Eun-Gi Shim

Electrochemical Performance of Li-Ion Batteries Containing Biphenyl, Vinyl Ethylene Carbonate in Liquid Electrolyte

This paper investigated the electrochemical behavior and thermal properties of vinyl ethylene carbonate (VEC) and biphenyl (BP) additives with triphenyl phosphate (TPP)-based, nonflammable electrolytes for Li-ion batteries. Mesocarbon microbeads and LiCoO 2 were used as the anode and cathode materials, respectively. The main analysis tools were cyclic voltammetry, differential scanning calorimetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The results showed that the oxidizing potential of VEC and BP is about 4.9 and 4.6 V vs LilLi + , respectively, in TPP-containing electrolytes. Consequently, we found that the addition of 0.1 wt % BP to TPP-based electrolytes improved the cell performance and thermal stability of electrolytes for Li-ion batteries.

Polyimide/carbon black composite nanocoating layers as a facile surface modification strategy for high-voltage lithium ion cathode materials

Ion-conductive polyimide (PI)/electron-conductive carbon black (CB) composite nanocoating layers (referred to as “PI/CB coating layers”) are presented as a facile and scalable surface modification strategy for high-voltage lithium ion cathode materials (here, LiCoO2 (LCO) is chosen as a model system). The PI/CB coating layers exhibit a unique synergistic effect (i.e., boosted electronic conduction (from CB networks) in conjunction with suppression of unwanted interfacial side reactions between delithiated LCO and the liquid electrolyte (due to PI nanothin films)), which thus exerts a beneficial influence on the electrochemical performance and thermal stability of high-voltage cells.

Polarity-tuned Gel Polymer Electrolyte Coating of High-voltage LiCoO 2 Cathode Materials

We demonstrate a new surface modification of high-voltage lithium cobalt oxide () cathode active materials for lithium-ion batteries. This approach is based on exploitation of a polarity-tuned gel polymer electrolyte (GPE) coating. Herein, two contrast polymers having different polarity are chosen: polyimide (PI) synthesized from thermally curing 4-component (pyromellitic dianhydride/biphenyl dianhydride/phenylenediamine/oxydianiline) polyamic acid (as a polar GPE) and ethylene-vinyl acetate copolymer (EVA) containing 12 wt% vinyl acetate repeating unit (as a less polar GPE). The strong affinity of polyamic acid for allows the resulting PI coating layer to present a highly-continuous surface film of nanometer thickness. On the other hand, the less polar EVA coating layer is poorly deposited onto the , resulting in a locally agglomerated morphology with relatively high thickness. Based on the characterization of GPE coating layers, their structural difference on the electrochemical performance and thermal stability of high-voltage (herein, 4.4 V) is thoroughly investigated. In comparison to the EVA coating layer, the PI coating layer is effective in preventing the direct exposure of to liquid electrolyte, which thus plays a viable role in improving the high-voltage cell performance and mitigating the interfacial exothermic reaction between the charged and liquid electrolytes.

Characteristics of Lithium Secondary Batteries Using Li Salt-Organic Electrolyte as Function of Temperature

This study investigated characteristics of ICR18650 batteries with different electrolyte compositions in the range of . ICR18650 cells using electrolyte systems, which DMC and EMC solvent were added in electrolytes have high specific energy in the wide range of temperature. The specific energy of ICR18650 batteries using electrolyte at of room temperature, respectively.