Silicon Oxide Negative Electrode Coating for Slurry Stability
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Solution Overview
Problem
Lithium ion secondary batteries using silicon as a negative electrode material face challenges in achieving high stability and cycle retention due to the instability of the slurry during production, leading to issues like gas generation and sedimentation, which affects the battery's capacity and efficiency.
Innovation Solution
A negative electrode active material is developed with a silicon compound (SiOx: 0.5≤x≤1.6) coated with carbon and a salt coating containing metal silicates and salts, such as aluminum and magnesium, to enhance water resistance and conductivity, stabilizing the slurry and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the negative electrode active material to improve battery capacity, then the theoretical capacity increases significantly (10 times that of graphite), but the active material expands and contracts during charging/discharging causing cracks to occur and cycle characteristics to degrade
Solution Approach 1:
The patent applies nested structure by placing silicon particles inside a porous carbon coating layer, which is itself enclosed within a protective shell containing Li2SiO3 and metal silicate. This multi-layer nested structure allows the silicon to expand and contract during charging/discharging while being contained and protected by the surrounding layers, preventing crack propagation and maintaining cycle characteristics.
Solution Approach 2:
The patent creates a composite material structure combining silicon particles with carbon coating and Li2SiO3-based protective shell. This composite structure leverages the high capacity of silicon while utilizing the mechanical stability of carbon and the protective properties of Li2SiO3 to mitigate expansion-induced damage, resolving the contradiction between capacity improvement and cycle stability.
2Reliability
If a carbon coating is provided on the superficial layer of silicon oxide particles to improve conductivity, then electron conduction is enhanced, but the slurry stability during production deteriorates due to gas generation and sedimentation
Solution Approach 1:
The patent develops a composite coating structure combining carbon with Li2SiO3 and metal silicate. This composite material provides both the electrical conductivity needed for battery performance and the chemical stability required for slurry processing. The Li2SiO3 component specifically addresses slurry stability by preventing gas generation and sedimentation that occur with carbon-only coatings.
Solution Approach 2:
The patent applies different materials with specific local functions: carbon provides conductivity at the surface, while Li2SiO3 and metal silicate provide chemical stability and slurry compatibility in the protective shell. This local differentiation of material properties allows simultaneous achievement of conductivity and slurry stability.
3Quantity of substance
If the negative electrode active material is designed to achieve high battery capacity, then the energy density increases, but the manufacturing process becomes complex due to multiple coating layers and specific composition requirements
Solution Approach 1:
The patent incorporates Li2SiO3 and metal silicate into the coating structure during the manufacturing process itself, rather than requiring separate post-treatment steps. This preliminary incorporation of protective and stabilizing components simplifies the overall manufacturing process while maintaining the high capacity benefits of silicon-based active material.
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 results in a stable slurry that prevents gas generation and sedimentation, enabling the production of lithium ion secondary batteries with high battery capacity, excellent cycle retention, and improved initial efficiency, suitable for industrial production.
Implementation Method 1
a carbon coating on at least a part of a surface of the silicon compound
Implementation Method 2
a salt coating containing one or more kinds of a metal silicate containing a metal element other than a lithium element and a metal salt containing a metal element other than the lithium element on a part of a surface of the silicon compound or a surface of the carbon coating
Data Source
AI summary
A negative electrode active material for non-aqueous electrolyte secondary batteries which has particles of negative electrode active material, the particles of negative electrode active material containing a silicon compound (SiOx: 0.5≤x≤1.6) that contains a Li compound, including a carbon coating on at least a part of a surface of the silicon compound and a salt coating containing one or more kinds of a metal silicate containing a metal element other than a lithium element and a metal salt containing a metal element other than the lithium element on a part of a surface of the silicon compound or a surface of the carbon coating or both of these. Thus, the negative electrode active material for non-aqueous electrolyte secondary batteries having high stability to an aqueous slurry, high capacity and excellent cycle characteristics and initial efficiency may be provided.