Jingze Li

Improved Electrochemical Performance of LiCoO2 Electrodes with ZnO Coating by Radio Frequency Magnetron Sputtering

Surface modification of LiCoO2 is an effective method to improve its energy density and elongate its cycle life in an extended operation voltage window. In this study, ZnO was directly coated on as-prepared LiCoO2 composite electrodes via radio frequency (RF) magnetron sputtering. ZnO is not only coated on the electrode as thin film but also diffuses through the whole electrode due to the intrinsic porosity of the composite electrode and the high diffusivity of the deposited species. It was found that ZnO coating can significantly improve the cycling performance and the rate capability of the LiCoO2 electrodes in the voltage range of 3.0-4.5 V. The sample with an optimum coating thickness of 17 nm exhibits an initial discharge capacity of 191 mAh g(-1) at 0.2 C, and the capacity retention is 81% after 200 cycles. It also delivers superior rate performance with a reversible capacity of 106 mAh g(-1) at 10 C. The enhanced cycling performance and rate capability are attributed to the stabilized phase structure and improved lithium ion diffusion coefficient induced by ZnO coating as evidenced by X-ray diffraction, cyclic voltammetry, respectively.

Electrochemical characterization of Co3O4/MCNTs composite anode materials for sodium-ion batteries

A composite of transition metal oxide Co3O4 and multiwalled carbon nanotubes (MCNTs) was applied as an anode material for sodium-ion batteries via a simply modified solid-state reaction and sonication method. The as-prepared Co3O4/MCNTs composite shows improved electrochemical performance than bare Co3O4 owing to the Co3O4/MCNTs nanostructure that benefits Na ion and electronic transport together with buffering the large volume change of Co3O4 during charging and discharging process. Additionally, the Na-storage behavior and the original capacity loss of Co3O4 based on the conversion reaction have been investigated through cyclic voltammogram, X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. It is firstly demonstrated that in discharge state, Co3O4 particles initially react with Na to produce CoO and then is further reduced to nanosized Co in an amorphous sodium oxides matrix. In the charge process, Co nanoparticles were partially oxidized to Co3O4, the other part of the CoO remain leading capacity loss. These results offer new insights into the electrochemical process of transition metal-based anode materials for Na-ion batteries.

Porous Li2C8H4O4 coated with N-doped carbon by using CVD as an anode material for Li-ion batteries

Lithium terephthalate (Li2C8H4O4) and its carboxylate-based derivatives have been proposed as advanced organic anodes for low cost lithium/sodium ion batteries. One of the key barriers for practical application is poor rate capability due to the intrinsic low electronic conductivity of most organic materials at room temperature. To overcome this issue, porous microspheres consisting of Li2C8H4O4 nanoparticles were synthesized by a common spray drying method for the first time. Furthermore, a straight-forward surface coating technique was developed using urea powder as nitrogen and carbon sources simultaneously. Consequently, a N-doped carbon layer was uniformly coated onto nanostructured Li2C8H4O4 electroactive material at 400 °C by chemical vapor deposition. The composite electrode displays excellent electrochemical performance under high current rate even at room temperature.

Extremely Accessible Potassium Nitrate (KNO3) as the Highly Efficient Electrolyte Additive in Lithium Battery.

The systematic investigation of RNO3 salts (R = Li, Na, K, and Cs) as electrolyte additives was carried out for lithium-battery systems. For the first time, the abundant and extremely available KNO3 was proved to be an excellent alternative of LiNO3 for suppression of the lithium dendrites. The reason was ascribed to the possible synergetic effect of K(+) and NO3(-) ions: The positively charged K(+) ion could surround the lithium dendrites by electrostatic attraction and then delay their further growth, while simultaneously the oxidative NO3(-) ion could be reduced and subsequently profitable to the reinforcement of the solid-electrolyte interphase (SEI). By adding KNO3 into the practical Li-S battery, the discharging capacity was enhanced to average 687 mAh g(-1) from the case without KNO3 (528 mAh g(-1)) during 100 cycles, which was comparable to the one with the well-known LiNO3 additive (637 mAh g(-1)) under the same conditions.

Dicarboxylate CaC8H4O4 as a high-performance anode for Li-ion batteries

Currently, many organic materials are being considered as electrode materials and display good electrochemical behavior. However, the most critical issues related to the wide use of organic electrodes are their low thermal stability and poor cycling performance due to their high solubility in electrolytes. Focusing on one of the most conventional carboxylate organic materials, namely lithium terephthalate Li2C8H4O4, we tackle these typical disadvantages via modifying its molecular structure by cation substitution. CaC8H4O4 and Al2(C8H4O4)3 are prepared via a facile cation exchange reaction. Of these, CaC8H4O4 presents the best cycling performance with thermal stability up to 570 °C and capacity of 399 mA·h·g−1, without any capacity decay in the voltage window of 0.005–3.0 V. The molecular, crystal structure, and morphology of CaC8H4O4 are retained during cycling. This cation-substitution strategy brings new perspectives in the synthesis of new materials as well as broadening the applications of organic materials in Li/Na-ion batteries.

Rice husk derived carbon–silica composites as anodes for lithium ion batteries

Carbon–silica composites were obtained via simply heating rice husk at 900 °C under a N2 atmosphere. This composite exhibits a high capacity and superior cycling performance as an anode for lithium ion batteries.

Quick Fabrication of Large-area Organic Semiconductor Single Crystal Arrays with a Rapid Annealing Self-Solution-Shearing Method

In this paper, we developed a new method to produce large-area single crystal arrays by using the organic semiconductor 9, 10-bis (phenylethynyl) anthracene (BPEA). This method involves an easy operation, is efficient, meets the demands of being low-cost and is independent of the substrate for large-area arrays fabrication. Based on these single crystal arrays, the organic field effect transistors exhibit the superior performance with the average mobility extracting from the saturation region of 0.2 cm2 V−1s−1 (the highest 0.47 cm2 V−1s−1) and on/off ratio exceeding 105. In addition, our single crystal arrays also show a very high photoswitch performance with an on/off current ratio up to 4.1 × 105, which is one of the highest values reported for organic materials. It is believed that this method provides a new way to fabricate single crystal arrays and has the potential for application to large area organic electronics.

Stable macroscopic nanocylinder arrays in an amphiphilic diblock liquid-crystalline copolymer with successive hydrogen bonds

In bulk films of a novel well-defined amphiphilic diblock liquid-crystalline copolymer with aramid moieties, a stable perpendicularly orientated hydrophilic nanocylinder array with hexagonal packing was formed in a large area by supramolecular self-assembly.

Pretreatment of Lithium Surface by Using Iodic Acid (HIO3) To Improve Its Anode Performance in Lithium Batteries

Iodic acid (HIO3) was exploited as the effective source to build an artificial solid-electrolyte interphase (SEI) on the surface of Li anode. On one hand, HIO3 is a weak solid-state acid and can be easily handled to remove most ion-insulating residues like Li2CO3 and/or LiOH from the pristine Li surface; on the other hand, both the products of LiI and LiIO3 resulted from the chemical reactions between Li metal and HIO3 are reported to be the ion-conductive components. As a result, the lower voltage polarization and impedance, longer cycling lifetime and higher Coulombic efficiency have been successfully achieved in the HIO3-treated Li-Li and Li-Cu cells. By further using the HIO3-treated Li anode into practical Li-S batteries, the impressive results also have been obtained, with average discharge capacities of 719 mAh g-1 for 200 cycles (0.2 C) and 506 mAh g-1 for 500 cycles (0.5 C), which were better than the Li-S batteries using the pristine Li anode (552 and 401 mAh g-1, respectively) under the same conditions.

A better understanding of the capacity fading mechanisms of Li3V2(PO4)3

Lithium vanadium phosphate Li3V2(PO4)3 (LVP) has emerged as an appealing cathode material for next generation lithium-ion batteries owing to its high theoretical capacity (197 mA h g−1) and high average working potential around 4.0 V vs. Li/Li+. However, the capacity fading problem limits its practical application, especially when a high cut-off voltage over 4.3 V is applied. In this study, the capacity fading mechanisms of LVP in different voltage windows of 3.0–4.3 V and 3.0–4.8 V are studied systematically by using electrochemical impedance spectroscopy, a galvanostatic intermittent titration technique, cyclic voltammetry, and in situ X-ray absorption spectroscopy. Surprisingly, the structure of LVP can be fully recovered after one cycle (even for a cut-off voltage as high as 4.8 V). It indicates that LVP is a promising cathode system with excellent structure reversibility intrinsically. We revealed that the capacity fading during high voltage cycling is mainly due to the parasitic reaction with the electrolyte, kinetics limitation and V dissolution, rather than LVP structure degradation. In addition, a “crystalline–amorphous–crystalline” phase transition pathway was revealed during the LVP synthesis process of the solid-state reaction by using synchrotron based in situ X-ray diffraction.