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• Self-discharge kinetics behavior of Li-Si anode is investigated by theoretical model and experiment. • Effective diffusion coefficients of soluble lithium in porous electrode are determined to verify the availability of model. • Effects of temperature, discharge current and electrode thickness on self-discharge kinetics behavior are discussed. • The three factors are coupled in the form of arrhenius equation by multivariate nonlinear regression. Self-discharge has significant influence on the service life of thermal batteries. The kinetics process of self-discharge depends on both the structure evolution and intrinsic property of electrodes. Herein, the kinetics model to quantify the self-discharge degree of the Li-Si anode is constructed according to the structure of thermal cells. Typical operation and preparation parameters, i.e. temperature, discharge current and electrode thickness, are evaluated based on the specially designed combined-discharge scheme. Then the effective diffusion coefficients (D eff) of soluble lithium (Li0) that are affected by the three variables are calculated and fitted. The calculation results consequently confirm self-discharge process of the Li-Si anode can be described by the derived equations exactly, and then the process is demonstrated to be diffusion-controlled. Further, D eff increase at the higher temperature and larger discharge current, while decrease with the increased electrode thickness, which is analyzed by scanning electron microscope and X-ray microcomputed tomography. The entire effects on D eff can be coupled in one fitting expression based on Arrhenius equation, and the apparent activation energies decrease under the larger discharge current and smaller electrode thickness. Finally, the additional experiments were conducted to verify the accuracy of the fitting expression. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: The amphipathic phenylalanine-adsorbed layer contributes to form a nucleophilic–hydrophobic interface that homogenizes Zn2+ flux while repelling H2O molecules from contacting Zn anode. The preferential reduction of phenylalanine (Phe) prior to H2O facilitates in situ formation of an organic–inorganic hybrid solid electrolyte interphase, enhancing the interfacial stability. Benefiting from the triple protection of Phe, the Zn||Zn and Zn||LMO cells display significantly improved electrochemical performances, even at extreme diluted electrolytes. 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. [ABSTRACT FROM AUTHOR]

The Zn//V2O5 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//V2O5 full cells. The polymer matrix and BN exhibit a robust anchoring effect on SO42−, 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//V2O5 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. [ABSTRACT FROM AUTHOR]

The Zn//V2O5 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//V2O5 full cells. The polymer matrix and BN exhibit a robust anchoring effect on SO42−, 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//V2O5 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. [ABSTRACT FROM AUTHOR]

Abstract Polycrystalline nickel ferrite (NiFe 2 O 4) thin films were fabricated by pulsed laser deposition (PLD) and coated with nanometer layer of lithium phosphorus oxynitride (LiPON) by radio frequency magnetron sputtering (RF sputtering). Physical characterizations demonstrated that NiFe 2 O 4 thin films were not destroyed by LiPON coating with 50 nm thickness. Discharge capacity of LiPON coated NiFe 2 O 4 thin film after 50 cycles at 5 μA cm−2 was 849 mAh g−1, much higher than the counterpart value of pristine NiFe 2 O 4 thin film (449 mAh g−1), while rate capability was also greatly enhanced. Ex situ TEM investigation confirmed the two-steps reaction mechanism between NiFe 2 O 4 and Li, which includes an irreversible decomposition reaction of NiFe 2 O 4 in the first discharge process and reversible reactions between NiO, Fe 2 O 3 and their nanosized metal particles afterward. The significant improvement on the electrochemical performance was ascribed to the amorphous LiPON layer on the surface, which suppressed the volume expansion of electrode, the formation of delaminated particles and generation of cracks on electrode surface, as proved by ex situ SEM and AFM results. The LiPON coating is an effective approach to enhance the electrochemical performance of conversion materials for lithium ion batteries. Highlights • Pristine and LiPON coated NiFe 2 O 4 thin films were fabricated. • LiPON coating benefits the electrochemical performance of NiFe 2 O 4 thin film. • Conversion mechanism was confirmed by ex situ TEM technique for the first time. • Ex situ SEM and AFM results explained the effect of LiPON coating. [ABSTRACT FROM AUTHOR]

• A system-level thermal-electrochemical model of thermal batteries during activation stage is built. • Fuse strip has important effects on the activation process of thermal batteries. • The difference of internal resistance between the unactivated and activated state can reach 12 orders of magnitude. As the primary reserve batteries widely used in military domain, the intricate thermal-electrochemical behaviors and tiny time scale of the activation process make the development of thermal batteries a pain-stacking work, as lacking of the precise model to guide the design process. In this study, a system-level thermal-electrochemical model for evaluating the main technical indexes of LiSi/FeS 2 thermal batteries during activation stage is built, which comprehensively considers the main physical and chemical processes such as combustion, heat transfer, phase change, ion transport, voltage variation and so on. The activation characteristics of two types of 5-cell thermal batteries are predicted by this model, and the activation voltages of the two batteries are tested to validate the model. The model possesses the high precision with error less than 5 % by comparing the simulation results of activation voltage with that of experiment results. Specifically, the model reveals that the instantaneous temperature of pyrotechnic pellet after combustion is around 1570 K, and the electrolyte becomes molten and its internal resistance sharply decreases to mΩ level when the temperature reaches its melting point. The variation process of activation voltage is mainly dominated by the geometry size of cell stack and the thickness ratio of pyrotechnic pellet to single cell, besides, the activation time can be considered to be the peak value time of activation voltage. Fuse strip has important effects on the activation process of thermal batteries, especially in the rapid increase period of activation voltage, and the heat transfer is the time-limited step of the activation process. The difference of internal resistance between the unactivated state and activated state of thermal batteries can reach 12 orders of magnitude. These results indicate that our model can perform well in evaluating the activation process of thermal batteries and guiding the optimal design. [ABSTRACT FROM AUTHOR]

[Display omitted] • The combined electrochemical and transport kinetic parameters of CoS 2 /LiCl-LiBr-KBr system at the varied high temperature were systematically studied. • The effects of electrochemical and transport behavior on the impedance characteristic of CoS 2 /LiCl-LiBr-KBr were explored by proposing a equivalent-circuit model. • The results of this research is basis for the design and optimization of the new thermal battery cell. Systematic researches of ionic transport and electrochemical characteristics have been seldom implemented for the porous CoS 2 electrode in ternary LiCl-LiBr-KBr, which are ideal and main form for advanced thermal batteries. In the work, we systematically measured the combined electrochemical and transport kinetic parameters of CoS 2 /LiCl-LiBr-KBr system at the varied high temperature. Specifically, we firstly explored the discharge mechanism of CoS 2 /molten LiCl-LiBr-KBr using galvanostatic discharge experiment and X-ray diffraction (XRD). For the ionic transport performance, the diffusion coefficient of active Li ions was calculated from cyclic voltammograms (CV) data, and the ionic conductivity of LiCl-LiBr-KBr and electric conductivity of CoS 2 and generated Co 9 S 8 were also measured. Then, the interfacial electrochemical characteristics (exchange current density and transfer coefficients) were comparatively studied by the electrochemical impedance spectroscopy (EIS) and linear sweep voltammograms (LSV) method. Based on the above-mentioned results, we further investigated the comprehensive effects of these factors on the electrochemical and transport behavior by proposing a equivalent-circuit model of the porous CoS 2 electrode soaked in LiCl-LiBr-KBr molten salts. The results of this research is basis for the design and optimization of the new thermal battery cell, and will contribute to a knowledge-based development of the advanced TBs in the future. [ABSTRACT FROM AUTHOR]

Li 3 P-VP nanocomposite has been formed by a homemade pulsed laser deposition route and its electrochemical characteristic with lithium is reported for the first time. It displays high lithium storage capability as electrode material for secondary lithium ion batteries. The Li 3 P-VP nanocomposite exhibits high specific discharge capacity of 1040.4 mAh g−1 between 0.01 and 4.0 V and the specific capacity can still maintain 95% after 50 cycles. Ex situ transmission electron microscopy reveals that VP 2 is generated from Li 3 P and VP after the first charging process to 4.0 V, while Li 3 P and V are found to be the final discharge products. In the recharging process, VP and VP 2 are formed as the delithiated products. Unlabelled Image • Li 3 P-VP nanocomposite thin film was fabricated by PLD. • High capacity of 1040.4 mAh g−1 was achieved and 95% was kept after 50 cycles. • VP 2 was generated from Li 3 P and VP after the first charging process to 4.0 V. • Reversible conversion mechanism to V and Li 3 P was suggested for VP-VP 2. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, we have systematically investigated the adsorption and diffusion behavior of Li in MoO 3 bulk, on MoO 3 (010) surface and in MoO 3 /graphene composite. Our results indicate that, in case of MoO 3 bulk, Li diffusion barriers in the interlayer and intralayer spaces are 0.55 eV and 0.58 eV respectively, which are too high to warrant fast Lithium-ion charge/discharge processes. While on MoO 3 (010) surface, Li exhibits a diffusion barrier as low as 0.07 eV which guarantees an extremely fast Li diffusion rate during charge/discharge cycling. However, in MoO 3 /graphene monolayer, Li diffusion barrier is at the same level as that on MoO 3 (010) surface, which also ensures a very rapid Li charge/discharge rate. The rapid Li charge/discharge rate in this system originates from the removal of the upper dangling O1 atoms which hinder the Li diffusion on the lower MoO 3 layer. Besides this, due to the interaction between Li and graphene, the Li average binding energy increases to 0.14 eV compared to its value on MoO 3 (010) surface which contributes to a higher voltage. Additionally, the increased ratio of surface area provides more space for Li storage and the capacity of MoO 3 /graphene composite increases up to 279.2 mAhg −1 . The last but not the least, due to the high conductivity of graphene, the conductivity of MoO 3 /graphene composite enhances greatly which is beneficial for electrode materials. In the light of present results, MoO 3 /graphene composite exhibits higher voltage, good conductivity, large Li capacity and very rapid Li charge/discharge rate, which prove it as a promising cathode material for high-performance lithium-ion batteries (LIBs). [ABSTRACT FROM AUTHOR]

[Display omitted] • A route is proposed to load nanoparticles and electrolyte into ceramic paper separator. • The proposed route is efficient and safe, which can be promoted to used in large scales. • Electrochemical performance of thermal batteries can be obviously improved with ceramic paper as separator. Composites consisted of ceramic paper, nanoparticles as well as molten salt electrolyte, are developed as the new electrolyte separators to substitute the traditional ones in thermal batteries, due to their flexible manufacture and good exhibition in electrochemical performance. However, the existed methods for fabricating the composites by roughly dip-coating with aqueous solutions, are suffering from drawbacks such as inefficiency, low consistence, or high temperature risk. Therefore, a new approach based on a melting-absorption-diffusion process, by using precursors without solvent, is developed. Firstly, the salts are accurately weighted. Then they melt on surfaces of ceramic papers and diffuse inside. After being treated at appropriate temperature for hours, high quality electrolyte separators based on ceramic papers are achieved. Compared to the traditional approaches, the new method can obviously increase and accurately control the amount of loaded nanoparticles and molten salts for each time. The achieved electrolyte separators also exhibit good electrochemical performance in single cells of thermal batteries compared with the traditional ones. With advantages like easy operation, high efficiency, and improved performance, this melting and in situ loading method holds broad prospect in preparing electrolyte separators at large scale. [ABSTRACT FROM AUTHOR]

In this paper, single-phase pyrite with different particle sizes is prepared by hydrothermal method with the reactants of NaS, S, and FeSO. Compared with natural pyrite powder, synthesized pyrite nanocubes with small particle sizes and fine distribution have lower resistance, higher specific capacity and power density during the discharging process. The enlarging contacting surface area of pyrite with electrolytes will reduce the concentration polarization caused by the discharging current and improve the utilization efficiency of the pyrite materials. When pulse currents are loaded, compared with natural pyrite single-cell thermal battery, synthetic ones have smaller voltage drops and higher power density during the pulse discharging process. Influences of particle sizes on the thermal stability of the pyrite powders have also been investigated. [ABSTRACT FROM AUTHOR]