Negative Electrode Carbon Material for Low Irreversible Capacity
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Solution Overview
Problem
Existing carbon materials used as negative electrode active materials in secondary batteries, particularly lithium-ion batteries, suffer from increased irreversible capacity when produced at lower firing temperatures, necessitating improvements in initial efficiency and long-term storage recovery rates.
Innovation Solution
A carbon material with specific properties, including a volume-based average particle size of 9 µm or less, true density of 2.25 g/cm³ or less, and a Raman R value of 0.50 or less, is developed by mixing natural graphite with an amorphous carbonaceous substance and heating to control crystallinity and disorder, thereby suppressing irreversible capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the firing temperature is lowered to obtain the carbon material, then the manufacturing cost and energy consumption are reduced, but the irreversible capacity increases
Solution Approach 1:
The patent changes the particle size parameter of the carbon material to 9 μm or less, which fundamentally alters the relationship between firing temperature and irreversible capacity. This parameter change allows the material to achieve good initial efficiency and storage recovery rate even at lower firing temperatures, thereby resolving the contradiction between energy consumption and reliability.
Solution Approach 2:
The patent creates a composite carbon material with specific physical properties (particle size ≤9 μm, true density 2.25 g/cm³ or less, Raman R value 0.50 or less) that combines the benefits of low firing temperature processing with low irreversible capacity. This composite approach allows simultaneous optimization of manufacturing efficiency and battery performance.
2Speed
If the particle size is reduced to improve charge-discharge characteristics, then the surface area increases, but the irreversible capacity increases
Solution Approach 1:
The patent optimizes the particle size parameter to a specific range (9 μm or less, with d10 ≤6 μm and d90 ≤15 μm) that balances surface area effects with irreversible capacity. This precise parameter control allows the material to maintain good charge-discharge characteristics while suppressing irreversible capacity increase that would normally occur with smaller particles.
Solution Approach 2:
The patent applies different quality requirements to different aspects of particle characteristics: it specifies strict upper limits for average particle size (9 μm) and fine particle content (d10 ≤6 μm) to ensure charge-discharge performance, while also controlling the overall size distribution (d90 ≤15 μm) to minimize irreversible capacity. This localized quality control resolves the contradiction between speed and reliability.
3Reliability
If the true density is reduced to improve initial efficiency, then the packing efficiency decreases, but the capacity per volume is reduced
Solution Approach 1:
The patent sets the true density parameter to 2.25 g/cm³ or less, which is a specific threshold that balances initial efficiency with volumetric capacity. This parameter change ensures that the carbon material has sufficient porosity and surface area for good initial efficiency while maintaining adequate density for practical battery energy density.
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 carbon material achieves excellent initial efficiency and long-term storage recovery rates without increasing irreversible capacity, enhancing the performance of negative electrodes in secondary batteries.
Implementation Method 1
a non-aqueous lithium secondary battery including a positive electrode and a negative electrode capable of storing and releasing lithium ions
Implementation Method 2
heating to control crystallinity and disorder
Data Source
AI summary
The present invention relates to a carbon material having a volume-based average particle size d50 of 9 µm or less, a true density of 2.25 g/cm3 or less, and a Raman R value of 0.50 or less, the Raman R value being represented by the equation: {(intensity IB of peak PH near 1360 cm-1 in Raman spectrum analysis)/(intensity IA of peak PA near 1580 cm-1 in Raman spectrum analysis)}.