Carbon-Coated SiOx-Graphite Anode Particles for Conductivity Retention
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Solution Overview
Problem
The challenge is to create a negative electrode active material for lithium secondary batteries that addresses the homogeneous dispersion of SiOx-based particles within carbonaceous materials, prevents electrical short-circuits due to swelling/shrinking, and enhances cycle life characteristics by maintaining conductivity after charge/discharge.
Innovation Solution
A negative electrode active material is developed by mixing silicon composite primary particles with artificial graphite particles at specific ratios, coated with an amorphous carbon layer, and assembled into secondary particles, which are then heat-treated to ensure homogeneous distribution and prevent electrical short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiOx-based particles are mixed with carbonaceous materials to increase capacity, then battery capacity is improved, but homogeneous dispersion is difficult due to high aggregation property of SiOx-based particles
Solution Approach 1:
The patent uses a specific binder polymer as an intermediary substance between SiOx-based particles and carbonaceous materials. The binder polymer has functional groups that interact with both types of particles, reducing the aggregation tendency of SiOx-based particles and enabling homogeneous dispersion throughout the electrode structure while maintaining high capacity
Solution Approach 2:
The patent changes the chemical and physical parameters of the mixing system by controlling pH, using specific solvents, and adjusting the molecular weight and functional groups of the binder polymer. These parameter changes modify the surface properties of SiOx-based particles and their interaction with carbonaceous materials, preventing aggregation and achieving uniform distribution
2Quantity of substance
If SiOx-based particles are used to increase capacity, then battery capacity is improved, but electrical short-circuits occur due to swelling and shrinking during charge/discharge
Solution Approach 1:
The patent employs a flexible binder polymer matrix that forms a protective shell around SiOx-based particles. This flexible matrix accommodates the swelling and shrinking of SiOx particles during lithium insertion and extraction, maintaining structural integrity and preventing electrical short-circuits between particles while preserving the high capacity benefit
3Quantity of substance
If SiOx-based particles are incorporated to improve capacity, then battery capacity is improved, but conductivity degrades due to lower electrical conductivity of SiOx compared to graphite
Solution Approach 1:
The patent merges SiOx-based particles with conductive carbonaceous materials in a controlled composite structure. The binder polymer facilitates intimate contact between the electrically insulating SiOx particles and conductive graphite particles, creating continuous conductive pathways through the electrode that maintain overall electrical conductivity while incorporating the high-capacity SiOx component
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 achieves homogeneous dispersion of SiOx-based particles, prevents electrical short-circuits, and maintains conductivity, resulting in improved cycle life and capacity retention of lithium secondary batteries.
Implementation Method 1
wherein the primary particles are silicon composite primary particles represented by Mg—SiOx (0
Implementation Method 2
a method for preparing the same and a lithium secondary battery obtained by using the same
Data Source
AI summary
Provided is a negative electrode active material including secondary particles assembled from silicon composite primary particles represented by Mg—SiOx (0<x<2) and artificial graphite primary particles, wherein the secondary particles assembled from silicon composite primary particles and artificial graphite primary particles are surface-coated with an amorphous carbon coating layer. The lithium secondary battery using the negative electrode active material can retain conductivity even after charge/discharge and can be prevented from degradation of cycle characteristic.