Preparation and characterization of barium strontium titanate/silicon nanoporous pillar array composite thin films by a sol-gel method

Barium strontium titanate （Ba0.5Sr0.5TiO3, BST）/silicon nanoporous pillar array （Si-NPA） thin films were prepared by a spin-coating/annealing technique based on Si-NPA with micro/nano-structure. Both the isomer conversion of acetylacetone and the network structure combined by enol and Ti-alkoxide facilitate the formation of the BST sol and the subsequent crystallization. Before the perovskite BST begins to form, the intermediate phase （Ba, Sr）Ti2OsCO3 is found. The boundary between BST and Si-NPA is of clarity and little interface diffusion, disclosing that Si-NPA is an ideal template substrate in the preparation of multifunctional composite films.

Enhanced cycling stability and rate performance of Co-doped and La_(2)O_(3)-coated LiNi_(0.9)Mn_(0.1)O_(2) toward power battery

Ultra-high nickel layered oxide cathode material with high energy density is the most promising material to improve the electrochemical performance of lithium-ion batteries(LIBs).However,the poor structural stability and severe surface/interface side reactions of the material lead to poor rate performance and cyclic stability,which limits its application in practice.In this paper,the dual-modification strategy of Co doping and La_(2)O_(3) coating is used to meet the above challenges.Co doping can effectively widen layer spacing and reduce Li^(+)/Ni^(2+) mixing,and La_(2)O_(3) coating can effectively eliminate the residual alkali on the surface of active material,inhibit the thickening of cathode electrolyte interphase(CEI)film and reduce surface/interface side reactions.Therefore,the modified material(NM90-CL)with excellent electrochemical properties is achieved through the synergistic enhancement of Co doping and La_(2)O_(3) coating.Its capacity retention rate can reach 77.9%after 200 cycles at 1.0℃ and 75.7%after 200 cycles at 5.0℃.Its reversible capacity can up to 153.5 mAh·g^(–1) at 10.0℃.This dual-modification strategy will provide theoretical guidance and technical support for the synthesis of other high-performance electrode materials.

Controllable construction of yolk–shell Sn–Co@void@C and its advantages in Na-ion storage

In the family of anodes for sodium-ion batteries,alloy-type anodes possess higher theoretical specific capacity than carbon anodes. The theoretical specific capacity of metallic Sn is 847 mAh·g^(-1). However, the tinbased material undergoes a large volume expansion during the sodium-ion intercalation process, which leads to the crack and pulverization of the electrode, consequently resulting in a significant capacity loss. In this paper, a yolk–shell-structured Sn–Co@void@C composite composed of a Sn–Co alloy core, a carbon shell and void space between the core and shell is designed and synthesized.Compared with the carbon-encapsulated SnCo without void space(Sn–Co@C) and carbon-encapsulated pure Sn core shell with void space(Sn@void@C), this composite exhibits improved reversibility, cyclic performance and rate capability. This work highlights the important roles of Co in the alloy and the void space between the core and the shell. The former can not only buffer the volume expansion of Sn, but also act as an electrical conductor. The void space can further tolerate the volume expansion of the Sn–Co core. Owing to this unique microstructure, the Sn–Co@void@C composite shows an initial reversible capacity of 591.4 mAh·g^(-1), at a current density of50 mA·g^(-1). After 100 charge/discharge cycles at100 mA·g^(-1), the composite still delivers 330 mAh·g^(-1).