# Graphene-Based Materials for the Separator Functionalization of Lithium-Ion/Metal/Sulfur Batteries
## 4 Conclusions and Perspective  
Graphene-based materials for separator modification in lithium-ion/metal/sulfur batteries have recently received vast attempts. In this review, we provided a comprehensive summary of the recent advancements in the preparation of graphene-based materials using techniques such as CVD, pyrolysis, and others. We also surveyed their applications as functionalized separator materials in next-generation lithium-ion/metal/sulfur batteries in Table 4. \begin{table}
\begin{tabular}{c c c c} \hline
**Separator** & **Rate Performance** & **Cycle Performance** & **Main Functions** & **Ref.** \\ \hline \multicolumn{4}{c}{Liithium-ion batteries} \\ \hline Celgard 2400 & \(135,113,83,30\) mAh g\({}^{-1}\) at 0.5, 1, 2, & \(138\) mAh g\({}^{-1}\) (0.2 C, after 100 cycles) & [101] \\  & 5 C & & \\ \hline PU@GO & \(147,121,93,55\) mAh g\({}^{-1}\) at 0.5, 1, 2, & \(154\) mAh g\({}^{-1}\) (0.2 C, after 100 cycles) & [101] \\ \hline PI@GO & \(149,137,111,49\) mAh g\({}^{-1}\) at 0.5, 1, 2, & - & (1) Improve wettability: \\  & 5 C & & (2) Provide abundant active sites; (3) Ensure excellent thermal/ mechanical stability. \\ \hline FO-g-HBPE & \(135,129,118,95\) mAh g\({}^{-1}\) at 0.5, 1, 2, & \(122\) mAh g\({}^{-1}\) (0.2 C, after 200 cycles) & [103] \\  & 5 C & & \\ \hline PVDF-co-HPF/GO & \(164,139,118,100\) mAh g\({}^{-1}\) at 0.5, 2, & \(152\) mAh g\({}^{-1}\) (0.2 C, after 200 cycles) & [104] \\  & 5 C & & \\ \hline G/PVDF-PL & \(153,148,135,111\) mAh g\({}^{-1}\) at 0.5, 2, & \(129\) mAh g\({}^{-1}\) (2 C, after 200 cycles) & [105] \\  & 5, 10 C & & Lithium-metal batteries \\ \hline PP & \(197.5,177,102,11\) mAh g\({}^{-1}\) at 0.2, & \(13\) mAh g\({}^{-1}\) (1 C, after 200 cycles) & [100] \\  & 0.5, 1, 2 C & & \\ \hline graphene/PP & \(199,184,115,28\) mAh g\({}^{-1}\) at 0.2, 0.5, & \(120\) mAh g\({}^{-1}\) (1 C, after 200 cycles) & [100] \\  & 1, 2 C & & (1) Inhibit lithium dendrites growth; (2) Provide abundant active sites; (3) Ensure excellent thermal/mechanical stability. \\ \hline  & \(1245,629,7\) & - & (1) Excellent thermal/mechanical stability. \\ \hline rGOF-A & \(147.49,100.72,78.83\) mAh g\({}^{-1}\) at 0.5, 1, 2, 5 C & \(144.63\) mAh g\({}^{-1}\) (5 C, after 100 cycles) & [126] \\ \hline PDA/Gr-CMC & \(89,77,65,39\) mAh g\({}^{-1}\) at 0.5, 1, 2, 4 C & \(130.21\) mAh g\({}^{-1}\) (1 C, after 100 cycles) & [127] \\ \hline \end{tabular}
\end{table} 
Table 4: A summary of the electrochemical performance of the graphene-based material functionalized separator in Li-ion/metal/sulfur batteries. Generally, functionalized separators utilizing porous graphene-based materials exhibit significant enhancements in conductivity, wettability, and thermal stability due to their large surface area, exceptional chemical stability, excellent mechanical properties, and controllable oxygen-containing surface functional groups. These materials also provide numerous active sites for redox reactions and Li\({}^{+}\) transfer channels while buffering the volume change of electrodes. Specifically, for lithium-ion batteries, the high wettability and abundant functional groups lead to improved Li\({}^{+}\) transfer kinetics, superior energy density, and enhanced rate/cycle performance. For lithium-metal batteries, the graphene-based interlayer mitigates local heat accumulation around irregular lithium deposition and inhibits further dendrite growth. Additionally, the outstanding mechanical strength of these materials effectively prevents separator puncturing. Finally, in lithium-sulfur batteries, the graphene-based interlayer can function as an effective sulfur adsorption agent and capture network, as well as an activator for dead sulfur. However, there are still great challenges for the industrial production of separators assembled with a graphene-based interlayer. Regarding preparation, it is quite challenging to make sufficient integration of low cost, minimal pollution, high yield, and high quality.