Multilayer Carbon Negative Electrode for Battery Cycle Life
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Solution Overview
Problem
Current nonaqueous lithium secondary batteries fail to achieve high capacity, rapid charging-discharging properties, and cycle characteristics required for modern applications such as electric power tools and electric cars, despite advancements in negative electrode materials.
Innovation Solution
A negative electrode material comprising two types of carbon materials, Carbon Material A and Carbon Material B, where Carbon Material A has a multilayer structure with high crystallinity and amorphous carbon coating, and Carbon Material B is a graphitic particle with enhanced electron conductivity, are combined to achieve both rapid charge-discharge characteristics and high cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous carbon particles are used to improve cycle characteristics, then cycle characteristics are improved, but irreversible capacity increases
Solution Approach 1:
The patent applies local quality by creating a multilayer structure where the outer layer consists of amorphous carbon particles (providing stability and cycle characteristics) and the inner layer consists of graphitic carbon particles (providing high capacity and low irreversible capacity). This layered structure allows different regions of the composite particle to have different functional properties, resolving the contradiction between cycle characteristics and irreversible capacity.
2Quantity of substance
If graphitic carbon materials are used to achieve high capacity, then high capacity is achieved, but rapid charge-discharge characteristics are insufficient
Solution Approach 1:
The patent uses composite materials by combining graphitic carbon particles (high capacity) with amorphous carbon particles (rapid charge-discharge characteristics) to form a multilayer composite structure. The amorphous carbon outer layer provides excellent electron conductivity and rapid charge-discharge properties, while the graphitic carbon inner layer provides high capacity, thus resolving the contradiction between capacity and charge-discharge speed.
3Speed
If surface coating with amorphous carbon is applied to graphitic particles, then rapid charge-discharge characteristics are improved, but electron conductivity decreases
Solution Approach 1:
The patent applies parameter changes by controlling the particle size ratio between amorphous carbon and graphitic carbon, and by optimizing the thickness and composition of the multilayer structure. By adjusting these parameters, the patent achieves a balance where the amorphous carbon layer provides rapid charge-discharge characteristics while the graphitic carbon core maintains high electron conductivity, resolving the contradiction between charge-discharge speed and conductivity.
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 combination of these carbon materials results in a nonaqueous electrolyte secondary battery with excellent rapid charging-discharging properties and high cycle characteristics, suitable for demanding applications like electric power tools and electric cars.
Implementation Method 1
the interplanar spacing (d002) of 002 planes by the wide-angle X-ray diffraction method
Data Source
AI summary
To provide a mixed carbon material used for an electrode of a nonaqueous secondary battery with excellent characteristics satisfying both rapid charge-discharge characteristics and high cycle characteristics. A negative electrode material for nonaqueous electrolyte secondary battery, comprising the following carbon material A and carbon material B: (Carbon material A) a multilayer-structure carbon material containing a graphitic particle and an amorphous carbon covering the surface of the graphitic particle, which is a carbon material where the interplanar spacing (d002) of 002 planes by the wide-angle X-ray diffraction method is 3.37 Å or less, Lc is 900 Å or more, the tap density is 0.8 g/cm3 or more, and the Raman R value that is a ratio of the peak intensity near 1,360 cm-1 to the peak intensity near 1,580 cm-1 in the argon ion laser Raman spectrum, is from 0.25 to 0.6, (Carbon material B) a graphitic particle where the interplanar spacing (d002) of 002 planes by the wide-angle X-ray diffraction method is 3.37 Å or less, Lc is 900 Å or more, the tap density is 0.8 g/cm3 or more, the Raman R value that is a ratio of the peak intensity near 1,360 cm-1 to the peak intensity near 1,580 cm-1 in the argon ion laser Raman spectrum, is from 0.2 to 0.5, and the average degree of circularity as determined by a flaw-type particle analyzer is 0.9 or more.