Preparation, Lithium Storage Performance and Thermal Stability of Nickel-Rich Layered LiNi0.815Co0.15Al0.035O2/RGO Composites

Graphical A lithium nickel cobalt aluminium oxide/reduced graphene oxide (LNCAO/RGO) composite is synthesized by chemical lithiation of commercial NCA, followed by coating with RGO. The effects on electrochemical performances and thermal stability are investigated. RGO shells provide protection against electrolyte corrosions and diminish Li + /Ni 2+ disordering, resulting in remarkable long-term cycling stability, rate capability and thermal stability. Ni-rich materials are promising Li-ion battery cathodes due to their high capacity but still suffer from electrolyte corrosions and inferior thermal stability, limiting the lithium storage capability. To improve both, lithium storage performances and thermal stability, LiNi 0.815 Co 0.15 Al 0.035 O 2 (LNCAO)/reduced graphene oxide (RGO) composites are synthesized by chemical lithiation of commercial Ni 0.815 Co 0.15 Al 0.035 (OH) 2 precursors with LiOH ⋅ H 2 O, followed by simply wet coating with RGO. The effects of such RGO modifications on lithium storage performances and thermal stability of the achieved LNCAO/RGO are investigated. Compared to LNCAO, the unique LNCAO/RGO (with ∼2.5 wt.% RGO) electrodes exhibit considerably improved cycling stability and high-rate capability (a reversible capacity of 135 mAh g −1 at 10 C), with a capacity decay rate of 0.07 % per cycle at 1 C, half of that of pristine LNCAO (0.14 %/cycle). As evidenced by differential scanning calorimetry, thermal stability is also significantly enhanced since the heat generation decreases from 912 to 586 J g −1 for pristine LNCAO and LNCAO/RGO, respectively. This could be ascribed to the unique structures and the encapsulated RGO coating layers, effectively protecting LNCAO against electrolyte corrosions and decreasing the level of Li + /Ni 2+ disordering. This study helps us further understand the critical roles of RGO layers in electrochemical performances and thermal stability of Ni-rich-based cathodes for lithium/sodium storage.