Non-equilibrium metal oxides via reconversion chemistry in lithium-ion batteries

Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles-thus the reversible capacity-remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides. As opposed to the commonly believed conversion chemistry forming rocksalt FeO and MnO, we reveal the two oxide series topotactically transform into non-native body-centred cubic FeO and zincblende MnO via displacement-like reactions whose kinetics are governed by the mobility differences between displaced species. These renewed mechanistic insights suggest avenues for the future design of metal oxide materials as well as new material synthesis routes using electrochemically-assisted methods.

Oriented-Redox Induced Uniform MnO2 Coating on Ni3S2 Nanorod Arrays as a Stable Anode for Enhanced Performances of Lithium Ion Battery

Cost-effective transition metal chalcogenides have aroused wide consideration as alternative anode materials in lithium ion batteries (LIBs) on account of their elevated lithium activity and considerable theoretical capacity. However, the significant challenge caused by the large volume change and shuttle effect of polysulfides during Li ion insertion/extraction severely restricts their practical application. In this work, the uniform MnO₂ coating layer with a tunable thickness on Ni₃S₂ nanorod arrays has been achieved through a mild oriented-redox reaction by taking advantage of the mixing valence of Ni in Ni₃S₂ [(Ni²⁺)₂(Ni⁰)(S^2-)₂]. The core/shell structured nanorod arrays directly used as anode materials of LIBs demonstrate remarkably improved lithium storage performance including high rate capacity and long cycle life, which deliver a discharge capacity of 662 mA h g^-1 for 150 cycles at 0.5 C, corresponding to an elevated capacity retention of 90.7%. The improved electrochemical performances can be assigned to the generation of stable solid electrolyte interface films and suppression of the shuttle behavior with the protection of the MnO₂ coating layer on Ni₃S₂ nanorod arrays.

The effect of acid/alkali treatment on the catalytic combustion activity of manganese oxide octahedral molecular sieves

The acid and alkali treated OMS-2 catalysts were prepared and evaluated as the catalysts for DME and toluene combustion.