HEPES-Assisted Co-Precipitation Synthesis of LiNi0.5Mn1.5O4: Tuning the Mn3+ Content and Electrochemical Properties by pH Values

Spinel LiNi0.5Mn1.5O4 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 LiNi0.5Mn1.5O4 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 Mn3+ content in pure LNMO.

Automated summary

The LNMO material synthesized using HEPES buffer solution shows excellent electrochemical performance with a capacity retention of 95.8% and 88.9% after cycling at high rates, attributed to homogenous element distribution, stable pH, and suitable Mn3+ content.