Li-Ion Battery Alternate Charging for Separator Impregnation
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Solution Overview
Problem
Lithium ion batteries face deteriorated cycle performance due to uneven impregnation of the electrolytic solution within the power storage element, particularly in the separator's pores, which affects the battery's charging and discharging efficiency.
Innovation Solution
A method involving alternate charging and discharging at specific voltage ranges (4.0 V to 4.1 V) with a current rate of 0.6 C or higher, and a total of 3 or more cycles, to facilitate the deep permeation of the electrolytic solution into the separator's pores, utilizing high-nickel and Si-based active materials in the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power storage element is impregnated with the electrolytic solution in an environment with reduced pressure, then the impregnation process is accelerated, but the electrolytic solution does not fully permeate the pores of the separator
Solution Approach 1:
The patent applies periodic action by performing alternate charging and discharging cycles at specific voltage ranges (4.0-4.1V). This periodic electrical stimulation causes repeated expansion and contraction of the electrodes, which in turn repeatedly opens and closes the separator pores, allowing the electrolytic solution to progressively permeate deeper into the pore structure over multiple cycles.
Solution Approach 2:
The patent utilizes parameter changes by operating at a specific voltage range (4.0-4.1V) where a unique phenomenon occurs. At this voltage, the electrodes exhibit specific expansion/contraction characteristics that maximize pore opening and closing, thereby optimizing electrolytic solution permeation. The current rate is also controlled at 0.6C or higher to achieve the desired effect.
2Productivity
If the separator pores are not fully permeated with the electrolytic solution, then the manufacturing process is faster, but the cycle performance deteriorates
Solution Approach 1:
The patent applies preliminary action by performing initial charging before the alternate charging and discharging cycles. This initial charging prepares the battery by establishing basic electrolyte distribution and electrode polarization, creating favorable conditions for the subsequent periodic action to effectively permeate the separator pores and improve cycle performance.
3Manufacturing precision
If alternate charging and discharging is performed at voltage between 4.0 V and 4.1 V with current rate of 0.6 C or higher, then the electrolytic solution permeates deeply into the separator pores, but the charging and discharging time increases
Solution Approach 1:
The patent applies partial or excessive action by performing a limited number of alternate charging and discharging cycles (3 or more times) at the specific voltage range (4.0-4.1V) and current rate (0.6C or higher). This provides just enough excessive action to achieve deep permeation of the electrolytic solution into the separator pores, beyond what would be achieved by conventional single-step impregnation, while avoiding unnecessary additional cycles that would waste time.
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 enhances the cycle performance by ensuring the electrolytic solution permeates deeply into the separator's pores, improving the battery's charging and discharging efficiency and reducing irreversible capacity.
Implementation Method 1
the pores in the separator may contract due to the increase in the force pressing the separator. It is considered that the contraction of the pores may cause the electrolytic solution to be discharged from the pores.
Implementation Method 2
the electrolytic solution may be aspirated into the pores due to the expansion of the pores
Data Source
AI summary
(a) A battery including a power storage element and an electrolytic solution is assembled. (b) Initial charging is performed on the battery. (c) Alternate charging and discharging are performed on the battery after the initial charging. In the alternate charging and discharging, charging and discharging are alternately performed once or more respectively at a voltage between 4.0 V and 4.1 V and a current rate of 0.6 C or higher. The total number of times of charging and discharging is 3 or greater. The charging is performed such that the voltage changes by 0.05 V or higher and 0.1 V or lower whenever the charging is performed once. The discharging is performed such that the voltage changes by 0.05 V or higher and 0.1 V or lower whenever the discharging is performed once.