Doped graphene encapsulated SnP2O7 with enhanced conversion reactions from polyanions as a versatile anode material for sodium dual-ion battery

Strategies for improving cathode electrolyte interphase in high-performance dual-ion batteries

Dual-ion batteries (DIBs) offer high energy density due to the ability to intercalate both anions and cations, thereby increasing the cutoff voltage and battery capacity. Graphite, with its ordered layered structure and cost-effectiveness, is commonly employed as the cathode material for DIBs. However, the discharge capacity of graphite cathodes is relatively low, and their cycling stability is poor, limiting the practical applications of DIBs. The formation of cathode electrolyte interphase (CEI) on the graphite cathode surface is closely related to anion behavior. Constructing a stable cathode electrolyte interface is crucial for improving the stability of anion storage. Therefore, we introduce a series of strategies to enhance the quality of the CEI layer, including additives, binders, main salts or solvents, high-concentration electrolytes, doping elements, artificial CEI, and graphite surface modifications. These strategies improve the CEI by enhancing anion transport rates, increasing anion solvation capabilities, and improving the structural stability of graphite cathodes, which is of profound significance for increasing the capacity and stability of DIBs. This review provides inspiration for future CEI research, encouraging further exploration of resources of CEI components and improvement strategies to further promote the development of DIBs technology.

Heteroatom Codoped Graphene: The Importance of Nitrogen

Although graphene has exceptional properties, they are not enough to solve the extensive list of pressing world problems. The substitutional doping of graphene using heteroatoms is one of the preferred methods to adjust the physicochemical properties of graphene. Much effort has been made to dope graphene using a single dopant. However, in recent years, substantial efforts have been made to dope graphene using two or more dopants. This review summarizes all the hard work done to synthesize, characterize, and develop new technologies using codoped, tridoped, and quaternary doped graphene. First, I discuss a simple question that has a complicated answer: When can an atom be considered a dopant? Then, I briefly discuss the single atom doped graphene as a starting point for this review's primary objective: codoped or dual-doped graphene. I extend the discussion to include tridoped and quaternary doped graphene. I review most of the systems that have been synthesized or studied theoretically and the areas in which they have been used to develop new technologies. Finally, I discuss the challenges and prospects that will shape the future of this fascinating field. It will be shown that most of the graphene systems that have been reported involve the use of nitrogen, and much effort is needed to develop codoped graphene systems that do not rely on the stabilizing effects of nitrogen. I expect that this review will contribute to introducing more researchers to this fascinating field and enlarge the list of codoped graphene systems that have been synthesized.

A redox-active metal-organic compound for lithium/sodium-based dual-ion batteries

Currently, there is considerable interest in developing new electrode materials to construct the new-generation dual-ion batteries (DIBs) with the potential advantages of higher working voltage, good safety, low cost, and environmental friendliness. Herein, a well-known charge-transfer metal-organic compound, copper-tetracyanoquinodimethane (CuTCNQ), is synthesized and then used as an anode material, which can reversibly store Li⁺/Na⁺ ions under the lower working voltage. Consequently, the lithium/sodium-based DIBs (LDIBs/SDIBs) are constructed by coupling CuTCNQ anode with graphite cathode and their working mechanisms are also understood in detail. As expected, LDIBs exhibit a high average potential of 4.26 V, a high initial discharge capacity of 195.4 mAh g^-1 at 0.1 A g^-1, long cycling performance after 200 cycles with good capacity retention and excellent rate capability of 106.2 mAh g^-1 at 5 A g^-1. Especially, high average potential of 4.23 V and good rate capability of 34.5 mAh g^-1 at 5 A g^-1 could be maintained in SDIBs. These results may open a new avenue for using metal-organic compound in the field of high-performance energy-storage devices.