SiOx Negative Electrode Composite for Volume-Stable Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries with silicon-based negative electrodes face limitations due to low initial efficiency and reduced battery life caused by volume expansion during charge and discharge, which existing carbon coating techniques fail to adequately address.
Innovation Solution
A negative electrode active material is developed, comprising a silicon-based composite with pores filled with a polymer and a metal compound, such as lithium, magnesium, or aluminum, combined with a carbon-based material, which improves initial efficiency and life characteristics by suppressing volume changes and preventing side reactions with the electrolyte.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon coating layer is formed on the surface of silicon-based particles, then the surface protection is improved, but the volume expansion during charge and discharge is not sufficiently suppressed and initial efficiency remains low
Solution Approach 1:
The patent uses a composite structure consisting of SiOx core particles, a polymer coating layer, and an outer carbon coating layer. This multi-layer composite structure combines the advantages of each material: SiOx provides high capacity, the polymer layer buffers volume expansion, and the carbon layer provides surface protection and conductivity, thereby resolving the contradiction between surface protection and initial efficiency
Solution Approach 2:
The patent applies different materials with specific functions to different locations: the polymer layer is applied locally at the interface between SiOx and electrolyte to handle volume expansion, while the carbon layer is applied on the outer surface for protection and conductivity. This localized functional distribution optimizes both volume expansion suppression and initial efficiency
2Quantity of substance
If silicon-based particles are used as negative electrode active material, then high discharge capacity is achieved, but volume expansion during charge and discharge reduces battery life
Solution Approach 1:
The patent employs a flexible polymer coating layer (such as polyacrylonitrile or carboxymethyl cellulose) that can elastically deform to accommodate the volume expansion of SiOx particles during lithium insertion. This flexible shell maintains structural integrity during cycling, preventing particle fracture and maintaining battery life while preserving high discharge capacity
Solution Approach 2:
The polymer coating layer is applied beforehand to the SiOx particles to provide a cushioning effect against volume expansion. This pre-applied protective layer absorbs the mechanical stress of expansion and contraction cycles, preventing direct contact between the expanding SiOx and the rigid carbon coating or electrolyte, thereby extending battery life
3Power
If the surface of silicon-based particles is coated with carbon, then electrical conductivity is improved, but side reactions with electrolyte are not sufficiently prevented
Solution Approach 1:
The patent introduces a polymer intermediary layer between the SiOx particles and the electrolyte. This intermediary layer serves dual functions: it prevents direct contact between SiOx and electrolyte to minimize side reactions, while also maintaining ionic conductivity for lithium transport. The carbon outer layer then provides additional protection and electrical conductivity without exposing the polymer to direct electrolyte contact
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 enhances the initial efficiency and life characteristics of lithium secondary batteries by buffering volume expansion and reducing side reactions, leading to improved capacity retention and extended battery life.
Implementation Method 1
a polymer disposed in the pores... buffering volume expansion
Implementation Method 2
a metal compound disposed on a surface of the SiOx (0≤x≤2) or on the surface and inside of the SiOx (0≤x≤2)... preventing side reactions with the electrolyte
Data Source
AI summary
The present invention relates to a negative electrode active material including a silicon-based composite and a carbon-based material, wherein the silicon-based composite includes SiOx (0≤x≤2) including pores, a polymer disposed in the pores, and a metal compound disposed on a surface of the SiOx (0≤x≤2) or on the surface and inside of the SiOx (0≤x≤2), wherein the metal compound is a compound including at least one element selected from the group consisting of lithium (Li), magnesium (Mg), calcium (Ca), and aluminum (Al), a method of preparing the same, and a negative electrode and a lithium secondary battery which include the negative electrode active material.