Graphite Anode Material Coating for Fast Charge and Low Expansion
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Solution Overview
Problem
Existing negative electrode materials for nonaqueous secondary batteries face issues with high-temperature storage characteristics, rapid charge-discharge characteristics, electrode expansion, and density limitations, which affect battery capacity and performance.
Innovation Solution
A negative electrode material comprising graphite with controlled amorphous carbon coating, specific thermal properties, and pore volumes, along with controlled mercury intrusion and pore distribution, to enhance charge-discharge characteristics, reduce electrode expansion, and allow high-density pressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous carbon is coated on graphite particles to improve stability with electrolyte solutions, then excellent stability with electrolyte solutions is achieved, but high-temperature storage characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a layered coating structure where amorphous carbon provides electrolyte stability at the surface while the underlying graphite maintains thermal stability. The specific surface area control (0.03-0.20 m²/g) ensures that the amorphous carbon coating is present but limited in quantity, providing local protection without dominating the thermal properties of the entire particle.
Solution Approach 2:
The patent uses composite materials by combining graphite particles with amorphous carbon coating to achieve a material that exhibits both the electrolyte stability of amorphous carbon and the thermal stability of graphite. This composite structure allows the material to benefit from both components' advantages while mitigating their individual drawbacks.
2Speed
If amorphous carbon coating is increased to improve rapid charge characteristics, then rapid charge characteristics are improved, but electrode expansion increases
Solution Approach 1:
The patent applies partial action by using a controlled, limited amount of amorphous carbon coating rather than excessive coating. The specific surface area is restricted to 0.03-0.20 m²/g, which is enough to provide rapid charge characteristics through improved surface reactivity but insufficient to cause excessive electrode expansion that would result from thick amorphous carbon layers.
3Quantity of substance
If density of negative electrode material is increased to improve battery capacity, then high capacity is achieved, but press load required increases
Solution Approach 1:
The patent changes the physical parameters of the negative electrode material by controlling the specific surface area (0.03-0.20 m²/g) and using graphite particles with controlled pore structures. These parameter changes allow the material to achieve high density and high capacity while maintaining favorable pressability, reducing the press load required during electrode manufacturing.
Data Source
AI summary
A negative electrode material for a nonaqueous secondary battery which contains a graphite that contains an amorphous carbonaceous material in at least a part of the surface; has a cumulative pore volume of 0.100 mL/g or less in a pore size range of 0.01 μm to 1 μm; and satisfies at least one of the following conditions (1) and (2) in a DTA curve obtained by differential thermal analysis (DTA) in an air stream: (1) the negative electrode material has no exothermic peak in a temperature range of 550° C. to 650° C.; and (2) the negative electrode material has an exothermic peak in a temperature range of 550° C. to 650° C., and the area of the exothermic peak is larger than 0 μV·s/mg but 90 μV·s/mg or smaller; a negative electrode for a nonaqueous secondary battery, which contains the same; and a nonaqueous secondary battery are provided.