The Daegu Gyeongbuk Institute of Science and Technology announced on Dec. 20 that it has produced a bendable composite solid electrolyte free from the risk of explosion and fire, and it is capable of substantially improving the performance and safety of wearable device batteries.

At present, liquid electrolytes are in wide use as an essential component of batteries. In a liquid electrolyte, a separator is used for anode-cathode separation. In the event of damage to the separator, the liquid electrolyte flows and the flow may lead to overheating or explosion.

A solid electrolyte is capable of preventing fire and explosion. In addition, it requires no separator and, as such, a decrease in battery volume can be achieved. However, a solid electrolyte is much less conductive than a liquid electrolyte, and this has been a challenge to researchers.

The institute produced a novel composite solid electrolyte in which polymers are mixed with porous YNa zeolite and lithium salt. In general, zeolite is not uniformly dispersed in polymers. However, the institute achieved a uniform dispersion by lithium salt concentration adjustment and suppressed lithium dendrite formation on the interface of the lithium metal cathode of a lithium-ion battery. As a result, mechanical strength and flexibility have been improved in the solid electrolyte.

The porous YNa zeolite with a large specific surface area made lithium-ion transfer more effective to the point of a transfer rate of 0.84, the best in the world. In addition, an ion conductivity of 1.66 × 10-2 Scm-1 was reached at 60 degrees Celsius along with a 100-cycle capacity retention of at least 95 percent. In a lithium deposition and desorption cycle test, a stable operation continued for more than 1,500 cycles at a current density of as high as 200 μA/cm2. Details of the research are available in the Journal of Materials Chemistry A.