A functional MXene/cellulose nanofibers separator for high-performance dendrite-free zinc anode under harsh conditions

Abstract

Aqueous zinc-ion batteries (AZIBs) show great potential for mass energy storage because of their intrinsic plentifulness and security. Nevertheless, the development of zinc dendrites is still a major challenge for the practical industrialisation of AZIB, especially under the demanding conditions of elevated current density and high temperatures. To combat this situation, we developed an ultrathin separator composed of cellulose nanofibers and MXene (noted as CM-15 separator) with a thickness of only 27 μm. The strong zincophilic characteristics and outstanding electrical/thermal conductivity of MXene make them suitable for use as an ion pump to expedite the transmission of Zn2+ through the electrolyte, which significantly increases the zinc ion transfer number and results in the deposition of homogeneous Zn nuclei and dendritic-free Zn. As a result, the symmetric battery equipped with a CM-15 separator enabled excellent dendrite free plating/stripping behavior, high coulomb efficiency (97.7 %) and cumulative plated capacity of 4.8 Ah/cm2 at 80 mA/cm2 at room temperature and as well as sustained operation for at least 300 h under 60 °C. More impressively, the Zn-MnO2/CNT battery equipped with a CM-15 separator achieved 72.6 % capacity retention after 10,000 cycles at 2 A/g under room temperature and 92.1 % capacity retention after 200 cycles at 1 A/g under 60 °C. Our research confirms the potential of functional separators to promote the application of AZIBs, especially under demanding conditions.