目录 | 《电化学（中英文）》2024年第6、7期（电化学获奖人专辑）文章速览

Developing in situ spectroelectrochemistry methods, which can provide detailed information about species transformation during electrochemical reactions, is very important for studying electrode reaction mechanisms and improving battery performance. Studying real-time changes in the surface of electrode materials during normal operation can be an effective way to assess and optimize the practical performance of electrode materials, thus, in situ and in operando characterization techniques are particularly important. However, batteries are hard to be studied by in situ characterization measurements due to their hermetically sealed shells, and there is still much room for battery characterizations. In this work, a specially designed battery based on the structure of coin cells, whose upper cover was transparent, was constructed. With such a device, acquisition of diffuse reflectance spectra of electrode materials during charging and discharging was realized. This not only provided a simple measurement accessory for diffuse reflectance spectroscopy (DRS), but also complemented in situ characterization techniques for batteries. Taking commonly used cathode materials in lithium-ion batteries (LIBs), including LiFePO4 (LFP), NCM811 and LiCoO2 (LCO) as examples, we managed to find out the response relationships of different electrode materials to visible light of different wavelengths under ordinary reflectance illumination conditions. Heterogeneity of different cathode materials on interaction relationships with the lights of different wavelengths was also revealed. This work demonstrated the capability of guiding wavelength selection for different materials and assessing electrochemical performances of in situ diffuse reflectance spectroelectrochemistry. By combining electrochemistry with diffuse reflectance spectroscopy, this work made an effective complementary for spectroelectrochemistry.

Two major challenges, high cost and short lifespan, have been hindering the commercialization process of low-temperature fuel cells. Professor Wei’s group has been focusing on decreasing cathode Pt loadings without losses of activity and durability, and their research advances in this area over the past three decades are briefly reviewed herein. Regarding the Pt-based catalysts and the low Pt usage, they have firstly tried to clarify the degradation mechanism of Pt/C catalysts, and then demonstrated that the activity and stability could be improved by three strategies: regulating the nanostructures of the active sites, enhancing the effects of support materials, and optimizing structures of the three-phase boundary. For Pt-free catalysts, especially carbon-based ones, several strategies that they proposed to enhance the activity of nitrogen-/heteroatom-doped carbon catalysts are firstly presented. Then, an in-depth understanding of the degradation mechanism for carbon-based catalysts is discussed, and followed by the corresponding stability enhancement strategies. Also, the carbon-based electrode at the micrometer-scale, faces the challenges such as low active-site density, thick catalytic layer, and the effect of hydrogen peroxide, which require rational structure design for the integral cathodic electrode. This review finally gives a brief conclusion and outlook about the low cost and long lifespan of cathodic oxygen reduction catalysts.

The unstable zinc (Zn)/electrolyte interfaces formed by undesired dendrites and parasitic side reactions greatly hinder the development of aqueous zinc ion batteries. Herein, the hydroxy-rich sorbitol was used as an additive to reshape the solvation structure and modulate the interface chemistry. The strong interactions among sorbitol and both water molecules and Zn electrode can reduce the free water activity, optimize the solvation shell of water and Zn²⁺ ions, and regulate the formation of local water (H2O)-poor environment on the surface of Zn electrode, which effectively inhibit the decomposition of water molecules, and thus, achieve the thermodynamically stable and highly reversible Zn electrochemistry. As a result, the assembled Zn/Zn symmetric cells with the sorbitol additive realized an excellent cycling life of 2000 h at 1 mA·cm^-2 and 1 mAh·cm^-2, and over 250 h at 5 mA·cm^-2 and 5 mAh·cm^-2. Moreover, the Zn/Cu asymmetric cells with the sorbitol additive achieved a high Coulombic efficiency of 99.6%, obtaining a better performance than that with a pure 2 mol·L^-1 ZnSO4 electrolyte. And the constructed Zn/poly1, 5-naphthalenediamine (PNDA) batteries could be stably discharged for 2300 cycles at 1 A·g^-1 with an excellent capacity retention rate. This result indicates that the addition of 1 mol·L^-1 non-toxic sorbitol into a conventional ZnSO4 electrolyte can successfully protect the Zn anode interface by improving the electrochemical properties of Zn reversible deposition/decomposition, which greatly promotes its cycle performance, providing a new approach in future development of high performance aqueous Zn ion batteries.

Magnesium (Mg) is a promising alternative to lithium (Li) as an anode material in solid-state batteries due to its abundance and high theoretical volumetric capacity. However, the sluggish Mg-ion conduction in the lattice of solid-state electrolytes (SSEs) is one of the key challenges that hamper the development of Mg-ion solid-state batteries. Though various Mg-ion SSEs have been reported in recent years, key insights are hard to be derived from a single literature report. Besides, the structure-performance relationships of Mg-ion SSEs need to be further unraveled to provide a more precise design guideline for SSEs. In this Viewpoint article, we analyze the structural characteristics of the Mg-based SSEs with high ionic conductivity reported in the last four decades based upon data mining - we provide big-data-derived insights into the challenges and opportunities in developing next-generation Mg-ion SSEs.

The ocean accounts for 97% of the total water resources on earth, covering over 70% of the map's surface area. With the continuous consumption of non-renewable energy sources such as fossil fuels and the rapid development of renewable energy, humans are increasingly paying attention to the utilization of ocean resources. Ocean energy includes tidal energy, wave energy, temperature difference energy, and salinity gradient energy. Salinity gradient energy is the energy generated by the interaction of seawater and fresh water, which is the ocean energy existing in the form of chemical energy. This energy is mostly generated in estuaries. The osmotic pressure generated by mixing water with different salinity can be converted into electrical energy driven by potential differences or ion gradients. Salinity gradient energy, as a new renewable energy source, has received widespread global attention and research in recent years, making rapid progress. The utilization of salinity gradient energy provides a renewable and sustainable alternative to the recent surge in global energy consumption.

At present, pressure delay osmosis technology, reverse electrodialysis technology and capacitive mixing technology are three main technologies for extracting salinity gradient energy. In this work, we built a new type of salt difference cell based on capacitive mixing technology, using molybdenum disulfide (MoS2) and multiwalled carbon nanotubes (MoS2/MWCNTs) composite electrode as the anode and an activated carbon (AC) as the cathode.

We composited two materials with different ion storage mechanisms together. MoS2 has a layered structure like graphene, with an interlayer spacing of about twice that of graphene. It is a battery electrode material that can undergo intercalation reaction with Na⁺. MWCNTs have a typical double electric layer effect. When discharging, while adsorbing Na⁺ on its surface, it can help Na⁺ enter the interlayer of MoS2 more quickly, accelerating the ion transport efficiency and the extraction efficiency of salt differential energy. We conducted physical and electrochemical characterizations of MoS2/MWCNTs composite material, and tested its salt difference energy extraction ability on a salt difference battery composed of it and AC electrode. We found that the concentration response voltage reached 150 mV, and the energy density of the extracted salt difference energy after a complete four-step cycle reached up to 6.96 J·g^-1. The advantages of low raw material price of the device and without using ion membranes make it more environmentally friendly, providing a new approach for the study of extracting salinity gradient energy.