Carbon Nanowall Negative Electrode for Lithium Battery
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Solution Overview
Problem
Lithium secondary batteries using negative electrode active substances like tin or silicon face structural collapse and reduced battery capacity due to volume changes during charging and discharging, leading to broken electrical conduction paths and reduced Li ion occlusion efficiency.
Innovation Solution
A negative electrode configuration where carbon nanowalls are formed on the collector, supporting the active substance, which acts as a spacer to maintain layer thickness and ensure electrical conductivity, preventing structural collapse and enhancing Li ion occlusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium alloy such as tin or silicon is used as a negative electrode active substance to achieve high battery capacity, then the charging and discharging capacity exceeds that of graphite, but the volume change during charging and discharging causes structural collapse and broken electrical conduction paths
Solution Approach 1:
The negative electrode active substance layer is divided into multiple particles dispersed throughout the carbon matrix. This segmentation prevents monolithic structural collapse by distributing volume changes across many small units, each capable of independent expansion and contraction without compromising the overall layer integrity.
Solution Approach 2:
Carbon material is incorporated into the negative electrode active substance layer before charging and discharging cycles begin. This preliminary incorporation of carbon creates a pre-formed conductive network that anticipates and compensates for future volume changes, maintaining electrical connectivity throughout the substance's lifecycle.
Solution Approach 3:
The negative electrode is constructed as a composite material combining lithium alloy particles with carbon material. This composite structure leverages the high capacity of lithium alloy while the carbon component provides structural stability and electrical conductivity, resolving the contradiction between capacity and stability.
2Quantity of substance
If a lithium alloy such as tin or silicon is used as a negative electrode active substance to achieve high battery capacity, then the charging and discharging capacity exceeds that of graphite, but the electrical conduction paths are broken due to volume change
Solution Approach 1:
The negative electrode is constructed as a composite material combining lithium alloy particles with carbon material. This composite structure leverages the high capacity of lithium alloy while the carbon component provides structural stability and electrical conductivity, resolving the contradiction between capacity and stability.
Solution Approach 2:
Carbon material is incorporated into the negative electrode active substance layer before charging and discharging cycles begin. This preliminary incorporation of carbon creates a pre-formed conductive network that anticipates and compensates for future volume changes, maintaining electrical connectivity throughout the substance's lifecycle.
3Quantity of substance
If a lithium alloy such as tin or silicon is used as a negative electrode active substance to achieve high battery capacity, then the charging and discharging capacity exceeds that of graphite, but the Li ion occlusion efficiency is reduced due to volume change
Solution Approach 1:
The negative electrode active substance layer is divided into multiple particles dispersed throughout the carbon matrix. This segmentation prevents monolithic structural collapse by distributing volume changes across many small units, each capable of independent expansion and contraction without compromising the overall layer integrity.
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
This configuration maintains the negative electrode active substance layer's structure and conductivity, enabling high battery capacity, excellent cycle characteristics, and low internal resistance, suitable for vehicles.
Implementation Method 1
the carbon nanowalls serve to act as a spacer during the shrinkage of the negative electrode active substance so that the thickness (volume) of the negative electrode active substance layer is maintained
Implementation Method 2
because the negative electrode active substance is supported on the carbon nanowalls that have a high electrical conductivity, the electrical conductivity (electron transfer) between the negative electrode active substances and/or between the negative electrode active substance and the negative electrode collector is ensured through the carbon nanowalls
Implementation Method 3
various problems are caused due to a volume change of the negative electrode active substance, because such an alloy expands and shrinks more than graphite does during charging and discharging procedures
Data Source
AI summary
A negative electrode (10) for a lithium secondary battery, including a negative electrode collector (20), and a negative electrode active substance layer (30) that is supported on the negative electrode collector (20) and includes carbon nanowalls (32) which are formed on the negative electrode collector (20), and a negative electrode active substance (36) which is supported on the carbon nanowalls (32).