In situ preparation of gel polymer electrolyte for lithium batteries: Progress and perspectives

The practical applications of Li-ion batteries(LIBs)are challenged by their safety concerns when using liquid electrolytes(LEs).Solid-state gel polymer electrolytes(GPEs)can address this challenge and have drawn increased attention recently.Normally,GPEs are prepared separately and then assembled into cells,which undoubtedly result in dissatisfactory solid/solid interfacial compatibility and low ionic conductivity.Fortunately,in situ GPEs are proposed to address the above challenges and simplify the preparation process.Typically,LE precursor is injected into the cells and gradually transformed into a quasisolid gel state under the conditions of thermal or chemical initiators.Consequently,the obtained in situ GPEs could fully infiltrate the electrode and better interface contact of gel electrolyte/electrode is thus inherited.In this review,the authors focus on the in situ GPEs used in lithium batteries(LBs),and summarize recent progress of the design,synthesis,and applications of in situ GPEs.Based on the different ways of triggering polymerization,there are mainly three methods:thermochemical gelation,polymerization by additional chemical initiators,and cross-linking initiated by Li O bond.Composite GPEs based on in situ solidification method are introduced as a promising strategy to improve the electrochemical performances.Finally,up-to-date research progresses are discussed,and perspectives are provided on the development and challenges of in situ GPEs to meet the requirements for their practical applications in LBs.

Stochastic ravitational wave background from PBH-ABH mergers

The measurement of gravitational waves produced by binary black-hole mergers at the Advanced LIGO has encouraged extensive studies on the stochastic gravitational wave background. Recent studies have focused on gravitational wave sources made of the same species, such as mergers from binary primordial black holes or those from binary astrophysical black holes. In this paper, we study a new possibility - the stochastic gravitational wave background produced by mergers of one primordial black hole and one astrophysical black hole. Such systems are necessarily present if primordial black holes exist. We study the isotropic gravitational wave background produced through the history of the universe. We find it is very challenging to detect such a signal. We also demonstrate that it is improper to treat the gravitational waves produced by such binaries in the Milky Way as a directional stochastic background due to a very low binary formation rate.