Coconut Shell Hard Carbon Anode for Li-Ion Capacitors
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Solution Overview
Problem
Lithium ion capacitors require anode materials with high discharge capacity and superior rate performance to enhance energy and power density, which is not adequately met by existing carbon materials like graphite and phenolic resin-based carbons, especially at high charge-discharge rates.
Innovation Solution
The use of coconut shell-derived hard carbon with specific carbonization temperatures (1200°C, 1400°C, and 1600°C) and subsequent treatments, such as HCl washing and re-heating, to produce a carbon composition with low surface area and optimized structural properties for improved lithium ion intercalation and de-intercalation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional carbon materials like graphite and phenolic resin-based carbons are used in anodes, then the structure is stable, but the discharge capacity and rate performance are insufficient at high charge-discharge rates
Solution Approach 1:
The patent applies parameter changes by optimizing the carbonization temperature (1200-1600°C) and performing subsequent chemical treatments (HCl washing) and thermal re-heating to transform the carbon structure. These parameter modifications convert traditional carbon materials into hard carbon with enhanced properties, achieving both high discharge capacity and superior rate performance without sacrificing structural stability.
Solution Approach 2:
The patent creates a composite hard carbon material from coconut shell through multi-step processing including carbonization, acid treatment, and re-heating. This composite structure combines the advantages of natural carbon sources with controlled structural features, resulting in an anode material that simultaneously achieves high discharge capacity and excellent rate performance.
2Productivity
If carbonization temperature is increased to 1200°C, 1400°C, or 1600°C, then the discharge capacity improves, but the energy consumption and processing complexity increase
Solution Approach 1:
The patent applies preliminary action by performing HCl washing and drying before the final high-temperature carbonization step. This pre-treatment removes impurities and prepares the coconut shell structure, allowing the subsequent high-temperature processing to be more efficient and effective in producing hard carbon with superior discharge capacity.
Solution Approach 2:
The patent utilizes the coconut shell's natural structure and composition as a self-service precursor that, when subjected to controlled thermal and chemical treatments, automatically transforms into hard carbon with the desired properties. The natural lignocellulosic structure provides a template that guides the formation of the hard carbon morphology during carbonization.
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 coconut shell-derived carbon exhibits significantly higher discharge capacities and superior rate performance compared to traditional materials, leading to enhanced energy and power density in lithium ion capacitors, particularly at high charge-discharge rates.
Implementation Method 1
The use of coconut shell-derived hard carbon with specific carbonization temperatures (1200°C, 1400°C, and 1600°C)
Implementation Method 2
optimized structural properties for improved lithium ion intercalation and de-intercalation rates
Data Source
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AI summary
An anode in a lithium ion capacitor, including: • a carbon composition comprising: a coconut shell sourced carbon in from 85 to 95 wt%; a conductive carbon in from 1 to 10 wt%; and a binder in from 3 to 8 wt%; and • an electrically conductive substrate, The invention being based on the high temperature of carbonization of the coconut shell, between 1000 and 1600°C. Further, for low temperature the carbon can be washed with HCI. The carbon obtained shows more amorphous carbon than cristalline carbon.