Unraveling the Coupling Effect between Cathode and Anode toward Practical Lithium-Sulfur Batteries

Abstract

The localized reaction heterogeneity of the sulfur cathode and the uneven Li deposition on the Li anode are intractable issues for lithium-sulfur (Li-S) batteries under practical operation. Despite impressive progress in separately optimizing the sulfur cathode or Li anode, a comprehensive understanding of the highly coupled relationship between the cathode and anode is still lacking. In this work, inspired by the Butler-Volmer equation, a binary descriptor (I_BD ) assisting the rational structural design of sulfur cathode by simultaneously considering the mass-transport index (I_mass ) and the charge-transfer index (I_charge ) is identified, and subsequently the relationship between I_BD and the morphological evolution of Li anode is established. Guided by the I_BD , a scalable electrode providing interpenetrated flow channels for efficient mass/charge transfer, full utilization of active sulfur, and mechanically elastic support for aggressive electrochemical reactions under practical conditions is reported. These characteristics induce a homogenous distribution of local current densities and reduced reaction heterogeneity on both sides of the cathode and anode. Impressive energy density of 318 Wh kg^-1 and 473 Wh L^-1 in an Ah-level pouch cell can be achieved by the design concept. This work offers a promising paradigm for unlocking the interaction between cathode and anode and designing high-energy practical Li-S batteries.

Keywords: binary descriptors; coupling effect; practical Li-S batteries; reaction heterogeneity; scalable electrodes.