O2 Cathode Research Articles

Impact of Fast-Charging Rates on Electrode Degradation in NMC/Gr Pouch Cells

With the rapid expansion of the electric vehicles market, fast charging lithium-ion batteries has become increasingly imperative and inevitable. However, as fast-charging technologies entering electric vehicle market, persistent challenges related to safety issue and cell degradation, such as lithium dendrite growth, thermal runaway etc. necessitate meticulous consideration. In this study, we investigated fast-charging rate effects on electrode degradation in 1.6 Ah pouch cells using LiNi0.5Mn 0.3Co 0.2O2 cathode and graphite anode provided by Nanoramic Laboratories. Our investigation involves a comparative analysis of the aging behavior of NMC/Gr cells subjected to various charging rates — 0.5C, 2C, 4C, and 6C. Notably, we observed that pouch cells charged at rates of 0.5C and 2C could persist 80% capacity retention over 1000 cycles while cells using 4C and 6C can survive no more than 400 cycles with 80% retention. Through a series of post-mortem characterizations, including electrochemical impedance spectroscopy (EIS), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), we scrutinized the harvested NMC and graphite electrodes. As expected, more dendrite formation was observed on graphite anodes with 4C and 6C fast charging rates. The deterioration of cell performance primarily resulted from the degradation of the graphite anode. This degradation could be attributed to distinct dendrite morphologies at the graphite anode under varying charging rates (see Fig. 1). In addition to dendrite formation on graphite electrodes, we observed more severe pulverization of NMC secondary particles under higher charging rates despite their lower cycle numbers. This investigation provides a comprehensive understanding of how NMC and graphite degrade under different charging rates, offering valuable insights into the practical impacts of charging rates on cell lifespan and highlighting potential challenges that need to be addressed.AcknowledgementThis material is based upon work supported by the U. S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Manufacturing Office, award number DE-EE0009111. Argonne National Laboratory is operated for DOE Office of Science by UChicago Argonne, LLC under contract number DE-AC02-06CH11357 Figure 1

Chemical Substitution Strategies for Tailoring P2- and O3-Type Layered Oxide Cathodes in Sodium-Ion Batteries

Among cathodes for sodium-ion batteries (SIBs), layered transition metal oxides Na x MO2 (M = transition metal) are very promising due to their easy synthesis and high theoretical capacity.1,2 In this class, Ni/Mn/Fe-based layered oxides are attractive due to the high redox potential of Ni2+/ Ni4+ and Jahn Teller inactive centers (Ni2+, Fe3+,and Mn4+).3 However, complex phase transitions, Na+/vacancy ordering and transition-metal (TM) migration degrade their electrochemical performances.4 To address the issues, a widely studied cathode- P2-type Na0.67[Ni0.33Mn0.67]O2 is chosen and Li+ is substituted in the TM-layer to tailor a series of high Na-content cathodes. Among them, Na0.85[Li0.14Ni0.29Mn0.57]O2 cathode with optimal Li-substitution exhibits a reversible capacity of 168 mAh g-1 at 0.1 C rate and good cycling stability (82% retention after 100 cycles).5 In-situ XRD measurement reveals a complete solid-solution formation and X-ray absorption spectroscopy studies confirm the participation of Ni4+/Ni2+ and Mn4+/Mn3+ redox couples during Na+-extraction/insertion. Lastly, a full Na-ion cell with hard carbon is demonstrated with an energy density of 420 Wh kg-1. In subsequent work, a Li and Ti co-substitution strategy is applied to design a high-entropy O3-type NaLixNiyFezMn0.5Ti0.5-aO2 cathode.6 It retains 77% of its initial capacity after 400 cycles at a 2 C rate with a facile O3-P3-OP2-P3-O3 phase transition. The co-substitution strategy uplifts the average voltage of the system, improves the reversibility of the high-voltage OP2 phase, and enhances the Na-ion diffusion rate. A mere 1.32% unit cell volume change and diminishing electrochemical cell resistance over cycling ensure its superior long-term cycling performance. A full cell is fabricated, which holds 62% of its initial capacity even after 1000 cycles at a 0.5 C rate. Therefore, mono- and di-ion substitution strategies hold enormous potential for designing high-performing P2- and O3-type cathode materials for practical SIBs. References T. Hosaka, K. Kubota, A. S. Hameed, and S. Komaba, Chem. Rev., 120, 6358–6466 (2020).J. Y. Hwang, S. T. Myung, and Y. K. Sun, Chem. Soc. Rev., 46, 3529–3614 (2017).F. Zhang, J. Liao, L. Xu, W. Wu, and X. Wu, ACS Appl. Mater. Interfaces, 13, 40695–40704 (2021).Z. Lu and J. R. Dahn, J. Electrochem. Soc., 148, A1225 (2001).A. Ghosh, B. Senthilkumar, S. Ghosh, P. Amonpattaratkit, and P. Senguttuvan, J. Electrochem. Soc., 170, 030538 (2023).A. Ghosh, R. Hegde, and P. Senguttuvan, J. Mater. Chem. A., submitted(2023).

Sustainable Electrochemical Recycling of Spent Lithium-Ion Batteries: Selective Extraction of Lithium and Direct Regeneration of De-Lithiated Material

The recycling of spent lithium-ion batteries has become an urgent imperative. In recent years, the rising demand for lithium has sparked interest in the selective extraction of lithium from spent LIBs cathode materials. This process is of interest as it can streamline processes, improve lithium recovery efficiency, and reduce processing costs. Electrochemical methods for selectively extracting lithium from spent cathode materials have gained significant attention among various selective extraction methods due to their advantages, such as low energy consumption and environmental friendliness. Despite substantial progress in improving the efficiency of lithium recovery through electrochemical methods, the economic returns from lithium salt products, to some extent, are still insufficient to offset the processing costs of the entire process, thereby limiting the further development of this technology. Therefore, it is necessary to develop reasonable strategies for the utilization of such de-lithiated materials to further enhance product yields. One promising strategy among these approaches is direct regeneration of fresh cathode materials from the de-lithiated material. However, due to a lack of clear understanding of the structural evolution of transition metal oxides during the lithium extraction process, and the lithiation mechanisms of lithium-depleted materials, there is currently no research report on the direct regeneration of such de-lithiated materials into battery materials.Herein, an electrochemical method using LiCl aqueous as electrolyte is developed to realize the selective extraction of lithium from spent polycrystal LiNi0.55Co0.15Mn0.3O2 (NCM) cathode materials, with a maximum de-lithiation rate approaching 90%. Thorough characterizations were conducted to monitor the morphological, structural, and compositional evolution of NCM during the electrochemical de-lithiation process. These findings contribute to a profound understanding of the characteristics of the de-lithiated material and inform the rational design of regeneration pathways tailored to such materials. The results reveal that the deep de-lithiation of NCM in lithium-aqueous electrolyte triggers water-molecule intercalation, leading to an unusual phase transformation beyond H1→H2→H3. This phase transformation causes substantial lattice expansion along c-axis and introduces severe lattice distortion in de-lithiated material. The over-expanded lattice and the presence of bulk defects resulted in an unstable structure, posing huge challenge for the subsequent direct regeneration of de-lithiated material using conventional calcination methods. To address this, we employ a hydrothermal re-lithiation process, characterized by a milder, lithium-rich and water-based environment. This process is able to create a “lithium-water-balance” structure for de-lithiated materials by promoting the lithium diffusion into the lithium-deficiency structure and facilitating the exchange between lithium ions and water molecules. This process effectively enhances structural stability of the de-lithiated material. As a result, subsequent calcination successfully converts the degraded structure back into the original lithium-conductive layer structure by further eliminating the remaining lattice defects in material and promoting the cation rearrangement. The regenerated material exhibits decent electrochemical performances, which delivers a capacity of 153.2 mAh g−1 at 1C and 132.5 mAh g− 1 at 5C. This work provides insights into the electrochemical de-lithiation method and fills a gap in the utilization of de-lithiated NCM, paving the way for the sustainable recycling of spent LIBs.

Stable Hydroborate Solid-State Lithium Battery with High-Voltage NMC811 Cathode

Hydroborate solid electrolytes offer high ionic conductivity and are stable in contact with alkali metal anodes, but are challenging to integrate into batteries with high-voltage cathodes [1-3]. Here, we demonstrate stable dis-/charge cycling of solid-state lithium-ion batteries combining a Li3(CB11H12)2(CB9H10) hydroborate electrolyte with a 4 V-class LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, exploiting the enhanced kinetic stability of the LiCB11H12-rich and LiCB9H10-poor electrolyte composition [4]. Cells with lithium metal and indium/lithium anodes achieve a discharge capacity at C/10 of ~145 mAh g–1 at room temperature and ~175 mAh g–1 at 60 °C. Indium/lithium cells retain 98% of their initial discharge capacity after 100 cycles at C/5 and 70% after 1000 cycles at C/2. Capacity retention of 97% after 100 cycles at C/5 and 75% after 350 cycles at C/2 is also achieved with a graphite anode without any excess lithium. The energy density per cathode composite weight of 460 Wh kg–1 is on par with the best solid-state batteries reported to date.[1] L. Duchêne, A. Remhof, H. Hagemann, D. Battaglia, Energy Storage Materials, 2020, 225, 782[2] L. Duchêne, R.-S. Kühnel, E. Stilp, E. Cuervo Reyes, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2017, 10, 2609[3] R. Asakura, D. Reber, L. Duchêne, S. Payandeh, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2020, 13, 5048[4] H. Braun, Ryo Asakura, A. Remhof, C. Battaglia, ACS Energy Lett. in press

Influence of Pristine NMC811 Secondary and Primary Particle Surfaces on the Materials Reactivity

Vehicle electrification currently relies on lithium-ion batteries using nickel, manganese and cobalt (NMC)-based lamellar oxides as positive electrode materials. In order to achieve higher energy densities, the market is now moving towards NMC with high nickel content. Nevertheless, these materials have been widely demonstrated to suffer from serious off-gassing problems that reduce cycle life and pose safety concerns. Not only gases resulting from the formation of SEI at the negative electrode, but the production of O2, CO and CO2 have also been noted by different research groups.1–3 Despite the large number of studies analyzing the material during and after cycling, we noted a lack of in-depth characterization of the surface of Nickel-rich NMCs in their initial state. The need for such information is increasingly necessary with the recent development of new technologies for surface modification such as coating to limit the instability of high Nickel content NMCs.4,5 The surface reactivity of Ni-rich layered transition metal oxides is instrumental to the performance of batteries based on these positive electrode materials. Most often, strong surface modifications are detailed with respect to a supposed ideal initial state. The study the LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material in its pristine state, hence before any contact with electrolyte or cycling, was performed thanks to advanced microscopy and spectroscopy techniques in order to fully characterize its surface down to the nanometer scale. Scanning transmission-electron microscopy-electron energy-loss spectroscopy (STEM-EELS), solid state nuclear-magnetic-resonance (SS-NMR) and X-rays photoelectron spectroscopy (XPS) are combined and correlated in an innovative manner.Specifically, using a high magnetic field NMR spectrometer, it was possible to evaluate the total amount of diamagnetic Li in the samples. Thanks to XPS it was then possible to identify the lithiated species present on the surface and to use such information to better deconvolve the NMR spectra. Li2O, Li2SO4 and LiOH were identified as the main contaminants on the surface of NMC in its initial state. On the other hand, the quantity of Li2CO3 initially estimated by XPS could be substantially re-evaluated using NMR (54% by XPS vs. only 1% by NMR). These two techniques, providing only partial and often imprecise information when used separately, have proven to be fundamental instruments in the analysis of surface species when used in a complementary manner.The results demonstrate that in usual storage conditions after synthesis, the extreme surface is already chemically different from nominal values. In particular, nickel is found in a reduced state compared to the bulk value and a Mn enrichment is determined in the first few nanometers of primary particles. Further exposition to humid air allows for quantifying the formed lithiated species per gram of active material, identifying their repartition and proposing a reaction path in relation with the instability of the surface. Modifying synthesis conditions impacts noticeably the previously identified surface particularities and, consequently, the materials reactivity.References :(1) Jung, R.; Metzger, M.; Maglia, F.; Stinner, C.; Gasteiger, H. A. Oxygen Release and Its Effect on the Cycling Stability of LiNixMnyCozO2 (NMC) Cathode Materials for Li-Ion Batteries. Journal of The Electrochemical Society 2017, 164 (7), A1361–A1377. https://doi.org/10.1149/2.0021707jes.(2) Renfrew, S. E.; McCloskey, B. D. Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2 and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides. J. Am. Chem. Soc. 2017, 139 (49), 17853–17860. https://doi.org/10.1021/jacs.7b08461.(3) Renfrew, S. E.; McCloskey, B. D. The Role of Electrolyte in the First-Cycle Transformations of LiNi 0.6 Mn 0.2 Co 0.2 O 2. J. Electrochem. Soc. 2019, 166 (13), A2762–A2768. https://doi.org/10.1149/2.1561912jes.(4) Zhang, H.; Liu, H.; Piper, L. F. J.; Whittingham, M. S.; Zhou, G. Oxygen Loss in Layered Oxide Cathodes for Li-Ion Batteries: Mechanisms, Effects, and Mitigation. Chem. Rev. 2022, acs.chemrev.1c00327. https://doi.org/10.1021/acs.chemrev.1c00327.(5) Manthiram, A.; Song, B.; Li, W. A Perspective on Nickel-Rich Layered Oxide Cathodes for Lithium-Ion Batteries. Energy Storage Materials 2017, 6, 125–139. https://doi.org/10.1016/j.ensm.2016.10.007. Figure 1

Understanding Ni-Rich Layered Cathode Materials for Fast-Charging Li-Ion Batteries

The market for electric vehicles (EVs) has experienced significant growth, and this trend is expected to continue in the coming years. While the lithium-ion battery (LIB) technologies for EVs have made significant progress so far, they still face several disadvantages compared to the internal combustion engines. A predominate challenge is reducing battery charging time. [1] Traditional LIBs typically use Li[Ni1-x-yCox(Mn and/or Al)y]O2 as cathode materials. To improve the driving range of EVs, energy density has been the focus of research and development in the past decade, which led to the wide adoption of Ni-rich (Ni content > 80%) layered oxide cathodes in LIBs.[2] With increasing Ni content, however, the structural changes that the cathode material undergoes during electrochemical reactions also become more severe, which negatively impact their fast-charging performances.[3-5] It is evident that addressing the fast charging limitations requires a deep understanding of the active materials. In this presentation, we show our recent effort in improving fast charging performances of Ni-rich layered cathodes. As the reactivity of Li[Ni1-x-yCox(Mn and/or Al)y]O2 cathodes vary with the states of dis/charges, their fast charging performances are directly linked to the charging/discharging protocol. In addition, we report how various physical properties of the cathode materials, such as microstructures and facets, can affect kinetics and charging rates. Our perspectives on future development strategies for fast charging Ni-rich layered cathode materials will also be discussed.[1] X. Wang, Y.-L. Ding, Y.-P. Deng, Z. Chen, Adv. Energy Mater. 2020, 10, 1903864.[2] S.-T. Myung; F. Maglia; K.-J. Park; C. S. Yoon; P. Lamp; S.-J. Kim; Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.[3] F. Schipper; E. M. Erickson; C. Erk; J.-Y. Shin; F. F. Chesneau; D. Aurbach, J. Electrochem. Soc. 2017, 164, A6220.[4] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater. 2018, 30, 1155.[5] J. Park, H. Zhao, S. D. Kang, K. Lim, C.-C. Chen, Y.-S. Yu, R. D. Braatz, D. A. Shapiro, J. Hong, M. F. Toney, M. Z. Bazant, W. C. Chueh, Nat. Mater. 2021, 20, 991.

High-Valence Ion Doped Compositionally Partitioned Li[Ni0.78Co0.10Mn0.12]O2 Cathode for Advanced Lithium-Ion Batteries

Numerous approaches have been employed to reduce the intrinsic instability of Ni-rich cathodes. Among them, the introduction of concentration gradient (CG), i.e., a strategy to protect the labile Ni-enriched compartment with a chemically protective Mn-rich shell, has proven successful in commercial applications.1 However, because the segmentation of transition metal (TM) constituents and the formation of unique geometric configurations are characteristics inherited from the CG hydroxide precursor; it is crucial to select the optimal calcination temperature and precisely control it.2 Excessive thermal energy input can result in concentration planarization because the CG of the hydroxide precursor is intrinsically susceptible to the interdiffusion of TM elements during lithiation. Moreover, the immoderate coarsening of the primary particles can eliminate the advantageous features of the CG design by producing equiaxed primary particles.2 In this study, we propose a strategy that can effectively ameliorate the deterioration of Ni-rich CG cathodes resulting from excessive thermal energy input and remarkably improve their electrochemical cycling performance. It was revealed that a trace amount of tungsten incorporation during the cathode calcination can effectively mitigate the high-temperature-induced cathode degeneration and maintain outstanding product quality over a wide range of temperatures. Thus, the proposed strategy opens new avenues for the facile synthesis of long-life Ni-rich CG cathodes. Reference s : [1] Y.-K. Sun, S.-T. Myung, B.-C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 8 (2009) 320-324.[2] G.-T. Park, H.-H. Ryu, T.-C. Noh, G.-C. Kang, Y.-K. Sun, Mater. Today 52 (2022) 9-18.

Colloid Electrolyte Containing Li3P Nanoparticles for Highly Stable 4.7 V Lithium Metal Batteries.

Lithium metal batteries (LMBs) with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes have garnered significant interest as next-generation energy storage devices due to their high energy density. However, the instability of their electrode/electrolyte interfaces in regular carbonate electrolytes (RCEs) results in a rapid capacity decay. To address this, a colloid electrolyte consisting of Li3P nanoparticles uniformly dispersed in the RCE is developed by a one-step synthesis. This design concurrently creates stable cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) on both electrode surfaces. The cathode interface derived from this colloid electrolyte significantly facilitates the decomposition of Li salts (LiPF6 and LiDFOB) on the cathode surface by weakening the P-F and B-F bonds. This in situ formed P/LiF-rich CEI effectively protects the NCM811 cathode from side reactions. Furthermore, the Li3P embedded in the SEI optimizes and homogenizes the Li-ion transport, enabling dendrite-free Li deposition. Compared to the RCE, the designed colloid electrolyte enables robust cathode and anode interfaces in NCM811||Li full cells, minimizing gas and dendrite formation, and delivering a superior capacity retention of 82% over 120 cycles at a 4.7 V cutoff voltage. This approach offers different insights into electrolyte regulation and explores alternative electrolyte shapes and formulations.

Manipulating Interfacial Renovation via In Situ Formed Metal Fluoride Heterogeneous Protective Layer toward Exceptional Durable Sodium Metal Anodes

AbstractSodium metal is regarded as an optimal anode material for high‐energy‐density sodium‐ion batteries (SIBs). However, during the processes of sodium deposition and stripping, the failure of the solid electrolyte interphase (SEI) film leads to the continuous accumulation of inactive sodium, thereby compromising the cycling reversibility of the battery. Here, a novel metal fluoride heterointerface layer is generated and constructed through in situ manipulation of the continuous reaction between TiF4 and metal Na. The reconstructed NaF/TiF3 interface layer, which tightly anchors the sodium metal, effectively suppresses the formation of sodium dendrites during the charge‐discharge process. The highly sodium‐philic TiF3 component exhibits strong binding with Na ions, while NaF reduces the Na+ diffusion energy barrier, significantly enhancing the reaction kinetics. Due to the successful artificial construction of this interface layer, the Na/TiF4 composite electrode demonstrates an exceptional ultra‐long cycling stability of 2370 h in symmetric cells (0.5 mAh cm−2). Density functional theory (DFT) calculations further validate the functionality of each component in the Na/TiF4 protective layer. When paired with NaNi1/3Fe1/3Mn1/3O2 cathode in a pouch cell, it exhibits stability up to 2000 cycles at current densities of 2 C and 4 C, with a maximum energy density output of 483.1 Wh kg−1 (power density: 320.8 W kg−1).

Operando chemo-mechanical evolution in LiNi0.8Co0.1Mn0.1O2 cathodes.

Ni-rich LiNi x Co y Mn z O2 (NCMxyz, x+y+z=1, x≥0.8) layered oxide materials are considered the main cathode materials for high-energy-density Li-ion batteries. However, the endless cracking of polycrystalline NCM materials caused by stress accelerates the loss of active materials and electrolyte decomposition, limiting the cycle life. Hence, understanding the chemo-mechanical evolution during (de)lithiation of NCM materials is crucial to performance improvement. In this work, an optical fiber with με resolution is designed to in operando detect the stress evolution of a polycrystalline LiNi0.8Co0.1Mn0.1O2 (P-NCM811) cathode during cycling. By integrating the sensor inside the cathode, the stress variation of P-NCM811 is completely transferred to the optical fiber. We find that the anisotropy of primary particles leads to the appearance of structural stress, inducing the formation of microcracks in polycrystalline particles, which is the main reason for capacity decay. The isotropy of primary particles reduces the structural stress of polycrystalline particles, eliminating the generation of microcracks. Accordingly, the P-NCM811 with an ordered arrangement structure delivered high electrochemical performance with capacity retention of 82% over 500 cycles. This work provides a brand-new perspective with regard to understanding the operando chemo-mechanical evolution of NCM materials during battery operation, and guides the design of electrode materials for rechargeable batteries.

Regulating the horizontal confined deposition of lithium metal by Co-Nx modified honeycomb-like carbon nanosheets

The uncontrollable Li dendrite growth as well as the severe volume expansion of Li metal anodes during cycling significantly impedes the practical applications of high-energy-density Li metal batteries. In this work, an innovative modulation strategy has been developed by constructing honeycomb-like nitrogen-doped carbon nanosheets with uniformly anchored cobalt nanoparticles (denoted as Co@HNC) for regulating the Li deposition behavior and meanwhile alleviating volume change during cycling. On one hand, the lithiophilic Co-Nx sites can largely reduce the energy barrier of Li nucleation and subsequently guide horizontal confined Li deposition in the honeycomb-like holes of Co@HNC, which is verified by the density functional theory calculations and in-situ optical microscopy observations. On the other hand, the honeycomb-like carbon framework with good structural integrity can endure the huge volume change during repeated Li plating/stripping processes. Consequently, the optimized Co@HNC electrode delivered a promoted cycling life for over 600 times with high Coulombic efficiency of 98.5 % at 1 mA cm−2. When matched with the high-mass-loading LiFePO4 (20 mg cm−2) or high-voltage LiNi0.8Mn0.1Co0.1O2 cathode, the Li@Co@HNC anode exhibited outstanding cycling stability and rate capability under low negative/positive capacity ratio, demonstrating its great potential in practical applications of high-energy-density lithium metal batteries.

A facile ice‐templating‐induced puzzle coupled with carbonization strategy for kilogram‐level production of porous carbon nanosheets as high‐capacity anode for lithium‐ion batteries

AbstractTwo‐dimensional porous carbon nanosheets (PCNSs) are considered promising anodes for lithium‐ion batteries due to their synergetic features arising from both graphene and porous structures. Herein, using naturally abundant and biocompatible sodium humate (SH) as the precursor, PCNSs are prepared from the laboratory scale up to the kilogram scale by a method of a facile ice‐templating‐induced puzzle coupled with a carbonization strategy. Such obtained SH‐derived PCNSs (SH‐PCNSs) possess a hierarchical porous structure dominated by mesopores having a specific surface area (~127.19 2 g−1), pore volume (~0.134 cm3 g−1), sheet‐like morphology (~2.18 nm in thickness), and nitrogen/oxygen‐containing functional groups. Owing to these merits, the SH‐PCNSs present impressive Li‐ion storage characteristics, including high reversible capacity (1011 mAh g−1 at 0.1 A g−1), excellent rate capability (465 mAh g−1 at 5 A g−1), and superior cycle stability (76.8% capacitance retention after 1000 cycles at 5 A g−1). It is noted that the SH‐PCNSs prepared from the kilogram‐scale production procedure possess comparable electrochemical properties. Furthermore, coupling with a LiNi1/3Co1/3Mn1/3O2 cathode, the full cells deliver a high capacity of 167 mAh g−1 at 0.2 A g−1 and exhibit an outstanding energy density of 128.8 Wh kg−1, highlighting the practicability of this porous carbon nanosheets and the potential commercial opportunity of the scalable processing approach.

Nonflammable All-Fluorinated Electrolyte Enabling High-Voltage and High-Safety Lithium-Ion Cells.

In this study, a nonflammable all-fluorinated electrolyte for lithium-ion cells with a Li(Ni0.8Mn0.1Co0.1)O2 cathode is investigated under high voltages. This electrolyte, named FT46, consists of fluoroethylene carbonate (FEC) and bis(2,2,2-trifluoroethyl) carbonate (TFEC) in a mass ratio of 4:6. Compared to a commercially available electrolyte and several other fluorinated electrolytes, cells containing FT46 demonstrate significantly better cycling performances under high voltage (3.0-4.5 V). This result may be ascribed to the generation of a stable, smooth, and thin passivation layer and the improved solvation structure formed by FT46. The LiF-rich passivation layer strengthens the electrode/electrolyte interface, inhibits the degradation of the electrode, and suppresses side reactions between the electrodes and electrolytes under high voltage. The solvation structure formed by FT46 is derived from anions, enabling an enhanced Li+ migration rate and inhibiting lithium plating generation. Additionally, due to the nonflammability of the electrolyte and the stable passivation layers, FT46 cells also demonstrate promising safety characteristics when exposed to typical abusive conditions, such as thermal abuse, mechanical abuse, and electrical abuse.

Unlocking the potential of cation vacancy-enriched ZnMn1.75O4 cathode for advanced aqueous aluminum-ion batteries

Manganese oxides are widely utilized in aqueous aluminum-ion batteries (AIBs) due to their high voltage and diverse crystal structures. However, the Jahn-Teller effect induced by Mn-O6 units results in irreversible structural damage. Here, we synthesized ZnMn1.75O4 (ZMO) cathodes loaded onto a carbon framework with manganese vacancies (VMn) for AIBs through ion substitution, manganese extraction, and carbonization on Mn-MIL. VMn stabilizes the ZMO structure by damping Mn-O bond vibrations and fosters Mn-O-C bonds between oxide particles and the carbon framework, effectively suppressing irreversible Mn2+ dissolution. Vacancy-modified cathodes provide more ion insertion sites, promoting ion diffusion. Ex-situ characterization revealed dominant H+ and Al3+ insertion behavior during different voltage regimes. Upon initial discharge, ion insertion into vacant lattice sites causes lattice distortions in adjacent unit cells, prompting ZMO to undergo a crystal structure transition and partial zinc deintercalation, resulting in a more stable cathode structure. Therefore, Al/ZMO batteries exhibit enhanced electrochemical performance.

Ribbon-Ordered Superlattice Enables Reversible Anion Redox and Stable High-Voltage Na-Ion Battery Cathodes.

High-voltage layered oxide cathodes attract great attention for sodium-ion batteries (SIBs) due to the potential high energy density, but high voltage usually leads to rapid capacity decay. Herein, a stable high-voltage NaLi0.1Ni0.35Mn0.3Ti0.25O2 cathode with a ribbon-ordered superlattice is reported, and the intrinsic coupling mechanism between structure evolution and the anion redox reaction (ARR) is revealed. Li introduction constructs a special Li-O-Na configuration activating reversible nonbonded O 2p (|O2p)-type ARR and regulates the structure evolution way, enabling the reversible Li ions out-of-layer migration instead of the irreversible transition metal ions out-of-layer migration. The reversible structure evolution enhances the reversibility of the bonded O 2p (O2p)-type ARR and inhibits the generation of oxygen dimers, thus suppressing the irreversible molecular oxygen (O2)-type ARR. After the structure regulation, the structure evolution becomes reversible, |O2p-type ARR is activated, O2p-type ARR becomes stable, and O2-type ARR is inhibited, which largely suppresses the capacity degradation and voltage decay. The discharge capacity is increased from 154 to 168 mA h g-1, the capacity retention after 200 cycles significantly increases from 35 to 84%, and the voltage retention increases from 78 to 93%. This study presents some guidance for the design of high-voltage, O3-type oxide cathodes for high-performance SIBs.

Preparation and Property Optimization of High Capacity O3-type NaNi0.4Fe0.2Mn0.4O2

O3-type NaNi0.4Fe0.2Mn0.4O2 cathode materials are structurally stable and have a high nickel content, allowing for stable high-capacity output. However, their performance needs further improvement. First, we investigated the effects of different sodium contents on the structure, morphology, and electrochemical performance of NaxNi0.4Fe0.2Mn0.4O2(x = 0.85, 0.9, 0.95, 1, 1.05) materials. The Na0.9Ni0.4Fe0.2Mn0.4O2 material exhibited initial discharge specific capacities of 148.11 and 181.80 mAh·g−1 at voltage ranges of 2–4.1 V and 2–4.2 V, respectively. To further optimize the cycling performance of the material, we doped NaNi0.4Fe0.2Mn0.4O2 with different calcium contents. Ca2+ doping significantly enhanced the electrochemical performance of the material. Subsequently, we synthesized Na0.96Ca0.02(NMF)0.95Zn0.05O2, and the dual-doped NMF-Ca0.02Zn0.05 maintains approximately 80% capacity retention at 1–4.05 V, and around 70% as the cut-off voltage increases to 4.15 V in full cells.

Multifunctional nitrile additives for inducing pseudo-concentration gel-polymer electrolyte: Enabling stable high-voltage lithium metal batteries

High-voltage lithium metal batteries (LMBs) are promising for next-generation high-energy storage systems. Unfortunately, their implementation has been severely plagued by the interfacial instability between the high-voltage cathodes/lithium metal (LM) anodes and electrolytes. To tackle these challenges, a novel nitrile additive, 1,4-dicyanobenzene (DCB) (Synonyms: terephthalonitrile), is added to the in situ polymerized pentaerythritol tetraacrylate-based gel polymer electrolyte (GPE). The DCB additive, as demonstrated both theoretically and experimentally, plays a crucial role in altering the Li+ coordinated solvation structure within the GPE. This alteration leads to the formation of a pseudo-concentrated electrolyte with a tightly packed Li+ cluster, expanding the electrochemical stability window of the electrolyte. Moreover, the DCB-included GPE significantly improves its compatibility with both LM anode and high-voltage cathode, attributed to the modified solvation structure and the generated LiF-rich electrolyte/electrode interphases. Accordingly, the GPE enables stable cyclic performance of LMBs based on a 4.9 V LiNi0.5Mn1.5O4 cathode at a low relative negative/positive ratio of 4, achieving a high reversible capacity of 123.8 mAh g−1 with a capacity retention of 87.7 % over 500 cycles at 0.5 C. This work provides new insights into enhancing the cyclability of high-voltage LMBs via the synergistic effect of additives and GPE.

Electronic modification of NaCrO2 via Ni2+ substitution as efficient cathode for sodium-ion batteries

The feature of high theoretical capacity, long thermal stability, and low-cost fabrication offers the layered transition metal oxide NaCrO2 as an excellent candidate for sodium-ion batteries. Here, we show an effective method for electronic modulation of NaCrO2 by partial substitution of Cr3+ with low-valent Ni2+ to produce NaCr0.95Ni0.05O2 as an efficient cathode for these batteries. We found that Ni2+ substitution plays a critical role in the ionic character of transition metal-oxygen bonds, which increases the interlayer separation and thus improves sodium-ion diffusion kinetics. Furthermore, Ni2+ substitution reduces the deterioration of NaCrO2 throughout charge-discharge processes and thus boosts the cycle performance of the materials. The resultant NaCr0.95Ni0.05O2 cathode displays a remarkable rate performance with specific capacities of 91.2 mAh g-1 at 50 C and a high retention (~80%) of the initial capacity after cycling for 1,000 cycles at 10 C.

Ab initio study on changing behaviors of lithium-rich layered composite cathode materials

The lithium-rich composite-layered oxide, xLi2MnO3•(1-x)LiM'O2, where M’ represents transition metals, is a promising cathode material with excellent capacity at high working voltage for lithium-ion batteries (LIBs). Nevertheless, an unusual charge-discharge feature is observed for this material with sloping and plateau regions during the initial charging. In this work, ab initio calculations based on density functional theory were employed to examine the stability of xLi2MnO3•(1-x)Li(Ni1/3Co1/3Mn1/3)O2 composite-layered cathode materials during the first charging. Optimized atomistic models for different compositions (x = 0.0, 0.3, 0.4, 0.5, 0.7, and 1) unveil a pseudo-rhombohedral or monoclinic-like structure within the solid solution phase, with simulated X-ray diffraction patterns closely matching experimental data. Using these atomistic models, the first charging process of the 0.4Li2MnO3•0.6Li(Ni1/3Co1/3Mn1/3)O2 cathode were investigated. There exists phase transition from a layered to a spinel structure. Additionally, Bader charge analysis reveals intriguing trends during the first delithiation process, where the valence states of Ni and Co gradual increase, while that of Mn almost remains unchanged. Simultaneously, significant oxidation of O is observed. This finding leads to further evaluations on oxygen vacancy formation in comparison to the energy required for delithiation. Defect formation energy calculations demonstrate that the plateau in charging curve is resulted from oxygen vacancy formation during the first charging. By empirical fitting oxygen chemical potential at μO = -1.200 eV, the calculated charging-discharging curves aligned well with experimental data during the first and second charging. Furthermore, the pathways of lithium and oxygen deintercalation are elucidated. This work contributes fundamental understandings on the xLi2MnO3•(1-x)LiM'O2 composite-layered oxides as cathode for LIBs, providing valuable guidance for further developments in high-capacity Co-lean cathode materials.

Acetonitrile-Based Local High-Concentration Electrolytes for Advanced Lithium Metal Batteries.

Acetonitrile (AN) is a compelling electrolyte solvent for high-voltage and fast-charging batteries, but its reductive instability makes it incompatible with lithium metal anodes (LMAs). Herein, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is used as the diluent to build an AN-based local high-concentration electrolyte (LHCE) to realize dense, dendrite-free, and stable LMAs. Such LHCE exhibits an exceptional electrochemical stability window close to 6V (vs Li+/Li), excellent wettability, and promising flame retardancy. Compared to a baseline carbonate-based electrolyte, its electrochemical performance is prominent: the overpotential of lithium nucleation is minimal (only 24mV), the average half-cell coulombic efficiency (CE) reaches 99.5% at 0.5mAcm-2, and its practicality in full cells with LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes is also demonstrated. Compounding factors are identified to decipher the superiority of the AN-based LHCE. From the respect of solvation structures, both the elimination of free AN molecule and the diluent separation would contribute to prevention of anodic AN decomposition. Based on cryogenic electron microscopy (Cryo-EM) characterization and theoretical simulations results, the produced solid-electrolyte interphase (SEI) layer is uniform and compact. Thus, this work demonstrates a successful application of AN-based electrolytes in LMAs-traditionally deemed impractical-via the combined regulation of solvation and SEI structures.