Lithium Battery Current Control via Internal Resistance Feedback
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Solution Overview
Problem
Current lithium secondary battery charging and discharging methods do not effectively account for internal resistance variations with the state of charge, leading to suboptimal charge/discharge rates and reduced durability of graphite-based active materials.
Innovation Solution
A method that adjusts charge and discharge currents based on real-time measurements of internal resistance by cutting off the current and measuring open-circuit voltage, allowing for continuous charging and discharging with modified current values to harmonize charging time, charge capacity, discharge current, and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant current charging is performed without adjusting for internal resistance variations, then charging simplicity is maintained, but charging time and charge capacity cannot be optimally harmonized
Solution Approach 1:
The patent implements feedback control by measuring internal resistance during charging and using this information to adjust the charge current. The controller continuously monitors the battery's internal resistance and modifies the charging current accordingly, creating a closed-loop system that optimizes charging time while maintaining appropriate charging conditions.
Solution Approach 2:
The patent transitions from static constant current charging to dynamic current adjustment based on real-time internal resistance measurements. The charging current is made variable rather than fixed, allowing the system to adapt to changing battery conditions during the charging process, thereby optimizing both charging time and capacity utilization.
2Speed
If high current is applied for fast charging, then charging speed increases, but lithium precipitation occurs and durability decreases
Solution Approach 1:
The system uses feedback control to monitor internal resistance as an indicator of battery state and adjusts the charging current to prevent lithium precipitation. When internal resistance increases indicating approaching saturation or risk of precipitation, the controller reduces the charging current, thereby maintaining battery durability while achieving fast charging when conditions permit.
Solution Approach 2:
The patent dynamically changes the charging current parameter based on measured internal resistance values. By adjusting this critical parameter in real-time, the system optimizes charging speed during early stages when the battery can accept high current, then gradually reduces current as the battery approaches full charge or shows signs of saturation, preventing lithium precipitation and extending battery life.
3Manufacturing precision
If internal resistance measurement and current adjustment are implemented, then charge capacity and discharge capacity are harmonized, but measurement and control complexity increases
Solution Approach 1:
The patent employs feedback mechanisms to continuously measure internal resistance and adjust charging parameters accordingly. This closed-loop approach enables precise control of charge capacity by using the measured internal resistance as feedback to optimize the charging current, thereby achieving accurate capacity harmonization between charge and discharge cycles.
Solution Approach 2:
The battery management system performs self-diagnosis and self-adjustment by measuring its own internal resistance and autonomously modifying the charging current without external intervention. This self-service capability enables precise capacity control while minimizing the need for complex external measurement and control infrastructure.
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 optimizes charging and discharging processes by ensuring stable lithium ion insertion and release rates, minimizing lithium precipitation, and maintaining high capacity retention over multiple cycles, while allowing for fast charging and efficient energy utilization.
Implementation Method 1
measuring internal resistance by a method of cutting off the constant current and measuring the open-circuit voltage
Data Source
AI summary
A charging and discharging method for a lithium secondary battery is provided, wherein, while charging or discharging the lithium secondary battery using a constant current, the charge current or allowable discharge current is modified by measuring the internal resistance of the lithium secondary battery. In the charging and discharging method for a lithium secondary battery according to the present disclosure, the charging time and charge capacity, or the discharge current amount and discharge capacity, may be appropriately harmonized, and thus the method may be usefully used as a charging method and a discharging method for a lithium secondary battery.