Tao Liu

Sulfide all solid-state batteries represent a promising next generation energy storage technology. However, their presumed safety is challenged by the risk of thermal runaway initiating at unexpectedly low temperatures. This critical issue stems from the unstable chemical interface between the positive electrode and thiophosphate solid electrolyte, a factor often overlooked in favor of electrochemical studies. Here we demonstrate that this electrochemically formed interphase is the primary trigger for catastrophic failure, not the bulk materials. Our investigation reveals a universal two stage degradation mechanism. The first stage involves intense exothermic reactions at the interface below 160 °C, releasing heat and gases. This initiates a second stage of propagating reactions leading to thermal runaway. Crucially, we show this hazardous process can be suppressed by interface engineering. We design a stable interfacial layer using a germanium sulfur chemistry, specifically lithium germanium sulfide. This modification delivers improved thermal safety without sacrificing battery performance. Our findings have the potential to establish a forward-looking safety paradigm, shifting the focus from bulk material compatibility to interfacial stability, and provide a vital design principle for future safe solid-state batteries.

Sulfide all-solid-state batteries (ASSBs) are poised to revolutionize energy storage with unparalleled energy densities and reduced flammability risks, yet emerging studies reveal a critical safety paradox where cathode-electrolyte interactions induce thermal runaway at unexpectedly low temperatures, challenging the assumption of inherent thermal stability. While current research prioritizes electrochemical performance, the thermochemical degradation dynamics between oxide cathode and thiophosphate electrolyte remain poorly understood, with even conflicting mechanistic interpretations. Herein, leveraging multiscale calorimetry and in-situ gaseous analytical techniques, it is noted that the metastable interphase between nickel-rich cathodes and thiophosphate electrolytes, formed through electrochemically preconditioned but persistently overlooked, serve as primary triggers for exothermic cascades, a phenomenon starkly distinct from liquid electrolyte counterparts. Thermal degradation in composite cathodes evolves through dual mechanistic phases: First, delithiated cathode materials react with electrochemical precondition generated sulfur-rich species (-S-S-, -P-S-P-, and Li ₃ PS ₄ ), driving rapid heat accumulation below 160 ℃ by interphase-dominated chemistry, accompanied by gaseous emissions (SO ₂ , CO ₂ , O ₂ ); subsequently, sulfur-oxygen interdiffusion in bulk phases accelerates solid-solid exothermic reactions, driving thermal propagation and eventual runaway. This dual-stage mechanism generalizes across other sulfide systems. Crucially, it is demonstrated that the electrochemically formed interface through Ge-S bond engineering effectively suppresses thermal cascades, where the as-designed Li ₄ GeS ₄ -modified interface system achieves unprecedented thermal safety without compromising electrochemical performance. Our study establishes a new paradigm for thermal runaway causality by prioritizing interfacial thermodynamics over bulk material compatibility as the primary determinant of thermal safety—a framework fundamentally divergent from conventional liquid electrolyte batteries.

The future energy needs have triggered research interest in finding novel energy storage systems with high energy density. Lithium–sulfur batteries are regarded as one of the most promising options for the next-generation energy storage applications because of their high theoretical energy and low cost. However, the electrochemical performances of lithium–sulfur batteries are seriously compromised by the polysulfides (LiPSs) shuttling and the insulating nature of sulfur. To overcome these issues, a novel CoNi1/3Fe2O4 (CNFO) nanoparticles uniformly covered on the carbon nanotubes is now reported as an efficient functional interlayer. Benefiting from the sufficient sulfiphilic sites of the CNFO for chemically bonding with LiPSs, as well as the conductive interconnected skeleton of carbon nanotubes, this composite material showed great enhancement on the rate capability and the cycle stability of Li−S batteries. The Li−S battery using this interlayer exhibited a high initial capacity of 897 mA h g−1 and a low capacity decay of 0.063% per cycle within 250 cycles at 2 C. Meanwhile, an reversible specific capacity of 869 mA h g−1 (at 0.5 C) with high coulombic efficiency could be obtained over 100 cycles at an elevated temperature (60 °C). We speculated that the chemical adsorption of CNFO for polysulfides-anchoring is extremely critical for the performances of Li−S batteries under high temperature.

In this study, Pt catalysts were fabricated on a glassy carbon (GC) electrode Pt/GC using a potentiostatic technique at different reduction potentials in potassium hexachloroplatinate solutions with hydrochloric acid. The compositions of the catalysts were determined using energy dispersive spectroscopy (EDS), the surface morphologies were observed using scanning electron microscopy (SEM), and the crystal structure was confirmed using thin-film X-ray diffraction (XRD). The results show that all the electrodeposited Pt/GC catalysts exhibit a higher electrochemical activity for the oxygen reduction reaction (ORR) when compared with a commercial Pt/C electrode. There is an optimum electrodeposited potential (−0.15 V vs. Ag/AgCl) at which the Pt/GC electrode displays the highest electrochemical activity for the ORR due to the high-index plane and shape effect of the Pt particles. At a lower electrodeposited potential, the applied current density is high enough to form large and coarse metal particles, while at a higher electrodeposited potential, the active sites of Pt particles decrease because of its equiaxed shape.