Supplemental Information

Air-stable red phosphorus anode for potassium/sodium-ion batteries enabled

through dual-protection design

Kan Fanga, Dan Liua*, Xinyuan Xiangb, Xinxin Zhub, Haolin Tangb, Deyu Qua, Zhizhong Xiea,

Junsheng Lia, Deyang Quc*

a Department of Chemistry, School of Chemistry, Chemical Engineering and Life Sciences, Wuhan

University of Technology, 122 Luoshi Road, Wuhan 430070, Chinab School of Materials Science and Engineering, Wuhan University of Technology, 122 Luoshi Road,

Wuhan 430070, P. R. Chinac Department of Mechanical Engineering, College of Engineering and Applied Science, University of

Wisconsin-Milwaukee, 3200 N. Cramer Street, Milwaukee, WI 53211, USA

* Corresponding author.

Email: daniellliu@whut.edu.cn (Dan Liu), deyuqu@whut.edu.cn (Deyu Qu), qud@uwm.edu

(Deyang Qu)

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Material Characterization

The scanning electron microscope (SEM) images were performed by a field emission scanning

electron microscope (ZEISS Supra 55). Powder X-ray diffraction (XRD) patterns were done on a

Bruker D8 Advance diffractometer with a Cu Kα radiation. Transmission electron microscopy

(TEM) examinations and energy dispersive spectra (EDS) were carried out with a JEM-2100F

electron microscope operating at 200 kV. The N2 adsorption-desorption isotherm measurements were

obtained on a Micromeritics Tristar 3020 analyzer. The specific surface areas were analyzed by theⅡ

Brunauer-Emmett-Teller (BET) method. The pore size distributions were tested by the quenched

solid density functional theory (QSDFT) method. Fourier transform infrared (FT-IR) spectroscopy

were recorded on a Nicolet 6700 IR spectrometer. Raman spectra were collected through a Renishaw

inVia Raman spectrometer. X-ray photoelectron spectroscopy (XPS) was collected by using an

Thermo VG Multilab 2000 spectrometer. Thermogravimetric analyses (TGA) were carried out on a

SDT Q600 thermal analyzer with a heating rate of 10 ºC min−1 in an argon flow of 100 mL min−1.

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Figure S1 (a) N2 adsorption-desorption isotherms and (b) pore size distribution curves of AC and

P@AC composites.

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Figure S2 (a) Optical photographs for pyrrole monomer (left) and supernatant after P@AC@PPy

particles were harvested (right). (b) NMR spectra of pyrrole monomer and the supernatant. The

chloroform-d was used as solvent for the NMR measurements.

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Figure S3 TEM images of (a) P@AC@PPy-10 and (b) P@AC@PPy-80 composites. Cycling

performances of (c) P@AC@PPy-10 and (d) P@AC@PPy-80 electrodes in PIB half-cells.

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Figure S4 (a) Cycling performance and (b) voltage profiles of AC@PPy electrode in PIB half-cells.

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Figure S5 (a) Cycling performance and (b) voltage profiles of neat PPy electrode in PIB half-cells.

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Figure S6 (a) Cycling performance at a current of 0.2 A g−1 within 0.01-2.5 V vs Na+/Na and (b)

selected charge-discharge profiles of AC@PPy electrode in SIB half-cells.

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Figure S7 (a) Cycling performance at a current of 0.2 A g−1 within 0.01-2.5 V vs Na+/Na and (b)

selected charge-discharge profiles of neat PPy electrode in SIB half-cells.

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Figure S8 TEM images of individual P@AC composite particle after 100 potassiation/depotassiation

cycles at a current density of 0.05 A g−1.

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Figure S9 (a) XPS survey spectrum of P@AC@PPy for SIBs after 200 cycles and the corresponding

high-resolution spectrum of (b) N 1s. As can be seen, the survey spectrum shows the presence of P,

C, N and O elements after cycling. The high-resolution N 1s spectrum can be deconvoluted into three

peaks around 403.1, 400.7, and 398.8 eV, corresponding to =N+- cations, -N+H- cations, and -NH-

nitrogen atoms in the backbone of PPy, respectively. The shift of typical N 1s peaks may be ascribed

to the formation of SEI film on the surface of P@AC@PPy electrode during cycling. These results

demonstrate that PPy was still coated on the P@AC composite after cycling.

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