Issue 6, 2019

Ultrafine Co2P nanorods wrapped by graphene enable a long cycle life performance for a hybrid potassium-ion capacitor

Abstract

Given their high theoretical capacities, metal phosphides are anticipated to be excellent charge-storage materials for high-efficiency potassium-ion batteries. However, one of the major problems is the shuttling of heavy and large K+ ions between electrodes, which triggers rapid capacity fading. Here, we demonstrate that sub-4 nm Co2P nanorods attached to reduced graphene oxide (Co2P@rGO) can operate at a lifespan exceeding thousands of cycles. By taking advantage of the high electronic conductivity and flexibility of reduced graphene oxide (rGO), the composite electrode delivers a high capacity (374 mA h g−1 at 20 mA g−1) and excellent C-rate capability (141 mA h g−1 at 2 A g−1), superior to its commercial counterpart. Impressively, the electrode maintains 54% of the capacity over 5000 cycles, and there is almost no capacity fading after the initial 200 cycles. In addition, a hybrid potassium-ion capacitor, assembled from a Co2P@rGO anode and activated carbon cathode, affords a high energy/power density (87 W h kg−1 and 4260 W kg−1) in a potential window of 1.0–4.0 V, as well as a long lifespan of over 1000 cycles. These extremes demonstrate the high-performance of the Co2P@rGO anode materials and an optimal synthesis strategy to boost K+ storage performance.

Graphical abstract: Ultrafine Co2P nanorods wrapped by graphene enable a long cycle life performance for a hybrid potassium-ion capacitor

Supplementary files

Article information

Article type
Communication
Submitted
01 4 2019
Accepted
11 6 2019
First published
11 6 2019

Nanoscale Horiz., 2019,4, 1394-1401

Ultrafine Co2P nanorods wrapped by graphene enable a long cycle life performance for a hybrid potassium-ion capacitor

Y. Wang, Z. Zhang, G. Wang, X. Yang, Y. Sui, F. Du and B. Zou, Nanoscale Horiz., 2019, 4, 1394 DOI: 10.1039/C9NH00211A

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