Self‐Templated Formation of Uniform NiCo₂O₄ Hollow Spheres with Complex Interior Structures for Lithium‐Ion Batteries and Supercapacitors

Abstract

Despite the significant advancement in preparing metal oxide hollow structures, most approaches rely on template-based multistep procedures for tailoring the interior structure. In this work, we develop a new generally applicable strategy toward the synthesis of mixed-metal-oxide complex hollow spheres. Starting with metal glycerate solid spheres, we show that subsequent thermal annealing in air leads to the formation of complex hollow spheres of the resulting metal oxide. We demonstrate the concept by synthesizing highly uniform NiCo2O4 hollow spheres with a complex interior structure. With the small primary building nanoparticles, high structural integrity, complex interior architectures, and enlarged surface area, these unique NiCo2O4 hollow spheres exhibit superior electrochemical performances as advanced electrode materials for both lithium-ion batteries and supercapacitors. This approach can be an efficient self-templated strategy for the preparation of mixed-metal-oxide hollow spheres with complex interior structures and functionalities.

Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems

“…Furthermore, Shen et al developed a strategy for the synthesis of NiCo 2 O 4 hollow spheres with complex interior structures. 97 The spinel-type transition metal oxides were prepared by a two-step process: in the first step, uniform nickel-cobalt glycerate spheres used as the precursor were prepared by a solvothermal method, and then, the resulting solid spheres were converted to NiCo 2 O 4 ''core-in-double shell'' hollow spheres by a non-equilibrium heat-treatment process ( Fig. 4k and l).…”

“…In particular, the shape and size control of the spinel-type transition metal oxides has been regarded as a useful strategy to improve the electrochemical performance of ESSs. To date, various spineltype transition metal oxides with diverse shapes in micro-and nano-scale forms, including nanoparticles, [46][47][48] nanoneedles, 49 nanosheets, [49][50][51] nanowires, [52][53][54][55][56] nanorods, 57 nanocubes, 58,94 nanofibres, 59 nanotubes, 60,61 polyhedral structures, 62,63,93 hierarchical structures, 58,92 hollow structures, 58,64,97 and core-shell structures, 65,96,97 have been synthesised and utilised as electroactive materials for ESSs. 98 The porous nanoarchitectures constructed by various morphological strategies have proved to be highly desirable for energy storage materials used for practical ESSs.…”

Macroscopic and Mechanically Robust Hollow Carbon Spheres with Superior Oil Adsorption and Light‐to‐Heat Evaporation Properties

“…[1][2][3][4] Many types of hollow spheres such as silica, [5] metal oxide (Al 2 O 3 , ZnS, TiO 2 ), [6][7][8] polymer, and carbon [9,10] have been developed. Among these systems, hollow carbon spheres (HCSs) are very attractive owing to their special properties, including their high specific surface area, good electrical conductivity, outstanding thermal stability, and good resistance to hydrolytes, acids and alkali, and solvents, which make of effervescent salts inside the droplet, hollow structures with large voids and hierarchical polymer shells could be achieved.…”

Li 3 V 2 (PO 4 ) 3 /LiFePO 4 composite hollow microspheres for wide voltage lithium ion batteries

“…More importantly, the interior void space can buffer the volume change during repeated Li + insertion/extraction, causing improved cycling life [30]. Uniform carbon coating on the particle surface of cathode materials is an economic and feasible technique to enhance the electronic conductivity [17,31,32].…”