Anatase TiO₂: Better Anode Material Than Amorphous and Rutile Phases of TiO₂ for Na-Ion Batteries

Amorphous TiO₂@C nanospheres were synthesized via a template approach. After being sintered under different conditions, two types of polyphase TiO₂ hollow nanospheres were obtained. The electrochemical properties of the amorphous TiO₂ nanospheres and the TiO₂ hollow nanospheres with different phases were characterized as anodes for the Na-ion batteries. It was found that all the samples demonstrated excellent cyclability, which was sustainable for hundreds of cycles with little capacity fading, although the anatase TiO₂ presented a capability that was better than that of the mixed anatase/rutile TiO₂ or the amorphous TiO₂@C. Through crystallographic analysis, it was revealed that the anatase TiO₂ crystal structure supplies two-dimensional diffusion paths for Na-ion intercalation and more accommodation sites. Density functional theory calculations indicated lower energy barriers for the insertion of Na⁺ into anatase TiO₂. Therefore, anatase TiO₂ hollow nanospheres show excellent high-rate performance. Through <i>ex situ</i> field emission scanning electron microscopy, it was revealed that the TiO₂ hollow nanosphere architecture can be maintained for hundreds of cycles, which is the main reason for its superior cyclability

The protective effect and its mechanism for electrolyte additives on the anode interface in aqueous zinc-based energy storage devices

Aqueous-electrolyte-based zinc-ion batteries (ZIBs), which have significant advantages over other batteries, including low cost, high safety, high ionic conductivity, and a natural abundance of zinc, have been regarded as a potential alternative to lithium-ion batteries (LIBs). ZIBs still face some critical challenges, however, especially for building a reversible zinc anode. To address the reversibility of zinc anode, great efforts have been made on intrinsic anode engineering and anode interface modification. Less attention has been devoted to the electrolyte additives, however, which could not only significantly improve the reversibility of zinc anode, but also determine the viability and overall performance of ZIBs. This review aims to provide an overview of the two main functions of electrolyte additives, followed by details on six reasons why additives might improve the performance of ZIBs from the perspectives of creating new layers and regulating current plating/stripping processes. Furthermore, the remaining difficulties and potential directions for additives in aqueous ZIBs are also highlighted

Non-precious metal electrocatalysts for two-electron oxygen electrochemistry: Mechanisms, progress, and outlooks

Hydrogen peroxide (H2O2) is a valuable chemical for a wide variety of applications. The environmentally friendly production route of the electrochemical reduction of O2 to H2O2 has become an attractive alternative to the traditional anthraquinone process. The efficiency of electrosynthesis process depends considerably on the availability of cost-effective catalysts with high selectivity, activity, and stability. Currently, there are many outstanding issues in the preparation of highly selective catalysts, the exploration of the interface electrolysis environment, and the construction of electrolysis devices, which have led to extensive research efforts. Distinct from the existing few comprehensive review articles on H2O2 production by two-electron oxygen reduction, the present review first explains the principle of the oxygen reduction reaction and then highlights recent advances in the regulation and control strategies of different types of catalysts. Key factors of electrode structure and device design are discussed. In addition, we highlight the promising co-production combination of this system with renewable energy or energy storage systems. This review can help introduce the potential of oxygen reduction electrochemical production of high-flux H2O2 to the commercial market

Strategies for boosting carbon electrocatalysts for the oxygen reduction reaction in non-aqueous metal-air battery systems

Carbon-based materials stand out from all possible non-precious metal-based oxygen reduction reaction (ORR) catalysts, owing to their low cost, high conductivity, and variety of allotropes with different bonding and structures. There have been many reviews on the ORR performance of carbon-based materials in aqueous electrolyte, but until now, there has been no specific review on the ORR activity of carbon-based materials in non-aqueous electrolyte. In this review, a comprehensive insight into carbon-based catalysts for the ORR in non-aqueous electrolyte in terms of the ORR mechanism and strategies for performance modulation (including morphology/nanostructure engineering, strategies for doping with foreign atoms, defect engineering, and functionalization engineering) is provided. Also, the challenges for carbon electrocatalysts in non-aqueous electrolyte and the corresponding solutions are also discussed

Homologous Nitrogen-Doped Hierarchical Carbon Architectures Enabling Compatible Anode and Cathode for Potassium-Ion Hybrid Capacitors

Potassium-ion hybrid capacitors (PIHCs) have been considered as an emerging device to render grid-scale energy storage. Nevertheless, the sluggish kinetics at the anode side and limited capacity output at the cathode side remain daunting challenges for the overall performances of PIHCs. Herein, an exquisite “homologous strategy” to devise multi-dimensional N-doped carbon nanopolyhedron@nanosheet anode and activated N-doped hierarchical carbon cathode targeting high-performance PIHCs is reported. The anode material harnessing a dual-carbon structure and the cathode candidate affording a high specific surface area (2651 m2 g−1) act in concert with a concentrated ether-based electrolyte, resulting in an excellent half cell performance. The related storage mechanism is systematically revealed by in situ electrokinetic characterizations. More encouragingly, the thus-derived PIHC full cell demonstrates a favorable energy output (157 Wh kg−1), showing distinct advantages over the state-of-the-art PIHC counterparts

Research progress in stable interfacial constructions between composite polymer electrolytes and electrodes

Composite polymer electrolytes (CPEs) have great commercialization potential because they can take advantage of the properties of inorganic and polymer electrolytes, which enable them to realize relatively high ionic conductivity, better electrode contacts, and superior mechanical strength. Nevertheless, the interface between the CPE and the electrode material remains a key challenge that obstructs the further practical development of polymer solid-state lithium batteries (PSSBs). This is because the continuous side reactions between the electrode materials and the CPE can result in unstable interfaces during cycling, thus affecting the electrochemical performance of the battery. Here, in this review, recent advances in various interfacial constructions are reviewed, including the modification of electrode materials and optimization of CPEs. Furthermore, we specifically focus on the underlying mechanisms of the interfacial contact, ionic migration, and electrochemical reactions between the electrodes and the CPE. It is hoped that this review can stimulate greater progress towards an in-depth understanding of this interfacial issue for CPEs, which could provide specific solutions for improving the electrochemical performances of PSSBs

Metallic Transition Metal Dichalcogenides of Group VIB: Preparation, Stabilization, and Energy Applications

Layered transition metal dichalcogenides (TMDs) of group VIB have been widely used in the realms of energy storage and conversions. Along with the existence of semiconducting states, their metallic phases have recently attracted numerous attentions owing to their fascinating physical and chemical properties. Many efforts have been devoted to obtain metallic TMDs with high purity and yield. Nevertheless, such metallic phase is thermodynamically metastable and tends to convert into semiconducting phase, which necessitates the exploration over effective strategies to ensure the stability. In this review, typical fabrication routes are introduced and those critical factors during preparation are elaborately discussed. Moreover, the stabilized strategies are summarized with concrete examples highlighting the key mechanisms toward efficient stabilization. Finally, emerging energy applications are overviewed. This review presents comprehensive research status of metallic group VIB TMDs, aiming to facilitate further scientific investigations and promote future practical applications in the fields of energy storage and conversion

Enhanced Reaction Kinetics and Structure Integrity of Ni/SnO₂ Nanocluster toward High-Performance Lithium Storage

SnO₂ is regarded as one of the most promising anodes via conversion-alloying mechanism for advanced lithium ion batteries. However, the sluggish conversion reaction severely degrades the reversible capacity, Coulombic efficiency and rate capability. In this paper, through constructing porous Ni/SnO₂ composite electrode composed of homogeneously distributed SnO₂ and Ni nanoparticles, the reaction kinetics of SnO₂ is greatly enhanced, leading to full conversion reaction, superior cycling stability and improved rate capability. The uniformly distributed Ni nanoparticles provide a fast charge transport pathway for electrochemical reactions, and restrict the direct contact and aggregation of SnO₂ nanoparticles during cycling. In the meantime, the void space among the nanoclusters increases the contact area between the electrolyte and active materials, and accommodates the huge volume change during cycling as well. The Ni/SnO₂ composite electrode possesses a high reversible capacity of 820.5 mAh g^–1 at 1 A g^–1 up to 100 cycles. More impressively, large capacity of 841.9, 806.6, and 770.7 mAh g^–1 can still be maintained at high current densities of 2, 5, and 10 A g^–1 respectively. The results demonstrate that Ni/SnO₂ is a high-performance anode for advanced lithium-ion batteries with high specific capacity, excellent rate capability, and cycling stability

Revealing the interfacial chemistry of silicon anodes with polysiloxane electrolyte additives

Silicon (Si) anodes are promising in lithium-ion batteries owing to their high specific capacity and suitable voltage platform. However, particle volume expansion (>300 %) and the continuous consumption of Li+ to form new interfacial layers result in poor cycle performance. We report a sustainable low-cost Si material derived from photovoltaic cutting waste, showing a high initial Coulombic efficiency (86.9 %). The cycle stability of Si/graphite is enhanced in terms of a 38 % capacity retention increase in the presence of vinyl-terminated polydimethylsiloxane (Vi-PDMS) additive. The C = C bond in Vi-PDMS plays a role in reacting with hydrogen fluoride (HF) by-products to prevent the side reaction between HF and solvent. The decomposed macromolecule Si-containing Li salt serves as a part of the solid electrolyte interphase film and has low interface resistance. This formed interphase layer effectively mitigates stress concentration at the contact surface between silicon particles and the current collector caused by expansion forces

Recent progress and strategic perspectives of inorganic solid electrolytes: fundamentals, modifications, and applications in sodium metal batteries

Solid-state electrolytes (SEs) have attracted overwhelming attention as a promising alternative to traditional organic liquid electrolytes (OLEs) for high-energy-density sodium-metal batteries (SMBs), owing to their intrinsic incombustibility, wider electrochemical stability window (ESW), and better thermal stability. Among various kinds of SEs, inorganic solid-state electrolytes (ISEs) stand out because of their high ionic conductivity, excellent oxidative stability, and good mechanical strength, rendering potential utilization in safe and dendrite-free SMBs at room temperature. However, the development of Na-ion ISEs still remains challenging, that a perfect solution has yet to be achieved. Herein, we provide a comprehensive and in-depth inspection of the state-of-the-art ISEs, aiming at revealing the underlying Na+ conduction mechanisms at different length scales, and interpreting their compatibility with the Na metal anode from multiple aspects. A thorough material screening will include nearly all ISEs developed to date, i.e., oxides, chalcogenides, halides, antiperovskites, and borohydrides, followed by an overview of the modification strategies for enhancing their ionic conductivity and interfacial compatibility with Na metal, including synthesis, doping and interfacial engineering. By discussing the remaining challenges in ISE research, we propose rational and strategic perspectives that can serve as guidelines for future development of desirable ISEs and practical implementation of high-performance SMBs