Hou Xianhua

First-principles study of interphase Ni3Sn in Sn-Ni alloy for anode of lithium ion battery

This paper investigates the mechanism of Li insertion into interphase Ni3Sn in Ni—Sn alloy for the anode of lithium ion battery by means of the first-principles plane-wave pseudopotential. Compared with other phases, it is found that the Ni3Sn has larger relative expansion ratio and lower electrochemical potential, with its specific plateaus voltage around 0.3 eV when lithium atoms are filled in all octahedral interstitial sites, and the relative expansion ratio increasing dramatically when the lithiated phase transits from octahedral interstitial sites to tetrahedral interstitial sites. So this phase is a devastating phase for whole alloy electrode materials.

The Roles of Intermediate Phases of Li-Si Alloy as Anode Materials for Lithium-Ion Batteries

Abstract An ab initio method of the first-principles plane-wave pseudopotentials based on the density functional theory has been used to calculate the physical character and electrochemical performance of various alloy phases in Li-Si alloy. The results show that besides the growth of solid electrolyte interphase (SEI), the formation of Li 12 Si 7 alloy phase also partly leads to the initial irreversible capacity loss. In addition, the pure silicon thin film electrode was prepared by the radio frequency (RF) magnetic sputtering on copper foil collector as anode materials. The structural and electrochemical characteristics of Li-Si alloy were examined using X-ray diffraction (XRD), cyclic voltammogram (CV) and repeatedly constant current charge/discharge (CC). The results show that the first irreversible capacity loss is very large and amorphous structure can accommodate the large volume expansions and improve cyclic performance.

One-pot Synthesis of Nano-NiFe 2 O 4 Pinning on the Surface of the Graphite Composite as Superior Anodes for Li-ion Batteries

Abstract Nickel ferrite and related materials have recently received considerable attention as potential anode in lithium-ion batteries for their high theoretical specific capacities. To overcome low intrinsic electronic conductivity and large volume expansion during the Li insertion/extraction process, in this work, nano-NiFe2O4 pinning on the surface of the graphite composite was prepared by a hydrothermal method. As the superior anode material, the as-obtained nano-NiFe2O4/graphite composite demonstrates high capacity and excellent cycle stability. An initial specific discharge capacity of approximate 1478 mAh·g−1 and a reversible specific capacity of approximate 1109 mAh·g−1 after 50 cycles at a current density of 100 mA·g−1 are reached. When the charging current is increased to 1000 mA·g−1, it also delivers a charge capacity of 750 mAh·g−1. The excellent performances are attributed to the special structure of NiFe2O4 nanoparticles pinning on the surface of the graphite, especially the enhanced electronic conductivity and area specific capacitance during the cycling process.

First Principles Studies on the Electronics Structures of (Li0.75Na0.25)(Fe0.75Mn0.25)PO4 Cathode Materials

The effect of the Li-site, Fe-site and co-doping in LiFePO4 on the electronic properties and local structural stability has been calculated by first principle plane-wave pseudopotential method. Our calculation shows that Li-site doped (Li0.75Na0.25)FePO4 exhibit better electronic conductivity than Fe-site doped Li(Fe0.75Mn0.25)PO4 cathode material, the local structural stability is reverse. But the Li-site and Fe-site co-doped (Li0.75Na0.25)(Fe0.75Mn0.25)PO4 possesses double optimization, which is probably ascribed to the interaction between Na-2p electron states and Li-s electron states. Meanwhile, large charges are transferred from the other atoms to lithium atoms in the co-doping LiFePO4 materials based on difference of charge density, this will result in the improvement of intrinsic electronic conductivity.