A new approach to facilely synthesize crystalline Co2(OH)3Cl microstructures in an eggshell reactor system

Abstract

Sophisticated biological systems developed over millions of years of evolution can be rich sources of inspiration for engineers and scientists. There is increasing interest in the synthesis and applications of metallic hydroxy salts, for example Co₂(OH)₃Cl. It is not an easy task to prepare phase-pure structured Co₂(OH)₃Cl by direct mixing aqueous solutions of CoCl₂ salts and NaOH in a flask. We demonstrate that crystalline Co₂(OH)₃Cl microparticles with unique morphology can be synthesized in eggshell reactor systems. The eggshell reactor system can provide the unique reaction environment for the formation of crystalline Co₂(OH)₃Cl microparticles with relatively well-defined shapes. Time-course experiments and intensive characterization helped us to propose a plausible formation mechanism. Our preliminary results suggest that the microscale Co₂(OH)₃Cl particles synthesized from the eggshell reactor system can be used for lithium-ion batteries, although its performance may still need to be further optimized and improved. In another attempt, we transformed the as-prepared Co₂(OH)₃Cl microparticle precursor into high-order structured Co₃O₄ microparticles preserving the same microscale morphology but with small Co₃O₄ nanoparticles as the basic building units. The as-prepared high-order structured Co₃O₄ microparticles demonstrate reasonably good electrochemical performance with a capacity of 900 mA h g⁻¹ in reversible lithium ion storage.