Porous Carbon Used as Reserved Interspace for Long Cycling Stability of Nanostructured MnO Electrode Materials

Manganese monoxide (MnO) has received considerable attention due to its high energy capacity in lithium-ion batteries (LIBs), whereas lithium-induced volume expansion hinders its cycle capacity. Carbon-coating is an effective strategy to address this issue. However, the volume expansion of the carbon layer is always ignored. Here, porous carbon (PC) was designed as reserved interspace for alleviating lithium-induced volume expansion of MnO@PC electrode materials. To clarify the effect of the reserved interspace, we assembled a Li-ion nanobattery in an aberration-corrected environmental transmission electron microscope using nanostructured MnO@PC as the electrode material to observe the Li insertion process in real time. Nearly no volume expansion was observed in the MnO@PC electrode materials during the lithiation process, indicating that those pores can effectively alleviate the carbon layer volume expansion. Electrochemical measurements of the nanostructured MnO@PC electrode materials were conducted in conventional LIBs, displaying a long cycling stability of about 1000 times. The pores acting as reserved interspace relieved the volume expansion of the carbon layer, and the porous carbon layer improved the long cycling stability of MnO@PC electrode materials. This result provided a promising method for the design of other nanostructured electrode materials.