Hybrid Carbon Negative Electrode for Low-Temperature Battery Rate
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in maintaining high input-output characteristics, especially at low temperatures, due to issues with cycle performance and safety related to dendrite formation and irreversible capacity when using traditional carbon materials as negative electrodes.
Innovation Solution
A carbon material composed of hybrid particles with graphite and carbon fine particles of specific size ranges, coated with amorphous carbon, is used as a negative electrode active material, enhancing Raman R(90/10) values and BET specific surface area to improve low-temperature performance and peel strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If graphite is used as negative electrode material, then cycle performance is superior and electrode expansion is small, but irreversible capacity is large and rate characteristics are inferior
Solution Approach 1:
The patent uses a composite carbon material consisting of graphite particles (3-50 μm) combined with carbon fine particles (0.003-0.5 μm) having low crystallinity. This composite structure combines the advantages of graphite (small expansion, good cycle performance) with the advantages of low-crystallinity carbon (fast Li-ion insertion/extraction, low irreversible capacity), thereby resolving the contradiction between cycle performance and rate characteristics.
2Device complexity
If traditional carbon materials are used as negative electrodes, then battery structure is simple, but input-output characteristics deteriorate at low temperatures
Solution Approach 1:
The patent applies local quality by creating a heterogeneous carbon material where different regions have different properties: graphite particles provide structural stability while dispersed carbon fine particles with low crystallinity provide fast ion transport pathways. This local differentiation of material properties enables good input-output characteristics at low temperatures without complicating the overall battery structure.
3Productivity
If carbon material with low crystallinity is added to graphite, then rate characteristics improve, but manufacturing complexity increases
Solution Approach 1:
The patent employs preliminary action by pre-synthesizing carbon fine particles with controlled low crystallinity and specific size distribution before combining them with graphite particles. This pre-preparation of materials with optimized properties simplifies the final composite material fabrication process, making it easier to manufacture while achieving improved rate characteristics.
Data Source
AI summary
An objet of the invention is to provide a non-aqueous electrolyte secondary battery superior in input-output characteristics even at a low temperature. To achieve the object, hybrid particles (carbon material) satisfying certain conditions, and composed of graphite particles and carbon particles with a primary particle size from 3 nm to 500 nm, preferably as well as amorphous carbon, are used as a negative electrode active material for a non-aqueous electrolyte secondary battery, so that the input-output characteristics of a non-aqueous electrolyte secondary battery at a low temperature can be improved remarkably.