A variety of carbon-coated FeS2 anodes: FeS2@CNT with excellent lithium-ion storage performance

Modulation of the Oxidation End-Product Toward Polysulfides-Free and Sustainable Lithium-Pyrite Thermal Batteries

The FeS₂ has abundant reserves and a high specific capacity (894 mAh g^-1 ), commonly used to fabricate Li-FeS₂ primary batteries, like LiM_x -FeS₂ thermal batteries (working at ≈500 °C). However, Li-FeS₂ batteries struggle to function as rechargeable batteries due to serious issues such as pulverization and polysulfide shuttling. Herein, highly reversible solid-state Li-FeS₂ batteries operating at 300 °C are designed. Molten salt-based FeS₂ slurry cathodes address the notorious electrode pulverization problem by encapsulating pulverized particles in time with e^- and Li⁺ flow conductors. In addition, the solid electrolyte LLZTO tube serves as a hard separator and fast Li⁺ channel, effectively separating the molten electrodes to construct a liquid-solid-liquid structure instead of the solid-liquid-solid structure of LiM_x -FeS₂ thermal batteries. Most importantly, these high-temperature Li-FeS₂ solid-state batteries achieve FeS₂ conversion to Li₂ S and Fe at discharge and further back to FeS₂ at charge, unlike room-temperature Li-FeS₂ batteries where FeS and S act as oxidation products. Therefore, these new-type Li-FeS₂ batteries have a lower operating temperature than Li-FeS₂ thermal batteries and perform highly reversible electrochemical reactions, which can be cycled stably up to 2000 times with a high specific capacity of ≈750 mAh g^-1 in the prototype batteries.

Carbon-Coated ZnS-FeS2 Heterostructure as an Anode Material for Lithium-Ion Battery Applications

The construction of carbon-coated heterostructures of bimetallic sulfide is an effective technique to improve the electrochemical activity of anode materials in lithium-ion batteries. In this work, the carbon-coated heterostructured ZnS-FeS₂ is prepared by a two-step hydrothermal method. The crystallinity and nature of carbon-coating are confirmed by the investigation of XRD and Raman spectroscopy techniques. The nanoparticle morphology of ZnS and plate-like morphology of FeS₂ is established by TEM images. The chemical composition of heterostructure ZnS-FeS₂@C is discovered by an XPS study. The CV results have disclosed the charge storage mechanism, which depends on the capacitive and diffusion process. The BET surface area (37.95 m²g^-1) and lower R_ct value (137 Ω) of ZnS-FeS₂@C are beneficial to attain higher lithium-ion storage performance. It delivered a discharge capacity of 821 mAh g^-1 in the 500th continuous cycle @ A g^-1, with a coulombic efficiency of around 100%, which is higher than the ZnS-FeS₂ heterostructure (512 mAh g^-1). The proposed strategy can improve the electrochemical performance and stability of lithium-ion batteries, and can be helpful in finding highly effective anode materials for energy storage devices.