Preparation Of Ti₃C₂T_x(MXene)-based Composites And Study On Their Properties

The high energy density and environment-friendly characteristics of lithium-ion batteries make them show obvious advantages in the field of new energy storage and utilization and environmental sustainability.As people aspire for a better life,the development of higher energy density rechargeable batteries has received attention.Lithium-sulfur batteries(LSB)have become the target of next-generation rechargeable battery development with their higher energy density and lower material cost.However,the shuttle effect during its charging and discharging process is one of the main problems limiting the commercialization of LSB.In this paper,Ti₃C₂Tx MXene two-dimensional materials with good mechanical properties,metal-like conductivity,chemical stability,and tunable structure are prepared by etching MAX phase by Li F/HCl solution system and applied to lithium-sulfur batteries.A crumpled nitrogen-doped porous MPF13-550 composite is synthesized through freeze-dried and high-temperature carbonized methods by polymerization of formaldehyde and pyrrole on Ti₃C₂Tx MXene surface by hydrogen bonding to form gels as precursors.The as-prepared MPF13-550 possesses a large specific surface area(179 m² g^-1)and high nitrogen doping(10.22 at.%).The multifunctional separator fabricated by coating the commercial polypropylene(PP)separator with MPF13-550(MPF13-550/PP)is applied in lithium-sulfur battery,which has the advantages of immobilizing lithium polysulfides via strong chemisorption and reactivating sulfur because of its high conductivity.Consequently,the Li-S battery with the MPF13-550/PP separator exhibits high initial discharge capacity(1235 m Ah g^-1 at 0.1 C),good rate capabilities(593 m Ah g^-1 at 2.0 C),and remarkable cycling performance(721 m Ah g^-1 at 0.2 C after 200 cycles).In order to further investigate the effect of heteroatom-doped MXene on the performance of lithium-sulfur batteries,in this paper,MPPA formed by the oxidative polymerization of aniline through hydrogen bonding interaction with phytic acid and MXene is used as a precursor,and then a N,P co-doped wavy MPPA-550 composite is synthesized by high temperature carbonization.The prepared MPPA-550 has a wavy-like surface and abundant N(4.28 at.%)and P(6.21 at.%)co-doping.The functionalized separator(MPPA-550/PP)has the advantage of immobilizing lithium polysulfide by strong chemisorption and reactivating sulfur by high electrical conductivity.As a result,the lithium-sulfur battery with MPPA-550/PP separator has a high initial discharge capacity of 736 m Ah g^-1 and good cycling performance of 500 cycles at a current density of 2.0 C.