Non-Electron-Conductive Intermediate Layer for Sodium-Sulfur Battery Safety
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Solution Overview
Problem
Sodium-sulfur batteries face issues with sulfur deposition on the cathode side during charging, leading to increased electrical resistance, premature polarization, and incomplete charging, as well as the risk of exothermic reactions and pressure buildup when the solid electrolyte breaks, causing damage and safety concerns.
Innovation Solution
Incorporating a non-electron-conductive intermediate layer with a thickness of 1.0 to 5 mm, impregnated with a polysulfide composition of alkali metal polysulfides, between the solid electrolyte and the porous solid electrode, which separates the cathode and anode compartments, preventing direct contact of molten sodium and sulfur and mitigating exothermic reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a porous solid electrode is placed directly adjacent to the solid electrolyte in contact with molten sulfur, then electrical conductivity and charging efficiency improve, but sulfur deposition on the cathode side increases electrical resistance and causes premature polarization
Solution Approach 1:
A non-electron-conductive intermediate layer is introduced between the porous solid electrode and the solid electrolyte. This intermediate layer prevents direct contact between sulfur and the electrode, eliminating sulfur deposition on the cathode side while maintaining ionic conductivity through the polysulfide composition it contains.
2Adaptability or versatility
If the solid electrolyte breaks during battery operation, then structural integrity is compromised, but direct contact between molten sodium and sulfur causes violent exothermic reactions and pressure buildup
Solution Approach 1:
The non-electron-conductive intermediate layer is pre-installed between the solid electrolyte and the porous solid electrode before operation. This layer acts as a safety buffer that prevents direct contact between molten sodium and sulfur even if the solid electrolyte breaks, avoiding violent exothermic reactions and pressure buildup.
3Reliability
If a non-electron-conductive intermediate layer is introduced between the solid electrolyte and porous solid electrode, then safety improves by preventing direct contact between molten sodium and sulfur, but internal resistance increases
Solution Approach 1:
The intermediate layer is impregnated with a polysulfide composition containing alkali metal polysulfides, which provides ionic conductivity pathways. This maintains low internal resistance for ion transport while the layer's non-electron-conductive nature preserves safety by preventing direct contact between molten sodium and sulfur.
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 solution reduces heat release and internal resistance, enhancing safety and maintaining battery performance even if the solid electrolyte is damaged, while preventing violent reactions and maintaining efficient energy storage and delivery.
Implementation Method 1
the risk of exothermic reactions and pressure buildup when the solid electrolyte breaks, causing damage and safety concerns
Implementation Method 2
a solid electrolyte separating the compartments
Implementation Method 3
Electrochemical devices having a compartment for molten cathode material, a compartment for molten anode material, a solid electrolyte separating the compartments
Data Source
Figure 1
AI summary
The invention relates to an electrode unit for an electrochemical device, comprising (i) a solid electrolyte, which separates a space for molten cathode material selected from the group consisting of elemental sulfur and polysulfide of the alkali metal anode material and a space for molten alkali metal anode material, and (ii) a porous solid electrode, which is located in the space for the cathode material directly adjacent to the solid electrolyte. Situated between the solid electrode and the solid electrolyte is a non-electron-conducting intermediate layer S, characterized in that prior to the first charging of the electrochemical device, said intermediate layer S is completely saturated with a polysulfide composition containing (A) clean polysulfide met <sb /> <sb /> where met = alkali metal of the alkali metal anode material selected from lithium, sodium, potassium, and x is a function of the alkali metal, and for Na = 2, 3, 4, or 5, and for Li = 2, 3, 4, 5, 6, 7, 8 and for K = 2, 3, 4, 5, 6, or (B) mixtures of the polysulphides of one and the same alkali metal from (A) between each other.