Preparation And Characterization Of MOFs/ Polymer Electrospun Fiber Membranes For Lithium Batteries

In the past decade,with the increasing demand for new energy technology applications such as portable electronic devices and electric vehicles,people put forward higher requirements for high energy density and long cycle lithium batteries.As one of the important components of lithium batteries,membranes can not only prevent the short circuit between the positive electrode and the negative electrode due to physical contact,but also can effectively transport ions.At present,the membrane used in commercial lithium-ion batteries is usually olefin composite separators,but this kind of membranes still has various defects.Such as poor thermal stability,there will be significant contraction at high temperature;With poor mechanical properties,the growth of lithium dendrite is easy to puncture membranes,leading to short circuit.Poor wettability with electrolyte,etc.Therefore,the development of membranes materials with good thermal stability,mechanical properties and electrolyte wettability is an important way to achieve high performance of lithium batteries.In this paper,MOFs and polymer composite lithium batteries membranes and gel electrolyte were prepared by electrospinning technology.By analyzing the composition and structure of the membrane material prepared,the physical properties of the membrane and other aspects were adjusted,which significantly improved the electrochemical performance and safety performance of lithium battery at high magnification.The specific content is as follows:(1)In this work,zeolite imidazole framework(ZIF-8)was introduced into polyacrylonitrile(PAN)to prepare ZIF-8/PAN fiber composite membranes with nanofiber structure by electrospinning.Compared with commercial separator,ZIF-8/PAN fiber composite membranes showed good porosity and thermal stability,rich network structure and good electrolyte wettability improved lithium-ion transport.In addition,ZIF-8 nanoparticles with topological framework structure can effectively inhibit the growth of lithium dendrite.The results show that,Li/Li symmetric cells assembled with ZIF-8/PAN fiber composite films show a lower polarization voltage.The excellent ion transport capacity greatly improves the fast charge discharge performance of Li Fe PO₄-ZIF-8/PAN-Li batteries(stable capacity of 104 m Ah g^-1 at a current density of 5 C)and good cycle durability(capacity decline of only 0.005%after2000 cycles at a current density of 5 C).This work provides new prospects for the development of high-performance lithium-ion batteries.(2)In this work,PVDF-HFP/PEO was used as gel polymer electrolyte substrate material and UIO-66 was added as inorganic filler,the PVDF-HFP/PEO/UIO-66 composite gel polymer electrolyte with good flame retardant properties was prepared by electrospinning.Compared with commercial separators,PVDF-HFP/PEO/UIO-66 gel electrolyte encapsulated liquid electrolyte in PVDF-HFP matrix,which greatly improved the safety of lithium batteries.The results showed that the electrochemical window(4.6V)and the cycling stability(up to 146.3m A g^-1 at 1 C)were significantly improved by the addition of activated UIO-66.Moreover,the metal active site in UIO-66 greatly restricted the movement of lithium anion and increased Li⁺transference number.In addition,the gel electrolyte can act as a physical barrier to inhibit the growth of lithium dendrites and stabilize the deposition of lithium by homogenizing the distribution of lithium ions.This work opens up a new way for the gel electrolyte of lithium metal batteries by combining rigid and flexible design ideas,which is expected to be widely used in the development of high-performance electrolyte of other porous materials.