Lithium Dependent Electrochemistry of p‐Type Nanocrystalline CuCrO₂ Films

Abstract

CuCrO2 nanocrystals were synthesized and fabricated into mesoporous thin films to study their electrochemical properties, where a strong [Li+] dependence was observed. An anodic shift in the Cu2+/+ redox potential was observed with increased [Li+] in the electrolyte, in addition to the growth of a new redox feature at E1/2=−0.43 V vs Fc+/0. This new feature was attributed to Cu2+/+ redox chemistry accompanied by Li+ occupation in copper vacancy surface defects. The equilibrium constant and maximum charge for Li+ occupation were determined to be K=0.057 M−1 and 15.5 mC, respectively. The maximum charge was close to the expected value of 11 mC based on the measured concentration of copper vacancies. The pronounced Li+ dependent electrochemistry suggests that CuCrO2 behaves similarly to cathodes in Li‐ion batteries. Thus, chronopotentiometry experiments revealed a 7.8 mA h g−1 charge capacity at cycle 2 and increasing cycling efficiency from 83 to 91 % over 10 cycles. However, a pronounced decrease in charge capacity was observed with increased cycles, attributed to a loss in lithium‐coupled electrochemistry. These studies add to our understanding of surface defects in p‐type oxides and their effect on hole recombination in solar cell devices.