Buffered Silicon Core Anode Capsules for Cycle Life Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion cells face limitations in energy density, power density, and cycle life due to mechanical stress and structural degradation of silicon anode materials during lithium insertion and extraction, leading to reduced capacity and cycle life.
Innovation Solution
A composite anode material is developed with silicon core particles encapsulated in graphene or reduced graphene oxide capsules, featuring a buffer layer to mitigate mechanical stress and enhance cycle life, comprising a core-shell structure with a lithium silicate buffer layer to support the silicon core, allowing for controlled expansion and maintaining capacity over multiple charge-discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is incorporated within a carbon based anode to increase capacity, then the anode capacity significantly increases, but the silicon undergoes significant volume expansion causing mechanical stress, fracture, and structural degradation
Solution Approach 1:
The patent employs a nested structure where silicon particles are enclosed within a porous carbon matrix, which is further protected by an outer shell. This multi-layer nesting allows the silicon to expand and contract during lithium insertion/extraction while maintaining structural integrity and preventing direct contact between silicon particles that would cause mechanical failure.
Solution Approach 2:
The patent utilizes a flexible porous carbon matrix and an outer shell structure that can accommodate the volume expansion of silicon during lithiation. The carbon-based materials provide mechanical flexibility and structural support, allowing the silicon particles to undergo up to 400% volume change without fracturing or losing electrical connectivity.
2Quantity of substance
If silicon undergoes volume expansion during lithium insertion, then anode capacity increases, but mechanical stress causes fracture and electrical disconnection of silicon particles
Solution Approach 1:
The patent introduces a porous carbon matrix as an intermediary material between silicon particles. This carbon matrix serves as a mechanical buffer that absorbs expansion stress and as an electrical conductor that maintains connectivity. The carbon-based intermediary prevents direct mechanical contact between silicon particles, reducing fracture and electrical disconnection during volume expansion cycles.
Solution Approach 2:
The patent creates a composite anode material combining silicon particles with porous carbon matrix and an outer shell. This composite structure leverages the high capacity of silicon while utilizing the mechanical stability and electrical conductivity of carbon materials to maintain structural integrity and electrical connectivity during repeated expansion and contraction cycles.
3Quantity of substance
If silicon particles are used to increase energy density, then cell capacity increases, but structural degradation leads to reduced cycle life
Solution Approach 1:
The patent implements a pre-designed porous carbon matrix structure that anticipates and accommodates the volume expansion of silicon particles during lithium insertion. The carbon matrix is engineered with sufficient porosity and mechanical strength to cushion the expansion stress before it can cause fracture to the silicon particles, thereby preventing structural degradation and maintaining cycle life.
Solution Approach 2:
The patent develops a composite anode structure combining silicon particles with porous carbon matrix and an outer shell. This composite design synergistically combines the high capacity advantage of silicon with the structural stability and cycle life benefits of carbon-based materials, enabling the anode to withstand repeated charge-discharge cycles while maintaining high energy density.
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 composite anode material significantly increases cycle life and capacity retention by minimizing mechanical degradation and electrical disconnection of silicon particles, as demonstrated by improved capacity retention in lithium ion test cells compared to control cells without the buffer layer.
Implementation Method 1
Each particle may include a core and a buffer layer surrounding the core, with the buffer layer and the core comprising different materials
Implementation Method 2
capsules comprising graphene, reduced graphene oxide, graphene oxide, or a combination thereof, and active material particles disposed inside of the capsules
Data Source
AI summary
Composite anode materials and methods of making same, the anode materials including capsules including graphene, reduced graphene oxide, graphene oxide, or a combination thereof, and particles of an active material disposed inside of the capsules. The particles may each include a core and a buffer layer surrounding the core. The core may include crystalline silicon, and the buffer layer may include a silicon oxide, a lithium silicate, carbon, or a combination thereof.