Design Of Porous Polymer Based On Pillar[5]Quinone Structure And The Lithium Storage Performance

Lithium-ion batteries are widely utilized in electronic gadgets,but,their inorganic cathode materials still have certain drawbacks,including low theoretical capacity,environmental degradation,and high energy requirements during manufacturing.As a result,the exploitation of new electrode materials with large theoretical capacities and no pollution has emerged as a popular area of study in the field of energy storage.Because of their abundant sources,flexible structural designability,high theoretical capacity,and several other advantages,organic materials are regarded as the most promising electrode materials in the upcoming generation.The theoretical capacity of p-Benzoquinone（BQ）,which has two carbonyl discharge functional groups,is up to 496 m Ah g^-1.However,BQ has high solubility and volatility,which leads to the rapid decline of its capacity during the cycle.Five BQ and methylene units made up pillar[5]quinone（P5Q）.All the 10 carbonyl functional groups in the structure can be used as active sites for lithium storage.Compared with BQ,the performance of P5Q has been improved to a certain extent,but it still has the problem of dissolution.In this paper,using the principle of“small to large”,P5Q was polymerized to synthesize a porous polymer,Poly Pillar[5]quinone（PP5Q）.Its larger molecular weight further inhibited the dissolution and improved the cycle stability of the battery.（1）A porous polymer PP5Q with P5Q as the structural unit was designed and synthesized.PP5Q was obtained from 1,4-dimethoxy-benzene by polycondensation,Fourier alkylation,and oxidation reaction.PP5Q polymer is basically insoluble in traditional organic electrolyte.As the cathode material of lithium-ion battery,its theoretical capacity is 446 m Ah g^-1,which is equal to that of P5Q cathode.（2）In the electrolyte of 1 M bistrifluoromethanesulfonimide lithium salt-tetraethylene glycol dimethyl ether（Li TFSI-TEGDME）,the cyclic performance of BQ,P5Q,and PP5Q was compared.At the current density of 100 m A g^-1,the initial discharge capacity of PP5Q is 350 m Ah g^-1,and after 100 cycles,the discharge capacity is 170 m Ah g^-1,which is superior to the cycle performance of BQ(8 m Ah g^-1)and P5Q(107 m Ah g^-1)under the same conditions.Meanwhile,the rate performance of the PP5Q cathode is also higher than that of P5Q cathode.（3）PP5Q showed better electrochemical performance with high concentration electrolyte,especially in 4 M Li TFSI-TEGDME.Under the current density of 100 m A g^-1,after 100 cycles,the discharge capacity is 240 m Ah g^-1,even in 300 m A g^-1,after 2000cycles,it can still maintain the discharge capacity of 137 m Ah g^-1.In addition,in the rate performance test,the reversible discharge capacity can reach more than 150 m Ah g^-1 when the current density is as high as 1000 mA g^-1.