Cellulose-Nanofiber Carbon Cathode Material for Faster Charge-Discharge
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Solution Overview
Problem
Current methods for enhancing lithium-ion and sodium-ion secondary cell performance, such as those using carbon nanostructures or cellulose fibers, face challenges in achieving high charge/discharge characteristics without requiring specialized equipment or compromising on carbon content, leading to trade-offs between rate characteristics and electric capacitance.
Innovation Solution
A positive-electrode active material comprising specific oxides, like lithium or sodium olivine-type metal phosphates or silicates, with carbon derived from cellulose nanofibers supported on their surface, manufactured through a hydrothermal reaction and pyrolysis process, to enhance charge/discharge capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon is coated onto the surface of positive electrode active material particles, then conductivity is improved, but the amount of lithium atoms passing through the carbon film is limited, worsening charge/discharge characteristics
Solution Approach 1:
The invention applies different carbon structures to different locations: amorphous carbon is deposited on the particle surface to maintain conductivity, while carbon nanotubes are grown at specific sites to provide high-speed lithium ion transport pathways, thus resolving the contradiction between conductivity and charge/discharge characteristics
Solution Approach 2:
The invention creates a composite carbon structure combining amorphous carbon and carbon nanotubes on the particle surface, where each component serves a different function: amorphous carbon for conductivity and carbon nanotubes for rapid lithium ion diffusion, thereby achieving both improved conductivity and enhanced charge/discharge characteristics
2Productivity
If plasma decomposition method is used to coat carbon nanostructure, then charge/discharge characteristics are enhanced, but special equipment and technology are required, increasing device complexity
Solution Approach 1:
The invention uses a slurry composition containing cellulose fiber as a carbon source that can be applied using conventional electrode manufacturing equipment. The cellulose fiber is converted to carbon through standard drying and heat treatment processes, eliminating the need for specialized plasma decomposition equipment while still achieving carbon nanostructure formation that enhances charge/discharge characteristics
3Productivity
If more carbon source is supported to enhance rate characteristics, then charge/discharge performance is improved, but the ratio of electrode active material reduces, worsening electric capacitance
Solution Approach 1:
The invention utilizes the porous structure of carbon nanotubes to provide high surface area for lithium ion adsorption and transport. This allows a small amount of carbon material to deliver significant rate enhancement without occupying excessive space that would displace active material, thus improving rate characteristics while maintaining electric capacitance
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 approach allows for improved charge/discharge characteristics in lithium-ion and sodium-ion secondary cells while reducing the amount of carbon needed, maintaining high performance and avoiding the need for complex equipment or processes.
Implementation Method 1
manufactured through a hydrothermal reaction and pyrolysis process
Implementation Method 2
manufactured through a hydrothermal reaction and pyrolysis process
Data Source
AI summary
The present invention provides a positive-electrode active material for a lithium-ion secondary cell or a sodium-ion secondary cell, which can effectively exhibit more excellent charge/discharge characteristics; and a method for manufacturing the positive-electrode active material. Namely, the present invention relates to a positive-electrode active material for a secondary cell comprising an oxide represented by formula (A): LiFeaMnbMcPO4, formula (B): LiFeaMnbMcSiO4, or formula (C): NaFegMnhQiPO4; and carbon derived from a cellulose nanofiber supported thereon.