Direct 3D printing of stress-released Zn powder anodes toward flexible dendrite-free Zn batteries

The notorious dendrite growth and poor deformation endurance of Zn metal anode impede the on-going rapid development of flexible Zn-ion batteries (ZIBs). Herein, a direct 3D printing approach architecting a novel Ag-anchored hierarchical porous flexible Zn anode (3DP-ZA) is for the first time proposed for flexible dendrite-free ZIBs. The 3DP-ZA anode demonstrates excellent inherent mechanical flexibility and structural stability: (1) the interaction between the components in the formulated ink (CNT, graphene and cellulose) drives an assembly of a robust intertwined flexible network where Zn powder is homogeneously embedded; (2) the 3D-printing customized macro holes guarantee sufficient buffer space for stress relief to accommodate volume change and maintain structural integrity upon plating/striping. Moreover, the introduced zincophilic Ag source and hierarchical porous structure of the anode endow uniform electronic/ionic fluxes and homogeneous Zn growth. Consequently, the 3DP-ZA//3DP-ZA symmetrical cell delivers a superior lifespan of over 330 h at 1 mA cm−2 and 1 mAh cm−2 with a low voltage hysteresis of 35 mV. Furthermore, a flexible full cell adopting 3DP-ZA anode and PANI coated carbon cloth (PANI@CC) cathode exhibits stable electrochemical performance under continuous deformation. This work points to a new mindset that elaborate 3D structural electrode design for high-performance flexible Zn batteries could be readily realized by 3D printing, which caters to a broad range of flexible energy storage applications.