MnO Conversion in Li-Ion Batteries: In Situ Studies and the Role of Mesostructuring

Abstract

Complex manganese oxides have been extensively studied as intercalation Li-ion battery electrodes. The simple oxide MnO has been proposed as a conversion anode material with a theoretical capacity of 756 mAh g −1 for full reduction to the metal.We report the reaction of MnO with Li using in situ X-ray diffraction and find no sign of crystalline products upon either discharge or charge. However, the absence of reflections, paired with electrochemical impedance spectroscopy, suggests disordered discharge products. We also examine composite electrodes with porous particles of MnO as the active component, with pores generated through the reductive heating of Mn 3 O 4 . We compare the behavior of these with more dense MnO powders, including studies of the electrode morphologies pre-and post-cyling. We find differences in the first discharge relevant to the utility of such mesostructuring in conversion reaction materials. Specifically, we find this type of mesostructure, which gives advantage in intercalation and pseudocapacitive storage, does not yield the same benefits for conversion reaction systems.2

Molybdenum Polysulfide Chalcogels as High-Capacity, Anion-Redox-Driven Electrode Materials for Li-Ion Batteries

“…78,79 While benefits of increased porosity may initially result in increased capacity, subsequent cycling in materials such as mesoporous MnO have been reported to rapidly fade. 83 Therefore, we attribute the electrochemical reversibility and of these high-capacity chalcogel electrodes to their amorphous structure.…”

Carbon-Coated Honeycomb Ni-Mn-Co-O Inverse Opal: A High Capacity Ternary Transition Metal Oxide Anode for Li-ion Batteries

“…Co 3 O 4 , MnO etc.) to its parent metal and Li 2 O during charging, with the metal being oxidised during discharge (for anodes)1213. These reactions facilitate higher specific capacities than typically seen for intercalation materials and as a result, interest in the development of conversion mode materials with suitable cycle lifetimes has increased1415.…”

Reversible High Capacity and Reaction Mechanism of Cr2(NCN)3 Negative Electrodes for Li‐Ion Batteries

“…The cyclic voltammetry results obtained for Cr 2 (NCN) 3 between 0.005 and 3 V at 0.05 mV s À1 are shown in Figure 3a. Similarly to all transition-metal carbodiimides, [8,21,26,27,32] a significant difference between the first cycle and subsequent ones is clearly visible in the cyclic voltammetry (CV) profile. This behavior is typical of conversion-type materials that undergo huge morphological and structural changes during the first lithiation.…”

“…To achieve that, numerous candidates from the p-block of the periodic table have been explored, such as silicon, tin, antimony, and phosphorus, as well as their oxides, sulfides, carbonates, etc. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Conversion-type materials have also been widely explored. [22][23][24][25] Among them, transition-metal-based compounds seem to be exciting and potential alternatives for graphite due to their high theoretical specific capacity.…”