A study of the structure–activity relationship of the electrochemical performance and Li/Ni mixing of lithium-rich materials by neutron diffraction†
Abstract
0.3Li2MnO3·0.7LiNi0.5−xMn0.5−xM2xO2 (M = Mg or Al, x = 0–0.08) samples have been synthesized by a combination of co-precipitation (CP) and solid-state reaction. Electrochemical measurements show that not only can the charge–discharge capacity of lithium-rich materials be enhanced, but more importantly, the rate capacity can be greatly improved by doping with magnesium and aluminum. At a current density of 400 mA g−1, the 0.3Li2MnO3·0.7LiNi0.46Mn0.46Mg0.08O2 and 0.3Li2MnO3·0.7LiNi0.49Mn0.49Al0.02O2 electrodes deliver discharge capacities of 135 mA h g−1 and 127 mA h g−1, respectively, while the pristine electrode delivers a discharge capacity of only 10 mA h g−1. Through studying the structure of lithium-rich materials, we find that the Li/Ni mixing of lithium-rich materials is reduced by doping with magnesium and aluminum, in turn, the performance of doped lithium-rich materials is improved greatly. Furthermore, compared with Al-doped lithium-rich materials, the Li/Ni mixing of Mg-doped materials is further reduced. So the performance improvement of Mg-doped lithium-rich materials is more obvious than that of Al-doped materials.
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