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

A flexible anode was developed with graphene nanoplatelet (xGnP) as the anode material for fabricating fast-charging lithium-ion batteries. The ink consists of xGnPs as active material along with C-45 carbon black as a conductive additive and polyvinylidene fluoride (PVDF) as a binder. The ink was bar coated onto two flexible copper films to form anodes with mass loadings of 2.8 and 7.2 mg/cm
²
. Then the anode was laser patterned to introduce a secondary pore network (SPN) consisting of pores with a diameter of
$\sim 33 \mu \text{m}$
and an edge-to-edge distance of
$\sim 42 \mu \text{m}$
between the pores. The mass loadings of laser-patterned anodes were measured to be 2.1 and 5.6 mg/cm
²
. Half-cell lithium-ion batteries (LIBs) were assembled with fabricated anodes with lithium metal foil as a counter electrode. Ethylene carbonate and diethyl carbonate (EC:DEC) in 50/50 (v/v) mixed with 1M lithium hexafluorophosphate (LiPF6) was used as an 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, 315, and 207 mAh/g at high mass loading, at fast charging C-rates of 2, 4, and 6 C, respectively. Cells with SPNs showed superior capacity retention close to 90% when compared to cells without SPNs (38%) after 200 cycles at 2 C-rate. The effect of SPNs was significantly evident during the 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 LIBs with high mass loading.