Preparation And Study Of Polyether Amine Polyurea Composite Electrolyte

Lithium-ion batteries(LIBs)have brought astonishing advancements and transformations in portable electronics and more recently electric vehicles during the past several decades.However,there are some serious safety issues such as short circuits,leakage and combustion even explosions deriving from the dendrite growth in liquid electrolytes used widely in LIBs.Meanwhile,motivated by storage systems with high energy density,the use of highly reactive lithium metal also promotes the search for new electrolytes.Consequently,the research on solid electrolytes has become a hot spot in the industry and academia.In this paper,a series of solid polymer electrolytes are prepared and doped with nanoparticles to construct composite polymer electrolytes.At the same time,a novel method of anode in-situ polymerization and cathode-supported polymer electrolyte is used to obtain high ionic conductivity and excellent electrode/electrolyte interface.The main research contents of the paper are as follows.(1)The solid polymer electrolyte(SPE)was designed and synthesized from diethyl maleate,polyether amine,and isophorone diisocyanate(IPDI)and its trimer(Tri-IPDI),and lithium trifluoromethanesulfonimide(Li TFSI)as a lithium source.The effects of the IPDI&Tri-IPDI ratio and lithium salt dosage on the performance of SPE were systematically investigated.The FTIR test results show that the polymer electrolytes have reacted completely.At the same time,with the addition of lithium salt,the amine peak of the SPE has a regular shift.Under the SEM observation,the SPE film presents a corrugated structure with no holes or gaps,indicating that the lithium salt has been mixed completely.In addition,the EDS test shows that the characteristic elements S and F in the lithium salt are uniformly distributed in the SPE and exhibits good compatibility.The XRD results show that the crystallinity of different cross-linking degrees is not completely the same,and when the cross-linking degree is small,there are more crystalline parts in the system.DSC results show that the T_g of SPE is about-50°C,and a lower T_g can enhance the movement of the chain segment,which is beneficial to the improvement of ionic conductivity.The reaction process of the system is monitored by the rheological test.The study finds that the higher the amount of trimer IPDI in the system,the faster the storage modulus curve and loss modulus curve reach the cross time.At the same time,the storage modulus is also higher after 9 hours of reaction.Besides,the frequency sweep mode is used to test the SPE film,and it is found that the SPE film exhibits viscoelasticity and typical cross-linking characteristics.The result shows that when the ratio of IPDI to Tri-IPDI is 2:1 and the mass fraction of lithium salt is 7%,the room temperature ionic conductivity is the highest in the ionic conductivity test.Meanwhile,the improvement effect of in-situ polymerization of lithium sheets on its impedance is explored.The impedance is reduced from 17000 ohm to4200 ohms,and in the electrochemical cycle test,the charge discharge capacity of nearly110 m Ah/g is nearly still maintained after 30 charging and discharging cycles.(2)Based on the above,the composite solid polymer electrolyte(CSPE)was constructed by adding a different mass fraction of nanoparticles.The FTIR test results show that the polymer electrolytes have reacted completely.In addition,the XRD results show the effect on the crystallinity of nano-alumina after adding,that is,the addition of nanoparticles within a certain amount is beneficial to increase the amorphous part of the system,but due to the agglomeration effect of nanoparticles,with the amount of nanoparticles increasing,the crystallinity of the system has increased.DSC test results find that the Tg of CSPE with nanoparticles increase to-40°C.Besides,the effects of nanoparticles on the thermal stability,ionic conductivity,and electrochemical stability window of the electrolyte were investigated.The thermal decomposition temperature is increased by 30?40?,and the ionic conductivity of CSPE@1 is higher an order of magnitude and nearly doubled than that of the control group PEO and SPE@A7,respectively,and the electrochemical stability window is increased to 4.5 V.The composite polymer electrolyte of CSPE@1 was selected to prepare lithium symmetrical batteries and the stability of the lithium electrode interface is tracked.It is found that the impedance does not change significantly within 9 days Besides,an electrode-supported polymer electrolyte membrane with tight interface was prepared.The SEM and EDS tests show that the composite polymer electrolyte and the positive electrode material are closely contact to form a whole,and the polymer electrolyte realizes full coverage of the electrode material.The full cell with this electrode is better than that with traditional electrode in impedance test.At the same time,the battery rate cycle test is carried out,and the performance is excellent,showing a great application prospect.