Discharge Conditioning for Lithium Deposition Control
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Solution Overview
Problem
High rate discharge during the manufacturing of lithium batteries for implantable medical devices leads to increased lithium deposition, which can cause short circuits and premature depletion, due to the high load current required for quick discharge, affecting both performance and safety.
Innovation Solution
Implementing a method that conditions the battery by discharging it at a reduced rate, such as the C/2 rate, and incorporating intermittent discharge periods with rest periods, and applying heat during these periods to control lithium deposition, thereby reducing the formation of lithium deposits on negatively charged surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the battery is discharged quickly to maintain high production throughput, then productivity is improved, but lithium deposit formation increases causing short circuits and safety issues
Solution Approach 1:
The discharge conditioning process is divided into periodic cycles consisting of high-rate discharge intervals followed by rest intervals. During the discharge interval, the battery is discharged at a high rate (e.g., 2C) to maintain productivity. During the rest interval, the battery is allowed to recover, which prevents lithium deposit formation. This periodic alternation between discharge and rest periods enables both high production throughput and battery safety.
2Productivity
If high load current is applied to discharge the battery faster, then productivity is improved, but lithium deposition on negative surfaces increases
Solution Approach 1:
The patent implements periodic discharge conditioning where high load current is applied only during discrete discharge intervals rather than continuously. The rest intervals allow lithium ions to redistribute and prevent deposit formation on negative surfaces. This periodic application of high current maintains productivity while eliminating the harmful effect of continuous high current that causes lithium deposition.
3Reliability
If the discharge rate is reduced to decrease lithium deposition, then reliability is improved, but productivity decreases
Solution Approach 1:
Rather than using a uniformly reduced discharge rate, the patent employs periodic action with alternating high-rate discharge intervals and rest intervals. The high-rate discharge intervals maintain manufacturing throughput, while the rest intervals provide the stability benefits of lower discharge rates by preventing lithium deposition. This approach achieves both reliability and productivity simultaneously.
Data Source
AI summary
The present subject matter provides apparatus and methods for controlling lithium deposition during manufacture of implantable medical device batteries. A method includes processing materials to form the battery and performing a discharge conditioning process step. The discharge conditioning process step includes using a reduced discharge load and applying a discharge load intermittently to decrease formation of lithium deposits on negatively charged surfaces within the battery.