Encapsulating manganese oxide nanoparticles within conducting polypyrrole via in situ redox reaction and oxidative polymerization for long-life lithium-ion batteries

Manganese oxides (MnO_x) have been extensively investigated due to their extremely high theoretical capacities for application as conversion anodes in lithium-ion batteries. However, fully performing their theoretical performance still faces poor electric conductivity and serious volume change upon lithium insertion/extraction. Herein, we demonstrate encapsulating manganese oxide nanoparticles within a conducting polymer polypyrrole (PPy) shell as a facile strategy to overcome such flaws through in situ redox reaction and oxidative polymerization process. Such an in situ method combines the redox reaction between potassium permanganate and tetrahydrofuran to form MnO_x nanoparticles and the subsequent oxidative polymerization of pyrrole to form a conductive polypyrrole coating shell by the oxidant KMnO₄ into one step. For the as-fabricated products (MnO_x@PPy), this tenderly introduced conductive PPy shell highly favors the fast electron transfer and preserves the electrode structure integrity upon repeated cycling. As the anode for LIBs, MnO_x@PPy exhibits superior lithium storage performance with a high reversible capacity (1538 mAh·g⁻¹), long-life cyclability (747 mAh·g⁻¹ after 1000 cycles at 1.0C) and durable ratability (574 mAh·g⁻¹ at 2.0C). This work demonstrates that the convenient in situ strategy to form conductive polymer coating shell is effective to improve the performance of conversion anodes and can be extended to other materials for energy storage applications.