ABSTRACT
Aqueous zinc ion batteries (ZIBs) hold great promise for large-scale energy storage; however, severe zinc dendritic growth and side reactions on the anode dramatically impede their commercial application. Herein, a Zr-based MOF (UiO-66) functionalized with a high density of sulfonic acid (âSO3 H) groups is used to modify the glass fiber (GF) separator of ZIBs, providing a unique solution for stabilizing Zn anode. Benefiting from the strong interaction between zincophilic -SO3 H and Zn2+ , this sulfonate-rich UiO-66 modified GF (GF@UiO-S2) separator not only guarantees the homogeneous distribution of ion flux, but also accelerates the ion migration kinetics. Hence, the GF@UiO-S2 separator promotes uniform Zn plating/stripping on the Zn anode and facilitates the desolvation of hydrated Zn2+ ions at the interface, which helps guide dendrite-free Zn deposition and inhibit undesired side reactions. Accordingly, the Zn||Zn symmetric cell with this separator achieves excellent cycling stability with a long cycle life exceeding 3450 h at 3 mA cm-2 . Besides, the Zn||MnO2 full cell paired with this separator delivers remarkable cyclability with 90% capacity retention after 1200 cycles. This design of metal-organic frameworks functionalized separators provides a new insight for constructing highly robust ZIBs.
ABSTRACT
Conjugated microporous polymers (CMPs) with porous structure and rich polar units are favorable for high-performance lithium-sulfur (Li-S) batteries. However, understanding the role of building blocks in polysulfide catalytic conversion is still limited. In this work, two triazine-based CMPs are constructed by electron-accepting triazine with electron-donating triphenylbenzene (CMP-B) or electron-accepting triphenyltriazine (CMP-T), which can grow on a conductive carbon nanotube (CNT) to serve as separator modifiers for Li-S batteries. CMP-B@CNT features faster ion transportation than the counterpart of CMP-T@CNT. More importantly, compared with acceptor-acceptor (A-A) CMP-T, donor-acceptor (D-A) CMP-B possesses a higher degree of conjugation and a narrower band gap, which are conducive to the electron transfer along the polymer skeleton, thus accelerating the sulfur redox kinetics. Consequently, the CMP-B@CNT functional separator endows Li-S cells with an outstanding initial capacity of 1371 mAh g-1 at 0.1 C and favorable cycling stability with a capacity degradation rate of 0.048% per cycle at 1 C for 800 cycles. This work provides insight into the rational design of efficient catalysts for advanced Li-S batteries.
