Unfavorable Phase Research Articles

Phase Transition Driven Zn‐Ion Battery With Laser‐Processed V2C/V2O5 Electrodes for Wearable Temperature Monitoring

AbstractFlexible power supply devices present significant potential for wearable bioelectronics within the Internet of Things. Aqueous zinc‐ion batteries have emerged as a viable and safe alternative for power supply in flexible electronics. Nevertheless, typical battery behaviors are generally detrimental with unfavorable phase transition of electrodes, which invariably lead to rapid performance degradation. Here, extraordinary capacity enhancement of 150% is presented, sustained over 60 000 cycles, attained using vanadium carbide MXene (V2C)/vanadium pentoxide (V2O5) heterostructure as cathode. The unique cathode material is created through the rational engineering of MAX (V2AlC), employing a single‐step laser writing process. The ultrastable Zn ion battery stands in stark contrast to all previously reported counterparts, which typically exhibit capacity degradation within a few hundred/thousand cycles. The primary mechanisms driving this enhancement include the delamination of V2C MXene and an unexpected favorable phase transition during cycling. Additionally, a wearable power supply is constructed using a series configuration and is integrated with a commercial temperature sensor for wireless, real‐time body temperature monitoring. This study highlights the critical role of electrode design for advanced wearable bioelectronics.

Surface-Enhanced Ni-Rich Cathodes for Reversible Li Intercalation

Energy-dense nickel (Ni)-rich layered oxide cathodes can enable lithium (Li)-ion batteries to power electric vehicles (EVs) for long distance. Employing Ni-rich cathodes, however, faces challenges in stabilizing cathode-electrolyte interfaces, leading to substantial degradation of the layered structure at the cathode surface during cycling process. In particular, high-voltage operation for the layered oxide cathodes leads to substantial volume change and structure collapsing, and thereby chemo-mechanical degradation. Cation doping, surface engineering, and/or composition gradient designs are common approaches to stabilizing charged structures at high voltage. They have proven effective in suppressing surface degradation of the layered oxide particles by promoting phase stability or providing extrinsic protection.In this presentation, we propose a reactive coating method to obtain active cathode particles with protective passivation via transition metal doping, which could primarily address parasitic side reactions occurring at the cathode-electrolyte interface. Our designed Mo (or Ti)-doped layered oxide cathodes contain more than 90% Ni and demonstrate high-voltage stability and good capacity retention under high temperature cycling environment. This results from an electrochemically stable, 10 nm-thick surface phase that was formed in situ during one step calcination process. Electron microscopy combined with elemental analysis indicates that the surface is Mo (or Ti)-rich phase. An electron diffraction pattern from the high-resolution transmission electron microscopy (TEM) reveals that the surface has rocksalt-like structure, while the bulk maintains the layered structure.This surface-enhanced cathode delivers 216 mAh/g at the second discharge (0.2C, room temperature) with excellent capacity retention of 89% over 50 cycles (1C, 45oC). This outperforms the pristine Ni-rich cathode without doping, in which the retention rate is 78%. Since the capacity fading of these Ni-rich layered cathodes largely originates from the cyclic internal stress caused by the repetitive H2-H3 phase transitions. Here, the differential capacity-voltage analysis and ex situ X-ray diffraction suggest that the surface coating can delay and suppress the unfavorable H2-H3 phase transition at high state of charge for the Ni-rich cathode, extending cycle life. Consequently, the Mo (or Ti) surface disordered rocksalt phase alleviated the structural stress associated with the repetitive phase transition by reducing the abrupt lattice collapse/expansion. The effects of the reduced lattice distortion, Ti/Mo-rich surface phase were reflected by the enhanced cycling stability of the coated cathodes in rate capability analysis. We consider that our work demonstrates how doping can stabilize the particle surface of Ni-rich cathodes to promote Li intercalation reversibility and energy density. And we expect that this dual modification design represents future research direction towards high-performance cathodes and will inspire waves of efforts to develop multifunctional materials for next-generation batteries.

Stabilizing 4.6 V LiCoO2 via Surface‐to‐Bulk Titanium Modification

AbstractElevating the charging cut‐off voltage is an effective strategy to increase the energy density of LiCoO2. However, unstable interfacial structures and unfavorable phase transitions in bulk are inevitably triggered during deep de‐lithiation at high voltage. Herein, an integrated surface‐to‐bulk Ti‐modification strategy is applied to LiCoO2, enabling uniform Li2TiO3 coating on the surface and gradient Ti‐doping toward the structural bulk. The resultant Ti‐modified LiCoO2 (T‐LCO) electrode can be stably cycled up to 4.6 V, providing a high‐rate capability of 137 mAh g−1 at 5C and a long‐life stability with 80.5% capacity retention after 400 cycles at 1C, far outperforming the unmodified LiCoO2 electrode with only 50.7% capacity retention. In situ X‐ray diffraction characterization and density functional theory calculation reveal that the synergistic modification of T‐LCO enhances Li+ diffusion, facilitates the construction of high‐quality cathode/electrolyte interphase, reduces the phase transition from O3 to H1‐3 and Co3d/O2p band overlap, and restrains layer‐to‐spinel phase distortion, thus improving structural stability at 4.6 V. This work presents a “two birds one step” strategy to enhance the cycling stability and achievable capacity of high‐voltage LiCoO2 for developing high energy density lithium‐ion batteries.

Laves phase control and tensile properties optimization of DED-arc repaired 718Plus components through the addition of TiC and Cr2C3

Directed energy deposition-arc (DED-arc) additive manufacturing technology was used to repair the damaged 718Plus components. This work shows that TiC/Cr2C3 addition to 718Plus alloy is an effective way to suppress the formation of the unfavorable Laves phase. TiC additions to 718Plus alloy can alleviate the elemental segregation, refine the dendritic structure and promote the formation of blocky TiC-NbC core-shell carbides and NbC carbides, while Cr2C3 additions enable the precipitation of rod-like NbC carbides. During the deposition process, the TiC/Cr2C3 additions were dissolved into the molten pool and decomposed into Ti, Cr, and C. The introduction of additional carbon in the melt drastically consumed the Nb available for Laves phase. The tensile tests show that TiC addition to 718Plus alloy contributed to an increased tensile strength of about 120 MPa due to the reduced amount of Laves phase and the reinforced effect of carbides. The fracture behaviour of carbides was explained in detail. The critical shear stress for blocky carbides to crack is higher than that required for rod-like ones, suggesting that TiC additions were desirable for better ductility compared with Cr2C3 additions.

Homogenizing Energy Landscape for Efficient and Spectrally Stable Blue Perovskite Light-Emitting Diodes.

Blue perovskite light-emitting diodes (PeLEDs) have attracted enormous attention; however, their unsatisfactory device efficiency and spectral stability still remain great challenges. Unfavorable low-dimensional phase distribution and defects with deeper energy levels usually cause energy disorder, substantially limiting the device's performance. Here, an additive-interface optimization strategy is reported to tackle these issues, thus realizing efficient and spectrally stable blue PeLEDs. A new type of additive-formamidinium tetrafluorosuccinate (FATFSA) is introduced into the quasi-2D mixed halide perovskite accompanied by interface engineering, which effectively impedes the formation of undesired low-dimensional phases with various bandgaps throughout the entire film, thereby boosting energy transfer process for accelerating radiative recombination; this strategy also diminishes the halide vacancies especially chloride-related defects with deep energy level, thus reducing nonradiative energy loss for efficient radiative recombination. Benefitting from homogenized energy landscape throughout the entire perovskite emitting layer, PeLEDs with spectrally-stable blue emission (478nm) and champion external quantum efficiency (EQE) of 21.9% are realized, which represents a record value among this type of PeLEDs in the pure blue region.

First-Principle Insight of Synergistic Modification Mechanism in P2-Type Layered Oxide Cathode Material with Anionic Redox Activity for Sodium-Ion Batteries

Layered oxides exhibiting anionic redox activity have gained attention as a promising material in both Na-ion batteries owing to their additional capacity provided through oxygen redox chemistry. However, unfavorable side effects such as irreversible phase transformation, hysteresis, and gas evolution, usually arise during the stabilization process of the unstable electron holes generated by the redox reaction of oxygen. To address these challenges, we co-dope Cu and Ca in the pristine Nax[Mg0.28Mn0.72]O2 (NMMO) and propose the P2-type NaxCa0.03Mg0.22Cu0.11Mn0.67O2 (NCaMCMO) Na-deficient cathode material which demonstrates high specific capacity with minimal phase change. In this work, we employed the density functional theory (DFT) calculations to investigate the underlying mechanisms of the synergistic modification strategy in both transition metal and alkali metal layers. The substitution of electrochemically active Cu induced variations in the electronic structure near the Fermi level, indicating an inherent change in redox chemistry. The computational results of the local structure provide a deeper understanding of the oxygen-stabilizing effect of Cu. Furthermore, we analyze the nature of the Ca insertion as a pillar in an alkali-metal layer, which mitigates phase transformation to the kinetically unfavorable O2 phase through phase energy comparison. The calculations manifest that Ca doping effectively extends the P2 phase into a deeper charging state. This work elucidates fundamental mechanisms for enhancing cathode materials in future battery design.

Corrosion properties of submerged friction stir modified as-cast nickel-aluminum bronze (NAB) compositions

This study aimed to analyze the effects of adding alloying elements and cooling medium during friction stirring on the electrochemical and immersion corrosion properties. The results showed that the addition of nickel and iron prevented the formation of an unfavorable phase γ2 and instead produced intermetallic compounds κ in the microstructure. Friction stir processing (FSP) helped refine and homogenize the coarse and inhomogeneous structure of the casting, and also eliminated casting defects, whether performed in air or underwater conditions. The polarization and electrochemical impedance tests revealed that, in most cases, FSP led to a decrease in electrochemical and short-term corrosion behaviors as compared to the as-cast specimens, under the impact of alloy composition and active cooling. However, the weight loss immersion tests indicated that the friction stir processed alloys, particularly those processed underwater, demonstrated the best long-term corrosion properties. It was observed that the corrosion product film created on all models after immersion had a similar composition.

Cu-substituted Na0.75Ni0.17Cu0.08Mn0.75O2 cathode with suppressing P2-O2 phase transition and air-stable for high-performance sodium-ion batteries

P2-Na0.75Ni0.25Mn0.75O2 cathode material with high specific capacity and high operating voltage is favored by researchers. However, the complex phase transition (P2-O2) at high voltage and the rapid capacity decay caused by Na+/vacancy ordering seriously restrict its application. In this study, a series of Cu-substituted P2-type Na0.75Ni0.25-xCuxMn0.75O2 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.1) cathodes are synthesized. The Na0.75Ni0.17Cu0.08Mn0.75O2 cathode achieves a high initial discharge capacity of 133.6 mAh g−1 and remains 80.5 % of this capacity after 150 cycles at 0.1C, outperforming the performance of other compositions. Investigations into the superior electrochemical performance of Na0.75Ni0.17Cu0.08Mn0.75O2 through a multi-technique approach, including in-situ X-ray diffraction (XRD), ex-situ X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT), elucidate the underlying mechanisms. The results show that the introduction of Cu2+ in Na0.75Ni0.25Mn0.75O2 can successfully regulate the ratio of Naf/Nae, with enhanced cell performance when Na+ occupies more Nae sites compared to Naf sites. In-situ XRD confirms that the Cu substitution for Ni stabilizes the P2 structure during the charge–discharge process and inhibits the unfavorable P2-O2 phase transition at high voltage. In addition, Cu-substituted cathode materials exhibit a good effect on improving air stability, attributed to the higher Cu2+/Cu3+ redox potential. This unique substitution mechanism offers a novel perspective for understanding the structure-performance relationship of P2-type cathode materials and provides important support for the design of air-stable, high-performance cathode materials.

Prevalence and Impact of Bypassing or Overriding Phase 2 Trials in Neurologic Drug Development.

Pivotal trials for neurologic drugs in clinical development are often initiated without a phase 2 trial ("bypass") or despite a negative phase 2 efficacy result ("override"). Such practices may degrade the risk/benefit ratio of phase 3 trials. The aim of this study is to estimate the proportion of phase 3 trials for 10 neurologic diseases started without a positive phase 2 trial, to identify factors associated with this practice, and to investigate any association with unfavorable phase 3 trial outcomes. We searched ClinicalTrials.gov for phase 3 trials completed during 2011-2021, with at least 1 research site in the United States, Canada, the European Union, the United Kingdom, or Australia, and investigating drugs or biologics for treatment of 10 neurologic conditions. Our primary objective was to assess the prevalence of phase 2 bypass/override by searching for preceding phase 2 trials. We used Fisher exact tests to determine whether phase 3 trial characteristics and trial results were associated with phase 2 bypass/override. Of the 1,188 phase 3 trials captured in our search, 113 met eligibility for inclusion. Of these, 46% were not preceded by a phase 2 trial that was positive on an efficacy endpoint (31% bypassed and 15% overrode phase 2 trial). Phase 2 bypass/override was not associated with industry funding (77% vs 89%, 95% CI 0.75-7.55, p = 0.13) or testing already approved interventions (23% vs 15%, 95% CI 0.60-5.14, p = 0.33). Overall, phase 3 trials based on phase 2 bypassed/override were statistically significantly less likely to be positive on their primary outcome (31% vs 57%, respectively, 95% CI 1.21-6.92, p = 0.01). This effect disappeared when indications characterized by nearly universal positive or negative results were excluded. Trials that bypassed/overrode phase 2 trials were not statistically significantly more likely to be terminated early because of safety or futility (29% vs 15%, respectively, 95% CI 0.15-1.18, p = 0.11) and did not show increased risk of adverse events in experimental arms (RR = 1.46, 95% CI 1.19-1.79, vs RR = 1.36, 95% CI 1.10-1.69, respectively, p = 0.65). Almost half of the neurologic disease phase 3 trials were initiated without the support of a positive phase 2 trial. Although our analysis does not establish harm with bypass/override, its prevalence and the scientific rationale for phase 2 trial testing favor development of criteria defining when phase 2 bypass/override is justified.

Nitrogen-Blowing Assisted Strategy for Fabricating Large-Area Organic Solar Modules with an Efficiency of 15.6.

Organic solar cells (OSCs) are one of the most promising photovoltaic technologies due to their affordability and adaptability. However, upscaling is a critical issue that hinders the commercialization of OSCs. A significant challenge is the lack of cost-effective and facile techniques to modulate the morphology of the active layers. The slow solvent evaporation leads to an unfavorable phase separation, thus resulting in a low power conversion efficiency (PCE) of organic solar modules. Here, a nitrogen-blowing assisted method is developed to fabricate a large-area organic solar module (active area = 12 cm2) utilizing high-boiling-point solvents, achieving a PCE of 15.6%. The device fabricated with a high-boiling-point solvent produces a more uniform and smoother large-area film, and the assistance of nitrogen-blowing accelerates solvent evaporation, resulting in an optimized morphology with proper phase separation and finer aggregates. Moreover, the device fabricated by the nitrogen-blowing assisted method exhibits improved exciton dissociation, balanced carrier mobility, and reduced charge recombination. This work proposes a universal and cost-effective technique for the fabrication of high-efficiency organic solar modules.

Gradient fluorination engineering through interdiffusion reaction for high-voltage LiCoO2

The advancement of high charging cut-off voltage stands as a crucial avenue to enhance the energy density of LiCoO2 (LCO). However, LCO faces severe interface and bulk phase issues at high voltage (≥ 4.6 V), resulting in poor cycling stability. In this study, we reconstruct the surface structure of LCO based on the interdiffusion reaction between LCO and MgF2 in a high-temperature sintering process. Specifically, this interdiffusion reaction yields an ultra-thin LiF coating layer, artificially reinforcing the chemical structure of the cathode-electrolyte interphase (CEI) during cycling. This LiF-rich CEI not only effectively protects the surface structure of LCO, but also facilitates the lithium-ion diffusion. Furthermore, the diffusion of F and Mg into the LCO lattice significantly strengthens the structure, which inhibits unfavorable phase transitions from the O3 phase to the H1–3 phase at high voltage. Consequently, such modified LCO with concurrently enhanced interface and bulk structure exhibits outstanding long-term cycling performance within 3.0–4.6 V at 1 C, achieving a capacity retention of 84.9 % after 1000 cycles. Meanwhile, it also demonstrates excellent high-temperature performance, with a capacity retention of 85.0 % after 200 cycles under 45 °C.

Entropy Engineering Constrain Phase Transitions Enable Ultralong-life Prussian Blue Analogs Cathodes.

Prussian blue analogs (PBAs) are considered as one of the most potential electrode materials in capacitive deionization (CDI) due to their unique 3D framework structure. However, their practical applications suffer from low desalination capacity and poor cyclic stability. Here, an entropy engineering strategy is proposed that incorporates high-entropy (HE) concept into PBAs to address the unfavorable multistage phase transitions during CDI desalination. By introducing five or more metals, which share N coordination site, high-entropy hexacyanoferrate (HE-HCF) is constructed, thereby increasing the configurational entropy of the system to above 1.5R and placing it into the high-entropy category. As a result, the developed HE-HCF demonstrates remarkable cycling performance, with a capacity retention rate of over 97% after undergoing 350 ultralong-life cycles of adsorption/desorption. Additionally, it exhibits a high desalination capacity of 77.24mg g-1 at 1.2V. Structural characterization and theoretical calculation reveal that high configurational entropy not only helps to restrain phase transition and strengthen structural stability, but also optimizes Na+ ions diffusion path and energy barrier, accelerates reaction kinetics and thus improves performance. This research introduces a new approach for designing electrodes with high performance, low cost, and long-lasting durability for capacitive deionization applications.

Wear-resistant ZrN/Ti functionally graded coating prepared on TA18 alloy by double glow plasma alloying

Despite being an excellent structural material, α-Ti alloy is with low shear deformation resistance, resulting in susceptibility to friction damage during service, and limits its further application. A wear-resistant ZrN/Ti functionally graded coating (FGC) was prepared on TA18 alloy by double glow plasma alloying technique in this paper. The morphology, phase structure, mechanical properties and wear behavior of ZrN/Ti FGCs were studied and analyzed. The results proved that a gradient structure formed in the coating: the topmost layer was ZrN ceramic phase, in the transition layer were ZrN, TiN, and Ti2N phases, and in the inner layer was α-Ti phase. The coating was dense and metallurgically bonded with the substrate. It exhibited better load bearing capacity and fracture toughness. Upon conclusion of wear tests under different loads, only slight damage was observed on the coating. The main wear form of the coating was delamination wear, and the ZrN layer on the topmost surface was not worn through. More specifically, the Zr pre-diffusion treatment was used to increase the content of ZrN in the transition layer, reducing the unfavorable Ti nitride phase formed. Therefore, the stress concentration caused by the difference in elastic modulus between the different phases was relieved. Thus, ZrN/Ti FGC with continuous properties and good wear resistance was successfully synthesized.

High-speed and high-precision measurement of biaxial in-plane displacements: tens of nanometers principle error suppression in microprobe sensors

When the microprobe sensor is faced with the demand of high-speed biaxial displacement measurement, due to the characteristics of phase generated carrier (PGC) technology, accompanying optical intensity modulation (AOIM) and unfavorable phase modulation depth (PMD) will bring about the tens of nanometer cyclic nonlinear errors, further hindering high-speed and high-precision measurement. Herein, a light source intensity stabilization system based on semiconductor optical amplifier (SOA) feedback control is achieved to eliminate the error caused by AOIM in the presence of high-frequency and large-amplitude laser modulation. Based on this, the reasons for large nonlinear errors in biaxial measurements and the inability to ensure the stability of the accuracy of multiple measurement axes are methodically examined, and an effective nonlinear error elimination methodology based on the normalized amplitude correction of active temperature scanning is proposed. The continuity and linearity of the temperature scanning are also discussed. The performed experiments show that the above approach is capable of reducing the displacement demodulation error from the nanometer scale to the sub-nanometer scale. Further, the nonlinear error is reduced to within 0.1 nm for both measurement axes and the performance becomes consistent. The dual-axis measurement resolution of the microprobe sensor reaches 0.4 nm and the measurement speed is better than 1.2 m/s with the standard deviation of lower than 0.5 nm.

Impact of synergistic interfacial modification on the electrochemical performance of LiNi0.5Mn1.5O4 cathode materials

Developing sophisticated lithium-ion batteries with high energy and power density requires using high-voltage positive electrodes. Due to its three-dimensional lithium-ion diffusion and greater nominal operating voltage, spinel LiNi0.5Mn1.5O4 has emerged as one of lithium-ion batteries' most viable cathode materials. Electrolyte breakdown, Mn dissolution, and rapid cathode-electrolyte interface (CEI) degradation in lithium-ion cells are exacerbated by the high operating voltage of LNMO. Consequently, the long-term cycling of LNMO is hampered by such adverse side effects, making the commercialization of such a battery impractical. Here, we document the enhancement in the electrochemical performance of LNMO by surface modification utilizing a combination of Al2O3 coating and Graphene enveloping employing a facile wet synthesis technique. The presence of highly crystalline spherical secondary microspheres consisting of primary nanoparticles of disordered LiNi0.5Mn1.5O4, the surface modification with Al2O3, and the subsequent graphene wrapping were all confirmed by structural and surface analysis techniques. The fabricated cells containing the enhanced cathode material (LNMO-Al-GO) were cycled at a C/10 rate for 100 cycles in a voltage window of 3.5–4.9 V, providing a specific discharge capacity of 134.7 ± 3.8 mAhg−1. Delivering a capacity retention of 97.7 ± 3.9% compared to the unmodified LNMO sample (84.7 ± 5.3%). Ex-situ XRD, Electrochemical Impedance Spectroscopy (EIS), and Differential Scanning Calorimetry (DSC) investigations reveal that the alumina coating protects the cathode by acting as a hydrogen fluoride (H.F.) scavenger and minimizes unfavorable phase formations at the CEI, inhibiting Mn3+ dissolution and enhancing cyclability.

Promoting Na-ion storage in P2-Na0.67Ni0.33Mn0.67O2 cathode via synergetic Ti and Zn Co-incorporation

P2-Na0.67Ni0.33Mn0.67O2 (NNMO) is regarded as a promising cathode candidate for sodium-ion batteries due to its high energy density. However, the electrochemical performance is hindered by Na+/vacancy order, irreversible P2–O2 phase transition at high voltage (>4.2 V), and harmful oxygen evolution. Herein, a synergetic Zn and Ti co-incorporation tactic is proposed for designing a Na0.67Ni0.29Zn0.04Mn0.63Ti0.04O2 (NNZMTO) cathode to overcome the above-mentioned challenges. First, the incorporated Ti heteroatom could break down Na+/vacancy order of NNMO by taking advantage of a similar ionic radius and substantially different Fermi levels with host Mn atom. Subsequently, the introduced Zn heteroatom could induce local Na–O–Zn configurations, buffer interlayer O2−–O2− electrostatic repulsion, as well as inhibit unfavorable phase transition. Moreover, the d10 band of Zn is lower than the oxygen states, and the Zn behaves like an s/p metal with oxygen, thus avoiding O2 release. Notably, in comparison with highly oxidized (Ni4+/Mn4+O6)δ− octahedron, the partial Na+ for charge neutrality in alkali metal layers could be well maintained in the as-designed (Zn2+/Ti4+O6)δ′−, which could be served as “pillars” to avoid layer gliding and structural collapse in the c-direction. As a result, an excellent electrochemical performance with high specific capacity of 90.9 mA h g−1 at 7 C could be retained for NNZMTO thanks to the synergetic effect from Ti and Zn incorporation. This study provides deep insights for designing superior layered cathode via conducting a rational cations co-incorporation strategy.

Residual alkali-evoked cross-linked polymer layer for anti-air-sensitivity LiNi0.89Co0.06Mn0.05O2 cathode

High-energy density lithium-ion batteries (LIBs) with layered high-nickel oxide cathodes (LiNixCoyMn1−x−yO2, x ≥ 0.8) show great promise in consumer electronics and vehicular applications. However, LiNixCoyMn1−x−yO2 faces challenges related to capacity decay caused by residual alkalis owing to high sensitivity to air. To address this issue, we propose a hazardous substances upcycling method that fundamentally mitigates alkali content and concurrently induces the emergence of an anti-air-sensitive layer on the cathode surface. Through the neutralization of polyacrylic acid (PAA) with residual alkalis and then coupling it with 3-aminopropyl triethoxysilane (KH550), a stable and ion-conductive cross-linked polymer layer is in situ integrated into the LiNi0.89Co0.06Mn0.05O2 (NCM) cathode. Our characterization and measurements demonstrate its effectiveness. The NCM material exhibits impressive cycling performance, retaining 88.4% of its capacity after 200 cycles at 5 C and achieving an extraordinary specific capacity of 170.0 mA h g−1 at 10 C. Importantly, this layer on the NCM efficiently suppresses unfavorable phase transitions, severe electrolyte degradation, and CO2 gas evolution, while maintaining commendable resistance to air exposure. This surface modification strategy shows widespread potential for creating air-stable LiNixCoyMn1−x−yO2 cathodes, thereby advancing high-performance LIBs.

Aluminum and polyanion-doping to improve structural and moisture stability of Ni-rich layered oxides for lithium-ion batteries.

Ni-rich layered materials LiNi0.8Co0.1Mn0.1O2 attracts extensive interest to build high-performance lithium-ion batteries, but ground challenges, e.g., unfavorable phase transfer and interfacial parasitic reactions during cycling, especially after being exposure to the air for a long time, greatly limit their practical utilization. Here, we prove that those issues of Ni-rich layered materials can be alleviated by concurrently incorporating the Al3+ and PO34-, and conduct corresponding comprehensive studies to explore mechanisms of the enhanced electrochemical performances. It is suggested that the phase transition (H2 to H3) that related to the lattice contraction can be suppressed after Al3+ and PO34- co-doping, leading to improved cycling stability. Additionally, the co-doping successfully mitigates the chemical reaction between the Ni-based oxides and the ambient air, significantly improving the reversibility of lithium intercalation and charge transfer kinetics against long-time storage. Specifically, the Al3+ and PO34- co-doped material maintains 94.1% capacity retention of 150 cycles before storage, and 73.6% capacity retention of 100 cycles after being stored in ambient air for 30 days, which is much better than that of the undoped one.

Suppression of Jahn–Teller distortion in a layered Mn-based oxide cathode with Li substitution toward achieving stable K-storage

Li-substitution suppressed the Jahn–Teller distortion, restraining unfavorable phase transition in KMO, and decreases the diffusion energy barrier of K+, promoting the diffusion of K+, which provides excellent K-storage activity in KLMO electrodes.

Ultrathin dense LiF coverage coupled with a near-surface gradient fluorination lattice enables fast-charging long-life 4.6 V LiCoO2

Schematic diagram of the fluorination interfacial reconstruction process and mechanism for stabilizing the cathode/electrolyte interface.