Search

The applicable nickel-rich cathode materials (LiNi0.5Co0.2Mn0.3O2, NCM) under high cutoff voltage for high energy density lithium ion batteries shows a broad prospect, but creates enormous challenges for safety. In this work, the LiFePO4-coated LiNi0.5Co0.2Mn0.3O2(NCM-LFP) composites were prepared on a large scale by the high-speed dispersion and mechanical fusion method, attempting to improve the electrochemical performance and safety of pouch full cells worked under a high cutoff voltage of 4.5 V. Performances have been greatly enhanced, especially for the heat generation during the charge process: the temperature rise of a 5Ah NCM-LFP/MCMB (mesocarbon microbeads) pouch cell was 18.7°C, much lower than that of a NCM/MCMB pouch cell (42.7°C). Also, no thermal runaway was observed of NCM-LFP/MCMB pouch cells at 100% state of charge (SOC) during the extrusion and metallic nail penetration tests. The results of ex-situ impedance measurement, high magnification transmission electron microscope (HR-TEM) and in-situ X-Ray Diffraction (XRD) during heating revealed that the enhanced high voltage safety was contributed to the suppressed structure evolution from layer to spinel to rock salt, as a result of a dense and uniform LFP protective layer on NCM.

With the increasing development of energy storage, searching a suitable anode comes to be one of the hottest issues in lithium ion batteries. Li4Ti5O12owns the advantages of long discharge plateau, superior safety and so on, but suffering the low electron conductivity. In this work, a facile method with NF3for the fluorination of Li4Ti5O12is applied. Via this method, the enhanced rate performance and larger specific capacity of the fluorination Li4Ti5O12are obtained. All these results will provide an applicable modification of Li4Ti5O12materials, which can contribute a lot to the development of lithium ion batteries.