Sealed Lithium Battery Negative Pressurization Method
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Solution Overview
Problem
Existing methods for manufacturing sealed lithium secondary batteries are complex and costly, requiring extensive maintenance of low humidity environments and multiple sealing steps, which increases the risk of defective products and high equipment expenses.
Innovation Solution
A method involving housing an electrode assembly and electrolyte solution in a hard case, negatively pressurizing the case, and sealing it before initial charging, allowing gases to vent naturally, followed by main charging without opening the case, simplifies the process and reduces equipment needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charging treatment is carried out before sealing the battery case in a dry environment, then gases generated during charging can be discharged outside the battery case, but the equipment and upkeep expenses increase due to the need to maintain low humidity environment for extended period
Solution Approach 1:
The battery case is pre-sealed in a dry environment before charging treatment, preparing the sealed structure in advance. This allows the charging process to be completed after sealing without requiring continuous dry environment maintenance, reducing equipment complexity while ensuring proper sealing conditions are established beforehand
Solution Approach 2:
The requirement for maintaining a dry environment is extracted from the charging process and confined only to the pre-sealing operation. By separating the sealing step from the charging step, the dry environment requirement is removed from the extended charging process, significantly reducing equipment and upkeep expenses
2Ease of manufacture
If multiple sealing steps are required to first pre-seal the battery case in a dry environment, then charging treatment can be carried out in open air, but the operations become complicated and result in higher rate of defective product
Solution Approach 1:
The battery case is pre-sealed in a dry environment before charging treatment, preparing the sealed structure in advance. This allows the charging process to be completed after sealing without requiring continuous dry environment maintenance, reducing equipment complexity while ensuring proper sealing conditions are established beforehand
Solution Approach 2:
The pre-sealing and main sealing operations are merged into a single sealing step performed in the dry environment. By combining these operations and eliminating the need to open the case between sealing and charging, the process complexity is reduced and defective product rate is lowered
3Device complexity
If the battery case is sealed before initial charging, then the interior of the hard case does not need to be open to the atmosphere, but gases generated during charging need to be discharged
Solution Approach 1:
The gases generated during initial charging, which would normally be harmful by-products, are converted into a beneficial venting mechanism. The pressure buildup from gas generation automatically opens the safety valve, allowing gas discharge without requiring active venting systems or opening the case
Solution Approach 2:
A safety valve with specific opening pressure is introduced as an intermediary mechanism between the sealed battery case and the external environment. This valve mediates the gas discharge process by opening only when internal pressure exceeds the valve's opening pressure, allowing controlled gas venting while maintaining sealed conditions during normal operation
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 enables the efficient and stable production of lithium secondary batteries with reduced defects and costs, allowing for better gas discharge and improved battery characteristics like energy density and reduced resistance.
Implementation Method 1
the trace amount of moisture present in these battery components and a portion of the electrolyte ingredients (nonaqueous solvent, supporting salt, etc.) are decomposed at the electrode surfaces during initial charging, resulting in the generation of gases
Implementation Method 2
negatively pressurizing the interior of the hard case and sealing the hard case in the negatively pressurized state
Data Source
AI summary
The invention provides a method capable of more simply and easily mass-producing sealed lithium secondary batteries having a stable battery performance. This method of manufacturing a sealed lithium secondary battery having an electrode assembly, an electrolyte solution and a sealable metallic or nonmetallic hard case of a given shape includes the steps of housing the electrode assembly, which includes a positive electrode and a negative electrode, and the electrolyte solution within the hard case; negatively pressurizing the interior of the hard case and sealing the hard case in the negatively pressurized state; carrying out, after the sealing step, initial charging so as to adjust the battery to a voltage at which the electrode assembly generates gases; and carrying out, after the initial charging step, main charging so as to charge the battery to a predetermined voltage. During the interval following the sealing step and up until the main charging step, the hard case is maintained in a sealed state so that the interior of the hard case is not open to the atmosphere.