Carbon-Coated Composite Electrode Material for High-Power Batteries
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Solution Overview
Problem
Existing composite electrode materials for lithium batteries face issues with impurities from steel balls during ball-milling, which lead to side reactions, and require additional carbon sources for conductivity, affecting battery performance.
Innovation Solution
A composite electrode material is developed using carbon-coated carbon fibers and complex oxide particles with a non-powdery carbon coating less than 100 nm thick, supported by vapor grown carbon fibers, which eliminates the need for additional carbon sources and enhances conductivity and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ball-milling is used to prepare composite electrode material, then mixing performance is improved, but steel ball impurities are introduced causing side reactions
Solution Approach 1:
The patent removes steel balls from the ball-milling process entirely and replaces them with ceramic balls (zirconia or alumina), thereby extracting the harmful impurity source while maintaining the beneficial mixing effect of mechanical ball-milling
Solution Approach 2:
The patent introduces ceramic balls as an intermediary material that performs the mechanical mixing function without introducing harmful impurities, serving as a mediator between the mixing requirement and the impurity-free constraint
2Quantity of substance
If additional carbon sources are added to achieve theoretical capacity, then capacity is improved, but conductivity and mechanical strength are compromised
Solution Approach 1:
The patent makes the complex oxide particles self-sufficient by coating them with a conductive carbonaceous layer that provides both the necessary conductivity and contributes to capacity, eliminating the need for additional carbon sources like carbon black
Solution Approach 2:
The patent creates a composite structure where complex oxide particles are coated with a carbonaceous material, forming a hybrid material that combines the high capacity of the oxide with the high conductivity of carbon, achieving both capacity and conductivity simultaneously
3Reliability
If carbon coating thickness is increased to improve conductivity, then conductivity is improved, but mechanical strength and adhesion deteriorate
Solution Approach 1:
The patent optimizes the carbon coating thickness parameter to a specific range (1-10 nm) that provides sufficient conductivity enhancement while maintaining strong adhesion and mechanical integrity, avoiding the detrimental effects of thicker coatings
Solution Approach 2:
The patent applies a thin carbonaceous coating only on the surface of complex oxide particles, providing local conductivity enhancement at the particle surface where it is most needed for electron transport, while preserving the bulk mechanical properties of the oxide particles
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 composite electrode material achieves high mechanical strength, improved conductivity, and increased capacity at high and low discharge rates, with reduced irreversible capacity loss and impedance, suitable for high-power applications.
Implementation Method 1
The chemical bonds provide excellent adhesion and high local conductivity
Implementation Method 2
the carbon fibers consist of fiber filaments having a diameter of 1 to 200 nm and an aspect ratio, length/diameter, of 20 to 2000
Data Source
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AI summary
The invention relates to a composite material comprising carbon fibers and complex oxide particles, wherein the carbon fibers and the complex oxide particles have a carbon coating on at least part of their surface, said carbon coating being a non powdery coating The material is prepared by a method comprising mixing a complex oxide or precursors thereof, an organic carbon precursor and carbon fibers, and subjecting the mixture to a heat treatment in an inert or reducing atmosphere for the decomposition of the precursors The material is useful as the cathode material in a battery