Thermal Decomposition Study on Li(2)O(2) for Li(2)NiO(2) Synthesis as a Sacrificing Positive Additive of Lithium-Ion Batteries

Herein, thermal decomposition experiments of lithium peroxide (Li(2)O(2)) were performed to prepare a precursor (Li(2)O) for sacrificing cathode material, Li(2)NiO(2). The Li(2)O(2) was prepared by a hydrometallurgical reaction between LiOH·H(2)O and H(2)O(2). The overall reaction during annealing was found to involve the following three steps: (1) dehydration of LiOH·H(2)O, (2) decomposition of Li(2)O(2), and (3) pyrolysis of the remaining anhydrous LiOH. This stepwise reaction was elucidated by thermal gravimetric and quantitative X-ray diffraction analyses. Furthermore, over-lithiated lithium nickel oxide (Li(2)NiO(2)) using our lithium precursor was synthesized, which exhibited a larger yield of 90.9% and higher irreversible capacity of 261 to 265 mAh g(−1) than the sample prepared by commercially purchased Li(2)O (45.6% and 177 to 185 mAh g(−1), respectively) due to optimal powder preparation conditions.