Xiaohua Xie

Al2O3/poly(ethylene terephthalate) composite separator for high-safety lithium-ion batteries

Separators have garnered substantial attention from researchers and developers in regard to their crucial role in the safety of lithium-ion batteries. In this study, a composite separator was prepared by coating cubic Al2O3 nanoparticles on non-woven poly(ethylene terephthalate) (PET) via a simple dip-coating process. The basic properties of the Al2O3-coated PET non-woven composite separator were characterized by scanning electron microscopy and other specific measurements in respect to its morphology, porosity, electrolyte wettability, and thermal shrinkage as well as its application in lithium-ion batteries. We found that the composite separator has outstanding thermostability, which may improve battery safety. Additionally, by comparison against the commercial Celgard 2500 separator, the proposed composite separator exhibits higher porosity, superior electrolyte wettability, and higher ionic conductivity. More importantly, the lithium-ion battery assembled with this composite separator shows better electrochemical performance (e.g., cycling and discharge C-rate capability) compared to that with the Celgard 2500 separator. The results of this study represent a simple approach to preparing high-performance separators that can be used to enhance the safety of lithium-ion batteries.

The effects of Li2CO3 particle size on the properties of lithium titanate as anode material for lithium-ion batteries

Spinel structured Li4Ti5O12 was synthesized by a solid-state method using TiO2 and Li2CO3 as starting materials. High-energy ball milling was used to obtain the Li2CO3 samples with different particle size. Then, the effects of Li2CO3 particle size on the structure, morphology, and electrochemical performance of Li4Ti5O12 samples were investigated in detail. The samples were characterized by TG/DTA analysis, X-ray diffraction, scanning electron microscopy and electrochemical tests, respectively. The results indicate that fine Li2CO3 particles will promote the interfacial reaction between Li2CO3 and TiO2 in solid-state reaction. The crystallinity and particle size of Li4Ti5O12 depend on the particle size of Li2CO3. Electrochemical tests show that Li4Ti5O12 samples synthesized by fine Li2CO3 particles exhibit better rate capacity and cycle performance.

Composition, structure, and performance of Ni-based cathodes in lithium ion batteries

With the rapid development of electric vehicles, Ni-based cathodes attract increasing attention as used in power batteries due to their high capacity and low cost. However, Ni-based cathodes are faced with several problems, such as Li/Ni disorder, cycle capacity degrading, poor storage in air, and thermal instability. This review carefully compared the structure difference between LiNiO2 and LiCoO2 and concluded that the electronic structure of Ni3+ determined the instability of LiNiO2. The degrading mechanism during long cycle was discussed in the second part and it could be attributed to the surface properties. Moisture sensitive severely restricts the application of Ni-based cathodes due to the gelation in slurry making and gas released in batteries. Some possible mechanisms proposed by previous researchers were reviewed in the third part and a new interpretation on the basis of diffusion was also suggested. Lastly, the nature of thermal instability of Ni-based cathodes was presented.