Evaluation of Low-cost Natrochalcite Na[Cu2(OH)(H2O)(SO4)2] as an Anode Material for Li- and Na-ion Batteries

Here we report the evaluation of natrochalcite (Na[Cu2(OH)(H2O)(SO4)2]), an anionic layered structure [Cu2(OH)(H2O)(SO4)2]− charge-balanced by Na+, as an anode material for both Li- and Na-ion batteries. It delivers 224 mAh/g and 175 mAh/g in the first discharge in the Li+- and Na+-cells respectively, and decomposes to form amorphous matrixes during this step. In the subsequent charge, the original layered structure is unusually partially recrystallized back from the matrixes, resulting in 53 mAh/g and 35 mAh/g discharge capacities in the second discharge respectively. In subsequent cycling, Li+ in the electrolyte is found to replace the original Na+ during cycling in the Li+-cell and the electrode in the Li+-cell demonstrates better capacity retention rates than that in the Na+-cell, possibly due to Li+ being smaller than Na+ and thus decomposition-recrystallization cycles being more reversible during cycling in the Li+-cell.