Latest ArticlesSome phase change materials (PCM) suitable for the thermal management of lithium-ion batteries were analyzed based on their types and characteristics, and recent research work on the selection and preparation of the PCMs were described. The main research aspect is to obtain the composites with a high thermal conductivity and a high latent heat. From the perspective of heat transfer mode, research progress on the passive and active phase change material-based thermal management systems was reviewed, and the future development direction was forecasted.
Studies on sodium-ion battery originated from the 1970s and 1980s, but it has not been paid much attention due to its low energy density. With the increasing shortage of lithium resources and the rising cost of lithium-ion battery preparation, sodium ion battery becomes a hot spot in the field of energy storage due to the abundant sodium resources, high energy conversion efficiency, long cycle life and good safety performance. Prussian blue analogues (PBAs) have excellent sodium storage properties due to their unique open framework structure, abundant sodium storage sites and large sodium ion migration channels. However, crystal water and structural defects are easy to occur in the synthesis process, leading to the decline of electrochemical properties. The structure and electrochemical characteristics of PBAs were introduced, and the preparation and modification methods were represented. In addition, the future development of PBAs as acathode for sodium ion battery was also prospected.
Potassium-ion batteries (KIB) are expected to replace lithium-ion batteries (LIB) as a new generation of energy storage devices due to their high energy density and abundant potassium resources. Carbon material is considered as a potential KIB anode material due to its low cost, easy availability and environment friendly. However, the development of carbon materials for KIB is restricted due to the presence of some problems (i.e., huge volume expansion and structural deformation during intercalation/deintercalation process), thus leading to low reversible capacity, inferior rate performance, and poor cycling stability. In order to solve the problems and increase the KIB performance, some approaches were summarized, such as heteroatom doping, structural designing and so on. This review summarized recent research progress on different types of carbon anode materials for KIB, including graphite, graphene, hard carbon, soft carbon and porous carbon. In addition, the critical issues, challenges, and perspectives for the development of KIB were also proposed.
The layered-structure materials of LaSrCoO4±δ and PrBaMn2O5+δ as cathode materials for solid oxide fuel cell were analyzed by the first principle method. Effect of A site atom arrangement (i.e., layered and mixed) on the electronic structure, defect forming energy and oxide ion migrating energy was investigated. The results show that for LaSrCoO4±δ, La/Sr atoms layered arrangement favors the formation and migration of interstitial oxygen ions, and for PrBaMn2O5+δ, Pr/Ba mixing arrangement benefits the formation and migration of oxygen vacancy. The electronic density distribution in real space was calculated. The results also indicate the reason for different oxygen defects (interstitial ions or vacancy) forming and migrating in each structure and provide a specific micro-image for the material research and optimization.
Micro thermoelectric devices based on thermoelectric films have promising applications in various fields such as micro-zone refrigeration and power generation. Thermoelectric films with high power factor and large ZT values are critical materials in these devices. Sb2Te3-based materials are outstanding p-type thermoelectric materials at room temperature. However, the thermoelectric properties of Sb2Te3-based thin films cannot meet the requirement of practical applications. The research background of thermoelectric materials is briefly introduced, the crystal structure of Sb2Te3 is discussed, the preparation techniques of Sb2Te3-based thin films are outlined, and the methods of improving the power factor and reducing the thermal conductivity of Sb2Te3-based thin films are summarized. In particular, the effects of microstructure on thermoelectric properties are focused on to elucidate the mechanism of improving thermoelectric properties of the films, which includes defects, preferential orientation, nanoparticles, superlattice, organic-inorganic hybridization, and so on. In addition, the future research directions for Sb2Te3-based thermoelectric thin films are discussed.
Hierarchical porous carbon with massive pores and intersections has a great potential in microwave absorption due to the low density, high specific surface area and high dielectric properties. This review represented the source, structure, composition and characteristics of hierarchical porous carbon materials. The research progress on hierarchical porous carbon as a wave absorbing material was summarized, and its future development was prospected.
FeCo@nano-SiO2 was prepared via a modified Stöber method using tetraethyl orthosilicate using FeCo as raw materials. The results show that the powder has a uniform core-shell structure. The reflection loss (RL) of FeCo@nano-SiO2 reaches -36.1 dB with the thickness of 2.6 mm, and the effective absorption bandwidth with RL<-10 dB is 3.2 GHz when the content of SiO2 is 35% (in mass fraction). The mass of FeCo@nano-SiO2 only increases 2% from room temperature to 800℃, and the optimum oxidation resistance can be obtained at the content of SiO2 of 65%. The SiO2 shell optimizes the impedance matching of FeCo, further facilitating the electromagnetic wave absorption, and prevents the contact between FeCo and oxygen at a high temperature, thus improving the oxidation resistance.
A flexible, lightweight and efficient electromagnetic shielding material was prepared with activated carbon fiber felt (ACF) with the density of 0.055 g/cm3. The phase compositions and micro-morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively. The electromagnetic parameters of samples at 8.2-12.4 GHz were examined by a rectangular waveguide method. The results show that high-temperature treatment can improve the degree of carbon ordering in ACF. The conductivity and electromagnetic shielding efficiency of ACF are improved after high-temperature treatment. The total electromagnetic shielding effectiveness of ACF is 39 dB after high-temperature treatment at 1 400℃, which is 23 dB greater than that of the raw material of ACF (i.e., 16 dB). It is indicated that high-temperature treatment could improve the electromagnetic shielding performance of ACF.
Metal V films were prepared on quartz substrates via magnetron sputtering, and then converted to VO2 films via vacuum annealing. The effect of annealing temperature on the surface morphologies, crystalline structures, optical properties and electric properties of VO2 films was investigated. The results show that the crystallinity of the films increases with the increase of annealing temperature from 300℃ to 450℃. The films annealed at 400℃ and 450℃ are a pure monoclinic phase. The grains grow better and the grain boundaries are clear. The valent states of V element for different samples include +4 and +5 states. The presence of V5+ in the films is due to the oxidation in atmosphere. The annealing temperature has little effect on the visible transmittance, but the solar modulation efficiency increases. The metal-insulator transition (MIT) temperature and the resistance of semiconductor phase increase with increasing the annealing temperature. The resistance change amplitude across the MIT for the films annealed at 400℃ and 450℃ is more than 2 orders of magnitude. The hysteresis width and the MIT temperature of the film annealed at 450℃ are 14.6℃ and 61.0℃, respectively.
This review represented the electrochromic mechanism of Prussian blue (PB), and summarized recent research work on the improvement of the electrochromic performance of PB. The main methods of preparing PB thin films and the relationship between the process and the properties were described. The mechanism of improving the properties of electrochromic devices by combining PB with other materials was emphatically given. It is indicated that increasing the contact area with the ion layer and improving the conductivity of the base both are effective approaches to improve the electrochromic devices of PB. In addition, the future development of PB electrochromic devices is integrated with flexible materials to expand the application range of electrochromic devices besides the improvement of the optical and electrical performance.
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