Non-aqueous Battery Voltage Control for Series Imbalance
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries connected in series experience significant cycle characteristic degradation due to voltage imbalance during discharge, leading to reduced reliability and the need for complex and costly balance circuits.
Innovation Solution
A method for controlling non-aqueous electrolyte secondary batteries by setting the discharge cutoff voltage between 3.4 V to 4.6 V, using a positive electrode with a lithium-transition metal oxide and a negative electrode with spinel-type lithium-titanium composite oxide, where the actual electric capacity of the negative electrode is lower than that of the positive electrode, ensuring a capacity ratio that maintains voltage balance and prevents overdischarge degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two non-aqueous electrolyte secondary batteries are connected in series with conventional discharge cutoff voltage settings, then the batteries can provide higher voltage output, but voltage imbalance during discharge occurs leading to cycle characteristic degradation
Solution Approach 1:
The patent applies parameter changes by setting the discharge cutoff voltage to a specific range (3.4 V to 4.6 V for two-series connection, which corresponds to 1.7 V to 2.3 V per cell). This parameter adjustment ensures that the positive electrode potential remains above 2.3 V during discharge, preventing voltage imbalance and cycle characteristic degradation while maintaining the higher voltage output benefit of series connection.
2Power
If conventional battery configurations are used in series, then voltage output is increased, but balance circuits become necessary increasing device complexity and cost
Solution Approach 1:
The patent implements self-service by designing the battery system to automatically maintain voltage balance through the specific discharge cutoff voltage setting (3.4 V to 4.6 V for two-series). The electrochemical characteristics of the electrodes and the controlled discharge cutoff voltage work together to prevent overdischarge and maintain potential balance without requiring external balance circuits, thereby reducing device complexity and cost.
3Use of energy by moving object
If discharge cutoff voltage is set too low to maximize capacity utilization, then energy output is increased, but overdischarge degradation occurs reducing reliability
Solution Approach 1:
The patent applies preliminary anti-action by preemptively setting the discharge cutoff voltage to a level that prevents overdischarge degradation before it can occur. The discharge cutoff voltage is configured to maintain the positive electrode potential above 2.3 V, which proactively counteracts the harmful effects of overdischarge while still allowing maximum safe capacity utilization, thus protecting the battery reliability.
Data Source
AI summary
A method for controlling a non-aqueous electrolyte secondary battery that includes connecting two non-aqueous electrolyte secondary batteries in series and setting the discharge cutoff voltage to 3.4 V to 4.6 V.