Separators play a key role in all batteries. The main function is to keep the positive and negative electrodes apart to prevent electrical short circuits and, at the same time allow rapid transport of ionic charge carriers needed to complete the circuit during the passage of current in an electro-chemical cell. Separators should be very good electronic insulators and have the capability of conducting ions by either intrinsic ionic conductor or by soaking electrolyte. They should minimize any processes that adversely affect the electrochemical energy efficiency of the batteries.
A separator is a porous membrane placed between electrodes of opposite polarity, permeable to ionic flow but preventing electric contact of the electrodes. A variety of separators have been used in batteries over the years. Starting with cedar shingles and sausage casing, separators have been manufactured from cellulosic papers and cellophane to nonwoven fabrics, foams, ion exchange membranes, and microporous flat sheet membranes made from polymeric materials. As batteries have become more sophisticated, separator function has also become more demanding and complex.
Common PP and PE separator membranes can be replaced with a nanofiber separator made from PVDF, PVDF copolymers and PAN .
NanospiderTM equipment allows nonwoven separator production. These nanofibrous separators meet the most important battery separator performance requirements such as:
- Chemical stability
- Tensile strength (acceptable for winding machines)
- Thermal stability (The requirement of less than 5% shrinkage after 60 min at 90 °C
(in a vacuum))
- Thickness (- Dimensional stability
- Porosity (greater than 40%)
- Pore size and pore size distribution (uniform pore distribution to avoid performance
loss arising from non-uniform current densities )
Enabling construction of a battery with superior parameters.
Elmarco’s NanospiderTM technology enables the manufacture of cost effective separators through:
- Lower consumption of polymer material due to the lower basis weight
of the membrane
- Significant increase of battery power density
- Higher charge and discharge rate
- Increase in battery life