Lithium Secondary Battery With High-Surface-Area Silicon Anode
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries exhibit high volume expansion/contraction during charging and discharging, leading to low initial efficiency and irreversible capacity, necessitating improved material designs to enhance battery performance.
Innovation Solution
A lithium secondary battery design incorporating silicon-based particles with a specific surface area four times greater than lithium composite transition metal compound particles, utilizing silicon-carbon composites or silicon oxide particles, and a carbon layer on the silicon-based particles to improve conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based particles are used as negative electrode active material, then battery capacity and high-speed charge characteristics are improved, but volume expansion/contraction increases and initial efficiency decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the specific surface area of silicon-based particles to be 4 times or greater than that of lithium composite transition metal compound particles. This parameter optimization balances the high capacity benefits of silicon with its volume expansion issues, achieving improved initial efficiency while maintaining high battery capacity.
Solution Approach 2:
The patent uses composite materials by combining silicon-based particles with carbon-based materials to form silicon-carbon composite particles. The carbon component provides structural stability during volume expansion while the silicon provides high capacity, resolving the contradiction between capacity improvement and initial efficiency maintenance.
2Productivity
If silicon-based particles with larger specific surface area are used, then lithium-ion reaction efficiency is improved, but side reactions increase
Solution Approach 1:
The patent optimizes the specific surface area parameter of silicon-based particles to be 4 times or greater than lithium composite transition metal compound particles. This controlled parameter change enhances lithium-ion reaction efficiency while the accompanying carbon coating mitigates excessive side reactions, achieving a balance between productivity and harmful effects.
Solution Approach 2:
The patent introduces a carbon layer as an intermediary between the silicon-based particles and the electrolyte. This carbon coating acts as a protective mediator that facilitates lithium-ion transport (improving reaction efficiency) while preventing direct contact between silicon and electrolyte (reducing side reactions).
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 design enhances lithium-ion reaction efficiency, reduces side reactions, and improves battery life and capacity by optimizing the surface area ratio between the silicon-based and transition metal compound particles, resulting in improved initial efficiency and life characteristics.
Implementation Method 1
the silicon-based active material has disadvantages in that a degree of volume expansion/contraction during charging and discharging is high
Implementation Method 2
a carbon layer on the silicon-based particles to improve conductivity and stability
Implementation Method 3
the positive electrode includes, as a positive electrode active material, lithium composite transition metal compound particles including nickel, cobalt, and manganese
Data Source
AI summary
The present invention relates to a lithium secondary battery comprising: a cathode; an anode; and a separator provided between the cathode and the anode, the cathode comprising, as a cathode active material, lithium composite transition metal compound particles in a single particle form containing nickel, cobalt, and manganese, the anode comprising silicon-based particles as an anode active material, wherein the specific surface area of the silicon-based particles is at least four times that of the lithium composite transition metal compound particles.