Enhancing capacity of lithium spinel via chlorination and triple doping with transition metals for next generation lithium based batteries
By Limpert, Matthew A.; Baroncini, Elyse A.; Gritton, Evans J.; Atwater, Terrill B.; Wachsman, Eric D.
Published in Journal of Power Sources
2022
Abstract
Lithium spinel (LiMn2O4) possesses a lower theoretical specific capacity compared to layered oxide cathodes (LiCoO2, LiNi0.33Mn0.33Co0.33O2, etc.) but offers an environmentally safe alternative by eliminating the cobalt used in current cathodes. LiMn2O4 requires dopants to increase the operating voltage, maximize energy density, and be competitive with current cathodes. Through a modified Pechini method, this is demonstrated with multiple dopants. The process and spinel structure enable multiple transition metal dopants (nickel, iron, and cobalt) to be added on the Mn site, which increases the specific capacity up to 110 mAh g−1 when charging up to 5.25 V. Chlorine doping in LiMn2O4 expands the lattice from 8.189 to 8.215 Å, allowing for the insertion and removal of additional lithium when cycling down to 2 V. This results in a nearly two fold increase in specific capacity to 200 mAh g−1 when discharging at 0.5 mA cm−2. However, cycling between 5.25 V and 2 V with standard liquid electrolytes increases cell resistance from 63 to 314 Ω due to instability of the electrolyte at voltages greater than 4.5 V. The chlorinated spinel is then paired with a >5 V stable Li6.75La2.75Ca0.25Zr1.5Nb0.5O12 garnet to validate 5 V cycling, achieving 190 mAh g−1 for 5 cycles with limited specific capacity decay.