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Preparation And Electrochemical Properties Of Dually Protected Ge@GeO2 Composites As Anode Materials For Lithium Ion Battery

Posted on:2017-03-09Degree:MasterType:Thesis
Country:ChinaCandidate:R XuFull Text:PDF
GTID:2271330503468967Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
With the increase of per capita energy usage, cleaner and longer-lasting energy storage devices are of the utmost importance in the current and future technology. The requirements for next generation batteries are particularly demanded, including larger capacity, higher safety, faster recharge and lower cost. Germanium-based materials are the most promising candidates for next-generation energy storage devices owing to their unique chemical and physical properties. In this paper, the germanium-based materials with enhanced electrochemical performance were studied.Porous germanium is prepared by magnesiothermic reduction reaction using GeO2 as the raw material. The active material is dually protected in order to improve the electrochemical performance. Germanium is covered by carbon layer via hydrothermal reaction. Subsequently, obtained Ge@C composites were mixtured with graphene oxide solution. The rationally designed dual-protection for Ge@GeO2 composites, i.e. encapsulation of amorphous carbon and cover of graphene nanosheets, has been successful formed by heat treatment. As a consequence, the designed composite electrode delivered a remarkable capacity of 729 mAh g-1 at a current density of 800 mA g-1 after 50 cycles at low temperature of 10℃ with low capacity fading of 0.12% per cycle and excellent rate capability. Of special note is that high thermosensitivity of electrochemical performance of composites has been observed from cycling performances at different temperatures.Composites fabricated by the different preparation conditions exhibit different electrochemical performances. The influence factors of composite performance are investigated, including different solvent(distilled water and ethanol), different qualities of graphite oxide(30mg, 60 mg and 80mg) and glucose(1g, 2g and 3g). In summary, the composite prepared by the use of ethanol, 60 mg graphite oxide and 1g glucose present the remarkable electrochemical performance. A reversible capacity of 717 mAh g-1 after 50 cycles at 800 mA g-1 and a stable capacity of 540 mAh g-1 at high current density of 1600 mA g-1 are measured for the composites.
Keywords/Search Tags:Graphene, lithium-ion battery, Ge@GeO2, anode material, dual-protection
PDF Full Text Request
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