Two-Step Activations and Liquid Metal Fortified Copper Substrate on Corrosion Tolerance in Anode-Free Lithium–Sulfur Battery

Capacity fading caused by polysulfide (PS) shuttling is a challenge in lithium–sulfur batteries. Anode-free lithium–sulfur batteries (AFLSBs) with zero excess Li are limited by dendrite and PS-induced reactions from soluble PS-shuttling, which affect cycle life. Here, the Cu current collector (Cu-CC) prone to PS-induced corrosion was studied using a liquid metal, GaIn, as a coating material. GaIn with self-healing properties fortifies uniform nucleation sites, alleviates dendrite growth, and overcomes the corrosion of Cu-CC. Operando confocal OM, in situ XRD, XPS, CV, and morphological-examinations revealed the mitigation of dendritic Li growth and alloy–dealloying mechanisms. The GaIn-Cu-CC under an asymmetric cell with a PS additive exhibits insignificant heat evolution and improved Li reversibility compared to Cu-CC, as revealed by operando heat evolution tests. Ex situ PS treatment resulted in severe corrosion in Cu-CC with substantial morphological alterations, and Cu2S formation was confirmed by XPS and synchrotronic XAS wavelet transform. The extent of in situ PS on AFLSB’s cell was studied under single-step activation (STA) and two-step activation (TSA) of the Li2S cathode. The STA-cathode delivers a capacity retention (CR) of 54.12% and 63.11% using Cu-CC and GaIn-Cu-CC, respectively, after 200 cycles. TSA of the cathode upon GaIn-Cu-CC leads to a 50.11% CR after 250 cycles. The adverse effect of PS on Cu-CC resulted in 33.15% CR after 100 cycles. Formulating a corrosion-tolerant and uniform nucleation site from a coating material in a facile approach enhances the feasibility of Cu-CC in sulfur-rich environments, making capable AFLSBs.