Silver Sulfide Cathode Coating for Longer-Life Silver-Oxide Batteries
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Solution Overview
Problem
Silver-oxide batteries suffer from poor cyclability and shelf life due to the instability of the silver-oxide cathode, which leads to the generation of mobile silver species that react with the battery separator, limiting the long-term cycle life and making it challenging to maintain a stable supply chain for battery-grade cellophane.
Innovation Solution
A porous substrate comprising silver and optionally silver oxide is coated with a silver sulfide layer, which is formed by submerging the substrate in a solution of elemental sulfur in dimethyl sulfoxide, thereby protecting the silver electrode from chemical and electrochemical degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional three-layer separator system is used in silver-oxide batteries, then the battery can function adequately as a primary battery, but the ultimate degradation of the cellophane layer limits the long-term cycle life of rechargeable silver-oxide batteries
Solution Approach 1:
The patent removes the cellophane middle layer from the traditional three-layer separator system. By extracting this problematic layer that degrades over time, the battery achieves improved long-term cycle life and shelf life without compromising its ability to function as a primary battery, using only the nylon and polypropylene layers
Solution Approach 2:
The patent applies a protective coating to the silver oxide cathode before battery assembly to prevent silver species migration in advance. This preliminary protective action eliminates the need for the cellophane layer to react with labile silver species, thereby removing the degradation mechanism that limited cycle life
2Device complexity
If the silver oxide cathode is used without protective coating, then the battery structure is simpler, but spontaneous and electrochemical degradation of the silver oxide generates mobile silver species that react with the battery separator
Solution Approach 1:
The patent creates a composite structure by coating the silver oxide cathode with a protective layer that combines the electrochemical activity of silver oxide with the stability of the coating material. This composite approach maintains the simplicity of the separator structure while preventing silver species migration and improving overall battery stability
Solution Approach 2:
The protective coating acts as an intermediary layer between the silver oxide cathode and the separator. It mediates the interaction by preventing direct contact between mobile silver species and the separator, thereby eliminating harmful reactions while maintaining the simple two-layer separator structure
3Reliability
If battery-grade cellophane is used to react with labile silver species, then the separator system functions adequately, but the supply chain becomes tenuous and endangers the long-term prospects to manufacture high-performance silver-oxide batteries
Solution Approach 1:
The patent extracts and eliminates the cellophane layer from the separator system, thereby removing the supply chain dependency for battery-grade cellophane. The remaining nylon and polypropylene layers provide adequate separator function without requiring the problematic middle layer
Solution Approach 2:
The protective coating on the cathode performs the function previously assigned to the cellophane layer (reacting with labile silver species), allowing the system to eliminate the physical cellophane separator layer entirely and its associated supply chain issues
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 silver sulfide coating significantly enhances the electrochemical performance and stability of the silver electrodes, reducing silver dissolution and eliminating the need for a cellophane separator, thus improving the cycle life and stability of silver-oxide batteries.
Implementation Method 1
a silver sulfide coating on at least a portion of the porous substrate
Implementation Method 2
submerging a substrate comprising silver and optionally silver oxide in the solution to form silver sulfide on the surface of the substrate
Data Source
AI summary
Disclosed herein is a porous substrate having silver and optionally silver oxide and a silver sulfide coating. Also disclosed herein is a battery having a cathode, an anode, and a separator between the cathode and the anode. The cathode includes a substrate having silver and optionally silver oxide and a silver sulfide coating. Also disclosed herein is a method of submerging a substrate having silver and optionally silver oxide in a solution of elemental sulfur in dimethyl sulfoxide to form silver sulfide on the surface of the substrate.