Defect regulation of heterogeneous nickel-based oxides via interfacial engineering for long-life lithium-oxygen batteries

Ultralow Overpotential in Rechargeable Li-CO2 Batteries Enabled by Caesium Phosphomolybdate as an Effective Redox Catalyst

Rechargeable lithium-CO2 batteries are emerging as attractive energy storage devices due to their potential for high capacity and efficient CO2 reduction, making them promising candidates for post-lithium-ion batteries with high energy densities. However, their practical applications have been restricted by low reversibility, poor cycle life, and sluggish redox kinetics induced by the high potential required for decomposing the discharge product Li2CO3. Despite the various cathode catalysts explored, their application is often limited by availability, high cost, and complexity of synthesis. Herein, caesium phosphomolybdate (CPM) is synthesized through a facile and low-cost method. The Li‒CO2 battery based on the CPM cathode demonstrates a high discharge capacity of 15 440 mAh g-1 at 50 mA g-1 with 97.3% coulombic efficiency. It further exhibits robust stability, operating effectively over 100 cycles at 50 mA g-1 with a capacity limitation of 500 mAh g-1. Remarkably, the CPM catalyst yields a low overpotential of 0.67 V, surpassing most catalysts reported in prior research. This study reports, for the first time, the application of a Keggin-type polyoxometalate as a bifunctional redox catalyst, significantly improving the reversible cycling of rechargeable Li-CO2 batteries.

Coupling MoSe2 with Non-Stoichiometry Ni0.85 Se in Carbon Hollow Nanoflowers for Efficient Electrocatalytic Synergistic Effect on Li-O2 Batteries

Li-O2 batteries could deliver ultra-high theoretical energy density compared to current Li-ion batteries counterpart. The slow cathode reaction kinetics in Li-O2 batteries, however, limits their electrocatalytic performance. To this end, MoSe2 and Ni0.85 Se nanoflakes were decorated in carbon hollow nanoflowers, which were served as the cathode catalysts for Li-O2 batteries. The hexagonal Ni0.85 Se and MoSe2 show good structural compatibility with the same space group, resulting in a stable heterogeneous structure. The synergistic interaction of the unsaturated atoms and the built-in electric fields on the heterogeneous structure exposes abundant catalytically active sites, accelerating ion and charge transport and imparting superior electrochemical activity, including high specific capacities and stable cycling performance. More importantly, the lattice distances of the Ni0.85 Se (101) plane and MoSe2 (100) plane at the heterogeneous interfaces are highly matched to that of Li2 O2 (100) plane, facilitating epitaxial growth of Li2 O2 , as well as the formation and decomposition of discharge products during the cycles. This strategy of employing nonstoichiometric compounds to build heterojunctions and improve Li-O2 battery performance is expected to be applied to other energy storage or conversion systems.

Recent advances in heterostructured cathodic electrocatalysts for non-aqueous Li-O2 batteries

Developing efficient energy storage and conversion applications is vital to address fossil energy depletion and global warming. Li-O2 batteries are one of the most promising devices because of their ultra-high energy density. To overcome their practical difficulties including low specific capacities, high overpotentials, limited rate capability and poor cycle stability, an intensive search for highly efficient electrocatalysts has been performed. Recently, it has been reported that heterostructured catalysts exhibit significantly enhanced activities toward the oxygen reduction reaction and oxygen evolution reaction, and their excellent performance is not only related to the catalyst materials themselves but also the special hetero-interfaces. Herein, an overview focused on the electrocatalytic functions of heterostructured catalysts for non-aqueous Li-O2 batteries is presented by summarizing recent research progress. Reduction mechanisms of Li-O2 batteries are first introduced, followed by a detailed discussion on the typical performance enhancement mechanisms of the heterostructured catalysts with different phases and heterointerfaces, and the various heterostructured catalysts applied in Li-O2 batteries are also intensively discussed. Finally, the existing problems and development perspectives on the heterostructure applications are presented.

Rationalizing Surface Electronic Configuration of Ni-Fe LDO by Introducing Cationic Nickel Vacancies as Highly Efficient Electrocatalysts for Lithium-Oxygen Batteries

Cationic defect engineering is an effective strategy to optimize the electronic structure of active sites and boost the oxygen electrode reactions in lithium-oxygen batteries (LOBs). Herein, Ni-Fe layered double oxides enriched with cationic nickel vacancies (Ni-Fe LDO-V_Ni ) are first designed and studied as the electrocatalysts for LOBs. Based on the density functional theory calculation, the existence of nickel vacancy in Ni-Fe LDO-V_Ni significantly improves its intrinsic affinity toward intermediates, thereby fundamentally optimizing the formation and decomposition pathway of Li₂ O₂ . In addition, the number of e_g electrons on each nickel site is 1.19 for Ni-Fe LDO-V_Ni , which is much closer to 1 than 1.49 for Ni-Fe LDO. The near-unity occupation of e_g orbital enhances the covalency of transition metal-oxygen bonds and thus improves the electrocatalytic activity of Ni-Fe LDO-V_Ni toward oxygen electrode reactions. The experimental results show that the LOBs with Ni-Fe LDO-V_Ni electrode deliver low overpotentials of 0.11/0.29 V during the oxygen reduction reaction/oxygen evolution reaction, respectively, large specific capacities of 13 933 mA h g^-1 and superior cycling stability of over 826 h. This study provides a novel approach to optimize the electrocatalytic activity of LDO through reasonable defect engineering.

MnCo2 S4 -CoS1.097 Heterostructure Nanotubes as High Efficiency Cathode Catalysts for Stable and Long-Life Lithium-Oxygen Batteries Under High Current Conditions

Constructing the heterostructures is considered to be one of the most effective methods to improve the poor electrical conductivity and insufficient electrocatalytic properties of metal sulfide catalysts. In this work, MnCo2 S4 -CoS1.097 nanotubes are successfully prepared via a reflux- hydrothermal process. This novel cathode catalyst delivers high discharge/charge specific capacities of 21 765/21 746 mAh g-1 at 200 mA g-1 and good rate capability. In addition, a favorable cycling stability with a fixed specific capacity of 1000 mAh g-1 at high current density of 1000 mA g-1 (167 cycles) and 2000 mA g-1 (57 cycles) are delivered. It is proposed that fast transmission of ions and electrons accelerated by the built-in electric field, multiple active sites from the heterostructure, and nanotube architecture with large specific surface area are responsible for the superior electrochemical performance. To some extent, the rational design of this heterostructured metal sulfide catalyst provides guidance for the development of the stable and efficient cathode catalysts for Li-O2 batteries that can be employed under high current conditions.