Pouch Lithium Battery Electrolyte Conditioning for Impact Resistance
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Solution Overview
Problem
Pouch type lithium secondary batteries are vulnerable to external shocks, leading to electrolyte leakage and electrode assembly separation, which compromises safety and performance, especially in harsh environments.
Innovation Solution
A manufacturing method that controls the electrolyte injection amount and pre-charging/discharging cycles to enhance the frictional force between the battery case and electrode assembly, adhering to specific relationships defined by Equations 1 and 1-1, ensuring a frictional force of 15 kgf or greater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If pouch type secondary batteries are used to achieve lightweight design and high energy density, then weight reduction and space utilization are improved, but impact resistance and safety under external shock deteriorate
Solution Approach 1:
The patent applies preliminary action by performing pre-charging and discharging cycles before the battery enters service. This preliminary electrochemical treatment causes electrolyte expansion and contraction that increases frictional force between the electrode assembly and pouch case, thereby enhancing impact resistance before the battery is subjected to external shocks during normal operation.
Solution Approach 2:
The patent utilizes parameter changes by controlling the electrolyte volume and conducting multiple pre-charging/discharging cycles to alter the physical state of the electrolyte. These parameter changes cause the electrolyte to expand and contract, increasing the frictional force between the electrode assembly and pouch case, thereby improving impact resistance while maintaining the lightweight pouch structure.
2Reliability
If electrolyte injection amount is increased to improve frictional force between battery case and electrode assembly, then impact resistance is improved, but battery cell volume and energy density are reduced
Solution Approach 1:
The patent applies periodic action by conducting multiple pre-charging and discharging cycles. This periodic electrochemical process causes repeated expansion and contraction of the electrolyte, which progressively increases the frictional force between the electrode assembly and pouch case. This approach achieves high impact resistance without requiring excessive electrolyte volume, as the mechanical effect is generated through repeated cyclic action rather than static volume increase.
Solution Approach 2:
The patent utilizes parameter changes by controlling the electrolyte injection amount within an optimized range (2.0-3.0 g/Ah) and combining it with multiple pre-charging/discharging cycles. This combination allows the electrolyte to generate sufficient frictional force through expansion and contraction during cycling, achieving high impact resistance without excessive electrolyte volume that would reduce energy density.
3Reliability
If multiple pre-charging and discharging cycles are performed to increase frictional force, then impact resistance is improved, but manufacturing time and process complexity are increased
Solution Approach 1:
The patent applies partial action by performing a limited number of pre-charging and discharging cycles (3-10 cycles) rather than continuous cycling. This partial action is sufficient to achieve the desired frictional force increase and impact resistance improvement, while avoiding excessive manufacturing time consumption. The optimal cycle number balances the frictional force enhancement effect with manufacturing efficiency.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the number of pre-charging/discharging cycles to a specific range (3-10 cycles) and controlling the C-rate (0.1C-1C). These parameter optimizations ensure that sufficient frictional force is generated to improve impact resistance while minimizing the time required for this treatment process, thereby balancing performance improvement with manufacturing efficiency.
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
The method significantly improves impact resistance by preventing electrolyte leakage and electrode assembly separation under crash conditions, maintaining battery integrity and safety.
Implementation Method 1
it has been found that when a battery is manufactured such that an electrolyte injection amount and the number of pre-charging/discharging satisfy a particular relationship, a frictional force between an electrode assembly and an inner surface of a battery case increases significantly
Data Source
AI summary
A method for manufacturing a lithium secondary battery may includes a first step of preparing a battery case, a second step of disposing an electrode assembly in the battery case and injecting an electrolyte to assemble a battery cell such that electrolyte mass per unit capacity is a (g/Ah), wherein a is from 2.0 g/Ah to 3.0 g/Ah, a third step of activating the battery cell, and a fourth step of pre-charging/discharging the activated battery cell b times, wherein b is an integer of 0 to 3, and wherein Equation 1 below is satisfied;15≤486.77-373.09×e(-0.006b)×a0.29≤30Equation 1