The surface morphology of Li metal electrode

Abstract

Surface morphological changes of Li powder compacted electrodes were investigated and compared with extruded Li foil electrodes during the dissolution (discharge)/deposition (charge) process. The area of derlclrite growing surfaces was reduced remarkably for Li powder compacted electrodes. Impedance measurements showed that Li compacted powder electrodes had a lower resistance than Li foil electrodes. This is presumed to be related with resistance reduction due to increasing ion conductivity in the SEI (solid electrolyte interface) formed on the surface along with the increase of the reaction area for the powder electrode.Keywords : lithium, battery, SEI, impedance, lithium metal battery, lithium powder I N T R O D U C T I O NAlthough pure Li metal has remarkable electrochemical characteristics of not only increasing the capacity but also reducing the weight of secondary batteries, carbon is used instead as anode active material for Li-ion batteries. This is mainly due to the cycling efficiency deterioration and safety problem caused by dendrite growth during the deposition (charge) which limits its application [1][2][3]. Some parts of deposited Li are isolated from newly formed surface films [1,2]. Such isolated Li, called dead Li, is electrically separated from Li metal substrate, and cannot participate in the electrochemical reaction [1,2]. It results in capacity loss, and reduces the cycling efficiency. Moreover, Li dendrites may pierce the separator and cause short circuits in batteries [3].The most popular model for the interface between Li metal and nonaqueous electrolytes, proposed by Peled, is called the solid electrolyte interface (SEI) model [4]. In the SEI model, the surface film can affect the morphology of the electrodeposited Li because Li metal is deposited via migration of Li § ions through the SEI film. The SEI films are known to be composed of various lithium compounds such as LiOH, Li20, and Li2CO3 [5], and therefore the as-formed SEI film has heterogeneous compositions. In the case of a rechargeable battery, the charging current distribution in such an SEI film is localized and causes dendritic growth [3].Dendritic growth of deposited Li causes the worst problem in metal rechargeable batteries; for this reason much research has been done on the prevention of Li dendrite growth. It has been said that Li dendrite growth is restrained when SEI is stable, thin, smooth and homogeneous [3]. This condition can be brought about by surface control using various additives such as CO2, HE surfactants, etc. [3,[6][7].In this paper, compacted Li powders that were made in the lab were introduced for the Li metal battery anode and the results were compared with those of conventionally extruded Li foil. Half-cell tests were performed on both the powders and the foils to observe the mechanism of Li dendrite growth. The changes o f the surface morphology of Li were investigated through an optical microscope. Impedance measurement of the powders and the foil specimen were also done. EXPERIMENTALSTo find Li den...

Air‐Stable Lithium Spheres Produced by Electrochemical Plating

“…The phase identificationsare marked in the EDPs in (g) and (h). [15] Thestabilized Li powders were compacted and used as the electrode for Li-ion battery, [15] and results show that dendrite growth in the compacted electrode was reduced significantly as compared with an extruded Li foil electrode.I narelated study,i tw as reported that Li 2 CO 3 particles treated graphite electrode showed much better capacity retention, particularly for the first cycle, as compared to the non-treated electrode,because the SEI layer with ah igher Li 2 CO 3 concentration enhanced the stability and assisted Li + diffusion, improving the capacity retention. To test whether the ASLSs can be used as anodes for Li-ion batteries, we constructed an anobattery using an ASLS as an anode, the shell of Li 2 CO 3 and Li 2 Oa sthe electrolyte, and an Au-coated CuO nanowire as the cathode inside the ETEM.…”

“…This result confirms that ASLSs are aversatile anode material for lithium batteries.T he structure of the ASLSs is similar to the surface-stabilized Li powders produced by the droplet emulsion technique (DET), which also exhibit aLi 2 CO 3 shell and aLicore. [15] Thestabilized Li powders were compacted and used as the electrode for Li-ion battery, [15] and results show that dendrite growth in the compacted electrode was reduced significantly as compared with an extruded Li foil electrode.I narelated study,i tw as reported that Li 2 CO 3 particles treated graphite electrode showed much better capacity retention, particularly for the first cycle, as compared to the non-treated electrode,because the SEI layer with ah igher Li 2 CO 3 concentration enhanced the stability and assisted Li + diffusion, improving the capacity retention. [16] Remarkably,A sadi and co-workers recently reported ar ecord-long cycle lifetime of 700 cycles for aL iair battery by using aL i 2 CO 3 -protected Li foil as the anode and cycling in asimulated air atmosphere.They attributed the record-long cycle lifetime to the presence of aL i 2 CO 3 passivation layer on the Li surface,w hich protects the metallic Li from corrosion by the moisture,C O 2 ,a nd O 2 in an air-like atmosphere.…”

Enhanced Capacity of Lithium Secondary Batteries Using a Li-Powder Anode

“…Unfortunately, the commercialization of lithium-metal cells is limited by various factors, such as dendrite growth, an unstable solid–electrolyte interphase (SEI), and capacity fading. Electrolyte additives, ex situ artificial layers, and composite anodes have been tested to suppress Li dendrite growth and stabilize the SEI. − In addition, Li powder has been demonstrated to be effective in suppressing dendrite growth, forming a stable SEI and a stable interface shape and area, according to data that have been reported in the last few decades. − ,− …”

Lithium Powder Synthesis and Preparation of Powder‐Based Composite Electrodes for Application in Lithium Metal Batteries

“…Kim et al [21] introduced the droplet emulsion technique (DET) for synthesis of lithium powder (Li p ) that was used for the preparation of compact Li p electrodes. In comparison with Li foil electrodes, the Li p electrodes demonstrated lower impedance and reduced HSAL formation after Li electrodeposition/electrodissolution processes.…”

“…The improved performance was attributed to the higher ionic conductivity of the solidÀelectrolyte interphase (SEI) [22] formed on such Li p particles and the larger surface area of the Li p electrodes that lead to lower local current densities and thus suppressed HSAL formation. [21] Based on the work of Kim et al, [21] further studies focused on the synthesis of surface-coated Li p , [23] where improved performance of Li p electrodes was achieved by the application of a higher compression degree, [24] the preparation of composite Li p electrodes using Cu powder, [25] and by chemical modification of the Li p particles in Li p electrodes using a cementation reaction with ZnI 2 . [26] Although the DET method was described in regard to the processing steps, [23,27,28] little work has been focused on deciphering the effect that various parameters within the DET method have on the particle size, shape, and interfacial properties of the synthesized Li p particles.…”