Layered double hydroxides of Ni with Cr and Mn as candidate electrode materials for alkaline secondary cells

Nickel-based layered double hydroxides (LDHs) having the composition Ni1−xMxIII(OH)2(An−)x/n·zH2O (x=0.2–0.33, MIII=Al, Fe, Co) are isostructural with α-nickel hydroxide, stable to aging in alkali and deliver reversible discharge capacities corresponding to the α/γ couple. The LDHs of Ni with Cr and Mn are also electrochemically active and deliver capacities of 500 (Ni–Cr), 400 (Ni–Mn, x=0.2) and 430 (Ni–Mn, x=0.1) mAh g−1 of Ni, respectively, while control electrodes of βbc (bc: badly crystalline)-nickel hydroxide deliver only 335 mAh g−1.