The Ti-Al alloy was synthesized using the aluminothermic reduction of TiO_(2),with CaO and MgF_(2)serving as flux components.Investigations were conducted to ascertain the effects of MgF_(2)content on the alloy-slag s...The Ti-Al alloy was synthesized using the aluminothermic reduction of TiO_(2),with CaO and MgF_(2)serving as flux components.Investigations were conducted to ascertain the effects of MgF_(2)content on the alloy-slag separation,alloy microstructure,composition,phase constitution,overall alloy yield,and aluminothermic reduction of TiO_(2).Results indicate that MgF_(2)enhances the separation of the alloy from slag and promotes the formation of the TiAl phase within the alloy matrix.Nevertheless,an overabundance of MgF_(2)reduces the interfacial tension between the Al reductant and the slag,leading to significant loss of Al.This adversely affects alloy-slag separation,escalates the incorporation of oxide inclusions in the alloy,and severely reduces the recovery rate of alloy.Concurrently,the alloy has a phase transition from TiAl to Ti_(3)Al.The optimum condition for alloy-slag separation and alloy integrity is realized at the MgF_(2)content of 10wt%.Kinetic analysis at this flux ratio determines the activating energy for the Al-TiO_(2)-CaO-MgF_(2)system,which is 409.729 kJ/mol,and the order of kinetics is n=0.38.展开更多
Lithium metal batteries(LMBs)with high energy density are impeded by the instability of solid electrolyte interface(SEI)and the uncontrolled growth of lithium(Li)dendrite.To mitigate these challenges,optimizing the SE...Lithium metal batteries(LMBs)with high energy density are impeded by the instability of solid electrolyte interface(SEI)and the uncontrolled growth of lithium(Li)dendrite.To mitigate these challenges,optimizing the SEI structure and Li deposition behavior is the key to stable LMBs.This study novelty proposes a facile synthesis of MgF_(2)/carbon(C)nanocomposite through the mechanochemical reaction between metallic Mg and polytetrafluoroethylene(PTFE)powders,and its modified polypropylene(PP)separator enhances LMB performance.The in-situ formed highly conductive fluorine-doped C species play a crucial role in facilitating ion/electron transport,thereby accelerating electrochemical kinetics and altering Li deposition direction.During cycling,the in-situ reaction between MgF_(2)and Li leads to the formation of LiMg alloy,along with a LiF-rich SEI layer,which reduces the nucleation overpotential and reinforces the interphase strength,leading to homogeneous Li deposition with dendrite-free feature.Benefiting from these merits,the Li metal is densely and uniformly deposited on the MgF_(2)/C@PP separator side rather than on the current collector side.Furthermore,the symmetric cell with MgF_(2)/C@PP exhibits superb Li plating/stripping performance over 2800 h at 1 mA cm^(-2)and 2 mA h cm^(-2).More importantly,the assembled Li@MgF_(2)/C@PPILiFePO4full cell with a low negative/positive ratio of 3.6delivers an impressive cyclability with 82.7%capacity retention over 1400 cycles at 1 C.展开更多
基金National Natural Science Foundation of China(52074052)。
文摘The Ti-Al alloy was synthesized using the aluminothermic reduction of TiO_(2),with CaO and MgF_(2)serving as flux components.Investigations were conducted to ascertain the effects of MgF_(2)content on the alloy-slag separation,alloy microstructure,composition,phase constitution,overall alloy yield,and aluminothermic reduction of TiO_(2).Results indicate that MgF_(2)enhances the separation of the alloy from slag and promotes the formation of the TiAl phase within the alloy matrix.Nevertheless,an overabundance of MgF_(2)reduces the interfacial tension between the Al reductant and the slag,leading to significant loss of Al.This adversely affects alloy-slag separation,escalates the incorporation of oxide inclusions in the alloy,and severely reduces the recovery rate of alloy.Concurrently,the alloy has a phase transition from TiAl to Ti_(3)Al.The optimum condition for alloy-slag separation and alloy integrity is realized at the MgF_(2)content of 10wt%.Kinetic analysis at this flux ratio determines the activating energy for the Al-TiO_(2)-CaO-MgF_(2)system,which is 409.729 kJ/mol,and the order of kinetics is n=0.38.
基金financially supported by the Natural Science Foundation of China(52277218)the Hubei Provincial Natural Science Foundation of China(2024AFA094)+1 种基金the Excellent Discipline Cultivation Project by JHUN(2023XKZ009)the Graduate Student Innovation Fund of JHUN(KYCXJJ202422).
文摘Lithium metal batteries(LMBs)with high energy density are impeded by the instability of solid electrolyte interface(SEI)and the uncontrolled growth of lithium(Li)dendrite.To mitigate these challenges,optimizing the SEI structure and Li deposition behavior is the key to stable LMBs.This study novelty proposes a facile synthesis of MgF_(2)/carbon(C)nanocomposite through the mechanochemical reaction between metallic Mg and polytetrafluoroethylene(PTFE)powders,and its modified polypropylene(PP)separator enhances LMB performance.The in-situ formed highly conductive fluorine-doped C species play a crucial role in facilitating ion/electron transport,thereby accelerating electrochemical kinetics and altering Li deposition direction.During cycling,the in-situ reaction between MgF_(2)and Li leads to the formation of LiMg alloy,along with a LiF-rich SEI layer,which reduces the nucleation overpotential and reinforces the interphase strength,leading to homogeneous Li deposition with dendrite-free feature.Benefiting from these merits,the Li metal is densely and uniformly deposited on the MgF_(2)/C@PP separator side rather than on the current collector side.Furthermore,the symmetric cell with MgF_(2)/C@PP exhibits superb Li plating/stripping performance over 2800 h at 1 mA cm^(-2)and 2 mA h cm^(-2).More importantly,the assembled Li@MgF_(2)/C@PPILiFePO4full cell with a low negative/positive ratio of 3.6delivers an impressive cyclability with 82.7%capacity retention over 1400 cycles at 1 C.
