Understanding and Control of Activation Process of Lithium-Rich Cathode Materials

Abstract

Lithium-rich materials (LRMs) are among the most promising cathode materials toward next-generation Li-ion batteries due to their extraordinary specific capacity of over 250 mAh g−1 and high energy density of over 1 000 Wh kg−1. The superior capacity of LRMs originates from the activation process of the key active component Li2MnO3. This process can trigger reversible oxygen redox, providing extra charge for more Li-ion extraction. However, such an activation process is kinetically slow with complex phase transformations. To address these issues, tremendous effort has been made to explore the mechanism and origin of activation, yet there are still many controversies. Despite considerable strategies that have been proposed to improve the performance of LRMs, in-depth understanding of the relationship between the LRMs’ preparation and their activation process is limited. To inspire further research on LRMs, this article firstly systematically reviews the progress in mechanism studies and performance improving attempts. Then, guidelines for activation controlling strategies, including composition adjustment, elemental substitution and chemical treatment, are provided for the future design of Li-rich cathode materials. Based on these investigations, recommendations on Li-rich materials with precisely controlled Mn/Ni/Co composition, multi-elemental substitution and oxygen vacancy engineering are proposed for designing high-performance Li-rich cathode materials with fast and stable activation processes. Graphical abstract The “Troika” of composition adjustment, elemental substitution, and chemical treatment can drive the Li-rich cathode towards stabilized and accelerated activation.

Surface Miscible Structure Modulation of Li‐Rich Cathodes by Dual Gas Surface Treatment for Super High‐Temperature Electrochemical Performance

“…Moreover, as an important component of LIBs, cathode materials account for more than 30% of the total cost of batteries. [ 1–5 ] Compared with olivine LiFePO 4 cathodes, spinel Li 2 MnO 4 cathode and traditional layered oxide cathode materials (LiTMO 2 , TM = Ni, Co, Mn), Li‐rich Mn‐based layer oxides ( x LiTMO 2 ·(1 − x )Li 2 MnO 3 , LRNCM) with high specific capacity (≧250 mAh g −1 ), high voltage (4.8 V), and low cost are becoming one of the key electrode materials for high‐energy‐density batteries. [ 6–9 ] The ultrahigh capacity is derived from the active reaction of oxygen at high voltage, including the reversible oxygen redox processes (O 2− to O n − , n < 2) and irreversible O 2 loss.…”

Role of Substitution Elements in Enhancing the Structural Stability of Li-Rich Layered Cathodes

“…The first charge (gray) curve can be divided into two regions. Region 1 below 4.5 V is associated with the oxidation of cations (Ni 2+ ), and region 2 is the potential plateau from approximately 4.5 to 4.8 V corresponding to the oxidation of anions (O 2– ). , The amount of Li + extracted from the three samples in region 1 is around 0.3 mol, indicating that the substitution of 4% Mg 2+ /Ti 4+ for Ni 2+ /Mn 4+ has a negligible effect on the Ni charge compensation. For region 2, in contrast, a clear difference appears, with 0.73 mol Li + uptake from the LNMO structure, approximately 0.65 mol Li + from Mg-LNMO, and 0.58 mol Li + extracted from the Ti-LNMO cathode.…”

Recent progress and perspectives on cation disordered rock-salt material for advanced Li-ion batteries

“…During the past decades, anionic redox chemistry was proposed in the LIBs, which introduced Li in the TM layered to activate O redox by the Li-O-Li conguration. 13,14 Nevertheless, the lithium retained diffusion behaviour upon cycling for the Li-excess compound (Fig. 1c).…”