Bi-functional Janus all-nanomat separators for acid scavenging and manganese ions trapping in LiMn2O4 lithium-ion batteries

LiMn 2 O 4 -based lithium-ion batteries (LIBs) have attracted considerable attention due to their cost advantage, but industrial use has been hindered by severe capacity deterioration during cycling with LiPF 6 -based carbonate electrolytes, especially under high-temperature (55 °C) cycling conditions. Herein, a bifunctional, Janus-faced, inorganic-organic hybrid separator is demonstrated to ensure long-term cycling reversibility of LiMn 2 O 4 ||graphite LIBs. The monolithic all-nanomat separator is constructed by a bottom layer of poly ( m -phenylene isophthalamide) nanofibers by electrospinning and a top layer of interpenetrating hydroxyapatite/bacterial cellulose fibers . Benefiting from such a unique Janus configuration, the as-formed separator exhibits synergistic coupling in functions, simultaneously scavenging trace acid and mitigating the dissolution/deposition of Mn 2+ ions in batteries. Consequently, the cells with the Janus separator achieve enhanced capacity retention compared with traditional cells with the commercial polyolefin separator over 100 cycles at 55 °C. Furthermore, bulk structure and surface chemistry characterizations confirm that irreversible structural change in the LiMn 2 O 4 cathode could be avoided, and the amount of manganese on the graphite anode from the cycled cells with the Janus separator is suppressed. This work demonstrates that a composite Janus all-nanomat separator offers an unexpected route towards highly durable LiMn 2 O 4 -based LIBs.