Impact of Cr Doping on the Voltage Fade of Li-Rich Mn-Rich Li1.11Ni0.33Mn0.56O2 and Li1.2Ni0.2Mn0.6O2 Positive Electrode Materials

Abstract

Voltage fade during charge-discharge cycling in Layered Li-rich Mn-rich positive electrode materials needs to be overcome for the development of high-energy low cost Li-ion batteries. Several cation dopants have been introduced into the bulk lattice to mitigate voltage decay by limiting transition metal (TM) migration, inhibiting phase transformation, or reducing the extent of oxygen release. Here, a series of electrochemically active Cr substituted (2.5, 5.0, and 10 mol%) Co-free Li1.11Ni0.33Mn0.56O2 and Li1.2Ni0.2Mn0.6O2 compositions were synthesized via dry particle fusion followed by heat treatment with Li2CO3. Cr doping improves specific capacity and capacity retention via multiple electron transfer of Cr3+/Cr6+ as well as mitigates voltage fading to a certain extent. The impact of Cr on voltage decay was studied by careful measurements of dQ/dV vs V on Cr-doped and undoped samples before and after cycle testing.