Interfacial Mn Vacancy for Li-Rich Mn-Based Oxide Cathodes

Abstract

Apart from the O releasing at a low rate, large polarization at a high rate is also a big challenge for Li-rich Mn-based oxide (LMO). Prussian blue (PB) with a specific redox potential is regarded as a suitable coating layer to overcome these drawbacks, while its stability is easily destroyed by the intrinsic Jahn−Teller effect after a long run. Herein, Mn vacancy (M V ) is introduced into the PB coating layer to enhance its stability. Consequently, such an electrode (M V -PB@LMO) presents a prolonged lifespan compared to the electrode with a PB coating layer only. Furthermore, it is found that the electrode with Mn vacancy in LMO (M V @ LMO) shows superior reversibility, which displays a boosted activity of LMO. This research exhibits the advanced merits of Mn vacancy for LMO, and further work may pay more attention to strengthening of the stability of M V @LMO.

Enabling Structural and Interfacial Stability via Coherent Interface Li3BO3 Coating for Lithium-Rich Manganese-Based Cathodes

“…The subsequent reductive peak at 3.2 V corresponds to the reduction of Ni 4+ /Ni 3+ and Co 4+/3+ . It is worth noting that the peak current (1.65 mA) of the LR@S@LBO-2% is smaller than that of the LR (1.70 mA) at 4.65 V is attributed to the Li 2 MnO 3 and the oxidation of O. − As is known to all, the O 2– oxidize to O 2 n – at high voltages, which is unstable forming O 2 release and promoting the migration and dissolution of TM (especially Mn 2+ ). , Therefore, the release of irreversible oxygen is suppressed after modification, which is attributed to the stronger Mn–O bonds of spinel . Additionally, the polarization voltage difference of LR@S@LBO-2% (0.8787 V) is also significantly smaller than that of LR (1.1281 V), which indicates that it can decrease the polarization and increase the diffusion of Li + after modification.…”

“…3−5 However, the lattice oxygen on the surface of LR is unstable and will be oxidized to O 2 and released, causing irreversible oxygen release, transition-metal ion migration, and phase transition. 6,7 Therefore, LR materials face challenges, including low initial coulomb efficiency (ICE), 8 poor rate performance, 9 and significant capacity decay, 10 severely impeding the practical application. Previous studies have shown that these issues originate from the surface of the LR materials and gradually penetrate the interior.…”

“…The rapid development of electric vehicles has resulted in a growing demand for improvements in lithium-ion batteries. , In particular, the upper limit of energy density for cathode materials is considered a primary constraint on the development of lithium-ion batteries. Among the cathode materials, the LR materials are regarded as the next generation of cathode electrode materials with high specific capacity (>250 mA h·g –1 ) and high-voltage anionic redox chemistry. − However, the lattice oxygen on the surface of LR is unstable and will be oxidized to O 2 and released, causing irreversible oxygen release, transition-metal ion migration, and phase transition. , Therefore, LR materials face challenges, including low initial coulomb efficiency (ICE), poor rate performance, and significant capacity decay, severely impeding the practical application. Previous studies have shown that these issues originate from the surface of the LR materials and gradually penetrate the interior .…”

In Situ Surface Reaction for the Preparation of High-Performance Li-Rich Mn-Based Cathode Materials with Integrated Surface Functionalization

“…The Li 2 MnO 3 phase controls the start and end potentials of LLO charge–discharge, and regardless of the LiTMO 2 phase’s stability and reversibility, the reversible capacity of LLO is influenced by the Li 2 MnO 3 phase. The A and C regions related to the Li 2 MnO 3 stage have substantially slower kinetics in contrast to the B region related to the LiTMO 2 phase . During each charging–discharging cycle, the voltage decay from the end of charging to the state after standing reflects the strength of the material polarization.…”

Modification Strategies and Challenges of High‐Performance Lithium‐Rich Manganese‐Based Cathode Materials

“…In addition to coating, various treatment methods can also be utilized to enhance the construction of new surface and interface structures, aiming to improve the efficiency of Li + transmission and minimize the release of O. Youchen Hao et al introduced the use of Mn vacancy and Prussian blue coating through an in situ complexation reaction between the complexing agent ethylenediaminetetraacetic acid disodium salt and metal elements. [ 67 ] This innovative approach resulted in a 20% capacity increase compare with the unimproved LRM and nearly doubled the cycle life. The application of Prussian blue significantly reduces the polarization of LRM at high rates and the release of O at low rates.…”