Reversible Intercalation of 1‐Ethyl‐3‐methylimidazolium Cations into MoS2from a Pure Ionic Liquid Electrolyte for Dual‐Ion Cells

Stable organic polymer anode for high rate and fast charge sodium based dual-ion battery

Considering the extensive resources, flexible structural designability, and abundant active sites, organic electrodes have been considered as the ideal sodium storage materials. However, organic materials generally face the limitations of unstable and dissolved characteristic, leading to a poor cyclic stability. In this work, we proposed a carbon nanotube (CNT) modified polyimide as the anode for sodium-based dual-ion battery (SDIB). The polyimide remains well the structure and morphology of monomer with a stable conjugated structure and high degree of crystallinity, effectively enhancing the electrochemical performance of the SDIBs. Also, the cooperation with CNT particularly improves the ion conductivity of the anode and advances the rate performance. Combined with an ionic liquid electrolyte, the constructed dual-ion battery exhibits excellent rate capability, high specific discharge capacity and stable cycling performance. It delivers a specific discharge capacity of 119.3 mA h g-1 at 0.2 C (1 C=100 mA g-1 ) and still has a specific discharge capacity of 82.3 mA h g-1 even after 1000 cycles at 10 C. Besides, the system displays a low self-discharge rate and stable fast charging performance, which is expected to be applied in the large-scale electrochemical energy storage devices and inspire the future development of SDIBs.

Sodium-Based Dual-Ion Battery Based on the Organic Anode and Ionic Liquid Electrolyte

Combining the advantages of dual-ion batteries (DIBs) and sodium-ion batteries (SIBs), we herein develop a superior sodium-based dual-ion battery (Na-DIB) based on the PTCDA organic anode and ionic liquid (IL) electrolyte. The system shows the highest specific discharge capacity of 177 mAh g^-1 at 0.5C and excellent capacity retention over 100% at 2C after 200 cycles. Notably, even at an ultrahigh rate of 20C, the battery still maintains a considerable capacity of 60 mAh g^-1 with a coulombic efficiency (CE) close to 100 and 94% capacity retention after 1000 cycles. Moreover, the self-discharge of the system has been investigated and shown to have an extremely low value of 0.18% h^-1. Consequently, this work presents an excellent Na-DIB system, which could be a promising candidate for large-scale applications.

Metal Assisted Synthesis of Cationic Sulfidobismuth Cubanes in Ionic Liquids

Bi2 S3 was dissolved in the presence of either AuCl/PtCl2 or AgCl in the ionic liquids [BMIm]Cl ⋅ xAlCl3 (BMIm=1-n-butyl-3-methylimidazolium; x=4-4.3) through annealing the mixtures at 180 or 200 °C. Upon cooling to room temperature, orange, air-sensitive crystals of [BMIm](Bi4 S4 )[AlCl4 ]5 (1) or Ag(Bi7 S8 )[S(AlCl3 )3 ]2 [AlCl4 ]2 (2) precipitated, respectively. 1 did not form in the absence of AuCl/PtCl2 , suggesting an essential role of the metal cations. X-ray diffraction on single-crystals of 1 revealed a monoclinic crystal structure that contains (Bi4 S4 )4+ heterocubanes and [AlCl4 ]- tetrahedra as well as [BMIm]+ cations. The intercalation of the ionic liquid was confirmed via solid state NMR spectroscopy, revealing unusual coupling behavior. The crystal structure of 2 consists of (Bi7 S8 )5+ spiro-dicubanes, [S(AlCl3 )3 ]2- tetrahedra triples, isolated [AlCl4 ]- tetrahedra, and heavily disordered silver(I) cations. No cation ordering took place in 2 upon slow cooling to 100 K.

Three-Dimensional Molecular Mapping of Ionic Liquids at Electrified Interfaces

Electric double layers (EDLs), occurring ubiquitously at solid-liquid interfaces, are critical for electrochemical energy conversion and storage processes such as capacitive charging and redox reactions. However, to date the molecular-scale structure of EDLs remains elusive. Here we report an advanced technique, electrochemical three-dimensional atomic force microscopy (EC-3D-AFM), and use it to directly image the molecular-scale EDL structure of an ionic liquid under different electrode potentials. We observe not only multiple discrete ionic layers in the EDL on a graphite electrode but also a quasi-periodic molecular density distribution within each layer. Furthermore, we find pronounced 3D reconfiguration of the EDL at different voltages, especially in the first layer. Combining the experimental results with molecular dynamics simulations, we find potential-dependent molecular redistribution and reorientation in the innermost EDL layer, both of which are critical to EDL capacitive charging. We expect this mechanistic understanding to have profound impacts on the rational design of electrode-electrolyte interfaces for energy conversion and storage.

High-Performance Phosphorus-Graphite Dual-Ion Battery

Recently, dual-ion batteries (DIBs) are regarded as a promising alternative to well-developed lithium-ion batteries, and the development of high-performance and abundant-sodium-based DIBs (SDIBs) is being intensively pursued. In this work, a novel SDIB composed of a phosphorus (P)-based anode and graphite (G) cathode is successfully constructed for the first time. This P-G SDIB shows a high working voltage of around 3.9 V, a high reversible capacity of 373 mA h/g, good rate capability, and long cyclability, which are superior to those of the most reported DIBs. The ex situ X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy tests reveal the insertion/extraction mechanism of Na⁺ ions into/from P-based anodes via reversible Na-P alloying reactions accompanied with high charge-storage capability. Moreover, the presodiation of P-based composites is found to be an efficient approach to boost the cycling performance of the P-G SDIB by forming a stable NaF-rich solid electrolyte interphase layer to alleviate electrolyte decomposition. Our results demonstrate that P-based SDIBs possess tremendous potential for practical electrochemical energy-storage applications.

Reversible interaction of 1-butyl-1-methylpyrrolidinium cations with 5,7,12,14-pentacenetetrone from a pure ionic liquid electrolyte for dual-ion batteries

An organic dual-ion battery with a 5,7,12,14-pentacenetetrone anode for the reversible interaction of 1-butyl-1-methylpyrrolidinium cations was designed, which showed a low self-discharge rate of 4.68% per h, a high discharge capacity of 164.5 mA h g-1, and a superior capacity retention of 92.2% after 100 cycles at 5C.