稳定锂电化学沉积和溶解行为的LiC_(6)异质微结构界面层

本文采用机械辊压方法在金属锂表面通过原位固相反应生成LiC_(6)异质微结构界面层,并研究了在碳酸酯有机电解液体系下该异质层对锂电化学沉积和溶解行为的影响。通过形貌表征与电化学测试发现,LiC_(6)异质层能够有效提升锂电化学沉积的可逆性与均匀性,从而抑制枝晶生长及维持沉积/溶解界面的稳定。使用异质层改性金属锂负极的扣式全电池也较纯金属锂负极体系表现出更为优异的循环稳定性。

Nano-channel-based physical and chemical synergic regulation for dendrite-free lithium plating

Uncontrollable dendrite growth resulting from the non-uniform lithium ion(Li^(+))flux and volume expansion in lithium metal(Li)negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries.Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li^(+)flux,the effective interaction distance between lithium ions and N-containing groups should be relatively small(down to nanometer scale)according to the Debye length law.Thus,it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li^(+)flux.In this work,porous carbon nitride microspheres(PCNMs)with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano-and micrometer scales on the Cu/Li foil.Physically,the three-dimensional(3D)porous framework is favorable for absorbing volume changes and guiding Li growth.Chemically,this coating layer can render a suitable interaction distance to effectively homogenize the Li^(+)flux and contribute to establishing a robust and stable solid electrolyte interphase(SEI)layer with Li-F,Li-N,and Li-O-rich contents based on the Debye length law.Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating,resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li||Cu and the Li||Li symmetric cells.Meanwhile,a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of~80%after more than 200 cycles at 1 C and achieved a remarkable rate capability.The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained~73%of the initial capacity after 150 cycles at 0.2 C.

The hydrodynamics of self-rolling locomotion driven by the flexible pectoral fins of 3-D bionic dolphin

The novel autonomous rolling performance is realized by the pair of pectoral fins of a three-dimensional(3-D)bionic dolphin in this paper numerically.3-D Navier-Stokes equations are employed to simulate the viscous fluid around the bionic dolphin.The effect of self-rolling manoeuvrability is ex-plored using the dynamic mesh technology and user-defined function(UDF).By varying the parameter ratios,the interaction of flexible pectoral fins is divided into two motion modes,amplitude differential and frequency differential mode.As the primary driving source,the differential motion of a pair of pec-toral fins can effectively provide the rolling torque,and the trajectory of the entire rolling process is approximately the clockwise spiral.The results demonstrate that the rolling angular velocity and driving torque in the steady state can be improved by increasing parameter ratios,and the rolling efficiency can reach the maximum under the optimal parameter ratio.Meanwhile,different parameter ratios do not af-fect the rolling radius of the self-rolling dolphin.The evolution process around the pair of pectoral fins is shown by the flow structures in self-rolling swimming,reasonably revealing that self-rolling locomotion is produced by the pressure and wake vortices surrounding the pair of pectoral fins,and the wake struc-tures depend primarily on the variation of parameter ratio.It properly turns out that the application of the pair of pectoral fins can realize the self-rolling performance through parameter differential modes.