Performance Of Li Metal Anode Research Articles

New Artificial Interphase with Li-Ion Pathway between Li Metal and Electrolytes for Secure Lithium Metal Anodes

While Li-ion batteries were firstly studied with Li metal as anodes due to its high theoretical specific capacity (3860 mA h g-1) and lowest negative electrochemical potential (-3.040 V vs SHE), commercial Li-ion batteries since 1992 consisted of graphite as an anode because of critical safety issues. However, for several decades, many strategies have been developed to surmount difficulties like problems of dendrite growth using modifications of electrolytes with additives, a change of lithium metal morphology, and an introduction of chemical/physical coating layers on Li metal. Herein, we report a simple approach to improve the electrochemical performance of Li metal anodes in Li-ion batteries with commercial carbonate-based electrolytes by utilizing a high Li-ion conductor, Li2TiO3, on Li metal anodes. Monoclinic Li2TiO3 is electrochemically inert in a wide voltage range with excellent structural stability in a liquid electrolyte. In addition, it structurally has a 3D path for Li-ion diffusions, leading to more uniform Li-ion flux. Li2TiO3 nanoparticles with a size of sub-100 nm were synthesized via a sol-gel method, and then the resulting particles were mixed with carbon as a conducting material and PVDF-HFP as a binder. A bright Li metal surface was covered with gray Li2TiO3 films in Figure 1a. From various Li plating and striping tests with pristine and modified Li metal as working electrodes, the modified Li metal exhibited outstanding electrochemical performances such as stable coulombic efficiency over 100th cycles at 1 mA/cm2 as shown in Figure 1c. Moreover, the modified Li metal was applied for practical lithium-ion batteries as a counter electrode to confirm the protective effects with LMO as a working electrode at a room temperature (25 oC) and high temperature (60 oC). Figure 1

Dendrite-free Li metal anode by lowering deposition interface energy with Cu99Zn alloy coating

Li should be the ultimate anode due to its highest theoretical capacity and lowest electrochemical potentials. However, the dendrite formation has been the grand challenge hindering their direct use. Here we modified the commercial anode Cu current collectors with atomically distributed Zn artificial defects by magnetic sputtering of Cu99Zn. Zn has definite solubility in Li metal and can form solid solution before Li metal deposition, lowering the deposition interface energy between current collectors and metal anodes. With atomically distributed seeds, significantly improved performance of Li metal anodes was achieved with depressed dendrite formation on both planar and 3D Cu. The Li-Li symmetric cell can be stably cycled for more than 1000 h. Coulombic efficiency over 98% at Li deposition capacity of 10 mAh cm−2 could be maintained. We anticipate that high performance lithium metal batteries could be realized by using this anode combined with optimized electrolytes and cathodes.

Enabling reliable lithium metal batteries by a bifunctional anionic electrolyte additive

Lithium metal has been considered as an attractive anode for high energy density lithium battery because of high specific capacity and the lowest redox potential. However, the growth of Li dendrites during cycling has hindered the practical application of Li metal battery (LMB). Herein, TTFEB is adopted as a bifunctional electrolyte additive to improve the performance of Li metal anode, which is beneficial for the surface chemistry of anode and the property of the electrolyte. A LiF-rich SEI layer and enhanced Li+ migration in electrolyte can be achieved with 2% TTFEB, which result in uniform Li deposition without uncontrollable Li dendrites. With controlled Li deposition in TTFEB-containing electrolyte, a significantly improved Coulombic efficiency (~ 96%) in Li|Cu cell, long lifetime (over 1000h), and weak polarization in Li|Li cell can be obtained. Moreover, excellent cycling performance and rate capability of Li|LiFePO4 cells with TTFEB are also presented in this work. Our strategy provides new insights on the diverse function of electrolyte additives for rechargeable LMB.

Toward Dendrite-Free Lithium Deposition via Structural and Interfacial Synergistic Effects of 3D Graphene@Ni Scaffold.

Owing to its ultrahigh specific capacity and low electrochemical potential, lithium (Li) metal is regarded as one of the most attractive anode materials for next-generation lithium batteries. Nevertheless, the commercialization of Li-metal-based rechargeable batteries (LiMBs) has been retarded by the uncontrollable growth of Li dendrites, as well as the resulting poor cycle stability and safety hazards. In this work, a 3D graphene@Ni scaffold has been proposed to accomplish dendrite-free Li deposition via structural and interfacial synergistic effects. Due to the intrinsic high surface area used to reduce the effective electrode current density and the surface-coated graphene working as an artificial protection layer to provide high cycle stability as well as suppress the growth of Li dendrites, the Coulombic efficiencies of Li deposition on 3D graphene@Ni foam after 100 cycles can be sustained as high as 96, 98, and 92% at the current densities of 0.25, 0.5, and 1.0 mA cm-2, respectively, which shows more excellent cycle stability than that of its planar Cu foil and bare Ni foam counterparts. The results obtained here demonstrate that the comprehensive consideration of multiaspect factors could be more help to enhance the performance of Li metal anode so as to achieve its real application in next-generation LiMBs.