Large-Scale Synthesis of High Energy Thermal Battery Cathode Ni0.5Co0.5S2 by a Simple Sintering Technique.

With the synergies of multiple elements, bimetallic sulfides exhibit excellent performance as splendid electrode materials and effective catalysts. However, large-scale synthesis of high-performance single-phase multicomponent sulfides has always been a challenge. Based on thermodynamic calculations, the intermediate phases NiS2 and Co3S4 are devoted to the synthesis of single-phase Ni0.5Co0.5S2. Because the reaction from NiS2 and Co3S4 to Ni0.5Co0.5S2 goes through a lower energy, it thermodynamically contributes to achieving a single-phase structure. Thus, single-phase Ni0.5Co0.5S2 can be simply and quickly prepared by two-step sintering and successfully scalable for mass production. This technique can extend to the whole ingredients Ni1-xCoxS2. Ni0.5Co0.5S2 demonstrates excellent thermal stability and good conductivity. It delivers a specific capacity of 671 mAh·g-1 and a specific energy of 1173 Wh·kg-1 when applied to a thermal battery cathode, which are increased by 18.6% and 25.0%, respectively, compared to pristine NiS2 (566 mAh·g-1) and CoS2 (537 mAh·g-1). This work proposes an innovative sintering method, which is applicable for cost-efficient and large-scale synthesis of single-phase multicomponent sulfides.

MultiElement-Doped Ni-Based Disulfide Enhances the Specific Capacity of Thermal Batteries by High Thermal Stability.

With the high theoretical capacity and the ability of large current discharge, NiS2 has been expected as a new cathode material for thermal batteries. However, its lower decomposition temperature (∼500 °C) restricts its application on thermal batteries because of the high operating temperature of thermal batteries (500-600 °C). In this case, Cr, Fe, Co, and Cu multielement-doped NiS2 (NiS2-d) has been successfully prepared by low-temperature solid-phase sintering. Owing to the effect of high entropy, the multielement doping improved the thermodynamic system stability of NiS2, and the decomposition temperature (2NiS2 → 2NiS + S2) increased from 482 to 610 °C. Interestingly, doping also reduces the particle size of NiS2, resulting in defects on the surface of NiS2 particles and improving the conductivity of NiS2.The actual discharge capacity of NiS2 enhanced significantly from 516 to 643 mA h g-1 at 500 °C, with a current density of 100 mA cm-2 and a cut-off voltage of 1.5 V. This is due to a more complete release of the first discharge reaction (NiS2 + 2Li+ + 2e- → NiS + Li2S) as the decomposition temperature rises. The enhancement of conductivity, meanwhile, lessens polarization during the discharge process, raises the voltage of the NiS2 discharge platform, and improves the stability of the NiS2 later discharge platform. Additionally, the smaller particle size enables improved contact between the cathode and the electrolyte interface, allowing electrolyte ions to quickly come into touch with the NiS2 surface. These results show that the discharge performance of NiS2 at high temperatures could be effectively improved by multielement doping. It provides a new method for improving the stability of a metal sulfide and its application at high-temperature discharge.

Lower Interfacial Resistance between a Ta-Doped Li7La3Zr2O12 (LLZTO) Solid Electrolyte and NiCl2 Cathode by a Simple Heat Treatment for a High-Specific Energy Thermal Battery.

Large current discharge is restricted because of the poor conductivity between the Ta-doped Li7La3Zr2O12 (LLZTO) solid electrolyte and electrode. The poor conductivity would be caused by the interfacial reaction between LLZTO and the cathode, which is detrimental to the secondary Li ionic or metal battery. In this case, we studied the interfacial reaction between LLZTO and a haloid cathode (NiCl2) for a thermal battery for the first time, and a lower interfacial resistance could be obtained by a simple heat treatment. Owing to the element interdiffusion of Cl- and O2- at a high temperature of 600 °C, the main reaction products are LaOCl, LiCl, and La2Zr2O7. This reaction reduces the interfacial resistance from 3 Ω to 2 Ω. After a pretreatment at 600 °C, the discharge specific energy could reach 1254 Wh kg-1 from 828 Wh kg-1 at 550 °C with a cut-off voltage of 1.8 V. These results suggest that the interfacial reaction could be significant for the battery by adding interfacial contact. It is an effective approach to decrease the interfacial resistance at high temperature for some specific system, such as a haloid cathode-solid electrolyte.

High Specific Capacity Thermal Battery Cathodes LiCu2O2 and LiCu3O3 Prepared by a Simple Solid Phase Sintering.

The thermal battery has been designed to be active at high temperature to satisfy storage life and large capacity for storage and emergency power. The development of thermal battery with high specific energy requires that the cathode has high thermal stability and excellent conductivity. Here, the semiconductor material Li-Cu-O compounds LiCu2O2 and LiCu3O3 are synthesized by a simple solid-phase sintering technique, which is simpler than the traditional synthesis process. The thermal decomposition temperatures are 680°C and above 900°C, respectively. This work first applies the Li-Cu-O compounds to the thermal battery. With a cutoff voltage of 1.5 V, the specific capacities of LiCu2O2 and LiCu3O3 are 423 and 332 mA h g-1. Both the decomposition temperature and specific capacity are higher than in the commercial FeS2 and CoS2, especially LiCu2O2. This work affords an alternative of the cathode materials for high specific capacity thermal battery.

Novel NiCl2 Nanosheets Synthesized via Chemical Vapor Deposition with High Specific Energy for Thermal Battery.

Two-dimensional (2D) nanomaterials possessing a unique sheet structure, compared to correlative bulk materials, exhibit excellent properties, especially in the energy storage and energy conversion field. In this case, NiCl2 nanosheets with thicknesses of 2-8 nm are first prepared by a simple chemical vapor deposition method. For the Li-B/LiF-LiCl-LiBr/NiCl2 thermal battery, the specific energy of NiCl2 nanosheets increases from 510 W h kg-1 (NiCl2 rods) to 616 W h kg-1 at an operation temperature of 500 °C and a current density of 0.2 A cm-2. The 2D morphology and large numbers of defects not only improve the redox reaction rates and the lithium storage capacity, but also enhance the adsorption capacity with the flake-like binder MgO, which prolong the discharge time by suppressing the discharge product diffusion to the electrolyte. These results indicate that NiCl2 nanosheets have a great possibility to become a desirable candidate of cathode materials for assisting in the development of high energy output and provide a new way to restrain the immersion between the electrode and electrolyte.

Enhanced visible light photocatalytic activity of g-C3N4 decorated ZrO2-x nanotubes heterostructure for degradation of tetracycline hydrochloride.

Photocatalytic degradation is considered as a promising strategy to address the environmental threat caused by antibiotics abuse. Visible light driven g-C3N4 decorated ZrO2-x nanotubes heterostructure photocatalysts for antibiotic degradation were successfully synthesized by anodic oxidation and following a thermal vapor deposition method. Compared with pure g-C3N4 or ZrO2-x nanotubes, the composite photocatalysts exhibited more extended visible light response and higher separation rate of photo-generated electron-holes pairs. The optimized heteroctructure with 7.1 wt.% g-C3N4 exhibited 90.6% degradation of tetracycline hydrochloride (TC-H) under 1 h visible light irradiation. The mainly active species of TC-H degradation were photo-generated h+ and O2-. The pathway of charge migration in the g-C3N4/ZrO2-x NTs system was also studied and a possible photocatalytic mechanism was proposed for TC-H degradation. Constructing the g-C3N4/ZrO2-x nanotubes heterostructure is anticipated to be an effective strategy for photocatalytic degradation of antibiotics.

Bundled Defect-Rich MoS2 for a High-Rate and Long-Life Sodium-Ion Battery: Achieving 3D Diffusion of Sodium Ion by Vacancies to Improve Kinetics.

Molybdenum disulfide (MoS2 ), a 2D-layered compound, is regarded as a promising anode for sodium-ion batteries (SIBs) due to its attractive theoretical capacity and low cost. The main challenges associated with MoS2 are the low rate capability suffering from the sluggish kinetics of Na+ intercalation and the poor cycling stability owning to the stack of MoS2 sheets. In this work, a unique architecture of bundled defect-rich MoS2 (BD-MoS2 ) that consists of MoS2 with large vacancies bundled by ultrathin MoO3 is achieved via a facile quenching process. When employed as anode for a SIB, the BD-MoS2 electrode exhibits an ultrafast charge/discharge due to the pseudocapacitive-controlled Na+ storage mechanism in it. Further experimental and theoretical calculations show that Na+ is able to cross the MoS2 layer by vacancies, not only limited to diffusion along the layer, thus realizing a 3D Na+ diffusion with faster kinetics. Meanwhile, the bundling architecture reduces the stack of sheets with a superior cycle life illustrating the highly reversible capacities of 350 and 272 mAh g-1 at 2 and 5 A g-1 after 1000 cycles.

Enhancement of the Adhesive Strength between Ag Films and Mo Substrate by Ag Implanted via Ion Beam-Assisted Deposition.

Silver-coated molybdenum is an optimum material selection to replace pure silver as solar cell interconnector. However, the low adhesive strength between Ag films and Mo substrate hinders the application of the interconnector, because it is difficult to form metallurgical bonding or compound in the film/substrate interface using conventional deposition. In order to improve the adhesion, some Ag particles were implanted into the surface of Mo substrate by ion beam-assisted deposition (IBAD) before the Ag films were deposited by magnetron sputtering deposition (MD). The objective of this work was to investigate the effect of different assisted ion beam energy on the film/substrate adhesive properties. In addition, the fundamental adhesion mechanism was illustrated. The results revealed that the adhesion between Ag films and Mo substrate could be greatly enhanced by IBAD. With the increase of the assisting ion beam energy, the adhesive strength first increased and then decreased, with the optimum adhesion being able to rise to 25.29 MPa when the energy of the assisting ion beam was 30 keV. It could be inferred that the combination of “intermixing layer” and “implanted layer” formed by the high-energy ion bombardment was the key to enhancing the adhesion between Ag films and Mo substrate effectively.

Excellent Tribological Properties of Lower Reduced Graphene Oxide Content Copper Composite by Using a One-Step Reduction Molecular-Level Mixing Process.

Reduced graphene oxide (RGO) composite copper matrix powders were fabricated successfully by using a modified molecular-level mixing (MLM) method. Divalent copper ions (Cu2+) were adsorbed in oxygen functional groups of graphene oxide (GO) as a precursor, then were reduced simultaneously by one step chemical reduction. RGO showed a distribution converting from a random to a three-dimensional network in the copper matrix when its content increased to above 1.0 wt.% The tribological tests indicated that the friction coefficient of the composite with 1.0 wt.% RGO decreased markedly from 0.6 to 0.07 at an applied load of 10 N, and the wear rate was about one-third of pure copper. The excellent tribological properties were attributed to a three-dimensional and uniform distribution, which contributes to improving toughness and adhesion strength.

Nanostructured Hypoeutectic Fe-B Alloy Prepared by a Self-propagating High Temperature Synthesis Combining a Rapid Cooling Technique.

We have successfully synthesized bulk nanostructured Fe94.3B5.7 alloy using the one-step approach of a self-propagating high temperature synthesis (SHS) combining a rapid cooling technique. This method is convenient, low in cost, and capable of being scaled up for processing the bulk nanostructured materials. The solidification microstructure is composed of a relatively coarse, uniformly distributed dendriteto a nanostructured eutectic matrix with α-Fe(B) and t-Fe2B phases. The fine eutectic structure is disorganized, and the precipitation Fe2B is found in the α-Fe(B) phase of the eutectic. The dendrite phase has the t-Fe2B structure rather than α-Fe(B) in the Fe94.3B5.7 alloy, because the growth velocity of t-Fe2B is faster than that of the α-Fe with the deeply super-cooling degree. The coercivity (Hc) and saturation magnetization (Ms) values of the Fe94.3B5.7 alloy are 11 A/m and 1.74T, respectively. Moreover, the Fe94.3B5.7 alloy yields at 1430 MPa and fractures at 1710 MPa with a large ductility of 19.8% at compressive test.