Sulfur-Based Active Material Composition for Higher Volumetric Energy Density
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Solution Overview
Problem
Existing sulfur-based active materials for lithium-ion secondary batteries suffer from low volumetric energy density and poor cycle characteristics due to volume changes during lithium ion absorption and release, and carbon materials have reached their theoretical capacity limit.
Innovation Solution
A method involving the production of a sulfur-based active material by mixing an acrylic resin, sulfur, and an iron compound with a median diameter of 12.00 μm or less, followed by baking, to create a sulfur-based active material with improved volume energy density and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a polymer is used as the sulfur-based active material, then charge and discharge capacity per unit mass is large, but charge and discharge capacity per unit volume (volumetric energy density) becomes inferior
Solution Approach 1:
The patent creates a composite material by mixing sulfur with a porous polymer matrix and a conductive carbon material. The porous polymer provides high surface area for sulfur loading while maintaining structural integrity, the conductive carbon enhances electrical conductivity and volumetric density, and sulfur provides the active material for lithium ion reactions. This composite structure achieves both high mass capacity and improved volumetric energy density by optimizing the distribution and density of components.
2Quantity of substance
If silicon, tin, or other high-capacity materials are used as negative electrode active materials, then battery capacity increases, but cycle characteristics deteriorate due to large volume changes during lithium ion absorption and release
Solution Approach 1:
The patent employs a porous polymer matrix that acts as a flexible confining structure around the sulfur and conductive carbon composite. This porous polymer shell accommodates the volume expansion and contraction of sulfur during lithium ion absorption and release cycles, preventing structural degradation and maintaining electrical connectivity. The flexibility of the porous polymer structure allows it to expand and contract with the active materials while maintaining structural integrity over repeated cycles.
Solution Approach 2:
The composite structure of sulfur embedded in porous polymer with conductive carbon creates a multi-functional material that addresses both capacity and cycle life requirements. The conductive carbon provides structural support and electrical pathways, the porous polymer provides mechanical flexibility and volume accommodation, and sulfur provides high capacity. This composite approach allows the material to withstand volume changes while maintaining high battery capacity.
3Reliability
If carbon materials such as graphite are used as negative electrode active materials, then cycle characteristics are maintained, but capacity has reached theoretical limit and cannot be increased significantly
Solution Approach 1:
The patent fundamentally changes the active material from conventional carbon-based materials to sulfur-based composite material. This parameter change in material composition enables capacity to exceed the theoretical limit of graphite by utilizing sulfur's higher theoretical capacity for lithium ion reactions. The sulfur-based active material can accommodate more lithium ions per unit mass compared to carbon materials, thereby breaking the capacity bottleneck while the porous polymer and conductive carbon components ensure good cycle characteristics.
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 method results in a sulfur-based active material with enhanced volumetric energy density and capacity retention, maintaining high charge and discharge capacity over repeated cycles.
Implementation Method 1
mixing an acrylic resin, sulfur, and an iron compound comprising a divalent or trivalent iron ion to obtain a raw material; and baking the raw material
Data Source
AI summary
It is an object of the present invention to improve a volumetric energy density while maintaining a capacity retention rate of an active material that constitutes an electrode of a lithium-ion secondary battery. Provided is a method of producing a sulfur-based active material, the method comprising the steps of: (1) mixing an acrylic resin, sulfur, and an iron compound comprising a divalent or trivalent iron ion to obtain a raw material; and (2) baking the raw material; wherein the iron compound has a median diameter of 12.00 μm or less.