Preparation of macroporous lithium iron manganese phosphate/carbon composites via sol-gel process accompanied by phase separation

Abstract

Macroporous lithium manganese iron phosphate/carbon (LiFe_0.9Mn_0.1PO₄/C) has been successfully synthesized via a sol-gel process accompanied by phase separation. Poly (ethylene oxide) (PEO) acts as a phase separation inducer, while polyvinylpyrrolidone (PVP) synergistically regulates the morphology of the gel skeleton and serves as a reducing agent. Propylene oxide (PO) works as a proton scavenger to initiate the homogeneous gelation and modify the macrostructure. An appropriate amount of PEO, PVP and PO led to the formation of xerogel monoliths characterized by a three-dimensional co-continuous skeleton and interconnected macropores. The amorphous xerogel upon heat treatment at 400 °C for 2 h under a N₂ atmosphere, formed carbon-coated LiFe_0.9Mn_0.1PO₄/C crystals with excellent crystallinity and uniform elemental distribution. The resultant macroporous LFMP/C has a discharge capacity of 113.43 mA h g^− 1 at 0.1 C, with a first coulombic efficiency of 90.1% and excellent capacity recovery rate after high-rate tests.