Negative Electrode Active Material for Li-Ion Battery
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Solution Overview
Problem
Lithium ion batteries face issues with rapid capacity degradation and safety concerns due to the reaction of carbon black with the electrolytic solution, leading to increased resistance and metal lithium precipitation on the negative electrode surface, especially during high-temperature environments and long-term use.
Innovation Solution
A negative electrode comprising a combination of spherical graphite and massive graphite as active materials, with a sulfur concentration of 0-300 ppm, and a plate-like graphite electrical conduction aid, forming a stable SEI film to prevent capacity degradation and ensure safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black is used to ensure electrical conductivity, then resistance is reduced, but metal lithium precipitation occurs on negative electrode surface during charging
Solution Approach 1:
The patent extracts carbon black from the negative electrode formulation, eliminating the source of harmful interactions with electrolytic solution that lead to metal lithium precipitation. The spherical graphite with low sulfur concentration provides conductivity without triggering the side reactions that cause lithium precipitation.
Solution Approach 2:
By controlling sulfur concentration to 0-300 ppm, the patent modifies the chemical properties of the graphite material to prevent unstable SEI film formation. This parameter change ensures that charging proceeds normally without metal lithium precipitation on the electrode surface.
2Quantity of substance
If conventional graphite materials are used for long-term battery operation, then initial capacity is achieved, but rapid fading phenomenon occurs during extended use
Solution Approach 1:
The patent applies parameter changes to the sulfur concentration (0-300 ppm) and particle morphology (spherical with 10-50 μm diameter) of the graphite material. These parameter optimizations ensure stable SEI film formation that prevents rapid capacity fading, enabling the battery to maintain performance over extended periods while preserving initial capacity.
Solution Approach 2:
The patent creates an optimized composite structure using spherical graphite particles with controlled sulfur content, combined with specific binders (PVDF, CMC, or SBR) and conductive additives. This composite approach ensures both high initial capacity and long-term stability by preventing the rapid fading phenomenon associated with conventional materials.
3Power
If high temperature operation is permitted, then power delivery is maintained, but capacity degradation accelerates and safety risks increase
Solution Approach 1:
The patent uses parameter changes in the graphite material (sulfur concentration 0-300 ppm, spherical morphology) to create thermal stability. This allows the battery to operate at high temperatures while maintaining power delivery, as the stabilized SEI film prevents accelerated degradation that would normally occur under thermal stress.
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 effectively prevents rapid capacity degradation and ensures safety by forming a stable SEI film, maintaining battery performance even in high-temperature environments and extending the battery's lifespan.
Implementation Method 1
forming a stable SEI film to prevent capacity degradation and ensure safety
Data Source
AI summary
The present invention relates to a negative electrode for a lithium ion secondary battery, the negative electrode containing a negative electrode active material containing a first carbon and a second carbon, in which the first carbon is spherical graphite, the second carbon is massive graphite, and the sulfur concentration in the first carbon (Sx) and the sulfur concentration in the second carbon (Sy) are each independently 0 ppm or more and 300 ppm or less.