Phosphonate-Functionalized Ionic Liquid Gel Polymer Electrolyte with High Safety for Dendrite-Free Lithium Metal Batteries.

The conventional lithium-ion battery technology relies on the liquid carbonate-based electrolyte solution, which causes excessive side reactions, serious risk of electrolyte leakage, high flammability, and significant safety hazards. In this work, phosphonate-functionalized imidazolium ionic liquid (PFIL) is synthesized and used as a gel polymer electrolyte (GPE) to replace the organic carbonate-based electrolyte solution. The as-prepared ionic liquid-based gel polymer electrolyte (IL-GPE) shows low crystallinity, flame retardance, and excellent electrochemical performance. Thanks to the fast double channel transport of lithium ions in the IL-GPE electrolyte, a high ionic conductivity of 0.48 mS cm-1 and a lithium-ion transference number of 0.37 are exhibited. Symmetrical lithium cells with IL-GPE retain stable cycling even after 3000 h under 0.1 mA cm-2. IL-GPE exhibits good compatibility toward lithium metal, yielding excellent long-term electrochemical kinetic stability. IL-GPE induces the formation of a uniform and robust SEI layer, inhibiting the growth of lithium dendrites and improving the rate performance and cycle stability. Furthermore, Li/LiFePO4 cells exhibit a specific capacity of 63 mA h g-1 after 150 cycles at 5.0 C, with a capacity retention of 90.2%. It is foreseen that this GPE is a promising candidate to enhance the safety of high-performance lithium metal batteries.

Enhanced high voltage performance of LiNi0.5Mn0.3Co0.2O2 cathode via the synergistic effect of LiPO2F2 and FEC in fluorinated electrolyte for lithium-ion batteries.

LiNi0.5Mn0.3Co0.2O2 can achieve high energy density due to its merits of high theoretical capacity and a relatively high operating voltage, but the LiNi0.5Mn0.3Co0.2O2 battery suffers from capacity decay because of the unstable solid electrolyte interface on the cathode. Herein, we investigate the application of a fluorinated electrolyte composed of fluoroethylene carbonate (FEC) as a cosolvent and lithium difluorophosphate (LiPO2F2) as a salt-type additive extending the life span of the LiNi0.5Mn0.3Co0.2O2 cathode. LiNi0.5Mn0.3Co0.2O2 can achieve and maintain a capacity of 157.7 mA h g-1 over 200 cycles at a 1C rate between 3.0 and 4.4 V, as well as a reversible capacity of 132.7 mA h g-1 even at the high rate of 10C. The enhanced performance can be ascribed to the formation of the robust and protective fluorinated organic-inorganic film on the cathode, which derives from the FEC cosolvent and LiPO2F2 additive and ensures facile lithium-ion transport. The synergistic effect of the cosolvent and additive to boost the electrochemical performance of LiNi0.5Mn0.3Co0.2O2 cathode will pave a new pathway for high-voltage cathode materials.

Flexible poly(vinylidene fluoride-co-hexafluoropropylene)-based gel polymer electrolyte for high-performance lithium-ion batteries.

Gel polymer electrolytes (GPEs) have attracted ever-increasing attention in Li-ion batteries, due to their great thermal stability and excellent electrochemical performance. Here, a flexible poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based GPE doped with an appropriate proportion of the PEO and SiO2 is developed through a universal immersion precipitation method. This porous PVDF-HFP-PEO-SiO2 GPE with high ionic conductivity and lithium-ion transference number (t Li+ ) can enhance the electrochemical performance of LiFePO4 cells, leading to superior rate capability and excellent cycling stability. Moreover, the PVDF-HFP-PEO-SiO2 GPE effectively inhibits the lithium dendrite growth, thereby improving the safety of Li-ion batteries. In view of the simplicity in using the gel polymer electrolyte, it is believed that this novel GPE can be used as a potential candidate for high-performance Li-ion batteries.

Mesoporous Polymer-Derived Ceramic Membranes for Water Purification via a Self-Sacrificed Template.

Membrane separation has been widely used in water purification, and mesoporous ceramic membranes show a high potential in the future because of their high stability and resistance to harsh environments. In the current study, a novel polymer-derived ceramic silicon oxycarbide (SiOC) membrane was developed via a preceramic reactive self-sacrificed method and was further applied in a homemade dead-end system for water purification. A cyclosiloxane hybrid polymer was selected as the precursor and polydimethylsiloxane (PDMS) was used as the sacrificial template. Membrane pores were formed because of template removal during the sintering process, creating channels for water transportation. The pore size and porosity could be readily adjusted by changing the amounts and types of PDMS used in the fabrication process. The as-prepared SiOC membrane showed a high water permeability (140 LMH@2.5 bar) and high removal rate of rhodamine B (RhB), demonstrating its potential applications in water treatment. This work would provide an easy and scalable method to prepare ceramic membranes with a controlled pore size, which could be used for different water treatment applications.

Hierarchical porous ZnMnO3 yolk-shell microspheres with superior lithium storage properties enabled by a unique one-step conversion mechanism.

ZnMnO3 has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity. However, it suffers from capacity fading because of the large volumetric change during cycling. Here, porous ZnMnO3 yolk-shell microspheres are developed through a facile and scalable synthesis approach. This ZnMnO3 can effectively accommodate the large volume change upon cycling, leading to an excellent cycling stability. When applying this ZnMnO3 as the anode in lithium-ion batteries, it shows a remarkable reversible capacity (400 mA h g-1 at a current density of 400 mA g-1 and 200 mA h g-1 at 6400 mA g-1) and excellent cycling performance (540 mA h g-1 after 300 cycles at 400 mA g-1) due to its unique structure. Furthermore, a novel conversion reaction mechanism of the ZnMnO3 is revealed: ZnMnO3 is first converted into intermediate phases of ZnO and MnO, after which MnO is further reduced to metallic Mn while ZnO remains stable, avoiding the serious pulverization of the electrode brought about by lithiation of ZnO.