In-situ synthetize multi-walled carbon nanotubes@MnO2 nanoflake core-shell structured materials for supercapacitors

► A facile in-situ co-precipitation method is developed to synthesize the MWCNTs@MnO2 core-shell structured material. ► Birnessite-type MnO2 nanoflakes chemically grew around the surface of the MWCNTs. ► The material had the high specific capacitance (380 F g−1) and power density (11.28 kW kg−1). ► The material showed excellent capacitance retention (82.7%) after 3500 cycles.