Abstract
Bimetallic selenides are considered to be the promising high-capacity anode materials for potassium ion batteries (PIBs). However, the dramatic volume fluctuation of K+ ions and pulverization during cycling still limit their practical application in PIBs. Herein, the nitrogen, phosphorus, and sulfur tri-doped carbon (SPNC)-coated bimetallic NiCo2Se4 needle arrays grown on carbon cloth (NiCo2Se4⊂SPNC/CC) prepared as a binder-free anode for PIBs. The polyphosphazene (PSZ) was used as ingenious heteroatoms doping carbon source. The coated SPNC layer derived from the PSZ on the surfaces of NiCo2Se4 needle arrays not only effectively alleviate the volume expansion of NiCo2Se4 but also provide abundant active sites for the storage of K+ ions. As the PIB anode, the NiCo2Se4⊂SPNC/CC could deliver a high reversible capacity of 880.9 mA h g−1 at a current density of 0.1 A g−1. After 500 cycles, the NiCo2Se4⊂SPNC/CC anode still maintains a high reversible capacity of 268.1 mA h·g−1 at a current density of 0.5 A g−1.
Highlights
With the rapid development of portable electronic equipment and electric vehicles, the demand for energy storage devices with high energy density and high safety is increasing
The nitrogen, phosphorus, and sulfur tri-doped carbon-coated NiCo2Se4 needle arrays grown on carbon cloth (NiCo2Se4⊂SPNC/CC) was prepared as a binder-free anode for potassium-ion batteries (PIBs)
The surfaces of NiCo2O4/CC have coated the polymer layers of the polyphosphazene (PSZ) via in-situ polycondensation of hexachlorotripolyphosphazene (HCCP) and 4,4′dihydroxydiphenylsulfone (BPS) (Figure 1B), which is demonstrated by the Fourier transform infrared spectroscopy (FTIR) spectra (Supplementary Figure S1)
Summary
With the rapid development of portable electronic equipment and electric vehicles, the demand for energy storage devices with high energy density and high safety is increasing. NiCo2Se4 still has some problems, such as pulverization of the electrode material due to volume expansion during charging and discharging, which causes the battery’s capacity to rapidly decay In view of these problems, how to solve the volume change during the continuous intercalation and delamination of K+ ions are the main challenge to improve the electrochemical performance and cycle stability of PIBs. In order to solve the above-mentioned problems of NiCo2Se4, Zhou et al deposited the hierarchical NiCo2Se4 nanoneedles/ nanosheets on the skeleton of N-doped three-dimensional porous graphene (NPG) as sodium-ion battery anode and found that the high conductivity and porous NPG improves the transport of electrons of the anode as well as ions (Zhou et al, 2021). After cooling to room temperature, the NiCo2Se4⊂SPNC/CC was carefully washed several times with ethanol and deionized water and dried under vacuum at 60°C for 12 h. Galvanostatic discharge-charge tests were performed between 0.01 and 3.0 V on a battery testing system (CT 2001A, Land)
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