Vincent Gariépy

Hollow melon-seed-shaped lithium iron phosphate micro- and sub-micrometer plates for lithium-ion batteries.

Melon-seed-shaped LiFePO4 hollow micro- and sub-micrometer plates have been synthesized via a polyol-assisted hydrothermal method. The as-prepared LiFePO4 hollow materials were new with regard to their single-crystalline shells with large ac surfaces. Based on the detailed analysis of time-dependent studies, a possible growth mechanism was proposed involving nucleation, anisotropic growth, selective etching, and reversed recrystallization. The effects of polyol concentration, reaction temperature, and feeding sequence of precursors on the growth of LiFePO4 materials were investigated. The electrochemical properties of as-prepared LiFePO4 hollow materials were examined as cathode materials.

Measuring Spatially Resolved Collective Ionic Transport on Lithium Battery Cathodes Using Atomic Force Microscopy

One of the main challenges in improving fast charging lithium-ion batteries is the development of suitable active materials for cathodes and anodes. Many materials suffer from unacceptable structural changes under high currents and/or low intrinsic conductivities. Experimental measurements are required to optimize these properties, but few techniques are able to spatially resolve ionic transport properties at small length scales. Here we demonstrate an atomic force microscope (AFM)-based technique to measure local ionic transport on LiFePO4 to correlate with the structural and compositional analysis of the same region. By comparing the measured values with density functional theory (DFT) calculations, we demonstrate that Coulomb interactions between ions give rise to a collective activation energy for ionic transport that is dominated by large phase boundary hopping barriers. We successfully measure both the collective activation energy and the smaller single-ion bulk hopping barrier and obtain excellent agreement with values obtained from our DFT calculations.

High-Capacity and Long-Cycle Life Aqueous Rechargeable Lithium-Ion Battery with the FePO4 Anode

Aqueous lithium-ion batteries are emerging as strong candidates for a great variety of energy storage applications because of their low cost, high-rate capability, and high safety. Exciting progress has been made in the search for anode materials with high capacity, low toxicity, and high conductivity; yet, most of the anode materials, because of their low equilibrium voltages, facilitate hydrogen evolution. Here, we show the application of olivine FePO4 and amorphous FePO4·2H2O as anode materials for aqueous lithium-ion batteries. Their capacities reached 163 and 82 mA h/g at a current rate of 0.2 C, respectively. The full cell with an amorphous FePO4·2H2O anode maintained 92% capacity after 500 cycles at a current rate of 0.2 C. The acidic aqueous electrolyte in the full cells prevented cathodic oxygen evolution, while the higher equilibrium voltage of FePO4 avoided hydrogen evolution as well, making them highly stable. A combination of in situ X-ray diffraction analyses and computational studies revealed that olivine FePO4 still has the biphase reaction in the aqueous electrolyte and that the intercalation pathways in FePO4·2H2O form a 2-D mesh. The low cost, high safety, and outstanding electrochemical performance make the full cells with olivine or amorphous hydrated FePO4 anodes commercially viable configurations for aqueous lithium-ion batteries.

Pure Phase Disordered LiMn1.45Cr0.1Ni0.45O4 by a Post-Annealing Treatment

A new post-annealing treatment at ca. 600 °C was used to modify the oxygen deficiency during the synthesis of the spinel LiMn1.45Cr0.1Ni0.45O4 cathode for Li-ion batteries. It is an effective way to eliminate the impurity phase without changing the crystal chemistry. Small amount of substituting Cr leads to better rate performance and cyclability at room temperature, compared to commercial LiMn1.5Ni0.5O4. LiMn1.45Cr0.1Ni0.45O4 delivered a reversible capacity of 104 mAh g-1 at 1C rate. After 125 cycles, about 99% of reversible capacity was retained for the LiMn1.45Cr0.1Ni0.45O4 in contrast with 6% capacity loss for the commercial LiMn1.5Ni0.5O4. Electrochemical impedance spectroscopy measurements revealed that the LiMn1.45Cr0.1Ni0.45O4 had a smaller surface resistance, which may be due to the segregation of Ni from the surface to the bulk.

High Capacity and High Efficiency Maple Tree-Biomass-Derived Hard Carbon as an Anode Material for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are in the spotlight because of their potential use in large-scale energy storage devices due to the abundance and low cost of sodium-based materials. There are many SIB cathode materials under investigation but only a few candidate materials such as carbon, oxides and alloys were proposed as anodes. Among these anode materials, hard carbon shows promising performances with low operating potential and relatively high specific capacity. Unfortunately, its low initial coulombic efficiency and high cost limit its commercial applications. In this study, low-cost maple tree-biomass-derived hard carbon is tested as the anode for sodium-ion batteries. The capacity of hard carbon prepared at 1400 °C (HC-1400) reaches 337 mAh/g at 0.1 C. The initial coulombic efficiency is up to 88.03% in Sodium trifluoromethanesulfonimide (NaTFSI)/Ethylene carbonate (EC): Diethyl carbonate (DEC) electrolyte. The capacity was maintained at 92.3% after 100 cycles at 0.5 C rates. The in situ X-ray diffraction (XRD) analysis showed that no peak shift occurred during charge/discharge, supporting a finding of no sodium ion intercalates in the nano-graphite layer. Its low cost, high capacity and high coulombic efficiency indicate that hard carbon is a promising anode material for sodium-ion batteries.

Application of operando X-ray diffraction and Raman spectroscopies in elucidating the behavior of cathode in lithium-ion batteries

With the advances in characterization techniques, various operando/in-situ methods were applied in studying rechargeable batteries in order to improve the electrochemical properties of electrode materials, prolonging the battery life and developing new battery materials. In the present review, we focus on the characterization of electrode materials with operando/in-situ X-ray diffraction and Raman spectroscopies. By correlating the results obtained via these two techniques in different electrode chemistry: a) intercalation materials, such as layered metal oxides and b) conversion materials, such as elemental sulfur. We demonstrate the importance of using operando/in-situ techniques in examining the microstructural changes of the electrodes under various operating conditions, in both macro and micro-scales. These techniques also reveal the working and the degradation mechanisms of the electrodes and the possible side reactions involved. The comprehension of these mechanisms is fundamental for ameliorating the electrode materials, enhancing the battery performance and lengthening its cycling life.