Copper has been widely used in many applications due to its outstanding properties such as malleability, high corrosion resistance, and excellent electrical and thermal conductivities. While 3D printing can offer many advantages from layer-by-layer fabrication, the 3D printing of highly pure copper is still challenging due to the thermal issues caused by copper’s high conductivity. This paper presents a comprehensive review of recent work on 3D printing technology of highly pure copper over the past few years. The advantages and current issues of 3D printing methods are compared while different properties of copper parts printed by these methods are summarized. Finally, we provide several potential applications of the 3D printed copper parts and an overview of current developments that could lead to new improvements in this advanced manufacturing field.

Herein, novel phosphide composites (Ni x Co 3−x P y ) are reported with welldefined hexagonal thin-plate morphology and a hieratically porous but robust junction-free 3D network constructed by interwelding porous NWs, which are achieved by first synthesizing 2D Ni-Co precursors with tunable Ni/ Co molar ratios and top-down etching, followed by phosphorization. Owing to enhanced electron/ion transfer, increased availability of active sites/ interfaces, rich mixed valences of bimetals and P, and strong intercomponent synergy, the optimized NiCoP-CoP shows a specific capacitance reaching 1969 F g −1 , much larger than those of Ni-Co sulfides and other similar phosphides. An asymmetric supercapacitor employing the advanced NiCoP-CoP as positive electrode exhibits a remarkable cycling stability with 93% retention after 5000 cycles at 8 A g −1 , which is mainly attributed to such architecture allowing strong mechanical stability and to effectively buffer the strain/volume expansion during fast Faradaic reactions. A single device having both an output voltage as high as 7.2 V and an ultrahigh areal energy density of 639 mWh cm −2 at 48 W cm −2 is realized by a designed configuration in which four capacitors in series connection are stacked with solid-state electrolyte. An almost linear increase in output voltage with the layer number indicates possibility to meet various output requirements for miniaturized electronics.

With novel hierarchical hexagonal prism arrays, a carbon-doped mixed-valence Co–Mn–Fe phosphide electrode shows high capacitance, rate capability and cycling stability.