Malachi Noked

Developing high-performance cathode materials is crucial for advancing grid-scale sodium-ion batteries (SIBs). Here, we introduce a P2-type layered oxide cathode material, Na0·67Ni0·33Mn0·51Ru0·16O2, which demonstrates exceptional electrochemical performance through a robust dual cationic–anionic redox mechanism. This material delivers a high discharge capacity of 175.6 mAh g−1 at an average voltage of 3.6 V and maintains remarkable cycling stability with ∼93% capacity retention after 1000 cycles. A key to this performance is the strategic Ru doping, which plays a pivotal role in electronically stabilizing the oxidized oxygen states. By mediating the reversible formation of oxygen holes and preventing oxygen undercoordination, the Ru dopant stabilizes the anionic redox process. Unlike Na-rich layered oxides, this ligand-to-metal charge-transfer mechanism effectively suppresses detrimental oxygen evolution and preserves the structural integrity of the layered Na-deficient P2-type framework. This design strategy enables a synergistic redox landscape, confirmed by ex situ and operando advanced characterizations and theoretical calculations such as Fukui functions, offering critical insights into the rational design of high-capacity cathode for next-generation SIBs.

Sodium-ion batteries are promising energy storage devices beyond Li-ion batteries; however, their cycling stability is limited by chemomechanical instabilities in transition-metal oxide cathodes. Although electrolyte additives and other surface modification strategies have been widely used to improve electrochemical performance, the mechanisms underlying these improvements remain poorly understood. Here, sodium chromium oxide (NaCrO2) and fluoroethylene carbonate (FEC) were selected as model cathode and electrolyte additive systems, respectively. FEC improved the capacity retention of the NaCrO2 cathode from 66% to 85% after 50 cycles at C/20 rate. Operando digital image correlation (DIC), together with ex situ X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD) techniques, was employed to investigate the mechanical, chemical, and structural evolution of the NaCrO2 cathode. The cathode exhibited nearly identical chemomechanical deformations and phase evolution regardless of FEC except during the first charge, where a distinct deformation response indicated the interfacial reconstruction associated with cathode-electrolyte interphase formation. XPS, FTIR, and HR-TEM measurements demonstrated the formation of a thinner, more uniform NaF-rich cathode-electrolyte interphase with improved preservation of surface Cr3+ species in the presence of FEC. Additional XPS analysis of the Na-metal anode revealed NaF-rich solid-electrolyte interphase formation in the presence of the FEC additive. The enhanced cycling stability of the NaCrO2 cathode against the Na-metal anode is primarily attributed to the cohesive impact of the improvement in chemical stability of the electrodes’ interphases rather than bulk chemomechanical deformations of the cathode alone at a slower rate. The operando mechanical measurements revealed a unique mechanical signature associated with interfacial reconstruction in the presence of FEC, providing a direct mechanistic link between interphase formation and electrochemical performance.

Persistent anionic N‐centered radicals are exceptionally rare, as the coexistence of negative charge and unpaired electron density typically promotes protonation, aggregation, and irreversible redox chemistry. Here we introduce mesoionic 1,2,3‐triazines as a platform for stabilizing such elusive open‐shell anions. These compounds undergo clean and reversible one‐electron reduction to generate negatively charged nitrogen‐centered radicals, and suitable substitution enables their isolation as crystalline salts. EPR spectroscopy, single‐crystal x‐ray diffraction, and computational analysis reveal dominant nitrogen spin localization together with reduction‐induced structural changes consistent with occupation of a parent triazine antibonding orbital. The resulting anionic radicals display chemically clean electron‐transfer behavior and are reversibly oxidized to their zwitterionic precursors. These findings further highlight the potential of mesoionic 1,2,3‐triazines as redox‐active molecular platforms for applications in complex electrochemical environments.

Persistent anionic N‐centered radicals are exceptionally rare, as the coexistence of negative charge and unpaired electron density typically promotes protonation, aggregation, and irreversible redox chemistry. Here we introduce mesoionic 1,2,3‐triazines as a platform for stabilizing such elusive open‐shell anions. These compounds undergo clean and reversible one‐electron reduction to generate negatively charged nitrogen‐centered radicals, and suitable substitution enables their isolation as crystalline salts. EPR spectroscopy, single‐crystal x‐ray diffraction, and computational analysis reveal dominant nitrogen spin localization together with reduction‐induced structural changes consistent with occupation of a parent triazine antibonding orbital. The resulting anionic radicals display chemically clean electron‐transfer behavior and are reversibly oxidized to their zwitterionic precursors. These findings further highlight the potential of mesoionic 1,2,3‐triazines as redox‐active molecular platforms for applications in complex electrochemical environments.

Li(MnxFe1–x)PO4 (LMFP) is a Co/Ni free, 4 V class cathode material for cost-sensitive electric vehicles and grid-scale energy storage. However, fully accessing its capacity and energy density requires ≥4.5 V operation, which accelerates electrolyte oxidation and Mn/Fe dissolution, driving impedance growth, voltage fade, and capacity loss. In this work, LMFP powder is rationally engineered with a conformal ZnF2 coating via atomic layer deposition (ALD), and its electrochemistry is comprehensively investigated. Under demanding cycling conditions (1000 cycles, 2.5–4.5 V vs Li/Li+; discharge @1C and 5C), the LMFP@ZnF2 cathode demonstrates >22% higher capacity retention than its pristine counterpart. Postmortem analyses reveal that ZnF2 encapsulation facilitates the formation of a thin, uniform, and F-, Li-, and P-enriched cathode–electrolyte interphase (CEI) that preserves the Mn/Fe stoichiometry and mitigates particle pulverization. Compared to the organic-rich CEI in the pristine-LMFP cathode, the robust inorganic-dominated CEI in LMFP@ZnF2 was found to be instrumental in promoting high-voltage stability and mechanical integrity of the cathode. Overall, this research presents a scientifically grounded and industry-relevant strategy for stabilizing LMFP-cathode operation at high voltages and aligns with global sustainability goals.

Lithium nickel oxide (LNO) is a promising cathode material for next‐generation high‐energy‐density lithium‐ion batteries owing to its high specific capacity and cost‐effectiveness. However, LNO cathodes suffer from significant interfacial instability due to structural issues, cation mixing, and aggressive reactions with the electrolyte, which leads to rapid capacity loss. Herein, we report a surface‐stabilization strategy employing atomic layer deposition (ALD) to fabricate an ultrathin (ca. 4 nm), conformal dual‐metal oxide (Mg and Zn) Mg _x Zn _y O _z (MZO) protective layer on model LNO particles. Comprehensive characterization, including time‐of‐flight secondary‐ion mass spectrometry and scanning transmission electron microscopy–energy‐dispersive X‐ray spectroscopy, reveals a unique chemical distribution: the Zn species remain localized at the surface, whereas Mg partially diffuses into the superstructure. Electrochemical experiments demonstrate that the MZO‐coated LNO particles exhibit significantly enhanced stability, achieving a ca. 22% improvement in capacity retention after 100 cycles over the pristine LNO, alongside a reduction in voltage hysteresis and an increase in round‐trip efficiency. These findings indicate that ALD‐derived dual‐metal surface engineering can improve the early‐stage interfacial stability of cobalt‐free LNO cathodes.

The practical applicability of lithium‐metal batteries (LMBs) is severely hindered by uncontrollable lithium dendrite growth, interfacial instability, poor reversibility, and the formation of an unstable solid‐electrolyte interphase (SEI) on lithium‐metal anodes. Constructing a robust, uniform, and ionically conductive SEI is therefore critical to enable stable Li cycling. Herein, we report the in‐situ formation of LiBr‐rich SEI layer through modification of the separator surface, which effectively regulates Li deposition behavior. Owing to its low Li ⁺ diffusion barrier, high lithium adsorption capability, and ability to form a thin and compact interfacial layer, the LiBr‐derived SEI facilitates homogeneous ion flux, suppresses dendritic growth, and mitigates dead Li formation. Symmetric Li||Li cells demonstrate excellent rate performance even under high current densities. Post‐cycling and computational studies reveal formation of LiBr‐rich SEI layer with suppressed electrolyte decomposition, while the NMR data confirm suppressed HF evolution. Furthermore, GITT, Tafel slope, transference number, and activation‐energy analyses substantiate the accelerated Li ⁺ diffusion and improved charge‐transfer kinetics endowed by the LiBr‐rich SEI. Full‐cell configurations using LiMn ₀ . ₆ Fe ₀ . ₄ PO ₄ , Li||LMFP full‐cell and Li||Cu systems further demonstrate the substantial improvement in electrochemical performance, highlighting the potential of LiBr‐rich SEI layer as an effective interfacial engineering strategy for high‐energy, long‐life lithium metal batteries (LMBs).

The long‐term viability of sodium‐ion batteries (SIBs) hinges on improving cathode stability while maximizing energy density and efficiency. O3‐layered cathodes, with high sodium content, are ideal for achieving high capacity, but their long‐term structural stability is challenged by the electrochemical conditions in SIBs. Here, the impact of Mg doping on the transition metal site in O3‐type NaNi _0.2 Fe _0.4 Mn _0.4 O ₂ (NFM244) cathodes is investigated, revealing its influence on phase stability, anion redox ability, and Na‐ion diffusion kinetics. Experimental and theoretical studies confirmed that Mg ²⁺ preferentially substitutes the Fe ³⁺ sites, mitigating transition metal ions migration and lattice strain while suppressing irreversible oxygen release. Optimal 5% Mg doping maintains a stable O3‐layered structure, enhanced capacity, and Na‐ion kinetics, improving capacity retention during extended cycling over 200 cycles. In contrast, excessive Mg substitution causes structural distortion, impeding Na‐ion mobility, and results in severe capacity fading during prolonged cycling. In situ online electrochemical mass spectroscopy (OEMS) combined with X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that Mg doping also suppresses detrimental electrolyte decomposition. These findings provide a strategic pathway for tailoring next‐generation sodium‐ion cathodes for scalable high‐performance energy storage solutions, underscoring the potential of Mg doping in O3‐layered cathodes.