# Metal–Organic Framework-Derived Co9S8 Nanowall Array Embellished Polypropylene Separator for Dendrite-Free Lithium Metal Anodes

## TL;DR

This paper introduces a new separator design using metal-organic frameworks to improve lithium metal anode performance by enabling uniform lithium ion deposition and stable battery cycling.

## Contribution

A novel MOF-derived Co9S8 nanowall array on polypropylene separators is proposed for dendrite-free lithium metal anodes.

## Key findings

- The Co9S8-PP separator enables stable Li//Cu half-cell cycling for 2000 hours at 1 mA cm−2 and 1 mAh cm−2.
- Li//LiFePO4 full cells with the separator show 74% capacity retention after 1000 cycles at 0.2 C.
- The design offers fast charge transfer and uniform Li+ ion deposition due to high ionic conductivity and morphology.

## Abstract

Developing a reasonable design of a lithiophilic artificial solid electrolyte interphase (SEI) to induce the uniform deposition of Li+ ions and improve the Coulombic efficiency and energy density of batteries is a key task for the development of high-performance lithium metal anodes. Herein, a high-performance separator for lithium metal anodes was designed by the in situ growth of a metal–organic framework (MOF)-derived transition metal sulfide array as an artificial SEI on polypropylene separators (denoted as Co9S8-PP). The high ionic conductivity and excellent morphology provided a convenient transport path and fast charge transfer kinetics for lithium ions. The experimental data illustrate that, compared with commercial polypropylene separators, the Li//Cu half-cell with a Co9S8-PP separator can be cycled stably for 2000 h at 1 mA cm−2 and 1 mAh cm−2. Meanwhile, a Li//LiFePO4 full cell with a Co9S8-PP separator exhibits ultra-long cycle stability at 0.2 C with an initial capacity of 148 mAh g−1 and maintains 74% capacity after 1000 cycles. This work provides some new strategies for using transition metal sulfides to induce the uniform deposition of lithium ions to create high-performance lithium metal batteries.