Functionalized Graphene Coating for Stable Silicon Battery Anodes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based negative electrode materials for lithium secondary batteries face stability issues due to volume expansion and excessive formation of the solid electrolyte interphase (SEI) layer, and existing solutions using graphene suffer from low dispersibility and adsorption performance.
Innovation Solution
Functionalized graphene with specific atomic compositions and functional groups is self-adsorbed onto silicon or silicon compounds via electrostatic, hydrogen, and covalent bonding, forming a hybrid material that enhances stability and lithium ion migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to increase capacity, then theoretical capacity increases to about 4,200 mAh/g, but volume expansion of about 300% to 400% occurs causing stability problems
Solution Approach 1:
The patent applies graphene thin film coating on silicon particles to form a flexible protective shell. This graphene shell accommodates the volume expansion of silicon during lithium insertion while maintaining structural integrity, preventing particle disintegration and maintaining electrochemical stability over multiple charge-discharge cycles.
Solution Approach 2:
The patent creates a composite material structure where silicon particles are combined with graphene and conductive polymer. This composite structure leverages the high capacity of silicon, the structural stability and flexibility of graphene, and the conductivity of the polymer to achieve both high capacity and stability simultaneously.
2Quantity of substance
If silicon is used as negative electrode material, then high theoretical capacity is achieved, but excessive formation of solid electrolyte interphase (SEI) layer occurs reducing capacity maintenance
Solution Approach 1:
The graphene thin film acts as a protective barrier that controls SEI layer formation. It allows initial SEI formation but prevents excessive SEI growth in subsequent cycles, maintaining capacity by limiting continuous electrolyte consumption and preserving active silicon material.
Solution Approach 2:
The graphene layer serves as an intermediary between silicon and the electrolyte, mediating the interaction to prevent harmful excessive SEI formation while still allowing necessary lithium ion transport. The conductive polymer further mediates this interface to stabilize the electrochemical response.
3Stability of the object's composition
If graphene is used to cover silicon to solve volume expansion problem, then structural stability improves, but low dispersibility caused by self-cohesiveness of graphene reduces adsorption performance
Solution Approach 1:
The patent modifies graphene parameters by introducing functional groups (oxidation, nitration, sulfonation) that change its surface properties. These chemical modifications reduce self-cohesiveness, improve dispersibility in solvents, and enable better coverage of silicon particles while maintaining the protective function.
Solution Approach 2:
The patent applies different functional groups at different locations on the graphene structure to achieve both dispersibility and stable adsorption. The functionalization creates local variations in chemical properties that facilitate uniform distribution and strong bonding to silicon surfaces.
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 hybrid material achieves a charge capacity of 1600 mAh/g or greater, discharge capacity of 1500 mAh/g or greater, initial efficiency of 90% or greater, and a capacity retention rate of 95% or greater, addressing the stability and SEI layer formation problems.
Implementation Method 1
the functionalized graphene is self-adsorbed onto the silicon or a silicon compound by being bonded to the surface of the silicon or the silicon compound by electrostatic bonding
Implementation Method 2
the functionalized graphene is self-adsorbed onto the silicon or a silicon compound by being bonded to the surface of the silicon or the silicon compound by hydrogen bonding
Implementation Method 3
the functionalized graphene is self-adsorbed onto the silicon or a silicon compound by being bonded to the surface of the silicon or the silicon compound by covalent bonding
Implementation Method 4
lithium ions move from a negative electrode to a positive electrode during a discharge process, and the lithium ions move back from the positive electrode to the negative electrode during charging
Data Source
AI summary
The present invention relates to functionalized graphene having a functional group self-adsorbed onto silicon or a silicon compound, wherein the functionalized graphene has an interplanar distance of about 0.3558 nm to about 0.4790 nm.