Si-O-C Anode Composite Structure for Stress and Side-Reaction Control
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Solution Overview
Problem
Existing negative electrode active materials for secondary batteries face challenges such as significant expansion and contraction during charging and discharging, low capacity, and irreversible capacity issues, leading to material deterioration and side reactions with the electrolyte.
Innovation Solution
A composite material is developed comprising an active phase that reacts with lithium, dispersed within an amorphous material phase containing silicon, oxygen, and carbon, which relieves stress and suppresses side reactions by forming a sea-island structure with a continuous amorphous material phase, preventing electrolyte penetration and grain boundary formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a metal-based active material including a first ceramic coating layer is used, then the material can be alloyed with lithium, but significant expansion and contraction occurs during charging and discharging
Solution Approach 1:
The patent uses a composite material consisting of a metal-based active material (such as silicon, tin, or aluminum) coated with a ceramic layer. This composite structure allows the material to alloy with lithium while the ceramic coating provides structural stability and reduces expansion and contraction during charging and discharging cycles.
Solution Approach 2:
The ceramic coating is applied locally on the surface of the metal-based active material particles. This local modification provides protective properties (reduced expansion, improved stability) only where needed at the surface, while the core metal material retains its high lithium alloying capability.
2Ease of manufacture
If a porous amorphous material is used, then the material can be produced through chemical vapor deposition, but the capacity is low and insufficient
Solution Approach 1:
The patent combines a metal-based active material with high theoretical capacity with a ceramic coating layer. This composite structure achieves both ease of manufacture (through established coating processes) and high lithium capacity (through the high-capacity metal core), overcoming the limitations of porous amorphous materials.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the active material by applying a ceramic coating, which changes the surface properties while maintaining the bulk capacity. This allows the material to achieve both manufacturability and high capacity by controlling coating thickness, composition, and structure.
3Adaptability or versatility
If a material including Si and O as constituent elements is used, then the material can be formed as a composite with carbon, but large irreversible capacity occurs and capacity control is difficult
Solution Approach 1:
The patent applies a ceramic coating layer with specific composition (containing Si and O) on the surface of the metal-based active material. This local modification provides protective and stabilizing properties, reducing irreversible capacity while maintaining adaptability with carbon-based materials in the composite electrode structure.
Solution Approach 2:
The ceramic coating layer creates an inert protective environment around the metal-based active material, preventing unwanted side reactions with the electrolyte and reducing irreversible capacity. This protective barrier allows for better capacity control while maintaining material compatibility with other electrode components.
4Strength
If silicon is dispersed in lithium silicate and sintered, then a composite material is formed, but the electrolyte penetrates into grain boundaries and causes side reactions
Solution Approach 1:
The patent uses a ceramic coating layer as a flexible protective shell around the metal-based active material particles. This thin film barrier prevents electrolyte penetration into grain boundaries and internal structures, eliminating side reactions while maintaining the density and strength benefits of sintered composites.
Solution Approach 2:
The patent creates a composite structure with a metal-based active material core and a ceramic coating layer. This composite design provides both the density and strength of sintered materials and the protective barrier against electrolyte penetration, overcoming the harmful effects of grain boundary exposure.
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 material achieves high capacity and improved cycle characteristics with reduced deterioration, enhancing the stability and performance of secondary batteries.
Implementation Method 1
the amorphous material phase includes Si, O, and C... which relieves stress and suppresses side reactions
Implementation Method 2
heating the mixture to a temperature of 650 to 1350° C. in a non-oxidizing gas and allowed to react to produce an amorphous material including silicon, carbon, and oxygen
Data Source
AI summary
A negative electrode active material for a secondary battery includes a composite material including an active phase that reacts with Li and an amorphous material phase, wherein the active phase is dispersed in the amorphous material phase, and the amorphous material phase includes Si, O, and C.