A Highly-Fluorinated Lithium Borate Main Salt Empowering Stable Lithium Metal Batteries.

Traditional lithium salts are difficult to meet practical application demand of lithium metal batteries (LMBs) under high voltages and temperatures. LiPF6, as the most commonly used lithium salt, still suffers from notorious moisture sensitivity and inferior thermal stability under those conditions. Here, we synthesize a lithium salt of lithium perfluoropinacolatoborate (LiFPB) comprising highly-fluorinated and borate functional groups to address the above issues. It is demonstrated that the LiFPB shows superior thermal and electrochemical stability without any HF generation under high temperatures and voltages. In addition, the LiFPB can form a protective outer-organic and inner-inorganic rich cathode electrolyte interphase on LiCoO2 (LCO) surface. Simultaneously, the FPB- anions tend to integrate into lithium ion solvation structure to form a favorable fast-ion conductive LiBxOy based solid electrolyte interphase on lithium (Li) anode. All these fantastic features of LiFPB endow LCO (1.9 mAh cm-2)/Li metal cells excellent cycling under both high voltages and temperatures (e.g., 80 % capacity retention after 260 cycles at 60 °C and 4.45 V), and even at an extremely elevated temperature of 100 °C. This work emphasizes the important role of salt anions in determining the electrochemical performance of LMBs at both high temperature and voltage conditions.

Covalently Cross-Linked Chemistry of a Three-Dimensional Network Binder at Limited Dosage Enables Practical Si/C Composite Electrode Applications.

Currently, Si (or SiOx, 1 < x < 2) and graphite composite (Si/C) electrodes (e.g., Si/C450 and Si/C600 with specific capacities of 450 and 600 mAh g-1 at 0.1 C, respectively) have become the most promising alternative to traditional graphite anodes toward high-energy lithium-ion battery (LIB) applications by virtue of their higher specific capacity compared to graphite ones and improved cycle performance compared to Si (or SiOx) ones. However, such composite electrodes remain challenging to practical for implementation owing to electrode structure disintegration and interfacial instability caused by a large volume change of inner Si-based particles. Herein, we develop a covalent-bond cross-linking network binder for Si/C450 and Si/C600 electrodes via reversible addition-fragmentation chain transfer (RAFT) polymerization. The as-developed binder with a 3 mol % cross-linker of other monomers [termed P(SH-BA3%)] achieves improved mechanical and adhesive properties and decreased Si/C anode volume expansion, compared to the linear binder counterpart. Impressively, the P(SH-BA3%) binder at only 3 wt % dosage enables 83.56% capacity retention after 600 cycles at 0.5 C in Si/C450 anode based half-cells and retains 86.42% capacity retention at 0.3 C after 200 cycles and 80.95% capacity retention at 0.5 C after 300 cycles in LiNi0.8Co0.1Mn0.1O2 cathode (15 mg cm-2) based homemade soft package full cells. This work provides insight into binder cross-linking chemistry under limited dosage and enlightens cross-linking binder design toward practical Si/C electrode applications.

Self-Standing Single-Ion Borate Salt-Based Polymer Electrolyte for Lithium Metal Batteries.

Polymer electrolytes (PEs) with excellent flexibility and superior compatibility toward lithium (Li) metal anodes have been deemed as one of the most promising alternatives to liquid electrolytes. However, conventional lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based dual-ion PEs suffer from a low Li ion transference number and notorious Li dendrite growth. Here, a single-ion conducting polyborate salt without any fluorinated groups, polymeric lithium dihydroxyterephthalic acid borate (PLDPB), is presented for addressing the issues of Li metal batteries. Owing to a nearly immovable bulky anion and the presence of a rigid benzene structure, the PLDPB@poly(ethylene oxide) (PEO) PE exhibits an ultrahigh Li ion transference number (0.94) and excellent mechanical strength, which could significantly restrict the growth of Li dendrites. Postmortem analysis reveals that a fluorine-free solid electrolyte interphase (SEI) enriched with B-O and benzene-containing species is formed on the surface of the Li metal anode, thereby facilitating elimination of excessive parasitic reactions and simultaneously suppressing the formation of Li dendrites. Consequently, the LiFePO4/Li cells with PLDPB@PEO PEs show an improved long-term cycling performance and high capacity retention (90.0%) and Coulombic efficiency (99.9%) after 500 cycles. This work may inspire new ideas to boost the development of single-ion conducting salts for dendrite-free Li metal batteries.

Correlation between physical fitness and reading ability among school aged children / 中国学校卫生

Objective@#To determine the association between physical health fitness with Chinese reading ability of schoolaged children, so as to provide evidence for improving children s reading ability.@*Methods@#A questionnaire survey was conducted among 1 923 school aged children in grades 2-6 in a primary school in Wuhan, Hubei Province, China. The questionnaire included basic demographic information and Dyslexia Checklist for Chinese Children and the Pupil Rating Scale Revised Screening. At the same time, participants underwent physical fitness tests which included an assessment of height, weight, and lung capacity, as well as a 50 meter run, sit forward bend, one minute skipping rope task, sit ups, and a 50 × 8 round trip.@*Results@#A total of 59 children were identified with dyslexia. Normal children achieved higher scores than children with dyslexia in the total physical health score, as well as the one minute skipping rope score, one minute sit up score, and sitting forward score ( P <0.05). Multiple linear regression analyses showed that the reading ability of girls was higher than that of boys ( β =-3.04, P <0.01), and the children who regularly participated in more intense physical activity and who had higher fitness scores had a higher reading ability ( β =-1.68, -0.08, P <0.01). Children s reading ability increased significantly with parental educational level( P <0.05).@*Conclusion@#Gender, parents education level, physical exercise intensity, and children s physical fitness were identified as influencing factors of school age children s reading ability. A positive correlation was found between children s physical health level and reading ability.