The earth-abundant and robust aluminum ferrite, AlFeO₃ (AFO), is mainly studied in the context of ferroelectrics. Herein, we demonstrate that AFO can be used as a stable solar absorber in photoelectrochemical cells for solar water splitting, exhibiting attractive performance. This is the first report on the photoelectrochemical activity of AFO. AFO thin-film photoelectrodes prepared by solution-processing methods are composed of vertically oriented thin nanosheets, featuring the rhombohedral symmetry (R3c) and n-type conductivity. The as-prepared AFO photoanodes generate a photocurrent density of +0.78 mA·cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE) with the photocurrent onset potential (U_onset) close to the flat band potential of 0.5 V vs. RHE in the presence of hole scavengers. Remarkably, the U_onset of AFO for solar water splitting coincides with the flat band potential as well, which is rare in n-type inorganic absorbers. We also report other properties of AFO associated with photoelectrochemical performance. AFO films exhibit a band gap energy of 2.31 eV and positive band edges with low dispersion. Moreover, the carrier lifetimes in AFO films are up to millisecond timescales under the mediation of defect traps. Based on the photoelectrochemical behavior and optoelectronic properties, we believe that AFO has great potential for application in photoelectrochemical cells.

Highly safe and efficient rechargeable lithium batteries have become an indispensable component of the intelligent society powering smart electronics and electric vehicles. This review summarizes the formation principle, chemical compositions, and theoretical models of the solid electrolyte interphase (SEI) on the anode in the lithium battery, involving the functions and influences of the electroactive materials. The discrepancies of the SEI on different kinds of anode materials, as well as the choice and design of the electrolytes are detailedly clarified. Furthermore, the design strategies to obtain a stable and efficient SEI are outlined and discussed. Last but not least, the challenges and perspectives of artificial SEI technology are briefly proposed for the development of high-efficiency batteries in practice.

Solid polymer electrolytes (SPEs) possess comprehensive advantages such as high flexibility, low interfacial resistance with the electrodes, excellent film-forming ability, and low price, however, their applications in solid-state batteries are mainly hindered by the insufficient ionic conductivity especially below the melting temperatures, etc. To improve the ion conduction capability and other properties, a variety of modification strategies have been exploited. In this review article, we scrutinize the structure characteristics and the ion transfer behaviors of the SPEs (and their composites) and then disclose the ion conduction mechanisms. The ion transport involves the ion hopping and the polymer segmental motion, and the improvement in the ionic conductivity is mainly attributed to the increase of the concentration and mobility of the charge carriers and the construction of fast-ion pathways. Furthermore, the recent advances on the modification strategies of the SPEs to enhance the ion conduction from copolymer structure design to lithium salt exploitation, additive engineering, and electrolyte micromorphology adjustion are summarized. This article intends to give a comprehensive, systemic, and profound understanding of the ion conduction and enhancement mechanisms of the SPEs for their viable applications in solid-state batteries with high safety and energy density.