Hollow ppy@Ti2Nb10O29-x@NC bowls: A stress–release structure with vacancy defects and coating interface for Li capacitor

• The hollow carbon bowl with large space utilization improves electron conduction and structural reliability of material. • The doping and vacancies defects lower the ion transport barrier and contribute ample active sites for the rapid Li + transmission. • Ppy interface can stabilize the solid-liquid interface through inter-chain or intra-chain bond cooperation. Interfacial coatings and lattice defects are effective strategies to optimize the electrochemical performance of bimetallic oxides. For safe potential window and large theoretical capacity, Ti 2 Nb 10 O 29 presents considerable energy storage potential in lithium ion system. In this work, the composite (ppy@TNO -x @NC), used in lithium ion batteries and lithium ion hybrid capacitors, was prepared by the high volume density carbon bowl derived from biomass as the matrix, the Ti 2 Nb 10 O 29 (TNO) containing oxygen vacancy as storage energy body, and the ultra-thin toughness polymer as coating. TNO modified by vacancy defects offers desirable electrochemical activity to acquire good ion embedding capacity. The ultrathin interfacial coating inhibits lattice misalignment caused by defects in bimetallic oxides, thus maintaining high stability of material. In addition, the hollow carbon bowl with large space utilization improves electron conduction and structural reliablity of material. In fact, as for lithium half battery, ppy@TNO -x @NC can deliver high capacitance of 325.1 mAh g -1 and retain 86.5% capacitance after up to 2000 cycles. While for lithium-ion hybrid capacitor, the maximum energy density and power density of ppy@TNO -x @NC//AC reach 144.9 Wh kg -1 and 10 kW kg -1 , respectively.