Mixed Carbon Negative Electrode for Rapid Charge-Discharge
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Solution Overview
Problem
Current negative electrode materials for 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.
Innovation Solution
A mixed carbon material comprising two types of carbon materials, Carbon Material A and Carbon Material B, where Carbon Material A has a multilayer structure with spheroidized graphitic particles and amorphous carbon coating, and Carbon Material B has high electron conductivity, both optimized for interplanar spacing, tap density, Raman R value, and specific surface area to enhance charge-discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous carbon particles are used to improve cycle characteristics, then cycle stability is improved, but irreversible capacity increases and rapid charge-discharge characteristics deteriorate
Solution Approach 1:
The invention uses a composite carbon material consisting of spheroidized graphitic carbon particles coated with amorphous carbon. The graphitic core provides high capacity and rapid charge-discharge characteristics, while the amorphous carbon coating improves cycle stability. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The invention applies different carbon material properties to different regions: the inner core uses spheroidized graphitic carbon for rapid charge-discharge performance, while the outer coating uses amorphous carbon for cycle stability. This local differentiation allows each region to optimize its function without compromising the other.
2Quantity of substance
If graphitic carbon materials are used to achieve high capacity and flat discharge potential, then capacity is improved, but rapid charge-discharge characteristics and cycle characteristics deteriorate
Solution Approach 1:
The invention creates a composite structure where spheroidized graphitic carbon particles serve as the core to maintain high capacity, while amorphous carbon coating is applied to the surface to enable rapid charge-discharge characteristics. This composite approach allows simultaneous achievement of high capacity and rapid response.
Solution Approach 2:
The invention changes the physical and chemical parameters of the carbon material surface by coating with amorphous carbon. This surface modification alters the electrochemical properties, enabling faster lithium ion insertion/extraction kinetics while maintaining the high capacity of the graphitic core.
3Productivity
If mechanical energy treatment is applied to spheroidize graphitic particles to improve rapid charge-discharge characteristics, then rapid charge-discharge properties are improved, but particle structure damage increases
Solution Approach 1:
The invention applies amorphous carbon coating to the spheroidized graphitic particles as a protective layer. This coating cushions and protects the underlying graphitic structure from further damage, maintaining particle integrity while preserving the rapid charge-discharge characteristics achieved through spheroidization.
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 eaxbon 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 0.11 to 0.2.