Polymorph of LiAlP2O7: Combined Computational, Synthetic, Crystallographic, and Ionic Conductivity Study (original) (raw)

Unraveling the doping mechanisms in lithium iron phosphate

Energy Materials, 2022

As a result of the extensive research and application of LiFePO 4 (LFP) in the past > 20 years, there is now a relatively in-depth understanding of its structural stability, phase transition mechanism and electrochemical properties. However, the difficulties faced by further improving the performance of LFP due to its intrinsic low electronic and ionic conductivity have not yet been effectively solved. In order to unlock the effect of transition metal doping on the physicochemical properties of LFP, we establish doping models for all 3d, 4d and 5d transition metals in LFP and compare and analyze their structural properties, band gaps, formation energies, elastic properties, anisotropies and lithiation/delithiation voltages using ab-initio computational screening. According to our screening results, the V-, Mn-, Ni-, Rh-and Os-doped LFP structures have excellent electrochemical properties and can be used as high-performance cathode materials for Li-ion batteries.

Structural and mechanistic insights into fast lithium-ion conduction in Li4SiO4-Li3PO4 solid electrolytes

Journal of the American Chemical Society, 2015

Solid electrolytes that are chemically stable and have a high ionic conductivity would dramatically enhance the safety and operating lifespan of rechargeable lithium batteries. Here, we apply a multi-technique approach to the Li-ion conducting system (1-z)Li4SiO4-(z)Li3PO4 with the aim of developing a solid electrolyte with enhanced ionic conduc-tivity. Previously unidentified superstructure and immiscibility features in high purity samples are characterized by X-ray and neutron diffraction across a range of compositions (z = 0.0 to 1.0). Ionic conductivities from AC impedance meas-urements and large-scale molecular dynamics (MD) simulations are in good agreement, showing very low values in the parent phases (Li4SiO4 and Li3PO4), but orders of magnitude higher conductivities (10-3 S/cm at 573 K) in the mixed compositions. The MD simulations reveal new mechanistic insights in the mixed Si/P compositions in which Li ion con-duction occurs through 3D pathways and a cooperative intersti...