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Li-rich cathode materials are attracting widespread attention owing to their advantages such as high specific capacity and operating voltage. However, irreversible lattice oxygen loss and structural distortion hinder their further commercial application. Herein, a threefold modification strategy with LiVO3surface coating and Na and V dual-cation doping has been utilized to boost the electrochemical performance of Li-rich oxides Li1.2Mn0.54Co0.13Ni0.13O2, which is achieved simply by introducing NaVO3treatment. The LiVO3surface coating prevents interfacial side reactions, promotes Li-ion diffusion kinetics in the interphase, and inhibits irreversible O2release. Additionally, the Na and V dual-cation doping in the bulk can also contribute to boosting Li-ion transfer and restrain irreversible O2evolution. Na-ion doping with the pillar effect expands the lattice space for faster Li-ion intercalation/deintercalation, and V-ion doping by forming stronger V–O bonds further strengthens structural stability. Therefore, the treated Li-rich sample exhibits extended cycle durability and stable voltage stability, with an 82.4% capacity retention rate after 250 cycles and an average voltage fading of 2.4 mV per cycle at 2 C. Moreover, a pouch cell based on the modified Li1.2Mn0.54Co0.13Ni0.13O2@LiVO3cathode presents an outstanding cyclability, maintaining 80.4% of its initial capacity after 400 cycles at 1 C. Our results demonstrate a promising strategy for addressing the issues of Li-rich cathode materials.

As an important Co-free and Ni-rich layered oxide, LiNi0.9Mn0.1O2(NM91) has garnered significant interest as a promising cathode material for lithium-ion batteries. Despite its attractively high specific capacity, the intrinsic structural instability poses a great challenge to its electrochemical performances, especially cycling performance. In this work, we circumvent the structural instability issue of NM91 through high-valence Nb doping. Our findings reveal that high-valence Nb5+dopants were successfully incorporated into the lattice of LiNi0.9Mn0.1O2, functioning as interlayer pillars that reinforce the structure and mitigate the detrimental H2 → H3 phase transition. This results in greatly improved cycling stability and rate capability of the cathode. The discharge capacities of 1%Nb-NM91 reached 211.8 mA h g–1at 0.1 C and 159.3 mA h g–1at 5 C, with a retention rate of 95.6% after 100 cycles at 0.5 C, even superior to the previously reported lower Ni content counterparts, including LiNi0.8Co0.15Al0.05O2, LiNi0.8Co0.1Mn0.1O2, and so forth. This study demonstrates that high-valence Nb doping is a promising strategy to overcome the structural instability issue in LiNi0.9Mn0.1O2and underscores the potential of Co-free Ni-rich layered oxides as cathode materials for lithium-ion batteries.

Owing to the capacity boost from anion redox activities, cation-disordered rock-salt oxides are considered as potential candidates for the next-generation of high energy density Li-ion cathode materials. Unfortunately, the anion redox process that affords ultra-high specific capacity often triggers irreversible O2release, which brings about structural degradation and rapid capacity decay. In this study, we present a partial chlorine (Cl) substitution strategy to synthesize a new cation-disordered rock-salt compound of Li1.225Ti0.45Mn0.325O1.9Cl0.1and investigate the impact of Cl substitution on the oxygen redox process and the structural stability of cation-disordered rock-salt cathodes. We find that partial replacement of O2–by Cl–expands the cell volume and promotes anion redox reaction reversibility, thus increasing the Li+ion diffusion rate and suppressing irreversible lattice oxygen loss. As a result, the Li1.225Ti0.45Mn0.325O1.9Cl0.1cathode exhibits significantly improved cycling durability at high current densities, compared with the pristine Li1.225Ti0.45Mn0.325O2cathode. This work demonstrates the promising feasibility of the Cl substitution process for advanced cation-disordered rock-salt cathode materials.

Layered metal vanadates with intercalation pseudocapacitive behaviors show great promise for applications in sodium-ion hybrid capacitor anode materials due to their large interlayer distances, which benefit the fast Na+solid-state diffusion. However, their charge storage capacity is significantly constrained by the limited available sites that allow the intercalation of Na+ions. In this work, by engineering the interlayer cations, Ni0.12Zn0.2V2O5·1.07H2O is designed as a high-performance anode material in sodium-ion hybrid capacitors. The Ni/Zn codoping in the layered vanadate leads to the integration of high rate capability and high specific capacity. Specifically, the spacious interlayer spacing and the pillaring effects of Zn ions together lead to the high rate performance and decent cycling stability, while the redox reactions of the interlayer Ni ions efficiently upgrade the charge storage capacity of this layered material. Accordingly, this work offers a promising avenue to further optimizing the Na+storage performance of layered vanadates via interlayer-cation engineering.

An effective lactic acid-assisted interface engineering strategy is designed to regulate the surface chemistry and properties of Ni-rich LiNi0.8Co0.1Mn0.1O2cathode material.

Cation-disordered rock-salt cathode materials are featured by their extraordinarily high specific capacities in lithium-ion batteries primarily contributed by anion redox reactions. Unfortunately, anion redox reactions can trigger oxygen release in this class of materials, leading to fast capacity fading and major safety concern. Despite the capability of absorbing structural distortions, high-ratio d0transition-metal cations are considered to be unfavorable in design of a new cation-disordered rock-salt structure because of their electrochemically inactive nature. Herein, we report a new cation-disordered rock-salt compound of Li1.2Ti0.6Mn0.2O2with the stoichiometry of Ti4+as high as 0.6. The capacity reducing effect by the low-ratio active transition-metal center can be balanced by using a Mn2+/Mn4+two-electron redox couple. The strengthened networks of strong Ti–O bonds greatly retard the oxygen release and improve the structural stability of cation-disordered rock-salt cathode materials. As expected, Li1.2Ti0.6Mn0.2O2delivers significantly improved electrochemical performances and thermal stability compared to the low-ratio Ti4+counterpart of Li1.2Ti0.4Mn0.4O2. Theoretical simulations further reveal that the improved electrochemical performances of Li1.2Ti0.6Mn0.2O2are attributed to its lower Li+diffusion energy barrier and enhanced unhybridized O 2p states compared to Li1.2Ti0.4Mn0.4O2. This concept might be helpful for the improvement of structural stability and electrochemical performances of other cation-disordered rock-salt metal oxide cathode materials.