Modifying Current Collectors to Produce High Volumetric Energy Density and Power Density Storage Devices

Hadi Khani; Timothy J Dowell; David O Wipf

doi:10.1021/acsami.8b03606

Modifying Current Collectors to Produce High Volumetric Energy Density and Power Density Storage Devices

ACS Appl Mater Interfaces. 2018 Jun 27;10(25):21262-21280. doi: 10.1021/acsami.8b03606. Epub 2018 Jun 13.

Authors

Hadi Khani¹, Timothy J Dowell², David O Wipf²

Affiliations

¹ Materials Science and Engineering Program and Texas Materials Institute , The University of Texas at Austin , Austin , Texas 78712 , United States.
² Department of Chemistry , Mississippi State University , Mississippi State , Mississippi 39762 , United States.

PMID: 29863835
DOI: 10.1021/acsami.8b03606

Abstract

We develop zirconium-templated NiO/NiOOH nanosheets on nickel foam and polypyrrole-embedded in exfoliated carbon fiber cloth as complementary electrodes for an asymmetric battery-type supercapacitor device. We achieve high volumetric energy and power density by the modification of commercially available current collectors (CCs). The modified CCs provide the source of active material, actively participate in the charge storage process, provide a larger surface area for active material loading, need no additional binders or conductive additives, and retain the ability to act as the CC. Nickel foam (NF) CCs are modified by use of a soft-templating/solvothermal treatment to generate NiO/NiOOH nanosheets, where the NF is the source of Ni for the synthesis. Carbon-fiber cloth (CFC) CCs are modified by an electrochemical oxidation/reduction process to generate exfoliated core-shell structures (ECFC). Electropolymerization of pyrrole into the shell structure produces polypyrrole embedded in exfoliated core-shell material (PPy@rECFC). Battery-type supercapacitor devices are produced with NiO/NiOOH@NF and PPy@rECFC as positive and negative electrodes, respectively, to demonstrate the utility of this approach. Volumetric energy densities for the full-cell device are in the range of 2.60-4.12 mWh cm^-3 with corresponding power densities in the range of 9.17-425.58 mW cm^-3. This is comparable to thin-film lithium-ion batteries (0.3-10 mWh cm^-3) and better than some commercial supercapacitors (<1 mWh cm^-3).¹ The energy and power density is impressive considering that it was calculated using the entire cell volume (active materials, separator, and both CCs). The full-cell device is highly stable, retaining 96% and 88% of capacity after 2000 and 5000 cycles, respectively. These results demonstrate the utility of directly modifying the CCs and suggest a new method to produce high volumetric energy density and power density storage devices.

Keywords: battery; exfoliated carbon fiber; nickel oxide; polypyrrole; supercapacitor; volumetric energy density; zirconium.