For lithium-selenium batteries, commercial applications are hindered by the inferior electrical conductivity of selenium and the low utilization ratio of the active selenium. Here, we report a new baked-in-salt approach to enable Se to better infiltrate into metal-complex-derived porous carbon (Se/MnMC-B). The approach uses the confined, narrow space that is sandwiched between two compact NaCl solid disks, thus avoiding the need for protection with argon or a vacuum environment during processing. The electrochemical properties for both lithium and sodium storage of our Se/MnMC-B cathode were found to be outstanding. For lithium storage, the Se/MnMC-B cathode (with 72% selenium loading) exhibited a capacity of 580 mA h g⁻¹ after 1000 cycles at 1 C, and an excellent rate capability was achieved at 20 C and 510 mA h g⁻¹. For sodium storage, a specific capacity of 535 mA h g⁻¹ was achieved at 0.1 C after 150 cycles. These results demonstrate the potential of this approach as a new effective general synthesis method for confining other low melting point materials into a porous carbon matrix.

Crystalline Si nanoparticles are prepared by reduction of SiCl₄ with metallic magnesium in the molten salt of AlCl₃ at 200 °C in an autoclave. AlCl₃ not only acts as molten salt, but also participates in the reaction. The related experiments confirm that metallic Mg reduces AlCl₃ to create nascent Al which could immediately reduce SiCl₄ to Si, and the by-product MgCl₂ would combine with AlCl₃ forming complex of MgAl₂Cl₈. As anode for rechargeable lithium ion batteries, the as-prepared Si delivers the reversible capacity of 3083 mAh g⁻¹ at 1.2 A g⁻¹ after 50 cycles, and 1180 mAh g⁻¹ at 3 A g⁻¹ over 500 cycles.

Crystalline Si nanoparticles are prepared by reduction of SiCl₄ with metallic magnesium in the molten salt of AlCl₃ at 200 °C in an autoclave. AlCl₃ not only acts as molten salt, but also participates in the reaction. The related experiments confirm that metallic Mg reduces AlCl₃ to create nascent Al which could immediately reduce SiCl₄ to Si, and the by-product MgCl₂ would combine with AlCl₃ forming complex of MgAl₂Cl₈. As anode for rechargeable lithium ion batteries, the as-prepared Si delivers the reversible capacity of 3083 mAh g⁻¹ at 1.2 A g⁻¹ after 50 cycles, and 1180 mAh g⁻¹ at 3 A g⁻¹ over 500 cycles.

Ferric chloride-graphite intercalation compounds (FeCl₃–GICs) with stage 1 and stage 2 structures were synthesized by reacting FeCl₃ and expanded graphite (EG) in air in a stainless-steel autoclave. As rechargeable Li-ion batteries, these FeCl₃–GICs exhibit high capacity, excellent cycling stability, and superior rate capability, which could be attributed to their unique intercalation features. This work may enable new possibilities for the fabrication of Li-ion batteries.

A new thread for improving the cycling stability of Fe₂O₃ nanorice is proposed through combining the electrochemical porousness (EP) effect and solid–electrolyte interphase (SEI) thermolysis approach. Starting from solid Fe₂O₃ nanorice, this process could be applied to prepare porous Fe₂O₃ nanorice with a good coating of a porous SEI thermolysis layer composed of carbon and Li₂O. The interconnecting pores and full coating of the SEI thermolysis layer provides not only mechanical resistance of the Fe₂O₃ nanorice against pulverization, but also high electrical and ionic conductivity over the electrode throughout long cell cycles. This method results in the enhancement of cycling ability and capacity, which is demonstrated by comparison with the starting Fe₂O₃ nanorice. After the EP and SEI thermolysis approach, the Fe₂O₃ nanorice exhibits an energy capacity retention about of 680 mAh g⁻¹ at a current density of 1000 mA g⁻¹ over 250 cycles, which is more than 82 % of the initial reversible capacity. Moreover, it also has an excellent rate capability and high coulombic efficiency. This strategy provides a simple and convenient route toward stable charge/discharge cycling for not only Fe₂O₃, but also for other electrode materials that are subject to large volume changes and low charge voltages. At the same time, it also contributes to a fundamental understanding of improved cycling stability and reversible capacity for electrode materials.

Carbon nanoplates with diameters and thicknesses of up to approximately 1.2 μm and 18 nm, respectively, were prepared by a reaction using CaC₂, ferrocene, and NH₄HCO₃ as starting materials at 600 °C for 10 h. These carbon nanoplates form aggregates that have a specific surface area of up to 831 m² g^–1 and a specific capacitance of up to 184 F g^–1 at a scanning rate of 10 mV s^–1 in a 3 mol L^–1 H₂SO₄ solution. Without using NH₄HCO₃, hexagonal carbon nanoplates with an average edge length of 500 nm and thickness of approximately 22 nm were obtained with a specific capacitance of up to 42 F g^–1. If NaN₃ or NaHCO₃ was used instead of NH₄HCO₃, carbon nanoplates with a curved surface or irregular circular carbon nanoplates were obtained with specific capacitances of 87 or 36 F g^–1, respectively.