Rechargeable Lithium Batteries with Electrodes of Small Organic Carbonyl Salts and Advanced Electrolytes

Rechargeable lithium batteries with organic electrode materials are promising energy storage systems with advantages of structural designability, low cost, renewability, and environmental friendliness. Among the reported organic electrode materials, small organic carbonyl compounds are powerful candidates with high theoretical capacities and fast kinetics. However, these compounds are plagued by high solubility in aprotic electrolytes, which is considered as the main issue leading to capacity decay and short cycling life. Herein we review two major methods to solve this problem, including the preparation of small organic carbonyl salts and optimization of the electrolyte. The polarities of organic electrode materials can be enhanced by forming salts. Thus, the dissolution of the organic compounds in aprotic electrolytes with low polarity is depressed. Meanwhile, optimization of the electrolyte with increasing viscosity can also reduce the dissolution. These two strategies provide guidance for future studies of rechargeable lithium batteries with organic electrode materials

Molecular Electrostatic Potential: A New Tool to Predict the Lithiation Process of Organic Battery Materials

This work is pioneering to introduce molecular electrostatic potential (MESP) to investigate the interaction between lithium ions and organic electrode molecules. The electrostatic potential on the van der Waals surface of the electrode molecule is calculated, and then the coordinates and relative values of the local minima of MESP can be correlated to the Li binding sites and sequence on an organic small molecule, respectively. This suggests a gradual lithiation process. Similar calculations are extended to polymers and even organic crystals. The operation process of MESP for these systems is explained in detail. Through providing accurate and visualizable lithium binding sites, MESP can give precise prediction of the lithiated structures and reaction mechanism of organic electrode materials. It will become a new theoretical tool for determining the feasibility of organic electrode materials for alkali metal ion batteries

Na⁺‑Enriched Quinoid Polymer Layer with Fast Ion Transport for Dendrite-Free Sodium Metal Batteries with High Cyclic Stability

An unstable solid electrolyte interphase (SEI) layer on a metal electrode leads to issues of severe dendrite formation and side reactions, resulting in low cycle stability and safety hazards of metal-based batteries. Herein, a functional quinoid polymer (poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene), PDBM) is introduced on the surface of Na/Li metal, forming a flexible and uniform polymer–salt (PDBM-Na/Li)-based SEI with Na+/Li+ enriching property and low ion dissociation energy. The PDBM-Na layer enables a stable Na plating/stripping behavior with over 1200 h cycles at 2 mA cm–2 and Na∥Na3V2(PO4)3 full batteries with a capacity retention of 93% after 2400 cycles at 5 C. Equally important, a comparison study of PDBM-Na/Li layers on the cycling stability of Na/Li metals demonstrates that not only an appropriate ion adsorption energy but also a low dissociation energy is important for extending the cyclic lifespan of metal electrodes. This study provides deep insights into the structural design of functional polymers for alkaline anode protection