Dealloying induced nanoporosity evolution of less noble metals in Mg ion batteries

Rechargeable Mg ion batteries(MIBs)have aroused great interests,and using alloy-type anodes and conventional electrolytes offers an effective way to develop high energy density Mg battery systems.However,the dealloying-induced nanoporosity evolution of alloy-type anodes during the charging process has received less attention.Herein,using a magnetron-sputtered Mg;Bi;film as an example,we investigate its electrochemical dealloying and associated structural evolution in an all-phenyl-complex electrolyte by in-situ and ex-situ characterizations.The microstructures and length scales of nanoporous Bi can be facilely regulated by changing electrochemical parameters,and there exists a good linear correlation between the surface diffusivity of Bi and the applied current density/potential scan rate on a logarithm scale.More importantly,the self-supporting nanoporous Bi electrodes deliver satisfactory Mg storage performance and alloy-type anodes show good compatibility with conventional electrolytes.Furthermore,the charging-induced dealloying in MIBs is a general strategy to fabricate nanoporous less noble metals like Sn,Pb,In,Cu,Zn and Al,which shows advantages over chemical dealloying in aqueous solutions.Our findings highlight the significance of nanoporosity evolution of alloy-type anodes during dealloying,and open opportunities for the fabrication of nanoporous reactive metals.

Self-healing Ga-based liquid metal/alloy anodes for rechargeable batteries

With the rapid development of electronics,electric vehicles,and grid energy storage stations,higher requirements have been put forward for advanced secondary batteries.Liquid metal/alloy electrodes have been considered as a promising development direction to achieve excellent electrochemical performance in metal-ion batteries,due to their specific advantages including the excellent electrode kinetics and self-healing ability against microstructural electrode damage.For conventional liquid batteries,high temperatures are needed to keep electrode liquid and ensure the high conductivity of molten salt electrolytes,which also brings the corrosion and safety issues.Ga-based metal/alloys,which can be operated at or near room temperature,are potential candidates to circumvent the above problems.In this review,the properties and advantages of Ga-based metal/alloys are summarized.Then,Ga-based liquid metal/alloys as anodes in various metal-ion batteries are reviewed in terms of their self-healing ability,battery configurations,working mechanisms,and so on.Furthermore,some views on the future development of Ga-based electrodes in batteries are provided.

Amorphous germanium-crystalline bismuth films as a promising anode for magnesium-ion batteries

Magnesium-ion batteries(MIBs)are promising alternatives to lithium-ion batteries due to their safety and high theoretical specific capacity,and the abundance of magnesium reserves.However,their anodes and electro-lytes severely restrict the development of MIBs,so alloy-type anodes provide an effective strategy to circum-vent the surface passivation issue encountered with Mg metal in conventional electrolytes.Theoretically,a germanium anode can deliver a high specific capacity of 1476 mAh g?1,but hitherto,no experimental reports have described Ge in MIBs.Herein,we experimentally verified that Ge could reversibly react with Mg 2þions through the design of dual-phase Ge–Bi film electrodes fabricated by magnetron co-sputtering.Notably,a Ge 57 Bi 43 electrode delivered a high specific capacity of 847.5 mAh g?1,owing to the joint alloying reactions of Ge and Bi with Mg,which was much higher than the specific capacity of Bi(around 385 mAh g?1).Moreover,the Ge–Bi anode showed excellent rate performance,good cycling stability,and superior compatibility with conventional electrolytes such as Mg(TFSI)2.More importantly,the Mg storage mechanism of the Ge–Bi anode was unveiled by operando X-ray diffraction,and density functional theory calculations rationalized that the introduction of Bi to form Ge–Bi evidently decreased the defect formation energy and effectively boosted the electrochemical reactivity of Ge with Mg.

Self-supporting, eutectic-like, nanoporous biphase bismuth-tin film for high-performance magnesium storage

Magnesium ion batteries are emerging as promising alternatives to lithium ion batteries because of their advantages including high energydensity,dendrite-free features and low cost.Nevertheless,one of the major challenges for magnesium ion batteries is the kinetically sluggishmagnesium insertion/extraction and diffusion in electrode materials.Aiming at this issue,biphase eutectic-like bismuth-tin film is designedherein to construct a self-supporting anode with interdigitated phase distribution and hierarchically porous structure,and further fabricated bya facile one-step magnetron cosputtering route.As benchmarked with single-phase bismuth or tin film,the biphase bismuth-tin film delivershigh specific capacity (538 mAh/g at 50 mA/g),excellent rate performance (417 mAh/g at 1,000 mA/g) and good cycling stability (233 mAh/gat the 200th cycle).The superior magnesium storage performance of the sputtered bismuth-tin film could be attributed to the synergetic effectof the interdigitated bismuth/tin phase distribution,hierarchically porous structure and biphase buffering matrices,which could increase ionictransport channels,shorten diffusion lengths and reduce total volume changes.

Phase-boundary regulation boosting electrochemical reactivity of tin-based anodes for magnesium-ion batteries

Tin(Sn)-based materials are promising anodes for magnesium-ion batteries(MIBs) owing to their low reaction voltages, high theoretical specific capacities and good compatibility with conventional electrolytes. However, relatively arduous alloying reaction and sluggish diffusion kinetics limit their practical applications. Herein, we proposed a general strategy to regulate the electrochemical reactivity and performance of Sn-based anodes for Mg storage through the introduction of the second phase and phase boundary. The biphase Sn–Al, Sn–Pb and Sn–Zn O films were further fabricated via magnetron co-sputtering. Taking Sn–Al as an example, it has been revealed that the introduction of Al can effectively stimulate the electrochemical reaction of Sn with Mg in either nanoscale or bulk through combining experiments with density-functional theory calculations. Specially, the rolled Sn–Al electrode exhibits superior long-term stability over 5,000 cycles. Additionally, the Mg-storage mechanism of the Sn–Al electrode was investigated by operando X-ray diffraction. The Sn–Al anodes also demonstrate good compatibility with simple Mg-salt-based electrolytes like Mg(TFSI)2in full cells. More importantly, it has been authenticated that the activation effect of second phase and phase boundary to Sn is also applicable to Pb and Zn O. Our findings may provide a favorable reference for the development of alloy-type anodes for MIBs.