Robust cellulose-BaTiO3 separator with electric-field regulation effect for dendrite-free Zn-ion batteries

Aqueous Zn-ion batteries have emerged as one of the best candidates for efficient and safe energy storage systems; however, they are severely restricted by the formation of uncontrolled Zn dendrites. To address this issue, micro-fibrillated cellulose (MFC)-BaTiO3 separators are designed to regulate the Zn2+ transport behavior and achieve stable Zn anodes via coupling multiple effects. The MFC component offers a cellulose framework with robust mechanical properties and prior ion transfer channels, while the BaTiO3 particles provide dynamic electric-field regulation toward Zn2+ transfer process under different states. Due to the above-mentioned co-functions, MFC-BaTiO3 separators deliver a much better comprehensive performance than the commercial glass fiber (GF) separator. A higher Zn2+ transference number of 0.69 can be achieved in the composite separator, which is more than twice that of the GF separator. Therefore, the MFC-BaTiO3 separators are capable of achieving a much longer cycle life of more than 1050 h under 1 mA cm−2 and 1 mAh cm−2 in contrast to only 250 h observed with GF separators. Corresponding Zn//Cu cells presented a considerable Coulombic efficiency of 99.1%, and Zn//MnO2 full cells can stably work for over 500 cycles. This work provides deep insights into designing efficient, high-performance, and low-cost separators for aqueous batteries.