Abstract: Energy electrochemistry is one of the key branches of energy chemistry. Its main goal is to develop chemical energy storage devices with high performance, high safety, long life and low cost for wide applications. The key research areas include lithium ion batteries, fuel cells and redox flow batteries, and the key future directions include Li-S batteries, Li-air batteries, all solid-state batteries and batteries for wearable electronics. Recently there have been some significant advances spanning from fundamental discovery to application-specific prototypes in this field. For this reason, J. Energy Chem. organizes this special issue titled "Energy Electrochemistry" to show the recent development and challenges in this field.
This issue contains 16 contributions, with 1 communication, 8 reviews and 7 articles, covering different aspects in fuel cells, ion batteries, lithiumsulfur batteries and etc.
In the communication, Zhuang, Xiao and coworkers (https://doi.org/10.1016/j.jechem.2018.05.009) report a simple method to prepare wide channels bearing hydrocarbon proton exchange membranes with about the 200% improved conductivity for proton exchange membrane fuel cells (PEMFCs). Electrocatalysts are another key component to play vital role in the fuel cells. Liu, Xing and coworkers (https://doi.org/10.1016/j.jechem.2018.01.029) review the recent development of methanol electro-oxidation catalysts for direct methanol fuel cells (DMFCs), which is a promising power source for stationary and portable miniature electric appliances. Xie, Zhang and coworkers (https://doi.org/10.1016/j.jechem.2018.03.015) summarize the recent advances in electrocatalytic conversion of methane to ethylene and methanol. Xing and coworkers (https://doi.org/10.1016/j.jechem.2018.06.008) developed a series of Fe-N-C catalysts from various iron sources, for example ZIF-8, (Fe(acac)₃ and discussed the influence of the Fe morphology and site density on the ORR activity.
The lithium-ion batteries featuring relatively high energy density have long been used to power portable electronics and electrical vehicles. Aqueous lithium-ion battery (ALIB) is one of the most promising stationary power sources for sustainable energy such as wind and solar power. Xia and coworkers (https://doi.org/10.1016/j.jechem.2018.06.004) review the development of cathode, anode and electrolyte for acquiring the desired electrochemical performance of ALIBs. Moreover, electrode materials determine the battery performance. Zhao et al. (https://doi.org/10.1016/j.jechem.2018.01.009) review the recent development of using transition metal sulfides such as copper sulfides, molybdenum sulfides, cobalt sulfides, and iron sulfides as electrode materials for lithium ion batteries. Sun et al. (https://doi.org/10.1016/j.jechem.2018.04.009) report the excellent performance of lithium-ion battery with porous core-shell CoMn₂O₄ microspheres as anode and their conversion reaction mechanism. Chen et al. (https://doi.org/10.1016/j.jechem.2018.06.003) report core-shell structured 1,4-benzoquinone@titanium dioxide (BQ@TiO₂) composite as cathode for lithium batteries, which exhibit high discharge capacity and good cycling performance. Xia and coworkers (https://doi.org/10.1016/j.jechem.2018.01.026) determine the theoretical specific capacity of a new two-dimensional boron material as anode material for lithium-ion batteries using the first principles calculations.
In situ and operando techniques with high spatial and temporal resolution have been developing rapidly for the nondestructive and real time dynamic investigation on the electrochemical reaction mechanism. Yang et al. (https://doi.org/10.1016/j.jechem.2018.03.020) review the application of synchrotron X-ray techniques, including X-ray diffraction (XRD), Pair Distribution Function (PDF), Hard and Soft X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS), to the investigation of battery systems. He, Zhou and coworkers (https://doi.org/10.1016/j.jechem.2018.06.007) investigated the lithium storage mechanism of layered LiNi_0.8Co_0.15Al_0.05O₂ during the electrochemical process through in situ X-ray diffraction.
Lithium-sulfur (LiS) battery is considered to be a promising next generation energy storage device with very high theoretical energy density and the natural abundance of sulfur. Guo et al. (https://doi.org/10.1016/j.jechem.2018.04.014) review the physical and chemical confinement of LiPSs and emphasize that synergy of the physical and chemical confinement is the feasible avenue to guide LiS batteries to the practical application. Chen, Wei and coworkers (https://doi.org/10.1016/j.jechem.2018.02.010) report a novel hierarchically porous nitrogen-doped carbon (HPNC) via a combination of salt template (ZnCl₂) and hard template (SiO₂) as sulfur host for Li-S batteries.
Comparing with lithium, sodium is of high overall abundance with even geographical distribution, and low cost. Thus, sodium-ion batteries (SIBs) have attracted increasing attention in the past decades. Zheng, Zhang and coworkers (https://doi.org/10.1016/j.jechem.2018.05.001) review the crystal structure of Na₃V₂(PO₄)₃ (NVP), a typical sodium super ion conductor (NASICON)-based electrode material, and recent approaches to enhance their surface electrical conductivity and intrinsic electrical conductivity. Besides, for the higher energy density Na-based batteries, Lu, Hu and coworkers (https://doi.org/10.1016/j.jechem.2018.03.004) discuss the challenges of Na metal anode, and then summarize several strategies to suppress dendrite growth and improve electrochemical performance, including interface engineering, electrolyte composition, electrode construction, and so on.
The last but not least system is lead-carbon battery (LCB) that is the new generation of lead-acid batteries. It is well known for its superior performance in partial-state-of-charge operation. Lin et al. (https://doi.org/10.1016/j.jechem.2018.03.002) report the novel lead-carbon anode with C/Pb composite, which displays excellent chargedischarge reversibility.
In summary, these outstanding contributions present the cutting-edge research and excellent collection of the field of energy electrochemistry. We would like to sincerely thank the authors for their great efforts in preparing high-quality manuscripts and the expert reviewers for providing constructive comments and helpful suggestions, which contributed substantially to the high scientific level of this issue. We also thank the efficient and professional editorial office of J. Energy Chem. for their tremendous efforts to make this issue such a great success.