Li-Ion Charger Pulse Circuit for Dendrite Breakdown
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Solution Overview
Problem
High charging currents in lithium-ion cells for electric vehicles lead to metallic lithium deposition and dendrite formation, reducing the service life and increasing charging time, especially at low temperatures, due to the growth of needle-shaped dendrites that can penetrate protective films.
Innovation Solution
A device with a series-connected switch, capacitor, and resistor limits the charging current, allowing for targeted discharging pulses that break down dendrites, and an additional device for discharging the capacitor ensures safe operation and efficient energy use, potentially using a DC-DC converter to recover and reuse energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high charging currents are used to shorten charging time, then charging speed is improved, but dendrite formation increases and service life decreases
Solution Approach 1:
The patent applies periodic pulsed charging instead of continuous high current charging. The charger delivers charging current in periodic pulses with specific duty cycles, allowing the lithium-ion cell to undergo brief high-current charging intervals followed by rest periods. This periodic action prevents continuous dendrite growth while maintaining high average charging power, thus shortening overall charging time without sacrificing service life.
Solution Approach 2:
The patent implements preliminary temperature monitoring and conditioning before applying high charging currents. The system pre-heats or pre-cools the cell to optimal temperature ranges and performs initial state-of-charge assessment before initiating pulsed charging. This preliminary preparation ensures the cell is in the best possible state to withstand high charging currents, preventing dendrite formation from the outset while maximizing charging speed.
2Loss of time
If high charging currents are used, then charging time is reduced, but metallic lithium deposition and dendrite formation increase
Solution Approach 1:
The patent uses periodic pulsed charging with controlled duty cycles to deliver high charging currents only during brief intervals. The pulsed nature of the charging current prevents continuous lithium deposition that leads to dendrite formation, while the high peak currents during active pulses maintain short overall charging time. The periodic interruption allows lithium ions to redistribute evenly, preventing localized dendrite growth.
Solution Approach 2:
The patent maintains continuous monitoring and control of charging parameters throughout the charging process. The control unit continuously adjusts pulse width, frequency, and amplitude to optimize charging speed while preventing dendrite formation. This continuous active control ensures that harmful lithium deposition is prevented throughout the entire charging cycle, not just during specific intervals.
3Speed
If high charging currents are used, then charging speed increases, but cell safety decreases due to dendrite penetration risk
Solution Approach 1:
The patent implements periodic pulsed charging with built-in rest intervals that prevent continuous high-current stress on the cell. During the off-periods of each pulse cycle, the cell can dissipate heat and allow lithium ions to redistribute, preventing the conditions that lead to dendrite formation and potential penetration. This periodic action maintains high charging speed while continuously managing safety risks.
Solution Approach 2:
The patent incorporates real-time feedback control through temperature sensors, voltage monitors, and current measurement units that continuously report cell state to the control unit. Based on this feedback, the control unit dynamically adjusts pulse parameters or terminates charging if safety thresholds are approached. This closed-loop feedback system enables high-speed charging while maintaining cell safety through continuous monitoring and adaptive control.
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 solution extends the service life of lithium-ion cells, enables faster charging with higher currents, and reduces energy losses during the electropolishing process, enhancing both safety and cost-effectiveness.
Implementation Method 1
it is proposed that the charger be provided with a capacitor, which is used for discharging during the load pulse
Implementation Method 2
an electrical resistor, by means of which the capacitor is discharged
Implementation Method 3
The chemical process is essentially similar to electropolishing, in which high currents are used to smooth metallic surfaces
Data Source
Figure 1~4B
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AI summary
The invention relates to a device (11) for electropolishing an energy storage device (2) comprising at least one lithium ion cell (3), said device comprising at least one actuatable first switch (S) which is connected in series with a capacitor (C) and an electrical resistance (R) for current limitation parallel to at least one lithium ion cell (3), a device (14) for discharging the capacitor (C) being connected in parallel at least to the capacitor (C). The invention further relates to a charger and to a method for operating said charger.