Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 11, Issue 26, Pages 23236-23243Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.9b05564
Keywords
CoMn layered double hydroxide; large d-spacing; metal-organic frameworks; supercapacitor; true active material
Funding
- MOE, Singapore Ministry of Education [MOE2016-T2-2-138]
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Cobalt-manganese layered double hydroxide (CoMn-LDH) has been known as a highly desired cathode material used with an alkaline electrolyte. However, the layered double hydroxide structure is unstable and changes almost instantly in alkaline solution due to the instability of a manganese(III) ion. Thus, it is important to investigate the true active phase for designing efficient electrode materials. In this work, the metal-organic framework is used as a templating precursor to derive CoMn-LDH from three different manganese solutions, namely, MnSO4, Mn(NO3)(2), and MnCl2. Anions in the solutions participate in the derivation process and strongly affect the layer structure, phase transformation process, and charge storage properties of the resulting materials. CoMn-LDH synthesized from manganese sulfate solution exhibits the largest interlayer spacing of 1.08 nm, and more interestingly, the layered structure can well be retained in KOH solution, while the other two synthesized from manganese chloride and nitrate solutions transform into the spinel structure. As a cathode material, it delivers a high areal capacity of 582.07 mC/cm(2) at 2 mA/cm(2), which is about 100% higher than those of the other two samples. The present work explores the active phase of CoMn-LDH in the alkaline electrolyte and proposes a potential mechanism of the phase transformation, which provides insights into understanding and designing of the active electrode materials for stable and high-performing supercapacitors in an alkaline environment.
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