A multimodal combined characterization platform is proposed to investigate the thermal stability of delithiated LLOs in the presence of an electrolyte for a low-gas-emission and high-safety battery system.

Deep eutectic solvents such as AlCl3/acetamide (AcA) have demonstrated great potential as room-temperature electrolytes for Al-S batteries, but their high viscosities and low ionic conductivities severely impede the electrochemical reaction kinetics. Herein, we report an effective strategy to optimize AlCl3/AcA by screening fluorobenzene co-solvents. The optimal 1,2,3-trifluorobenzene (tFBn) effectively dilutes AlCl3/AcA and has a crowding effect that creates a local high-concentration zone for efficient transport of electro-active ions. Rather than merely functioning as a diluent, tFBn induces the localized aggregation of neutral molecules and ion clusters, which reduces the bulk viscosity by 50% and doubles the ionic conductivity. This localized high concentration, coupled with the rapid migration of ion clusters, accelerates the reaction kinetics and improves the long-cycling stability of Al stripping/plating. tFBn also promotes the transportation of Al-Cl species onto Al to regulate the interphase structures and reduce the resistance. Due to the accelerated reaction kinetics, the tFBn-modified AlCl3/AcA further improves the S utilization, reduces the polarization, and enhances the capacity retention of Al-S batteries. This study provides important insights into the design of high-performance electrolytes toward practical Al-S batteries.

Ni-based layered oxides (NCMs) are one of the crucial candidates for high-energy Li-ion batteries, but suffer from severe structural degradation owing to diverse irreversible phase transitions, especially when Co is removed. Addressing such intrinsic instabilities calls for creative bulk design strategies, wherein crystal domain engineering emerges as a compelling approach. In this research, we developed a simple one-step strategy based on crystal domain engineering to controllably integrate locally ordered Li-rich Li2TMO3 crystal domain, which is composed of LiNi6- xMnx hexatomic-ring, into the NMs bulk lattice. By precisely controlling the lithium stoichiometry to obtain "twin domain" Ni-based cobalt-free lithium-rich layered oxides (Ni-LLOs) with a tunable lithium-rich functional unit. Benefiting from such crystal domain engineering, the optimal cathode material with competitive capacity (∼200 mAh g-1) can deliver an excellent capacity retention of 90.59% after 600 cycles in pouch-type cells at 1 C. Further mechanistic investigation reveals that the intergrown Li2TMO3 crystal domain suppress the formation of H3 phase and mitigate lattice contraction through a pinning effect, while simultaneously alleviating Li/Ni cation mixing, thereby reducing the necessity for cobalt incorporation. Collectively, this work establishes crystal domain engineering as a versatile and powerful strategy for developing high-energy, long-lifespan cathode materials for next-generation high-performance lithium-ion batteries.

Layered transition-metal oxide cathodes are pivotal for lithium-ion batteries (LIBs)-powered energy-storage systems. However, the relentless pursuit of high performance is severely bottlenecked by intrinsic thermal safety concerns, where structural degradation and interfacial instability can trigger catastrophic thermal runaway. Herein, a thermally triggered domino effect, manifesting as a destructive chain reaction that initiates with severe interfacial side reactions at the cathode surface and sequentially propagates toward profound bulk structural collapse, is identified as the headstream of thermal failure. To mitigate these vulnerabilities, a scalable crystalline-state composite strategy is proposed by integrating micrometer-scale layered oxides with nanosized olivine-structured oxides (LMFP). This rationally designed architecture also synergistically realizes volumetric compacted density up to 3.75 g cm-3 and 86% capacity retention over 1000 cycles. Specifically, LMFP affords a dual-spatial stabilization: it directs the formation of a robust inorganic-rich cathode-electrolyte interphase while simultaneously functioning as an internal thermal barrier to effectively interrupt this detrimental chain reaction, resulting in 61.3°C and 21.4°C thermal failure delay for both cathodes and ampere-hour-level cells, respectively, which creates more than 16 min for evacuation during thermal runaway. This work elucidates a previously overlooked surface-to-bulk failure mechanism and delineates a highly viable trajectory for designing intrinsically safe, highly stable cathode architectures.

Lithium-rich layered oxides (LLOs) deliver high energy density via coupled cationic/anionic redox, but high-voltage oxygen activation generates radical-rich interfaces that accelerate electrolyte decomposition, surface reconstruction, and mechanical failure. Although polyimide serves as an oxidation-resistant interphase on LLO cathodes, its durability is limited by labile termini vulnerable to reactive oxygen species, whereas backbone fluorination compromises ionic transport. In this study, a terminally fluorinated polyimide (FPI) interphase is constructed on LLOs (LLO-FPI) by introducing electron-withdrawing ─CF3 termini to elevate the interfacial electronic barrier, thereby mitigating oxidative attack and oxygen release while preserving backbone integrity. Terminal fluorination suppresses radical-mediated degradation and parasitic oxidation, while the high-modulus FPI interphase constrains stress-driven particle cracking without sacrificing Li+ kinetics. Consequently, LLO-FPI exhibits exceptional long-term cycling stability, retaining 80.8% capacity after 1000 cycles. A Si/C||LLO-FPI pouch cell delivers 409 Wh kg-1 with 90.1% capacity retention over 100 cycles. These findings identify terminal fluorination as a versatile strategy for durable high-energy-density batteries.

With the rapid development of electric transportation and energy storage fields, secondary battery devices with high-energy-density and long-term cycling life are urgently required to meet current market demands. Ni-based layered oxides (LiNixMyO2, x >= y, M = Co, Mn or Al) are considered as the dominant cathode materials for the next-generation batteries owing to their high-energy-density. However, with Ni content increasing, Ni-based cathode materials undergo rapid electrochemical degradation driven by bulk structural and cathode-electrolyte interface (CEI) instability and conventional element doping strategy struggles to balance high-capacity and long-term cycling life simultaneously. According to recent studies, implanting a "Li-rich functional unit" into Ni-based layered oxides holds the potential to address the above challenges. We systematically review the latest research progress, including implanting amount, existing form, functional mechanisms and inherent limitations of these different Li-rich functional units. Furthermore, we categorize the designed/synthesized materials into "Ni-based slightly Li-rich layered oxides (Ni-sLLOs)", "Ni-based Li-rich layered oxides (Ni-LLOs)", and "Ni-based surface Li-rich layered oxides (Ni-fLLOs)". Ultimately, we put forward a "dual Li-rich design" strategy for Ni-based layered oxides to solve the key issues of their application in next-generation high-energy-density and long-cycling Li-ion batteries.

Li-rich layered oxides (LLOs) show tremendous potential as cathode materials for next-generation Liion batteries (LIBs) due to their high energy density and cost-effectiveness. However, several challenges, including lattice oxygen release, interface side reactions, and structural transitions, lead to rapid performance degradation, which limits their widespread application. To address these issues, a phasecompatible spinel Li1.25 Cr0.25 Ti1.5 O4 (LCTO) coating layer on LLOs, as well as Cr3+ and Ti4+ surface codoping, is successfully constructed. Based on the synergetic effect of the coating and co-doping, we intend to effectively enhance the structure stability and electrochemical performance upon cycling. Consequently, the optimized LLOs-LCTO-1 exhibits a capacity retention of 85.6 % and a voltage decay of 0.309 mV cycle-1 after 500 cycles at 1 C. In addition, an excellent rate capacity of 163.5 mAh g-1 is delivered at 5 C. This study provides a promising solution for enhancing the performance and stability of LLOs, paving the way for their broader application in LIBs. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Mn-based Li-rich layered oxide (Mn-LLO) cathodes own promising potential for electrochemical energy-storage (EES) systems due to their cost-effectiveness, structural diversity, and high energy density. However, the longevity of these Mn-based materials remains a crucial challenge that hampers their adoption in grid-scale applications. To address this issue, the composite-structure outside of grain (CSOG) strategy integrated with layered/olivine structures is proposed for enhancing the stability of crystal structure, interfacial chemistry, and electrochemical cycling behaviors of Mn-LLOs. A series of cutting-edge microscopic and synchrotron techniques present the CSOG strategy that initiates the intensified particle surface, stable P-O bonding for layered structure, and robust electrode-electrolyte interphase. This multi-faceted reinforcement effectively bolsters interfacial stability for both pristine and electrochemical cycling. As a result, the Mn-based CSOG cathodes realize superior capacity retention over 1000 cycles with capacity decay of similar to 0.009 % per cycle in pouch cells. Crucially, enhanced interfacial behaviors in the CSOG cathodes inhibit elemental dissolution and deposition of Mn onto the anode and result in a similar to 39 % improvement in thermal stability compared to pristine Mn-LLOs. This innovative CSOG concept opens new avenues for designing highly stable Mn-based cathode materials, accentuating their potential for grid-scale EES applications.

The practical applications of high‐energy Li‐rich layered oxides (LLOs) have been hindered by the severe performance degradation including voltage decay and capacity fading. The gradient construction toward high‐activity interior and high‐stability exterior, typically realized by gradually changed transition metal (TM) gradient in LLOs, can alleviate the performance degradation to certain degrees. In this study, a gradient design of Al/Mg dopants is demonstrated for the TM‐gradient LLOs to further harmonize the high‐activity interior and high‐stability exterior, thereby forming the dual (TM and doping) gradient. As a result, superior capacity retention of 86% and a minor voltage decay of 0.54 mV cycle −1 are achieved at 1 C after 300 cycles. The improved electrochemical stability of the dual‐gradient LLO is attributed to the enhanced surface stability and suppressed bulk structure degeneration of LLOs upon electrochemical cycling. The dual‐gradient design serves as an important approach to fabricate high‐performance bulk LLOs toward applications.

A highly stable Mn-based composite-structure cathode material is constructed with the low crystallinity pre-introduced high-voltage spinel and Li 2 MnO 3 crystal domains, realizing excellent high-voltage stability and low-strain behaviours.

The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost, high energy density, and good performance at low temperatures, and is the promising choice for energy storage batteries. However, the long-cycling stability of batteries needs to be improved. Herein, the Mn-based Li-rich cathode materials with small amounts of Li2MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability. Then the batteries with a high energy density of 600 Wh kg−1, excellent capacity retention of 99.7% with low voltage decay of 0.03 mV cycle−1 after 800 cycles, and good rates performances can be achieved. Therefore, the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation, and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.

Accurate prediction of the remaining useful life (RUL) of lithium-ion batteries (LIBs) is crucial for enhancing the safety and efficiency of energy storage systems. This study proposes a genetic algorithm (GA)-optimized back-propagation (BP) neural network that eliminates the need for complex feature engineering and improves convergence robustness. By directly using raw cycle-capacity data and optimizing both weights and thresholds via GA, the model achieves high predictive accuracy across diverse battery chemistries and degradation behaviors. The model is validated using publicly available datasets for LiCoO2, LiFePO4, and NMC batteries, as well as lithium-rich layered oxide (LLOs) batteries from our laboratory. These datasets span a range of nonlinear and near-linear capacity fading profiles. Results demonstrate that the GA-BP model consistently outperforms conventional BP models, achieving R2 values exceeding 0.98 and effectively tracking both long-term degradation and short-term fluctuations. This approach provides a scalable and robust solution for battery health assessment and RUL forecasting across different battery chemistries and degradation scenarios.

High-capacity and reversible cathodes are important for sustainable energy development. Layered oxides present promising options, achieving a high capacity while maintaining manageable production costs. Despite the redox activity of transition metal primarily contributes to the capacity, anionic redox offers additional potential, as evidenced by the subtle voltage plateau at high voltage. However, challenges remain, particularly concerning the reversibility of anionic redox, resulting in voltage fade, hysteresis, and the formation of undesired oxygen species. Resonant inelastic X-ray scattering (RIXS) captures not only the charge transfer processes between oxygen ligands and transition metals but also the formation of molecular oxygen, elucidating the chemical transformations of oxygen during electrochemical cycles. Mapping capability allows for the generation of spectral patterns with quantitative measures that surpass those achievable by other characterization techniques. Though early reports on its advantages, a comprehensive discussion of RIXS and its perspectives on anionic redox processes in cathode materials remains absent but necessary. This perspective aims to provide a systematic overview of RIXS, emphasizing its unique contributions to cathode material research. It also serves as a valuable reference for energy researchers and RIXS practitioners, featuring the advancements and future possibilities of this powerful technique.

Manganese-based (Mn-based) layered oxides have emerged as competitive cathode materials for sodium-ion batteries (SIBs), primarily due to their high energy density, cost-effectiveness, and potential for mass production. However, these materials often suffer from irreversible oxygen redox reactions, significant phase transitions, and microcrack formation, which lead to considerable internal stress and degradation of electrochemical performance. This study introduces a high-entropy engineering strategy for P2-type Mn-based layered oxide cathodes (HE-NMCO), wherein a multi-ingredient cocktail effect strengthens the lattice framework by modulating the local environmental chemistry. This innovative approach fosters sustainable reversible oxygen activity, mitigates stress concentrations at grain boundaries, and accelerates Na + transport kinetics. The resulting robust lattice framework with optimized elemental interactions significantly improves structural integrity and reduces the formation of intragranular fractures. Consequently, HE-NMCO demonstrates remarkable cycling stability, retaining 93.5 % capacity after 100 deep (de)sodiation cycles, alongside an enhanced rate capability of 134.1 mAh g −1 at 5 C. Notably, comparative studies through multimodal characterization techniques highlight HE-NMCO′s superior reversibility in oxygen anion redox (OAR) reactions over extensive cycling, contrasting sharply with conventional NMCO cathode. This work elucidates the potential for advancing high energy and power density Mn-based cathodes for SIBs through local species diversity.

Fluorinated polymer matrix emerges as a promising candidate owing to their enhanced anti-oxidation ability, but their application is plagued by the relatively low ion conduction ability and the ambiguous ionic conduction mechanism in the fluorinated polymer electrolytes (PEs). Herein, a series of acrylate-based electrolytes with different fluorinated functional units (fluorinated-FUs) of poly(ethyl methacrylate) electrolyte (0F PE), poly (trifluoroethyl methacrylate) electrolyte (3F PE) and poly(hexafluorobutyl methacrylate) electrolyte (6F PE) were investigated. Beneficial from the long fluorinated-FUs in the side chain, the 6F PE exhibits improved both ionic conductivity of 4.0x10(-4) S cm(-1) and Li+ transference number of 0.65 at 25 degrees C, which are superior to those of the 0F PE and the 3F PE. The enhanced ion conduction mechanism was clarified via combining the theoretical calculations and experimental data, where the integration of local fluorinated-FUs provides additional coordinating sites for the continuous Li+ migration and regulates the ion transporting pathways. This work demonstrates that the regulation of local fluorinated-FUs can provide a promising strategy for achieving high performance PEs applied in solid-state batteries.

Poly(vinyl ethylene carbonate) (PVEC) electrolyte is a promising option for high-performance solid-state lithium metal batteries (SSLMBs). However, its anti-oxidation ability is still too low to match high-voltage cathode materials. Herein, a novel copolymer electrolyte, poly(vinyl ethylene carbonate-3-sulfolene) (P(VEC-SF)-PE) has been developed by copolymerizing 3-sulfolene (SF) and vinyl ethylene carbonate (VEC) monomer precursors. The P(VEC-SF)-PE possesses a wide electrochemical stability window of 5 V (vs. Li+/Li), high lithium ion transference number of 0.6 and ionic conductivity of 7.97 x 10-4 S cm-1 at 25 degrees C. The anti-oxidation ability is enhanced by the pre-degradation of sulfolene-based functional units and confirmed by multiple techniques. The P(VEC-SF)-PE based SSLMBs with the LiCoO2 cathode exhibit a high discharge capacity and good rate performances when charged to 4.5 V. This study presents an efficient strategy to improve the compatibility of the cathode/electrolyte interface and the electrochemical performances of high-energy SSLMBs. A novel poly(vinyl ethylene carbonate-3-sulfolene) electrolyte has been developed by copolymerizing monomer precursors, which has a wide electrochemical stability window of 5 V (vs. Li+/Li) attributed to the pre-degradation of sulfolene-based functional units.

Rechargeable batteries currently hold the largest share of the electrochemical energy storage market, and they play a major role in the sustainable energy transition and industrial decarbonization to respond to global climate change. Due to the increased popularity of consumer electronics and electric vehicles, lithium-ion batteries have quickly become the most successful rechargeable batteries in the past three decades, yet growing demands in diversified application scenarios call for new types of rechargeable batteries. Tremendous efforts are made to developing the next-generation post-Li-ion rechargeable batteries, which include, but are not limited to solid-state batteries, lithium-sulfur batteries, sodium-/potassium-ion batteries, organic batteries, magnesium-/zinc-ion batteries, aqueous batteries and flow batteries. Despite the great achievements, challenges persist in precise understandings about the electrochemical reaction and charge transfer process, and optimal design of key materials and interfaces in a battery. This roadmap tends to provide an overview about the current research progress, key challenges and future prospects of various types of rechargeable batteries. New computational methods for materials development, and characterization techniques will also be discussed as they play an important role in battery research.

Manganese-based lithium-rich layered oxides (Mn-LLOs) are promising candidate cathode materials for lithium-ion batteries, however, the severe voltage decay during cycling is the most concern for their practical applications. Herein, an Mn-based composite nanostructure constructed Li2MnO3 (LMO@Li2MnO3) is developed via an ultrathin amorphous functional oxide LixMnOy coating at the grain surface. Due to the thin and universal LMO amorphous surface layer etched from the lithiation process by the high-concentration alkaline solution, the structural and interfacial stability of Li2MnO3 are enhanced apparently, showing the significantly improved voltage maintenance, cycle stability, and energy density. In particular, the LMO@Li2MnO3 cathode exhibits zero voltage decay over 200 cycles. Combining with ex situ spectroscopic and microscopic techniques, the Mn2+/4+ coexisted behavior of the amorphous LMO is revealed, which enables the stable electrochemistry of Li2MnO3. This work provides new possible routes for suppressing the voltage decay of Mn-LLOs by modifying with the composite functional unit construction.

Stable electrolytes are urgently required for lithium-ion batteries based on lithium-rich layered oxides (LLOs), which generally suffer from fast capacity and voltage decay at high voltages up to 4.8 V. Herein, we report a salt-concentrated electrolyte consisting of 4 M lithium hexafluorophosphate (LiPF6) salt in ester solvents of fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC) to alleviate the above challenges. The solvent structure in the 4 M electrolyte shows more volatile DMC integrated with Li+ and more free antioxidative FEC compared with a 1 M electrolyte, broadening the operation voltage. Simultaneously, this electrolyte endows a thin yet high elasticity modulus LiF-rich interphase on the LLOs surface, which can effectively prevent diverse side reactions and transition metal migration, consequently improving the electrochemical performance with a voltage decay of only 0.46 mV/cycle and capacity retention of 80.3% after 500 cycles. This simple and effective approach boosts the development of high-energy-density batteries using LLOs.