Carbon-Coated Silicon Oxide Anodes for Irreversible Capacity Loss
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Solution Overview
Problem
Existing high capacity negative electrode materials, particularly silicon and silicon oxide, suffer from high irreversible capacity loss and poor discharge and recharge cycling due to structural changes and large volume expansions, leading to decreased cycling efficiency in lithium ion batteries.
Innovation Solution
The use of silicon oxide based active materials in lithium ion batteries, combined with supplemental lithium and electrically conductive components, and optimized electrode structures, such as composites with smaller particles and pyrolytic carbon coatings, to stabilize the negative electrode and improve cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide based active material is used in negative electrode, then specific capacity is improved, but irreversible capacity loss increases and cycling stability deteriorates
Solution Approach 1:
The patent applies composite materials by combining silicon oxide particles with conductive carbon materials and binder materials to form a composite negative electrode. The silicon oxide provides high specific capacity while the carbon matrix and binder provide structural stability, reducing irreversible capacity loss and improving cycling stability. The composite structure allows the silicon oxide to expand and contract during lithium insertion/extraction without destroying the electrode integrity.
Solution Approach 2:
The patent employs a carbon-based coating or matrix that acts as a flexible shell around silicon oxide particles. This shell accommodates the volume expansion of silicon oxide during lithiation while maintaining structural integrity. The flexible carbon structure prevents particle aggregation and maintains electrical conductivity throughout cycling, thereby improving cycling stability.
2Use of energy by moving object
If silicon oxide based active material is used in negative electrode, then energy density is improved, but volume expansion increases leading to structural degradation
Solution Approach 1:
The patent creates a composite structure where silicon oxide particles are embedded in a carbon matrix. The carbon component provides mechanical strength and structural stability, preventing the electrode from degrading despite the volume expansion of silicon oxide during cycling. This composite approach maintains both high energy density and structural integrity.
Solution Approach 2:
The carbon binder and conductive carbon materials act as intermediaries between the silicon oxide particles and the electrode current collector. This intermediary structure absorbs and distributes the mechanical stress from volume expansion, preventing direct transmission of stress that would cause structural degradation. The intermediary carbon phase maintains electrode integrity while allowing silicon oxide to undergo volume changes.
3Quantity of substance
If high capacity negative electrode material is used, then battery capacity is improved, but manufacturing complexity increases due to need for composite structures and coatings
Solution Approach 1:
The patent merges multiple functions into a single composite material system. The carbon matrix simultaneously provides electrical conductivity, mechanical strength, and structural stability. The binder material concurrently holds particles together and accommodates volume changes. This merging of functions into integrated composite structures simplifies manufacturing compared to applying separate coatings and assemblies.
Solution Approach 2:
The patent optimizes parameters such as particle size distribution, carbon content ratio, and binder composition to achieve high capacity while maintaining manufacturability. By carefully controlling these parameters, the composite structure can be manufactured using conventional battery manufacturing processes, reducing complexity despite the advanced material system.
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 results in lithium ion batteries with improved cycling stability and high specific capacity, maintaining discharge capacity over multiple cycles and reducing irreversible capacity loss, suitable for commercial applications.
Implementation Method 1
structural changes and large volume changes can destroy the structural integrity of the electrode, thereby decreasing the cycling efficiency... associated with lithium intercalation/alloying
Implementation Method 2
structural changes and large volume changes can destroy the structural integrity of the electrode, thereby decreasing the cycling efficiency... associated with lithium intercalation/alloying
Implementation Method 3
composites with smaller particles and pyrolytic carbon coatings
Data Source
AI summary
Silicon oxide based materials, including composites with various electrical conductive compositions, are formulated into desirable anodes. The anodes can be effectively combined into lithium ion batteries with high capacity cathode materials. In some formulations, supplemental lithium can be used to stabilize cycling as well as to reduce effects of first cycle irreversible capacity loss. Batteries are described with surprisingly good cycling properties with good specific capacities with respect to both cathode active weights and anode active weights.