Binder-Free Anodes for Potassium-ion Batteries Comprising Antimony Nanoparticles on Carbon Nanotubes Obtained Using Electrophoretic Deposition

Antimony has a high theoretical capacity and suitable alloying/dealloying potentials to make it a future anode for potassium-ion batteries (PIBs); however, substantial volumetric changes, severe pulverization, and active mass delamination from the Cu foil during potassiation/depotassiation need to be overcome. Herein, we present the use of electrophoretic deposition (EPD) to fabricate binder-free electrodes consisting of Sb nanoparticles (NPs) embedded in interconnected multiwalled carbon nanotubes (MWCNTs). The anode architecture allows volume changes to be accommodated and prevents Sb delamination within the binder-free electrodes. The Sb mass ratio of the Sb/CNT nanocomposites was varied, with the optimized Sb/CNT nanocomposite delivering a high reversible capacity of 341.30 mA h g–1 (∼90% of the initial charge capacity) after 300 cycles at C/5 and 185.69 mA h g–1 after 300 cycles at 1C. Postcycling investigations reveal that the stable performance is due to the unique Sb/CNT nanocomposite structure, which can be retained over extended cycling, protecting Sb NPs from volume changes and retaining the integrity of the electrode. Our findings not only suggest a facile fabrication method for high-performance alloy-based anodes in PIBs but also encourage the development of alloying-based anodes for next-generation PIBs.

(Figure S5a), 28.9 m 2 g −1 and 46.4 m 2 g −1 (Figure S5b), respectively.Figure S6a reveals the weight loss of the CNT sample near 100 o C due to the removal of moisture, then the combustion of oxygen-containing functional groups present in CNT to 500 o C, and finally the burning of the remaining carbon in air observed from ~ 500 ºC to 600 ºC. 1 It is recognized that all Sb/CNT samples exhibit similar TGA behaviours, including the combustion reaction of CNT and the oxidization process of Sb.Initially, the weight loss observed was due to moisture and oxygen-containing functional groups as described earlier.
As the temperature steadily increased, a slight weight gain in the samples observed from       The Sb/CNT-1 and Sb/CNT-3 electrodes delivered specific capacities of 305.21 and 395.93 mA h g −1 , respectively, in the first cycle at 0.2C.Sb/CNT-3 exhibited an initial CE of 42.5% (Figure S8b), higher than the CEs of Sb/CNT-2 (39.5%, Figure 3f) and Sb/CNT-1 (37.1%, Figure S8b) in the first cycle.The effect of CNT content on the CE of Sb/CNT continues in a few first cycles, the CEs of all Sb/CNT electrodes only reached over 96% after 10 cycles and maintained around 98% after 15 cycles whereas the CE of Sb electrode (Figure 3f) was over 97% after 5 cycles and maintained around 98% after that.

Figure S1 .
Figure S1.XPS spectra of Sb NPs: (a) wide scan spectrum and core peaks corresponding to

Figure S6 .
Figure S6.Thermogravimetric (TG) plots of (a) CNT, (b) Sb/CNT-1, (c) Sb/CNT-2, and (d) ~350 o C to 500 o C was attributed to the partial oxidation of metallic Sb into Sb 2 O 3 (4Sb + 3O 2 → 2Sb 2 O 3 ), as shown in Figure S6b-d.The co-existence of Sb and Sb 2 O 3 phases was confirmed by the XRD result of Sb/CNT samples at 500 o C (Figure S7a).After that, the Sb/CNT samples exhibited significant weight loss, corresponding to carbon combustion of CNT (C + O 2 → CO 2 ).In the meantime, the further oxidation of Sb 2 O 3 (2Sb 2 O 3 + O 2 → 2Sb 2 O 4 ) as well as the residual Sb (2Sb + 2O 2 → Sb 2 O 4 ) happen together. 2-4Finally, the weight of the Sb/CNT composite samples remained stable at temperatures above 600 ºC.The XRD pattern of the oxidation product of the Sb/CNT composite after the heating process confirming the Sb 2 O 4 (SbO 2 ) phase is presented in Figure S7b.The weight percentage of Sb present in the Sb/CNT composite was calculated as follows.
weights of Sb and SbO 2 respectively, and the weight(%) at 800 ºC is the assumed weight of SbO 2 .

Figure S7 .
Figure S7.XRD patterns of Sb/CNT composite samples after heating at (a) 500 ºC and (b)

Figure S8 .
Figure S8.(a) CV of CNT electrode at scan rate 0.1 mV s -1 and (b) cycling performance at

Figure S11 .
Figure S11.An equivalent circuit used for fitting of EIS data.

Figure S13 .
Figure S13.GITT curves for (a) the Sb/CNT-2 and (b) the pure Sb in the potential range of

Figure S18 .
Figure S18.Optical images of Sb and Sb/CNT-2 electrodes before and after cycling.

Figure S19 .
Figure S19.(a, b) Top-down SEM images and (c, d) cross-section SEM images of Sb

Table S1 .
The quantitative composition of Sb/CNT nanocomposites.Presumably, Sb/CNT samples only consist of Sb and C.

Table S2 .
Tabulation of R s , R SEI and R ct value of Sb/CNT-2 and Sb at different cycle no.