Composite Negative Electrode Particles for Battery Capacity Retention
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Solution Overview
Problem
Current non-aqueous electrolyte secondary batteries face limitations in energy density and capacity retention due to the expansion of inorganic particles like silicon, which can lead to cracking of the carbonaceous material and side reactions with the electrolyte, reducing the battery's performance and lifespan.
Innovation Solution
A negative electrode material comprising composite particles with a carbonaceous material layer having a specific porosity range and a second covering layer that inhibits direct contact between the inorganic particles and the electrolyte, preventing side reactions and expansion, thereby enhancing charge and discharge capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If inorganic particles like silicon are used to increase capacity, then the battery capacity increases significantly, but the inorganic particles expand during charging and discharging, causing cracking of the carbonaceous material and side reactions with the electrolyte
Solution Approach 1:
The patent employs a porous carbonaceous material layer with controlled porosity (4.3%-10.0% in the first region) to accommodate the expansion of inorganic particles during lithium insertion. The porous structure provides buffer space that prevents cracking while maintaining electrical conductivity and preventing electrolyte contact
Solution Approach 2:
The patent creates a composite structure consisting of inorganic particles (silicon, tin, or zinc) embedded in a carbonaceous material matrix. This composite approach combines the high capacity of inorganic materials with the structural stability and conductivity of carbonaceous materials, resolving the contradiction between capacity and reliability
2Object-affected harmful factors
If the carbonaceous material layer is made dense to prevent side reactions, then protection against electrolyte is improved, but the expansion of inorganic particles is restricted, leading to cracking and reduced capacity retention
Solution Approach 1:
The patent utilizes a porous carbonaceous material layer that balances protection and accommodation functions. The controlled porosity allows the structure to expand with the inorganic particles while the carbonaceous material itself acts as a barrier to electrolyte, preventing side reactions
Solution Approach 2:
The patent applies different porosity characteristics to different regions of the carbonaceous material layer. The first region (closer to the inorganic particle surface) has porosity of 4.3%-10.0% to accommodate expansion, while the second region (outer region) has porosity of 0.1%-5.0% to provide protection, creating local quality variations that satisfy different functional requirements
3Reliability
If graphite-based materials are used for negative electrodes, then the electrode structure remains stable, but the capacity is limited to the theoretical value of 372 mAh/g
Solution Approach 1:
The patent replaces pure graphite-based materials with composite particles containing inorganic materials (silicon, tin, or zinc) that have higher theoretical capacities (e.g., silicon can occlude 4.4 lithium atoms per silicon atom, about 10 times that of graphite). The carbonaceous material component maintains structural stability while the inorganic component provides high capacity
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 proposed solution effectively inhibits the expansion of inorganic particles and reduces side reactions, resulting in improved charge and discharge capacity retention and high-rate performance of non-aqueous electrolyte secondary batteries.
Implementation Method 1
The carbonaceous material layer has a first region having a porosity of 4.3% or more and 10.0% or less, the first region being a region extending from the surface of the inorganic particle to the surface of an imaginary sphere that is centered at the center of the inorganic particle and has a radius of 3r
Implementation Method 2
one or more covering layers, each of which is in contact with a surface of the inorganic particle
Data Source
AI summary
A negative electrode material for a non-aqueous electrolyte secondary battery includes a plurality of composite particles. Each of the plurality of composite particles includes an inorganic particle, one or more covering layers, each of which is in contact with a surface of the inorganic particle, and a carbonaceous material layer that covers the inorganic particle and has voids. The carbonaceous material layer includes a first region having a porosity of 4.3% or more and 10.0% or less, the first region being a region extending from the surface of the inorganic particle to the surface of an imaginary sphere that is centered at the center of the inorganic particle and has a radius of 3r, where r is a radius of the inorganic particle. Each of the voids is separated by one of the one or more covering layers from the surface of the inorganic particle.