Amphipathic Phenylalanine-Induced Nucleophilic-Hydrophobic Interface Toward Highly Reversible Zn Anode.

Aqueous Zn2+-ion batteries (AZIBs), recognized for their high security, reliability, and cost efficiency, have garnered considerable attention. However, the prevalent issues of dendrite growth and parasitic reactions at the Zn electrode interface significantly impede their practical application. In this study, we introduced a ubiquitous biomolecule of phenylalanine (Phe) into the electrolyte as a multifunctional additive to improve the reversibility of the Zn anode. Leveraging its exceptional nucleophilic characteristics, Phe molecules tend to coordinate with Zn2+ ions for optimizing the solvation environment. Simultaneously, the distinctive lipophilicity of aromatic amino acids empowers Phe with a higher adsorption energy, enabling the construction of a multifunctional protective interphase. The hydrophobic benzene ring ligands act as cleaners for repelling H2O molecules, while the hydrophilic hydroxyl and carboxyl groups attract Zn2+ ions for homogenizing Zn2+ flux. Moreover, the preferential reduction of Phe molecules prior to H2O facilitates the in situ formation of an organic-inorganic hybrid solid electrolyte interphase, enhancing the interfacial stability of the Zn anode. Consequently, Zn||Zn cells display improved reversibility, achieving an extended cycle life of 5250 h. Additionally, Zn||LMO full cells exhibit enhanced cyclability of retaining 77.3% capacity after 300 cycles, demonstrating substantial potential in advancing the commercialization of AZIBs.

Toward Simultaneous Dense Zinc Deposition and Broken Side-Reaction Loops in the Zn//V2 O5 System.

The Zn//V2 O5 system not only faces the incontrollable growth of zinc (Zn) dendrites, but also withstands the cross-talk effect of by-products produced from the cathode side to the Zn anode, inducing interelectrode talk and aggravating battery failure. To tackle these issues, we construct a rapid Zn2+ -conducting hydrogel electrolyte (R-ZSO) to achieve Zn deposition modulation and side reaction inhibition in Zn//V2 O5 full cells. The polymer matrix and BN exhibit a robust anchoring effect on SO4 2- , accelerating Zn2+ migration and enabling dense Zn deposition behavior. Therefore, the Zn//Zn symmetric cells based on the R-ZSO electrolyte can operate stably for more than 1500 h, which is six times higher than that of cells employing the blank electrolyte. More importantly, the R-ZSO hydrogel electrolyte effectively decouples the cross-talk effects, thus breaking the infinite loop of side reactions. As a result, the Zn//V2 O5 cells using this modified hydrogel electrolyte demonstrate stable operation over 1,000 cycles, with a capacity loss rate of only 0.028 % per cycle. Our study provides a promising gel chemistry, which offers a valuable guide for the construction of high-performance and multifunctional aqueous Zn-ion batteries.

Electrochemical behaviors of Li-B alloys in a LiCl-LiBr-KBr molten salt system.

Li-B alloys present higher voltages and better power performances than those of conventional Li-Al and Li-Si anodes for thermal batteries. Herein, the electrochemical characteristics of the Li-B alloy in the LiCl-LiBr-KBr electrolyte, including the discharge mechanism, charge transfer coefficient and exchange current density, were investigated in the temperature range of 623-823 K by open circuit potential (OCP), cyclic voltammetry (CV), chronopotentiometry (CP), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques. Consequently, the OCP of the Li-B alloy in the LiCl-LiBr-KBr electrolyte is close to that of pure lithium at the investigated temperatures. The discharge of the Li-B alloy electrode includes electrochemical dissolution of free lithium (Li → Li+) and compounded lithium (LiB → Li+ + B). The charge transfer coefficient in the anodic direction (Li → Li+) is about 0.63 at 623 K, which slightly increases as the temperature increases. The exchange current density of the Li (Li-B)/Li+ couple determined by the EIS method increases from 3.84 A cm-2 to 8.40 A cm-2 when the temperature increases from 623 to 823 K, corresponding to an activation energy of 16.4 kJ mol-1. These results suggest that the Li-B anode allows ultrahigh-rate discharge in thermal batteries.

Mechanism and kinetics characteristic of self-discharge of FeS2 cathodes for thermal batteries.

The service life of FeS2 thermal batteries is significantly affected by self-discharge of the cathode. Herein, SEM, XRD and XPS were employed to characterize the mechanism of self-discharge of the FeS2 cathode. A novel combined-discharge method, in which a tiny current (5 mA cm-2) was applied to minimize the effect of polarization on discharge capacity, was conducted to study the kinetics characteristic of self-discharge of FeS2 cathode upon discharge. Then, the self-discharge kinetics parameters which are related to the current density (20, 50 and 200 mA cm-2) and temperature (400, 450, 500 and 550 °C) were determined by the Serin-Ellickson model. Characterizations of the cells standing at 500 °C confirm that the decomposition product of the FeS2 cathode is FeS. The quantitative analysis of self-discharge rate constants (SRC) demonstrates that the reaction is a diffusion-controlling process. The kinetics process can conform to the Serin-Ellickson model. Specifically, the values of SRC increase when the cell is carried by a heavier load, since more breakage would form in FeS2 particles at the larger current density. Besides, the SRC increase at a higher temperature, and the relationship of SRC and temperature can be fitted by the Arrhenius equation. Consequently, the apparent activation energy decreases with the increase of current density.

The synergistic effect of the PEO-PVA-PESf composite polymer electrolyte for all-solid-state lithium-ion batteries.

Blending with poly(vinyl alcohol) (PVA) and poly(oxyphenylene sulfone) (PESf) has been investigated to improve the properties of a polymer electrolyte based on a poly(ethylene oxide) (PEO) matrix. The composite electrolyte shows a high ionic conductivity of 0.83 × 10-3 S cm-1 at 60 °C due to the significant inhibition of crystallization caused by the synergistic effects of PVA and PESf. The symmetrical cell Li/CPE/Li is continuously operated for at least 200 hours at a current density of 0.1 mA cm-2 without the enhancement in the polarization potential. In addition, the all-solid-state LiFePO4/CPE/Li cells exhibit small hysteresis potential (about 0.10 V), good cycle stability and excellent reversible capacity (126 mA h g-1 after 100 cycles).

LiF Splitting Catalyzed by Dual Metal Nanodomains for an Efficient Fluoride Conversion Cathode.

The critical challenges for fluoride conversion cathodes lie in the absence of built-in Li source, poor capacity retention, and rate performance. For lithiated fluorides, the reason to limit their competitiveness is rooted in the facile coarsing of insulating LiF (as built-in Li source) and its insufficient splitting kinetics during charging. Previous efforts on blending LiF nanodomains with reductive metal, metal oxide, or fluoride by ball-milling method still face the problems of large overpotential and low current density. Herein we propose a strategy of dual-metal (Fe-Cu) driven LiF splitting to activate the conversion reaction of fluoride cathode. This lithiated heterostructure (LiF/Fe/Cu) with compact nanodomain contact enables a substantial charge process with considerable capacity release (300 mAh g-1) and low charge overpotential. Its reversible capacity is as high as 375-400 mAh g-1 with high energy efficiency (76%), substantial pseudocapacitance contribution (>50%), and satisfactory capacity retention (at least 200 cycles). The addition of Cu nanodomains greatly catalyzes the kinetics of Fe-Cu-F formation and decomposition compared with the redox process of Fe-F, which lead to the energy and power densities exceeding 1000 Wh kg-1 and 1500 W kg-1, respectively. These results indicate that LiF-driven cathode is promising as long as its intrinsic conductive network is elegantly designed.

A New Class of Ternary Compound for Lithium-Ion Battery: from Composite to Solid Solution.

Searching for high-performance cathode materials is a crucial task to develop advanced lithium-ion batteries (LIBs) with high-energy densities for electrical vehicles (EVs). As a promising lithium-rich material, Li2MnO3 delivers high capacity over 200 mAh g-1 but suffers from poor structural stability and electronic conductivity. Replacing Mn4+ ions by relatively larger Sn4+ ions is regarded as a possible strategy to improve structural stability and thus cycling performance of Li2MnO3 material. However, large difference in ionic radii of Mn4+ and Sn4+ ions leads to phase separation of Li2MnO3 and Li2SnO3 during high-temperature synthesis. To prepare solid-solution phase of Li2MnO3-Li2SnO3, a buffer agent of Ru4+, whose ionic radius is in between that of Mn4+ and Sn4+ ions, is introduced to assist the formation of a single solid-solution phase. The results show that the Li2RuO3-Li2MnO3-Li2SnO3 ternary system evolves from mixed composite phases into a single solid-solution phase with increasing Ru content. Meanwhile, discharge capacity of this ternary system shows significantly increase at the transformation point which is ascribed to the improvement of Li+/e- transportation kinetics and anionic redox chemistry for solid-solution phase. The role of Mn/Sn molar ratio of Li2RuO3-Li2MnO3-Li2SnO3 ternary system has also been studied. It is revealed that higher Sn content benefits cycling stability of the system because Sn4+ ions with larger sizes could partially block the migration of Mn4+ and Ru4+ from transition metal layer to Li layer, thus suppressing structural transformation of the system from layered-to-spinel phase. These findings may enable a new route for exploring ternary or even quaternary lithium-rich cathode materials for LIBs.

Multifunctional interface modification of energy relay dye in quasi-solid dye-sensitized solar cells.

In this paper, 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) has been used in interface modification of dye-sensitized solar cells (DSCs) with combined effects of retarding charge recombination and Förster resonant energy transfer (FRET). DCJTB interface modification significantly improved photovoltaic performance of DSCs. I-V curves shows the conversion efficiency increases from 4.27% to 5.64% with DCJTB coating. The application of DCJTB with combined effects is beneficial to explore more novel multi-functional interface modification materials to improve the performance of DSCs.