Lithium-Sulfur Positive Electrode Composition for Polysulfide Suppression
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Solution Overview
Problem
Lithium-sulfur batteries face issues with sulfur molecules and intermediate products dissolving in the electrolyte, leading to self-discharge, deterioration, and reduced battery performance due to increased viscosity and irreversible capacity, which existing solutions like adding ZnO and Al2O3 do not adequately address.
Innovation Solution
Incorporating ceramic powder oxidized and reduced between 1.0V to 3.0V (vs. Li/Li+) into the positive electrode mixture layer to adsorb lithium polysulfide, improving lithium ion and electronic conductivity, and using a sulfur-carbon composite with specific mass ratios to enhance capacity retention and reduce polysulfide diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur and sulfur compounds are used in the positive electrode to achieve high energy density, then the battery capacity increases, but intermediate products dissolve in the electrolyte causing increased viscosity and reduced lithium ion conductivity
Solution Approach 1:
A ceramic powder additive is introduced as an intermediary substance in the positive electrode mixture. This additive adsorbs intermediate products (lithium polysulfides) to form a composite structure, preventing their dissolution into the electrolyte. The ceramic powder acts as a mediator between sulfur and the electrolyte, capturing harmful intermediates while allowing lithium ion transport to proceed efficiently.
Solution Approach 2:
The positive electrode uses a composite material system consisting of sulfur, ceramic powder additive, conductive carbon, and binder. This composite structure combines the high capacity of sulfur with the adsorption properties of ceramic powder, creating a multi-functional electrode material that simultaneously provides high capacity and suppresses intermediate product dissolution.
2Quantity of substance
If sulfur and sulfur compounds are used in the positive electrode to achieve high energy density, then the battery capacity increases, but intermediate products diffuse to the negative electrode causing redox shuttle effect and increasing irreversible capacity
Solution Approach 1:
The ceramic powder additive serves as an intermediary that traps intermediate products within the positive electrode structure. By adsorbing lithium polysulfides, it prevents their diffusion to the negative electrode, thereby eliminating the redox shuttle effect and reducing irreversible capacity loss.
Solution Approach 2:
The harmful intermediate products are extracted from the electrolyte phase by the ceramic powder additive and retained in the solid electrode structure. This extraction of intermediates from the liquid electrolyte prevents their harmful diffusion and redox reactions.
3Reliability
If ceramic powder additive is added to suppress intermediate product dissolution, then lithium ion conductivity is improved, but the device complexity increases
Solution Approach 1:
The invention optimizes the amount of ceramic powder additive to a specific range (1-20 wt% of total electrode mass) to achieve the desired balance between suppressing intermediate product dissolution and maintaining lithium ion conductivity. By controlling this parameter, the system achieves improved performance without excessive complexity.
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 effectively suppresses the dissolution of intermediate products, improves initial capacity and retention, and increases battery capacity by promoting reduction reactions and ion conductivity, while being simple to implement in the manufacturing process.
Implementation Method 1
the positive electrode mixture layer contains sulfur and/or a sulfur compound, a ceramic material oxidized and reduced in a potential range of 1.0V (vs. Li/Li+) to 3.0V (vs. Li/Li+), and a binder... capable of suppressing the dissolution of the intermediate products in an electrolyte by adsorbing the intermediate products into the additive
Implementation Method 2
a ceramic material oxidized and reduced in a potential range of 1.0V (vs. Li/Li+) to 3.0V (vs. Li/Li+)... improves lithium ion and electronic conductivity... by promoting reduction reactions and ion conductivity
Data Source
AI summary
The present disclosure provides a positive electrode which includes a positive electrode current collector and a positive electrode mixture layer, wherein the positive electrode mixture layer contains sulfur and/or a sulfur compound, a ceramic material that is oxidized and reduced in a potential range of 1.0V (vs. Li/Li+) to 3.0V (vs. Li/Li+), a binder, and a proportion of the sulfur and/or the sulfur compound in the positive electrode mixture layer is 40% by mass to 80% by mass.