Sung Man Cho

Quasi-Solid-State Rechargeable Li–O2 Batteries with High Safety and Long Cycle Life at Room Temperature

As interest in electric vehicles and mass energy storage systems continues to grow, Li-O2 batteries are attracting much attention as a candidate for next-generation energy storage systems owing to their high energy density. However, safety problems related to the use of lithium metal anodes have hampered the commercialization of Li-O2 batteries. Herein, we introduced a quasi-solid polymer electrolyte with excellent electrochemical, chemical, and thermal stabilities into Li-O2 batteries. The ion-conducting QSPE was prepared by gelling a polymer network matrix consisting of poly(ethylene glycol) methyl ether methacrylate, methacrylated tannic acid, lithium trifluoromethanesulfonate, and nanofumed silica with a small amount of liquid electrolyte. The quasi-solid-state Li-O2 cell consisted of a lithium powder anode, a quasi-solid polymer electrolyte, and a Pd3Co/multiwalled carbon nanotube cathode, which enhanced the electrochemical performance of the cell. This cell, which exhibited improved safety owing to the suppression of lithium dendrite growth, achieved a lifetime of 125 cycles at room temperature. These results show that the introduction of a quasi-solid electrolyte is a potentially new alternative for the commercialization of solid-state Li-O2 batteries.

Electrochemical Behavior of Li–Cu Composite Powder Electrodes in Lithium Metal Secondary Batteries

A new type of Li-Cu composite powder electrode (Li-Cu CE) was fabricated via mechanical blending of Li and Cu powders. The new Li-Cu electrode is capable of replacing Li metal anodes in Li metal secondary battery (LMSB) systems without exhibiting typical intrinsic problems such as dendrite growth, volume change, and electrolyte depletion. Thus, Li-Cu CE cells can offer longer lives and very high capacities. The Li particles in Li-Cu CEs are surrounded by Cu particles and thus cannot form networks that extend throughout the electrode. Isolation of the Li powder enables the control of Li+ ion migration during deposition and dissolution. The Li-Cu CE can thus prevent problematic volume changes and dendrite growth on the anode during battery operation. Symmetric Li-Cu CE cells are stable for up to 200 cycles at a rate of 3 C, and the anode capacity is estimated to be 1158 mAh g-1 (Li+ ion usage of 30%). These results are thought to represent a largest anode capacity for Li-metal in LMSBs.