Xiaosa Xu

A single-Ni-atom-anchored COF as a catalyst is proposed to enhance the decomposition kinetics of lithium salt and construct the inorganic-rich SEI and CEI layers for anode-free solid-state lithium metal batteries.

Quasi–solid-state lithium metal batteries (QSSLMBs) are hindered by interfacial instability at high-voltage cathodes and uncontrolled lithium dendrite growth at the anode, limiting their cycling life and energy density. To overcome these challenges, we have developed a piperidine-based ionic liquid (IL) additive featuring a methylthiolation cationic segment that stabilizes the interphase of layered oxide cathodes and lithium anodes under fast charging and high-voltage conditions. These ILs preferentially oxidize to form a robust cathode-electrolyte interphase with LiF and sulfide species, which effectively suppresses dissolution of transition metal and enhances interfacial ion transport. Simultaneously, the IL-derived diverse inorganic species composite interphase at the anode improves mechanical strength and inhibits lithium dendrite growth. The resulting quasi–solid-state electrolyte demonstrates stable operation at a high voltage of 4.5 V, high mass loading of 21.6 mg cm ⁻² , high–energy density of 407 Wh kg ⁻¹ , and broad temperature range from −20° to 60°C, advancing the practical application of QSSLMBs.

Developing safe and high-voltage solid-state polymer electrolytes for high-specific-energy lithium metal batteries holds great promise. However, low ionic conductivity, limited Li⁺ transference number, narrow voltage window, and high flammability greatly hinder their practical applications. Herein, we propose a puzzle-like molecular assembly strategy to construct a solid-state polymer electrolyte via in situ polymerization. The triallyl phosphate and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate segments are spliced into the vinyl ethylene carbonate matrix to enhance anion affinity and promote lithium salt dissociation, resulting in a high ionic conductivity of 0.432 mS cm^-1 and a Li⁺ transference number of 0.70 at 25 °C. Meanwhile, the polymer electrolyte exhibits a high oxidation voltage of 5.15 V, enabled by its intrinsic high-voltage tolerance and the formation of a robust inorganic-rich interphase. As a result, the Li||LiNi_0.6Co_0.2Mn_0.2O₂ cell maintains stable performance for 300 cycles and reliably cycles even with an application-oriented mass loading of 15.8 mg cm^-2. The 2.6-Ah Li||LiNi_0.8Co_0.1Mn_0.1O₂ pouch cell reaches a high specific energy of 349 Wh kg^-1. Furthermore, the developed polymer electrolyte displays superior nonflammability and the Li||LiFePO₄ cell exhibits stable cycling for over 120 cycles at 100 °C. Both accelerating rate calorimetry and nail penetration tests verify the high safety of the pouch cells using the designed polymer electrolyte, showing the potential for practical applications.

Rational design of gas diffusion layers (GDL) is an example of a long-standing pursuit to increase the power density and reduce the cost of proton exchange membrane fuel cells (PEMFC). However, current state-of-the-art GDLs are designed by trial-and-error, which is a time-consuming endeavor. Here, we propose a closed-loop workflow of Bayesian machine learning approach to guide the design of GDL structures. With artificial neural network accelerating the calculation of anisotropic transport properties of reconstructed GDLs, Bayesian optimization algorithm identifies optimal structures in only 40 steps, maximizing the PEMFC’s limiting current density. Results suggest that the optimal porous GDL structure consists of highly orientated fibers with moderate diameters, which is successfully fabricated with a controlled electrospinning technique. The PEMFC demonstrates a high power density of 2.17 W cm^-2 and a limiting current density of ~7200 mA cm^-2, far exceeding that with commercial GDL (1.33 W cm^-2 and ~2700 mA cm^-2).

Concentration polarization-triggered dendrite growth hinders the practical application of solid-state polymer lithium batteries, which is caused by the uncontrolled anion migration in conventional dual-ion electrolytes. Single-ion conductive polymer electrolytes (SICPEs) offer a promise to mitigate dendrite growth via reducing concentration polarization and prohibiting salt depletion, yet they are highly challenging for successful implementation due to their narrow electrochemical window and poor ionic conductivity, which result from the deficient dissociation of Li⁺ polyanions and sluggish chain relaxation. Here, a cyano-containing covalent organic framework (COF) is designed to fuse with SICPEs, promising fast Li⁺ transport and remarkable interfacial stability toward high-voltage lithium-metal batteries. The electron-withdrawing cyano group on the COF facilitates the dissociation of the polyanions via ion-dipole interactions, resulting in more free-moving Li⁺. Rapid ion migration then occurs along the long-range cooperative ion transport pathways between the COF and SICPE. Additionally, the cyano group robustly bonds with transition metal ions of NCM cathodes to inhibit the catalytic decomposition of SICPE and guarantee the structural integrity of NCM. Hence, the as-prepared SICPE exhibits a significantly enhanced ionic conductivity of 9.2 × 10^-4 S cm^-1 and an improved Li⁺ transference number of 0.94 at room temperature. Accordingly, the NCM622||Li quasi-solid-state cell achieves an exceptional capacity retention of 92.0% over 1000 cycles at 0.5 C, while the cell pairing with the 4.8 V NCM622 cathode delivers a remarkable capacity of 149.5 mAh g^-1 after 200 cycles at 0.5 C. This study provides a new perspective for facilitating ionic conductivity and interface chemistry toward the practical feasibility of single-ion conductive polymer electrolytes.

Trace residual solvents in solid polymer electrolytes (SPEs) significantly affect electrolyte and interface properties, where optimal selection enhances the ionic conductivity and transference numbers. However, the solvent complexity hinders general screening methods. We establish a universal criterion linking electronic (highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO)) and macroscopic properties (dielectric constant, dipole moment, polarizability) via machine learning on an ∼10 000-solvent dataset from high-throughput density functional theory (DFT). Two solvents, N-methoxy-N-methyl-2,2,2-trifluoroacetamide and 2,2,2-trifluoro-N,N-dimethylacetamide were identified. Experimental incorporation of trace N-methoxy-N-methyl-2,2,2-trifluoroacetamide into a poly(vinylidene fluoride-co-hexafluoropropylene) matrix achieves a 4.5 V window, conductivity of 5.5 × 10^-4 S cm^-1 (30 °C), and Li⁺ transference number of 0.78. The cell retains 86.7% capacity over 500 cycles (LiFePO₄) and 98.7% after 200 cycles at 2C (LiNi_0.9Co_0.05Mn_0.05O₂), outperforming 2,2,2-trifluoro-N,N-dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide. This synergy enables balanced ion transport, wide stability, and cycling durability, advancing safer high-energy lithium metal batteries. Our integrated approach establishes a solvent screening paradigm for rational SPE design, accelerating next-generation battery development.

The practical application of quasi‐solid‐state ether‐based electrolytes is hindered by lithium dendrite formation and poor oxidation stability, which reduce the cycle life and energy density of the battery. Here, taking advantage of the ionic liquids’ high ionic interactions and structural flexibility in forming an optimized electrode/electrolyte interface, a pyrrolidinium‐based ionic liquids with trifluorotoluylation cationic segment is designed and developed. The oxidation of anions in the electrolytes is induced to form a robust inorganic LiF‐rich interphase at the cathode, thereby effectively achieving high oxidation stability and suppressing the dissolution of transition metal ions. In addition, the LiF interphases derived from the trifluorotoluylation cations increase the modulus of the anode interface and suppress the growth of lithium dendrites. Therefore, the Li‐LiFePO ₄ , Li‐LiCoO ₂ , and Li‐LiNi _0.8 Co _0.1 Mn _0.1 O ₂ full cells with the optimized electrolytes demonstrate remarkable performance improvements at high current density (10 C), a wide voltage range of 4.5 V, a high mass loading of 11.1 mg cm ⁻² , and a wide temperature range of −20–80 °C. Furthermore, a 2.66 Ah‐level pouch cell with a high‐energy‐density of exceeding 356 Wh kg ^‒1 and excellent cyclic stability demonstrates the potential of the strategy in providing a path for the practical application of quasi‐solid‐state ether‐based electrolytes in high‐energy‐density batteries.