Solid polymer electrolytes (SPEs) with high flexibility and processability enable the fabrication of leak-free solid-state batteries with varied geometries. However, SPEs usually suffer from low ionic conductivity and poor stability with lithium metal anodes. Here, we propose nano-sized metal-organic framework (MOF) material(UiO-66) as filler for poly(ethylene oxide) (PEO) polymer electrolyte. The coordination of UiO-66 with oxygen in PEO chain and the interaction between UiO-66 and lithium salt significantly improve the ionic conductivity (3.0×10 ^-5 S/cm at 25 ℃, 5.8×10 ^-4 S/cm at 60 ℃) and transference number of Li ⁺ (0.36), widen the electrochemical window to 4.9 V (vs Li ⁺/Li), enhance the stability with lithium metal anode. As a result, the as-prepared Li symmetrical cells can continuously operate for 1000 h at 0.15 mA?cm ^-2, 60 ℃. The results show that UiO-66 filler is effective to improve the electrochemical performance of polymer electrolyte.

High-entropy oxides have attracted more and more attention due to their unique structures and potential applications. In this work, M₃O₄(M=FeCoCrMnMg) high entropy oxide powders were synthesized by a facile solid-state reaction method. The powders were characterized by different methods. Furthermore, M₃O₄/Ni foam (M₃O₄/NF) electrode was prepared by a coating method, followed by investigation of its supercapacitor performance. The results showed that, with the increase of calcining temperature, Fe₂O₃(H)/Co₃O₄(S)/Cr₂O₃(E) and Mn₂O₃(B) dissolved successively in the crystal lattice of spinel structure. After M₃O₄ powders being calcined at 900 ℃ for 2 h, single spinel structure (FCC, Fd-3m, a=0.8376 nm) was obtained with uniform distribution of Fe, Co, Cr, Mn, and Mg elements, the typical characteristic of high entropy oxide. In addition, the mass specific capacitance of M₃O₄/NF composite electrode is 193.7 F·g^-1, with 1 mol/L KOH as electrolyte and 1 A·g^-1 as current density, which indicated that the M₃O₄ high entropy oxide can be considered as a promising candidate for the electrode material in the field of supercapacitor applications.

With the advantages of low cost and wide distribution of raw materials, sodium-ion batteries are considered to be the best alternative materials for lithium-ion battery cathode materials. In the P2-phase NaMnO₂ with layered structure, binary solid solution of the transition metal layer can effectively improve the electrochemical performance of the electrode material. In this study, the structural model of Na_x[Mg_0.33Mn_0.67]O₂ with Mg ion solid solution was constructed by using the Coulombic model. The first-principles calculations revealed that discharge voltage of Na_x[Mg_0.33Mn_0.67]O₂ reached 3.0 V at a sodium ion content of less than 0.67. Electronic density of states and charge population analysis showed that the solid solution of Mg motivated the anionic electrochemical activity of lattice oxygen in the P2-phase Na_x[Mg_0.33Mn_0.67]O₂, which transformed the electrochemical reaction mechanism of the system from cationic and anionic synergic redox reaction to reversible anionic redox reaction. This transformation provides a novel method for the design of electrode materials for Na ion batteries, as well as a new approach for the optimization and exploration of other ion batteries.

High entropy La(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O₃ perovskite ceramics powder were prepared using coprecipitation method combined with calcination process, and synthesis temperature of the high entropy perovskite ceramics was significantly reduced. The phases and morphology of the ceramics powder were characterized by different methods. The results show that when the calcination temperature is 800 ℃, perovskite structure with a small amount of second phase was formed in the ceramics powder. When the calcination temperature is 1000 ℃, pure perovskite structure is formed in the La(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O₃ high entropy ceramics powder. Three electrode system was used to test the electrical properties of the working electrode made from the La(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O₃ high entropy ceramics powder, including cyclic voltammetry (CV) test and constant current charge-discharge (GCD) test. At the current density of 1 A/g, specific capacity of the working electrode reaches 154.8 F/g, while the current density increased to 10 A/g, the electrode material can still maintain 47%(73 F/g) of the initial specific capacity. All results indicate that high entropy La(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O₃ perovskite ceramics have good rate properties.

Lithium-sulfur batteries are deemed to be the next generation of cost-effective and high energy density systems for energy storage. However, low conductivity of active materials, shuttle effect and sluggish kinetics of redox reaction lead to serious capacity fading and poor rate performance. Herein, a sodium citrate derived three-dimensional hollow carbon framework embedded with cobalt nanoparticles is designed as the host for sulfur cathode. The introduced cobalt nanoparticles can effectively adsorb the polysulfides, enhance the kinetics of conversion reaction and further improve the cyclic and rate performance. The obtained cathode delivered a high initial discharge capacity of 1280 mAh·g^-1 at 0.5C, excellent high-rate performance up to 10C and stable cyclic capacity of 770 mAh·g^-1 at 1C for 200 cycles with high Columbic efficiency.

Storage life at high state of charge is a key factor affecting the application of Li ion battery, but the related mechanism research is insufficient. In this study, the storage life of LiNi_0.8Co_0.15Al_0.05O₂ (NCA)/graphite battery was evaluated via accelerating experiment at elevated temperature, and the electrochemistry performances and interface properties of fresh and aged active materials were analyzed. Storage experiment shows that the storage life of NCA/graphite battery at high state of charge under 55 ℃ is about 90 d. Electrochemical test shows that the capacities of NCA and graphite decrease when the batteries reach the end of life, but that is not the main cause inducing capacity degradation. Interface analysis illustrates that the solid electrolyte interface (SEI) film on graphite anode significantly grows when batteries reach the end of life, while the positive solid electrolyte interface (PEI) film on NCA cathode keeps basically unchanged. The growth of SEI film on graphite owing to the decomposition of carbonates in electrolyte results in Li loss in anode, which contributes to the capacity loss of NCA/graphite battery during the storage aging at high state of charge.

As the extension of high-entropy alloy, entropy engineering has been already extensively used in thermoelectrics because it can guide the optimization of thermoelectric (TE) performance from the aspects of both electrical and thermal transports. Due to the inherent material gene-like feature, entropy can be used as a performance indicator to rapidly screen new multicomponent TE materials. In this review, we first reveal the reason why entropy can be used as the performance indicator of TE materials. The physical mechanisms of enhanced structure symmetry, improved Seebeck coefficient, and suppressed lattice thermal conductivity as a result of the increased configurational entropy are discussed. Then, the applications of entropy engineering in typical TE materials, such as liquid-like materials and IV-VI semiconductors, are outlined, and the approach to screen and identify candidate multicomponent TE materials with high configurational entropy is introduced. Finally, the future directions for entropy engineering are highlighted.

In general, (GeTe)_n(Bi₂Te₃)_m compounds in GeTe-Bi₂Te₃ pseudo-binary system possess a relatively low thermal conductivity, however, the thermoelectric properties of these compounds have not been evaluated systematically. In this study, a series of single-phase (GeTe)_nBi₂Te₃ (n=10, 11, 12, 13, 14) compounds were prepared by a melting-quenching-annealing process combined with spark plasma sintering. The phase compositions and thermoelectrical properties of these samples were characterized. It is found that doping with Bi₂Te₃ intensifies the phonon scattering and significantly reduces the lattice thermal conductivities of these samples, producing a low total thermal conductivity of 1.63 W?m ^-1?K ^-1 at 723 K for (GeTe)₁₃Bi₂Te₃ compound. Moreover, the effective mass of these compounds is enhanced through adjustment of the relative amount of Bi₂Te₃ and GeTe. Therefore, the Seebeck coefficient and power factor of these samples remain superior even at high carrier concentration. At 723 K, the maximum power factor of (GeTe)₁₃Bi₂Te₃ compound is 2.88×10 ^-3 W?m ^-1?K ^-2 and the maximum ZT of (GeTe)₁₃Bi₂Te₃ is 1.27, which is 16% higher than that of pristine GeTe.

With the fascinating properties observed in high entropy alloys, the idea of high entropy design has been applied to many material fields. Thermoelectric materials have some particular requirements for high entropy structure according to their transport characteristics. Here, we revealed that the high entropy structure for thermoelectrics required less lattice distortion, and the doping sites should have less influence on the Fermi surface. In the designed compound of Cu_0.8Ag_0.2Zn_0.1Ga_0.4Ge_0.1In_0.4Te₂, the room-temperature thermal conductivity is reduced by 80% as compared to the matrix, and the maximum ZT is enhanced to 1.02. In SnTe, the solid solution of AgSbSe₂ reduces the room-temperature thermal conductivity by 80%, reaching 1.3 W·m^-1·K^-1. This study shows that the high entropy structure following the proposed designing rules could be an important strategy for thermoelectrics.

The high temperature interfacial stability of thermoelectric (TE) elements, which is mainly evaluated by the inter-diffusion and interfacial resistivity at the interface between the barrier layer and the TE material, is one of the key factors determining the service performance and application prospects of TE devices. In this study, a screening method based on high-throughput strategy was employed to further improve the interfacial stability of P-type bismuth telluride TE devices, and Fe was proved the preferred barrier layer material for P-type Bi_0.5Sb_1.5Te₃ (P-BT). Then Fe/P-BT TE elements were prepared by one-step sintering. Evolution of the Fe/P-BT interfacial microstructure during high temperature accelerated aging was systematically studied, and stability of the interfacial resistivity was explored. It is found that during aging, the Fe/P-BT interface is well bonded and the composition of the ternary Fe-Sb-Te diffusion layer remains basically unchanged. The diffusion layer thickness increases linearly with the square root of the aging time and the growth activation energy is 199.6 kJ/mol. The initially low interfacial resistivity of the Fe/P-BT interface increases slowly with the prolonged aging time but remains below 10 μΩ·cm² even after 16 d at 350 ℃. The life prediction based on the interfacial diffusion kinetics indicates that Fe is a suitable barrier layer material for Bi_0.5Sb_1.5Te₃ TE elements.

Hydrolysis is a unique method for hydrogen generation at ambient condition. Widespread attentions have been paid to materials for hydrogen generation via hydrolysis due to several advantages: high theoretical hydrogen capacity, moderate storage and operation condition, safety, etc. In this paper, recent progress and development in this area were reviewed. Three types of materials including borohydride (NaBH₄, NH₃·BH₃), metal (Mg, Al), and metal hydride (MgH₂) were introduced. Several issues about them were discussed specifically: mechanism, main problems, designments of catalysts and materials, etc. Based on these discussions, we compared the different materials mentioned above, commented their current performances and practical difficulties. At last, prospects in this field were presented.

The amorphous nano-Nd-Ni-B rare earth (RE) alloy catalytic electrode on nickel foam (NF) was prepared by simple one-step electroless deposition method and served as a highly active hydrogen evolution reaction (HER) catalyst. Its microstructure and electrocatalytic HER performance were characterized. The results show that addition of Nd improved the electrocatalytic HER. The preparation conditions were optimized with neodymium nitrate of 3 g?L^-1, reaction temperature of 35 ℃ and reaction time of 1 h. The Nd-Ni-B/NF electrode requires an overpotential of only 180 mV to achieve the current density of 20 mA?cm^-2 in 1.0 mol?L^-1 KOH solution, and the corresponding Tafel slope is 117 mV?dec^-1. HER of Nd-Ni-B/NF catalyst is controlled by Volmer-Heyrovsky step. Moreover, the Nd-Ni-B/Nf shows superior electrochemical stability, 12 h chronoamperometry and 2000 sweeps of cyclic voltammetry with no obvious activity decay.

In recent years, perovskite materials become a research hotspot in the field of solar cells due to their excellent photovoltaic properties, but control of their interface defects still remains one of the key problems to be solved. In this study, an organic small molecule additive (L-3-(4-pyridyl)-alanine (PLA)) was introduced in the preparation of perovskite photoabsorption layer by two-step solution method. The characterizations showed that the introduction of PLA could comprehensively improve photoelectric performance of the device, with optimal energy conversion efficiency of 21.53%, in contrast to that of the reference device (20.10%). Further studies showed that PLA could reduce the trap state density of the device from 5.59×10¹⁶cm^-3 to 3.40×10¹⁶cm^-3, promote the interface charge extraction, and decrease the carrier recombination. The above improvements can be attributed to the PLA induced PbI₂ enrichment at grain boundaries and PLA anchoring at defects, which play an important roles in passivate defects. This study can provide guideline for further regulating the defects of perovskite solar cells.

Oxygen vacancy plays an important role in promoting CO₂ adsorption and reduction on photocatalysts. Bi was heavily doped into ceria, forming a solid solution catalyst Ce_1-xBi_xO_2-δ meanwhile maintaining the fluorite structure, to increase the oxygen vacancy concentration. The sample Ce_0.6Bi_0.4O_2-δ showed the highest photocatalytic activity with a CO yield of ～4.6 times that of the pristine ceria nanorods. Bi was homogeneously dispersed into the fluorite ceria which was confirmed by XRD and EDX elemental mapping. It has been evidenced by the results of Raman and XPS that Bi introduction boosts the concentration of oxygen vacancy in the solid solution that can facilitate the adsorption/activation of carbonate and bicarbonate intermediates on its surface according to in-situ FT-IR.

Electron transport layer is a key part for perovskite solar cell (PSC), which can block holes and transmit electrons to reduce recombination. In this study, SnO₂ was synthesized with low-temperature solution-processed method and used as electronic transport layer for perovskite solar cells. The influence of annealing temperature on the properties of SnO₂ films and PSCs were systematically studied. The results showed that with the annealing temperatures at 60, 90, 120, 240 ℃, the surfaces of SnO₂ films own more pores; while annealed at 150, 180, 210 ℃, the corresponding surfaces show fewer pores. It was found that the transmittance of FTO glass covered with SnO₂ films is better than that of the bare FTO glass. With SnO₂ annealed at 180 ℃, the electron mobility of the thin film is the highest. The corresponding PSC possesses the best transmission resistance, composite resistance, and superior photovoltaic performance. The photoelectric conversion efficiency, the open-circuit voltage, the short-circuit current and the filling factor were 17.28%, 1.09 V, 20.91 mA/cm² and 75.91%, respectively.

In the production process of multicrystalline silicon solar cells, diamond wire sawn (DWS) cutting technology attracts wide attention because of its advantages of high cutting speed, high precision and less loss of raw materials. But the traditional acid etching technology cannot match the shallow damage layer formed on the surface of diamond wire sawn cut multicrystalline silicon wafer to make the texture surface. On the contrary, the metal-catalyzed chemical etching method owns the advantages of simple operation, controllable structure and easy to form the structure with high aspect ratio, indicating a wide range of application on diamond wire sawn cut multicrystalline silicon wafer. This paper systematically summarizes the work of the etching mechanisms and the structures of textures by different metal catalysts in the process of making texture surface, and deeply discusses the single and composite catalytic etching process of Ag and Cu, the structure of texture surface, and the performance of solar cells. Finally, the problems of metal-catalyzed chemical etching on the surface of diamond wire sawn cut multicrystalline silicon are analyzed, and their future research directions are prospected.

Niobate materials, such as LiNbO₃, KNbO₃, LnNbO₄ (Ln=Pr, La, Ga, Y), etc. have attracted wide attention due to their excellent photosensitivity. However, the transition metal niobate is rarely studied, and the relationship between its photoelectric properties and vacancy defects has not been thoroughly explored. Here, the effect of vacancy defect on electro-optical characteristics of ZnNb₂O₆ system was studied based on first-principles of density function theory. Its geometric structure, electronic structure, and optical spectrum clearly revealed the effect of electro- negativity and geometric position of atoms on the structure and electronic energy level. At the center of the octahedron, atoms, such as Zn and Nb, contributed similarly to the energy band, and had relatively fixed positions on the valance band when they formed vacancy defects. However, Nb atoms with larger electro-negativity generated larger lattice distortions, more obvious negative shifts of the conduction band, and red shifts of the absorption edge upon the formation of vacancy defects, which are conducive to improving electro-optical characteristics. Atom O at the vertices of the octahedron generated smaller lattice distortions when vacancy defects formed. However, negative shifts occurred at the conduction and valance bands, and impurity energy levels emerged on the Fermi surface, which induced the formation of “capture traps” on the charge carriers. This in turn exerted a larger influence on the redistribution of charge, resulting in a blue shift of the system in whole, and an all-round enhancement of optical spectrum intensity.

In order to achieve the commercialization of proton exchange membrane fuel cells (PEMFCs), it is necessary to synthesize electrocatalyst with higher electrochemical activity. In this study, PtCo nano-alloy electrocatalyst was prepared by liquid phase synthesis method with sodium borohydride as reducing agent, triethylamine as complexing agent, and by sequential heat-treatment. The physical properties of the catalyst were characterized by different analytical methods. We studied the effects of heat-treatment temperature, different amounts of sodium borohydride and triethylamine on electrochemical performance. The results show that heat-treatment can greatly improve the mass activity of the catalyst, and 500 ℃ is the optimal temperature for preparing the catalyst with the highest catalytic performance towards oxygen reduction reaction(ORR). Compared with commercial TKK-PtCo alloy catalyst under the same test system, the as-prepared catalysts exhibits advantages of more uniform particle size distribution, smaller particle size and higher electrochemical performance. In particular, the mass activity (MA) of the prepared catalyst is 133 mA/mg_Pt, which is 3 times of TKK-PtCo alloy catalyst.