We used two different techniques of atomic layer deposition (ALD) to prepare AlOx-coated LiNi0.8Co0.1Mn0.1O2 (NCM811) materials as cathodes for Li-ion batteries. The first approach was to use a fluidized bed reactor in order to coat the NMC811 powder before electrode film preparation and calendering with the goal of obtaining a dense coating on each particle of this powder. The second approach was to coat the electrode after film preparation and calendering by spatial ALD, with the possibility to prepare gradients of the coating material. We present an in-depth structural characterization of the prepared electrodes and their electrochemical performance, and we reveal the advantages and disadvantages of both approaches.

Sodium fluorophosphate Na2FePO4F holds great promise for sodium-ion batteries due to its high theoretical capacity, excellent structural stability, abundant resources, and affordability. However, its poor electronic and ionic conductivities limit its practical applications. Therefore, ion doping and carbon coating have been employed as synergistic strategies in this study to overcome these limitations. A one-step, energy-efficient solidstate method using sucrose as a carbon coating source was used to synthesize Na2FePO4F/C (NFPF/C) and its doped variant, Na2Fe0.85V0.1PO4F/C (NFVPF/C). 23Na-MAS-NMR spectra confirm the existence of two distinct sites for sodium (Na1/Na2). The ex-situ 23Na-MAS-NMR performed at different states-of-charge reveals the activity of only one sodium. The scanning electron microscopy findings reveal a reduction in the particle size with V-introduction, enhancing the energetic performances. NFVPF/C delivers higher specific capacity of 122 mAh g-1 compared to 116 mAh g-1 for NFPF/C at 0.1C. It also demonstrates improved cycling stability, retaining 81 % of its initial capacity after 120 cycles, in contrast to 46 % for the pristine material. The doped phase outperforms the pristine at higher current rates, delivering specific capacities of 81 and 55 mAh g-1 at 2C and 3C, respectively, compared to 35 and 17 mAh g-1 for NFPF/C.

Ion-exchange synthesis offers a powerful route to access Li-based fluorophosphates that are otherwise unattainable through direct methods. In this study, Na0.92Li1.05FePO4F/C (NLFPF/C) was successfully prepared via a chemical ion exchange reaction using Na2FePO4F/C (NFPF/C) as a precursor. XRD and Rietveld refinement confirmed that the orthorhombic Pbcn framework was preserved after exchange, while Raman and TGA demonstrated that the conductive carbon coating remained intact. ICP-OES and solid-state NMR showed a nearly one-to-one Na+/Li+ substitution, with Li+ occupying both Na sites in the Na2FePO4F framework. Variabletemperature XRD and TGA indicated structural decomposition above 350 degrees C, leading to the formation of NaFeP2O7. NFPF/C electrochemical profile exhibited two distinct voltage plateaus characteristic of biphasic Na+ migration, whereas NLFPF/C showed significantly different electrochemical behavior consisting of sloping profiles that indicate a solid-solution mechanism. NLFPF/C delivered a high discharge capacity of 139 mAh g- 1 at 0.1C with excellent capacity retention and improved coulombic efficiency over 100 cycles. Ex-situ XRD measurements confirmed reversible structural evolution without formation of secondary phases, suggesting a highly stable framework under cycling. These findings demonstrate the high stability and energy density of NLFPF/C and highlight ion exchange as an excellent strategy for designing advanced Li-based polyanionic cathodes.

The demand for high energy density in the field of Li-ion batteries has intensified interest in lithium-rich Mn-based layered oxide cathodes (LRLOs) owing to their high capacity and low cost. Nevertheless, the thermal runaway becomes an urgent concern because of the high-voltage operation (up to 4.8 V), and the structural evolution mechanism of delithiated LRLOs during heating remains unclear. Here, we combine in situ high-temperature X-ray diffraction and absorption spectroscopy to systematically investigate the structural and chemical evolution of Li1.2Ni0.2Mn0.6O2 (LLNMO) across distinct charge-discharge states. Interestingly, Ni is the first element to undergo thermally induced reduction in the charged state of LLNMO. With further increasing the temperature, Mn reduction sets in, coinciding with extensive lattice oxygen loss, and a phase transition from layered to disordered layered or Li-containing rock-salt-type phase occurs. More intriguingly, after the initial electrochemical cycle, LLNMO exhibits negative thermal expansion at low temperatures below 200 °C, which are attributed to the cycling-induced microstrain accumulation and long-range structural ordering. These findings provide a mechanistic insight into the state-of-charge-dependent thermal behavior of Li-rich layered materials and offer guidelines for designing safer, high-capacity battery materials.

Direct recycling is a promising approach for valorizing spent lithium-ion batteries, yet the effect of impurities on cathode regeneration has been insufficiently explored. Herein, an end-of-life LiNi0.6Co0.2Mn0.2O2 (NCM622) pouch cell is used as a model system to systematically investigate the behavior of impurities and the outcomes for regeneration, using XPS, SRD, and XAS techniques. The analysis identifies AlPO4, AlF3, Li3PO4, LiF, LixPFyO4, and Li2CO3 as the main impurities in the spent powder, along with Al-inclusion limited to a surface near region. Among these, Al-and F-containing species are found to significantly affect the regeneration process, inducing further Al-and F-inclusion in the regenerated material, while PO43- species exhibit a minimal structural impact. In-depth structural analysis reveals that F-inclusion proceeds via substitution of lattice oxygen, causing increased structural disorder. Al-inclusion most likely involves epitaxial crystal growth promoted by excess lithium salts, resulting in structural asymmetry at elevated inclusion levels. Electrochemical evaluation shows that low-level impurity inclusion has a negligible effect on initial capacity. Yet, impurity accumulation, potentially amplified over repeated recycling, markedly compromises capacity recovery and structural integrity. This work clarifies impurity-induced effects during regeneration and highlights the importance of impurity control for enabling sustainable and effective direct recycling.

Lithiumrich manganese spinels have attracted sustained interest because they promise high lithiumionsieve capacity. Although the material with nominal composition Li1.6Mn1.6O4 presents better performance than those belonging to the Li(1+d)Mn(2-d)O4 series, yet its exact crystal chemistry and structure remains controversial. In the present experimental and theoretical study, the material was synthesized by spraydrying followed by calcination, obtaining the target stoichiometry in which Mn is present with the 4+ oxidation state.,Rietveld refinements were performed to synchrotron X-Ray diffraction patterns using Full Prof and FAULTS programs to model stackingfaultinduced reflections broadening. The refinement revealed a twophase system, formed by ~80 wt.% of cubic spinel Li1.33Mn1.67O4 and ~20 wt. % of monoclinic-layered Li2MnO3, together reproducing the overall Li1.6Mn1.6O4 composition. ⁷Li solidstate NMR confirmed that lithium occupies 8a and 16d sites in the spinel and the presence of the Li2MnO3 phase. Furthermore, density functional theory calculations revealed that the formation of Li2MnO3 is probably inevitable in synthesis with Li/Mn ratios greater than 0.8 (d > 0.33), since a minimal stoichiometric imbalance could lead to metastable spinel phases.

Hard carbon (HC) has attracted considerable attention as an alternate anode material for lithium-ion batteries (LIBs) due to low cost, sustainability, and higher achievable capacity compared with graphite. Here, we report enhanced lithium storage capacity in HC derived from silica-depleted rice hull ash (SDRHA) apparently enabled by potassium-induced structural tuning. SDRHA is obtained through KOH-catalyzed distillative depolymerization of the SiO2 in RHA by reaction with hexylene glycol to produce a distillable spirosiloxane and coincidentally a high-surface-area (300-500 m2g-1) HC framework. On neutralizing the SDRHA to ≈ pH 9 ra-ther than 7, residual K+ is retained. Electrochemical testing of Li/SDRHAxx (xx = wt. % SiO2, 40-60) half-cells finds significantly improved capacities vs. fully neutralized samples. Capaci-ties increase from ≈ 740 mAhg-¹/500 cycles/0-2.5 V at pH 7 to ≈ 1250 mAhgcarbon-¹ at pH 9/60 cycles/0-3.0V with CEs of ~100% after initial formation (first-cycle efficiency, FCE = 40-45 %).Subsequent heating at 800 oC/N2/2 h with addition of KPF6 in the electrolyte further im-proves capacities to ~1400 ± 30 mAh gcarbon-1 and raises the FCE to ~50 %. TEM and EDS confirm the presence of residual potassium within the carbon framework and suggest potassi-um-associated structural evolution during cycling. 29Si and 13C Solid State NMR suggest elec-trochemical cycling induces structural divergence between the silica and carbon domains: the silica matrix becomes more disordered, the carbon domains undergo localized ordering per-haps associated with potassium rich regions. The results are consistent with a contribution from retained potassium, acting together with the porous SDRHA-derived HC structure and interfa-cial effects, to create additional lithium-storage-active environments. The achieved capacities significantly exceed those of commercial graphite (~370 mAh g-¹) under identical conditions, highlighting the potential of biomass-derived carbon as sustainable and high-performance anode materials for next-generation LIBs.

A series of LiV1-x Mn x PO4F/C (x = 0, 0.03, 0.09) materials were synthesized via a sol-gel method and thoroughly characterized to understand the structural, electronic, and electrochemical modifications induced by manganese incorporation. Structural analysis confirms that Mn doping preserves the triclinic lattice of LiVPO4F. The XAS measurements reveal partial oxidation of vanadium, forming a mixed V3+/V4+ state to compensate for aliovalent Mn2+ insertion. The impedance spectroscopy indicates improved lithium-ion mobility and reduced charge-transfer resistance in Mn-substituted samples. Among them, the V-Mn9 (x = 0.09) composition exhibits the best performance, delivering a high reversible capacity of 147 mAh g-1 with excellent cycling stability (99.3% capacity retention over 200 cycles at 1C). These results demonstrate that Mn2+ doping is an effective strategy to tune the redox environment and transport properties of LiVPO4F, thereby enhancing its viability for high-performance lithium-ion battery applications.

The electrochemical performance of layered transition-metal oxides is highly sensitive to lithium content, yet the underlying structural and redox mechanisms remain elusive. Here we systematically investigated this relationship using a series of Li1+x[Ni0.5Mn0.5]1- xO2 cathodes with tunable lithium content (x = 0, 0.05, 0.10, 0.15, 0.20). Increasing lithium content concertedly reduces lattice parameters, suppresses cation mixing, promotes the formation of honeycomb superstructure, and drives the evolution of superstructure units from LiMn6 to LiNiMn5. In parallel, the surface atomic structure evolves from fully disordered to partially disordered and ultimately to an ordered layered arrangement. Despite these structural improvements, higher lithium content is associated with a marked increase in irreversible oxygen redox activity, as revealed by combined spectroscopic and electrochemical analyses. Together, these findings establish lithium content as a key parameter governing the balance between structural order and redox reversibility. By optimizing this trade-off, we demonstrate a highperformance Li1.1Ni0.45Mn0.45O2 cathode that delivers a specific capacity of 228.0 mAh g- 1 with 90.4% capacity retention after 100 cycles. Our findings provide valuable insights into the chemical composition design of high-energy-density, layered cathodes.

Limited ion diffusion poses a major challenge for anode materials in lithium-ion batteries operating under extreme environments, where sluggish Li' transport and poor electronic conductivity severely deteriorate lithium-ion storage performance. Since ion diffusion pathways are intrinsically governed by the crystal structure, rational structural regulation is essential to enable low-energy diffusion pathways. Herein, vanadium-doped Nb2WO8 is designed to construct a dual-phase heterostructure composed of Nb2WO8 and Nb14W3O44, where vanadium incorporation introduces local lattice distortion and chargecompensation effects that destabilize the Nb2WO8 framework. The resulting dual-phase architecture introduces abundant heterointerfaces, which provide structurally disordered regions with reduced Li' diffusion energy barriers and facilitate ion transport. Meanwhile, vanadium doping effectively enhances the electronic conductivity of the composite, synergistically improving charge-transfer kinetics. The dualphase niobium-tungsten oxides exhibit high reversible capacities at -60 degrees C. A full cell assembled with LiCoO2 delivers a capacity retention of 80.05% after 100 cycles at 0.5 C and -40 degrees C. This work provides new insights into the structural design of high-performance anode materials for extreme-environment lithium-ion batteries. (c) 2026 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

All-solid-state lithium-sulfur batteries (ASSLSBs) hold great promise for next-generation electrochemical energy storage due to sulfur's high theoretical specific capacity and low cost. However, sluggish sulfur conversion kinetics and severe volume variations during cycling, as well as poor ionic percolation in composite cathodes, limit their practical viability. To overcome these challenges, we herein introduce solid electrolytes of nominal composition Li10.5- xSi1.5P1.5S12- xIx (with x = 0, 0.2, 0.4), possessing high ionic conductivities of ≥ 7 mS cm-1 at room temperature. We show that increasing iodine content alters the phase composition and triggers reversible redox activity in these materials. If implemented as catholytes, this enables very fast sulfur conversion kinetics, ultimately leading to ASSLSBs with exceptional performance. The cells achieve 86% sulfur utilization at a rate of C/2 and at 45°C and offer high-rate capability by delivering 1175 mAh gsulfur -1 at 5C and 590 mAh gsulfur -1 at 15C. Furthermore, the synergistic effects of ionic percolation and redox-activity enable record areal capacities up to 14 mAh cm-2 with a sulfur loading of 10 mg cm-2. Taken together, our findings provide new strategies for designing redox-active catholytes for application in advanced ASSLSBs and further strengthen the redox-mediating role of iodine therein.

Structural repair is a vital step in the direct recycling of spent LiNixCoyMnzO2 lithium-ion batteries, yet its underlying mechanisms remain insufficiently clear. Herein, the thermal solid-state structural repair of spent LiNi0.6Co0.2Mn0.2O2 (NCM622) layered cathode material is systematically investigated. Through multiscale techniques combining XRD, XAS, and 6Li solid-state NMR, we identify the structural degradation in spent NCM622 and monitor both long- and short-range structural evolution during repair. Our findings reveal that degradation predominantly occurs through Ni migration into Li octahedral sites, while Co and Mn demonstrate relatively lower occupancies in the Li layer. Such occupancies are primarily responsible for structural disorder and cubic-symmetry domain formation within the spent material. The repair process is demonstrated to involve re-lithiation, oxygen capture, increased transition metal (TM) oxidation states, and the migration of TM ions from the Li layer back to the TM layer, followed by cation diffusion. Both temperature and lithium compensation ratio are identified as critical factors promoting these processes. Capacity recovery studies show a strong correlation between reduced TM occupancy in the Li layer and improved electrochemical performances. These insights allow us to move beyond conventional phase-transition perspectives, offering an atomic-level understanding of structural degradation and repair mechanisms in spent layered cathode materials.

High-voltage, low-nickel, cobalt-free layered oxides are promising candidates for high-energy-density lithium-ion batteries. However, their practical application is hindered by intrinsic cation disorder and structural degradation at high voltages, leading to a poor electrochemical performance. Here, we report a slightly lithium-enriched, cobalt-free layered oxide, Li1.05Ni0.43Mn0.52O2, featuring lithium-rich disorder domains achieved through chemical composition optimization. Advanced structural characterization demonstrates that nickel ions not only reside within the TM layers but also occupy the Li layers, acting as pinned ions. Theoretical calculations indicate that this in-plane and out-of-plane disorder enables reversible oxygen redox activity without oxygen release at high voltages. Moreover, this local structural framework preserves integrity even after extended cycling, ensuring chemical and structural stability during battery operation. Consequently, the cathode delivers an impressive discharge capacity of 202.2 mAh g-1 at C/10 and exceptional cycling stability, retaining 96.3% of its capacity after 200 cycles at C/3 within a voltage range of 2.5-4.55 V. Our findings provide valuable insights into the design of high-energy-density, cobalt-free layered cathodes.

The formation process of NaFeF3 via ball milling of the binary fluorides, structural changes, and reaction kinetics has been investigated. The mixture of NaF and FeF2 educts was ball-milled for various durations, and the phase evolution was monitored by using a range of analytical techniques. X-ray diffractograms of the samples obtained after different milling times indicate the formation of NaFeF3 after just 30 min of milling, which is confirmed by 23Na NMR, 57Fe Mossbauer spectroscopy, and Fe K-edge XAS spectroscopy. Moreover, the magnetic properties of NaFeF3 and also its application as a cathode in a sodium-ion battery have been studied.

Lithium argyrodite superionic conductors with the general formula Li6PS5X (X = Cl, Br, I) have been intensively investigated in recent years and successfully adopted in the field of solid-state batteries (SSBs). The transport properties of argyrodite solid electrolytes (SEs) usually strongly depend on the degree of occupational disorder. Increasing disorder through complex doping or substitution has been shown to directly affect ionic conductivity. Herein, we explore a high-entropy lithium argyrodite of nominal composition Li6.6[P0.2Si0.2Sn0.2Ge0.2Sb0.2]S5I. This material can be readily prepared by mechanochemistry. Using complementary diffraction techniques, nuclear magnetic resonance spectroscopy, and charge-transport measurements, we show that upon tailoring crystallinity and defect concentration by post-annealing at temperatures up to 220 degrees C, a high room-temperature ionic conductivity of about 0.9 mS cm-1 (similar to 4.4 mS cm-1 bulk conductivity) can be achieved. Both the as-prepared and annealed (at 220 degrees C) samples were tested in pellet-stack SSB cells. The mechanochemically prepared glass-ceramic SE was found to exhibit superior performance, even outperforming commercially available Li6PS5Cl. Collectively, the results highlight the importance of considering structural aspects across different length scales when optimizing the properties of lithium argyrodites for SSB applications.

High-voltage fluorophosphate cathode materials have emerged as promising candidates for next-generation lithium-ion batteries, offering enhanced safety, energy density, and stability compared to conventional oxidebased materials. In this study we investigate the effects of manganese doping on the structural and electrochemical properties of LiVPO4F cathode material synthesized via an optimized and simple sol-gel method. A series of LiV1-2y/3MnyPO4F/C (y = 0, 0.03, 0.09, 0.15) compositions was successfully prepared and characterized to highlight the impact of Mn substitution on structural stability and electrochemical performance. X-ray diffraction analysis confirmed the preservation of the initial crystal structure of the undoped material for manganese content up to y = 0.09, while higher concentration (y = 0.15) leads to the appearance of secondary phases. The successful incorporation of Mn was confirmed by systematic shifts in diffraction peaks and changes in the unit cell parameters. Electrochemical characterization revealed that the optimized composition (y = 0.09) delivered a remarkable discharge capacity of 150 mAh/g at C/5, approaching the theoretical capacity of 153 mAh/g, with 98 % capacity retention after 100 cycles. Notably, all compositions demonstrated excellent thermal stability at 50 degrees C. Once again, the composition corresponding to y = 0.09 shows the best performance as it maintains a discharge capacity of 149 mAh/g with minimal capacity fade (approximate to 0.7 %) after 50 cycles. Rate capability tests showed enhanced performance for Mn-doped samples, particularly at higher C-rates, attributed to improved charge transfer kinetics and structural stability. The enhanced performance is attributed to the synergistic effects of successful Mn incorporation and the uniform carbon coating derived from the in-situ carbonization of citric acid. These results demonstrate the effectiveness of our synthetic approach in developing high-performance cathode materials for advanced lithium-ion batteries.

Solid-state batteries (SSBs) based on inorganic solid electrolytes (SEs) possibly offer enhanced energy and power densities, along with increased safety, compared to state-of-the-art rechargeable batteries using liquid organic electrolytes. However, the stiffness and brittle nature of inorganic SEs can complicate cell fabrication and lead to the (chemo)mechanical failure of SSBs during operation. In the past, the design of SEs has mainly focused on optimizing the ionic conductivity and (electro)chemical stability. However, to mitigate detrimental (chemo)mechanical degradation in SSBs, due to electrode volume and morphology changes upon charge and discharge, the mechanical properties of SEs also need to be considered in their development. In this regard, glass-ceramic SEs offer a reduced hardness but often suffer from rather low ionic conductivities. Herein we systematically investigate the effect of LiI additive and annealing temperature on phase composition and charge-transport properties of a series of SEs with the general composition of 4.25Li2S-0.75P2S5-1.5SiS2-xLiI (0 <= x <= 2). We demonstrate that the glass-ceramic material (LPSI-GC) with x(LiI) = 1.25 achieves a high room-temperature ionic conductivity of 4.38 mS cm-1 and further exhibits favorable mechanical properties owing to the combination of crystalline t-Li10.5P1.5Si1.5S12 and I-rich amorphous phases. When implemented in SSBs together with a layered Ni-rich oxide cathode material, the LPSI-GC SE enables stable cycling for over 100 cycles, although (electro)chemical decomposition, detected by X-ray photoelectron spectroscopy, is evident. Collectively, our results demonstrate that glass-ceramic SEs allow for simultaneous optimization of the ionic conductivity and mechanical properties, thus enabling long-term SSB operation.

Hard carbon (HC) anodes used in secondary batteries have attracted increasing recent attention in particular to transition to new energy storage formats. To date, HC is produced exclusively by charring organic precursors in inert atmospheres. One would not expect to find HC in rice hull ash (RHA), the byproduct of rice hull combustion processes. However, in developing approaches to depolymerize RHA SiO2 (90:10 wt% SiO2:C) to produce silica-depleted RHA or SDRHA(40-60) (40-60 wt% SiO2) to tailor C:SiO2 ratios for carbothermal reduction reactions, the SDRHA carbon component is recently revisited. In more detailed efforts to characterize the form of carbon present in SDRHA, a series of analyses reveal graphitized carbon domains in amorphous matrices, i.e., HC, despite RHA being produced via combustion in an oxidizing atmosphere. Comprehensive electrochemical analyses on SDRHA(40-60) find unexpected capacities far in excess (>700 mAh g(-1)) of reported values for HC and graphite. Electrochemical and STEM characterization suggest that the unexpected capacity may come from the nanoscale morphology of the amorphous carbon component. Given that RHA is a biowaste generated in kilotons/year worldwide, there seems to be an opportunity to develop sustainable high-capacity anode materials for alkali-ion storage systems.

Cathode materials Li1-xNi1-zCoz/2Mnz/2O2 with z = 1/5 (NCM811), z = 2/5 (NCM622), or z = 2/3 (NCM111) in (i) the pristine state, (ii) charged to x = 0.5 or x = 0.65, and (iii) discharged after having been charged previously were characterized by x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), direct current (DC) and alternating current (AC) magnetometry, heat capacity, and nuclear magnetic resonance (NMR) spectroscopy. The magnetic properties of these layered oxides are decisively determined by Ni2+ ions that have migrated from the transition metal (TM) layer to the Li layer and that are magnetically coupled to the Ni, Co, or Mn cations occupying neighboring sites within the adjacent TM layers. For the pristine and discharged states, this cluster formation causes a bifurcation between the zero-field-cooled (ZFC) and the field-cooled (FC) susceptibility vs temperature curve (which sets in continuously below about 100 K) and is responsible for the appearance of a broad maximum of the imaginary chi" susceptibility vs temperature curve that is centered around 14, 23, and 25 K for pristine NCM111, NCM622, and NCM811, respectively. The charged states with reduced Ni2+ amount do no longer show these features pointing to a strongly reduced cluster formation ability. Further, three-dimensional (frustrated) magnetic long-range ordering that leads to a broad local maximum in the heat capacity curve and to another abrupt bifurcation of the ZFC/FC susceptibility vs temperature curve (both observable slightly below 10 K) are additional features that all compositions (and states of charge) have in common. With increasing Ni to Co/Mn ratio, this low-temperature magnetic transition exhibits a more pronounced "partial" spin-glass-like characteristic as inferred from the frequency shift of the local AC susceptibility maximum. The results from AC/DC magnetometry and heat capacity measurements return complementary information to what can be inferred from XRD, XAS, and NMR investigations about the Ni to Co/Mn ratio, the Li/Ni disorder, and the TMs' oxidation states. The systematic investigation of samples with different Ni to Co/Mn ratios (going from NCM811 via NCM622 to NCM111) and with different oxidation states of the TMs (at different states of charge) allows for a better understanding of how the magnetic phenomena are correlated with the (real) structure and electronic properties in these layered oxide cathode materials.