Battery Electrode Engineering Enables Fast Charging LMFP Cells Without Carbon-Coated Foil

Lithium manganese iron phosphate (LiMn_xFe_1-xPO₄, LMFP) has emerged as a promising Li-ion battery cathode material due to its high voltage, thermal stability, and cycle life, yet its intrinsically low electronic and ionic conductivity limits high-rate performance and thus usefulness in fast-charge applications such as electric vehicles. Here, we evaluate key electrode design aspects, investigating the interplay between calendering density and current collector priming (carbon-coating) on the fast cycling performance of LMFP cathodes. For electrodes on pristine aluminium, calendering to high density induced particle embedment into the foil (quantified via segmentation of cross-sectional microscope images), reducing interfacial resistance while enhancing both rate capability and long-term cycling stability. In contrast, performance of electrodes on C-coated aluminium exhibited minimal sensitivity to densification. Surprisingly, at sufficiently high calendering pressure (achieving density ≥ 2.5 g cm^-3), the carbon coating provided no advantage to high-rate performance, in stark contrast with conventional understanding, and cells manufactured with pristine Al achieved fast charging from 10% to 80% SOC in just over 15 min, a key milestone for this chemistry. These findings establish a mechanistic understanding of how density and interfacial properties govern transport and electrochemical behavior in LMFP cells, providing practical guidance for optimized electrode structures.