Xueya Kang

In situ formation and rapid decomposition of Ti(BH4)3 by mechanical milling LiBH4 with TiF3

Mechanically milled 3LiBH(4)/TiF(3) mixture can rapidly release over 5 wt % hydrogen at moderate temperatures (70-90 degrees C) without undesired gas impurity. Structure analyses results show that the favorable dehydrogenation performance of the material should be associated with the in situ formation and rapid decomposition of an intermediate titanium borohydride (Ti(BH(4))(3)). These findings demonstrated a viable chemical activation approach for promoting hydrogen release from the thermodynamically stable borohydrides. Particularly, it shows the potential of transition metal borohydrides for hydrogen storage applications.

Direct formation of Na3AlH6 by mechanical milling NaH/Al with TiF3

Na3AlH6 can be directly formed by mechanical milling NaH/Al with TiF3 under hydrogen atmosphere. The hydrogenation fraction of NaH increases with increasing the milling time, and reaches up to 0.61 after 20 h milling. Thus-formed Na3AlH6 exhibits unexpected polymorphic transformation and decomposition behaviors. This, together with the unusual hydrogen storage performance of the mechanically prepared materials, provides us a suggestive perspective to probe the favorable modification of the thermodynamics of Na3AlH6 and nature of active Ti-species in Ti-doped NaAlH4

Preparation and electrochemical properties of LiMn2O4 by a rheological-phase-assisted microwave synthesis method

By using LiCO3 and MnO2, a rheological-phase-assisted microwave synthesis method has been applied in the fast preparation of spinel LiMn2O4 in order to reduce the cost of cathode materials. Comparing with the pristine LiMn2O4 obtained by the traditional solid-state reaction method, the structure and surface morphology of the samples synthesized by the rheological-phase-assisted microwave synthesis method have been investigated. The powders were used as positive materials for lithium-ion battery, whose charge/discharge properties and cycle performance have been examined in detail. As a result, the powders prepared by the rheologicalphase-assisted microwave synthesis method at 750°C are pure spinel LiMn2O4 with regular shapes and uniform distribution, which exhibit higher capacity and much better reversibility than the sample prepared by the traditional solid-state reaction.

EFFECTS OF DIFFERENT CARBON SOURCES ON PROPERTIES OF LiFePO4/C BY A CARBOTHERMAL REDUCTION METHOD

The LiFePO4/C composite was prepared by carbothermal reduction method (CTR) with FePO4 ⋅ 2H2O, Li2CO3 as starting materials, and acetylene black or polyethylene glycol (PEG; mean molecular weight of 10,000) as carbon sources. The structural and electrochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM), and charge–discharge tests. The results showed that LiFePO4/C is olivine-type phase, and the addition of carbon reduced the LiFePO4 grain size with uniform distribution. The carbon is dispersed between the grains, forming a good electronic contact. The synthesized LiFePO4 composites showed excellent electrochemical performance with initial discharge capacity of 161, 142 and 96 mAh ⋅ g-1 at 0.1 C, 1 C and 5 C, respectively and displays a robust rate capacity and stable cycling life.