Study On The Novle Electrode Materials For Lithium-Ion Batteries

Science the high operating voltage，high energy density，large eapacity and long cycle life of therechargeable lithium-ion batteries, they are much investigated and widely used. In this dissertation, wefocused on the research of the positive and negative electrodes for lithium-ion batteries. Firstly, thehydrate precursor Ni_0.5Co_0.2Mn_0.3（OH）₂was prepared via a co-precipitation method using theammonia-free complexing agents. Secondly, the cathode material was calcined by the mixture ofvarious Li salts and precursor. Besides, in order to improve the cycling performance of thetransition-metal oxide ZnO as anode materials for lithium-ion batteries, the coating modification wasadopted by the wet-chemical process. The main results are summarized as follows:1) The effect of the calcination on the physical and electrochemical properties of cathodematerial LiNi_0.5Co_0.2Mn_0.3O₂had been studied. It is found that the suitable Li source is Li2CO3, andafter mixing the precursor and Li2CO3in a stoichiometric amount of1:1.05, the final product calcinedat850℃for12hours exhibits the optimal layer-structure, high rate capabilities and cycling stability.2) The precursors Ni_0.5Co_0.2Mn_0.3（OH）₂were prepared by co-precipitation method using variouscomplexing agent. The results show that the optimal condition for the preparation of the precursor isthe molar ratio （R=2:3） of the complexing agent C₃H₆O₃to total metal ions at70℃, and the productshows the highest crystallinity and specific surface area, and tap density.3) The effect of the coprecipitation temperature and complexing agent concentration on the phasestructure and electrochemical properties of cathode material LiNi_0.5Co_0.2Mn_0.3O₂had been studied. Itis found that he final cathode material exhibits the optimal layer-structure, high first dischargecapacity and high cycling stability when the coprecipitation temperature is70℃andn（C₃H₆O₃）:n(Ni²⁺+Co²⁺+Mn²⁺)=2:3.4) The influence of coating modification on the negative electrode material ZnO has been alsostudied. ZnO/C composite microspheres were prepared by calcining the Zn（NO₃）₂/RF gel in argonatmosphere. compared with common ZnO, it exhibits high cycling stability. The carbon microspheresin the composite have advantages of buffering the volume change, retraining the particles’ aggregationand enhancing the conductivity.