Entropy Stabilization Strategy for Enhancing the Local Structural Adaptability of Li‐Rich Cathode Materials

Abstract

Layered Li‐rich cathode materials with high reversible energy densities are becoming prevalent. However, owing to the activation of low‐potential redox couples and the progressively irreversible structural transformation caused by the local adjustment of transition‐metal ions in the intra/interlayer driven by anionic redox, continuous capacity degradation, and voltage decay emerge, thus greatly reducing the energy density and increasing the difficulty of battery system management. Herein, layered Li‐rich cathode materials with higher intralayer configuration entropy have more local structural diversity and higher distortion energy, resulting in superior local structural adaptability with no drastic redox couple evolution, major local structural adjustment, or obvious layered‐to‐spinel phase transition. Consequently, the energy retention of the entropy‐stabilization‐strategy‐enhanced Li‐rich cathode materials is almost twice that of a typical Li‐rich cathode material (Li1.20Mn0.54Ni0.13Co0.13O2, T‐LRM) after 3 months of cyclic testing. Moreover, when cycled at 1 C, the voltage degradation per cycle is less than 0.02%, that is, it results in a voltage loss of only 0.8 mV per cycle, which is excellent performance. This study paves the way for the development of Li‐rich cathode materials with stabilized intralayer atomic arrangements and high local structural adaptability.

Recent advances in lithium-rich manganese-based cathodes for high energy density lithium-ion batteries

“…In addition, when the cycling temperature is 1 1C, the voltage loss per cycle is only 0.8 mV with less than 0.02% degradation per cycle. 269 Through introducing a small amount of nano-Li 3 PO 4 into the electrode, Wu et al successfully modified the electrode-electrolyte interface phase generated during the cyclic process improving the LRMO's electrochemical performance. 270 Applying mild heat energy to the circulating LRMO material restores the decayed voltage.…”

Fabricating Heterostructures for Boosting the Structure Stability of Li-Rich Cathodes

“…Li-rich Mn-based cathode materials have great advantages over other cathode materials due to their high operating voltage and high energy density. − The high capacity is mainly provided by the cation redox reaction and anion redox reaction. − At 2–4.45 V, the transition metal ions undergo reversible redox processes (Ni 2+ /Ni 4+ and Co 3+ /Co 4+ ) which are the cation redox reaction. − This process is often accompanied by transition metal migration, thus inducing phase transition. − At 4.45–4.8 V, lattice O undergoes a redox reaction to provide charge compensation, which is the anion redox reaction. − With irreversible O 2 loss, it leads to structure collapse, capacity degradation, and poor cycling performance. ,, The severe challenge of structural attenuation and capacity degradation in the electrochemical cycle also seriously hinders their practical application …”

“… 13 − 16 This process is often accompanied by transition metal migration, thus inducing phase transition. 17 − 22 At 4.45–4.8 V, lattice O undergoes a redox reaction to provide charge compensation, which is the anion redox reaction. 23 − 25 With irreversible O 2 loss, it leads to structure collapse, capacity degradation, and poor cycling performance.…”

Impact of Synthesis Chelation on the Crystallography and Capacity of Li-Rich Li1.2Ni0.13Mn0.54Fe0.13O2 Cathode Particles

“…The achieved level of activation of Li 2 MnO 3 on the first delithiation is predictive of the achieved steady-state cycling capacity. Some challenges impeding the commercialization of Li-rich oxides are voltage fade, , structural degradation, and irreversible oxygen loss . The performance of Li-rich oxides is influenced by several factors including particle size, crystallographic irregularities, and composite nanodomain distribution.…”