Microporous Membrane Roll with Conductive Core for Static Control
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Solution Overview
Problem
Microporous membrane rolls, particularly those made of polyolefin, experience significant static electricity issues during and after winding, leading to increased electric potential, poor handling ability, and potential adhesion to equipment, which existing technologies have not adequately addressed.
Innovation Solution
A microporous membrane roll is wound on a core partially or wholly made of an electrically conductive member, with the membrane's top and bottom surfaces charged with reversed polarities, achieving a capacitance of 50pF to 1000pF and surface electric potential between -2kV to +2kV, to suppress electric potential rise and improve handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a microporous membrane is wound on a core to form a roll, then the membrane can be supplied and unwound for battery manufacturing, but static electricity accumulates on the membrane surface causing increased electric potential, poor handling ability, and adhesion to equipment
Solution Approach 1:
An electrically conductive member is introduced as an intermediary between the microporous membrane and the core. This conductive member serves as a mediator to drain static electricity from the membrane surface during winding, preventing charge accumulation while maintaining the rolling function. The conductive member acts as a bridge that transfers excess charge to ground, resolving the contradiction between maintaining productivity through rolling and preserving handling ability by controlling static electricity.
2Volume of moving object
If the microporous membrane is wound tightly to improve compactness, then the roll size is reduced, but the friction coefficient on the film surface increases causing peeling charge and higher electric potential during unwinding
Solution Approach 1:
The electrically conductive member positioned between the membrane and core serves as a mediator to dissipate peeling charge generated during tight winding and subsequent unwinding. As the membrane is wound tightly, friction generates charge that would normally accumulate on the membrane surface. The conductive member provides a continuous charge dissipation path, preventing the buildup of peeling charge even under high friction conditions, thus resolving the contradiction between compact roll size and reduction of harmful electrostatic effects.
3Reliability
If conventional insulative cores are used to prevent charge transfer, then the membrane retains static electricity, but using electrically conductive cores may cause unwanted charge discharge
Solution Approach 1:
Instead of making the entire core electrically conductive, only a specific portion of the core (the portion that contacts or is in proximity to the microporous membrane) is made electrically conductive. This localized conductivity allows charge dissipation where it is most needed at the membrane-core interface, while other portions of the core can remain insulative. This resolves the contradiction by providing charge management functionality only where required, preventing electric potential increase without causing unwanted discharge elsewhere in the system.
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 configuration effectively reduces the surface electric potential of the microporous membrane roll, preventing electrostatic adhesion and enhancing handling ability by balancing the electric double layer and maintaining low surface electric potential during unwinding.
Implementation Method 1
a microporous membrane is wound on a core which is partially or wholly made of an electrically conductive member
Implementation Method 2
the microporous membrane might retain static electricity to cause troubles such as a bad winding shape, uncomfortable handling ability and malfunction. Further, since the microporous membrane roll is made of multilayer microporous membrane, static electricity might cause a trouble while the electric potential gradually increases as the membrane is unwound
Data Source
Figure 1(a)~1(b)
Figure 2~3
Figure 4(a)~4(b)
AI summary
A microporous membrane roll (33) comprises cores (1, 11, 21, 31) formed in whole or in part from electrically conductive members (12, 13), and microporous membranes (34, S) which are wound around the cores (1, 11, 21, 31). A first surface (100) and a second surface (200) of the microporous membranes (34, S) are respectively equivalently charged with antipolar charges (102, 201). A method of manufacturing the microporous membrane roll (33) includes diselectrifying the microporous membranes (34, S) with a diselectrifier (35), and winding the microporous membranes (34, S) around the cores (1, 11, 21, 31) formed in whole or in part from the electrically conductive members (12, 13). When the microporous membranes (34, S) are unwound from the cores (1, 11, 21, 31), the microporous membranes (34, S) are prevented from being drawn toward either the microporous membrane roll (33) or peripheral devices by static electricity. The microporous membranes (34, S) are useful as a separator in either a fuel cell or a secondary battery.