High-rate lithium-ion battery performance of a ternary sea urchin-shaped CoNiO_(2)@NiP_(6)Mo_(18)/CNTs composites

Bimetallic oxides are attractive anode materials for lithium-ion batteries(LIBs)due to their large theoretical capacity.However,the low conductivity,short cycle life,and poor rate capability are the bottlenecks for their further applications.To overcome above issues,the basket-like polymolybdate(NiP_(6)Mo_(18))and carbon nanotubes(CNTs)were uniformly embedded on the urchin-shaped CoNiO_(2)nanospheres to yield a ternary composites CoNiO_(2)@NiP_(6)Mo_(18)/CNTs via electrostatic adsorption.The multi-level morphology of urchin spinules accelerates the diffusion rate of Li^(+);CNT improves the conductivity and enhances cycle stability of the material;and heteropoly acid contributes more redox activity centres.Thus,CoNiO_(2)@NiP_(6)Mo_(18)/CNTs as an anode of LIBs exhibits a high initial capacity(1396.7 mA h g^(−1)at 0.1 A g^(−1)),long-term cycling stability(750.2 mA h g^(−1)after 300 cycles),and rate performance(450.3 mA h g^(−1)at 2 A g^(−1)),which are superior to reported metallic oxides anode of LIBs.The density functional theory(DFT)and kinetic mechanism suggest that CoNiO_(2)@NiP_(6)Mo_(18)/CNTs delivers an outstanding pseudocapacitance and rapid Li^(+)diffusion behaviors,which is due to the rich surface area of the urchin-like CoNiO_(2)with the uniform embeddedness of NiP_(6)Mo_(18)and CNTs.This study provides a new idea for optimizing the performance of bimetallic oxides and developing high-rate lithium-ion battery composites.

A bi-As-capped and tetra-V-substituted arsenomolybdate:synthesis,structure,capacitive and electrocatalytic properties

A bi-As-capped and tetra-V-substituted arsenomolybdate(Hbib)_(2)(biyb)_(3)[As^(Ⅲ)_(2)As^(Ⅴ)Mo^(Ⅵ)8V^(Ⅴ)_(4)O_(40)]_(2)·H_(2)O(1)(bib=1.4-Bis(imidazoly)butane;biyb=1,4-bis(imidazol-1-ylmethyl)benzene)has been constructed through hydrothermal methods and characterized by conventional method.Compound 1 is a tetra-V substituted{AsMo^(Ⅵ)_(8)V^(Ⅴ)_(4)O_(4)}polyanions capped by two AsⅢcations at two symmetrical ditch in{AsO_(4)}rectangular pyramid geometry.It exhibits higher specific capacitance,capacitance retention,and electrocatalytic activities for oxidizing ascorbic acid and reducing peroxide hydrogen.

Mechanical properties of Ti_(3)AlC_(2)ceramics before and after heat treatment

Ti_(3)AIC_(2)ceramics were heat treated at the temperature from 1050 to 1450℃.Vickers hardness,fracture toughness,flexural strength and compressive strength of Ti_(3)AlC_(2)were tested and calculated before and after heat treatment,respectively.Ti_(3)AIC_(2)content,fracture toughness,flexural strength and compressive strength of Ti_(3)AIC_(2)first increase and then decrease,while Vickers hardness is just the opposite with the increase in temperature from 1050 to 1450℃C.After heat treatment at1250℃,Ti_(3)AIC_(2)content reaches the highest level of94.2 wt%,and fracture toughness,flexural strength and compressive strength reach the maximum values,which are6.4 MPa·m^(1/2),318 MPa and 662 MPa,respectively.Vickers hardness reduces to the lowest value of 2.9 GPa.Heat treatment does improve the strength and Ti_(3)AlC_(2)content,but reduces the hardness and optimizes the mechanical properties of Ti_(3)AlC_(2).