is primarily attributed to uncontrolled Li dendrite growth, which inevitably occurs on the Li surface during repeated plating/ stripping processes. Li dendrite-growth leads to battery performance failure and thermal runaway, causing a catastrophic safety failure accompanied by fi re and smoke. With the emergence of Li-ion batteries (LIBs) based on the Li intercalating anode materials represented by carbonaceous anodes in the early 1990s, enthusiasm for developing commercial Li metal secondary batteries has largely diminished. [ 3,[8][9][10] Recently, the need for electric vehicles (EVs) and energy storage systems (ESSs) that require a higher level energy density from electric energy sources than that available from commercialized LIBs has sparked renewed interest in Li metal anodes. Rechargeable batteries using Li metal anodes such as Li/air [11][12][13] or Li/sulfur [14][15][16] batteries are attracting increasing attention as possible alternatives, with many researchers devoting intense efforts to realize these systems. For successful implementation of such nextgeneration battery systems beyond LIBs, signifi cant challenges remain for each battery constituent, including Li metal anodes, cathodes, electrolytes, and battery system design. Above all, harmonious improvement in each fi eld is a prerequisite. Li metal stabilization is a burdensome task because of the well-known diffi culties encountered during the long history of Li battery research and the resultant failure to realize the use of Li metal in a commercialized rechargeable battery system during the last four decades.During the fi rst charging process, the higher cathodic potential compared with the Li ion reduction leads to reductive decomposition of electrolytes, including organic solvents and Li salt on Li metal, and the formation of electrically insulating but ionically conducting protective fi lm called surface electrolyte interphase (or interface, SEI). [ 8,[17][18][19] This passive layer ideally permits Li ion migration and prevents further electrolyte decomposition, enabling stable cycle performance of LIBs in the subsequent cycles. As discussed extensively, [ 18,[20][21][22][23] SEI is understood to be a highly complicated Li ion conducting layer consisting of many different decomposed products with inorganic and organic components, such as Li 2 CO 3 , Li 2 O, LiCO 2 R, LiF, and Li alkoxides. SEI inevitably possesses lateral and vertical non-uniformity, which leads to uneven Li ion conduction. During the charging process, Li ions moving through SEI Repressing uncontrolled lithium (Li) dendrite growth is the top priority for enabling the reliable use of Li metal secondary batteries. On the other hand, the technique controlling the metal plating behavior during metal plating indeed has been considered very diffi cult to achieve. For instance, how can one plate metal ions on the favored selected region during plating? The present study describes how to achieve this goal, i.e., dendrite-free Li deposition, by mechanical surface modifi cation using ...

A highly adhesive and thermally stable copolyimide (P84) that is soluble in organic solvents is newly applied to silicon (Si) anodes for high energy density lithium-ion batteries. The Si anodes with the P84 binder deliver not only a little higher initial discharge capacity (2392 mAh g(-1)), but also fairly improved Coulombic efficiency (71.2%) compared with the Si anode using conventional polyvinylidene fluoride binder (2148 mAh g(-1) and 61.2%, respectively), even though P84 is reduced irreversibly during the first charging process. This reduction behavior of P84 was systematically confirmed by cyclic voltammetry and Fourier-transform infrared analysis in attenuated total reflection mode of the Si anodes at differently charged voltages. The Si anode with P84 also shows ultrastable long-term cycle performance of 1313 mAh g(-1) after 300 cycles at 1.2 A g(-1) and 25 °C. From the morphological analysis on the basis of scanning electron microscopy and optical images and of the electrode adhesion properties determined by surface and interfacial cutting analysis system and peel tests, it was found that the P84 binder functions well and maintains the mechanical integrity of Si anodes during hundreds of cycles. As a result, when the loading level of the Si anode is increased from 0.2 to 0.6 mg cm(-2), which is a commercially acceptable level, the Si anode could deliver 647 mAh g(-1) until the 300th cycle, which is still two times higher than the theoretical capacity of graphite at 372 mAh g(-1).

No abstract

In article 1600140, Myung‐Hyun Ryou and Yong Min Lee suggest that the well‐designed surface‐patterns on Li metal may resolve the chronic Li dendrite formation problem of Li metal electrodes, which restricted the implementation of Li metal in a practical secondary battery system over five decades.

No abstract