Surface-Modified Graphite Additives for Low Oxidability Electrodes
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Solution Overview
Problem
Graphite materials used as conductive additives in batteries and fuel cells face limitations due to their limited stability in oxidative environments, leading to increased electrical resistance and potential hazardous degradation, necessitating a balance between low oxidability and low electrical resistance.
Innovation Solution
The development of graphite materials with specific properties, including a pH of at least 5.4, Scott density less than or equal to 0.11 g/cm³, and a Raman D/G intensity ratio of 0.220 to 0.420, achieved through a surface modification process involving heating in the presence of oxidizing process gases, which enhances their oxidability and electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite materials are used as conductive additives in batteries and fuel cells, then electrical conductivity is improved, but oxidability increases leading to degradation and hazardous gas evolution
Solution Approach 1:
The patent applies parameter changes by controlling the oxidation process through specific parameters including temperature ranges (400-1000°C), oxidation time (1-48 hours), and oxidation atmosphere composition to achieve the desired balance between conductivity and oxidability. This transforms the graphite surface properties to reduce harmful oxidation while preserving electrical conductivity.
Solution Approach 2:
The patent uses controlled oxidation with various oxidizing atmospheres (air, oxygen, steam, carbon dioxide) to deliberately modify the graphite surface. This accelerated oxidation process creates a surface layer that protects against further oxidation during battery operation, thereby reducing the harmful oxidability effect while maintaining the beneficial electrical conductivity.
2Reliability
If graphite materials are used as conductive additives, then electrical resistance is decreased, but stability in oxidative environments deteriorates
Solution Approach 1:
The patent applies preliminary action by performing surface oxidation treatment on the graphite particles before they are incorporated into the battery electrodes. This pre-treatment creates a stable surface layer that prevents further oxidation during battery operation, thereby ensuring both low electrical resistance and high stability in oxidative environments throughout the battery's service life.
Solution Approach 2:
The patent creates a composite structure on the graphite surface through controlled oxidation, forming a surface layer with different properties than the bulk graphite. This composite structure combines the electrical conductivity of graphite with the oxidation resistance of the oxidized surface layer, achieving both low electrical resistance and high stability simultaneously.
3Productivity
If graphite materials are used as conductive additives, then battery performance is improved, but hazardous degradation and gas evolution occur
Solution Approach 1:
The patent converts the potentially harmful oxidation of graphite into a beneficial protective mechanism. By deliberately oxidizing the graphite surface under controlled conditions, a stable surface layer is formed that prevents further oxidation and degradation during battery operation. This transforms what would normally be a harmful process (oxidation leading to degradation) into a beneficial protective effect that enhances battery safety and performance.
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
These graphite materials exhibit improved stability and conductivity, extending the life of batteries and fuel cells, reducing the risk of decomposition, and allowing for higher cell capacity by minimizing the use of conductive additives.
Implementation Method 1
a graphite starting material is subjected to a surface modification process comprising heating to a temperature in the range of 300 to 1700°C in the presence of an oxidizing process gas
Implementation Method 2
heating to a temperature in the range of 300 to 1700°C in the presence of an oxidizing process gas such as but not limited to oxygen, air, oxygen enriched air, carbon dioxide, ozone, steam, NOx
Data Source
AI summary
The present invention is directed to graphite materials having a pH of at least 5.4, a Scott density of less than or equal to 0.11 g/cm3, and a Raman D/G intensity ratio of 0.220 to 0.420. The present invention further relates to applications of these graphite materials as well as processes for their production. In particular, the graphite materials of the present invention allow for an advantageous balance of low oxidability and low electrical resistance. This combination of properties is particularly advantageous when using the graphite materials as conductive additives in electrodes.