Exploring the structural properties of cathode and anode materials in Li-ion battery via neutron diffraction technique

As a unique microprobe for structure and dynamics of materials,neutron possesses superior ability in penetration as well as sensitivity for light and magnetic elements in comparison with X-ray and electron.As for the research and development of lithium-ion batteries(LIBs),neutron diffraction techniques play an indispensable role in exploring the structural properties of various electrode materials,especially the detailed structural evolution of cathode and anode materials during electrochemical cycling.Moreover,based on thorough analysis of neutron diffraction results,an in-depth and systematic understanding of some fundamental mechanisms,such as the formation mechanism of defects and migration mechanism of lithium ions,could also be established,which is essential for the development of high-performance electrode materials for the next-generation LIBs.Nevertheless,that technique would not seem to be widely applied yet in comparison with the application of X-ray diffraction and more attention should be paid.To demonstrate the advantages of neutron diffraction technique in research of LIBs materials,this work systematically summarizes representative neutron diffraction studies on exploring structural details hidden in electrode materials and on probing structural evolution of electrode materials during charge/discharge processes.Prospects for further applications of neutron diffraction techniques in research of LIBs are also put forward.

Study of Polytropic Exponent Based on High Pressure Switching Expansion Reduction

Switching expansion reduction(SER) uses a switch valve to substitute the throttle valve to reduce pressure for high pressure pneumatics.The experiments indicate that the simulation model well predicts the actual characteristics.The heat transfers and polytropic exponents of the air in expansion tank and supply tanks of SER have been studied on the basis of the experiments and the simulation model.Through the mathematical reasoning in this paper,the polytropic exponent can be calculated by the air mass,heat,and work exchanges of the pneumatic container.For the air in a constant volume tank,when the heat-absorption is large enough to raise air temperature in discharging process,the polytropic exponent is less than 1;when the air is experiencing a discharging and heat-releasing process,the polytropic exponent exceeds the specific heat ratio(the value of 1.4).