Mechanistic Study on Artificial Stabilization of Lithium Metal Anode via Thermal Pyrolysis of Ammonium Fluoride in Lithium Metal Batteries.

The use of the "Holy Grail" lithium metal anode is pivotal to achieve superior energy density. However, the practice of a lithium metal anode faces practical challenges due to the thermodynamic instability of lithium metal and dendrite growth. Herein, an artificial stabilization of lithium metal was carried out via the thermal pyrolysis of the NH4F salt, which generates HF(g) and NH3(g). An exposure of lithium metal to the generated gas induces a spontaneous reaction that forms multiple solid electrolyte interface (SEI) components, such as LiF, Li3N, Li2NH, LiNH2, and LiH, from a single salt. The artificially multilayered protection on lithium metal (AF-Li) sustains stable lithium stripping/plating. It suppresses the Li dendrite under the Li||Li symmetric cell. The half-cell Li||Cu and Li||MCMB systems depicted the attributions of the protective layer. We demonstrate that the desirable protective layer in AF-Li exhibited remarkable capacity retention (CR) results. LiFePO4 (LFP) showed a CR of 90.6% at 0.5 mA cm-2 after 280 cycles, and LiNi0.5Mn0.3Co0.2O2 (NCM523) showed 58.7% at 3 mA cm-2 after 410 cycles. Formulating the multilayered protection, with the simultaneous formation of multiple SEI components in a facile and cost-effective approach from NH4F as a single salt, made the system competent.

Boosting the Interfacial Stability of the Li6PS5Cl Electrolyte with a Li Anode via In Situ Formation of a LiF-Rich SEI Layer and a Ductile Sulfide Composite Solid Electrolyte.

Due to its good mechanical properties and high ionic conductivity, the sulfide-type solid electrolyte (SE) can potentially realize all-solid-state batteries (ASSBs). Nevertheless, challenges, including limited electrochemical stability, insufficient solid-solid contact with the electrode, and reactivity with lithium, must be addressed. These challenges contribute to dendrite growth and electrolyte reduction. Herein, a straightforward and solvent-free method was devised to generate a robust artificial interphase between lithium metal and a SE. It is achieved through the incorporation of a composite electrolyte composed of Li6PS5Cl (LPSC), polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), resulting in the in situ creation of a LiF-rich interfacial layer. This interphase effectively mitigates electrolyte reduction and promotes lithium-ion diffusion. Interestingly, including PEG as an additive increases mechanical strength by enhancing adhesion between sulfide particles and improves the physical contact between the LPSC SE and the lithium anode by enhancing the ductility of the LPSC SE. Moreover, it acts as a protective barrier, preventing direct contact between the SE and the Li anode, thereby inhibiting electrolyte decomposition and reducing the electronic conductivity of the composite SE, thus mitigating the dendrite growth. The Li|Li symmetric cells demonstrated remarkable cycling stability, maintaining consistent performance for over 3000 h at a current density of 0.1 mA cm-2, and the critical current density of the composite solid electrolyte (CSE) reaches 4.75 mA cm-2. Moreover, the all-solid-state lithium metal battery (ASSLMB) cell with the CSEs exhibits remarkable cycling stability and rate performance. This study highlights the synergistic combination of the in-situ-generated artificial SE interphase layer and CSEs, enabling high-performance ASSLMBs.

Generating Multi-Carbon Products by Electrochemical CO2 Reduction via Catalytically Harmonious Ni/Cu Dual Active Sites.

Despite the unique advantages of single-atom catalysts, molecular dual-active sites facilitate the C-C coupling reaction for C2 products toward the CO2 reduction reaction (CO2 RR). The Ni/Cu proximal dual-active site catalyst (Ni/Cu-PASC) is developed, which is a harmonic catalyst with dual-active sites, by simply mixing commercial Ni-phthalocyanine (Ni-Pc) and Cu-phthalocyanine (Cu-Pc) molecules physically. According to scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) energy dispersive spectroscopy (EDS) data, Ni and Cu atoms are separated, creating dual-active sites for the CO2 RR. The Ni/Cu-PASC generates ethanol with an FE of 55%. Conversely, Ni-Pc and Cu-Pc have only detected single-carbon products like CO and HCOO- . In situ X-ray absorption spectroscopy (XAS) indicates that CO generation is caused by the stable Ni active site's balanced electronic state. The CO production from Ni-Pc consistently increased the CO concentration over Cu sites attributed to subsequent reduction reaction through a C-C coupling on nearby Cu. The CO bound (HCOO- ) peak, which can be found on Cu-Pc, vanishes on Ni/Cu-PASC, as shown by in situ fourier transformation infrared (FTIR). The characteristic intermediate of *CHO instead of HCOO- proves to be the prerequisite for multi-carbon products by electrochemical CO2 RR. The work demonstrates that the harmonic dual-active sites in Ni/Cu-PASC can be readily available by the cascading proximal active Ni- and Cu-Pc sites.

Lewis Acid Probe for Basicity of Sulfide Electrolytes Investigated by 11B Solid-State NMR.

Sulfide-based solid-state lithium-ion batteries (SSLIB) have attracted a lot of interest globally in the past few years for their high safety and high energy density over the traditional lithium-ion batteries. However, sulfide electrolytes (SEs) are moisture-sensitive which pose significant challenges in the material preparation and cell manufacturing. To the best of our knowledge, there is no tool available to probe the types and the strength of the basic sites in sulfide electrolytes, which is crucial for understanding the moisture stability of sulfide electrolytes. Herein, we propose a new spectral probe with the Lewis base indicator BBr3 to probe the strength of Lewis basic sites on various sulfide electrolytes by 11B solid-state NMR spectroscopy (11B-NMR). The active sulfur sites and the corresponding strength of the sulfide electrolytes are successfully evaluated by the proposed Lewis base probe. The probed strength of the active sulfur sites of a sulfide electrolyte is consistent with the results of DFT (density functional theory) calculation and correlated with the H2S generation rate when the electrolyte was exposed in moisture atmosphere. This work paves a new way to investigate the basicity and moisture stability of the sulfide electrolytes.

In-Depth Insight into a Passive Film through Hydrogen-Bonding Network in an Aqueous Zinc Battery.

Electrochemical stability and interfacial reactions are crucial for rechargeable aqueous zinc batteries. Electrolyte engineering with low-cost aqueous electrolytes is highly required to stabilize their interfacial reactions. Herein, we propose a design strategy using glutamic additive and its derivatives with modification of hydrogen-bonding network to enable Zn aqueous battery at a low concentration (2 m ZnSO4 + 1 m Li2SO4). Computational, in situ/ex situ spectroscopic, and electrochemical studies suggest that additives with moderate interactions, such as 0.1 mol % glutamic additive (G1), preferentially absorb on the Zn surface to homogenize Zn2+ plating and favorably interact with Zn2+ in bulk to weaken the interaction between H2O and Zn2+. As a result, uniform deposition and stable electrochemical performance are realized. The Zn||Cu half-cell lasts for more than 200 cycles with an average Coulombic efficiency (CE) of >99.32% and the Zn||Zn symmetrical cells for 1400 h with a low and stable overpotential under a current density of 0.5 mA cm-2, which is better than the reported results. Moreover, adding 0.1 mol % G1 to the Zn||LFP full cell improves its electrochemical performance with stable cycling and achieves a remarkable capacity of 147.25 mAh g-1 with a CE of 99.79% after 200 cycles.

Dual-Doped Cubic Garnet Solid Electrolytes with Superior Air Stability.

Li7La3Zr2O12 (LLZO) garnet is one kind of solid electrolyte drawing extensive attention due to its good ionic conductivity, safety, and stability toward lithium metal anodes. However, the stability problem during synthesis and storage results in high interfacial resistance and prevents it from practical applications. We synthesized air-stable dual-doped Li6.05La3Ga0.3Zr1.95Nb0.05O12 ((Ga, Nb)-LLZO) cubic-phase garnets with ionic conductivity of 9.28 × 10-3 S cm-1. The impurity-phase species formation on the garnet pellets after air exposure was investigated. LiOH and Li2CO3 can be observed on the garnet pellets by Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) once the garnets are exposed to humid air or come in contact with water. The (Ga, Nb)-LLZO garnet is found to form less LiOH and Li2CO3, which can be further reduced or removed after drying treatment. To confirm the stability of the garnet, an electrochemical test of the Li//Li symmetric cell was also performed in comparison with previously reported garnets (Li7La2.75Ca0.25Zr1.75Nb0.25O12, (Ca, Nb)-LLZO). The dual-doped (Ga, Nb)-LLZO showed less polarized and stable plating/stripping behavior than (Ca, Nb)-LLZO. Through Rietveld refinement of XRD patterns of prepared materials, dopant Ga was found to preferably occupy the Li site and Nb takes the Zr site, while dopant Ca mainly substituted La in the reference sample. The inherited properties of the dopants in (Ga, Nb)-LLZO and their structural synergy explain the greatly improved air stability and reduced interfacial resistance. This may open a new direction to realize garnet-based solid electrolytes with lower interfacial resistance and superior air stability.

Electrochemical Behaviour of Tinidazole at 1,4-Benzoquinone Modified Carbon Paste Electrode and Its Direct Determination in Pharmaceutical Tablets and Urine by Differential Pulse Voltammetry.

A simple and highly sensitive electrochemical method based on a 1,4-benzoquinone modified carbon paste electrode (1,4-BQMCPE) was described for the determination of tinidazole (TDZ). In Britton Robinson buffer solution, TDZ yields well-defined irreversible reduction peak at -0.344 V on a 1,4-BQMCPE. Compared with that on a bare CPE, the reduction peak of TDZ increased significantly on the modified CPE and the effects of different parameters on the voltammetric responses were also investigated. Differential pulse voltammetric method was proposed and optimized for TDZ determination and its reductive peak current response at 1,4-BQMCPE was found to show linear dependence on the concentration of TDZ in the range of 1.0 × 10-6 to 5.0 × 10-4 M with a linear regression equation, correlation coefficient, limit of detection (LOD), and limit of quantification (LOQ) of IPC (µA) = 0.19958 + 0.02657C (µM), 0.99486, 1.10 × 10-7 M, and 3.77 × 10-7, respectively. Excellent recovery results for spiked TDZ in pharmaceutical tablet samples ranging within 97.44-97.51% and in urine ranging within 95.37-96.91% were observed. The selectivity of the method for TDZ was further studied in the presence of selected potential interferents and confirmed the potential applicability of the developed method for the determination of TDZ.

Electrochemical Determination of Metronidazole in Tablet Samples Using Carbon Paste Electrode.

Cyclic voltammetric investigation of metronidazole at carbon paste electrode revealed an irreversible reduction peak centered at about -0.4 V. Observed peak potential shift with pH in the range 2.0 to 8.5 indicated the involvement of protons during the reduction of metronidazole, whereas the peak potential shift with scan rate in the range 10-250 mV/s confirmed the irreversibility of the reduction reaction. A better correlation coefficient for the dependence of peak current on the scan rate than on the square root of scan rate indicated an adsorption controlled kinetics. Under the optimized method and solution parameters, an excellent linearity between the reductive peak current and the concentration of metronidazole was observed in the concentration range 1.0 × 10(-6) to 5.0 × 10(-4) M with a correlation coefficient, method detection limit (based on s = 3σ), and limit of quantification of 0.999, 2.97 × 10(-7) M and 9.91 × 10(-7) M, respectively. Good recovery results for spiked metronidazole in tablet samples and selective determination of metronidazole in tablet formulations in the presence of selected potential interferents such as rabeprazole, omeprazole, and tinidazole confirmed the potential applicability of the developed method for the determination of metronidazole in real samples like pharmaceutical tablets.