Enhancing the energy density of safer Li-ion batteries by combining high-voltage lithium cobalt fluorophosphate cathodes and nanostructured titania anodes

Recently, Li-ion batteries have been heavily scrutinized because of the apparent incompatibility between safety and high energy density. This work report a high voltage full battery made with TiO 2 /Li 3 PO 4 /Li 2 CoPO 4 F. The Li 2 CoPO 4 F cathode and TiO 2 anode materials are synthesized by a sol–gel and anodization methods, respectively. X-ray diffraction (XRD) analysis confirmed that Li 2 CoPO 4 F is well-crystallized in orthorhombic crystal structure with Pnma space group. The Li 3 PO 4 -coated anode was successfully deposited as shown by the (011) lattice fringes of anatase TiO 2 and (200) of γ-Li 3 PO 4 , as detected by HRTEM. The charge profile of Li 2 CoPO 4 F versus lithium shows a plateau at 5.0 V, revealing its importance as potentially high-voltage cathode and could perfectly fit with the plateau of anatase anode (1.8–1.9 V). The full cell made with TiO 2 /Li 3 PO 4 /Li 2 CoPO 4 F delivered an initial reversible capacity of 150 mA h g −1 at C rate with good cyclic performance at an average potential of 3.1–3.2 V. Thus, the full cell provides an energy density of 472 W h kg −1 . This full battery behaves better than TiO 2 /Li 2 CoPO 4 F. The introduction of Li 3 PO 4 as buffer layer is expected to help the cyclability of the electrodes as it allows a rapid Li-ion transport.