Uncommon Behavior of Li Doping Suppresses Oxygen Redox in P2‐Type Manganese‐Rich Sodium Cathodes

Abstract

Utilizing both cationic and anionic oxygen redox reactions is regarded as an important approach to exploit high‐capacity layered cathode materials with earth abundant elements. It has been popular strategies to effectively elevate the oxygen redox activities by Li‐doping to introduce unhybridized O 2p orbitals in NaxMnO2‐based chemistries or enabling high covalency transition metals in P2‐Na0.66MnxTM1−xO2 (TM = Fe, Cu, Ni) materials. Here, the effect of Li doping on regulating the oxygen redox activities P2‐structured Na0.66Ni0.25Mn0.75O2 materials is investigated. Systematic X‐ray characterizations and ab initio simulations have shown that the doped Li has uncommon behavior in modulating the density of states of the neighboring Ni, Mn, and O, leading to the suppression of the existing oxygen and Mn redox reactivities and the promotion of the Ni redox. The findings provide a complementary scenario to current oxygen redox mechanisms and shed lights on developing new routes for high‐performance cathodes.

Hysteresis‐Suppressed Reversible Oxygen‐Redox Cathodes for Sodium‐Ion Batteries

“…In this work, we calculated and analyzed magnetic moment (represented simply by N unp ) of elements to show clearly what ions and how much they are oxidized. Our calculated magnetic moments indicated relatively a lower oxygen redox activity in P2-Na 0.75 [Li 0.15 Ni 0.15 Mn 0.7 ]O 2 compared to P2-Na 0.67 [Li 0.22 Mn 0.78 ]O 2 in the range of 1.5-4.6 V. Xiao et al [16] found that Li substitution suppresses the oxygen redox activity in P2-Na 0.66 Ni 0.25 Mn 0.75 O 2 in the range of 1.5-4.4 V. Please note that in our work we studied the effect of Ni substitution on P2-Na 0.67 [Li 0.22 Mn 0.78 ]O 2 and found a mechanism that Ni substitution suppresses the migration of Li ions from TM to the Na layer (and then surface) and thereby oxidation of oxygen.…”

“…[8][9][10] Interestingly, such oxygen behavior is also applicable to not only Na-rich cathodes, [11][12][13] which are an analog of Li-rich materials, but also Na-deficient TM oxides. [14][15][16][17][18][19][20][21] The Na-rich compounds are mainly based on noble and expensive TMs, such as 4d (Ru) and 5d (Ir) metals; [22][23][24] however, Na-deficient materials (P2 and P3) are represented by abundant and low-cost 3d (Mn). [15,16] There is a universal notation for oxygen redox:…”

“…[14][15][16][17][18][19][20][21] The Na-rich compounds are mainly based on noble and expensive TMs, such as 4d (Ru) and 5d (Ir) metals; [22][23][24] however, Na-deficient materials (P2 and P3) are represented by abundant and low-cost 3d (Mn). [15,16] There is a universal notation for oxygen redox:…”

Biomimetic manganese-based theranostic nanoplatform for cancer multimodal imaging and twofold immunotherapy

“…Manganese, an essential metal element for human body, is one of the most commonly used materials in design and synthesis of multifunctional cancer theranostics agent [ 9 , 10 ]. For instance, manganese dioxide (MnO 2 ) is commonly used as a catalase to eliminate hydrogen peroxide (H 2 O 2 ) and produce ROS to kill cancer cells via the released manganese ions (Mn 2+ ) inducing Fenton-like reaction in TME [ 11 ]. Mechanism research revealed that PTT and CDT could improve anti-tumor immunity via inducing immunogenic cell death (ICD) of tumor cells accompanied by the expression Calreticulin (CRT) and the release of high-mobility group box 1 (HMGB1) as well as ATP [ 12 ].…”

Tailoring Ultrafast and High‐Capacity Sodium Storage via Binding‐Energy‐Driven Atomic Scissors

“…Sodium-ion batteries (SIBs) have drawn significant attention as a promising nextgeneration energy storage technology as a result of the large reserves and comparatively low cost of Na metal. [1][2][3][4][5][6] Given significant developments in open framework materials with kinetically favorable Na storage channels as SIB cathodes, [7][8][9][10][11][12][13] the concomitant development of advanced anodes possessing high capacities and rate capabilities is essential to enable the widespread implementation of SIBs. Among the various candidates, Ge, which has a bandgap of only 0.66 eV at 300 K, has become increasingly prominent as an anode material for sodium storage, owing to its remarkable electrical conductivity (≈100 times higher than that of Si), [14] high theoretical capacity (Na 3 Ge: 1108 mAh g −1 , NaGe: 369 mAh g −1 ), [15,16] rapid Na + transport properties, and superior mechanical strength.…”