Achieving High Initial Coulombic Efficiency and Capacity in a Surface Chemical Grafting Layer of Plateau-type Sodium Titanate

The plateau-type sodium titanate with suitable sodiation potential is a promising anode candidate for high safe and high energy density of sodium-ion batteries (SIBs). However, the poor initial Coulombic efficiency (ICE) and cyclic instability of sodium titanate are attributed to the unstable interfacial structure along with the decomposition of electrolytes, resulting in the continuous formation of solid electrolyte interface (SEI) film. To address this issue, a chemical grafting method is developed to fabricate a highly stable interface layer of inert Al2O3 on the sodium titanate anode, rendering the high ICE and excellent cycling stability. Based on theoretical calculations, NaPF6 are more likely adsorption on the Al2O3 surface and produce sodium fluoride. The formation of a thin and dense SEI film with rich sodium fluoride achieves the low interfacial resistances and charge-transfer resistances. Benefitting from our design, the obtained sodium titanate exhibits a high ICE from 67.7 % to 79.4 % and an enhanced reversible capacity from 151 mAh g-1 to 181 mAh g-1 at 20 mA g-1, along with an increase in capacity retention from 56.5 % to 80.6 % after 500 cycles. This work heralds a promising paradigm for rational regulation of interfacial stability to achieve high-performance anodes for SIBs.

Eliciting Specific Electrochemical Reaction Behavior by Rational Design of a Red Phosphorus Electrode for Sodium-Ion Batteries

Due to the demand to upgrade from lithium-ion batteries (LIB), sodium-ion batteries (SIB) have been paid considerable attention for their high-energy, cost-effective, and sustainable battery system. Red phosphorus is one of the most promising anode candidates for SIBs, with a high theoretical specific capacity of 2596 mAh g⁻¹ and in the discharge potential range of 0.01–0.8 V; however, it suffers from a low electrical conductivity, a substantial expansion of volume (~300%), and sluggish electron/ion kinetics. Herein, we have designed a well-defined electrode, which consists of red phosphorus, nanowire arrays encapsulated in the vertically aligned carbon nanotubes (P@C NWs), which were fabricated via a two-step, anodized-aluminum oxide template. The designed anode achieved a high specific capacity of 2250 mAh g⁻¹ (87% of the theoretical capacity), and a stepwise analysis of the reaction behavior between sodium and red phosphorus was demonstrated, both of which have not been navigated in previous studies. We believe that our rational design of the red phosphorus electrode elicited the specific reaction mechanism revealed by the charge–discharge profiles, rendered excellent electrical conductivity, and accommodated volume expansion through the effective nano-architecture, thereby suggesting an efficient structure for the phosphorus anode to advance in the future.

Defect engineering of oxide perovskites for catalysis and energy storage: synthesis of chemistry and materials science

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Cr2P2O7 as a Novel Anode Material for Sodium and Lithium Storage

The development of new appropriate anode material with low cost is still main issue for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). Here, Cr2P2O7 with an in-situ formed carbon layer has been fabricated through a facile solid-state method and its storage performance in SIBs and LIBs has been reported first. The Cr2P2O7@C delivers 238 mA h g-1 and 717 mA h g-1 at 0.05 A g-1 in SIBs and LIBs, respectively. A capacity of 194 mA h g-1 is achieved in SIBs after 300 cycles at 0.1 A g-1 with a high capacity retention of 92.4%. When tested in LIBs, 351 mA h g-1 is maintained after 600 cycles at 0.1 A g-1. The carbon coating layer improves the conductivity and reduces the side reaction during the electrochemical process, and hence improves the rate performance and enhances the cyclic stability.

Construction of the NaTi2(PO4)3/C electrode with a one-dimensional porous hybrid structure as an advanced anode for sodium-ion batteries

The inferior electronic conductivity of NASICON materials leads to poor cyclability and rate capability, which severely inhibits their extensive development. Therefore, we have developed a one-dimensional (1D) hybrid electrode material that combines small NaTi2(PO4)3 nanoparticles (5-50 nm) with a porous carbon matrix using a controllable sol-gel strategy. This unique design enables the electrode to possess good structural stability, superior charge transfer kinetics, and low polarization. The intimate combination between the nanoparticles and the porous carbon matrix can effectively facilitate Na+/e- transfer and accommodate volume variation during cycling. The construction of the new structure presented in this work will extend the applications of the NaTi2(PO4)3 system. Furthermore, the formed hybrid structure has potential to be a universal model for various electrode materials.

Li(Na)2FeSiO4/C hybrid nanotubes: promising anode materials for lithium/sodium ion batteries

Porous Li(Na)₂FeSiO₄/C hybrid nanotubes were successfully synthesized by a modified sol–gel strategy and a subsequent calcination process. These nanohybrids exhibited excellent electrochemical performances as anodes for lithium/sodium ion batteries.

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

A novel anthracene-based tetraperimidine hexafluorophosphate 3 was prepared, and its structure was determined through X-ray analysis, HRMS as well as ¹H and ¹³C NMR spectroscopy. In the cationic moiety of 3, two (N-ethylperimidinyl–C₂H₄)₂NCH₂– arms were attached to the 9- and 10-positions of anthracene. In addition, compound 3 was used as a chemosensor to research the ability to recognize Cr³⁺ through fluorescence and UV titrations, HRMS, as well as ¹H NMR and IR spectroscopy. The results indicate that 3 is an effective chemosensor for Cr³⁺.

2D ultrathin carbon nanosheets with rich N/O content constructed by stripping bulk chitin for high-performance sodium ion batteries

Two-dimensional (2D) nanomaterials hold considerable potential in reforming the energy storage performance, and the efficient production of high-performance 2D energy storage materials through facile and sustainable approaches is highly desirable. Herein, for the first time, large-area and ultrathin carbon nanosheets doped with N/O were constructed by stripping bulk chitin via a "top-down" method. On the basis of the specific layered structure composed of nanofibers, chitin samples after removing the protein and CaCO₃ could be efficiently exfoliated into nanosheets (CNs) via the hydrothermal method, which were then carbonized into N/O co-doped porous carbon nanosheets (CCNs). The CCNs with a thickness of about 3.8 nm retained the original nanosheet structure consisting of nanofibers, leading to a 2D structure with hierarchical porosities. When used as anode materials for sodium-ion batteries, the 2D porous nanostructures and abundant N/O doping of CCNs-600 (carbonized at 600 °C) enable a high reversible capacity of 360 mA h g^-1 at 50 mA g^-1, a good rate capability of 102 mA h g^-1 at 10 A g^-1, and an excellent cycling stability of 140 mA h g^-1 after 10 000 cycles at a high density of 5 A g^-1. Full cells consisting of a CCN anode and a Na₃V₂(PO₄)₃/C cathode exhibited favorable rate performance and cycling stability, showing potential application prospects in highly efficient energy storage systems.

Electrode Materials for High-Performance Sodium-Ion Batteries

Sodium ion batteries (SIBs) are being billed as an economical and environmental alternative to lithium ion batteries (LIBs), especially for medium and large-scale stationery and grid storage. However, SIBs suffer from lower capacities, energy density and cycle life performance. Therefore, in order to be more efficient and feasible, novel high-performance electrodes for SIBs need to be developed and researched. This review aims to provide an exhaustive discussion about the state-of-the-art in novel high-performance anodes and cathodes being currently analyzed, and the variety of advantages they demonstrate in various critically important parameters, such as electronic conductivity, structural stability, cycle life, and reversibility.