Functionalized WS₂-MWCNT Hybrid Nanostructures for Li-Ion Battery Anodes— Towards Binder-Free Approach

Tungsten disulfide (WS₂), among various transition metal dichalcogenides (TMDs), has garnered significant attention as a potential intercalation host material for lithium-ion batteries (LIBs). This interest is attributed to its unique graphite-like layered structure, high theoretical specific capacity of 433 mAh g^-1, relatively low cost, and excellent charge transport and mechanical properties [1]. However, WS₂ based anodes face several challenges, including pulverization, low electronic and ionic conductivities, an unstable solid-electrolyte interphase (SEI) layer, and thermal runaway issues, which limit their application in practical devices [1]. To address the technical challenges of WS₂-based anodes in LIBs, recent research has focused on hybrid nanostructure-based anodes [2–4]. We demonstrate the effective functionalization of WS₂ nanoflakes and MWCNT (multiwalled carbon nanotube) bundles using the n-type semiconducting polymer PCBM (Phenyl-C61-butyric acid methyl ester). This functionalization facilitates the formation of hybrid nanostructures, resulting in significantly enhanced performance of WS₂ anodes in LIB applications. PCBM functioned as a conductive bridge between the WS₂ hexagonal nanoflakes and the MWCNT bundles, thereby significantly reducing junction resistance. Additionally, PCBM functionalization mitigated the agglomeration and pulverization of the WS₂ nanoflakes. The functionalization of WS₂ and MWCNTs with PCBM is confirmed by the FTIR and Raman spectroscopies. The demonstrated WS₂-PCBM/MWCNT hybrid nanostructures based anodes were cycled for 500 cycles at current density of 1.0 A g^-1, where has shown a stable average discharge specific capacity of ~485.73 mAh g^-1 with coulombic efficiency (CE) of close to 100% [5]. In addition, the PVDF binder-free WS₂-PCBM/MWCNT hybrid nanostructure-based anode has displayed an average discharge specific capacities of ~1224 mAh g^-1 for up to 25 cycles at current density of 0.1 A g^-1 with coulombic efficiency of ~99.99%. Thus, our work offers new avenues to explore the utility of PCBM as a carbon conductive to boost the performance of the WS₂ based anodes for Li-ions and other metal-ion batteries. Additionally, our findings offer a groundbreaking and scalable methodology for the development of traditional binder-free electrodes.<br/><br/>References:<br/><br/>[1] Y. Song, S. Bai, L. Zhu, M. Zhao, D. Han, S. Jiang, Y. N. Zhou, <i>ACS Appl. Mater. Interfaces</i> 2018, <i>10</i>, 13606.<br/>[2] Y. Wang, D. Kong, W. Shi, B. Liu, G. J. Sim, Q. Ge, H. Y. Yang, <i>Adv. Energy Mater.</i><b> </b>2016, <i>6</i>, 1.<br/>[3] H. Xu, L. Sun, W. Li, M. Gao, Q. Zhou, P. Li, S. Yang, J. Lin, <i>Chem. Eng. J.</i> 2022, <i>435</i>, 135129.<br/>[4] S. Ahmad, D. Copic, C. George, M. De Volder, <i>Adv. Mater.</i> 2016, <i>28</i>, 6705.<br/>[5]<b> </b>B. Mondal, A. Azam, S. Ahmad, <i>Energy and Fuels</i> 2023, <i>37</i>, 16105.