Lifting the energy density of lithium ion batteries using graphite film current collectors

Lightweight and highly conductive flexible films are attractive for a wide range of devices, especially replacing heavy metal-based current collectors, which can greatly reduce the weight of inactive materials in batteries and further enhance the energy density of energy storage devices. In this study, we first report a graphite film (GF) with ultralight weight (3.44 mg cm⁻²), high electrical conductivity (up to 1.07*10⁶ S m⁻¹), fast heat transport and excellent anti-wrinkle (300 times folding) properties. When used as current collector of half-cells, GF can enhance the rate property and long cycle durability of Li-ion batteries (LIBs) by reducing the contact resistance between active materials and current collector and buffering the stress during charge/discharge. By further employing GF current collectors to completely replace the Al and Cu foils at both sides of full cells, the electrode energy density of LiCoO₂‖Csi cell (4 mAh cm⁻²) is greatly boosted from 260 Wh kg⁻¹ to 332 Wh kg⁻¹. Moreover, such a GF film with excellent wrinkle resistance enables it to be used in flexible pouch cells with stable power output during various bending and distorting.