Studies On The Preapration,Desodiation And Lithiation Of Sodium Sulfur/Selenium-graphite Intercalation Compounds

Li-S/Se battery is an energy storage system with great potential due to its high specific energy density,low cost and high safety.However,S/Se cathodes suffer from several problems such as low ionic and electronic conductivity,dissolution and shuttle effect of intermediate,huge volume change et al.This thesis attempts to embed sulfur or selenium with sodium into the inter-layer of graphite so as to get sodium sulfur/selenium-graphite intercalation compound(NaS/Se-GIC)which will be used to prepare novel battery cathode materials,namely sulfur/selenium-graphite intercalation compound(S/Se-GIC)by a electrochemical desodiation process.As a preliminary study on the preparation of S/Se-GIC,Two main works have been done as following:(1)Firstly,NaS-GIC was prepared by blending-heating method.Results show that NaS-GIC has a highly ordered layered structure and high crystallinity.The distribution of S,Na and C elements in NaS-GIC is homogeneous with a stoichiometric ratio of Na C_5.1S_0.2.TG tests exhibit NaS-GIC begins to break down at about 150 ^oC in pure oxygen atmosphere,indicating the pretty good thermostability of NaS-GIC.Lithium batteries were assembled by using NaS-GIC as the cathode,metal Li as the anode.Then,galvanostatic charge-discharge was conducted in order to remove Na⁺in NaS-GIC and intercalate Li⁺.Results show a considerable part of Na⁺ions de-intercalates and the desodiated NaS-GIC exhibits good lithium storage peroformance.(2)Secondly,NaSe-GIC was fabricated with the same method as NaS-GIC,NaSe-GIC has a highly ordered layered structure and high crystallinity.The distribution of Se,Na and C elements in NaSe-GIC is also homogeneous with a stoichiometric ratio of Na C_4.4Se_0.15.NaSe-GIC begins to break down at about 200 ^oC under oxygen atmosphere.Lithium batteries were also assembled by using NaSe-GIC as the cathode,metal Li as the anode.Then,galvanostatic charge-discharge was conducted in order to remove Na⁺in NaSe-GIC and intercalate Li⁺.Results show a considerable part of Na⁺ions de-intercalates and the desodiated NaSe-GIC exhibits good lithium storage peroformance.