Polyfluorinated crosslinker-based solid polymer electrolytes for long-cycling 4.5 V lithium metal batteries

Abstract

Solid polymer electrolytes (SPEs), which are favorable to form intimate interfacial contacts with electrodes, are promising electrolyte of choice for long-cycling lithium metal batteries (LMBs). However, typical SPEs with easily oxidized oxygen-bearing polar groups exhibit narrow electrochemical stability window (ESW), making it impractical to increase specific capacity and energy density of SPE based LMBs with charging cut-off voltage of 4.5 V or higher. Here, we apply a polyfluorinated crosslinker to enhance oxidation resistance of SPEs. The crosslinked network facilitates transmission of the inductive electron-withdrawing effect of polyfluorinated segments. As a result, polyfluorinated crosslinked SPE exhibits a wide ESW, and the Li|SPE|LiNi0.5Co0.2Mn0.3O2 cell with a cutoff voltage of 4.5 V delivers a high discharge specific capacity of ~164.19 mAh g−1 at 0.5 C and capacity retention of ~90% after 200 cycles. This work opens a direction in developing SPEs for long-cycling high-voltage LMBs by using polyfluorinated crosslinking strategy.

Improving Ion Conductivity in Polymer Blend Electrolytes by Tuning Microdynamics and Interfaces

“…Definitely the chemical stability of the interface between polymer electrolyte and electrodes needs to be improved to enhance the cyclability. Recent advances on designing SPEs for long-cycling batteries include polyfluorinated cross-linking, composite of dielectric nanowires and PVDF matrix to form heterojunction structure, and combination of high molecular weight PVDF and stable interface layer . In addition, the role of Li-ion salts needs to be carefully evaluated since it was found that a significant change of electrochemical stability window of polymer electrolytes can occur depending upon the formation of polymer/salt complexes .…”

Polymer-based electrolytes for solid-state lithium batteries with a wide operating temperature range

“…19 However, the effect of high/low temperatures on polymer-based electrolytes is multi-dimensional, not only including the physical and electrochemical properties of electrolytes (low temperature ionic conductivity and thermal stability), but also relating to the electrode–electrolyte interface compatibility (interface stability and destruction). 20–23 Numerous studies have attempted to overcome these limitations. For instance, Yu and coworkers demonstrated that the ionic conductivity of polymer-based electrolytes could be improved by introducing different dipoles; the as-prepared poly(vinyl ethylene carbonate) (PVEC) based polymer electrolyte contained two kinds of dipoles (CO and C–O) and achieved a high ionic conductivity of 0.4 mS cm −1 @−15 °C.…”

Nitrogen Ion Implantation-Modified Cu Substrate for Stable Lithium Metal Anode

“…Due to the high theoretical specific capacity (3860 mAh g –1 ) and the most negative potential (−3.04 V vs SHE), lithium metal anode (LMA) , has been regarded as a most welcomed anode candidate for the high-energy-density battery . However, the development of LMA is severely limited by the uncontrollable Li dendrite growth and the unstable solid electrolyte interphase (SEI), which requires strategy innovation. − The capabilities and interface of the substrate have a critical impact on the reversibility of LMA in tutoring the Li nucleation and deposition behavior, especially in anode-free lithium metal battery configurations. − The copper (Cu) foil, as the only commercialized negative current collector for Li-ion batteries, possesses many advantages, including ideally good conductivity, mechanical properties, low cost, and manufacturing compatibilities.…”