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Sodium-ion batteries (SIBs) have been considered as one of foremost promising alternatives for the widely used lithium-ion batteries. In order to assemble high-performance SIBs, cathode materials with stable structure and superior electrochemical properties are needed emphatically. In this work, we prepare a new layered oxide material, P2-type Na2/3Mn1/2Co1/3Cu1/6O2 (P2-MCC) with the morphology of hexagonal micro-prisms, by a sol-gel method. When used as cathode material for SIBs, the P2-MCC exhibits good cycling stability (e.g., >83.5% capacity retention after 100 cycles at 100 mA g−1) and superior high-rate performance. Moreover, it also owns an attractive ability of fast-charging, e.g., a high capacity retention of ∼66% after 100 cycles as charging at a high current density of 200 mA g−1 and discharging at a low current density of 10 mA g−1. Such good electrochemical properties can be originated from the synergetic improvement of selected multi-metallic ions and enhanced electrode kinetics (high apparent Na-diffusion kinetics) which is demonstrated by the galvanostatic intermittent titration technique, electrochemical impedance spectroscopy and cyclic voltammetry at various scan rates.

As a promising cathode material of sodium-ion battery, P2-type Na2/3Ni1/3Mn2/3O2 (NNMO) possesses a theoretically high capacity and working voltage to realize high energy storage density. However, it still suffers from poor cycling stability mainly incurred by the undesirable P2–O2 phase transition. Herein, the electrochemically active Fe3+ ions are introduced into the lattice of NNMO, forming Na2/3Ni1/3Mn2/3–xFexO2 (x = 0, 1/24, 1/12, 1/8, 1/6) to effectively stabilize the P2-type crystalline structure. In such Fe-substituted materials, both Ni2+/Ni4+ and Fe3+/Fe4+ couples take part in the redox reactions, and the P2–O2 phase transition is well restrained during cycling, as verified by ex situ X-ray diffraction. As a result, the optimized Na2/3Ni1/3Mn7/12Fe1/12O2 (1/12-NNMF) has a long-term cycling stability with the fading rate of 0.05% per cycle over 300 cycles at 5 C. Furthermore, the 1/12-NNMF delivers excellent rate capabilities (65 mA h g–1 at 25 C) and superior low-temperature performance (the cap...

Developing a high-performance, low-cost, and safer rechargeable battery is a primary challenge in next-generation electrochemical energy storage. In this work, a quasi-solid-state (QSS) sodium-ion full battery (SIFB) is designed and fabricated. Hard carbon cloth derived from cotton cloth and Na3V2(PO4)2O2F (NVPOF) are employed as the anode and the cathode, respectively, and a sodium ion-conducting gel-polymer membrane is used as both the QSS electrolyte and separator, accomplishing the high energy and power densities in the QSS sodium-ion batteries. The energy density can reach 460 W h kg–1 according to the mass of the cathode materials. Moreover, the fabricated QSS SIFB also exhibits an excellent rate performance (e.g., about 78.1 mA h g–1 specific capacity at 10 C) and a superior cycle performance (e.g., ∼90% capacity retention after 500 cycles at 10 C). These results show that the developed QSS SIFB is a hopeful candidate for large-scale energy storage.

Simple yet efficient design of an outstanding multifunctional electrocatalyst is crucial for advanced energy conversion and storage devices. Herein, we report the synthesis of an N-enriched hierarchically porous carbon electrocatalyst, which demonstrated excellent overall oxygen electrode activity (ΔE = EOER,10 − EORR,1/2 of 0.770 V) and impressive durability in 0.1 M KOH. The activity of our material integrates a high BET surface area (1547.13 m2 g−1), accessible N dopant and suitable porous architectures. The material is formed by mixing cicada sloughs with ZnCl2, as the inorganic pore-fabricating agent, with ball milling followed by annealing treatment. Unexpectedly, the nitrogen reduction reaction (NRR) with excellent production yield (NH3: 15.7 μg h−1 mg−1 cat., faradaic efficiency: 1.45%) and selectivity is achieved at −0.2 V vs. RHE under ambient conditions. The present trifunctional catalytic activities are markedly better than leading results reported in recent literature. These results highlight the significance of deliberate structural engineering in the preparation of multifunctional electrocatalysts for versatile electrochemical reactions.

Recently, sodium-ion batteries (SIBs) have been considered as the promising alternative for lithium-ion batteries. Although layered P2-type transition metal oxides are an important class of cathode materials for SIBs, there are still some hurdles for the practical applications, including low specific capacity as well as poor cycling and rate properties. In this study, the electrochemical properties of layered Mn-based oxides have been effectively improved via Al doping, which cannot only promote the formation of layered P2-type structure in the preparation processes but also stabilize the lattice during the successive Na-intercalation/deintercalation due to suppression of the Jahn-Teller distortion of Mn3+. Among the as-prepared series of Na2/3Mn1-xAlxO2 (x = 0, 1/18, 1/9, and 2/9), Na2/3Mn8/9Al1/9O2 with x = 1/9 exhibits the optimal doping effect with the best electrochemical properties, in terms of the highest specific capacity of 162.3 mA h g−1 at 0.1 C, the highest rate capability, and the best cycling stability in comparison to the undoped Na2/3MnO2 and the other two materials with different Al-doped contents. Both cyclic voltammetry at varied scan rates and galvanostatic intermittent titration technique disclose the optimal electrode kinetics (the highest Na-diffusion coefficient) of the best Na2/3Mn8/9Al1/9O2.

An advanced hierarchically porous nanosheets-constructed three-dimensional (3D) carbon material (HPNSC) is prepared by using low-cost agricultural waste-nelumbium seed-pods as the precursor, and potassium hydroxide (KOH) as the activator. The as-prepared HPNSC material has a hierarchically porous nanosheets-constructed structure with 3D carbon nanosheet network morphology, which can enable fast and efficient transfer of Li+/Na+/H+ during charge-discharge process. The assembled HPNSC//HPNSC symmetric supercapacitors exhibit an improved energy density of 41.3 W h kg-1 with a power density of 180 W kg-1 in 1 mol l-1 Na2SO4 electrolyte. The energy density can still be maintained at 16.3 W h kg-1 even if the power density is increased to 9000 W kg-1. When acting as the reversible electrode for lithium ion batteries, this HPNSC material can achieve a high specific capacity of 1246 mA h g-1 at 0.1 A g-1. Moreover, sodium ion battery with HPNSC electrode exhibits excellent cycling performance of 161.8 mA h g-1 maintained even after being cycled 3350 times. The electrochemical performances clearly indicate that the HPNSC developed in this work is a very promising energy storage electrode material, and can further provide new insights for designing and developing highly porous materials for energy storage in other fields.

As a promising cathode material of sodium-ion battery, P2-type Na

In order to develop promising anode materials for sodium-ion batteries (SIBs), a novel pie-like FeS@C (P-FeS@C) nanohybrid, in which all ultrasmall FeS nanocrystals (NCs) are completely embedded into the carbon network and sealed by a protective carbon shell, has been prepared. The unique pie-like structure can effectively speed up the kinetics of electrode reactions, while the carbon shell stabilizes the FeS NCs inside. Studies show that the electrochemical reaction processes of P-FeS@C electrodes are dominated by the pseudocapacitive behavior, leading to an ultrafast Na+-insertion/extraction reaction. Hence, the prepared P-FeS@C nanohybrid exhibits superior Na-storage properties especially high rate capability in half cells. For example, it can deliver reversible capacities of 555.1 mA h g−1 at 0.2 A g−1 over 150 cycles and about 60.4 mA h g−1 at 80 A g−1 (an ultrahigh current density even higher than that of the capacitor test). Furthermore, an advanced P-FeS@C//Na3V2(PO4)2O2F full cell has been assembled out, which delivers a stable specific capacity of 441.2 mA h g−1 after 80 cycles at 0.5 A g−1 with a capacity retention of 91.8%.