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PEO-based solid polymer electrolytes typically show limited capability for the suppression of Li metal dendrites, which is mainly attributed to their low mechanical strength. To tackle this issue, we improved the mechanical strength of a ternary solid polymer electrolyte (TSPE: PEO-LiTFSI-Pyr14TFSI) by integratingCelgard 2500 separator as a high modulus domain. The Celgard-reinforced TSPE (CgTSPE) presents a significantly higher elastic modulus (223MPa) than TSPE (0.2MPa) at 60°C, which in result leads tomore lithium anode utilization. Specifically, the Columbic efficiency of Li electrodeposition/dissolution during cycling in Li|CgTSPE|Cu cells (90%) is distinctly higher than in Li|TSPE|Cu (30%). Furthermore, the cycling of Li||Li symmetric cells with CgTSPE displays an improved cycling stability, due to the presence of Celgard, in which high surface area lithium (HSAL), e.g., dendrite formation is suppressed. Operando electrochemical dilatometry (ECD) analysis as well as post mortem surface analysis with SEM reveal the formation of "dead lithium" and cavities under an areal capacity utilization of 5 mAh/cm2. It is also suggested by the cycling behavior of the Li||Li cell with high areal capacity utilization that lithium surface treatment is required to completely eliminate the formation of "dead lithium" and of cavities. [ABSTRACT FROM AUTHOR]

Lithium-powder electrodes, prepared via paste casting method using lithium powder and polyisobutylene (PIB) as a binder, were investigated for their electrochemical properties in lithium-metal cells. The electrode paste casting method allows preserving the spherical shape of lithium-powder particles during processing to electrodes. However, these lithium-powder based electrodes suffer from poor active material utilization, as electronic isolation of lithium particles during the lithium electrodissolution process was observed to occur. In order to improve the lithium inter-particle contact as well as the contact with the current collector, a simple and effective chemical modification of the lithium-powder based electrodes was considered. Using a cementation reaction with ZnI2, the growth of a Li-Zn intermetallic ("alloy") between the lithium-powder particles and the surface of the lithium powder, lead to an increase of the active material utilization and overcame the side reactions due to lithium electrodissolution. Besides increasing the active material utilization, such simple chemical modification of the lithium-powder based electrodes improved the electrochemical performance resulting in more stable cycling behavior with low polarization and longer cycle life in both LiǁLi-symmetric and LiǁNMC 622 cells. [ABSTRACT FROM AUTHOR]