Electric vehicle driving range could be doubled, study says

Researchers have said it is possible to increase the driving range of electric vehicles by almost double the current range through modifications in the salt concentrations.

Department of Energy’s Pacific Northwest National Laboratory researchers demonstrated a small lithium-metal battery can re-charge about seven times more than batteries with conventional electrolytes.

A battery’s electrolyte solution shuttles charged atoms between electrodes to generate electricity. Finding an electrolyte solution that doesn’t corrode the electrodes in a lithium-metal battery is a challenge but the PNNL approach, published online in Advanced Materials, successfully creates a protective layer around the electrodes and achieves significantly increased charge/discharge cycles.

Conventional electrolytes used in lithium-ion batteries are not suitable for lithium-metal batteries. Lithium-metal batteries that replace a graphite electrode with a lithium electrode are the ‘holy grail’ of energy storage systems because lithium has a greater storage capacity and, therefore, a lithium-metal battery has double or triple the storage capacity. That extra power enables electric vehicles to drive more than two times longer between charges.

Adding more lithium-based salt to the liquid electrolyte mix creates a more stable interface between the electrolyte and the electrodes which, in turn, affects the life of the battery. But that high concentration of salt comes with distinct downsides — including the high cost of lithium salt. The high concentration also increases viscosity and lowers conductivity of the ions through the electrolyte.

In the new process, they were able to localize the high concentrations of lithium-based salt into “clusters” which are able to still form protective barriers on the electrode and prevent the growth of dendrites — microscopic, pin-like fibers — that cause rechargeable batteries to short circuit and limit their life span.

PNNL’s patent-pending electrolyte was tested in PNNL’s Advanced Battery Facility on an experimental battery cell similar in size to a watch battery. It was able to retain 80 percent of its initial charge after 700 cycles of discharging and recharging. A battery using a standard electrolyte can only maintain its charge for about 100 cycles.