Lithium-Ion Electrode Composition for Capacity Retention
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Solution Overview
Problem
Existing electrodes for lithium-ion secondary batteries, particularly those using active materials like sulfur and iron compounds, face challenges in achieving high charge and discharge capacity and capacity retention rates due to material deterioration and structural issues during charge and discharge cycles.
Innovation Solution
The electrode comprises an active material layer with a particulate mixture of an organic sulfur compound and an iron compound, where the sulfur, iron, and median diameter satisfy the inequality A s × A F × M > 1600, optimizing the content ratios and particle size to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur and iron compounds are used as active materials to increase battery capacity, then charge and discharge capacity increases, but capacity retention rate deteriorates due to material deterioration during charge and discharge cycles
Solution Approach 1:
The invention optimizes the particle size parameter (median diameter ≥ 2 μm) and compositional parameters (sulfur content 60-80 wt%, iron compound content 5-20 wt%) of the active material to simultaneously achieve high charge and discharge capacity and high capacity retention rate, resolving the contradiction between capacity increase and capacity retention deterioration
Solution Approach 2:
The invention creates a composite active material consisting of sulfur compound, iron compound, and conductive carbon material in specific proportions, where the conductive carbon material forms a network structure that improves both capacity and capacity retention by enhancing electrical conductivity and structural stability during charge and discharge cycles
2Productivity
If smaller particle size active material is used to increase surface area for reactions, then charge and discharge rate improves, but capacity retention rate worsens due to increased material deterioration
Solution Approach 1:
The invention sets the median diameter of the active material to 2 μm or more, optimizing the particle size parameter to balance charge and discharge rate with capacity retention rate, preventing excessive material deterioration while maintaining adequate reaction surface area
3Quantity of substance
If higher sulfur content is used to increase capacity, then charge and discharge capacity increases, but structural stability worsens leading to lower capacity retention rate
Solution Approach 1:
The invention creates a composite structure where sulfur compound (60-80 wt%) provides high capacity while iron compound (5-20 wt%) and conductive carbon material provide structural stability and electrical conductivity, achieving both high capacity and high capacity retention rate through synergistic composition
Solution Approach 2:
The invention creates a local network structure of conductive carbon material throughout the active material composite, providing localized structural support and electrical conductivity pathways that maintain stability during charge and discharge cycles while preserving high sulfur content for capacity
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
This configuration results in improved charge and discharge capacity and capacity retention rates, with initial discharge capacities exceeding 400 mAh/g and 10th discharge capacities above 350 mAh/g, enhancing the overall performance of lithium-ion batteries.
Implementation Method 1
as negative electrode active materials, it has been proposed to use materials that can absorb and release more lithium ions
Implementation Method 2
the active material comprising an organic sulfur compound and an iron compound
Data Source
Figure 1
AI summary
Provided is an electrode for lithium-ion secondary battery, the electrode comprising an active material layer comprising a particulate active material, the active material comprising an organic sulfur compound and an iron compound, wherein As, AF, and M satisfy the following inequality (1) As×AF×M > 1600, where As represents a sulfur element content, in % by mass, in the active material, AF represents an iron element content, in % by mass, in the active material, and M represents a median diameter, in µm, of the active material. It is an object of the present invention to improve an overall performance of charge and discharge capacity and a capacity retention rate of a lithium-ion secondary battery.