Multifunctional Separator Enabled by a High Phosphorus Content Additive for Ni-Rich Transition Metal Oxide Batteries

Ni-rich transition metal oxide batteries, generally represented as LiNix Co y Mn1-x-y (Ni-rich NMC), where x >= 0.5 and y < 0.5, have drawn much attention recently due to their high energy density and high discharge capacity (similar to 200 mAh g(-1)). However, the Ni-rich NMC battery frequently suffers from the interfacial issues and safety concerns attributed to the reduction of the Ni element during cycling. In this work, a multifunctional separator employing a high phosphorus content additive, i.e., dimethyl methylphosphonate (Fyrol DMMP), is prepared using a phase inversion method. The synthesized separator reveals a superior electrolyte uptake of 2213%, which is nearly 10 times higher than that of the commercial polypropylene separator. A key feature of the synthesized separator is the capability to generate a uniform and stable cathode-electrolyte interphase with a thickness of similar to 5 nm, consisting of LiF, on subsequent cycles. Consequently, the cycling stability of the NMC cell is enhanced exhibiting a high and consistent Coulombic efficiency of similar to 99%, and the capacity fading is decreased from 18 to 9.5% during 100 cycles (at C-rate). Furthermore, the stabilized interphase contributes to a decrease in impedance from similar to 154 to similar to 59.2 omega. The synthesized separator also displays strong thermal stability and flame-retardant property. Ignitions were attempted during the combustion test, but any flames were promptly extinguished ( < 1.0 s). This study presents an effective approach to tackle both the interfacial issues and safety concerns of Ni-rich NMC batteries at the same time.

Automated summary

Ni-rich NMC batteries have attracted much attention due to their high energy density and capacity. However, they often suffer from interfacial issues and safety concerns. In this study, a multifunctional separator was prepared using a high phosphorus content additive. The synthesized separator showed improved electrolyte uptake and formed a uniform and stable cathode-electrolyte interphase. This enhanced the cycling stability and Coulombic efficiency of the NMC cell, while also providing thermal stability and flame-retardant properties.