Manipulating the diffusion energy barrier at the lithium metal electrolyte interface for dendrite-free long-life batteries.

Constructing an artificial solid electrolyte interphase (SEI) on lithium metal electrodes is a promising approach to address the rampant growth of dangerous lithium morphologies (dendritic and dead Li0) and low Coulombic efficiency that plague development of lithium metal batteries, but how Li+ transport behavior in the SEI is coupled with mechanical properties remains unknown. We demonstrate here a facile and scalable solution-processed approach to form a Li3N-rich SEI with a phase-pure crystalline structure that minimizes the diffusion energy barrier of Li+ across the SEI. Compared with a polycrystalline Li3N SEI obtained from conventional practice, the phase-pure/single crystalline Li3N-rich SEI constitutes an interphase of high mechanical strength and low Li+ diffusion barrier. We elucidate the correlation among Li+ transference number, diffusion behavior, concentration gradient, and the stability of the lithium metal electrode by integrating phase field simulations with experiments. We demonstrate improved reversibility and charge/discharge cycling behaviors for both symmetric cells and full lithium-metal batteries constructed with this Li3N-rich SEI. These studies may cast new insight into the design and engineering of an ideal artificial SEI for stable and high-performance lithium metal batteries.

Diffusion-modulated colorimetric sensor for continuous gas detection.

Due to their high sensitivity and selectivity, low cost, and good compatibility for sensor array integration, colorimetric gas sensors are widely used in hazardous gas detection, food freshness assessment, and gaseous biomarker identification. However, colorimetric gas sensors are usually designed for one-time discrete measurement because the sensing materials are entirely exposed to analytes during the sensing process. The fast consumption of sensing materials limits colorimetric sensors' applications in continuous analytes monitoring, increases the operation complexity and brings challenges for calibration. In this work, we reported a novel sensor design to prolong the lifetime of colorimetric gas sensors by engineering the gas diffusion process to preserve the sensing materials. We compared two geometries for gas diffusion control in a sensing matrix through simulation and experiment on an ammonia sensing platform. We found that the 2-dimensional gas diffusion geometry enabled a better sensor performance, including more stable and higher sensitivity and a more linear response to ammonia concentration compared to 1-dimensional gas diffusion geometry. We also demonstrated the usability of this diffusion-modulated colorimetric sensor for continuous environmental ammonia monitoring.

Decreasing Water Activity Using the Tetrahydrofuran Electrolyte Additive for Highly Reversible Aqueous Zinc Metal Batteries.

Aqueous zinc metal batteries show great promise in large-scale energy storage. However, the decomposition of water molecules leads to severe side reactions, resulting in the limited lifespan of Zn batteries. Here, the tetrahydrofuran (THF) additive was introduced into the zinc sulfate (ZnSO4) electrolyte to reduce water activity by modulating the solvation structure of the Zn hydration layer. The THF molecule can play as a proton acceptor to form hydrogen bonds with water molecules, which can prevent water-induced undesired reactions. Thus, in an optimal 2 M ZnSO4/THF (5% by volume) electrolyte, the hydrogen evolution reaction and byproduct precipitation can be suppressed, which greatly improves the cycling stability and Coulombic efficiency of reversible Zn plating/stripping. The Zn symmetrical cells exhibit ultralong working cycles with a wide range of current density and capacity. The THF additive also enables a high Coulombic efficiency in the Zn||Cu cell with an average value of 99.59% over 400 cycles and a high reversible capacity with a capacity retention of 97.56% after 250 cycles in the Zn||MnO2 full cells. This work offers an effective strategy with high scalability and low cost for the protection of the Zn metal electrodes in aqueous rechargeable batteries.

Mitigating Interfacial Mismatch between Lithium Metal and Garnet-Type Solid Electrolyte by Depositing Metal Nitride Lithiophilic Interlayer.

Solid-state lithium batteries are generally considered as the next-generation battery technology that benefits from inherent nonflammable solid electrolytes and safe harnessing of high-capacity lithium metal. Among various solid-electrolyte candidates, cubic garnet-type Li7La3Zr2O12 ceramics hold superiority due to their high ionic conductivity (10-3 to 10-4 S cm-1) and good chemical stability against lithium metal. However, practical deployment of solid-state batteries based on such garnet-type materials has been constrained by poor interfacing between lithium and garnet that displays high impedance and uneven current distribution. Herein, we propose a facile and effective strategy to significantly reduce this interfacial mismatch by modifying the surface of such garnet-type solid electrolyte with a thin layer of silicon nitride (Si3N4). This interfacial layer ensures an intimate contact with lithium due to its lithiophilic nature and formation of an intermediate lithium-metal alloy. The interfacial resistance experiences an exponential drop from 1197 to 84.5 Ω cm2. Lithium symmetrical cells with Si3N4-modified garnet exhibited low overpotential and long-term stable plating/stripping cycles at room temperature compared to bare garnet. Furthermore, a hybrid solid-state battery with Si3N4-modified garnet sandwiched between lithium metal anode and LiFePO4 cathode was demonstrated to operate with high cycling efficiency, excellent rate capability, and good electrochemical stability. This work represents a significant advancement toward use of garnet solid electrolytes in lithium metal batteries for the next-generation energy storage devices.

Achieving High Pseudocapacitance Anode by An In Situ Nanocrystallization Strategy for Ultrastable Sodium-Ion Batteries.

Conversion/alloying type anodes have shown great promise for sodium-ion batteries (SIBs) because of their high theoretical capacity. However, the poor structural stability derived from the large volume expansion and short lifetime impedes their further practical applications. Herein, we report a novel anode with a pomegranate-like nanostructure of SnP2O7 particles homogeneously dispersed in the robust N-doped carbon matrix. For the first time, we make use of in situ self-nanocrystallization to generate ultrafine SnP2O7 particles with a short pathway of ions and electrons to promote the reaction kinetics. Ex situ transmission electron microscope (TEM) shows that the average particle size of SnP2O7 decreases from 66 to 20 nm successfully based on this unique nanoscale-engineering method. Therefore, the nanoparticles together with the N-doped carbon contribute a high pseudocapacitance contribution. Moreover, the N-doped carbon matrix forms strong interaction with the self-nanocrystallization ultrafine SnP2O7 particles, leading to a stable nanostructure without any particle aggregation under a long-cycle operation. Benefiting from these synergistic merits, the SnP2O7@C anode shows a high specific capacity of 403 mAh g-1 at 200 mA g-1 and excellent cycling stability (185 mAh g-1 after 4000 cycles at 1000 mA g-1). This work presents a new route for the effective fabrication of advanced conversion/alloying anodes materials for SIBs.

Grain Boundary Defect Passivation of Triple Cation Mixed Halide Perovskite with Hydrazine-Based Aromatic Iodide for Efficiency Improvement.

Perovskites have been unprecedented with a relatively sharp rise in power conversion efficiency in the last decade. However, the polycrystalline nature of the perovskite film makes it susceptible to surface and grain boundary defects, which significantly impedes its potential performance. Passivation of these defects has been an effective approach to further improve the photovoltaic performance of the perovskite solar cells. Here, we report the use of a novel hydrazine-based aromatic iodide salt or phenyl hydrazinium iodide (PHI) for secondary post treatment to passivate surface and grain boundary defects in triple cation mixed halide perovskite films. In particular, the PHI post treatment reduced current at the grain boundaries, facilitated an electron barrier, and reduced trap state density, indicating suppression of leakage pathways and charge recombination, thus passivating the grain boundaries. As a result, a significant enhancement in power conversion efficiency to 20.6% was obtained for the PHI-treated perovskite device in comparison to a control device with 17.4%.