Subfluorinated Graphite Fluoride Electrodes for High-Rate Lithium Batteries
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Solution Overview
Problem
Fluorinated carbon materials used in lithium batteries suffer from low electrical conductivity, which limits their performance, especially at high discharge rates, despite their high thermal stability and discharge capacity.
Innovation Solution
The use of subfluorinated graphite fluorides with a fluorine content in the range of 0.06 to 0.63, combined with a conductive diluent and a binder, to create electrodes that enhance the electrical conductivity and performance of lithium batteries during high-rate discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly fluorinated graphite fluorides (CFx)n are used as electrode materials, then thermal stability and discharge capacity are improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fluorine content (x value) in graphite fluoride compounds to fall within the range of 0.25 < x ≤ 0.50. This specific compositional parameter optimization balances the competing requirements: sufficient fluorine content provides thermal stability and discharge capacity, while limiting excessive fluorine content preserves electrical conductivity. The patent demonstrates that this narrow compositional window resolves the contradiction between stability and conductivity.
Solution Approach 2:
The patent employs composite materials by combining graphite fluoride particles with conductive additives such as carbon black, acetylene black, or graphite powder in the electrode formulation. This composite approach allows the graphite fluoride to provide thermal stability and capacity while the conductive additives compensate for and enhance the electrical conductivity, thereby resolving the contradiction between these two properties.
2Quantity of substance
If highly fluorinated graphite fluorides (CFx)n are used as electrode materials, then discharge capacity is improved, but performance at high discharge rates deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the fluorine content (x value) within the specific range of 0.25 < x ≤ 0.50. This compositional optimization ensures sufficient discharge capacity while maintaining adequate electrical conductivity for high-rate performance. The patent further optimizes particle size parameters (1-10 microns) to enhance rate capability while preserving capacity.
Solution Approach 2:
The patent uses composite materials by formulating electrodes with graphite fluoride combined with conductive additives (carbon black, acetylene black, or graphite powder). This composite structure enables the electrode to achieve both high discharge capacity from the graphite fluoride and high rate performance from the conductive network provided by the additives.
3Temperature
If fluorine content in graphite fluoride is increased, then thermal stability is improved, but electrical conductivity decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fluorine content (x value) within the optimized range of 0.25 < x ≤ 0.50. This parameter optimization identifies the sweet spot where thermal stability is sufficiently high while electrical conductivity remains adequate. The patent demonstrates through experimentation that exceeding this fluorine content range causes conductivity to drop precipitously, so the parameter control resolves the contradiction.
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 subfluorinated graphite fluorides improve the battery's performance by increasing conductivity, allowing for higher discharge rates while maintaining the high thermal stability and discharge capacity of fluorinated carbon materials.
Implementation Method 1
electrochemical device that converts chemical energy to electrochemical current
Implementation Method 2
graphite has been known to react with elemental fluorine at high temperatures to yield graphite fluoride compounds
Data Source
AI summary
Subfluorinated graphite fluorides of formula CFx wherein CFx is in the range of 0.06 to 0.63, e.g., 0.10 to 0.46, are used as electrode materials in electrochemical devices that convert chemical energy to electrical current, e.g., batteries. The invention additionally provides methods of manufacturing electrodes with the subfluorinated graphite fluorides, as well as primary and secondary batteries containing such electrodes.