Shu Zhang

Despite the considerable promise of solid polymer electrolytes (SPEs) for enabling high‐energy‐density and intrinsically safe lithium metal batteries, their practical deployment in cold environments remains hindered by sluggish Li ⁺ transport at sub‐zero temperatures. Herein, methyl trifluoromethanesulfonate (TMS) is introduced as an ionic microenvironment regulator into a cationic poly(ionic liquid) solid electrolyte, enabling enhanced Li ⁺ transport under extreme low‐temperature conditions. Notably, TMS not only enhances lithium salt dissociation but also induces an anion‐trapping effect by modulating the local charge distribution of the polycationic backbone, thereby facilitating uniform lithium deposition. As a result, the optimized cationic poly(ionic liquid) solid electrolyte (PIL‐TMS ₁ ) enables stable cryogenic operation of high‐voltage Li||PIL‐TMS ₁ ||LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and Li||PIL‐TMS ₁ ||LiFePO ₄ batteries, delivering capacity retentions of 89.8% after 500 cycles and 80.1% after 800 cycles at −15°C, respectively. This work presents an effective strategy for designing low‐temperature solid‐state lithium metal batteries through additive‐regulated anion trapping and accelerated Li ⁺ transport.

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.

All-solid-state lithium batteries for electric vehicles require high specific power, challenged in thick negative electrodes by fragile conducting networks during volume changes and dendrite growth at high currents. We propose an In_0.38Sn_0.33Bi_0.29 ternary alloy negative electrode creating a mixed ionic-electronic conducting continuum that overcomes these limitations. The stepwise formation of multiple phases with sufficient mechanical robustness during Li-alloying effectively stabilizes the ionic and electronic conducting percolation by relieving stress concentration and minimizing crack propagation. The unique reversibility of the multiple phase changes during lithiation/delithiation ensures stable cycling performance. The In_0.38Sn_0.33Bi_0.29 negative electrode exhibits a high capacity of ~ 724 mAh g⁻¹ and a critical current density of 150 mA cm⁻² at 5.0 mAh cm^–2. The In_0.38Sn_0.33Bi_0.29 | |LiCoO₂ full cell with industry-level mass loading (6.49 mAh cm^–2) can retain 87.5% capacity over 1300 cycles at 4.0 C, delivering a jellyroll specific energy of 203.1 Wh kg⁻¹ and 670.6 Wh L⁻¹ at 5.0 C. The fast-charging capability is further validated by large-format pouch cells. The design principles can be extended to other negative electrode designs for solid-state batteries.

The instability of lithium salts within the electrolyte has consistently posed a significant challenge to next-generation lithium-ion batteries. The most commercialized lithium hexafluorophosphate (LiPF₆) suffers from ligand abstraction, causing excessive formation of erosive HF at elevated temperatures. Another promising salt of lithium difluoro(oxalato)borate (LiDFOB), featuring hydrophilic/lithiophilic carbonyl groups, possesses high moisture sensitivity and insufficient dissociation in electrolytes. Herein, we propose an anion-skeleton editing strategy that increases the fluoride ion affinity of the parent Lewis acid while reducing its interaction with H⁺/Li⁺ by replacing the carbonyl groups in DFOB^- anion with hydrophobic/lithiophobic -CF₃ groups. The lithium salt alternative, lithium 2,2-difluoro-4,4,5,5-tetrakis(trifluoromethyl)−1,3,2-dioxaborolan-2-uide (LiDFTFB), has been successfully synthesized and serves as a well-balanced salt in terms of moisture stability, thermal stability, electrochemical stability, ionic conductivity, solubility, and aluminum foil passivation, outperforming LiPF₆ and LiDFOB. Even at an elevated temperature of 50 °C, LiDFTFB endows 1 Ah graphite | |LiNi_0.8Mn_0.1Co_0.1O₂ pouch cells with enhanced cycling stability (81.7% retention after 650 cycles, 0.5 C charge and 0.5 C discharge, 1 C = 200 mA g^-1). This work emphasizes the critical importance of strategically modulating anion chemistries to promote the development of the next-generation lithium-ion batteries.

We investigated the power density spectrum (PDS) and time lag of ultraluminous X-ray sources (ULXs) observed by XMM-Newton. We determined the PDSs for each ULX and found that five of them show intrinsic variability due to obvious quasi-periodic oscillations (QPOs) of mHz–1 Hz, consistent with previous reports. We further investigated these five ULXs to determine their possible time lag. The ULX QPOs exhibit a soft time lag that is linearly related to the QPO frequency. We discuss the likelihood of the ULX QPOs being type-C QPO analogs, and the time lag models. The ULXs might harbor intermediate-mass black holes if their QPOs are type-C QPO analogs. We suggest that the soft lag and the linearity may be due to reverberation.