Anti-dissolving cellulose-based separator for dendrite-free rechargeable aluminum batteries

Rechargeable aluminum batteries (RABs) are noteworthy due to their environmental sustainability and cost-effectiveness. However, its practical applications suffer from wilder growth of anode dendrites and greater physicochemical instability of separator triggered by corrosive ionic liquid electrolytes (ILs). This work produces a core-shell structured CCP@TiO₂ separator by introducing TiO₂ nanolayer onto commercial cellulose paper (CCP) to improve its stability by tackling the challenge of cellulose dissolution in ILs. By combining experimental and simulation studies, CCP@TiO₂ separator exhibits excellent anti-dissolving property and interfacial polarization effect, not only provides the stable anion flux and high anion transfer number of 0.29, but also facilitates the uniform distribution of the ions and electric charges at the separator/electrolyte/anode interface, thereby promoting dendrite-free Al deposition. Thus, the assembled graphite//Al battery maintains a higher discharge capacity of 90.3 mAh g⁻¹ after 1000 cycles at 0.2 A g⁻¹, compared to the 82.4 mAh g⁻¹ residual of that with glass fiber (GF) separator. Furthermore, the battery with secondary use CCP@TiO₂ separator still maintains 98 % capacity retention. Such separator engineering of insolubility of cellulose in ILs and inhibition of dendrite growth, provides an unparalleled pathway for promising alternative to GF separator and stable operation, sustainable development of RABs.