Table of Content

20 December 2022, Volume 5 Issue 4

Previous Issue   

Innovative Strategies for Overall Water Splitting Using Nanostructured Transition Metal Electrocatalysts

Asad Ali, Fei Long, Pei Kang Shen

2022, 5(4):  1.  doi:10.1007/s41918-022-00136-8

Asbtract ( 2121 )   PDF  

Related Articles | Metrics

Electrochemical water splitting is regarded as the most auspicious technology for renewable sources, transport, and storage of hydrogen energy. Currently, noble Pt metal and noble-metal oxides (IrO₂ and RuO₂) are recognized as state-of-the-art electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Searching for earth-abundant electrocatalysts for the HER and OER with remarkable performance and high stability to replace precious metals plays a significant role in the commercial application of electrochemical water splitting. In this review, recent advancements in nanostructured transition metal electrocatalysts are assessed through the selected examples of nitrides, carbides, phosphides, sulfides, borides, layered double hydroxides, and oxides. Recent breakthroughs in nanostructured transition metal electrocatalysts are discussed in terms of their mechanisms, controllable production, structural design, and innovative strategies for boosting their performance. For instance, most nanostructured transition metal electrocatalysts for overall water splitting (OWS) only function well in neutral and alkaline solutions. Finally, current research challenges and future perspectives for increasing the performance of nanostructured transition metals for OWS are proposed.



Surface Doping vs. Bulk Doping of Cathode Materials for Lithium-Ion Batteries: A Review

Huaming Qian, Haoqi Ren, Ying Zhang, Xianfeng He, Wenbin Li, Jingjing Wang, Junhua Hu, Hong Yang, Hirbod Maleki Kheimeh Sari, Yu Chen, Xifei Li

2022, 5(4):  2.  doi:10.1007/s41918-022-00155-5

Asbtract ( 2007 )   PDF  

Related Articles | Metrics

To address the capacity degradation, voltage fading, structural instability and adverse interface reactions in cathode materials of lithium-ion batteries (LIBs), numerous modification strategies have been developed, mainly including coating and doping. In particular, the important strategy of doping (surface doping and bulk doping) has been considered an effective strategy to modulate the crystal lattice structure of cathode materials. However, special insights into the mechanisms and effectiveness of the doping strategy, especially comparisons between surface doping and bulk doping in cathode materials, are still lacking. In this review, recent significant progress in surface doping and bulk doping strategies is demonstrated in detail by focusing on their inherent differences as well as effects on the structural stability, lithium-ion (Li-ion) diffusion and electrochemical properties of cathode materials from the following mechanistic insights: preventing the exposure of reactive Ni on the surface, stabilizing the Li slabs, mitigating the migration of transition metal (TM) ions, alleviating undesired structural transformations and adverse interface issues, enlarging the Li interslab spacing, forming three-dimensional (3D) Li-ion diffusion channels, and providing more active sites for the charge-transfer process. Moreover, insights into the correlation between the mechanisms of hybrid surface engineering strategies (doping and coating) and their influences on the electrochemical performance of cathode materials are provided by emphasizing the stabilization of the Li slabs, the enhancement of the surface chemical stability, and the alleviation of TM ion migration. Furthermore, the existing challenges and future perspectives in this promising field are indicated.



Recent Advances in Non-Precious Metal–Nitrogen–Carbon Single-Site Catalysts for CO₂ Electroreduction Reaction to CO

Yiqun Chen, Junru Zhang, Lijun Yang, Xizhang Wang, Qiang Wu, Zheng Hu

2022, 5(4):  11.  doi:10.1007/s41918-022-00156-4

Asbtract ( 1910 )   PDF  

Related Articles | Metrics

The carbon dioxide electroreduction reaction (CO₂RR) to fuels and/or chemicals is an efficient prospective strategy to realize global carbon management using intermittent electric energy harvested from renewable sources. Highly efficient inexpensive electrocatalysts are required to achieve high energy and Faradaic efficiencies as well as fast conversion. Metal–nitrogen–carbon (M–N–C) single-site catalysts (SSCs) are highly competitive over precious metal catalysts in the CO₂RR to CO due to their high performance, easy regulation and low cost. In the past six years, intensive studies of M–N–C SSCs for CO₂RR to CO have been performed, and great progress has been achieved. This review focuses on the important topic of CO₂RR to CO with M–N–C SSCs. We first introduce the reaction mechanism of the CO₂RR to CO and the regulation of the electronic structure from a theoretical viewpoint. Then, the construction of M–N–C SSCs and the regulation of the electronic structure are demonstrated experimentally. The up-to-date electrocatalytic performance of M–N–C SSCs with different metal centers (Ni, Fe, Co and others) is summarized and compared systematically to highlight structure–performance correlations that were considered from both theoretical and experimental perspectives. Finally, the opportunities, challenges and future outlooks are summarized to deepen and widen research and applications in this promising field.



Recent Progress and Design Principles for Rechargeable Lithium Organic Batteries

Xiudong Chen, Xiaojie Yin, Junaid Aslam, Weiwei Sun, Yong Wang

2022, 5(4):  12.  doi:10.1007/s41918-022-00135-9

Asbtract ( 1981 )   PDF  

Related Articles | Metrics

The most commonly used electrode materials in lithium organic batteries (LOBs) are redox-active organic materials, which have the advantages of low cost, environmental safety, and adjustable structures. Although the use of organic materials as electrodes in LOBs has been reported, these materials have not attained the same recognition as inorganic electrode materials, mainly due to their slight electronic conductivity and possible solubility in organic electrolytes, resulting in a low reversible capacity. However, over the past 10 years, organic materials have achieved outstanding results when used as battery electrodes, and an increasing number of researchers have realized their significance. This review summarizes the recent progress in organic electrodes for use in rechargeable LOBs. By classifying Li-storage mechanisms with various functional organic groups and designing molecules for next-generation advanced lithium organic systems, we attempt to analyze the working principle and the effect of various organic functionalities on electrochemical performance, to reveal the advantages and disadvantages of various organic molecules and to propose possible design principles and development trends for future LOBs. In addition, we highlight the recently reported two-dimensional covalent organic framework that is unique in its extensive π conjugated structure and Li-storage mechanisms based on benzene and N-containing rings; this framework is considered to be the most promising alternative to metal-based electrode materials with comparable large reversible capacities and long cycle lives.



Controlled Synthesis of Carbon-Supported Pt-Based Electrocatalysts for Proton Exchange Membrane Fuel Cells

Huiyuan Liu, Jian Zhao, Xianguo Li

2022, 5(4):  13.  doi:10.1007/s41918-022-00173-3

Asbtract ( 1895 )   PDF  

Related Articles | Metrics

Proton exchange membrane fuel cells are playing an increasing role in postpandemic economic recovery and climate action plans. However, their performance, cost, and durability are significantly related to Pt-based electrocatalysts, hampering their large-scale commercial application. Hence, considerable efforts have been devoted to improving the activity and durability of Pt-based electrocatalysts by controlled synthesis in recent years as an effective method for decreasing Pt use, and consequently, the cost. Therefore, this review article focuses on the synthesis processes of carbon-supported Pt-based electrocatalysts, which significantly affect the nanoparticle size, shape, and dispersion on supports and thus the activity and durability of the prepared electrocatalysts. The reviewed processes include (i) the functionalization of a commercial carbon support for enhanced catalyst–support interaction and additional catalytic effects, (ii) the methods for loading Pt-based electrocatalysts onto a carbon support that impact the manufacturing costs of electrocatalysts, (iii) the preparation of spherical and nonspherical Pt-based electrocatalysts (polyhedrons, nanocages, nanoframes, one- and two-dimensional nanostructures), and (iv) the postsynthesis treatments of supported electrocatalysts. The influences of the supports, key experimental parameters, and postsynthesis treatments on Pt-based electrocatalysts are scrutinized in detail. Future research directions are outlined, including (i) the full exploitation of the potential functionalization of commercial carbon supports, (ii) scaled-up one-pot synthesis of carbon-supported Pt-based electrocatalysts, and (iii) simplification of postsynthesis treatments. One-pot synthesis in aqueous instead of organic reaction systems and the minimal use of organic ligands are preferred to simplify the synthesis and postsynthesis treatment processes and to promote the mass production of commercial carbon-supported Pt-based electrocatalysts.



A Review of Nonaqueous Electrolytes, Binders, and Separators for Lithium-Ion Batteries

Jiale Xing, Stoyan Bliznakov, Leonard Bonville, Miodrag Oljaca, Radenka Maric

2022, 5(4):  14.  doi:10.1007/s41918-022-00131-z

Asbtract ( 1952 )   PDF  

Related Articles | Metrics

Lithium-ion batteries (LIBs) are the most important electrochemical energy storage devices due to their high energy density, long cycle life, and low cost. During the past decades, many review papers outlining the advantages of state-of-the-art LIBs have been published, and extensive efforts have been devoted to improving their specific energy density and cycle life performance. These papers are primarily focused on the design and development of various advanced cathode and anode electrode materials, with less attention given to the other important components of the battery. The “nonelectroconductive” components are of equal importance to electrode active materials and can significantly affect the performance of LIBs. They could directly impact the capacity, safety, charging time, and cycle life of batteries and thus affect their commercial application. This review summarizes the recent progress in the development of nonaqueous electrolytes, binders, and separators for LIBs and discusses their impact on the battery performance. In addition, the challenges and perspectives for future development of LIBs are discussed, and new avenues for state-of-the-art LIBs to reach their full potential for a wide range of practical applications are outlined.



Single-Crystal Nickel-Based Cathodes: Fundamentals and Recent Advances

Shijie Lu, Linbo Tang, Hanxin Wei, Yingde Huang, Cheng Yan, Zhenjiang He, Yunjiao Li, Jing Mao, Kehua Dai, Junchao Zheng

2022, 5(4):  15.  doi:10.1007/s41918-022-00166-2

Asbtract ( 219 )   PDF  

Related Articles | Metrics

Lithium-ion batteries (LIBs) represent the most promising choice for meeting the ever-growing demand of society for various electric applications, such as electric transportation, portable electronics, and grid storage. Nickel-rich layered oxides have largely replaced LiCoO₂ in commercial batteries because of their low cost, high energy density, and good reliability. Traditional nickel-based oxide particles, usually called polycrystal materials, are composed of microsized primary particles. However, polycrystal particles tend to suffer from pulverization and severe side reactions along grain boundaries during cycling. These phenomena accelerate cell degradation. Single-crystal materials, which exhibit robust mechanical strength and a high surface area, have great potential to address the challenges that hinder their polycrystal counterparts. A comprehensive understanding of the growing body of research related to single-crystal materials is imperative to improve the performance of cathodes in LIBs. This review highlights origins, recent developments, challenges, and opportunities for single-crystal layered oxide cathodes. The synthesis science behind single-crystal materials and comparative studies between single-crystal and polycrystal materials are discussed in detail. Industrial techniques and facilities are also reviewed in combination with our group’s experiences in single-crystal research. Future development should focus on facile production with strong control of the particle size and distribution, structural defects, and impurities to fully reap the benefits of single-crystal materials.



Recent Advances in the Unconventional Design of Electrochemical Energy Storage and Conversion Devices

Senthil Velan Venkatesan, Arpita Nandy, Kunal Karan, Stephen R. Larter, Venkataraman Thangadurai

2022, 5(4):  16.  doi:10.1007/s41918-022-00162-6

Asbtract ( 231 )   PDF  

Related Articles | Metrics

As the world works to move away from traditional energy sources, effective efficient energy storage devices have become a key factor for success. The emergence of unconventional electrochemical energy storage devices, including hybrid batteries, hybrid redox flow cells and bacterial batteries, is part of the solution. These alternative electrochemical cell configurations provide materials and operating condition flexibility while offering high-energy conversion efficiency and modularity of design-to-design devices. The power of these diverse devices ranges from a few milliwatts to several megawatts. Manufacturing durable electronic and point-of-care devices is possible due to the development of all-solid-state batteries with efficient electrodes for long cycling and high energy density. New batteries made of earth-abundant metal ions are approaching the capacity of lithium-ion batteries. Costs are being reduced with the advent of flow batteries with engineered redox molecules for high energy density and membrane-free power generating electrochemical cells, which utilize liquid dynamics and interfaces (solid, liquid, and gaseous) for electrolyte separation. These batteries support electrode regeneration strategies for chemical and bio-batteries reducing battery energy costs. Other batteries have different benefits, e.g., carbon-neutral Li-CO₂ batteries consume CO₂ and generate power, offering dual-purpose energy storage and carbon sequestration. This work considers the recent technological advances of energy storage devices. Their transition from conventional to unconventional battery designs is examined to identify operational flexibilities, overall energy storage/conversion efficiency and application compatibility. Finally, a list of facilities for large-scale deployment of major electrochemical energy storage routes is provided.



Versatile Electrospinning for Structural Designs and Ionic Conductor Orientation in All-Solid-State Lithium Batteries

Qiang Li, Xiao Sun, Daxian Cao, Ying Wang, Pengcheng Luan, Hongli Zhu

2022, 5(4):  18.  doi:10.1007/s41918-022-00170-6

Asbtract ( 260 )   PDF  

Related Articles | Metrics

Recent advances in next-generation energy storage devices have focused on flexible and wearable all-solid-state lithium batteries (ASSLBs), mainly because of their advantages in terms of safety and extensive applications. Among various technologies for the preparation of flexible electrodes, electrospinning is a straightforward operation and cost-effective mean for the facile fabrication of flexible nanofibers and the versatile design of nanofiber structure. Herein, current technologies for engineering electrospun nanofiber structures and their state-of-the-art implementation in flexible ASSLBs are reviewed. First, current strategies for nanofiber structural design, including advances in high-specific surface area, superior mechanical flexibility, and various nanostructures, are systematically discussed. Subsequently, the utilization of electrospun nanofibers in ASSLBs is reviewed. Electrospinning of flexible and highly ion-conductive solid-state electrolytes (SSEs) is emphasized, and current nanofiber structural designs for SSEs and electrodes for ASSLBs are introduced. Despite these advances, there have not been enough studies of the integration of versatile electrospinning techniques in nanofiber structural design for both SSEs and electrodes. In the final section, promising pathways to implement versatile electrospinning in flexible ASSLBs with superior electrochemical performance and stable cycling properties are discussed. Thus, this review provides a holistic overview of the state of the art of electrospinning for high-performance flexible ASSLBs, which could safely power next-generation flexible devices.