Effect of electrode change on solidification of slag and metal pool profile in electroslag remelting process

A two-dimensional axisymmetric model is established to study the effect of electrode change on the solidification of slag and metal pool profile during electroslag remelting process.The basic considerations of flow and heat transfer are included in the model,and the growth of ingot is described by the dynamic mesh technique.The electrode melting rate is predicted based on the transient thermal conductivity model between slag and electrode.The results indicate that in the electrode change stage,the slag temperature drops from 1847 to 1763 K gradually and the“hot heart”phenomenon is observed.And the metal pool profile is slightly changed with a depth decrease from 0.3984 to 0.3688 m.In the heating and melting stage of new electrode,the maximum slag temperature firstly increases from 1763 to 1892 K,then decreases to 1845 K,and finally at 3558 s,the maximum slag temperature is stable at 1884 K.Solidified slag shell with a maximum volume of 7.31×10^(-3) m^(3) is formed at the electrode tip,and then,the solidified slag melts completely.The depth of metal pool firstly rises to 0.3700 m and then drops to 0.3565 m.As the preheating temperature of the new electrode increases from 473 to 973 K,the maximum volume of solidified slag decreases from 0.00748 to 0.00592 m^(3),and the time from heating to melting of the new electrode decreases from 996 to 887 s.

Multi-dimensional hybrid flexible films promote uniform lithium deposition and mitigate volume change as lithium metal anodes

Lithium metal is the ultimate anode material for next-generation high-energy batteries.Yet,the practical application of lithium metal anodes is limited by the formation of Li dendrites and large volume changes.Herein,an effective multi-dimensional hybrid flexible film(MD-HFF)composed of iodine ion(0 dimension),CNTs(1 dimension)and graphene(2 dimensions)is designed for regulating Li deposition and mitigating volume changes.The multi-dimensional components serve separate roles:(1)iodine ion enhances the conductivity of the electrode and provides lithiophilic sites,(2)CNTs strengthen interlaminar conductance and mechanical strength,acting as a spring in the layered structure to alleviate volume changes during Li plating and stripping and(3)graphene provides mechanical flexibility and electrical conductivity.The resulting MD-HFF material supports stable Li plating/stripping and high Coulombic efficiency(99%)over 230 cycles at 1 mA cm^(-2) with a deposition capacity of 1 mAh cm^(-2).Theoretical calculations indicate that LiI contributes to the lateral growth of Li on the MD-HFF surface,thereby inhibiting the formation of Li dendrites.When paired with a typical NCM811 cathode,the assembled MD-HFF‖NCM811 cell exhibit improved capability and stable cycling performance.This research serves to guide material design in achieving Li anode materials that do not suffer from dendrite formation and volume changes.