A Novel and Flexible Laser Patterned Graphene Nanoplatelet Electrode With SPNs for Fast Charging Lithium-Ion Batteries

Abstract

A flexible anode was developed with graphene nanoplatelet (xGnP) as the anode material for fabricating fast charging lithium-ion battery. The ink consists of graphene nanoplatelets as active material along with C-45 carbon black as conductive additive and polyvinylidene fluoride (PVDF) as binder. The ink was bar coated on to two flexible copper films to form anodes with mass loadings of 2.8 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 7.2 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Then the anode was laser patterned to introduce secondary pore network (SPN) consisting of pores with a diameter of ~33 μm and an edge-to-edge distance of ~42 μm between the pores. The mass loadings of laser patterned anodes were measured to be 2.1 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 5.6 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Half-cell lithium-ion batteries was assembled with fabricated anodes with lithium metal foil as counter electrode. Ethylene carbonate and dimethyl carbonate (EC: DEC) in 50/50 (v/v) mixed with 1M lithium hexafluorophosphate (LiPF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ) was used as electrolyte in assembled coin-cells. Formation, rate and cycling tests were performed for bar-coated (without SPN) and laser patterned (with SPN) cells with different mass loadings at different C-rates. Cells with SPNs exhibited higher specific capacities of 420 mAh/g, 315 mAh/g and 207 mAh/g at high mass loading, at fast charging C-rates of 2C, 4C and 6C, respectively. Cells with SPNs showed superior capacity retention close to 90% when compared to cells without SPNs (38%) after 200 cycles at 2C-rate. Effect of SPN’s was significantly evident during rate and cycling performance of anodes at high mass loading. This study demonstrated the significance of implementing SPNs in the electrodes for achieving fast charging lithium-ion batteries with high mass loading.