Graphene-Coated Silicon Oxide Composite Anodes for Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based anode materials in lithium-ion batteries face rapid cycle life degradation, poor charge-discharge rate capability, and low coulombic efficiency due to extreme volume changes during lithiation and delithiation, leading to electrical disconnection and unstable solid electrolyte interface (SEI) formation.
Innovation Solution
The use of composite particles with a core particle of alkali metal or alkali earth metal silicate coated with low-defect turbostratic carbon, which provides improved electrical conductivity and stability through a flexible, conductive graphene-containing coating that minimizes stress and maintains electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode materials are used to achieve high energy density, then the theoretical gravimetric capacity increases to about 4,200 mAh/g, but the cycle life degrades rapidly due to extreme volume changes during charge and discharge
Solution Approach 1:
The silicon core is nested within a carbon shell structure, creating a core-shell composite where the silicon particle is encapsulated by carbon material. This nesting approach allows the high-capacity silicon to be protected from mechanical degradation while maintaining its lithium storage functionality, resolving the contradiction between high capacity and cycle life stability
Solution Approach 2:
The invention uses composite materials combining silicon with carbon (graphene or graphite) to create a hybrid anode structure. The silicon provides high theoretical capacity while the carbon matrix provides structural stability and conductivity, enabling the composite to achieve both high energy density and improved cycling stability that neither material could achieve alone
2Quantity of substance
If silicon particles undergo lithiation and delithiation to store lithium ions, then the lithium storage capacity increases, but the volume expansion reaches up to 400% causing pulverization and electrical disconnection
Solution Approach 1:
The carbon shell surrounding the silicon core acts as a flexible protective layer that can accommodate the volume expansion of silicon during lithiation while maintaining structural integrity. The shell's flexibility allows it to stretch and contract with the silicon particle without fracturing, preventing pulverization and maintaining electrical contact throughout cycling
Solution Approach 2:
The carbon coating is applied beforehand to the silicon particles, creating a protective cushion that absorbs and distributes the mechanical stress generated during volume expansion. This pre-applied protective layer prevents direct exposure of silicon to mechanical degradation forces, reducing pulverization before it occurs
3Power
If silicon-based anodes are used to achieve high power density, then the charge-discharge rate capability should improve, but the coulombic efficiency remains subpar due to unstable SEI formation
Solution Approach 1:
The carbon shell serves as an intermediary layer between the silicon core and the electrolyte, mediating the formation of the solid electrolyte interface (SEI). This intermediate carbon layer provides a stable surface for SEI formation, preventing direct and unstable interactions between silicon and electrolyte that would otherwise lead to poor coulombic efficiency and continuous SEI growth
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
This solution significantly enhances the cycle life and rate performance of silicon-based anode materials, achieving over 300 cycles with more than 90% capacity retention, compared to uncoated materials which typically experience 90% capacity fade within 20 cycles.
Implementation Method 1
graphene-containing metalized silicon oxide composite materials
Implementation Method 2
provides improved electrical conductivity and stability through a flexible, conductive graphene-containing coating that minimizes stress and maintains electrical contact
Data Source
AI summary
Active material composite particles, an electrode including the composite particles, a lithium ion secondary battery including the electrode, and method of forming the same, in which the composite particles each include a core particle including an alkali metal or an alkali earth metal silicate, and a coating disposed on the surface of the core particle. The coating includes turbostratic carbon having a Raman spectrum having: a D band having a peak intensity (ID) at wave number between 1330 cm−1 and 1360 cm−1; a G band having a peak intensity (IG) at wave number between 1580 cm−1 and 1600 cm−1; and a 2D band having a peak intensity (I2D) at wave number between 2650 cm−1 and 2750 cm−1, wherein a ratio of ID/IG ranges from greater than zero to about 1.1, and a ratio of I2D/IG ranges from about 0.4 to about 2.