Ultrahigh areal capacity of self-combusted nanoporous NiCuMn/Cu flexible anode for Li-ion battery

•A flexible anode was prepared by combusting a Cu sandwiched nanoporous alloy.•Mild reduction of combusted sample induces robust vacancies and Cu doping in oxides.•The anode produces a capacity of 9.48 mAh cm−2 with excellent rate performance.•The high performance originates from its unique structure with vacancy-rich mixed oxides.