Negative Electrode Active Material for Lithium Secondary Battery
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Solution Overview
Problem
Conventional lithium secondary batteries using carbon-based active materials face challenges such as low discharge voltage, poor high-temperature characteristics, and reduced electrode adhesive strength, particularly with artificial graphite, while natural graphite offers high capacity but risks swelling and poor high-temperature performance.
Innovation Solution
A negative electrode active material comprising a blend of natural graphite particles and soft carbon particles with a BET specific surface area of 7.6 m2/g or more, in a weight ratio of 78:22 to 92:8, which improves output characteristics, high-temperature storage, and cycle characteristics by reducing lithium ion transfer resistance and preventing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural graphite is used as the negative electrode active material, then capacity and output are improved, but high-temperature characteristics deteriorate due to swelling and functional groups on the surface
Solution Approach 1:
The patent uses a composite material system consisting of natural graphite particles combined with soft carbon particles having specific surface area characteristics. This composite structure allows the natural graphite to provide high capacity while the soft carbon component mitigates swelling and improves high-temperature stability, thereby resolving the contradiction between capacity and high-temperature characteristics
2Reliability
If artificial graphite is used as the negative electrode active material, then high-temperature characteristics are improved, but electrode adhesive strength and processability deteriorate due to secondary particles and coating treatment
Solution Approach 1:
The patent combines natural graphite particles with soft carbon particles to create a composite that maintains good electrode adhesive strength and processability while providing improved high-temperature characteristics. The soft carbon component facilitates better slurry preparation and coating without the secondary particle formation issues associated with artificial graphite
3Reliability
If graphite-based active material is used, then reversible intercalation and deintercalation of lithium ions is achieved, but discharge voltage is reduced to -0.2V compared to lithium
Solution Approach 1:
The patent optimizes the surface area parameters of the soft carbon particles (BET specific surface area of 7.6-20.0 m²/g) and controls the particle size distribution to enhance lithium ion transfer kinetics. This parameter optimization allows the graphite-based material to maintain reversibility while improving the discharge voltage characteristics by reducing transfer resistance
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 blended material enhances the battery's output, high-temperature storage, and cycle performance by maintaining structural integrity and reducing lithium ion transfer resistance, enabling stable operation and improved capacity retention under high-temperature conditions.
Implementation Method 1
soft carbon particles having a BET specific surface area of 7.6 m2/g or more
Implementation Method 2
carbon-based active materials enabling reversible intercalation and deintercalation of lithium ions
Data Source
AI summary
A negative electrode active material for a lithium secondary battery, which includes: natural graphite particles; and soft carbon particles having a BET specific surface area of 7.6 m2/g or more, wherein the natural graphite particles and the soft carbon particles are present in the negative electrode active material at a range of weight ratio of 78:22 to 92:8. Also a negative electrode containing the negative electrode active material and a lithium secondary battery containing the negative electrode.