Exploring LiFe0.4Mn0.6PO4 as a Cathode Material for Nonaqueous Aluminum-Ion Batteries.

Abstract

This research provides a pioneering demonstration of LiFe_0.4Mn_0.6PO₄@C (LFMP@C) as a cathode material for rechargeable aluminum-ion batteries (AIBs). The composite delivers an initial discharge capacity of 156.5 mAh g^-1 at 200 mA g^-1, with 148.2 mAh g^-1 retained after 500 cycles. The Li⁺/Al³⁺ (de)intercalation mechanisms and their structural impacts on the LFMP lattice are systematically investigated through density functional theory, inductively coupled plasma optical emission spectroscopy, X-ray photoelectron spectroscopy, and ex situ X-ray diffraction. The results show that aluminum and lithium ions successfully intercalate into the LFMP lattice and participate in the electrochemical reaction, while Fe and Mn undergo reversible valence state changes. The strong electrostatic interactions between Al³⁺ and the host lattice (hindering ion migration) as well as Li⁺ trapping by the acidic electrolyte jointly contribute to rapid capacity decay during initial cycles. Nevertheless, the LFMP@C composite demonstrates promising cycling stability.