Stanford University researchers found that resting a discharged lithium-metal EV battery extends its life and restores battery capacity. The study was published in Nature on February 7, 2023, by study co-lead author Wenbo Zhang. The method aims to improve lithium metal cycling life in a simple, cost-effective, and fast manner. Resting the battery in a discharged state recovers lost capacity and increases cycle life. Improvements can be achieved by reprogramming the battery management software with no additional costs or changes.
The study provides practical insights for EV manufacturers to adapt lithium metal technology to real-world driving conditions. Lithium-metal batteries can double the range of EVs but lose capacity quickly after charging and discharging. A lithium-ion battery consists of a graphite anode and lithium metal oxide cathode, while a lithium-metal battery has an electroplated lithium metal anode. Lithium-metal batteries store twice the energy of lithium-ion batteries in the same space and weigh less.
During discharge, micron-sized lithium metal bits become trapped in the solid electrolyte interphase (SEI), reducing battery performance. The SEI matrix, composed of decomposed electrolyte, surrounds isolated lithium metal and prevents electrochemical reactions. Repeated charging and discharging cause the build-up of dead lithium, reducing battery capacity rapidly.
Previous research found that the SEI matrix dissolves when the battery is idle, prompting the study on battery resting. Discharging the battery and resting for an hour dissolves some of the SEI matrix surrounding dead lithium. Dead lithium reconnects with the anode when the battery is recharged, increasing battery performance and extending cycle life. Capacity can be recovered by resting the discharged battery, which was initially thought to be irreversible.
The average US driver spends about an hour driving daily, making resting the battery for several hours feasible. A typical EV has 4,000 batteries in modules controlled by a battery management system. Lithium-metal battery management systems can discharge individual modules entirely for resting. Real-world application of resting lithium-metal batteries can improve EV performance and extend battery life.
