Overlithiation-driven structural regulation of lithium nickel manganese oxide for high-performance battery cathode

Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material due to its high operation voltage, cobalt free nature and low cost. High energy density of batteries could be realized by coupling LNMO with high-capacity Si based anodes, before which large active lithium loss at the anode should be addressed. Pre-insertion of additional lithium (Li, x) into LNMO, namely overlithaition of LNMO (L1+xNMO) here, becomes a promising approach for active Li compensation. Understanding the materials structure and property evolution of L1+xNMO and their further effect on electrochemical behavior is crucial. Although spinel LNMO could endure a certain amount of extra Li, its excessive insertion could cause degradation in materials structure, interfacial stability and electrochemical performance due to the introduction of large strain, grain boundaries and immoderate reduction of Mn element. L1.4NMO showed a tradeoff between donable lithium-ion capacity and electrochemical cycling stability among the investigated L1+xNMO (x = 0, 0.2, 0.4, 0.6 and 1) samples. L1.4NMO||Si/C cell presented a reversible capacity of 121.7 mAh g−1 and energy density of 429 Wh kg−1, achieving over 50 % improvement than that of LNMO||Si/C cell.