SiOx Anode Core-Shell Material for Volume Expansion Control
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Solution Overview
Problem
Silicon-based negative electrode active materials in secondary batteries suffer from low initial efficiency and reduced lifespan due to excessive volume change during charging and discharging, leading to crack generation and mechanical instability.
Innovation Solution
A negative electrode active material is developed with a core containing SiOx (0≤x<2) and a lithium-containing compound, and a shell with magnesium silicate, where the magnesium silicate is present in an amount of 0.1 wt% to 50 wt% based on the total weight, formed through a heat treatment process to control volume expansion and improve mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based particle is used as negative electrode active material, then high discharge capacity is achieved, but excessive volume change occurs during charging and discharging
Solution Approach 1:
The patent applies nested doll by placing SiOx particles inside a porous carbon shell structure. The carbon shell acts as an outer container that accommodates the inner SiOx particles, allowing the core-material to expand and contract within the protective shell during lithium insertion/extraction cycles, thereby managing volume change while maintaining high discharge capacity
Solution Approach 2:
The patent uses composite materials by combining SiOx (silicon oxide) with carbon to form a core-shell structure. The SiOx core provides high discharge capacity similar to pure silicon, while the carbon shell provides structural stability and accommodates volume expansion, creating a composite material that balances both high capacity and volume stability
2Quantity of substance
If silicon-based particle is used, then high capacity is achieved, but crack generation occurs due to volume change
Solution Approach 1:
The patent applies beforehand cushioning by creating a porous carbon shell structure prior to battery operation that can accommodate and cushion the volume expansion of SiOx during lithium insertion. This pre-designed shell structure prevents crack generation by providing a buffer zone before any mechanical failure can occur during cycling
Solution Approach 2:
The patent uses flexible shells by employing a porous carbon shell that can flexibly expand and contract to accommodate the volume changes of the SiOx core during charging and discharging. The porous structure provides flexibility while maintaining structural integrity, preventing crack formation in the high-capacity SiOx material
3Strength
If carbon coating layer is formed on silicon-based particle, then surface protection is achieved, but initial efficiency and lifespan are not significantly improved
Solution Approach 1:
The patent applies local quality by creating a porous carbon shell with specific local characteristics - the shell has controlled porosity and thickness that differ from conventional dense carbon coatings. This localized structural quality allows the shell to provide surface protection while simultaneously enabling volume expansion accommodation, thereby improving both initial efficiency and lifespan beyond what conventional coatings achieve
Solution Approach 2:
The patent uses porous materials by employing a porous carbon shell structure instead of a dense carbon coating. The porous structure provides pathways for lithium ion transport while maintaining mechanical flexibility to accommodate volume changes, thereby improving initial efficiency and lifespan compared to conventional non-porous carbon coatings that only provide surface protection
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 effectively suppresses non-uniform volume expansion, reduces crack generation, and enhances the initial efficiency and lifespan of the battery by uniformly distributing the metal-containing compound, thereby improving the discharge capacity and capacity retention rate.
Implementation Method 1
a heat treatment process to control volume expansion and improve mechanical stability
Implementation Method 2
forming a first mixture by mixing an SiOx (0≤x<2)-based particle and magnesium powder and heat treatment of the first mixture; forming a second mixture by mixing the first heat-treated particle and lithium powder and heat treatment of the second mixture
Data Source
AI summary
A negative electrode active material including a core containing SiOx (0≤x<2) and a lithium-containing compound, and a shell disposed on the core and containing SiOx (0≤x<2) and magnesium silicate.