Formation of Nanocrystalline Cobalt Oxide-Decorated Graphene for Secondary Lithium-Air Battery and Its Catalytic Performance in Concentrated Alkaline Solutions

Abstract

A potent cathode catalyst of octahedral cobalt oxide (Co3O4) was synthesized onto graphene (GR) nanosheets via a two-step preparation method. The precursor cobalt solution reacted with GR during the initial hydrolysis step to form intermediates. A subsequent hydrothermal reaction promoted Co3O4 crystallinity with a crystalline size of 73 nm, resulting in octahedral particles of 100–300 nm in size. Scanning electron microscopy, Raman spectroscopy, and X-ray diffraction analysis confirmed the successful formation of the Co3O4/GR composite. This catalyst composite was sprayed onto a carbon cloth to form a cathode for the hybrid electrolyte lithium-air battery (HELAB). This catalyst demonstrated improved oxygen reduction and oxygen evolution capabilities. The HELAB containing this catalyst showed a higher discharge voltage and stable charge voltage, resulting in a 34% reduction in overall over-potential compared to that without the Co3O4/GR composite. The use of saturated LiOH in 11.6 M LiCl aqueous electrolyte at the cathode further reduced the over-potential by 0.5 V. It is proposed that the suppressed dissociation of LiOH expedites the charging reaction from un-dissociated LiOH. This Co3O4/GR composite is a promising bi-functional catalyst, suitable as a cathode material for a HELAB operating in high relative humidity and highly alkaline environment.

Electrochemical energy storage and conversion: An overview

“…Thus, designing of the spinel electrocatalysts with appropriate arrangement of Co 2+ and Co 3+ has become very essential to achieve the optimized bifunctional catalytic activity. Recently, octahedral cobalt oxide Co 3 O 4 /GR cathode catalysts with a high humidity of >70% was prepared via a two‐step preparation method (S. H. Peng et al, 2020). The Li‐oxygen cell assembled with Co 3 O 4 /GR catalyst has shown over‐potential reduction of 34% and good cycling stability.…”

A Flexible Lithium-Ion-Conducting Membrane with Highly Loaded Titanium Oxide Nanoparticles to Promote Charge Transfer for Lithium–Air Battery

“…The HELAB directly addresses the aforementioned problems by mitigating the flammability and volatilization of aprotic LE, with the discharge product (LiOH) being soluble in an aqueous LE. In addition, HELABs can be operated under an ambient atmosphere with high relative humidity, thereby saving the cost of the high-purity O 2 supply device required in aprotic Li–air batteries [ 13 , 14 ]. The most common oxides used for an LICM are NASICON-type materials such as Li 1+x Al x Ti 2−x (PO 4 ) 3 (LATP) and Li 1+x Al x Ge 2−x (PO 4 ) 3 (LAGP).…”

“…The most common oxides used for an LICM are NASICON-type materials such as Li 1+x Al x Ti 2−x (PO 4 ) 3 (LATP) and Li 1+x Al x Ge 2−x (PO 4 ) 3 (LAGP). However, due to its rigid nature, a ceramic LICM has a risk of cracking during assembly, followed by electrolyte leakage, corrosion of the lithium, and deterioration of the battery [ 13 , 14 ].…”