![]() The Na doped material exhibited significantly higher electronicĬonductivity than its un-doped analog as evidenced by dc electronic conductivity data and AC impedance of Li cells. The discharge rate capability of the LLNMC was greatly improved at both room temperature and 50 0C with the Na doping. % Na doped material, formulated asĠ.3Li 2MnO 3.0.7Li 0.97Na 0.03Mn 0.33Ni 0.33Co 0.33O 2, was compared to its counterpart without Na doping. Metal oxides appears to be a holistic strategy for improving the structural robustness and rate capabilities of these high capacity cathode materials for Li-ion batteries.Ĭhapter 3 examines the effect of alkali ion doping (Na +) into the cathode material of the composition 0.3Li 2MnO 3.0.7LiMn 0.33Ni 0.33Co0.33O 2 (LLNMC). Removing the Mn from the LiMO 2 segment of lithium rich layered Electrochemical cycling data from Li cells further revealed that the absence of Mn in the LiMO 2 segment significantly improves the rate capabilities of LLNC with good capacity maintenance during long term cycling. The XAS data along with electrochemical results revealed that Mn atoms are not present in the LiMO 2 structural segment in LLNC. Using X-ray absorption (XAS) spectroscopy we elucidated the oxidation states of the K edges of Ni and Mn in the two materials with respect to different charge andĭischarge states. X-ray diffraction (XRD) patterns revealed that both compounds, synthesized as approximately 300 nm crystals, have identical super lattice ordering attributed to Li 2MnO 3 existence. Resists the layered to spinel structural transformation under conditions in which LLNMC does. ![]() In LLNC, the removal of Mn from the LiMO 2 (M=transition metal) segment allowed us to determine the identity of the manganese oxide moiety in it that triggers the layered to spinel conversion during cycling. Material in Li cells have been compared to that of 0.3Li 2MnO 3.0.7LiMn 0.33Ni 0.33Co 0.33O 2 (LLNMC). The crystal structure and electrochemistry of this new cathode active This dissertation presents an account of investigations leading to advanced materials which overcome the deficiencies of this class of highĬhapter 1 discusses the fundamental aspects of generic battery systems and elaborates on the current state of the art of rechargeable Li batteries.Ĭhapter 2 deals with the discovery of the material 0.3Li 2MnO 3.0.7LiNi 0.5Co 0.5O 2 (LLNC) that allowed us to conclude which segment of the lithium rich layered composite metal oxide is responsible for structural transformation from the layered to spinel phase during charge/discharge cycling. In order to overcome these deficiencies of LiCoO 2, Li-rich layered metal dioxides, also known as layered-layered lithiated metal oxide composite compound, formulated as xLi 2MnO 3.(1-x)LiMO 2 (M=Mn, Ni or Co), have been proposed recently. The deficiencies of LiCoO 2 include: i-) low capacity with only 0.5 mole of Li + is being reversibly used in the battery leading to 140 mAh/g discharge capacity at low to medium rates, ii-) high cost, and iii-) environmental concerns arising from the harmful physiologicalĮffects of Co metal. Current Li-ion battery technologyĮmploys lithium cobalt oxide, LiCoO 2, or one of its congeners, in which some of the Co is substituted with Ni and/or Mn as cathode active material. ![]() Large scale energy storage is an indispensable component of renewable energy sources and in this context, Li-ion batteries (LIBs), due to their high energy and power densities and long cycle life, have spurred great interest. (Committee member) Language: English Publisher: Boston, Massachusetts : Northeastern University, 2015 Copyright date: 2015 Date Accepted: April 2015 Date Awarded: May 2015 Type of resource: Text Genre: Dissertations Format: electronic Digital origin: born digital Abstract/Description: Renewable energy sources such as solar energy, wind and hydroelectric power are increasingly being developed as essential energy alternatives to alleviate the deleterious effects of greenhouse gases in the globe. Title: High energy density cathode active materials for lithium-ion batteries Creator: Ates, Mehmet Nurullah (Author) Contributor: Abraham, Kuzhikalail M. ![]()
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