Synthesis And Properties Of Carboxylic Acid Salt Organic-inorganic Polymers As Negative Materials For Li-ion Batteries

Since organic-inorganic polymers are easily synthesized and controllablestructure, a large number of optoelectronic organic-inorganic hybrid crystallinematerials have been synthesized in recent years. However, little works has beenconcentrated on designing organic-inorganic hybrid as a electrode material forlithium-ion battery. In this thesis, the carboxylic acid salt polymers weredesigned and synthesized based on the idea of molecule design and the theory ofelectrochemical reaction, and their structures and electrochemical propertieswere also studied. The main results were as following:（1） The terephthalate lithium （tpaLi₂） coordination polymer as a negativematerial was synthesized by solvothermal method. The results showed tpaLi₂was a3D coordination polymer, the size of grain is about7μm-8μm. Theinitial charge and discharge capacities of the sample were98mAh·g^-1and180mAh·g^-1, respectively. The charge and discharge capacities remain at67mAh·g^-1and68mAh·g^-1after40cycles, respectively. The impact on the performance of synthesis methods was analyzed, and the way of improving the electrochemicalproperties was put forward.（2） Trimesic lithium polymer was synthesized by different methods, and theinfluence of synthetic route on electrochemical properties was analyzed. Whenethanol solution of LiOH·H₂O was added in ethanol solution of Trimesic acid,the sample morphology is almost characterized by a sheet shape （the thicknessof those materials range from0.5μm to1μm）. After90cycles, the charge anddischarge capacities of the compound were258mAh·g^-1and264mAh·g^-1.However, when Trimesic acid was added in ethanol solution of LiOH·H₂O, thesynthetic sample was single small pieces. The thickness of those materials isabout0.2um. After50cycles, the charge and discharge capacities of thecompound were58mAh·g^-1and59mAh·g^-1.and the electrochemicalperformance is poor.（3） A new coordination polymer based on2,6-pyridinedicarboxylic acid[C25H21Li6N3O14] as negative material was synthesized by solvothermal andreflux methods, respectively. The results showed C25H21Li6N3O14is a2D layerstructure crystallized in the monoclinic system, P2（1）n space group. The initial charge and discharge capacities of the compound were280mAh·g^-1and819mAh·g^-1, respectively. The charge and discharge capacities maintain at about164mAh·g^-1and160mAh·g^-1after50cycles. This work might provide a newmethod for designing new positive-electrode materials as lithium ion batteries.