Silicon Anode Composite With Dual MgSiO3 Phases for Volume Stability
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Solution Overview
Problem
Silicon-based negative electrode active materials in secondary batteries face issues with reduced initial efficiency and lifespan due to reactions with lithium ions and excessive volume expansion, which are not adequately addressed by metal doping alone.
Innovation Solution
A negative electrode active material comprising silicon-based composite particles with a MgSiO3 phase, including both enstatite and clinoenstatite structures at a specific weight ratio, which improves structural stability and minimizes electrolyte side reactions, thereby enhancing battery capacity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal doping is applied to silicon-based particles to block reaction sites, then initial efficiency is improved, but capacity per weight is significantly reduced
Solution Approach 1:
The patent changes the chemical composition parameters by forming MgSiO3 compound with specific SiO2:Mg ratio (1.05:1 to 1.5:1) and controlling the phase structure (enstatite and clinoenstatite ratio of 1:1 to 1:5), thereby improving initial efficiency without significantly reducing capacity per weight compared to conventional metal doping
Solution Approach 2:
The patent uses composite material MgSiO3 formed by reacting SiO2 and Mg, which combines the benefits of blocking irreversible reaction sites while maintaining lighter weight and higher capacity per weight compared to conventional metal doping approaches
2Quantity of substance
If silicon-based particles are used as negative electrode active material, then discharge capacity is improved, but volume expansion occurs during charge
Solution Approach 1:
The MgSiO3 compound acts as an intermediary layer surrounding the silicon core, mediating the volume expansion during charge by providing a buffer structure that accommodates expansion while maintaining structural integrity and preventing excessive volume increase
Solution Approach 2:
The patent changes the structural parameters by creating a composite structure with specific phase ratios (enstatite:clinoenstatite = 1:1 to 1:5) and SiO2:Mg ratio (1.05:1 to 1.5:1), which controls the volume expansion behavior during charge while maintaining high discharge capacity
3Quantity of substance
If SiO2 in silicon-based particles reacts with lithium ions, then capacity is improved, but initial efficiency and life characteristics are reduced
Solution Approach 1:
The patent optimizes the SiO2:Mg ratio to 1.05:1 to 1.5:1 and controls the MgSiO3 phase composition (enstatite:clinoenstatite = 1:1 to 1:5), which regulates the reactivity with lithium ions to achieve appropriate capacity while improving initial efficiency and life characteristics
Solution Approach 2:
The patent creates local quality differences by forming MgSiO3 compound with specific phase distribution, where the enstatite and clinoenstatite phases provide different local properties that collectively improve initial efficiency and life characteristics while maintaining capacity
Data Source
AI summary
The present invention relates to: a negative electrode active material including silicon-based composite particles containing SiOx (0<x<2) and a MgSiO3 phase, wherein the MgSiO3 phase includes a first MgSiO3 phase having an enstatite structure and a second MgSiO3 phase having a clinoenstatite structure at a weight ratio of 1:1 to 1:5; a negative electrode including the same; and a secondary battery including the negative electrode.