Sulfur Cathode Material Using Expandable Polymer Particles
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries face challenges in achieving low-cost production, improving cycle characteristics, and enhancing charge/discharge capacity, particularly due to the high cost of polyacrylonitrile, insufficient cycle characteristics of industrial rubber-based cathode materials, and poor volume stability of anode materials like silicon and tin.
Innovation Solution
A sulfur-based active material is developed by calcinating a raw material comprising heat-expandable particles with an acryl-based copolymer outer shell and a hydrocarbon inside, along with sulfur, at a temperature of 250 to 550°C. This process ensures a good dispersion of sulfur and uniform contact with the outer shell, leading to improved charge/discharge capacity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polyacrylonitrile is used as a raw material for cathode active material, then charge/discharge capacity is improved, but manufacturing cost increases significantly
Solution Approach 1:
The invention changes the chemical composition parameters of the polymer raw material from polyacrylonitrile to acryl-based copolymers (acrylonitrile-acrylic acid copolymer, acrylonitrile-methacrylic acid copolymer, or acrylonitrile-acrylic acid-methacrylic acid terpolymer). This parameter change maintains the charge/discharge capacity while significantly reducing raw material cost, as these copolymer materials are more readily available and less expensive than high-quality polyacrylonitrile.
2Ease of manufacture
If industrial rubber is used to reduce cathode active material cost, then manufacturing cost decreases, but cycle characteristics are insufficient
Solution Approach 1:
The invention uses composite materials consisting of specific acryl-based copolymers combined with sulfur in controlled ratios. The copolymer composition (acrylonitrile with acrylic acid or methacrylic acid) creates a composite structure that provides both cost-effectiveness and excellent cycle characteristics, overcoming the limitations of industrial rubber while maintaining low manufacturing cost.
Solution Approach 2:
The invention specifies precise compositional parameters for the acryl-based copolymer (acrylonitrile content, presence of acrylic acid or methacrylic acid) and controls the sulfur content ratio. These parameter changes ensure optimal cycle characteristics while maintaining cost-effectiveness, distinguishing the invention from generic industrial rubber applications.
3Quantity of substance
If silicon or tin is used as anode active material to increase battery capacity, then charge/discharge capacity is improved, but cycle characteristics deteriorate due to large volume change
Solution Approach 1:
The invention creates composite materials by combining high-capacity anode materials (silicon or tin) with carbon materials in specific ratios and structures. This composite structure accommodates the volume expansion and contraction during lithium ion occlusion and release, preventing particle disintegration and maintaining electrical conductivity, thus preserving cycle characteristics while achieving high battery capacity.
Solution Approach 2:
The invention employs carbon material coatings or composite structures that act as flexible shells around silicon or tin particles. These carbon shells provide mechanical flexibility to accommodate volume changes during cycling, preventing structural failure and maintaining electrochemical performance over repeated charge/discharge cycles.
4Reliability
If carbon materials like graphite or hard carbon are used for anode, then stability is improved, but theoretical capacity is almost reached and significant capacity improvement cannot be expected
Solution Approach 1:
The invention develops composite anode materials combining carbon materials (graphite, hard carbon) with high-capacity materials (silicon, tin, or their alloys). This composite structure allows the carbon component to provide stability and structural integrity while the silicon or tin component contributes additional lithium ion capacity, achieving both stability and enhanced theoretical capacity that exceeds what carbon materials alone can provide.
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 sulfur-based active material achieves a large charge/discharge capacity and excellent cycle characteristics, making it suitable for non-aqueous electrolyte secondary batteries while being produced inexpensively and efficiently.
Implementation Method 1
a heat-expandable particle comprising an outer shell comprising an acryl-based copolymer and a hydrocarbon included inside the outer shell, the heat-expandable particle having an expansion starting temperature of 150° C. or lower
Implementation Method 2
calcinating a raw material comprising (1) a heat-expandable particle comprising an outer shell comprising an acryl-based copolymer and a hydrocarbon included inside the outer shell, the heat-expandable particle having an expansion starting temperature of 150° C. or lower, and (2) sulfur
Data Source
AI summary
Provided is a sulfur-based active material for a non-aqueous electrolyte secondary battery having a large charge/discharge capacity and excellent cycle characteristics which is inexpensively and easily provided, an electrode comprising the sulfur-based active material, and a non-aqueous electrolyte secondary battery comprising the electrode, as well as a producing method thereof. The sulfur-based active material is obtainable by calcinating a raw material, the raw material comprising (1) a heat-expandable particle comprising an outer shell comprising an acryl-based copolymer and a hydrocarbon included inside the outer shell, the heat-expandable particle having an expansion starting temperature of 150° C. or lower, and (2) sulfur.