A Bilayer High-Temperature Dielectric Film with Superior Breakdown Strength and Energy Storage Density

The further electrification of various fields in production and daily life makes it a topic worthy of exploration to improve the performance of capacitors for a long time,including thin-film capacitors.The discharge energy density of thin-film capacitors that serves as one of the important types directly depends on electric field strength and the dielectric constant of the insulation material.However,it has long been a great challenge to improve the breakdown strength and dielectric constant simultaneously.Considering that boron nitride nanosheets(BNNS)possess superior insulation and thermal conductivity owing to wide band gap and 2-dimensional structure,a bilayer polymer film is prepared via coating BNNS by solution casting on surface of polyethylene terephthalate(PET)films.By revealing the bandgap and insulating behavior with UV absorption spectrum,leakage current,and finite element calculation,it is manifested that nanocoating contributes to enhance the bandgap of polymer films,thereby suppressing the charge injection by redirecting their transport from electrodes.Worthy to note that an ultrahigh breakdown field strength(~736 MV m^(−1)),an excellent discharge energy density(~8.77 J cm^(−3))and a prominent charge-discharge efficiency(~96.51%)are achieved concurrently,which is ascribed to the contribution of BNNS ultrathin layer.In addition,the modified PET films also have superior comprehensive performance at high temperatures(~120°C).The materials and methods here selected are easily accessible and facile,which are suitable for large-scale roll-to-roll process production,and are of certain significance to explore the methods about film modification suitable for commercial promotion.

Storage Characteristics of LiNi_(0.8)Co_(0.1+X)Mn_(0.1-X)O_2 (X=0,0.03,0.06) Cathode Materials for Lithium Batteries

1 Results LiNi0.8Co0.1+xMn0.1-xO2 cathodes with x=0,0.03 and 0.06 were prepared by firing a mixture of stoichiometric amounts of LiOH·H2O and coprecipitated Ni0.8Co0.1+xMn0.1-x(OH)2 at 800 ℃ for 15 h.Using these powders,their storage characteristics upon exposure to air and electrolytes at 90 ℃ were compared before charging and after charging to 4.3 V with a variation of the storage time.As the Co content (x) increased in the cathode,both the Ni2+ content in the lithium 3a sites,and the contents of the ...

Indication of hydrogen and oxygen stable isotopes on the characteristics and circulation patterns of medium-low temperature geothermal resources in the Guanzhong Basin,China

Guanzhong Basin is a typical medium-low temperature geothermal field mainly controlled by geo-pressure in the west of China.The characteristics of hydrogen and oxygen isotopes were used to analyze the flow and storage modes of geothermal resources in the basin.In this paper,the basin was divided into six geotectonic units,where a total of 121 samples were collected from geothermal wells and surface water bodies for the analysis of hydrogen-oxygen isotopes.Analytical results show that the isotopic signatures of hydrogen and oxygen throughout Guanzhong Basin reveal a trend of gradual increase from the basin edge areas to the basin center.In terms of recharge systems,the area in the south edge belongs to the geothermal system of Qinling Mountain piedmont,while to the north of Weihe fault is the geothermal system of North mountain piedmont,where the atmospheric temperature is about 0.2℃-1.8℃in the recharge areas.The main factors that affect the geothermal waterδ18O drifting include the depth of geothermal reservoir and temperature of geothermal reservoir,lithological characteristics,water-rock interaction,geothermal reservoir environment and residence time.Theδ18O-δD relation shows that the main source is the meteoric water,together with some sedimentary water,but there are no deep magmatic water and mantle water which recharge the geothermal water in the basin.Through examining the distribution pattern of hydrogen-oxygen isotopic signatures,the groundwater circulation model of this basin can be divided into open circulation type,semi-open type,closed type and sedimentary type.This provides some important information for rational exploitation of the geothermal resources.

Plant species with extremely small populations(PSESP) in China:A seed and spore biology perspective

Approximately one fifth of the world's plants are at risk of extinction.Of these,a significant number exist as populations of few individuals,with limited distribution ranges and under enormous pressure due to habitat destruction.In China,these most-at-risk species are described as 'plant species with extremely small populations'(PSESP).Implementing conservation action for such listed species is urgent.Storing seeds is one of the main means of ex situ conservation for flowering plants.Spore storage could provide a simple and economical method for fern ex situ conservation.Seed and spore germination in nature is a critical step in species regeneration and thus in situ conservation.But what is known about the seed and spore biology(storage and germination) of at-risk species? We have used China's PSESP(the first group listing) as a case study to understand the gaps in knowledge on propagule biology of threatened plant species.We found that whilst germination information is available for 28 species(23%of PSESP),storage characteristics are only known for 8%of PSESP(10 species).Moreover,we estimate that 60%of the listed species may require cryopreservation for long-term storage.We conclude that comparative biology studies are urgently needed on the world's most threatened taxa so that conservation action can progress beyond species listing.

High-temperature energy storage dielectric with inhibition of carrier injection/migration based on band structure regulation

Dielectric capacitors have a high power density,and are widely used in military and civilian life.The main problem lies in the serious deterioration of dielectric insulation performance at high temperatures.In this study,a polycarbonate(PC)-based energy storage dielectric was designed with BN/SiO_(2)heterojunctions on its surface.Based on this structural design,a synergistic suppression of the carrier injection and transport was achieved,significantly improving the insulating properties of the polymer film.In particular,the composite film achieves optimal high-temperature energy-storage properties.The composite film can withstand an electric field intensity of 760 MV m^(-1)at 100℃and obtain an energy storage density of 8.32 J cm^(-3),while achieving a breakthrough energy storage performance even at 150℃(610 MV m^(-1),5.22 J cm^(-3)).Through adjustment of the heterojunction structure,free adjustment of the insulation performance of the material can be realized;this is of great significance for the optimization of the material properties.