Supplementary Information

Cactus-like Iron Diphosphide@Carbon Nanotubes Composites as

Advanced Anode Materials for Lithium-ion BatteriesXibang Chena, Jingyi Qiub, Yimeng Wanga, Furong Huanga, Jing Penga, Jiuqiang Lia,

Maolin Zhaia*aBeijing National Laboratory for Molecular Sciences, Radiochemistry and Radiation

Chemistry Key Laboratory of Fundamental Science, the Key Laboratory of Polymer

Chemistry and Physics of the Ministry of Education, College of Chemistry and

Molecular Engineering, Peking University, Beijing 100871, China.

*E-mail: mlzhai@pku.edu.cnbInstitute of Chemical Defense, Beijing 100191, China

Fig. S1 The SEM images (a) and (b) of RP ; (c) and (d) of Fe@CNTs

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Fig. S2 The SEM images of FeP2@CNTs composites synthesized with different temperature in the

second step for 2h; Red P 20%; (a) 500 °C; (b) 750°C; (c) 900°C.

Fig. S3 The SEM images of FeP2@CNTs composites synthesized with different time at 750 °C in

the second step; Red P 20%; (a) 1 h; (b) 2 h; (c) 4 h

Fig. S4 (a–c) EDS elemental mapping of FeP2@CNTs-2 ball cactus-like composite

Fig. S5 The SEM images of FeP2@CNTs-2 electrode before (a) and after (b) the first discharge

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Fig. S6 Discharge/charge capacities versus cycle number of FeP2@CNTs-1(a), FeP2@CNTs-2(b),

FeP2@CNTs-3(c)and FeP2@CNTs-4(d)at a rate of 0.1 C between 2 and 0 V, respectively. (e)

Discharge/charge capacities versus cycle number of FeP2@CNTs-2, FeP2, and RP at a rate of 0.1 C

between 2 and 0 V, (f) equivalent electrical circuit model

Table. S1

The Re, Rf and Rct of Fe@CNTs cell obtained by fitting experimental data in Fig.5h using

equivalent circuit (Fig. S6f) after first cycling; The Re, Rf and Rct of FeP2@CNTs-2 cell obtained

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by fitting experimental data in Fig.5g using equivalent circuit (Fig. S6f) before and after cycling.

cycling number Re (Ω) Rf (Ω) Rct (Ω)1 st- Fe@CNTs 2.35 36.5 2411 st- FeP2@CNTs-2 1.28 69.0 81.320 th- FeP2@CNTs-2 1.42 116 72.050 th-FeP2@CNTs-2100 th-FeP2@CNTs-2

1.431.81

104101

189162

Table. S2 Some recently reported transition metal phosphide-based anodes in LIBs

Electrode material

Currentdensity

InitialCoulombicEfficiency

(%)

Cycle number

ReversibleCapacity(mAh g-1)

Reference

Amorphous FeP2

0.1 C 61 10 906 [1]

FeP2/carbon nanotube

0.1 C2.5 C

5245

100100

453243

[2]

FePy (3 < y < 4)

0.03 C0.3 C

73_

1020

108945

[3]

FePy(0.85 < y < 0.91)

0.25 C 40 30 420 [4]

Ni5P4/C 0.1 C 79.6 50 644 [5]Porous

Cu3P/Cu0.3 C 75.1 70 377 [6]

FeP@C nanoplates

200 mA g-1 70 100 720 [7]

FeP@C nanorods

30 mA g-1 28 200 480 [8]

Sandwiched Fe2P/GCS

100 mA g-1 64 200 602 [9]

Sn4P3

nanoparticles100 mA g-1 86 320 442 [10]

FeP2@Carbon Ball Cactus

0.1 C2.5 C

91.641.3

100100

736.2650.2

This Work

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