Sulfur Positive Electrode Composite for Lower Battery Internal Resistance
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Solution Overview
Problem
Existing secondary batteries face challenges in reducing internal resistance, particularly when using sulfur as a positive electrode material, which limits their charge-discharge rate characteristics and capacity utilization during rapid charging and discharging.
Innovation Solution
A positive electrode material is developed comprising a porous carbon material with sulfur and lithium halide placed inside its pores, creating an ion conduction path that enhances the movement of lithium ions and reduces internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If elemental sulfur is used as a positive electrode material, then the theoretical capacity is extremely large (about 1670 mAh/g), but the internal resistance is high making it difficult to secure sufficient charge and discharge capacity at practical current
Solution Approach 1:
The patent uses porous carbon material as the base structure of the positive electrode, providing a three-dimensional pore network that accommodates sulfur and lithium halide. The porous structure increases the surface area and provides multiple pathways for ion transport, reducing internal resistance while maintaining high theoretical capacity of sulfur.
Solution Approach 2:
The patent creates a composite material system consisting of sulfur, lithium halide, and porous carbon material. This composite structure combines the high capacity of sulfur with the conductive properties of carbon and the ion-conducting properties of lithium halide, achieving both high capacity and low internal resistance.
2Power
If sulfur is placed in mesopores of mesoporous carbon (as in JP 2010-95390 A), then electron conductivity is improved by particle size reduction and conjugation, but internal resistance cannot be sufficiently reduced for high charge-discharge rate characteristics
Solution Approach 1:
The patent introduces lithium halide as an intermediary substance between sulfur and the porous carbon structure. The lithium halide forms ion conduction paths that facilitate lithium ion transport, acting as a mediator that connects the electronic conductivity improvement (from sulfur-con carbon conjugation) with the ion conductivity needed for low internal resistance and high charge-discharge rates.
Solution Approach 2:
The patent changes the physical and chemical parameters of the electrode material by incorporating lithium halide, which alters the ion conduction properties. This parameter change enables sufficient reduction of internal resistance while maintaining the electron conductivity improvements achieved through sulfur particle size reduction and conjugation with mesoporous carbon.
3Speed
If a secondary battery is designed for rapid charging and discharging, then charge-discharge rate characteristics are required to be sufficient, but internal resistance prevents utilization of sufficient capacity during rapid charging and discharging
Solution Approach 1:
The porous carbon material structure provides a three-dimensional network of pores that facilitate rapid ion transport throughout the electrode. This porous architecture enables sufficient charge-discharge rate characteristics by providing multiple parallel pathways for lithium ion diffusion, overcoming the internal resistance limitation during rapid charging and discharging.
Solution Approach 2:
The composite material system of sulfur-lithium halide-porous carbon creates a synergistic structure where each component addresses different aspects of the charge-discharge process. The combination enables both high capacity utilization and sufficient charge-discharge rate characteristics by simultaneously improving electron conductivity, ion conductivity, and providing rapid transport pathways.
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 proposed electrode material significantly reduces internal resistance, allowing for improved charge-discharge rate characteristics and capacity utilization, making it suitable for high-performance secondary batteries.
Implementation Method 1
The solid electrolyte is a material mainly made of an ion conductor that enables ion conduction in a solid
Data Source
AI summary
A positive electrode material contains a porous carbon material, a positive electrode active material containing sulfur, and a lithium halide, wherein at least a part of the positive electrode active material and at least a part of the lithium halide are placed inside the pores of the porous carbon material. The positive electrode material provides a means for further reducing an internal resistance of a secondary battery.