Resurrecting a battery
chemistry thought to be only primary, we
demonstrate the first example of a rechargeable alkaline zinc/copper
oxide battery. With the incorporation of a Bi2O3 additive to stabilize the copper oxide-based conversion cathode,
Zn/(CuO–Bi2O3) cells are capable of cycling
over 100 times at >124 W h/L, with capacities from 674 mA h/g (cycle
1) to 362 mA h/g (cycle 150). The crucial role of Bi2O3 in facilitating the electrochemical reversibility of Cu2O, Cu(OH)2, and Cuo was supported by
scanning and transmission electrochemical microscopy, cyclic voltammetry,
and rotating ring-disc electrode voltammetry and monitored via operando energy-dispersive X-ray diffraction measurements.
Bismuth was identified as serving two roles, decreasing the cell resistance
and promoting Cu(I) and Cu(II) reduction. To mitigate the capacity
losses of long-term cycling CuO cells, we demonstrate two limited
depth of discharge (DOD) strategies. First, a 30% DOD (202 mA h/g)
retains 99.9% capacity over 250 cycles. Second, the modification of
the CuO cathode by the inclusion of additional Cu metal enables performance
at very high areal capacities of ∼40 mA h/cm2 and
unprecedented energy densities of ∼260 W h/L, with near 100%
Coulombic efficiency. This work revitalizes a historically primary
battery chemistry and opens opportunity to future works in developing
copper-based conversion cathode chemistries for the realization of
low-cost, safe, and energy-dense secondary batteries.