Jian-Ging Chen

Synthesis of non-stoichiometric lithium nickel cobalt oxides and their structural and electrochemical characterization

Non-stoichiometric phases of lithium nickel cobalt oxides were synthesized by a sol–gel method using oxalic acid as a chelating agent. The structural properties have been examined using X-ray diffraction techniques. Electrochemical coin cell studies showed materials with excess lithium stoichiometry had interesting properties of improved capacity and cyclability. Of all the compositions with excess lithium stoichiometry, Li1.1Ni0.8Co0.2O2, showed better electrochemical characteristics with a first cycle discharge capacity of 182 mAh/g and a 10th cycle of 172 mAh/g than the ideal stoichiometry LiNi0.8Co0.2O2. The structural and electrochemical properties of LixNi0.8Co0.2O2 with x=1.00, 1.05, 1.10 and 1.15 are discussed in detail.

Electrochemical performance of Sr2+-doped LiNi0.8Co0.2O2 as a cathode material for lithium batteries synthesized via a wet chemistry route using oxalic acid

Oxalic acid assisted sol–gel synthesis of Sr2+-doped LiNi0.8Co0.2O2 has been reported for the first time. Structural characterization was carried out using X-ray diffraction studies. Electrochemical studies were performed by assembling 2032 coin cells with lithium metal as an anode. The charge–discharge studies were performed galvonostatically at a 0.1 C rate from 3.0–4.2 V. Of all the doped compositions with dopant mole ratios ranging from 10−8 to 10−4, the compound with a dopant mole ratio of 10−6 showed improved capacity and cyclabilty with a first cycle discharge capacity of 173 mAh/g and 10th cycle of 167 mAh/g. The improvement in capacity has been discussed using a defect model.