Electrolytes and interphases in Li-ion batteries and beyond.

Recent developments in cathode materials for lithium ion batteries

Lithium-excess manganese layered oxides, which are commonly described by the chemical formula zLi2MnO3−(1 − z)LiMeO2 (Me = Co, Ni, Mn, etc.), are of great importance as positive electrode materials for rechargeable lithium batteries. In this Article, LixCo0.13Ni0.13Mn0.54O2−δ samples are prepared from Li1.2Ni0.13Co0.13Mn0.54O2 (or 0.5Li2MnO3−0.5LiCo1/3Ni1/3Mn1/3O2) by an electrochemical oxidation/reduction process in an electrochemical cell to study a reaction mechanism in detail before and after charging across a voltage plateau at 4.5 V vs Li/Li+. Changes of the bulk and surface structures are examined by synchrotron X-ray diffraction (SXRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (SIMS). SXRD data show that simultaneous oxygen and lithium removal at the voltage plateau upon initial charge causes the structural rearrangement, including a cation migration process from metal to lithium layers, which is also supported ...

Detailed Studies of a High-Capacity Electrode Material for Rechargeable Batteries, Li2MnO3−LiCo1/3Ni1/3Mn1/3O2

Ni-rich layered oxides and Li-rich layered oxides are topics of much research interest as cathodes for Li-ion batteries due to their low cost and higher discharge capacities compared to those of LiCoO2 and LiMn2O4. However, Ni-rich layered oxides have several pitfalls, including difficulty in synthesizing a well-ordered material with all Ni3+ ions, poor cyclability, moisture sensitivity, a thermal runaway reaction, and formation of a harmful surface layer caused by side reactions with the electrolyte. Recent efforts towards Ni-rich layered oxides have centered on optimizing the composition and processing conditions to obtain controlled bulk and surface compositions to overcome the capacity fade. Li-rich layered oxides also have negative aspects, including oxygen loss from the lattice during first charge, a large first cycle irreversible capacity loss, poor rate capability, side reactions with the electrolyte, low tap density, and voltage decay during extended cycling. Recent work on Li-rich layered oxides has focused on understanding the surface and bulk structures and eliminating the undesirable properties. Followed by a brief introduction, an account of recent developments on the understanding and performance gains of Ni-rich and Li-rich layered oxide cathodes is provided, along with future research directions.

Nickel-Rich and Lithium-Rich Layered Oxide Cathodes: Progress and Perspectives

Pristine Li-rich layered cathodes, such as Li1.2Ni0.2Mn0.6O2 and Li1.2Ni0.1Mn0.525Co0.175O2, were identified to exist in two different structures: LiMO2R3m and Li2MO3C2/m phases. Upon 300 cycles of charge/discharge, both phases gradually transform to the spinel structure. The transition from LiMO2R3m to spinel is accomplished through the migration of transition metal ions to the Li site without breaking down the lattice, leading to the formation of mosaic structured spinel grains within the parent particle. In contrast, transition from Li2MO3C2/m to spinel involves removal of Li+ and O2-, which produces large lattice strain and leads to the breakdown of the parent lattice. The newly formed spinel grains show random orientation within the same particle. Cracks and pores were also noticed within some layered nanoparticles after cycling, which is believed to be the consequence of the lattice breakdown and vacancy condensation upon removal of lithium ions. The AlF3-coating can partially relieve the spinel f...

Formation Of The Spinel Phase In The Layered Composite Cathode Used In Li-Ion Batteries

National Basic Research Program of China (973 Program) [2007CB209702]; National Natural Science Foundation of China (NNSFC) [20433060, 20473068, 29925310]

https://iopscience.iop.org/article/10.1149/1.2966694/pdf

X. B. Wu

Papers

The Effects of AlF3 Coating on the Performance of Li [ Li0.2Mn0.54Ni0.13Co0.13 ] O2 Positive Electrode Material for Lithium-Ion Battery