Predicting Capacity Fade in Silicon Anode-Based Li-Ion Batteries

While silicon anodes hold promise for use in lithium-ion batteries owing to their very high theoretical storage capacity and relatively low discharge potential, they possess a major problem related to their large volume expansion that occurs with battery aging. The resulting stress and strain can lead to mechanical separation of the anode from the current collector and an unstable solid electrolyte interphase (SEI), resulting in capacity fade. Since capacity loss is in part dependent on the cell materials, two different electrodes, Lithium Nickel Oxide or LiNi0.8Co0.15Al0.05O2 (NCA) and LiNi1/3Mn1/3Co1/3O2 (NMC 111), were used in combination with silicon to study capacity fade effects using simulations in COMSOL version 5.5. The results of these studies provide insight into the effects of anode particle size and electrolyte volume fraction on the behavior of silicon anode-based batteries with different positive electrodes. It was observed that the performance of a porous matrix of solid active particles of silicon anode could be improved when the active particles were 150 nm or smaller. The range of optimized values of volume fraction of the electrolyte in the silicon anode were determined to be between 0.55 and 0.40. The silicon anode behaved differently in terms of cell time with NCA and NMC. However, NMC111 gave a high relative capacity in comparison to NCA and proved to be a better working electrode for the proposed silicon anode structure.

Thermal Decomposition Study on Li2O2 for Li2NiO2 Synthesis as a Sacrificing Positive Additive of Lithium-Ion Batteries

Herein, thermal decomposition experiments of lithium peroxide (Li2O2) were performed to prepare a precursor (Li2O) for sacrificing cathode material, Li2NiO2. The Li2O2 was prepared by a hydrometallurgical reaction between LiOH·H2O and H2O2. The overall reaction during annealing was found to involve the following three steps: (1) dehydration of LiOH·H2O, (2) decomposition of Li2O2, and (3) pyrolysis of the remaining anhydrous LiOH. This stepwise reaction was elucidated by thermal gravimetric and quantitative X-ray diffraction analyses. Furthermore, over-lithiated lithium nickel oxide (Li2NiO2) using our lithium precursor was synthesized, which exhibited a larger yield of 90.9% and higher irreversible capacity of 261 to 265 mAh g−1 than the sample prepared by commercially purchased Li2O (45.6% and 177 to 185 mAh g−1, respectively) due to optimal powder preparation conditions.

VANADIUM BASED LITHIUM NICKEL ALUMINIUMOXIDE SYSTEM WITH GOOD PERFORMANCE IN LITHIUM-ION BATTERIES

LiNixV1-x-y AlyO2, are cathode materials for lithium ion batteries which have been synthesized via carbon combustion method. Lithium nickel oxide derivatives are considered by the battery manufacturers to be very promising for application in 4V lithium-ion batteries. The objective of this study is, to successfully synthesize a lithium nickel vanadium aluminum oxide cathode which can show intercalation and de-intercalation process during cyclic voltammetry testing and a discharge capacity of above 50mAh/g. LiNi1-x-yVxAlyO2were synthesized by the carbon combustion method using acetylene carbon black as a binder. X-Ray Diffraction (XRD) reveals extra peaks related to Vanadium metal when it is added into LiNiAlO2. The intensity peak of the spectrum increased when the V content is increased. Scanning Electron Microscopy (SEM) shows the grain particles become non-spherical and flakes when more vanadium substituted for nickel in the sample. Fourier Transform Infrared (FTIR) spectroscopy analysis and Energy dispersive analysis of X-Ray (EDAX) confirmed that NO3- impurities are not present and composition in samples Galvanostatic charge/discharge data obtained illustrates a discharge capacity of 80.57mAh/g LiNi0.8V0.1Al0.1O2 and an average of 80.55mAh/g for 10 cycles whereas LiNi0.6V0.3Al 0.1O2 highest discharge capacity is 80.52mAh/g and also an average of 80.53mAh/g for 10 cycles. Voltammographs of the LiNi0.8V0.1Al0.1O2, LiNi0.7V0.2Al0.1O2 and LiNi0.6V0.3Al0.1O2 materials showed good oxidation and reduction loop at 0.05mV/s and 1 mV/s scan rate.