Yan Zhang

Silicon is considered one of the most promising next-generation anode materials for lithium-ion batteries (LIBs) due to its exceptionally high theoretical capacity, but its large volume changes during cycling demand careful composite design. In this work, Si/carbon@Li ₄ Ti ₅ O ₁₂ @graphite composites containing 24 wt% silicon were synthesized via two scalable, one-step methods (mechanomilling and speed-mixing) to assess the impact of processing and component distribution on electrochemical performance. Physicochemical and electrochemical analyses revealed that the mechanomilled Si/carbon@LTO composite without graphite (M-SLC) outperformed all others, delivering ∼870 mAh g ⁻¹ at C/10 and 430 mAh g ⁻¹ at 10 C. Its superior performance stemmed from excellent component integration, low surface area, fast Li⁺ diffusion, and suppression of crystalline Li _3.75 Si formation, confirmed by EIS, in situ- Raman, and XPS. In contrast, the other composites suffered from graphite amorphization and poor component integration. These results highlight the importance of carefully selecting an appropriate synthesis method and understanding correlations between the electrode’s physicochemical and electrochemical properties in order to enhance the development of high-performance silicon anodes.

Tuning the lithium salts’ chemistry is a promising approach to achieve a competitive solid polymer electrolyte (SPE). Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) has been extensively investigated due to its excellent thermal and electrochemical stability. On the other hand, poly(ethylene oxide) (PEO) remains one of the most studied polymer matrices owing to its high solvating power, which promotes lithium salt dissociation. However, the low lithium transference number (T Li+) of LiTFSI/PEO (ca. 0.2) system is a handicap for high-performance SPE, mainly attributed to the high anion diffusion. In this work, a series of five lithium salts were designed by replacing one -CF3 group of LiTFSI with a dialkylamine moiety bearing different alkyl chain lengths. Ion coordination environments between PEO, cations and anions, along with their transport properties, were systematically investigated through experimental and computational approaches. The results demonstrate that anion diffusion can be effectively suppressed by introducing bulky alkyl groups, with the improved T Li+ (ca. 0.5) primarily attributed to steric hindrance rather than long-range interactions between the anion and the PEO matrix.

Sodium (Na) metal is a highly attractive anode material for next-generation batteries due to its natural abundance and low cost, but its practical use is limited by the poor reversibility of the Na plating/stripping process and instability during cycling. Herein, nanoscale metallic films (Ti, Ni, Ge and In) with different thicknesses are grown by magnetron sputtering to coat commercial stainless steel 316L current collectors, and the substrate-dependent Na plating/stripping characteristics are thoroughly explored. The results reveal that sodiophilic interphases can be achieved by in situ formation of M–Na (M = Ge, In) alloys. A controlled protocol is developed to electrochemically form ultrathin Ge–Na or In–Na alloy buffer layers in the first cycle prior to Na plating, serving as pillars for a stable subsequent Na metal deposition and boosting the buildup of a highly efficient thin Na metal anode. Among the tested materials, 50 nm thick In coatings exhibit the most stable long-term plating/stripping process. These findings demonstrate a simple and effective interfacial engineering strategy to enhance the performance of Na metal anodes, providing a pathway toward safer and long-lasting sodium metal batteries.

Solid polymer electrolytes (SPEs) with both excellent processability and flexibility have been deemed as an auspicious alternative to develop safe solid-state lithium metal (Li°) batteries (SSLMBs). The electrochemical performance of SSLMBs is ultimately associated with the nature of the Li-salt anion and the widely used bis(trifluoromethanesulfonyl)imide anion (TFSI) is “slippery” due to its perfluorinated nature and therefore highly mobile, which leads to severe polarization upon battery cell charge/discharge cycles. In this work, we report on a new type of chiral salts, synthesized from commercially available camphorsulfonic acid, used in poly(ethylene oxide) (PEO)-based SPEs. The impact of the chirality of the anions on the fundamental physical properties of the SPEs is extensively studied in terms of thermal stability, phase transition and ionic conductivity, etc. We demonstrate that the resulting SPEs exhibit agreeable ionic conductivities (ca. 10 ^‒4 S cm ^‒1 ) accompanied by high cation transference numbers (ca. 0.5) at 70 °C. Whether either the R or the S enantiomers are used the ion transport properties are the same, as expected, but rather surprisingly the artificial racemic mixture is within the errors of the measurements just as conductive. We discuss how this opens a new avenue to design novel salts for reaching high-performant SSLMBs.

The influence of electrical excess charges on the crystallization from supersaturated aqueous sodium chloride solutions is reported. This is accomplished by efflorescence studies on single levitated microdroplets using optical and electrodynamic levitation. Specifically, a strong increase in efflorescence humidity is observed as a function of the droplet’s negative excess charge, ranging up to −2.1 pC, with a distinct threshold behavior, increasing the relative efflorescence humidity, at which spontaneous nucleation occurs, from 44% for the neutral microparticle to 60%. These findings are interpreted by using molecular dynamics simulations for determining plausible structural patterns located near the particle surface that could serve as suitable precursors for the formation of critical clusters overcoming the nucleation barrier. These results, facilitating heterogeneous nucleation in the case of negatively charged microparticles, are compared to recent work on charge-induced nucleation of neat supercooled water, where a distinctly different nucleation behavior as a function of droplet charge has been observed.

Polymer-rich composite electrolytes with lithium bis(fluorosulfonyl)imide/poly(ethylene oxide) (LiFSI/PEO) containing either Li-ion conducting glass ceramic (LICGC) or inorganic Al₂O₃ fillers are investigated in all-solid-state Li–S cells. In the presence of the fillers, the ionic conductivity of the composite polymer electrolytes (CPEs) does not increase compared to the plain LiFSI/PEO electrolyte at various tested temperatures. The CPE with Al₂O₃ fillers improves the stability of the Li/electrolyte interface, while the Li–S cell with a LICGC-based CPE delivers high sulfur utilization of 1111 mAh g^–1 and areal capacity of 1.14 mAh cm^–2. In particular, the cell performance gets further enhanced when combining these two CPEs (Li | Al₂O₃–CPE/LICGC–CPE | S), reaching a capacity of 518 mAh g^–1 and 0.53 mAh cm^–2 with Coulombic efficiency higher than 99% at the end of 50 cycles at 70 °C. This study shows that the CPEs can be promising electrolyte candidates to develop safe and high-performance all-solid-state Li–S batteries.

Nanoparticles exhibiting zero backscattering but a large scattering cross section in the forward direction should play a key role as light diffracting elements in photonic devices like solar cells. Using Mie theory we address lossless dielectric spheres that were recently reported to possess a magnetodielectric response to the illuminating wave, and analyze their scattering cross section together with their zero-backwards scattering conditions. We show that there is an optimum particle refractive index ( m = 2.47), which yields maximum forward scattering without backwards scattering of light.

Structural motifs of pre-nucleation clusters prepared in single, optically levitated supersaturated aqueous aerosol microparticles containing CaBr2 as a model system are reported. Cluster formation is identified by means of X-ray absorption in the Br K-edge regime. The salt concentration beyond the saturation point is varied by controlling the humidity in the ambient atmosphere surrounding the 15–30 μm microdroplets. This leads to the formation of metastable supersaturated liquid particles. Distinct spectral shifts in near-edge spectra as a function of salt concentration are observed, in which the energy position of the Br K-edge is red-shifted by up to 7.1 ± 0.4 eV if the dilute solution is compared to the solid. The K-edge positions of supersaturated solutions are found between these limits. The changes in electronic structure are rationalized in terms of the formation of pre-nucleation clusters. This assumption is verified by spectral simulations using first-principle density functional theory and molecular dynamics calculations, in which structural motifs are considered, explaining the experimental results. These consist of solvated CaBr2 moieties, rather than building blocks forming calcium bromide hexahydrates, the crystal system that is formed by drying aqueous CaBr2 solutions.

Electron attachment to pentafluorobenzonitrile (C₆F₅CN) and pentafluoronitrobenzene (C₆F₅NO₂) is studied in the energy range 0–16 eV by means of a crossed electron-molecular beam experiment with mass spectrometric detection of the anions. We find that pentafluoronitrobenzene exclusively generates fragment anions via dissociative electron attachment (DEA), while pentafluorobenzonitrile forms a long lived parent anion within a narrow energy range close to 0 eV and additionally undergoes DEA at higher energies. This is in contrast to the behaviour of the non-fluorinated analogues as in nitrobenzene the non-decomposed anion is formed while in benzonitrile only DEA is observed. The associated reactions involve simple bond cleavages but also complex unimolecular decompositions associated with structural and electronic rearrangement also resulting in the deterioration of the cyclic structure.