Silver Oxide Cathode Composition for End-of-Discharge Detection
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Solution Overview
Problem
Alkaline secondary batteries with silver oxide as a positive electrode material face challenges in detecting the end-of-discharge time due to voltage flatness issues and charge/discharge reversibility, making it difficult to determine the optimal replacement time before apparatus operation is stopped.
Innovation Solution
Incorporating a mixture of silver oxide and silver-bismuth complex oxide as the positive electrode active material, with specific charge and discharge conditions to achieve a discharge curve that includes a step between 70% and 90% depth of discharge, allowing for easier detection of the end-of-discharge time while maintaining voltage flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If silver oxide is used as the positive electrode active material to achieve constant discharge potential and flat discharge curve, then voltage flatness is improved, but it becomes difficult to detect the end-of-discharge time
Solution Approach 1:
The patent uses a composite positive electrode active material consisting of silver oxide and bismuth oxide. The silver oxide provides voltage flatness while the bismuth oxide component generates a detectable step change in the discharge curve near the end of discharge, enabling both voltage stability and discharge detection
2Difficulty of detecting and measuring
If bismuth oxide is added to silver oxide to create a step change in discharge voltage for end-of-discharge detection, then end-of-discharge detection is improved, but charge and discharge reversibility and voltage flatness deteriorate
Solution Approach 1:
The patent optimizes the composition parameters of the composite material, specifically controlling the ratio of silver oxide to bismuth oxide and the particle size distribution. By adjusting these parameters, the patent achieves a balance where the bismuth oxide provides detectable step changes without compromising the charge-discharge reversibility or voltage flatness
3Difficulty of detecting and measuring
If the discharge voltage drops rapidly to detect end of discharge, then end-of-discharge detection is improved, but the time window for detection becomes too short to know replacement time in good time
Solution Approach 1:
The patent creates an electrical equivalent of a 'color change' by generating a step change (inflection point) in the discharge voltage curve. This step change occurs as a distinct feature in the voltage profile, providing a clear electrical signal that indicates the end-of-discharge point, analogous to how a color change indicates an endpoint in chemical titration
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 solution provides alkaline secondary batteries with improved voltage flatness and easier detection of the end-of-discharge time, ensuring timely replacement and maintaining battery utility by balancing the ratio of silver-bismuth complex oxide to silver oxide for optimal performance.
Implementation Method 1
a positive electrode active material containing a mixture of a silver oxide and a silver-bismuth complex oxide... When the battery that is fully charged is discharged with a constant current until a battery voltage drops to 1.0 V
Implementation Method 2
an alkaline secondary battery includes a positive electrode containing a positive electrode active material, a negative electrode, a separator... an alkaline electrolyte solution
Data Source
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AI summary
An alkaline secondary battery disclosed in the present application includes a positive electrode containing a positive electrode active material, a negative electrode, and a separator. The positive electrode active material contains a mixture of a silver oxide and a silver-bismuth complex oxide. A discharge curve is obtained when the battery that is fully charged is discharged with a constant current until a battery voltage drops to 1.0 V. The battery voltage at a point on the discharge curve where x (%) of a total discharge capacity has been discharged from the battery since start of discharge is represented by Vx (V). The discharge curve satisfies V10 - V70 < 0.08, has a step in the range of 70 ≤ x ≤ 90, and shows that a size of the step represented by V70 - V90 is 0.04 or more and 0.15 or less.