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Abstract: We demonstrate a simple method for enhancing the electrochemical performance of air electrodes of Li–air batteries using a polydopamine coating on the surface of carbon. A thin polydopamine layer on Ketjen black carbon clearly modified the surface properties of the air electrode, in turn resulting in improved electrolyte filling. The coating also passivates surface carbon defects, which may be helpful in suppressing parasitic reactions during cycling. Electrochemical tests of the electrode indicate that the introduction of the polydopamine layer is beneficial in that it increases the capacity, lowers the overpotential, and improves the cyclic performance of Li–air cells. These effects may be associated with the increased active catalytic area of the electrode, mostly resulting from the improved wetting characteristics. The suppression of parasitic reactions due to the passivation of carbon defects also contributes to the enhanced cyclic performance of the polydopamine-treated electrode. [Copyright &y& Elsevier]

Lots of lithium ion battery (LIB) products contain lithium metal oxide LiNi 5 Co 2 Mn 3 O 2 (LNCM) as positive electrode active material. To increase the conductivity, conductive carbon-based materials including acetylene black and carbon black become necessarily consisted in electrodes. Recently, carbon nano-tube (CNT) appears as a popular choice for conductive carbon in LIB. However, a large quantity of the conductive carbon which cannot provide capacity as the active material will decrease the energy density of batteries. The ultra-high cost of CNT comparing to conventional carbon black is also a problem. In this work, we are going to introduce 'short length' and 'long length' carbon nano-tube (S-CNT and L-CNT) into electrode in order to design a reduced-amount conductive carbon electrode. The whole experiment will be done in 1 Ah commercial type pouch LIB. By decreasing conductive carbon as well as increasing the active material in positive electrode, the energy density of LNCM-based 1Ah pouch type LIBs with only 0.16% of L-CNT inside LNCM positive electrode could reach 224 Wh/kg and 549 Wh/L, in weight and volume energy density, respectively. Also, this high energy density LIB with L-CNT reveals stable cyclability may become a valuable progress in portable devices and electric vehicle (EV) applications. [ABSTRACT FROM AUTHOR]

Solid-electrolyte interface (SEI) between the active material and the electrolyte is critically important to the electrochemical performance of a lithium-ion battery. In this work, a depth profile measurement of the SEI layer after prolonged electrochemical cycling is reported in order to quantify the influence of conducting additives in the development of this layer in mesocarbon microbeads (MCMB) electrodes. It is shown that the SEI in the electrodes having multiwalled carbon nanotubes (CNT) as conductive additive is primarily a multi-layered structure consisting of an outer organic layer near the electrolyte/SEI interface and an inner inorganic layer near the SEI/electrode interface. The chemical analysis of such electrodes exhibits that the inorganic layer is made up of compounds such as Li 2 O, LiF and Li 2 CO 3, while the outer layer consists mainly of organic carbonates, oligomers, traces of randomly distributed Li x PO y F z and undissociated LiPF 6. The chemical analysis of electrodes with carbon black (CB) as conducting additive reveals a similar composition of the outer layer, whereas the inner layer shows a relatively uniform molar amount of organic and inorganic carbonates and species like Li x PO y F z and Li x PO y , resulting in a porous SEI layer which as confirmed in AFM and SEM characterizations. On the other hand, the electrodes containing hybrid (CB-CNT) conducting additives show a relatively higher oligomer content than the electrodes with CNT only. The SEI formed on electrodes with CB-CNT as additives is shown to offer increased flexibility to accommodate partial strain generated due to volume change with narrow cracks exhibited in the SEM micrographs. Further, the variation in surface features and roughness augment the XPS findings. [ABSTRACT FROM AUTHOR]