This paper presents a technique to form an electrochemically active interface between the oxides in an all-solid-state Li secondary battery (ASSB), via liquid sintering. Spinel-type Li₄Mn₅O₁₂ (LMO) is formed on a perovskite-type Li_0.29La_0.57TiO₃ (LLTO) solid electrolyte by heating Mn(NO₃)₂·6H₂O, LiNO₃ and LiCl. The resultant LMO, when evaluated as a positive electrode in an ASSB, exhibits a reversible capacity of 100 mAh g⁻¹, good cyclability, and typical charge/discharge curves. LiCoO₂ (LCO) is also prepared similarly, using molten salts, and a full ASSB is assembled with LCO as the positive electrode, LLTO as the solid electrolyte, and LMO as the negative electrode. The full ASSB exhibits a plateau at 1 V and discharge capacity of 60 mAh g⁻¹ at a C-rate of C/100. When the C-rate is increased to 1 C, the capacity retention decreases below 20 % after 40 cycles; however, when the C-rate is returned to C/100, the retention recovers to 100 %. The porous LLTO supporting Li-ion conduction improves the performance of the ASSB. The effective formation of electrodes on LLTO using molten salts can facilitate the creation of ASSBs comprising oxides alone.

“In-parallel distributed circuits” and “in-series distributed circuits,” which comprise numerous similar circuit units connected in parallel and in series, are proposed, as expansions of traditional lumped constant equivalent circuits for electrochemical impedance spectroscopy, such as Randles-type circuit. An in-series distributed circuit is used to describe non-uniformity of some properties along the direction of the current, whereas an in-parallel distributed circuit is used to describe those along the direction perpendicular to the current. The calculation method of the impedance values of the proposed distributed circuit is presented generally. Qualitative characteristics of the impedance values of several types of distributed circuits were investigated. The results include some types of deviations from behaviors of lumped constant circuits, which is often observed experimentally, such as a distorted semicircle and an inclined vertical line. The proposed calculation method is not specialized for the examples described in this work, and can be widely used to any kind of circuits.

With the improvement of lithium-ion batteries in civil aviation transportation, the thermal safety of lithium-ion batteries can not be ignored. Especially in a battery pack, the thermal runaway of batteries can spread from cell to cell, resulting in catastrophic hazards. This work focuses on the experimental setup and analysis of the experimental parameters of lithium-ion batteries with different thicknesses of aerogel felt to study the blocking effect of barrier materials on thermal runaway propagation of lithium-ion batteries in civil aviation transport. The aerogel felt was selected as the barrier material and a series of experiments were carried out with different thicknesses of 1 mm, 3 mm, and 6 mm. The results demonstrated that the increase of aerogel felt thickness exhibited excellent performance in delaying lithium-ion battery thermal runaway. Additionally, a simplified thermal model of thermal runaway propagation was proposed to explain the thermal runaway propagation in the battery to adjacent batteries. These results provide valuable suggestions and enlightenment for the aviation safety transportation of lithium-ion batteries.

To better understand the thermal runaway characteristics of lithium-ion batteries in civil aviation transportation environments, an experimental platform for the fire and explosion of lithium-ion batteries was designed and built. The 18650 NCM lithium-ion battery was selected as the test sample to study the influence of different initial pressures on the thermal runaway characteristics of the lithium-ion battery pack in a confined space. The results showed that, under 61 kPa, the initial thermal runaway triggering time is longer, the initial thermal runaway temperature is higher, and the explosion pressure and TNT equivalent are lower than that under 96 kPa. The mass loss increased with the increase of pressure and the number of batteries. In addition, the initial thermal runaway triggering time and temperature are affected by the number of batteries. These results could provide some support for civil aviation transportation safety.

Transition metal-tungsten nitrides (CrWN₂, MnWN₂, FeWN₂, Co₃W₃N, Ni₂W₃N) could be synthesized and electrocatalytic properties on electrochemical oxygen reduction and evolution reactions were examined. The oxygen reduction performance was in the order of Co₃W₃N > MnWN₂ > Ni₂W₃N ≫ FeWN₂ ≫ CrWN₂. While the oxygen evolution was in that of Co₃W₃N ≫ CrWN₂ > Ni₂W₃N > MnWN₂ ≫ FeWN₂. Then, the Co₃W₃N gave high bi-functional oxygen electrocatalytic properties. Furthermore, Ni-doped (Co_1−xNi_x)₃W₃N (x = 0–1.0) were prepared and it was found that the (Co_0.6Ni_0.4)₃W₃N gave the highest bi-functional electrocatalytic properties. The cathode performance was achieved with the electrode containing 32 wt% (Co_0.6Ni_0.4)₃W₃N, i.e., the current density as high as 280 mA cm⁻², which was 10 times higher than that of a carbon-only electrode, was obtained at (0.80 V vs. RHE) in 5 mol L⁻¹ KOH at 70 °C. Also, the (Co_0.6Ni_0.4)₃W₃N electrode showed high activity to oxygen evolution as high as 300 mA cm⁻² at (1.60 V vs. RHE). As it was observed the changes in binding energy at O_1s, N_1s, W_4f, Co_2p, and Ni_2p spectra among Co₃W₃N, (Co_0.6Ni_0.4)₃W₃N, and Ni₂W₃N by X-ray photoelectron spectroscopy, the change in electrical properties at the surface of the nitrides should be one of the reasons of the high performance.

In the active material of a lithium-ion secondary battery, electrons and lithium-ions react at the same time. The fact that the active material can transfer electrons with a small reaction overvoltage leads to a reduction in the internal resistance of the battery. Therefore, when the electrical resistance was measured by changing the electrode material in contact with the active material, it was found that the electrical resistance of the active material was reduced depend on the carbon materials make contact with the active material.

Electrorefining is an effective method for preparing high-purity indium. To realize the control of impurity Sn in crude indium electrolytic refining, electrochemical test methods, such as cyclic voltammetry (CV), and chronoamperometry (CA) were mainly used to study the electrochemical behavior of indium. The results show that when a few of SnSO₄ was added to the electrolyte containing indium sulfate, in the meantime, the Sn²⁺ concentration reached 5000 ppm, in the electrolysis process, the impurity Sn in the cathode was appeared to precipitate before the indium precipitated. The electrodeposition of indium was irreversible, controlled by diffusion steps, and In³⁺ reduction was carried out by fractional steps, transferring one electron at a time. The diffusion coefficient of In³⁺ calculated by cyclic voltammetry was 1.02 × 10⁻⁷ cm²/s, and the average charge transfer coefficient was 0.081. The nucleation mechanism of indium conformed to three-dimensional instantaneous nucleation. The results provide theoretical guidance for electrolytic refining of crude indium and electrochemical regulation of impurities.