O2 Cathode Research Articles

Enhancing High‐Voltage LNMO Cathode Performance in Li‐Metal Batteries Via Anionic Electrolyte Additive‐Integrated CEI Engineering

AbstractAn anionic‐additive electrolyte system is introduced by incorporating Lithium tetrafluoroborate (LiBF4) into a conventional base electrolyte for high‐voltage LiNi₀.₅Mn₁.₅O₄ (LNMO) cathodes in lithium‐metal batteries. At high voltages, the sacrificial oxidation of LiBF4 mitigates electrolyte degradation and forms a robust cathode electrolyte interface (CEI) enriched with boron and fluorine‐based components, which protects against active material corrosion. Density Functional Theory (DFT) studies reveal that BF₄⁻ is more readily oxidized, while MD simulations validate the CEI's inorganic composition. Initial cycling with a specialized charge‐discharge protocol ensures optimal use of the additive, resulting in a uniform, thin (4–6 nm) CEI on the LNMO cathode. The CEI formed in anionic‐additive electrolyte system effectively suppresses transition metal dissolution and surface degradation, enhancing long‐term cycling performance. The LiBF4‐enhanced electrolyte also lowers overpotential and promotes more uniform Li deposition compared to the base electrolyte. At a 1 C‐rate, the LNMO cathode with a Li metal anode and optimized electrolyte achieves a discharge capacity of 115 mA h g⁻¹ and an energy density of 540 Wh kg⁻¹ over 500 cycles. These findings underscore LiBF4’s dual role in protecting LNMO cathodes and Li metal anodes, highlighting the critical role of additives in CEI development for advanced lithium‐metal batteries.

Influence of Process Conditions During Aqueous and Direct Recycling of NMC811 Cathodes.

This study investigated the impact of various process conditions on the aqueous, direct recycling of LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Three model systems were used. The first system assumes that the current collector delamination is performed in a dry environment without the use of water as a process medium. Consequently, the NMC811 is only exposed to water during classification, where no aluminum foil is present. The second model system assumes that the current collector delamination occurs in water. Therefore, the NMC811 is exposed to water in the presence of aluminum foil. Due to the pH increase caused by the Li+/H+ exchange reaction, the pH value surpasses the stability window of the aluminum-oxide passivation layer (pH 4.5-8.5), resulting in the deposition of aluminum-containing species on the NMC811 surface. The third model system is identical to the second, with the exception that H3PO4 is added. This causes the pH to decrease and prevents corrosion of the aluminum foil. The findings reveal that process conditions significantly affect the surface chemistry on NMC811, influencing electrochemical performance. Notably, aluminum-containing species increase polarization. Heat treatment simulating regeneration led to cation mixing as surface species diffused into the NMC811 bulk structure, highlighting the need to control recycling process conditions.

Revealing the Dual Role of Ammonia in the Hydroxide Co-precipitation Synthesis of Cobalt-free Nickel-rich LiNi0.9Mn0.05Al0.05O2 (NMA955) Cathode Materials for Lithium-ion Batteries.

Nickel-rich cobalt-free LiNi0.9Mn0.05Al0.05O2 (NMA955) is considered a promising cathode material to address the scarcity and soaring cost of cobalt. Particle size and elemental composition significantly impact the electrochemical performance of NMA955 cathodes. However, differences in precipitation rates among metal ions coveys a challenge in obtaining cathode materials with the desired particle size and composition via hydroxide co-precipitation synthesis. Utilizing complexing agents like ammonia offers an effective strategy to tackle these issues. Here, we investigate the optimal ammonia concentration to achieve moderate particle size and precise material composition. Although ammonia only forms complex coordination with transition metals, its concentration also affects the final product's precipitation and composition, including aluminum. This study shows that ammonia serves a dual function in NMA synthesis via hydroxide co-precipitation, i.e., regulating particle size and adjusting elemental composition. It was found that an ammonia concentration of 1.2 M achieved optimal particle size and composition, resulting in superior electrochemical performance. NMA955 synthesized in 1.2 M ammonia demonstrated a high specific capacity of 188.12 mAh g-1 at 0.1C, retained 71.16% of its capacity after 200 cycles at 0.2C, and delivered 110.30 mAh g-1 at 5C. These results suggest tuning ammonia concentration is crucial for producing high-performance cathode materials.

Ultra‐Tough Dynamic Supramolecular Ion‐Conducting Elastomer Induced Uniform Li+ Transport and Stabilizes Interphase Ensures Dendrite‐Free Lithium Metal Anodes

AbstractArtificial polymer solid electrolyte interphases (SEIs) with microphase‐separated structures provide promising solutions to the inhomogeneity and cracking issues of natural SEIs in lithium metal batteries (LMBs). However, achieving homogeneous ionic conductivity, excellent mechanical properties, and superior interfacial stability remains challenging due to interference from hard‐phase domains in ion transport and solid‐solid interface issues with lithium metal. Herein, we present a dynamic supramolecular ion‐conducting poly (urethane‐urea) interphase (DSIPI) that achieves these three properties through modulating the hard‐phase domains and constructing a composite SEI in situ. The soft‐phase polytetrahydrofuran backbone, featuring loose Li+−O coordinating interactions, ensures uniform Li+ transport. Concurrently, sextuple hydrogen bonds in the hard phase dissipate strain energy through sequential bond cleavage, thereby imparting exceptional mechanical properties. Moreover, enriched bis (trifluoromethanesulfonyl) imide anion (TFSI−) in DSIPI promotes the in situ formation of a stable polymer‐inorganic composite SEI during cycling. Consequently, the DSIPI‐protected lithium anode (DSIPI@Li) enables symmetric cells with exceptional cyclability exceeding 4,000 hours at an ultra‐high current density of 20 mA cm−2, thereby demonstrating excellent cycling stability. Furthermore, DSIPI@Li facilitates stable operation of the pouch cells under the constraints of a high‐loading LiNi0.8Co0.1Mn0.1O2 cathode and low negative/positive capacity (N/P) ratio. This work presents a powerful strategy for designing artificial SEIs and high‐performance LMBs.

A New Class of Oxyhalide Solid Electrolytes NaNbCl6‐2xOx for Solid‐state Sodium Batteries

AbstractSodium‐based batteries are gaining momentum due to the abundance and lower cost of sodium compared to lithium. Solid‐state sodium batteries can also provide further safety advantages. However, sodium‐based solid‐state electrolytes (SSEs) that meet all the rigorous requirements, such as high ionic conductivity, oxidative stability with the cathode, and ease of processability, are lacking. We present here a new class of sodium‐based oxyhalide electrolytes NaNbCl6‐2xOx with a facile mechanochemical synthesis. The oxyhalide NaNbCl4O exhibits close to two orders of magnitude higher ambient‐temperature sodium‐ion conductivity (1.03×10−4 S cm−1) compared to the halide counterpart NaNbCl6 (3×10−6 S cm−1). Structural motifs unique to the oxygen content in NaNbCl6‐2xOx are identified with 23Na and 93Nb magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and x‐ray diffraction (XRD). Solid‐state sodium batteries assembled with NaNbCl4O electrolyte and the cobalt‐ and nickel‐free layered Na0.70Fe0.3Mn0.65Al0.05O2 cathode exhibit a maximum discharge capacity of 155 mAh g−1 with good cycle life at ambient temperature.

Ultra-Tough Dynamic Supramolecular Ion-Conducting Elastomer Induced Uniform Li+ Transport and Stabilizes Interphase Ensures Dendrite-Free Lithium Metal Anodes.

Artificial polymer solid electrolyte interphases (SEIs) with microphase-separated structures provide promising solutions to the inhomogeneity and cracking issues of natural SEIs in lithium metal batteries (LMBs). However, achieving homogeneous ionic conductivity, excellent mechanical properties, and superior interfacial stability remains challenging due to interference from hard-phase domains in ion transport and solid-solid interface issues with lithium metal. Herein, we present a dynamic supramolecular ion-conducting poly (urethane-urea) interphase (DSIPI) that achieves these three properties through modulating the hard-phase domains and constructing a composite SEI in situ. The soft-phase polytetrahydrofuran backbone, featuring loose Li+-O coordinating interactions, ensures uniform Li+ transport. Concurrently, sextuple hydrogen bonds in the hard phase dissipate strain energy through sequential bond cleavage, thereby imparting exceptional mechanical properties. Moreover, enriched bis (trifluoromethanesulfonyl) imide anion (TFSI-) in DSIPI promotes the in situ formation of a stable polymer-inorganic composite SEI during cycling. Consequently, the DSIPI-protected lithium anode (DSIPI@Li) enables symmetric cells with exceptional cyclability exceeding 4,000 hours at an ultra-high current density of 20 mA cm-2, thereby demonstrating excellent cycling stability. Furthermore, DSIPI@Li facilitates stable operation of the pouch cells under the constraints of a high-loading LiNi0.8Co0.1Mn0.1O2 cathode and low negative/positive capacity (N/P) ratio. This work presents a powerful strategy for designing artificial SEIs and high-performance LMBs.

Understanding of a Ni-Rich O3-Layered Cathode for Sodium-Ion Batteries: Synthesis Mechanism and Al-Gradient Doping.

O3-type NaNi0.8Mn0.1Co0.1O2 (NaNMC811) cathode active materials for sodium-ion batteries (SIBs), with a theoretical high specific capacity (∼187mAhg-1), are in the preliminary exploration stage. This study comprehensively investigates NaNMC811 from multiple perspectives. For the first time, the phase evolution ( - - ) during the solid-state synthesis is systemically investigated, which elucidates in-depth the mechanisms of the thermal sodiation process. Furthermore, an Al-gradient doping of NaNMC811 wassuccessfully implemented through Al2O3 coating on the cathode active material (CAM) precursor. The modified Al-NaNi0.8Mn0.1Co0.1O2 (Al-NaNMC811) exhibits excellent electrochemical dynamics and performance, maintaining a specific capacity above 100mAhg-1 after 100 cycles at 0.1 C (1.5-4.1 V) while providing a promising capacity retention of 63%. Additionally, the material demonstrates excellent rate capabilities, retaining a specific capacity of 107 mAh g-1 at 5 C. Compared to pristine NaNMC811, the modified Al-NaNMC811 is proven to have improved electrochemical kinetics with a higher Na+ diffusion coefficient due to dilated (003) interplanar spacing, and a more stable structure during the electrochemical charge-discharge processes, which is attributed to stronger Al-O bond energy. Understanding phase formations during the synthesis and comprehensive insight in the gradient doping for O3-type NaNMC811 CAMs guides further development of next-generation SIBsmaterials.

Cross-linking γ-Polyglutamic Acid as a Multifunctional Binder for High-Performance SiOx Anode in Lithium-Ion Batteries.

SiOx is a highly promising anode material for realizing high-capacity lithium-ion batteries owing to its high theoretical capacity. However, the large volume change during cycling limits its practical application. The development of a binder has been demonstrated as one of the most economical and efficient strategies for enhancing the SiOx anode's electrochemical performance. In this work, a multifunctional binder (T-PGA) is fabricated by cross-linking γ-polyglutamic acid (PGA) and tannic acid (TA) for SiOx anodes. The introduction of TA into PGA helps to buffer the volume changes of the SiOx anodes, facilitate diffusion of Li+, and construct stable SEI layers. Benefiting from this proposed binder, the SiOx anode maintains a reversible capacity of 973.0 mAh g-1 after 500 cycles at 500 mA g-1 and the full cell, pairing with LiNi0.5Co0.2Mn0.3O2 cathode, delivers a reversible capacity of 133 mA h g-1 (73.2% retention) after 100 cycles. This study offers valuable insights into advanced binders that are used in high-performance Li-ion batteries.

Modulating Interfacial Solvation via Ion Dipole Interactions for Low-Temperature and High-Voltage Lithium Batteries.

Extending the stability of ether solvents is pivotal for developing low-temperature and high-voltage lithium batteries. Herein, we elucidate the oxidation behavior of tetrahydrofuran with ternary BF4-, PF6- and difluoro(oxalato)borate anions and the evolution of interfacial solvation environment. Combined in-situ analyses and computations illustrate that the ion dipole interactions and the subsequent formation of ether-Li+-anion complexes in electrolyte rearrange the oxidation order of solvated species, which enhances the electrochemical stability of ether solvent. Furthermore, preferential absorption of anions on the surface of high-voltage cathode favors the formation of a solvent-deficient electric double layer and an anti-oxidation cathode electrolyte interphase, inhibiting the decomposition of tetrahydrofuran. Remarkably, the formulated electrolyte based on ternary anion and tetrahydrofuran solvent endows the LiNi0.8Co0.1Mn0.1O2 cathode with considerable rate capability of 5.0 C and high capacity retention of 93.12% after 200 cycles. At a charging voltage of 4.5 V, the Li||LiNi0.8Co0.1Mn0.1O2 cells deliver Coulombic efficiency above 99% at both 25 and -30 °C.

Modulating Interfacial Solvation via Ion Dipole Interactions for Low‐Temperature and High‐Voltage Lithium Batteries

Extending the stability of ether solvents is pivotal for developing low‐temperature and high‐voltage lithium batteries. Herein, we elucidate the oxidation behavior of tetrahydrofuran with ternary BF4‐, PF6‐ and difluoro(oxalato)borate anions and the evolution of interfacial solvation environment. Combined in‐situ analyses and computations illustrate that the ion dipole interactions and the subsequent formation of ether‐Li+‐anion complexes in electrolyte rearrange the oxidation order of solvated species, which enhances the electrochemical stability of ether solvent. Furthermore, preferential absorption of anions on the surface of high‐voltage cathode favors the formation of a solvent‐deficient electric double layer and an anti‐oxidation cathode electrolyte interphase, inhibiting the decomposition of tetrahydrofuran. Remarkably, the formulated electrolyte based on ternary anion and tetrahydrofuran solvent endows the LiNi0.8Co0.1Mn0.1O2 cathode with considerable rate capability of 5.0 C and high capacity retention of 93.12% after 200 cycles. At a charging voltage of 4.5 V, the Li||LiNi0.8Co0.1Mn0.1O2 cells deliver Coulombic efficiency above 99% at both 25 and ‐30 °C.

Enhancing the electrochemical characteristics of P2-Na0.7Mn0.6Cu0.3Cr0.1O2 cathode materials through morphological manipulation: assessment of rate capability and coulombic efficiency

Abstract Manganese-based layered oxides are regarded as an excellent cathode material for Na-ion batteries. These materials are susceptible to phase transitions, which result in structural instability and constrain their reversible capacity. Layered self-assembled microsphere-type cathodes Na0.7Mn0.6Cu0.3Cr0.1O2 were developed to modify the efficiency of sodium-ion batteries through a technique focused on controlling morphology. The incorporation of organic compounds such as benzoic acid employs molecular design techniques to modify intermolecular interactions and increase the spacing between layers. The self-assembled layered spherical architecture enhances the interface between the cathode and electrolyte, thereby markedly boosting the transport efficiency of sodium ions. Based on the cathode for batteries, it demonstrates a substantial initial capacity of 200.26 mAh g-1 at a current density of 26 mA g-1 within the voltage amount of 1.5-4.1 V, with a capacity retention of 82.69% after 100 cycles.

Suppressing high voltage chemo-mechanical degradation in single crystal nickel-rich cathodes for high-performance all-solid-state lithium batteries

Sulfide-based all-solid-state lithium batteries (SASSLBs) suffer from electrochemo.mechanical damage to Ni-rich oxide-based cathode active materials (CAMs), primarilycaused by severe volume changes, results in significant stress and strain cuase micro-cracks, and interfacial contact loss at potentials > 4.3 V(vs. Li/Li+). Quantifying micro-cracks and voids in cathode active materials (CAMs) can reveal the degradation mechanisms of Ni-rich oxide-based cathodes during electrochemical cycling. Nonetheless, the origin of electrochemical-mechanical damage remains unclear. Herein, We have developed a multifunctional PEG-based soft buffer layer (SBL) on the surface of carbon black (CB). This layer functions as a percolation network in the single crystal LiNi0.83Co0.07Mn0.1O2 and Li6PS5Cl composite cathode layer, ensuring superior ionic conductivity, reducing void formation and particle cracking, and promoting uniform utilization of the cathode active material in all-solid-state lithium batteries (ASSLBs). STEM-HAADF combined with nanoscale X-ray holo-tomography and plasma-focused ion beam scanning electron microscopy confirmed that the PEG-based SBL mitigated strain induced by reaction heterogeneity in the cathode. This strain produces lattice stretches, distortions, and the formation of curved transition metal oxide layers near the surface, contributing to structural degradation at elevated voltages. Consequently, ASSLBs with a LiNi0.83Co0.07Mn0.1O2 cathode containing LCCB-10 (CB/PEG mass ratio: 100/10) demonstrate a high areal capacity (2.53 mAh g–1/0.32 mA g–1) and remarkable rate capability (0.58 mAh g–1 at 1.4 mA g–1), with 88% capacity retention over 1000 cycles.

Lattice sulfuration enhanced sodium storage performance of Na0.9Li0.1Zn0.05Ni0.25Mn0.6O2 cathode

Lattice sulfuration enhanced sodium storage performance of Na0.9Li0.1Zn0.05Ni0.25Mn0.6O2 cathode

Achieving complete solid-solution reaction in layered cathodes with reversible oxygen redox for high-stable sodium-ion batteries

P2-type layered Mn-based oxides are promising cathode materials for sodium-ion batteries (SIBs), but it is still challenging to achieve both high capacity and stability because of complex phase transitions and irreversible oxygen release at high voltage. To address these challenges, an optimal P2-type Na0.67Mn0.8Cu0.15Ti0.05O2 (NMCT) cathode with a complete solid-solution reaction and reversible oxygen redox reaction over a wide voltage range was developed. The introduction of the Na–O–Ti configuration leads to fewer delocalized electrons on oxygen and thus enhances oxygen redox activity, while the high energetic overlap between O 2p and Cu 3d states and the increased Mn–O hybridization strengthen the rigidity of oxygen framework to achieve reversible and stable oxygen redox reaction. In addition, the reinforced TM–O interaction, combined with the ameliorated Mn3+ Jahn-Teller distortion and disrupted Na+/vacancy ordering, synergistically eliminate the undesired P2–OP4 phase transition and lead to a complete solid-solution reaction, which greatly facilitates Na+ transport kinetics and stabilizes structural integrity. As a consequence, improved rate performance and cycling stability are achieved for NMCT. Our present study provides a promising avenue for simultaneously utilizing the reversible oxygen redox activity and maintaining the structural integrity to accomplish the capacity-stability trade-off of Mn-based oxide cathodes for constructing practical SIBs.

Breaking boundaries in O3-type NaNi1/3Fe1/3Mn1/3O2 cathode materials for sodium-ion batteries: An industrially scalable reheating strategy for superior electrochemical performance

To address the challenges of air stability and slurry processability in layered transition metal oxide O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM) for sodium-ion batteries (SIBs), we have designed an innovative 500 °C reheating strategy. This method improves the surface properties of NFM without the need for additional coating layers, making it more efficient and suitable for large-scale applications. Pristine NFM (NFM-P) was first synthesized through a high-temperature solid-state method and then modified using this reheating approach (NFM-HT). This strategy significantly enhances air stability and electrochemical performance, yielding an initial discharge specific capacity of 151.46 mAh/g at 0.1 C, with a remarkable capacity retention of 95.04% after 100 cycles at 0.5 C. Additionally, a 1.7 Ah NFM||HC (hard carbon) pouch cell demonstrates excellent long-term cycling stability (94.64% retention after 500 cycles at 1 C), superior rate capability (86.48% retention at 9 C), and strong low-temperature performance (77% retention at −25 °C, continuing power supply at −40 °C). Notably, even when overcharged to 8.29 V, the pouch cell remained safe without combustion or explosion. This reheating strategy, which eliminates the need for a coating layer, offers a simpler, more scalable solution for industrial production while maintaining outstanding electrochemical performance. These results pave the way for broader commercial adoption of NFM materials.

Elucidating the Nature of Secondary Phases in LiNi0.5Mn1.5O4 Cathode Materials using Correlative Raman-SEM Microscopy

Elucidating the Nature of Secondary Phases in LiNi0.5Mn1.5O4 Cathode Materials using Correlative Raman-SEM Microscopy

Synthesis of nano cubic microstructure LiNi0.8Co0.1Mn0.1O2 cathode materials via rapid precipitation assisted with hydrothermal treatment

In this work, a modified Ni-rich cathode material LiNi0.8Co0.1Mn0.1O2 with a unique nano cubic microstructure is successfully synthesized via a rapid precipitation assisted with hydrothermal treatment. The formation of this distinctive microstructure is attributed to the homogeneous rapid precipitation in microreactor, which predominantly generates uniform crystal nuclei. The as-prepared material with nano-/microstructure shows superior initial reversible capacity (205.3 mAh·g−1 at 2.7–4.3 V) and rate capability (163.9 mAh·g−1 at 5 C). Additionally, it maintains a high capacity (188.2 mAh·g−1) with a retention of 87.2 % at 1 C after 200 cycles, demonstrating outstanding cycling stability. Our work presents a straightforward and efficient approach for producing nano-cubic microstructure layered cathode materials.

Improvement of electrochemical performance by surface modification of LiNi0.65Co0.15Mn0.2O2 cathode materials with SnO2

LiNi0.65Co0.15Mn0.2O2 batteries have attracted more and more attention due to their high energy density. However, LiNi0.65Co0.15Mn0.2O2 possesses adverse factors such as severe Li-Ni mixing and side reactions between active substance and electrolyte, which limits its electrochemical performance. Hence, we employed the SnO2 surface coating method to enhance its performance. SnO2 coating inhibits the direct contact between LiNi0.65Co0.15Mn0.2O2 and the electrolyte, which reduces the lithium-nickel mixing, enlarges the lithium layer spacing, and contributes to the improvement of the specific capacity of discharge and the cycling performance. The electrochemical results indicate the optimal SnO2-coated LiNi0.65Co0.15Mn0.2O2 show excellent cycling performance (85.0 % capacity retention for 100 cycles at 0.1 C) and multiplicative performance (124.1 mA·h·g−1 discharge specific capacity at 2 C). The paper highlights the SnO2 cladding technology which provides an excellent research idea to improve lithium-ion batteries.

Elucidating the effect of annealing temperature on the atomic-level surface structure evolution and electrochemical performance of Mo doped LiMn2O4 cathode materials

Critical barriers to the extensive applications of the spinel LiMn2O4 cathodes include grievous capacity degradation and structural collapse. Bulk elemental doping combining surface modification, which is a common approach to address these challenges. Here, synchronous bulk Mo-doped and in-situ surface reconstructed layer coated LiMo0.02Mn1.98O4 cathodes are prepared by tuning the annealing temperatures. Using the spherical aberration-corrected scanning transmission microscopy (Cs-STEM) technique, we demonstrate that part of Mo6+ ions dopes into the octahedral Mn 16d sites to form LiMo0.02Mn1.98O4 that strengthens bulk structural stability. The other part of Mo6+ ions or the Mn atom occupying the Mn 16c sites of the spinel to form a surface reconstructed layer on the outermost surface that suppresses the side reaction and slows down the decomposition of the electrolyte. Specifically, the LiMo0.02Mn1.98O4 cathode calcined at 750 °C with an appropriate surface reconstructed layer exhibits an outstanding capacity retention of 76.28 % after 1000 cycles at 10C at 25 °C. Our work provides a simple and novel way toward high electrochemical performance tuning for spinel LiMn2O4 cathodes.

A Quasi-Solid-State Polymer Lithium-Metal Battery with Minimal Excess Lithium, Ultrathin Separator, and High-Mass Loading NMC811 Cathode.

Solid-state batteries with lithium metal anodes are considered the next major technology leap with respect to today's lithium-ion batteries, as they promise a significant increase in energy density. Expectations for solid-state batteries from the automotive and aviation sectors are high, but their implementation in industrial production remains challenging. Here, we report a solid-state lithium-metal battery enabled by a polymer electrolyte consisting of a poly(DMADAFSI) cationic polymer and LiFSI in Pyr13FSI as plasticizer. The polymer electrolyte is infiltrated and solidified in the pores of a commercial LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode with up to 2.8 mAh cm-2 nominal areal capacity and in the pores of a 25 μm thin commercial polypropylene separator. Cathode and separator are finally laminated into a cell in combination with a commercial 20 μm thin lithium metal anode. Our demonstration of a solid-state polymer battery cycling at full nominal capacity employing exclusively commercially available components available at industrial scale represents a critical step forward toward the commercialization of a competitive all-solid-state battery technology.