Synthesis of /Single-Walled Carbon Nanotubes Integrated into Nanostructured Composites as Cathode Materials in High Performance Lithium-Ion Batteries

Vanadium pentoxide (V2O5)-anchored single-walled carbon nanotube (SWCNT) composites have been developed through a simple sol–gel process, followed by hydrothermal treatment. The resulting material is suitable for use in flexible ultra-high capacity electrode applications for lithium-ion batteries. The unique combination of V2O5 with 0.2 wt.% of SWCNT offers a highly conductive three-dimensional network. This ultimately alleviates the low lithium-ion intercalation seen in V2O5 itself and facilitates vanadium redox reactions. The integration of SWCNTs into the layered structure of V2O5 leads to a high specific capacity of 390 mAhg−1 at 0.1 C between 1.8 to 3.8 V, which is close to the theoretical capacity of V2O5 (443 mAhg−1). In recent research, most of the V2O5 with carbonaceous materials shows higher specific capacity but limited cyclability and poor rate capability. In this work, good cyclability with only 0.3% per cycle degradation during 200 cycles and enhanced rate capability of 178 mAhg−1 at 10 C have been achieved. The excellent electrochemical kinetics during lithiation/delithiation is attributed to the chemical interaction of SWCNTs entrapped between layers of the V2O5 nanostructured network. Proper dispersion of SWCNTs into the V2O5 structure, and its resulting effects, have been validated by SEM, TEM, XPS, XRD, and electrical resistivity measurements. This innovative hybrid material offers a new direction for the large-scale production of high-performance cathode materials for advanced flexible and structural battery applications.

Influence of Al2O3 Coatings on HF Induced Transition Metal Dissolution from Lithium-Ion Cathodes

Transition metal (TM) dissolution from oxide cathode materials is a major challenge limiting the performance of modern Li-ion batteries. Coating the cathode materials with thin protective layers has proved to be a successful strategy to prolong their lifetime. Yet, there is a lack of fundamental understanding of the working mechanisms of the coating. Herein, the effect of the most commonly employed coating material, Al2O3, on suppressing hydrofluoric acid(HF)-induced TM dissolution from two state-of-the-art cathode materials, LiMn2O4 and LiNi0.8Mn0.1Co0.1O2, is investigated. Karl Fischer titration, fluorine selective probe and inductively coupled plasma optical emission spectrometry are coupled to determine evolution of H2O, HF and TM concentrations, respectively, when the active materials come in contact with the aged electrolyte. The coating reduces the extent of TM dissolution, in part due to the ability of Al2O3 to scavenge HF and reduce the acidity of the electrolyte. Delithiation of the cathode materials, however, increase the extent of TM dissolution, likely because of the higher vulnerability of surface TMs in +IV oxidation state towards HF attack. In conclusion, the current study evidences the important role of acid-base reactions in governing TM dissolution in Li-ion batteries and shows that coatings protect the cathode towards an acidic electrolyte.