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• The coating layer of carbon was designed for a bare CuF 2 cathode. • The carbon layer inhibits side reactions between CuF 2 and LiF–LiCl–LiBr electrolyte. • CuF 2 @C delivers ultrahigh discharge specific capacity and actual discharge time. Conversion-type compounds as cathodes for thermal batteries have recently attracted considerable attention due to their excellent specific capacities. CuF 2 has been regarded as a promising candidate owing to its high theoretical discharge voltage (3.55 V, vs Li) and theoretical capacity (528 mAh·g−1). However, mass loss caused by side-reactions from CuF 2 cathode and molten salt electrolyte leads to severe degradation of the discharge capacity of single-cells in thermal batteries. As a proof-of-concept, in this work, carbon coated CuF 2 (CuF 2 @C) is employed as the cathode to fabricate thermal batteries, in which carbon serves as a protector to inhibit the mass loss of CuF 2 in molten salt electrolyte. As a result, CuF 2 @C demonstrates obviously improved electrochemical performance with a discharge specific capacity of 462.45 mAh·g−1 at the current density of 10 mA·cm−2, which is 82.67 % higher than that of the counterpart (bare CuF 2). This can be attributed to the reduced average polarization resistance of the single-cells in CuF 2 @C composites. This work provides a new route for developing high performance CuF 2 -based cathode material for thermal batteries and promoting its further practical application. [ABSTRACT FROM AUTHOR]

CoS 2 cathode has been extensively adopted for application in thermal batteries due to its excellent electrochemical performance. However, CoS 2 undergoes rapid discharge degradation at high-rates or low working temperatures because of its high polarization resistance. This is ascribed to the kinetically slow rate of Li+ inset in the CoS 2 cathode. With the aim of accelerating charge carrier exchange at the cathode-electrolyte interface, the construction of a heterostructure with an engineered electronic structure at the surface of CoS 2 is described in this present work. The results show that the specific discharge capacity (V ≥ 1.75 V) of heterostructured CoS 2 increases 23% at 500 °C and 42.3% at 450 °C with discharge currents of 300 and 100 mA cm−2, respectively. Electrochemistry measurements and density functional theory (DFT) analysis decipher that N modification alters the surface structure of CoS 2 , resulting in beneficial "defect" formation, that further enhances surface exchange density and the adsorption capability of Li+. [Display omitted] • Specific discharge capacity (V ≥ 1.75 V) of heterostructured CoS 2 increases 23% at 500 °C and 42.3% at 450 °C. • Electrochemical behaviors of heterostructured CoS 2 in molten salt are discussed and verified. • Influence mechanisms of heterostructured CoS 2 are studied by the DFT calculation. [ABSTRACT FROM AUTHOR]

Abstract As the most promising anode material for next-generation Li batteries, Li metal never loses the academic attention due to its inherent superiority in high theoretical capacity and low redox potential. However, Li dendrites formed during cycling stubbornly hinder the pace of commercializing high-energy-density Li metal batteries. Here sericin endowed with abundant lithiophilic and anionphilic functional groups on its polypeptide chain is proposed as a conformal protective coating on both Cu and Li metal anodes. The resulting increase of Li-ion transference number (as high as 0.876) and mitigation of tip effect are favorable for the homogeneous Li deposition in island-like or lateral growth mode at electrode/electrolyte interface. Long cycle life (335 cycles) and high Coulombic efficiency (98%) are obtained in sericin decorated Li/Cu cells. Even under extremely high current density of 10 mA cm−2 based on a large capacity of 5 mAh cm−2, the sericin decorated Li anode also enables a superior cycle stability (160 cycles) in the symmetric cells. The conformal sericin coating effectively inhibits the corrosion of air to Li metal. Sericin modified Li-S batteries exhibit greatly enhanced rate performance (452.8 mAh g−1 at 5 C) and cycling performance (667.8 mAh g−1 after 520 cycles at 1 C). Graphical abstract Image 1 Highlights • Sericin is proposed as a conformal protective coating on both Cu and Li metal anodes. • Under 10 mA cm−2, the sericin decorated Li anode enables a superior cycle stability. • The conformal sericin coating effectively inhibits the corrosion of air to Li metal. • Sericin modified Li-S batteries exhibit enhanced rate and cycling performance. [ABSTRACT FROM AUTHOR]

• The FeS 2 cathode has successfully modified by Al 2 O 3 nanoparticles (FeS 2 @Al 2 O 3). • The modified FeS 2 @Al 2 O 3 increases the transport rate of lithium ions. • The good wettability of solid-liquid interface suppresses the overflow of electrolytes. • The thermal batteries using of FeS 2 @Al 2 O 3 cathode achieve better performance. Thermal batteries are widely employed as the primary reserve batteries due to their high energy density and long shelf lifespan. FeS 2 is the most studied and promising cathode material of thermal batteries at present because of its abundant stock and superior electrochemical performance. However, the FeS 2 cathode is limited by low discharge capacity, big polarization, and security issues during discharge process. Herein, the improved electrochemical performance is achieved by increasing the interface wettability between cathode and electrolyte, in which the FeS 2 cathode has modified by Al 2 O 3 (FeS 2 @Al 2 O 3) nanoparticles. The good wettability of the solid-liquid interface suppresses the overflow of electrolytes, and the discharge capacity of thermal batteries by using FeS 2 @Al 2 O 3 cathode is 341.3 mAh·g−1, which is higher than that of pure FeS 2 cathode (319.7 mAh·g−1). Significantly, this work provides a novel idea for modifying cathode material for comprehensive performance and safe thermal batteries in practical engineering applications. [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]

[Display omitted] • (1 1 0) orientation is favored for energy minimization of LiCoO 2 thin film. • LCO(1 1 0)/LiPON/Li shows a discharge capacity of 47 μAh cm−2 μm−1 (about 101 mAh g−1) on 10C-rate. • Oxygen reactive sputtering promotes the transformation from LiCoO 2 (1 1 0) texture to (0 0 3) texture. • LiCoO 2 (1 1 0) texture has the lowest interface and bulk resistance for Li+ transfer. The solid-solid interfaces have crucial, but still poorly understood, roles in the performance of thin-film lithium batteries (TFBs). The modulating of crystalline preferred growth orientation is an effective method to build rapid ionic diffusion channel with lower interfacial barrier. This work develops and reveals the interfacial electrochemical behaviors of textured cathode/solid electrolyte in TFBs by controlling preferred growth orientation of LiCoO 2 (LCO) thin-film. The LCO(0 0 3) texture is transformed from the (4 4 0) plane of Co 3 O 4 precursor with the lowest surface energy after annealing. Remarkably, oxygen reactive sputtering will promote the formation of LCO grains instead of Co 3 O 4 species, resulting in the growth of LCO along (1 1 0) facet with the lowest volume strain-energy after annealing. TFBs (LCO/LiPON/Li) configuration with LCO(1 1 0) texture exhibit enhanced electrochemical performance with the capacity of about 101 mAh g−1 about twice than that of (0 0 3) texture on 10C-rates, owing to the lower interface and bulk resistance. These results indicate that the method of controlling the lattice orientation not only minimize the lithium-ion diffusion pathways in the film textures, but also is beneficial to the interface between LCO and LiPON electrolyte to establish high performance solid-state batteries. [ABSTRACT FROM AUTHOR]

As the most investigated cathode of thermal batteries, the electrochemical performance of CoS 2 is limited by a big polarization at high current density and low working temperature, which is ascribed to the poor wettability of molten salt on CoS 2 surface and low exchange current density. In this contribution, Al 2 O 3 is selected as a modifier to improve the wettability of molten salt on CoS 2 surface and exchange current density at the same time, by adjusting the dielectric polarization field of CoS 2 surface. The discharge capacity (V ≥ 1.7 V) of CoS 2 increases by ~11% at 500 °C with a discharge current of 300 mA cm−2, and 55% at 450 °C with a discharge current of 100 mA cm−2, by the decoration of Al 2 O 3 nanoparticles. Moreover, the influence of decorated Al 2 O 3 nanoparticles on the electrochemical performance of CoS 2 are discussed. • CoS 2 decorated with Al 2 O 3 nanoparticles can be synthesized via a simple way. • Optimized interface is able to boost the discharge ability of thermal batteries. • Influence mechanisms of Al 2 O 3 on electrochemical behavior of CoS 2 are studied. [ABSTRACT FROM AUTHOR]