4-(Trimethylsiloxy)-3-pentene-2-one (TMSPO) is tested as an electrolyte additive to enhance Coulombic efficiency and cycle retention for the Li/ LiNi 0.5 Mn 1.5 O 4 (LNMO) half-cell and graphite/LNMO fullcell. TMSPO carries two functional groups, siloxane (−Si− O−) and carbon−carbon (CC) double bonds. It is found that the siloxane group reacts with hydrogen fluoride (HF), which is generated by hydrolysis of lithium hexafluorophosphate (LiPF 6 ) by impure water in the electrolyte solution, to produce 4-hydroxypent-3-ene-2-one (HPO). The as-generated HPO, as well as TMSPO itself, is electrochemically oxidized to form a protective surface film on the LNMO electrode, in which it is inferred that the carbon−carbon (CC) double bond initiates radical polymerization. The surface film derived from the TMSPO-added electrolyte shows a superior passivating ability to that generated from the pristine (TMSPO-free) electrolyte. The suppression of electrolyte oxidation enabled by the superior passivating ability offers two beneficial features to the half-cells and full-cells: the suppression of both HF generation and deposition of the resistive surface film on LNMO. As a result, the metal dissolution by HF attack on LNMO appears to be smaller by the addition of TMSPO. The cell polarization is also less significant because of the latter beneficial feature. In short, the bifunctional activity of TMSPO (HF scavenger and protective film former) allows an enhanced Coulombic efficiency and cycle retention to the half-cell and full-cell.
Biodegradable and non-toxic multi-block copolymers based on poly(L-lysine) and poly(ethylene glycol) were synthesized. Synthesized copolymers showed almost negligible cytotoxicity above 95% cell viability and transfection efficiency compared to the PLL homopolymer with molecular weight of 25,700. Biodegradation under physiological conditions revealed that the molecular weight of copolymers decreased to 20% of the initial molecular weight within 72 h. Transfection efficiencies of copolymers were not affected by the presence of serum, while that of PLL homopolymer decreased to the level of naked DNA in the presence of serum. Based on the results, the new copolymers are believed to be a potentially efficient carrier for the delivery of bioactive agents.
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