Revisiting Electrolyte Kinetics Differences in Sodium Ion Battery:Are Esters Really Inferior to Ethers?

The ether electrolytes usually outperform ester electrolytes by evaluating sodium-ion batteries(SIBs)rate performance,which is a near-unanimous conclusion of previous studies based on an essential configuration of the half-cell test.However,here we find that contrary to consensus,the ester electrolyte shows better Na storage capability than the ether electrolyte in full cells.An in-depth analysis of three-electrode,symmetric cell,and in situ XRD tests indicates that traditional half-cell test results are unreliable due to interference from Na electrodes.In particular,Na electrodes show a huge stability difference in ester and ether electrolytes,and ester electrolytes suffer more severe interference than ether electrolytes,resulting in the belief that esters are far inferior to ether electrolytes.More seriously,the more accurate three-electrode test would also suffer from Na electrode interference.Thus,a“corrected half-cell test”protocol is developed to shield the Na electrode interference,revealing the very close super rate capability of hard carbon in ester and ether electrolytes.This work breaks the inherent perception that the kinetic properties of ester electrolytes are inferior to ethers in sodium-ion batteries,reveals the pitfalls of half-cell tests,and proposes a new test protocol for reliable results,greatly accelerating the commercialization of sodium-ion batteries.

Nitrogen-doped lignin based carbon microspheres as anode material for high performance sodium ion batteries

Nitrogen-doped lignin-based carbon microspheres are synthesized using 3-aminophenol as a nitrogen source by the hydrothermal method.The structural change and the effect on the electrochemical properties are systematically investigated. Nitrogen-doped lignin-based carbon microspheres represent well-developed spherical morphology with many active sites, ultramicroporous(< 0.7 nm) structure, and large interlayer spacing. Consistent with the obtained physical structures and properties, the nitrogen-doped carbon microspheres exhibit fast sodium ion adsorption/intercalation kinetic process and excellent electrochemical performance. For example, a reversible specific capacity of 374 m Ah g^(-1) at 25 m A g^(-1) with high initial coulombic efficiency of 85% and high capacitance retention of 90% after 300 cycles at 100 m A g^(-1) and stable charge/discharge behavior at different current density is obtained. The additional defects and abundant ultramicroporous structure can enhance sloping capacity, and large interlayer spacing is considered to be the reason for improving plateau capacity.

A solvothermal pre-oxidation strategy converting pitch from soft carbon to hard carbon for enhanced sodium storage

Due to its low cost and easy availability, the pitch is considered a promising precursor for soft carbon anodes. However, pitch-derived soft carbon shows a high graphitization degree and small interlayer spacing, resulting in its much lower sodium storage performance than hard carbon. We propose a novel preoxidation strategy to introduce additional oxygen atoms into the low-cost soft carbon precursor pitch to fabricate a defect-rich and large-interlayer spacing hard carbon anode(HPP-1100). Compared with the direct pyrolysis of pitch carbon, the sodium storage capacity of HPP-1100 is significantly improved from 120.3 m Ah/g to 306.7 m Ah/g, with an excellent rate and cycling capability(116.5 m Ah/g at 10 C). Moreover, when assorted with an O_(3)-Na(NiFeMn)1/3O_(2)cathode, the full cell delivers a high reversible capacity of 274.0 m Ah/g at 0.1 C with superb cycle life. This work provides a new solution for realizing the application of low-cost pitch anodes in Na-ion batteries.

High-voltage,low-temperature supercapacitors enabled by localized“water-in-pyrrolidinium chloride”electrolyte

Aqueous electrolytes offer superior prospects for advanced energy storage.“Water-in-salt”(WIS)electrolytes exhibit a wide electrochemical stability window(ESW),but their low conductivity,high viscosity,and precipitation at low temperatures restrict their application.Herein,we report a novel localized“water-in-pyrrolidinium chloride”electrolyte(LWIP;1 mol/L,N-propyl-N-methylpyrrolidinium chloride/(water and N,Ndimethylformamide,1:4 by molality))enabling high-voltage,low-temperature supercapacitors(SCs).The greatly improved ESW(3.451 V)is mainly attributed to the strong solvation between Cl-and water molecules,which broadens the negative stability.This water-binding mechanism is very different from that of a WIS electrolyte based on alkali metal salt.SCs using LWIP electrolytes not only yield a high operating voltage of 2.4 V and excellent capacity retention(82.8%after 15,000 cycles at 5 A g^(-1))but also operate stably at-20℃.This work provides new approaches for the design and preparation of novel electrolytes.

Mesoporous carbon material as cathode for high performance lithium-ion capacitor

Mesoporous carbon(MC) material with high specific surface area(1432 m^2/g), large pore volume(2.894 cm^3/g) and appropriate mesopore structure(about 6.5 nm) has been prepared. We use the magnesium citrate as the precursor of the carbon material and the nano-sized magnesium oxide(MgO)particles as template provided by magnesium citrate. The structure characterization and the electrochemical performance of MC are investigated. Compared with commercial activated carbon(AC) cathode, the utilization of MC cathode can obviously improve the energy density of LIC device. When the MC cathode is coupled with pre-lithiated hard carbon(HC) anode, the LIC device shows the optimal electrochemical performance, high energy density up to 95.4 Wh/kg and power density as high as 7.4 kW/kg(based on active material mass of two electrodes), excellent capacity retention of 97.3% after 2000 cycles. The present work indicates the combination of MC electrode with HC electrodes as promising candidates for the realization of LIC with high energy density, high power density and long cycle life.

Synthesis and magnetic property of a nitroxide based on C60

The compounds containing stable nitroxide radicals possess magnetic properties for the free radical have net magnetic moment. Oxidization of the [60]fulleropyrolidine obtained from the reaction of C60 with diketone and 2-aminoisobutyric acid by m-chloroperoxybenzoic acid gives a new nitroxide integrated with C60. The stable nitroxide based on C60 is confirmed to be antiferro-magnetism with quantum design superconducting quantum interference device (SQUID).

Synthesis and antioxidative properties of polyphenol-fullerenes

Fullerene derivatives have exhibited fascinating properties in biological systems. Several antioxidative hindered phenol units were connected to Ceo called radical sponge, resulting in its excellent solubility in polar solvents. The stable radical scavenging experiments were performed with electron spin resonance spectroscopy. The results indicate that both samples show desirable efficiency in eliminating free radicals.

Facile cyclic ammonium salt with the smallest size for high performance electric double layer capacitors

The smallest cyclic ammonium salt reported to date, N,N-dimethylpyrrolidinium tetrafluoroborate (P11-BF4), was successively synthesized using a synthesis route without metal ions and halogen ions, then investigated as the electrolyte with Propylene carbonate in EDLCs. The electrochemical characteristics of EDLCs assembled by 1 mol/L P11-BF4/PC paired with activated carbon electrodes were compared to traditional electrolytes. P11-BF4 has proven to have superior voltage resistance by using cyclic voltammetry and constant current charge-discharge testing. Moreover, P11-BF4 exhibits a more brilliant rate performance due to its high conductivity. These results demonstrate that P11-BF4 is an ideal electrolyte to improve the energy density and power density of supercapacitors.

Copper-sulfide cluster assembled architecture via in situ reaction

A new copper-thiolate cluster assembled framework[Cu2(μ4-SCH3)Cl]n(1),has been solvothermally synthesized through in situ reaction viz.,in situ ligand generation and metal reduction.Compound 1 represents the first 3 D framework based on Atlas-sphere functionalized by singleμ2-Cl groups.DOS calculation reveals the interaction of electronic structures.It is found that the HOMO is mainly distributed on Cl,Cu and S bonding orbitals,while the LUMO is dominated by Cu-Cl antibonding orbitals.

Supercapacitors

Due to outstanding storage capacity,ultra-high power density,super long cycle life time,moderate energy density and high safety,supercapacitors have enthusiastically become a new type of energy storage device and energy storage technology after lithium ion battery.In the recent decade,scientists and engineers around the world have extensively and thoroughly studied physics,chemistry,materials,chemical engineering,electronics,transportation engineering,energy science and technology,aeronautical and astronautics science and technology,which promoted