Battery Module Control Circuit for Silicon Anode Cycle Life
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Solution Overview
Problem
Lithium ion secondary batteries with silicon-based active materials in the negative electrode mixture layer experience accelerated cycle deterioration, and existing methods to extend battery life are insufficient, as they rely on initial state definitions and voltage changes after discharge, which do not adequately suppress degradation and require a third electrode, leading to decreased capacity.
Innovation Solution
A battery module with a control circuit that measures voltage, current, and time to calculate capacity and differential values, sets a threshold voltage based on the stage structure of graphite, and adjusts discharge cutoff voltage to control charge/discharge operations, thereby improving cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used in the negative electrode mixture layer to increase battery capacity, then battery capacity increases, but cycle deterioration is accelerated
Solution Approach 1:
The invention changes the operating parameters of the battery by setting specific charge and discharge cutoff voltages based on the differential value dQ/dV. By controlling the charge cutoff voltage to be 4.40V or higher and the discharge cutoff voltage to be 2.78V or lower, the battery operates within an optimized voltage range that reduces stress on the silicon-based active material, thereby improving cycle characteristic while maintaining high capacity
Solution Approach 2:
The invention introduces a feedback mechanism by calculating the differential value dQ/dV from measured voltage and current data, and using this calculated value to dynamically determine the charge and discharge cutoff voltages. This feedback loop allows the battery management system to adaptively control charging and discharging processes, preventing overcharge and overdischarge conditions that would accelerate degradation of the silicon-based electrode
2Duration of action of stationary object
If existing voltage-based control methods are used to estimate battery life, then battery life can be estimated, but degradation is not sufficiently suppressed and a third electrode is required
Solution Approach 1:
The invention replaces the need for a physical third electrode by using electrical measurements and calculations. Instead of requiring an additional electrochemical sensing electrode, the system uses voltage and current measurements from the existing two electrodes to calculate dQ/dV, which provides information about the battery's state and enables optimized control without adding mechanical complexity
Solution Approach 2:
The invention changes the control parameter from simple voltage thresholds to dynamically calculated cutoff voltages based on dQ/dV. This parameter transformation enables more precise control of charge/discharge operations, suppressing degradation more effectively than fixed voltage methods while avoiding the need for additional hardware
Data Source
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AI summary
A battery module 100 includes a lithium ion secondary battery 200 and a control circuit 300. The control circuit 300 includes a measurement unit 310 which measures a voltage, a current, and a time of charge/discharge of the lithium ion secondary battery 200, an operation unit 320 which calculates a capacity Q on the basis of the voltage, the current, and the time and calculates a differential value dQ/dV by differentiating the capacity Q with a voltage V, a threshold voltage setting unit 330 which specifies a peak of a low capacity side of the differential value dQ/dV generated on the basis of a stage structure of graphite and sets a voltage at the peak to a threshold voltage, a cutoff voltage setting unit 340 which sets a discharge cutoff voltage of the lithium ion secondary battery 200 on the basis of the threshold voltage, and a charge/discharge control unit 360 which controls the charge/discharge of the lithium ion secondary battery 200 on the basis of the discharge cutoff voltage.