Enabling high rate charge and discharge capability, low internal resistance, and excellent cycleability for Li-ion batteries utilizing graphene additives

• Published in: Electrochimica acta 2018-05, Vol.273 (C), p.200-207
• Main Authors: Tsai, Hsiu-Ling, Hsieh, Chien-Te, Li, Jianlin, Gandomi, Yasser Ashraf
• Format: Article
• Language: English
• Subjects: Additives; Batteries; Charge transfer; Charging; Conductors; Diffusion coefficient; Discharge; Electric properties; Electrochemical analysis; Electrochemical impedance spectroscopy; Electrodes; ENERGY STORAGE; Fast charging; Graphene; Graphene nanosheets; Ion diffusion; Ions; Lithium; Lithium ion battery; Lithium-ion batteries; MATERIALS SCIENCE; NANOSCIENCE AND NANOTECHNOLOGY; Pouch cell; Rechargeable batteries; Sheets; Ternary cathode
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2018.03.154

A liquid-phase mixing method is adopted to uniformly disperse the graphene nanosheets onto LiNi1/3Co1/3Mn1/3O2 cathode for high-performance Li-ion batteries (LIBs). The electrochemical performance was characterized using a full pouch cells with state-of-the-art electrode areal loading (compared to half coin cells). The addition of graphene sheets (i.e., only 1 wt%) significantly improves the high rate capability for charging and discharging operation. For example, 6 times improvement in 5 C charging was achieved providing further insights in enabling extreme fast charging for LIBs. Other benefits include longer cycleability, lower internal resistance, and higher lithium ion diffusion coefficient, demonstrated by charge-discharge cycling tests and electrochemical impedance spectroscopy. Higher capacity retention of 88.2% and decreased internal resistance of ∼0.9 Ω are observed after 400 cycles. The diffusion coefficient of Li ions is 6.49 × 10−8 cm2 s−1 when charged to 4.2 V, which is approximately 1.37 times higher compared to the configuration with no graphene sheet (4.74 × 10−8 cm2 s−1). The improved performance is ascribed to a robust network among the active materials formed by graphene sheets, which serves as an extended current conductor and facilitates charge transfer, ionic reversibility, and ionic transportation. [Display omitted] •A liquid-phase mixing is used to disperse graphene nanosheets (GNs) onto cathode.•Soft-pack full cells are fabricated with GN/LiNi1/3Co1/3Mn1/3O2 (LNCM) cathode.•The GNs enhance rate capability, cycleability and electrical conductivity.•The cell shows high capacity retention and small resistance after 400 cycles.•The GNs serve as an extended conductor to form a network among LNCM crystals.