Handong Jiao

A long-life rechargeable Al ion battery based on molten salts

Affordable and scalable energy storage systems are necessary to mitigate the output fluctuation of an electrical power grid integrating intermittent renewable energy sources. Conventional battery technologies are unable to meet the demanding low-cost and long-life span requirements of a grid-scale application, although some of them demonstrated impressive high energy density and capacity. More recently, the prototype of an Al-ion battery has been developed using cheap electrode materials (Al and graphite) in an organic room-temperature ionic liquid electrolyte. Here we implement a different Al-ion battery in an inorganic molten salt electrolyte, which contains only an extremely low-cost and nonflammable sodium chloroaluminate melt working at 120 °C. Due to the superior ionic conductivity of the melt electrolyte and the enhanced Al-ion interaction/deintercalation dynamics at an elevated temperature of 120 °C, the battery delivered a discharge capacity of 190 mA h g−1 at a current density of 100 mA g−1 and showed an excellent cyclic performance even at an extremely high current density of 4000 mA g−1: 60 mA h g−1 capacity after 5000 cycles and 43 mA h g−1 capacity after 9000 cycles, with a coulombic efficiency constantly higher than 99%. The low-cost and safe characteristics, as well as the outstanding long-term cycling capability at high current densities allow the scale-up of this brand-new battery for large-scale energy storage applications.

A Novel Ultrafast Rechargeable Multi-Ions Battery

An ultrafast rechargeable multi-ions battery is presented, in which multi-ions can electrochemically intercalate into graphite layers, exhibiting a high reversible discharge capacity of ≈100 mAh g-1 and a Coulombic efficiency of ≈99% over hundreds of cycles at a high current density. The results may open up a new paradigm for multi-ions-based electrochemical battery technologies and applications.

Direct Conversion of Greenhouse Gas CO2 into Graphene via Molten Salts Electrolysis

Producing graphene through the electrochemical reduction of CO2 remains a great challenge, which requires precise control of the reaction kinetics, such as diffusivities of multiple ions, solubility of various gases, and the nucleation/growth of carbon on a surface. Here, graphene was successfully created from the greenhouse gas CO2 using molten salts. The results showed that CO2 could be effectively fixed by oxygen ions in CaCl2-NaCl-CaO melts to form carbonate ions, and subsequently electrochemically split into graphene on a stainless steel cathode; O2 gas was produced at the RuO2-TiO2 inert anode. The formation of graphene in this manner can be ascribed to the catalysis of active Fe, Ni, and Cu atoms at the surface of the cathode and the microexplosion effect through evolution of CO in between graphite layers. This finding may lead to a new generation of proceedures for the synthesis of high value-added products from CO2, which may also contribute to the establishment of a low-carbon and sustainable world.

3D flower-like NaHTi3O7 nanotubes as high-performance anodes for sodium-ion batteries

The synthesis and electrochemical performance derived from NaHTi3O7 have been investigated for use as an anode material for sodium-ion batteries. NaHTi3O7 nanotubes were fabricated by a hydrothermal method. Galvanostatic charge/discharge measurements were performed in a voltage range of 0.01–2.5 V vs. Na+/Na at different current densities, using the as-prepared NaHTi3O7 nanotubes as the working electrode. Typically, the initial discharge and charge capacities of NaHTi3O7 nanotubes were 381.80 mA h g−1 and 242.82 mA h g−1, respectively, at a current density of 20 mA g−1, and still retained a high specific capacity of 105.32 mA h g−1 and 100.65 mA h g−1 after 100 cycles. The electrode also exhibits outstanding rate capability with a reversible capacity as high as 300.95 mA h g−1 and 209.10 mA h g−1 at current densities of 50 mA g−1 and 100 mA g−1, respectively. The excellent electrochemical stability and high specific capacity of these nanostructured materials have been attributed to the three-dimensional flower-like morphology of NaHTi3O7 nanotubes. All of the findings demonstrate that NaHTi3O7 nanotubes have steady cycling performance and environmental and cost friendliness for use in next generation secondary batteries of sodium-ion batteries.

Electrochemically depositing titanium(III) ions at liquid tin in a NaCl–KCl melt

The electrochemical behavior of titanium ions at a liquid tin cathode has been investigated by cyclic voltammetry and square wave voltammetry in a NaCl–KCl melt at 1023 K. The results show that the deposition potentials of alkali metals and titanium at liquid tin are more positive than those at a solid tungsten cathode. Meanwhile, the results prove that titanium(III) ions can be reduced at liquid tin with a one-step reduction, Ti3+ + 3e = Ti, which is a quasi-reversible process with diffusion-controlled mass transfer. The diffusion coefficient of titanium(III) ions is 1.05 × 10−5 cm2 s−1. Additionally, galvanostatic electrolysis has been carried out to clarify the effect of the current density on the cathodic products. The result demonstrates that a greater depth of titanium will be diffused into the liquid tin cathode during electrolysis with a lower current density.

The electrochemical behavior of an aluminum alloy anode for rechargeable Al-ion batteries using an AlCl3–urea liquid electrolyte

Due to its characteristics of high capacity, low cost, being non-flammable, and involving a three-electron-redox reaction, the aluminum rechargeable battery has received wide attention. Because of these advantages, we focus on a low-cost aluminum alloy anode and detect the discharge/charge reaction mechanism in the aluminum chloride-urea liquid electrolyte at 110–130 °C. The discharge voltage of the battery is about 1.9 V and 1.6 V, and at the current density of 100 mA g−1 the cell can produce a specific capacity of ∼94 mA h g−1. Compared to the pure aluminum anode, the system has a promising future for high efficiency, low-cost energy storage devices.

Production of Ti–Fe alloys via molten oxide electrolysis at a liquid iron cathode

This work studies the direct electrochemical preparation of Ti–Fe alloys through molten oxide electrolysis (MOE) at a liquid iron cathode. Cyclic voltammetry and potentiostatic electrolysis have been employed to study the cathodic process of titanium ions. The results show that cathodic behavior happens during the negative sweep at a potential range from −0.80 to −1.25 V (vs. QRE-Mo), corresponding to the electro-reduction of titanium ions. Importantly, Ti–Fe and titanium-rich Ti–Fe alloys have been successfully produced by galvanostatic electrolysis at different current densities of 0.15 and 0.30 A cm−2, respectively. The results show that it is feasible to directly prepare Ti–Fe alloys by the MOE method at a liquid iron cathode.

Ni0.36Al0.10Cu0.30Fe0.24 Metallic Inert Anode for the Electrochemical Production of Fe-Ni Alloy in Molten K2CO3-Na2CO3

In this paper, a Ni0.36Al0.10Cu0.30Fe0.24 metallic inert anode was proposed and the electrochemical behaviors were studied in molten K2CO3-Na2CO3 at 1023 K by polarization curves and Tafel plots. The results indicated that Ni0.36Al0.10Cu0.30Fe0.24 alloy was stable in carbonate due to the formation of a passivation film on the surface. The film was mainly composed of NiFe2O4 and Al2O3 with a dense structure, which inhibited further corrosion of anode. Moreover, oxygen gas and Fe-Ni alloy have been successfully generated through electrolysis with NiO-Fe2O3 pellet as cathode and Ni0.36Al0.10Cu0.30Fe0.24 alloy as anode under a potential of 1.9 V for 24 hours. Ni0.36Al0.10Cu0.30Fe0.24 alloy exhibited bright prospect as a potential candidate of inert anode for green metallurgical process.