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Experimental Research On Supercritical Hydrothermal Preparation Of LiMn2O4Cathode For Lithium Ion Battery

Posted on:2014-02-17Degree:MasterType:Thesis
Country:ChinaCandidate:J TangFull Text:PDF
GTID:2231330395499963Subject:Chemical Process Equipment
Abstract/Summary:PDF Full Text Request
Spine] LiMn2O4has become one of the most promising alternative materials in commercial application. In comparison with the conventional LiCoO2positive electrode, it shows many favorable attributes including good capacity, high-energy density, especially, low cost and low toxicity. So searching for good preparation methods is very significant. But most of the conventional methods require high temperature, or a complicated process. While, the supercritical hydrothermal synthesis can shorten the reaction time and energy consumption because of the beneficial properties of supercritical water, so it provides a new way for the industrialization of the LiMn2O4material by supercritical hydrothermal synthesis.This paper describes the preparation of sub-micron LiMn2O4by supercritical hydrothermal synthesis method. It was investigated that the effects of hydrothermal reaction parameters (reaction pressure, temperature, time and the pH) and calcining process parameters (calcining time and calcining temperature) on the structure, morphology and electrochemical performance of the material.The electrochemical performance of sub-micro LiMn2O4synthesised under optimal experiment condition was evaluated, the results showed that it could reach a reversible specific capacities of123.6mAh/g at0.1C and123.3mAh/g at1C, the capacity retention was90.4%after50cycles at1C. At high rates of up to50C, the discharge capacity could reach92.0mAh/g, the resulting powders exhibited good cycle performance and rate capability.In order to improve the problem of capacity decay of the lithium manganese oxide, the compound LiMxMn2-xO4(M=Al, Co and Fe, x=0.05,0.1,0.2,0.3) was synthetized under the optimum condition for LiMn2O4. The doping amount and the types of doped atom were respectively investigated. The spinel structure of LiMn2O4could be stabilized through partial substitution of manganese by other metals in LiMn2O4, it was a versatile method to improve cycle performance of the LiMn2O4spinel in the problems such as the Jahn-Teller’s distortion and the Mn dissolution during lithium ion intercalation/deintercalation. Among substituted manganese spinel cathodes, the Co doped lithium manganese oxides LiCo0.05Mn1.95O4showed the best electrochemical performance among the compounds. The results showed that the first discharge capacity could reach to111.8mAh/g at0.1C, after200cycles the capacity was97.4mAh/g at1C and87.2%of the capacity was maintained. The cycle performance was obviously improved.
Keywords/Search Tags:Lithium Ion Battery, Supercriticall Water, Cathode Material, LiMn2O4, Metal-substituted Manganese Spinels
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