(Invited) Surface Modified Polypropylene Membrane for High Performance Lithium Metal Coin and Pouch Cell Batteries

Abstract

For the advanced Li metal batteries, lithium (Li) metal is considered as anode electrode because of its lowest redox potential (–3.04 V vs. standard hydrogen electrode), highest theoretical specific capacity (3,860 mAh g-1), and the low density (0.59 g cm-3). Nevertheless, Li metal anode seriously impede its practical use for viable market because of short-circuit based safety risk associated to dendrite growth and low Coulombic efficiency. Understanding those fundamental challenges, we designed a multifunctional tri-layer membrane by percolating a layer of a polydopamine (PDA) followed by depositing graphene-carboxymethyl cellulose (Gr-CMC) on the top of polypropylene (PP) separator, hypothesizing to improve the cycle stability and performance of Li metal electrodes. The novel, new trilayer comprising Gr-CMC layer of the designed separator depicted an excellent electrolyte wettability, an additional capacity of Li storage and an enhanced electrical conductivity. In Li/Cu half-cell the Coulombic efficiency was significantly enhanced over 200 cycles after implementing PDA/Gr-CMC separator. LiFePO4 cathode vs Li full cell with trilayer separator directed to long term cycle retention (1000 cycles) with enhanced rate capability. Apart from room temperature, electrochemical stability at 0 oC demonstrated the sanguine potential of PDA/Gr-CMC separator for practical Li-metal batteries. Beyond coin cells, pouch cell studies and cycling abilities will be demonstrated.