Battery Charging with Oscillation Current to Suppress Lithium Dendrites
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Solution Overview
Problem
The safety performance of batteries is compromised due to lithium precipitation during the charging process, which can lead to short circuits caused by lithium dendrites piercing through the separator between the positive and negative electrodes, necessitating a method to effectively remove these precipitates and prevent their formation.
Innovation Solution
A charging method involving an oscillation current with alternating charging and discharging cycles is applied, where the charging device outputs a high-frequency oscillation current with specific sub-periods and magnitudes based on the battery's state of charge and health, dissolving lithium precipitates and preventing new dendrite growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional charging is used, then charging speed is maintained, but lithium precipitation occurs leading to safety issues
Solution Approach 1:
The patent applies periodic action by implementing oscillation current with alternating charging and discharging sub-periods. The charging device outputs current in cycles where the first sub-period charges the battery and the second sub-period discharges it, creating a periodic oscillation that prevents lithium precipitation while maintaining overall charging progress. This periodic reversal of current direction dissolves precipitated lithium dendrites before they can cause short circuits.
Solution Approach 2:
The patent changes the current parameter from constant to oscillating by varying the current magnitude and direction over time. The oscillation current modifies the electrical parameters including current density, voltage, and time characteristics. By controlling the ratio of charging to discharging sub-periods and adjusting current magnitudes, the system prevents lithium precipitation while maintaining net charging, thus resolving the safety issue without sacrificing charging functionality.
2Reliability
If oscillation current is applied to remove lithium precipitates, then battery safety is improved, but charging time increases
Solution Approach 1:
The patent applies partial action by implementing brief discharging sub-periods within the oscillation cycles. Rather than fully discharging the battery, only short-duration discharging pulses are applied just enough to dissolve lithium precipitates. The charging sub-periods are significantly longer and provide the majority of the charging, while the discharging sub-periods serve the specific function of precipitate removal. This partial discharging approach maintains safety while minimizing time loss.
3Productivity
If high current is used for fast charging, then charging speed increases, but lithium dendrite growth accelerates
Solution Approach 1:
The patent uses periodic oscillation current where high charging current is applied in the first sub-period to maintain fast charging speed, followed by a second sub-period where discharging current dissolves the lithium dendrites that formed during the charging phase. This periodic alternation allows the system to benefit from high current charging while simultaneously preventing dendrite accumulation through regular discharging pulses, thus resolving the contradiction between charging speed and dendrite growth.
Solution Approach 2:
The patent converts the harmful effect of high current-induced lithium precipitation into a beneficial process by intentionally allowing controlled precipitation during charging sub-periods, then using discharging sub-periods to dissolve these precipitates. The lithium that would normally form dangerous dendrites is instead cycled through precipitation and dissolution, ultimately reinforcing the electrode structure while maintaining fast charging capability. This transforms the harmful precipitation phenomenon into a useful mechanism for dendrite prevention.
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 method effectively removes lithium precipitates, prevents short circuits, and extends battery life by ensuring the safety performance of batteries through controlled oscillation currents that dissolve dendrites and manage state of charge fluctuations.
Implementation Method 1
the oscillation current includes n cycle periods, each of the cycle periods includes a first sub-period and a second sub-period, a current output by the charging device during the first sub-period is a first current, a current output by the charging device during the second sub-period is a second current, and a direction of the first current is opposite to that of the second current
Data Source
AI summary
A charging method may include: sending a first command to a charging device, the first command being used to control the charging device to output an oscillation current to the battery during a first time period in a charging process, where the oscillation current may include n cycle periods, n being a positive integer greater than 1, each of the cycle periods may include a first sub-period and a second sub-period, a current output by the charging device during the first sub-period is a first current, a current output by the charging device during the second sub-period is a second current, and a direction of the first current may be opposite to that of the second current; and sending a second command to the charging device, the second command being used to instruct the charging device to charge the battery during a second time period in the charging process.