles.
Solution Approach 2:
The patent employs a porous carbon matrix that acts as a flexible protective shell surrounding the silicon nanoparticulates. This carbon shell accommodates the volume changes of silicon during lithium alloying and de-alloying, preventing direct contact between silicon particles and the electrolyte, thereby avoiding pulverization and maintaining electrical contact throughout cycling.
2Quantity of substance
If silicon nanoparticulates are used to achieve high specific capacity, then energy density is improved, but electrical contact is lost due to pulverization
Solution Approach 1:
The patent creates a composite material system consisting of silicon nanoparticulates embedded in a porous carbon matrix. The carbon component provides electrical conductivity and structural stability, while the silicon provides high capacity. This composite structure ensures continuous electrical contact is maintained even as the silicon undergoes volume changes during cycling.
Solution Approach 2:
The porous carbon matrix serves as an intermediary between the silicon nanoparticulates and the current collector. It mediates the mechanical stress and volume changes, maintaining electrical connectivity while allowing the silicon to undergo its natural expansion and contraction during lithiation and delithiation processes.
3Reliability
If graphite is used as anode material to achieve good cycle stability, then reliability is improved, but energy density is limited due to low theoretical storage capacity
Solution Approach 1:
The patent applies local quality by using different materials in different regions of the anode structure. The porous carbon matrix provides structural stability and good cycle life characteristics, while the embedded silicon nanoparticulates provide high local capacity. This spatial differentiation of material functions allows the anode to achieve both stability and high capacity.
Solution Approach 2:
The patent creates a composite anode material combining graphite's structural stability with silicon's high capacity. The porous carbon matrix (which may include graphite components) provides a stable framework that maintains cycle life, while the silicon nanoparticulates dispersed within provide the high theoretical capacity, achieving a synergistic effect that overcomes the limitations of pure graphite.
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 significantly improves the cycle stability and retention of high specific capacities in lithium ion batteries, maintaining performance over multiple cycles by preventing pulverization and maintaining electrical contact.
Implementation Method 1
each nanoparticle is individually coated with a polymeric SEI, enhancing ionic conductivity and preventing silicon or germanium oxidation
Implementation Method 2
each nanoparticle is individually coated with a polymeric SEI, enhancing ionic conductivity
Data Source
AI summary
Herein are described materials for a lithium ion anode, processes of manufacturing the lithium ion anode, and batteries that include the lithium ion anode. The materials can include a metal or metal alloy nanoparticulate carrying a solid electrolyte interface. The process can include admixing a lithium accepting material that is a metal or metal alloy nanoparticulate carrying a solid electrolyte interface with a conductive carbon; and then preparing a film of the admixture on an electrical substrate. The battery is assembled from the as manufactured lithium ion anode.