Xingjiang Liu

Suppression of Lithium Dendrite Formation by Using LAGP-PEO (LiTFSI) Composite Solid Electrolyte and Lithium Metal Anode Modified by PEO (LiTFSI) in All-Solid-State Lithium Batteries

The formation of lithium dendrites is suppressed using a Li1.5Al0.5Ge1.5(PO4)3-poly(ethylene oxide) (LAGP-PEO) composite solid electrolyte and a PEO (lithium bis(trifluoromethane)sulfonimide) [PEO (LiTFSI)]-modified lithium metal anode in all-solid-state lithium batteries. The effects on the anode performance based on the PEO content in the composite solid electrolyte and the molecular weight of PEO used to modify the Li anode are studied. The structure, surface morphology, and stability of the composite solid electrolyte are examined by X-ray diffraction spectroscopy, scanning electron microscopy, and electrochemical tests. Results show that the presence of a PEO-500000(LiTFSI) film on a Li anode results in good mechanical properties and satisfactory interface contact features. The film can also prevent Li from reacting with LAGP. Furthermore, the formation of lithium dendrites can be effectively inhibited as the composite solid electrolyte is combined with the PEO film on the Li anode. The ratio of PEO in the composite solid electrolyte can be reduced to a low level of 1 wt %. PEO remains stable even at a high potential of 5.12 V (vs Li/Li+). The assembled Li-PEO (LiTFSI)/LAGP-PEO/LiMn0.8Fe0.2PO4 all-solid-state cell can deliver an initial discharge capacity of 160.8 mAh g-1 and exhibit good cycling stability and rate performance at 50 °C.

A Cross-Linking Succinonitrile-Based Composite Polymer Electrolyte with Uniformly Dispersed Vinyl-Functionalized SiO2 Particles for Li-Ion Batteries.

A cross-linking succinonitrile (SN)-based composite polymer electrolyte (referred to as CLPC-CPE), in which vinyl-functionalized SiO2 particles connect with trimethylolpropane propoxylate triacrylate (TPPTA) monomers by covalent bonds, was prepared by an ultraviolet irradiation (UV-curing) process successfully. Vinyl-functionalized SiO2 particles may react with TPPTA monomers to form a cross-linking network within the SN-based composite polymer electrolyte under ultraviolet irradiation. Vinyl-functionalized SiO2 particles as the fillers of polymer electrolyte may improve both the thermal stability of CLPC-CPE and interfacial compatibility between CLPC-CPE and electrodes effectively. There is no weight loss for CLPC-CPE until above 230 °C. The ionic conductivity of CLPC-CPE may reach 7.02 × 10(-4) S cm(-1) at 25 °C. CLPC-CPE has no significant oxidation current until up to 4.6 V (vs Li/Li(+)). The cell of LiFePO4/CLPC-CPE/Li has presented superior cycle performance and rate capability. The cell of LiFePO4/CLPC-CPE/Li may deliver a high discharge capacity of 154.4 mAh g(-1) at a rate of 0.1 C after 100 charge-discharge cycles, which is similar than that of the control cell of LiFePO4/liquid electrolyte/Li. Furthermore, the cell of LiFePO4/CLPC-CPE/Li can display a high discharge capacity of 112.7 mAh g(-1) at a rate of 2 C, which is higher than that of the cells assembled with other plastic crystal polymer electrolyte reported before obviously.

Recent advances in solid polymer electrolytes for lithium batteries

Solid polymer electrolytes are light-weight, flexible, and non-flammable and provide a feasible solution to the safety issues facing lithium-ion batteries through the replacement of organic liquid electrolytes. Substantial research efforts have been devoted to achieving the next generation of solid-state polymer lithium batteries. Herein, we provide a review of the development of solid polymer electrolytes and provide comprehensive insights into emerging developments. In particular, we discuss the different molecular structures of the solid polymer matrices, including polyether, polyester, polyacrylonitrile, and polysiloxane, and their interfacial compatibility with lithium, as well as the factors that govern the properties of the polymer electrolytes. The discussion aims to give perspective to allow the strategic design of state-of-the-art solid polymer electrolytes, and we hope it will provide clear guidance for the exploration of high-performance lithium batteries.

Effects of Fe2+ ion doping on LiMnPO4 nanomaterial for lithium ion batteries

To improve the electrochemical performance of LiMnPO4, a modified polyol reaction has been successfully developed for the preparation of LiMnxFe1−xPO4/C samples (x = 0.2, 0.5, 0.8). The secondary particles of the acquired LiMnxFe1−xPO4/C samples are spherical or annular, and the primary particles are nano-sized (20–80 nm). The LiMn0.8Fe0.2PO4/C has a higher energy density of 637 W h kg−1 compared with LiMn0.2Fe0.8PO4/C (575 W h kg−1) and LiMn0.5Fe0.5PO4/C (584 W h kg−1). The TEM image shows that the primary particles of LiMn0.8Fe0.2PO4/C are uniformly covered by a 3 nm carbon layer, and it can deliver a high discharge capacity of 161 mA h g−1 at 0.05C. At a 0.5C discharge rate, the LiMn0.8Fe0.2PO4/C can maintain 80.4% of its initial capacity after 900 cycles, and it also maintains 90% and 83% of its initial capacity at 45 °C and 55 °C respectively after 100 cycles. The results demonstrate that the modified polyol process is feasible for Fe-doping and carbon-coating to enhance the electrochemical performance of LiMnPO4.

Effects of LAGP electrolyte on suppressing polysulfide shuttling in Li–S cells

In this work, the solid electrolyte of Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is used to suppress polysulfides shuttling in Li–S cells. Firstly, the H-type visible cell is assembled by using a LAGP glass ceramic plate and normal poly-propylene (PP) separator. It is demonstrated that the LAGP glass ceramic plate is quite effective in shutting-down the migration of polysulfide ions and improving the utilization ratio of the sulfur cathode. However, in the commercial production of Li–S batteries it is not possible to use the LAGP glass ceramic plate as a membrane due to its brittle characteristics. Herein, the LAGP modified separator has been prepared by a simple casting procedure and applied in Li–S cells. The Li-ion conductivity of the LAGP modified separator is 6.280 × 10−4 S cm−1 at room temperature. The Li-ion transference number and the Gurley value of the modified separator show that the diffusion of the polysulfide anions can be suppressed effectively. The discharge capacity of the Li–S cell with the modified separator at the 50th cycle can reach 770.1 mA h g−1, while that of the Li–S cell with the routine PP separator is only 658.4 mA h g−1 at the 50th cycle. The superior utilization of sulfur in the Li–S cells indicates that using the LAGP modified separator is a viable way to overcome the shuttling problem for practical Li–S batteries.

α-MnO2 nanoneedle-based hollow microspheres coated with Pd nanoparticles as a novel catalyst for rechargeable lithium—air batteries

Abstract The hollow α-MnO2 nanoneedle-based microspheres coated with Pd nanoparticles were reported as a novel catalyst for rechargeable lithium-air batteries. The hollow microspheres are composed of α-MnO2 nanoneedles. Pd nanoparticles are deposited on the hollow microspheres through an aqueous-solution reduction of PdCl2 with NaBH4 at room temperature. The results of TEM, XRD, and EDS show that the Pd nanoparticles are coated on the surface of α-MnO2 nanoneedles uniformly and the mass fraction of Pd in the Pd-coated α-MnO2 catalyst is about 8.88%. Compared with the counterpart of the hollow α-MnO2 catalyst, the hollow Pd-coated α-MnO2 catalyst improves the energy conversion efficiency and the charge-discharge cycling performance of the air electrode. The initial specific discharge capacity of an air electrode composed of Super P carbon and the as-prepared Pd-coated α-MnO2 catalyst is 1220 mA·h/g (based on the total electrode mass) at a current density of 0.1 mA/cm2, and the capacity retention rate is about 47.3% after 13 charge-discharge cycles. The results of charge-discharge cycling tests demonstrate that this novel Pd-coated α-MnO2 catalyst with a hierarchical core-shell structure is a promising catalyst for the lithium-air battery.

Nano-SiO2-embedded poly(propylene carbonate)-based composite gel polymer electrolyte for lithium–sulfur batteries

All-solid-state electrochemical energy storage devices are highly in demand for future energy storage, where quasi-solid-state systems, such as gel polymer electrolytes, represent an important step towards this goal. Herein, a novel poly(propylene carbonate)-based composite gel polymer electrolyte (G-PPC-CPE) with 7.3 wt% ether-based electrolyte as a plasticizer was developed for a (sulfur/polyacrylonitrile)/lithium (S/PAN)/Li cell. The embedded SiO2 nanoparticles acted as multifunctional fillers, and could improve the interfacial stability and enhance the ionic conductivity and lithium ions transference number, as well as cooperate with the PPC polymer matrix to suppress the diffusion of LiPSs. Compared to the common carbonate-based electrolyte, (S/PAN)/Li with the G-PPC-CPE could deliver a higher sulfur utilization (∼100%), a high reversible capacity of 700.5 mA h gcomposite−1 (1668 mA h gsulfur−1) over 100 cycles and a long cycle life with 85% capacity retention after 500 cycles. Moreover, an inhibited self-discharge behaviour and a decent rate performance could be obtained simultaneously. XPS analysis was used to further elucidate the interaction mechanism of the nano-SiO2. The blocking effect of G-PPC-CPE for LiPSs was confirmed by XPS analysis of S 2p on the lithium anode. In brief, G-PPC-CPE guarantees good prospects for the development of quasi-solid-state LSBs with high performance at ambient temperature.

Simple method for synthesizing few-layer graphene as cathodes in surface-enabled lithium ion-exchanging cells

In order to realize a wider application for graphene materials specifically in the field of energy storage, a simple and mass-scalable method described as “the atmospheric, low-temperature, shock-heating process” is proposed in this work. During this low-temperature process, the graphite oxide without pre-treatment is completely exfoliated to form the few-layer graphene materials at atmospheric conditions. The Brunauer-Emmett-Teller (BET)-specific surface area of acquired material at 350xa0°C can reach 487xa0m2xa0g−1. The acquired few-layer graphene materials are also confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results demonstrate that this simple method is feasible for synthesizing the few-layer graphene materials. Besides that, the acquired graphene is also used as the cathode material in the surface-enabled lithium ion-exchanging cell. The galvanostatic charge/discharge tests show that the graphene prepared from this method is suitable for this system and displays a satisfactory electrochemical performance. The acquired graphene sample exhibits the reversible capacities of around 187, 107, 84, 58, and 45xa0mAhxa0g−1 at 0.1, 2, 5, 10, and 15xa0Axa0g−1, respectively. At the current density of 0.5xa0Axa0g−1, the capacity retention can reach 75xa0% after 2000xa0cycles.

Electrochemical discharging performance of 3D porous magnesium electrode in organic electrolyte

Abstract A novel type of porous magnesium electrode with a stable 3D copper foam as current collectors for the organic magnesium-air battery was prepared by both amperostatic and pulsed electrodeposition of magnesium on copper foam substrates in an electrolyte of 1 mol/L EtMgBr/THF solution, respectively. Optimal parameters of the pulsed electrodeposition were obtained using a bending cathode at the right angle. The surface morphology of the porous electrode was investigated by SEM, and the discharging performance of the porous magnesium electrode was detected by the chronoamperometric measurement. The electrochemical stability of 3D copper foam current collectors was examined by cyclic voltammetry, SEM and ICP-OES analyses. The results show that the rate capability of the porous magnesium electrode with a stable 3D copper foam as a current collector is better than that of the planar magnesium electrode, and the rate capability of the porous magnesium electrode prepared by the pulsed electrodeposition is superior to that of the porous magnesium electrode prepared by the amperostatic electrodeposition. The 3D structure of copper foam current collectors of the porous magnesium electrode could keep stable during the discharging process.

Preparation of porous Mg electrode by electrodeposition

Abstract In order to obtain a porous Mg electrode with a stable skeleton, organic Mg fuel cell (OMFC), the electrochemical behavior of Mg deposition on Cu and Ni metallic substrates in 1 mol/L EtMgBr/THF solution was investigated by SEM, EDS and electrochemical methods. The experimental results show that Mg can be electrodeposited on both substrates, as a continuous layer on a Cu substrate. Accordingly, an approach for producing a porous Mg electrode with a stable skeleton of OMFC was proposed by means of electrodeposition of Mg on a foamed Ni substrate with a layer of Cu pre-plating. The discharge performance of this porous Mg electrode of OMFC is superior to that of a planar Mg electrode.