Three-Dimensional Ordered Porous Nanostructures for Lithium-Selenium Battery Cathodes That Confer Superior Energy-Storage Performance

Synthesis of hierarchical porous carbon scaffold derived from red kidney bean peels for advanced Li-Se and Na-Se batteries

Incorporating selenium into high-surface-area carbon with hierarchical pores, derived from red kidney bean peels via simple carbonization/activation, yields a superior Li-Se battery cathode material. This method produces a carbon framework with 568 m2 g-1 surface area, significant pore volume, and improves the composite's electronic conductivity and stability by mitigating volume changes and reducing lithium polyselenide dissolution. The Se@ACRKB composite, containing 45 wt% selenium, shows high discharge capacities (609.13 mAh g-1 on the 2nd cycle, maintaining 470.76 mAh g-1 after 400 cycles at 0.2 C, and 387.58 mAh g-1 over 1000 cycles at 1 C). This demonstrates exceptional long-term stability and performance, also applicable to Na-Se batteries, with 421.36 mAh g-1 capacity after 200 cycles at 0.1 C. Our study showcases the potential of using sustainable materials for advanced battery technologies, emphasizing cost-effective and scalable solutions for energy storage.

A Facile Pre-Lithiated Strategy towards High-Performance Li2Se-LiTiO2 Composite Cathode for Li-Se Batteries

Conventional lithium-ion batteries with a limited energy density are unable to assume the responsibility of energy-structure innovation. Lithium-selenium (Li-Se) batteries are considered to be the next generation energy storage devices since Se cathodes have high volumetric energy density. However, the shuttle effect and volume expansion of Se cathodes severely restrict the commercialization of Li-Se batteries. Herein, a facile solid-phase synthesis method is successfully developed to fabricate novel pre-lithiated Li2Se-LiTiO2 composite cathode materials. Impressively, the rationally designed Li2Se-LiTiO2 composites demonstrate significantly enhanced electrochemical performance. On the one hand, the overpotential of Li2Se-LiTiO2 cathode extremely decreases from 2.93 V to 2.15 V. On the other hand, the specific discharge capacity of Li2Se-LiTiO2 cathode is two times higher than that of Li2Se. Such enhancement is mainly accounted to the emergence of oxygen vacancies during the conversion of Ti4+ into Ti3+, as well as the strong chemisorption of LiTiO2 particles for polyselenides. This facile pre-lithiated strategy underscores the potential importance of embedding Li into Se for boosting electrochemical performance of Se cathode, which is highly expected for high-performance Li-Se batteries to cover a wide range of practical applications.

Hollow carbon spheres loaded with NiSe2 nanoplates as multifunctional SeS2 hosts for Li-SeS2 batteries

Selenium sulfide as a new alternative cathode material can effectively address the inferior electronic conductivity of sulfur, which is the main cause for poor electrochemical reactivity of conventional lithium-sulfur batteries (Li-S batteries). Therefore, in this work, hollow carbon spheres loaded with NiSe₂ nanoplates were prepared as SeS₂ hosts for Li-SeS₂ batteries. The unique micro-mesoporous hollow carbon spheres not only provide channels for the diffusion of SeS₂, but also afford spaces for alleviating the volume expansion of the active substance. Besides, the external polar NiSe₂ nanoplates increase active sites for capturing polysulfides or polyselenides during the charge/discharge process. Meanwhile, the excellent electronic conductivity of NiSe₂ can accelerate the catalytic reaction on the surface, thus reducing the loss of soluble intermediate products and finally suppressing the "shuttle effect". These extraordinary features of the as-proposed cathode offer many superiorities in electrochemical performances in terms of a high initial discharge capacity of 1139 mA h g^-1 at a current rate of 0.1C and an excellent cycling life of up to 1000 cycles at 1C.

Supercritical CO2 Synthesis of Freestanding Se1-x S x Foamy Cathodes for High-Performance Li-Se1-x S x Battery

Selenium-sulfur solid solutions (Se_1-x S _x ) are considered to be a new class of promising cathodic materials for high-performance rechargeable lithium batteries owing to their superior electric conductivity than S and higher theoretical specific capacity than Se. In this work, high-performance Li-Se_1-x S _x batteries employed freestanding cathodes by encapsulating Se_1-x S _x in a N-doped carbon framework with three-dimensional (3D) interconnected porous structure (NC@SWCNTs) are proposed. Se_1-x S _x is uniformly dispersed in 3D porous carbon matrix with the assistance of supercritical CO₂ (SC-CO₂) technique. Impressively, NC@SWCNTs host not only provides spatial confinement for Se_1-x S _x and efficient physical/chemical adsorption of intermediates, but also offers a highly conductive framework to facilitate ion/electron transport. More importantly, the Se/S ratio of Se_1-x S _x plays an important role on the electrochemical performance of Li- Se_1-x S _x batteries. Benefiting from the rationally designed structure and chemical composition, NC@SWCNTs@Se_0.2S_0.8 cathode exhibits excellent cyclic stability (632 mA h g-1 at 200 cycle at 0.2 A g^-1) and superior rate capability (415 mA h g^-1 at 2.0 A g^-1) in carbonate-based electrolyte. This novel NC@SWCNTs@Se_0.2S_0.8 cathode not only introduces a new strategy to design high-performance cathodes, but also provides a new approach to fabricate freestanding cathodes towards practical applications of high-energy-density rechargeable batteries.