Porous Carbon Used\nas Reserved Interspace for Long\nCycling Stability of Nanostructured MnO Electrode Materials

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