Composite Active Material Graphene Network for Battery Safety
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Solution Overview
Problem
Lithium-ion secondary batteries using carbon-based materials face issues with rapid charge and discharge due to dendrite formation, leading to internal short circuits and low energy density when using titanium-based materials, which require additional conductivity enhancers like Ketjen black or graphene, but these solutions often reduce capacity and stability.
Innovation Solution
A composite incorporating titanium composite oxide particles with a graphene structure where the graphene surface is slanted relative to the active material particle surface, forming a strong conductive network and enhancing stability, allowing for high current operation and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon-based materials are used in the negative electrode to achieve high capacity, then the theoretical capacity reaches 372 mAh/g, but dendrite precipitation occurs during rapid charge and discharge, causing internal short circuits and safety issues
Solution Approach 1:
A lithium phosphate coating layer is applied to the surface of the graphite particles, serving as an intermediary barrier that prevents direct contact between lithium ions and the graphite surface during rapid charge/discharge, thereby suppressing dendrite formation while maintaining high capacity
Solution Approach 2:
The negative electrode uses a composite structure combining graphite particles with a lithium phosphate coating layer, integrating the high capacity of graphite with the protective properties of the phosphate layer to achieve both high performance and safety
2Reliability
If titanium oxide is used as the negative electrode active material to prevent dendrite formation, then battery safety and stability improve, but the energy density decreases due to lower capacity per weight
Solution Approach 1:
The negative electrode employs a composite structure combining graphite particles with a lithium phosphate coating layer, integrating the high capacity of graphite with the protective properties of the phosphate layer to achieve both high performance and safety
3Power
If a large amount of Ketjen black is added to titanium-niobium composite oxide to provide sufficient conductivity, then the conductivity increases, but the capacity is reduced and the oxide becomes destabilized
Solution Approach 1:
The invention changes the physical form of the conductive additive from bulk carbon black particles to graphene sheets with two-dimensional structure, which provides superior conductivity per unit mass and allows much smaller amounts to be used without compromising electrical performance
Solution Approach 2:
The invention uses graphene, a two-dimensional material with exceptional electrical conductivity, as a more efficient alternative to conventional three-dimensional carbon black, achieving the same or better conductivity enhancement with significantly reduced loading amounts
4Power
If a large amount of sucrose is used to increase conductivity of titanium-niobium composite oxide, then the conductivity improves, but the oxide is reduced and capacity is easily reduced
Solution Approach 1:
The invention changes the chemical nature of the conductive additive from organic sucrose (which can be reduced) to inorganic graphene (which is chemically stable), eliminating the reduction issue while maintaining conductivity enhancement
Solution Approach 2:
The invention replaces sucrose, an organic substance with limited stability, with graphene, a highly stable carbon allotrope that maintains its properties over long periods and under various electrochemical conditions
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 achieves excellent conductivity and stability, enabling lithium-ion batteries to operate at high currents with improved capacity retention and reduced risk of dendrite formation, outperforming batteries using Ketjen black or other conductivity enhancers.
Implementation Method 1
The graphene structure has at least one side surface in contact with the active material particle. The side surface includes a carbon material whose graphene surface is slanted relative to the side surface
Data Source
AI summary
According to one embodiment, there is provided a composite. The composite includes active material particles of a titanium composite oxide or oxide of titanium, and a graphene structure including a carbon material. The carbon material has a graphene framework defining a graphene surface. The graphene structure is located in between the active material particles. The graphene structure has at least one side surface in contact with the active material particle. The side surface includes the carbon material whose graphene surface is slanted relative to the side surface.