Yongxin Huang

Advanced High Energy Density Secondary Batteries with Multi‐Electron Reaction Materials

Secondary batteries have become important for smart grid and electric vehicle applications, and massive effort has been dedicated to optimizing the current generation and improving their energy density. Multi‐electron chemistry has paved a new path for the breaking of the barriers that exist in traditional battery research and applications, and provided new ideas for developing new battery systems that meet energy density requirements. An in‐depth understanding of multi‐electron chemistries in terms of the charge transfer mechanisms occuring during their electrochemical processes is necessary and urgent for the modification of secondary battery materials and development of secondary battery systems. In this Review, multi‐electron chemistry for high energy density electrode materials and the corresponding secondary battery systems are discussed. Specifically, four battery systems based on multi‐electron reactions are classified in this review: lithium‐ and sodium‐ion batteries based on monovalent cations; rechargeable batteries based on the insertion of polyvalent cations beyond those of alkali metals; metal–air batteries, and Li–S batteries. It is noted that challenges still exist in the development of multi‐electron chemistries that must be overcome to meet the energy density requirements of different battery systems, and much effort has more effort to be devoted to this.

Preparation of Prussian Blue Submicron Particles with a Pore Structure by Two-Step Optimization for Na-Ion Battery Cathodes

Traditional Prussian blue (Fe4[Fe(CN)6]3) synthesized by simple rapid precipitation shows poor electrochemical performance because of the presence of vacancies occupied by coordinated water. When the precipitation rate is reduced and polyvinylpyrrolidone K-30 is added as a surface active agent, the as-prepared Prussian blue has fewer vacancies in the crystal structure than in that of traditional Prussian blue. It has a well-defined face-centered-cubic structure, which can provide large channels for Na(+) insertion/extraction. The material, synthesized by slow precipitation, has an initial discharge capacity of 113 mA h g(-1) and maintains 93 mA h g(-1) under a current density of 50 mA g(-1) after 150 charge-discharge cycles. After further optimization by a chemical etching method, the complex nanoporous structure of Prussian blue has a high Brunauer-Emmett-Teller surface area and a stable structure to achieve high specific capacity and long cycle life. Surprisingly, the electrode shows an initial discharge capacity of 115 mA h g(-1) and a Coulombic efficiency of approximately 100% with capacity retention of 96% after 150 cycles. Experimental results show that Prussian blue can also be used as a cathode for Na-ion batteries.

Nature-Inspired Na2Ti3O7 Nanosheets-Formed Three-Dimensional Microflowers Architecture as a High-Performance Anode Material for Rechargeable Sodium-Ion Batteries

Low cycling stability and poor rate performance are two of the distinctive drawbacks of most electrode materials for sodium-ion batteries (SIBs). Here, inspired by natural flower structures, we take advantage of the three-dimensional (3D) hierarchical flower-like stable microstructures formed by two-dimensional (2D) nanosheets to solve these problems. By precise control of the hydrothermal synthesis conditions, a novel three-dimensional (3D) flower-like architecture consisting of 2D Na2Ti3O7 nanosheets (Na-TNSs) has been successfully synthesized. The arbitrarily arranged but closely interlinked thin nanosheets in carnation-shaped 3D Na2Ti3O7 microflowers (Na-TMFs) originate a good network of electrically conductive paths in an electrode. Thus, Na-TMFs can get electrons from all directions and be fully utilized for sodium-ion insertion and extraction reactions, which can improve sodium storage properties with enhanced rate capability and super cycling performance. Furthermore, the large specific surface area provides a high capacity, which can be ascribed to the pseudo-capacitance effect. The wettability of the electrolyte was also improved by the porous and crumpled structure. The remarkably improved cycling performance and rate capability of Na-TMFs make a captivating case for its development as an advanced anode material for SIBs.

A Chemical Precipitation Method Preparing Hollow-Core-Shell Heterostructures Based on the Prussian Blue Analogs as Cathode for Sodium-Ion Batteries

Prussian blue and its analogs are regarded as the promising cathodes for sodium-ion batteries (SIBs). Recently, various special structures are constructed to improve the electrochemical properties of these materials. In this study, a novel architecture of Prussian blue analogs with large cavity and multilayer shells is investigated as cathode material for SIBs. Because the hollow structure can relieve volume expansion and core-shell heterostructure can optimize interfacial properties, the complex structure materials exhibited a highly initial capacity of 123 mA h g-1 and a long cycle life. After 600 cycles, the reversible capacity of the electrode still maintains at 102 mA h g-1 without significant voltage decay, indicating a superior structure stability and sodium storage kinetics. Even at high current density of 3200 mA g-1 , the electrode still delivers a considerable capacity above 52 mA h g-1 . According to the electrochemical analysis and ex-situ measurements, it can be inferred that the enhanced apparent diffusion coefficient and improved insertion/extraction performance of electrode have been obtained by building this new morphology.

Zirconia-supported solid-state electrolytes for high-safety lithium secondary batteries in a wide temperature range

High safety is a long-sought-after goal in the energy storage field. We fabricate a high-safety solid-state electrolyte by in situ immobilizing ionic liquids within a nanoporous zirconia-supported matrix. This ionogel electrolyte provides a combination of the solid-like physical support and liquid-like ionic transport performance, which substantially improves the thermal stability and safety without sacrificing ionic conductivity. Both Raman spectra and density functional theory computations indicate that the zirconia skeleton interacts with the Li salts, promoting the dissociation and transport of Li+. The solid-state cell assembled with this electrolyte possesses excellent cycling performance, with a discharge capacity of 135.9 mA h g−1 after 200 cycles at 30 °C and works well in a wide operating temperature range from −10 to 90 °C. Moreover, the good compatibility and stable interface toward Li–metal anodes in a symmetrical cell demonstrates the usefulness of the electrolyte in Li–metal batteries. These results indicate that this ionogel electrolyte has great promise for application in the energy storage field because of its dramatically improved safety characteristic.

Conductivity and Pseudocapacitance Optimization of Bimetallic Antimony-Indium Sulfide Anodes for Sodium-Ion Batteries with Favorable Kinetics

Abstract Metal sulfides show promise for use in alkali‐ion batteries because of their high theoretical capacities. However, their poor cycling stability and rate performance hinder their further development. To avoid these issues, In2S3 into Sb2S3 is introduced to improve its electrochemical properties by optimizing its crystal structure and sodium storage mechanism. A heterostructure composed of In2S3 and Sb2S3 shows a unique morphology of formicary microspheres, which provide abundant channels for fast transfer of sodium ions, large surface area for a high pseudocapacitance effect, and enough voids to relieve volume expansion. A sodium‐ion battery containing the bimetallic sulfide anode exhibits a high reversible capacity of 400 mA h g−1 and long cycle life of about 1000 cycles. Similarly, a high capacity of ≈610 mA h g−1 is achieved for a lithium‐ion battery containing the anode. During sodiation/desodiation, the synergistic effect of In2S3 and Sb2S3 enhances electronic conductivity and supports the host structure, preventing collapse. The cycling performance and rate performance of the In2S3–Sb2S3 anode are further improved by wrapping the electrode with carbon nanotubes. Even at a high current density of 3.2 A g−1, this carbon composite structure still shows a capacity of about 355 mA h g−1.