HEPES-Assisted Co-Precipitation Synthesis of LiNi <sub>0.5</sub> Mn <sub>1.5</sub> O <sub>4</sub> : Tuning the Mn <sup>3+</sup> Content and Electrochemical Properties by pH Values
Jiliang Wu, Hui Li, Yutao Liu, Yu Ye, Yifu Yang
Abstract
Spinel LiNi 0.5 Mn 1.5 O 4 material (LNMO) is now actively developed as a promising cathode for next generation lithium-ion batteries due to its high specific energy, high rate capability, high operating potential, and low cost. However, its performance degradation originating from transition metal dissolution and severe side reactions remains a critical challenge. Herein, a new solution system 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) buffer solution for the synthesis of the spinel LiNi 0.5 Mn 1.5 O 4 material is reported, which is not only the pH stabilizer, but also the chelating agent. The obtained LNMO exhibits excellent electrochemical performance, and its capacity retention is kept as 95.8%, and 88.9% after cycled at 5 C and 10 C for 1000 times, respectively. These can be attributed to homogenous distributions of elements in the as-prepared carbonate precursors, stable pH value of reaction base solution and suitable Mn 3+ content in pure LNMO.