Water governs both reactivity and transport in aqueous batteries, yet the occurrence of distinct free, coordinated, and network-bound states complicates electrolyte design. Here, a quantitative water-speciation identification (QWSI) strategy is established to resolve and quantify water populations and to correlate composition with microstructure and function. Aqueous Zn-I2 batteries are employed as a model system owing to the high sensitivity of capacity to water-state distributions. Eliminating free water stabilizes electrophilic iodine species and activates the I2/2I+ couple to realize a four-electron conversion that doubles capacity, whereas driving water content too low depletes coordinated and network-bound water, slows ion transport, and ultimately compromises capacity. The QWSI strategy pinpoints a critical composition at which water resides within hydrogen-bond networks and cation solvation shells, with no detectable bulk-like free water. Electrolytes formulated at this composition sustain four-electron conversion while maintaining high ionic conductivity, reconciling activation of four-electron conversion with ion transport. Consequently, the Zn//I2 cells deliver distinct two-plateau profiles and high reversibility, enabling an average Coulombic efficiency of 99.8% and a specific capacity of 309.1 mAhg-1. These findings define molecular control of water-state distributions as a design principle, while the QWSI strategy provides quantitative descriptors for predictive control of solvation and reactivity across aqueous electrochemistry.

Exploring sodium-ion layered oxides with broad compositional diversity is an important approach for the development of high-performance positive electrodes. Structural chemistry determined by composition plays a decisive role in performance improvement, but the relationship between composition and structure becomes more elusive in complex multi-component systems. Here we propose an electronegativity entropy weight concept to understand entropy-dominated phases formation. Electronegativity and configurational entropy are used to quantify key interactions in layered materials. Guided by this understanding, we design a sodium-deficient layered oxide with an O3 stacking sequence. This material demonstrates good structural and thermal stability, along with air stability (negligible performance degradation after air exposure), cycling stability (93.02% capacity retention after 200 cycles), and rate capability (retaining 69.1% capacity retention from 86.5 mA g⁻¹ to 1.73 A g⁻¹). Even in potassium-ion batteries with larger inserted ions, the material still exhibits cycling stability. This strategy provides valuable compositional guidance for the rational design of high-performance layered oxide materials.

Understanding and suppressing gas evolution is critical to enabling high-energy-density lithium metal batteries (LMBs). Yet, comprehensive investigations in ether-based systems remain limited. Here we quantify gas generation in ether-based LMBs and elucidate the underlying mechanisms. We link CO and CO2 production to the cathode, and CH4 evolution to the anode. Notably, CO and CO2 are consumed at the Li anode to form Li-containing species such as Li2CO3. Although CH4 ultimately dominates the gaseous products, its evolution during cycling is delayed until a distinct onset point. We show that in a high-concentration ether electrolyte, anode activation improves Li deposition morphology and suppresses interfacial reactions, extending the number of cycles to gas onset and cell failure by an order of magnitude. Achieving these gains without altering the electrolyte enables the reconsideration of seemingly impractical electrolytes, highlighting a practical strategy to enhance the safety and performance of commercial LMBs.

Sodium-ion batteries (SIBs) present a compelling lithium-ion alternative, leveraging abundant sodium reserves and shared main-group chemistry for grid-scale storage and electric vehicles. Hard carbon (HC) is the prime sodium host among carbon-based materials, exhibiting superior thermodynamic stability during charge transfer over traditional graphite. However, complex organic precursors for HC anodes require precise control of structural evolution during carbonization to optimize ideal electrochemical performance. This work provides an independently developed Neural Network Potential (NNP) model for CHON-containing systems combined with experimental characterizations to reveal the pivotal role of oxygen contents in HC. Crucially, nitric acid preoxidation of pitch precursors elevates carbonized HC capacity from 300 to 350 mAh/g mainly in the plateau stage. Enhanced oxygen content increases carbonyl/carboxyl/ester group density, triggering intra-/inter-molecular crosslinking during carbonization. The results highlight that the resultant CO2/CO/H2 release generates radially propagating percolation pores within the carbon matrix, directly boosting sodium storage plateau capacity. Additionally, lateral and longitudinal dimensions of nanographitic crystallites modulate pore evolution during stacking as well. These atomistic insights into functional group transformations and nanographitic crystallites enable targeted HC structure optimization, advancing high-performance SIB electrode materials.

A physical phenomenon encompassing the transitions of open circuit voltage (OCV), internal resistance, temperature, pressure, and auto-ignition near crucial point is identified. This study has demonstrated the distinctive feature to be very similar among pouch NMC532, pouch LCO and cylindrical 21700 NCA batteries. The observed transient sequence less than 1.4s and in the temperature range of 1.3 ℃ is ranked as follow: pressure transition (TP3) → gas eruption associated with ejecta (Teruption) → resistance/OCV change (TR3/TV2) → auto-ignition (Tig) associated with a blue-purple flame. A unique Tcr has been captured earlier or later than pressure behaviors related to TP3, Teruption, and Pcr. These results provide a new perspective for the understanding of intrinsic safety design and the mechanism of TR.

Lithium-ion batteries lead in portable device and electric vehicle markets, yet scarcity of reserves drives the development of alternative battery technologies. Although graphene exhibits high conductivity and structural stability, its pure form as an anode suffers from low theoretical capacity, primarily due to weak interactions with alkali metal ions; therefore, heteroatom doping to enhance ion adsorption and storage capabilities has become a key modification strategy. Within the framework of density functional theory (DFT), this study systematically evaluated the potential of dual-phosphorus-doped graphene (D2-P2C12) functioning as an alkali-metal-ion battery anode. The computational results indicate that P-doping creates an asymmetric structure and increases the density of electrochemically active sites, thereby significantly enhancing the adsorption of alkali metal ions. Particularly for Na, the theoretical capacity reaches an ultrahigh value of 3,119.96 mAh/g, whereas the capacities for Li and K are both 779.99 mAh/g, demonstrating a stronger affinity for Na storage. After ion adsorption, the lattice parameters of D2-P2C12 vary by under 5%, demonstrating outstanding structural durability over repeated cycles. The material maintains good conductivity before and after adsorption, and the energy barriers of Li/Na/K diffusion on its surface are all below 0.4 eV, and its rate performance is excellent. In summary, D2-P2C12 provides strong theoretical support for developing efficient electrode materials for alkali metal ion batteries.

Abstract Mixed Sn–Pb halide perovskites exhibit excellent optoelectronic properties but suffer rapid degradation due to the facile oxidation of Sn2+ to Sn4+. Here, we establish a multiscale framework to uncover how cation ordering, surface defect chemistry, hole localization, and carrier dynamics collectively drive the initiation of Sn oxidation in FAPb0.5Sn0.5I3 (FA = formamidinium). Graph neural network screening identifies layered Sn/Pb enrichment as a recurring low-energy motif, which naturally yields an Sn-rich, Sn–I-terminated surface. Static calculations reveal contrasting effects of the two surface defects: the Sn vacancy (VSn) creates an oxidation-prone local environment that stabilizes Sn-centered hole localization and lattice distortion, whereas atop iodine (Iatop) promotes hole delocalization, reinforces the surface Sn–I framework, and suppresses the formation of Sn(IV)-like oxidation precursors. Nonadiabatic molecular dynamics further reveal a hundred-picosecond window, defined by ultrafast hole extraction toward the surface and much slower nonradiative recombination, in which accumulated photogenerated holes can drive oxidation-related lattice reorganization. Ab initio molecular dynamics simulations with two excess holes show that the pristine surface remains relatively robust, whereas VSn strongly stabilizes localized holes and triggers pronounced local distortion together with SnI4-like extrusion and defect growth. These findings reveal that Sn oxidation is governed by carrier–lattice coupling through its control over the kinetic accessibility of Sn-centered hole localization, and they identify the suppression of VSn defects and the stabilization of I-rich surface terminations as key design principles for stable Sn–Pb perovskites.

Introducing KH 2 PO 4 into the NiO x precursor effectively suppresses nanoparticle aggregation, enabling homogeneous coverage of the NiO x film. Based on a KH 2 PO 4 –NiO x film, the 1.77 eV PSC achieves a PCE of 21.17% with an impressive V OC of 1.363 V.

Sodium-ion batteries are promising candidates for large-scale energy storage applications. Nevertheless, conventional linear poly(1,3-dioxolane) (PDOL)-based electrolytes suffer from severe chain degradation, poor low-temperature ion conduction and unstable electrode interfacial properties, which severely limit their practical commercialization. Herein, ethylene sulfate and pentaerythritol bis(cyclic sulfate) are employed as functional modifiers to construct a three-dimensional cross-linked A2-DTD-TDT polymer electrolyte. The sulfonate ester groups work synergistically with Al³⁺ to regulate ring-opening polymerization, forming stable network architecture that effectively restrains structural deterioration and recrystallization at low temperature. The optimized electrolyte achieves a high ionic conductivity of 0.76 mS cm−1 and a high Na⁺ transference number of 0.89 at -20 °C, with an expanded electrochemical stability window up to 4.79 V, and enables stable Na⁺ transport and electrode-electrolyte interfaces across a wide temperature range of -40 to 55 °C. Benefiting from optimized solvation configuration and robust inorganic-rich SEI film, the assembled Na||Na symmetric cells achieve stable cycling for >6000 h at -40 °C. This work proposes a reliable modification strategy for developing wide-temperature and high-performance PDOL-based polymer electrolytes, and provides new insights into the structure-performance relationship of advanced sodium-ion battery electrolytes.

Electrolyte additives are essential for enhancing the interfacial stability of Na metal anodes by facilitating the construction of robust solid electrolyte interphases (SEI). However, competition for decomposition between additives and solvents hampers the preferential reduction of additives and diminishes their effectiveness. Herein, we propose an interfacial interaction-driven strategy to selectively regulate the decomposition behavior and maximize the utility of fluoroethylene carbonate (FEC) for constructing a robust NaF-rich SEI for stable sodium-metal batteries (SMBs). An in-situ formed Na3Bi alloy on the Na anode surface exhibits stronger adsorption affinity toward FEC compared to carbonate solvents, leading to FEC enrichment within the electric double layer at the anode surface. Benefiting from the enhanced interfacial interaction, the Na3Bi alloy facilitates preferential reductive decomposition of FEC and maximizes FEC utilization, resulting in a dense, gradient-structured NaF-rich SEI. Furthermore, the sodiophilic Na3Bi alloy effectively homogenizes Na nucleation and enables non-dendritic Na deposition. Importantly, the Na3Bi alloy maintains structural and chemical stability during prolonged cycling, ensuring sustained interfacial regulation. As a result, the modified Na anodes deliver excellent cycling stability in Na||Na symmetric cells. Moreover, the Na||Na3V2(PO4)3 (NVP) cells achieve an ultra-long lifespan exceeding 10,000 cycles at 5 C. The Na||NVP cells with high-loading NVP cathodes (10 mg cm-2) can still stably cycle for over 200 cycles at 1 C. This work reveals the critical role of interfacial engineering in modulating additive decomposition and offers a scalable pathway to enhance the stability of SMBs.

Lithium-sulfur (Li-S) batteries are considered promising candidates for next-generation energy storage due to their high energy density. However, the complex multi-electron redox mechanisms occurring in cathodes remain poorly understood, and clarifing the reaction mechanism of Li-S batteries is crucial for advancing their application. We select graphene as cathode material for Li-S batteries to investigate the discharge process by using first-principles calculations. Calculation results show that the radical polysulfide anions LiS5, LiS4, and LiS3 are the primary intermediate species, which is different from the Li2Sn (n = 1-8) intermediate commonly considered in early studies. Meanwhile, graphene can provide moderate adsorption strength for intermediate species and suppress the shuttle effect. Thermodynamic calculations combined with kinetic barrier analysis identified two feasible reaction pathways: S8-* LiS4-* LiS3-* LiS2 (Path A) and S8-* LiS5-* LiS4-* LiS3-* LiS2 (Path B). Path A was found to be the optimal pathway, and its rate-determining step barrier (0.67 eV) is significantly lower than the Path C/D involving the Li2Sn intermediates. This work reveals the catalytic reaction mechanism of graphene cathode during discharge process, which improves the understanding of Li-S battery systems and provides theoretical guidance for the design of cathode materials.

While pursuing high energy density in sodium-ion battery cathodes, ensuring intrinsic safety remains challenging. This study establishes a complete evidence chain linking "intrinsic chemical stability-metal dissolution-electrolyte catalytic decomposition-thermal safety" using NaNi1/3Fe1/3Mn1/3O2 (NFM), Na4Fe3(PO4)2(P2O7) (NFPP), and NaCrO2 (NCO) as models. We reveal that multivalent ions (Mn3+/Fe2+) in both NFM and NFPP trigger severe thermal runaway via a "dissolution-catalysis-runaway" cascade, despite their distinct structures. In contrast, NCO leverages the extreme chemical inertness of Cr3+ (unique d3 configuration and high Cr-O bond energy) to effectively sever this catalytic pathway, achieving counterintuitive high safety with minimal capacity sacrifice. This work elucidates that chemical inertness, rather than mere structural robustness, governs thermal safety, providing a new paradigm for designing intrinsically safe cathode materials.

Carbazole-based phosphonic acid self-assembled monolayers (SAMs) are essential for high-efficiency p-i-n perovskite solar cells. However, during processing, these SAMs inevitably contact perovskite inks, where their acidity triggers a dimethyl sulfoxide (DMSO)-mediated iodide redox reaction that imprints device performance, representing a universal bottleneck for inverted devices. We resolve this SAM-triggered redox mechanism and introduce chemistry-matched hydrazide additives to mitigate the degradation. These additives abrogate DMSO activation and redirect unwanted by-products toward benign hydrazide-formamidinium adducts. Consequently, we achieved power conversion efficiencies (PCEs) of 27.7% (certified 27.4%) in small-area (0.06 cm2) cells and 20.1% in 2.0 m2 modules, along with T95 lifetimes of ~2000 hours of maximum power point tracking (MPPT) at 85°C and ~1500 hours MPPT at 85°C and 85% relative humidity.

Abstract The search for stable, lead-free halide perovskites with tunable optoelectronic properties remains a critical challenge. Using first-principles calculations, we investigate the intrinsic defect properties and strain tunability of the metastable R3c phase NaGeI 3 . It is found that NaGeI 3 possesses a direct band gap of 2.69 eV at the Γ point, which can be effectively reduced to 1.92 eV under 3% strain induced by hydrostatic compression while retaining a direct gap, due to enhanced Ge-I orbital hopping and reduced octahedral distortion. Chemical potential analysis reveals that the compound is metastable with a small decomposition enthalpy of -24 meV/atom, presents a low intrinsic defect concentrations due to the dominant defects Nai, NaGe, and V Na with the defect formation energies above 1.2 eV, indicating high defect tolerance. Charge transition level calculations, after correcting for hole self-trapping relaxation, show that most defects introduce only shallow levels, while Nai and NaGe give rise to deep electron traps. However, optical transition analysis indicates that these defects can contribute to band-edge absorption enhancement at around 2.40 eV. Our results demonstrate that NaGeI 3 possesses high intrinsic defect tolerance and a strain-tunable band gap, positioning it as a strong candidate for low-cost, environmentally friendly perovskite photovoltaics.

Abstract Prussian blue analogues have emerged as a promising cathode material owing to their open‑framework structure and high theoretical capacities; however, the presence and dynamic evolution of crystalline water severely constrain their electrochemical performance. Despite extensive studies, a systematic understanding of dehydration-induced structural reconstruction and the role of water during electrochemical cycling remains elusive. Herein, we elucidate the structural evolution and water-regulated electrochemical behavior of Prussian blue (PB) through controlled dehydration-rehydration process. It is found that dehydration irreversibly triggers the fractures of the one-dimensional C ≡ N framework, forming novel crystal defects, that give rise to defect-associated water with lower binding energy. Density functional theory calculations corroborate the weakened water-framework interactions and reveal defect-mediated energetics. Upon rehydration, the optimized PB‑3 exhibits adaptive dehydration behavior during electrochemical cycling, in which defect-associated water is preferentially extracted upon charging, while coordinated and interstitial water persist as structural pillars, enabling high reversible capacity and long-term cycling stability. By precisely tuning the rehydration degree, PB‑3(H/L) achieves excellent long‑cycle life and rate performance. This work uncovers the mechanistic origin of dehydration-induced CN − defect formation and establishes adaptive water regulation as a governing principle for achieving high-capacity and high-stability Prussian blue cathodes.

Lithium doping can effectively mitigate the rapid capacity fade of layered oxide cathode materials for sodium-ion batteries, but the underlying mechanism remains unclear. In this study, by using first-principles calculations, we systematically investigate Li doping effects on the phase transition and surface properties of P2-NaxNi1/3Mn2/3O2 (0 < x < 1) during charge-discharge processes and reveal the following: (i) Li doping elevates the average operating voltage, enabling the material to maintain a higher sodium content at the practical upper-cutoff voltage. This higher sodium content thermodynamically stabilizes the layered structure, which is the fundamental reason for the redirected phase transition pathway from P2 → O2 to P2 → OP4. The associated activation of oxygen redox at a high SOC (state of charge) reduces the net charge on oxygen, thereby decreasing the electrostatic repulsion between the oxygen layers as a consequential effect. (ii) Li migration from the transition metal layer to the sodium layer can act as a structural pillar to prevent particle cracking, but this reversible migration between the two layers can only occur within a certain SOC range. (iii) The Na+/vacancy ordering is disrupted, leading to a solid-solution behavior during sodium insertion and extraction. These factors are likely the key reasons for the improved cycling stability, although surface oxygen exhibits stronger oxidizability at a high SOC, which may trigger severe interfacial side reactions. Therefore, it is necessary to strictly control the amount of sodium extraction to avoid over-oxidation.

All-solid-state batteries (ASSBs) employing Li-free anode materials (e.g., Si, Si-C) are promising for commercialization due to their compatibility with existing lithium-ion battery infrastructure and enhanced safety. However, their electrochemical performance is fundamentally limited because the initial lithium inventory resides entirely in the cathode, making them highly vulnerable to irreversible lithium loss during cycling. In this study, we introduce a novel cathode sacrificial agent (CSA), Li2S-LiI (6:1 mass ratio, denoted as LSI), which delivers a high capacity of 1020.5 mAh g-1, enabling effective compensation of lithium loss in ASSBs. Importantly, LSI maintains full compatibility with sulfide solid electrolytes and does not disrupt the lithium (de) intercalation behavior of the cathode active material. When implemented in Li-free anode ASSBs, LSI enables greater capacity utilization and markedly enhances cycling stability in both indium metal and silicon anode-based systems. This work provides a practical strategy to advance Li-free anode ASSBs toward high energy density and long-term durability.

This study comprehensively investigates the effects of lithium doping in suppressing the phase transitions during the charge–discharge process of the P2-phase sodium-layered oxide materials through DFT calculations, and identifies the root causes.

Halide solid electrolytes, exemplified by Li3YCl6 (LYC), offer moderate ionic conductivity (∼1 mS/cm), high oxidative stability (>4 V), and good mechanical deformability, making them promising candidates for solid-state lithium batteries. However, the room-temperature ionic conductivity of single-crystal LYC is nearly one order of magnitude higher than that of experimental polycrystalline samples. Grain boundaries (GBs) are considered the primary cause of this discrepancy. Although GBs critically influence Li-ion transport in most solid electrolytes, the impact in LYC remains poorly understood. Herein, we quantify the contribution of GBs to Li-ion transport in LYC utilizing machine learning driven deep potential molecular dynamics. For all GBs considered, the results reveal a strong inherent tendency toward polycrystallinity in LYC due to low GB formation energies. Although the ionic conductivity of all LYC GBs is lower than that of the bulk, among them, the highest activation energy and the lowest ionic conductivity are 0.246 eV and 8.6 mS/cm, respectively. Moreover, the {303¯2}⟨101¯3¯⟩ GB with the lowest GB energy (0.176 J/m2) exhibits the highest ionic conductivity of 13.9 mS/cm. The simulations demonstrate that GBs hinder overall Li-ion transport compared to the bulk, though GBs do not act as the dominant barrier to Li-ion transport in LYC. This work provides insights for the design of halide solid electrolytes.

Perovskite Li3xLa2/3-xTiO3 (LLTO) has been investigated as a Li-ion solid electrolyte material and has attracted significant attention due to its wide operating voltage range. Polycrystalline and grain boundaries (GBs) are a common structural motif found in ceramic oxides. So, GBs can have a significant influence on the material properties. Here, we conduct a molecular dynamics (MD) study that quantifies the effect of LLTO GBs on Li-ion transport. We examine six types of LLTO GBs, including P-Sigma 5(210), P-Sigma 5(310), P-Sigma 13(510) in the Li-poor phase and R-Sigma 5(210), R-Sigma 5(310), R-Sigma 13(510) in the Li-rich phase. We also consider the LLTO bulk for comparison. The results show that the grain boundary formation energies of the six GBs are all below 1.30 J/m(2), indicating the presence of a high concentration of GBs in polycrystalline LLTO. It is likely to find a highest concentration of Sigma 5(210) GB due to its lowest formation energy (1.00 J/m(2) for P-Sigma 5(210) and 0.89 J/m(2) for R-Sigma 5(210)). Compared with Li+ ions in the bulk LLTO, Li+ ions in the six GBs exhibit a lower mean squared displacement (MSD), a smaller migration energy barrier and a lower ionic conductivity. These results confirm that the LLTO GBs hinder Li+ transport. For bulk LLTO, the Li+ migration barrier is determined to be 0.30 eV (Li-poor phase) and 0.26 eV (Li-rich phase). In comparison, the migration barrier of LLTO GBs exhibits a slight decrease in Li-poor phase (0.32-0.37 eV) and Li-rich phase (0.27-0.31 eV). The computed Li-ion conductivities of the six GBs are 1 to 2 orders of magnitude lower than those of the corresponding bulk counterparts. Of the six GBs, P-Sigma 13(510) exhibits the highest Li+ conductivity of 4.76 & times;10(-5) S/cm in the Li-poor phase, whereas R-Sigma 5(310) shows the maximum Li+ conductivity of 1.31 & times;10(-3) S/cm in the Li-rich phase. Furthermore, the peak Li+ conductivity in the Li-rich phase is much higher than that in the Li-poor phase. In addition, Li+ transport perpendicular to the GB (i.e. from grain to grain) is more hindered than that along the GB. Nevertheless, the Li+ diffusion can be improved by increasing the Li content in the GB region. The Li+ diffusion maps can be visualized by analyzing the Li+ trajectories of the MD simulations. We find that Li+ transport is first restricted to the GB region, then gradually turns to the bulk region, and finally forms a two-dimensional diffusion path similar to that of the LLTO bulk. Furthermore, the Li+ diffusion strongly depends on the distribution of O ions in LLTO GBs. For example, in the Li-poor-phase P-Sigma 5(310) GB, the number of O ions in the GB region is greater than that in the bulk region, which indicates that a Li-O attractive interaction in the GB region is stronger, thereby hindering the formation and transport of Li+ to the bulk region. Overall, these atomic-scale insights deepen our understanding of LLTO GBs and their influence on Li+ transport.