Preparation Of PAN-based Three-dimensional Carbon Skeleton By Electrostatic Spinning And Its Protection For Lithium Metal Batteries

Lithium battery,as a secondary energy storage device with great development potential,has huge energy storage potential waiting for the research and development of scientific researchers.Metal lithium is the best choice of lithium secondary batteries due to its extremely high theoretical specific capacity and extremely low electrode potential.However,lithium metal has serious dendrite growth problems during battery charging and discharging,which leads to serious safety risks for lithium metal batteries.Therefore,the commercial production of lithium metal batteries faces serious challenges.Based on the above problems,this dissertation attempts to prepare PAN fiber material by electrospinning method,add ammonium fluoride/glacial acetic acid saturated solution to modify PAN,and prepare N functional group-rich PAN-based 3D fiber skeleton for the protection of metal lithium anode to achieve the purpose of inhibiting the growth of metal lithium dendrites,thereby protecting the metal lithium anode,and providing a method for the commercial production of metal lithium batteries.In this dissertation,the PAN-based 3D carbon fiber skeleton was prepared by electrospinning.The PAN fiber was modified by adding ammonium fluoride/glacial acetic acid saturated to prepare the 3D cross-linked nanofiber structure.The PAN/carbon lithium metal anode skeleton was prepared by the dipping method.The PAN-based three-dimensional carbon skeleton was characterized by various test techniques such as SEM,XRD,XPS,FTIR,and Raman.The results showed that a porous 3D nano-crosslinked structure rich in polar functional groups such as amide bonds was prepared.Using this 3D nano-crosslinked structure for battery performance testing.The best technology of battery preparation is single gasket system,and the structure of loaded fiber is treated by non ultrasonic.A PAN-based 3D carbon fiber skeleton metal lithium battery modified by NH4F/HAc saturated solution was prepared,and the optimal volume of additive of NH4F/HAc saturated solution was confirmed to be 0.05 ml through a comparative experiment.A symmetrical metal lithium battery was prepared,and the protection of the PAN-based 3D carbon fiber framework modified by NH4F/HAc saturated solution was verified to prolong the cycle number of the metal lithium battery to more than 2000 circles.Through SEM test,the deposition results of lithium metal on the modified PAN-based 3D carbon fiber framework were observed,and it was found that the 3D carbon fiber framework structure can effectively inhibit the growth of lithium dendrites.Using the comsol platform to simulate the surface current density of the rod-shaped carbon material,the carbon rod deposition model in the battery was constructed,and the deposition curve of lithium metal on the surface of the fiber was obtained.The surface deposition current density of the fiber with different porosity was simulated and analyzed.It is concluded that the large specific surface area lead to low current density of the local deposition,which explains the reason why carbon fibers inhibit the growth of lithium dendrites.