Research Of Lithium Manganese Cathode Materials With Long Cycle Life

In recent years due to environmental pollution and resources shortage, HEV/EV triggered heated debate. And it has caused the attention to automotive power battery. In order to in order to satisfy the universal energy vehicles, cost and performance stability of lithium-ion batteries made new requirements. Lithium manganese oxide spinel with abundant, inexpensive, safe and stable, no pollution, is one of the green power battery cathode material suitable recognized, but under high temperature conditions exist Jahn-Teller distortion effect caused cycle capacity attenuation problems have hindered its large-scale application. Solution methods include changing synthesis method, coating modification, doping, etc. The main modification methods for t were doped ions.This paper focuses on spinel lithium manganese doped with a metal cation, in order to improve the cycle performance.Using High-temperature solid-phase method and sol-gel method to prepare lithium manganese oxide materials, XRD studies show that the samples are prepared by two methods are both spinel structure. The sample particles prepared by high-temperature solid-phase method are larger, morphology rules, uniform particle size, and excellent dispersion by SEM analysis. And the electrical properties of the test sample in a high temperature solid phase method show a higher discharge capacity, more stable discharge platform, better cycle performance.The spinel LiMn2O4 samples obtained through high-temperature solid-phase synthesis method with Li OH and Mn(CH3COO) 2 as raw materials, XRD and SEM research indicated that Lithium salt volatilized at high temperature calcinations phenomenon. So the ratio of the lithium manganese should higher than the stoichiometric ratio. Sample synthesis with Li / 2Mn = 1.15 the first reversible capacity of the sample is 118.9 mAh / g, and the capacity maintains 97.6% after 50 cycle.Samples obtained by high-temperature solid-phase synthesis doped with Co, Cr, Al elements with LiOH and Mn(CH3COO) 2 as raw materials. XRD shows that LiMn2O4 materials doped with one or some kinds of Co, Cr or Al, structure does not change, all the structures are typical spinel phase, and there are no impurity phases. The electrochemical testing study shows that the reversible capacity of the samples doped with single element of Co, Cr and Al, regardless the doping ratio; reduced.But the cycle performance can be improved.LiMn2O4 samples doped with Co, Cr and Al multi-element.XRD shows the structure unchanged. DSC analysis indicated the element of Al could improve the thermal stability of LiMn2O4; Cr element could improve the high-rate discharge capacity of the material; Co, Cr, Al cooperation can significantly improve the cycle performance of the material, especially to high-temperature cycle performance. Sample-2(LiCo0.1Cr0.05Al0.1Mn1.75O4) shows excellent cycle performance, the capacity maintains 89.9% after 500 cycles at room temperature @1C.and the capacity still maintains 78.4% after 500 cycles at temperature 55 ?@1C.