Primary Lithium Battery Electrolyte Sizing for Cathode Void Volume
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Solution Overview
Problem
Primary lithium batteries, such as Li/FeS2 cells, experience a decrease in cathode volume during discharge, leading to increased void volume and suboptimal performance due to insufficient electrolyte volume to fill cathode pores and maintain ion transport.
Innovation Solution
Increasing the volume of electrolyte in the battery to greater than the sum of the total pore volume and the void volume created during discharge, ensuring full contact between the electrolyte and the active cathode surface and maintaining Li ion transport throughout the discharge process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the battery uses a minimal volume of electrolyte to fill pores in cathode and separator, then the battery structure is compact and manufacturing is simplified, but the battery performance degrades due to insufficient electrolyte to maintain ion transport during discharge
Solution Approach 1:
The patent calculates the void volume that will be generated during discharge in advance and adds this volume to the total pore volume to determine the required electrolyte volume before battery assembly. This preliminary calculation ensures that sufficient electrolyte is present from the start to maintain ion transport throughout the entire discharge process, preventing performance degradation.
Solution Approach 2:
The patent changes the electrolyte volume parameter from a minimal pore-filling amount to a calculated amount that compensates for discharge-induced volume changes. By adjusting this critical parameter based on electrochemical reaction stoichiometry and density changes, the battery maintains optimal ion transport conditions throughout discharge.
2Duration of action of moving object
If the cathode volume decreases during discharge due to electrochemical reactions, then the electrochemical reaction progresses, but the void volume increases creating insufficient electrolyte contact with active cathode surface
Solution Approach 1:
The patent provides a cushioning volume of electrolyte in advance that compensates for the void volume created during cathode volume decrease. This excess electrolyte volume acts as a buffer that maintains continuous contact with the active cathode surface throughout discharge, ensuring reliable ion transport even as the cathode structure changes during electrochemical reaction.
3Ease of manufacture
If the battery is designed as a primary battery with simple structure, then manufacturing is easier and cost is lower, but the battery cannot accommodate volume changes during discharge without performance loss
Solution Approach 1:
The patent achieves improved performance in simple primary batteries by changing the electrolyte volume parameter to a specifically calculated value that accounts for discharge-induced void volume. This single parameter adjustment allows the simple primary battery structure to accommodate volume changes without requiring complex multi-layer separators or robust design features.
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 approach enhances battery performance by ensuring adequate electrolyte volume to compensate for the increase in void volume during discharge, thereby maintaining ion transport and overall cell performance.
Implementation Method 1
An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge
Implementation Method 2
the respective oxidation and reduction reactions to occur to provide electrical power
Implementation Method 3
as a primary lithium battery including, for example, FeS2 as the cathode active material, discharges, the resulting products of the battery can occupy less volume compared to the initial reagents
Data Source
AI summary
A battery includes a housing, and within the housing, an anode having an alkali metal as the active material, a cathode having a mass (m) of a cathode active material, for example, iron disulfide as the active material, a separator between the anode and the cathode, and an increased electrolyte volume (v).