Regulation of Surface Defect Chemistry toward Stable Ni‐Rich Cathodes

Abstract

Surface reconstruction of Ni‐rich layered oxides (NLO) degrades the cycling stability and safety of high‐energy‐density lithium‐ion batteries (LIBs), which challenges typical surface‐modification approaches to build a robust interface with electrochemical activity. Here, a strategy of leveraging the low‐strain analogues of Li‐ and Mn‐rich layered oxides (LMR) to reconstruct a stable surface on the Ni‐rich layered cathodes is proposed. The new surface structure not only consists of a gradient chemical composition but also contains a defect‐rich structure regarding the formation of oxygen vacancies and cationic ordering, which can simultaneously facilitate lithium diffusion and stabilize the crystal structure during the (de)lithiation. These features in the NLO lead to a dramatic improvement in electrochemical properties, especially the cyclability under high voltage cycling, exhibiting the 30% increase in capacity retention after 200 cycles at the current density of 1 C (3.0–4.6 V). The findings offer a facile and effective way to regulate defect chemistry and surface structure in parallel on Ni‐rich layered structure cathodes to achieve high‐energy density LIBs.

Facilitating reversible transition metal migration and expediting ion diffusivity via oxygen vacancies for high performance O3-type sodium layered oxide cathodes

“…But at the same time, the high precision of synthetic conditions and the high price of the doped elements (such as Ti and Mg) are worrisome, which have been identied as the decisive bottleneck issues for their sustainable practice and production. 16,17 In this context, it is high time to seek other tactics to redeem the inaccessible capacity of deeply charged Na x TMO 2 . Recently, the reports on Li-rich Mn-based cathodes and Ni-rich cathodes for LIBs that are meticulously designed with oxygen vacancies have provided outstanding prospects for the attainment of highvoltage stability.…”

“…Recently, the reports on Li-rich Mn-based cathodes and Ni-rich cathodes for LIBs that are meticulously designed with oxygen vacancies have provided outstanding prospects for the attainment of highvoltage stability. [17][18][19] The related studies indicate that the oxygen vacancies pre-formed on the surface have triple functions for stable high-voltage operation: (1) facilitate reversible TM cation migration in the bulk phase for inhibiting infaust phase transformation; (2) produce a pinning effect for riveting the dislocation motion and buffering the further structure deformation; (3) improve the electron/ion conductivity for ensuring sufficient electrons on high capacity of LIB cathodes. [20][21][22][23] Nonetheless, only a handful of reports shed light on the effect of oxygen vacancies in Na x TMO 2 cathodes for SIBs and the relevant interplay between oxygen vacancies and stable high-voltage operation is still in an infant stage.…”

Atomically Interlocked Chemistry Activated by Interstitial Sites in LiMn2O4 Cathode

“…This structural evolution could bring in the loss of oxygen and the increase of oxygen vacancy, followed by the collapse of surface crystal structure framework. [25] The peaks of Mn-L3 and Mn-L2 demonstrate a slight chemical shift towards lower energy loss from inside to surface for LMO, indicating Mn valence decreases from inside to surface (Figure 5h). [26] In contrast to the result above, the surface and interior part of the Al-LMO electrode exhibit a more uniform Mn valence state (Figure 5j).…”

Controllable vacancy strategy mediated by organic ligands of nickel fluoride alkoxides for high-performance aqueous energy storage

“…25,26 Unlike traditional template methods, energy storage precursors could serve as self-templates and vacancies are formed during the electrochemical reconstruction process. [27][28][29] Although true energy storage components can be reconstituted to yield more thermodynamically stable states, [30][31][32][33] the controllable modulation of vacancy content cannot be fully realized. Therefore, it is still urgent to develop controllable vacancy engineering toward energy conversion and storage.…”