Constructing High-Performance Alkali Metal Anodes Via Optimizing Thermal Distribution Based On Interface Regulation

Recently,alkali metal anodes are of great competitiveness in anode materials due to their low electrochemical potential and high theoretical specific capacity.But the dendrite growth during the charge/discharge process and the related safety problems seriously hinder their further development.However,the proposed protection routes are mainly focusing on the reaction surface(the interface between alkali metal anode surface and electrolyte).It is thought that the alkali metal anode can achieve dendrite-free deposition even with hundreds of microns in thickness merely through the regulation of substrate surface.Based on the conclusion,a doubt is put forward in the paper:whether there are other correlation mechanisms between the inner of electrode and surface deposition behavior.And we make an in-depth exploration on the issue.(1)The different interface contacts originating from lithiophilic and lithiophobic nucleation can result in different interface current densities,which cannot be directly related with the state of surface current density.Instead,the disordered joule heat distribution induced by irregular interface structure in the inner of electrode may be the core reason affecting the dendrite.To verify the conjecture,we do the following researches:At first,it is pr oved that the temperature-sensitive polarization of lithium(Li)plating through the potential comparison of Li deposition and Li ion(Li~+)embedding in graphite negative electrode under temperature fluctuation.Although many reports have confirmed the temperature effect on Li dendrite,the corresponding mechanisms have not been accounted yet for the surface deposition behavior on the electrode affected by lithiophilic and lithiophobic nucleation.However,with the charge transfer,the thermal distribution on Li metal surface becomes different because of joule heat based on different interface contact,which may be the important factor for dendrite growth.Then combined with theoretical simulation and experimental verification,we find that the uneven interface structure inside the electrode can induce disordered surface thermal distribution and plating morphology,which can be considered as another influence factor for chaotic dendrite.(2)Based on the above concept,a new strategy of liquid metal welding(LMW)integrated electrode is proposed to optimize the interface contact between collector and Li metal anode in traditional electrode,which can obtain a compact interface with high thermal conductivity owing to the liquid state at room temperature and good thermal conductivity of gallium(Ga)-based liquid metal.Thus homogenizing the thermal distribution on the Li surface and promoting the uniform and dense Li deposition.Besides,the corresponding batteries show the obvious advantages no matter in ether-based or ester-based electrolytes.(3)Due to the poor thermal conductivity of separator and electrolyte usually used in batteries,the thermal effect caused by the uneven structure of the electrode itself at the reaction interface cannot be homogenized thr ough other interface contacts.According to the concept of joule heat distribution affecting dendrite,uniform thermal distribution can suppress dendrite effectively.Therefore,using high thermal conductivity materials to repair the thermal distribution of electrode reaction interface can be a promising protection strategy.In addition,the degree of thermal restoration can be regulated by adjusting the damage degree and usage of the thermal conductive materials.And the corresponding electrochemical performance also shows a positive proportional relationship.In a word,the more uniform temperature distribution on the surface of alkali metal anodes,the more conducive to the improvement of electrochemical performance.And it is further proved that homogenizing the thermal distribution at the electrode surface is an effective way to achieve stable alkali metal anodes.