Key issues for the next generation of Li-Ion batteries are increasing the specific energy and reducing the cell cost. It is possible to achieve both this targets by adopting innovative and cheap cathode materials presenting either higher capacity or higher operating potential than standard cathode materials. Among the high voltage materials, LiNi_0.5Mn_1.5O₄ (LMNO) is one of the most promising candidates for Li-Ion cells application because of its operating potential of 4.7 V vs. Li/Li⁺, its good specific capacity (147 mAh g^-1) and low cost. Graphite/LMNO cells guarantee considerable improvements in the specific energy of Li-Ion batteries by increasing the cell operating voltage to ca. 4.6 V. Unfortunately Graphite/LMNO systems undergo a strong aging process and a rapid capacity fade because of the electrolyte degradation reactions occurring at high potential. Thus, it is necessary to adopt different strategies such as the optimization of the active material, the adoption of coatings and the optimization of the electrolyte in order to stabilize the cathode/electrolyte interface. Adopting these strategies, it was possible to significantly increase the cycling life of Graphite/LMNO cells up to more than 700 cycles (Figure).

The development of stable Graphite/LMNO cells starts with the optimization of the cathode active material. Thus, we studied and tailored morphological properties of LMNO such as particle architecture, composition, crystallite size and particle size. This study aimed to realize an optimized LMNO, presenting features in line with commercial cathode materials and the best compromise between electrochemical performance and reduced electrolyte degradation. The optimized LMNO in full-cells vs. graphite anodes showed remarkable electrochemical performance and a stable reversible capacity for more than 300 cycles.

Additional strategies for improving the cycling life of Graphite/LMNO cells included a facile oxidic treatment of the LMNO particles surface. The aim of this treatment was to further stabilize the cathode/electrolyte interface without altering the electrochemical performance of the active material. Moreover, we pointed out the importance of using a suitable electrolyte composition, which guarantees high voltage stability without interfering with the performances of the full-cells. Electrochemical studies in full-cells showed a significant contribution of these improvements to the cycling stability of Graphite/LMNO cells and the validity of the adopted strategies.