Sulfur Negative Electrode Battery Polymer Gel Layer
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Solution Overview
Problem
Lithium-ion secondary batteries using sulfur as a positive-electrode active material face capacity deterioration due to lithium polysulfide elution into the electrolyte, leading to reduced charging and discharging capacity over repeated cycles, and require pre-doping treatments to manage lithium insertion.
Innovation Solution
A metal-ion secondary battery design featuring a sulfur-based negative-electrode active material and a polymer gel layer on the positive electrode, utilizing a lithium transition metal oxide as the positive-electrode active material, which prevents reaction between eluted polysulfides and the positive electrode, eliminating the need for pre-doping treatments and enhancing cyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfur is used as a positive-electrode active material to achieve large capacity, then charging and discharging capacity increases, but battery capacity deteriorates through repeated charging and discharging due to lithium polysulfide elution
Solution Approach 1:
A polymer gel layer is introduced as an intermediary between the sulfur-based positive electrode and the electrolyte. This gel layer prevents lithium polysulfides from eluting into the electrolyte while still allowing lithium ion transport, thereby maintaining high capacity while preventing capacity deterioration through repeated cycles
Solution Approach 2:
A thin polymer gel coating is applied to the positive electrode surface. This flexible film structure physically confines the lithium polysulfides at the electrode-gel interface, preventing their dissolution into the bulk electrolyte and subsequent oxidation reactions that cause capacity fade
2Ease of manufacture
If sulfur-based active material is used for negative electrode to avoid pre-doping treatment, then manufacturing complexity reduces, but side reactions occur under oxidizing atmosphere causing battery deterioration
Solution Approach 1:
The polymer gel layer creates a protective environment around the sulfur-based negative electrode, isolating it from the oxidizing atmosphere in the electrolyte. This prevents harmful oxidation reactions while allowing the battery to operate without pre-doping treatments
Solution Approach 2:
The polymer gel acts as a protective intermediary between the sulfur-based negative electrode and the oxidizing electrolyte environment, enabling direct use of sulfur without pre-doping while preventing deterioration from side reactions
3Ease of operation
If lithium transition metal oxide is used as positive electrode to ensure lithium source, then lithium insertion is simplified, but reaction between eluted polysulfide and positive electrode occurs under oxidizing atmosphere
Solution Approach 1:
A polymer gel thin film is coated on the lithium transition metal oxide positive electrode surface. This film physically blocks eluted polysulfides from contacting and oxidizing the positive electrode materials, eliminating the harmful reaction while maintaining ease of lithium insertion
Solution Approach 2:
The polymer gel layer, which might seem to add complexity, actually converts a harmful situation (polysulfide elution leading to oxidation) into a beneficial configuration where the gel confines polysulfides at the electrode interface, preventing their harmful oxidation reactions
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 battery exhibits improved cyclability with reduced capacity loss over repeated charging and discharging cycles, maintaining a higher capacity retention rate and preventing polysulfide oxidation, thus extending the battery's lifespan.
Implementation Method 1
the positive electrode has a polymer gel layer on a surface of the positive electrode
Implementation Method 2
prevents reaction between eluted polysulfides and the positive electrode
Implementation Method 3
a negative electrode comprising a sulfur-based negative-electrode active material
Implementation Method 4
the generated sulfide is soluble into a nonaqueous electrolyte (for example, ethylene carbonate and dimethyl carbonate and the like) of the lithium-ion secondary battery
Data Source
AI summary
An object of the present disclosure is to provide a secondary battery having excellent cyclability by using a sulfur-based active material as a negative-electrode active material while preventing a reaction between an eluted polysulfide and a positive electrode. The metal-ion secondary battery comprises a negative electrode comprising a sulfur-containing compound as a negative-electrode active material, a positive electrode and an electrolyte, and has a polymer gel layer on a surface of the positive electrode.