High-energy Cathode Materials Research Articles

Interlayer expanded magnesium vanadium bronze for high capacity stable aqueous zinc batteries and method for proton contribution calculation

Magnesium vanadium bronze, MgV6O16·6H2O, is demonstrated as a cathode material for aqueous zinc batteries. Its remarkable electrochemical performance is attributed to the hydrated magnesium pillar layer, which enhances zinc ion diffusion into the structure, yielding a high initial discharge capacity of 298 mAh g−1 and capacity retention above 97 % after 300 cycles. Zinc ions and protons are co-intercalated into the MgV6O16·6H2O structure, while zinc hydroxide sulfate forms on the surface during the discharge process. Ex-situ X-ray diffraction results and elemental analyses confirm the zinc and proton co-intercalation reaction within the MgV6O16·6H2O structure during cycling, providing detailed insights into the electrochemical mechanisms. These findings demonstrate the potential of MgV6O16·6H2O as a high-energy cathode material for aqueous zinc batteries and offer a comprehensive understanding of the zinc ion and proton co-intercalation mechanism in the MgV6O16·6H2O structure.

Optimizing the crystal structure and electrochemical properties of Na4MnCr(PO4)3 by trace La doping

Na4MnCr(PO4)3, a manganese-based NASICON-type phosphate cathode material, is attracted considerable attention due to its high voltage and energy density. However, its practical application is hindered by poor electronic conductivity and inferior sodium ion diffusion kinetics. In this study, trace La3+ is utilized to optimize the lattice structure of Na4MnCr(PO4)3 due to its unique energy level structure. La3+ doping significantly enhances the local environment of the Mn-O bond and stabilizes the lattice structure by improving covalency, thereby mitigating Mn dissolution during charge–discharge cycles. Additionally, the large ionic radius of La3+ promotes the sodium ion transport kinetics by expanding the cell volume and facilitating rapid sodium storage. As a result, the optimal Na4MnCr0.995La0.005(PO4)3/C sample demonstrates an impressive initial discharge specific capacity of 124.5 mAh g−1 at 0.1C and superior cycling stability with a capacity retention of 70.2 % after 500 cycles at 5C. Furthermore, density functional theory calculations indicate that La3+ doping can enhance conductivity and reduce the energy barrier for sodium ion diffusion. This study presents an effective and cost-efficient doping strategy for modifying high-energy density NASICON-type phosphate cathode materials, showing promising potential in the field of sodium ion batteries.

A Comprehensive Review of Functional Gel Polymer Electrolytes and Applications in Lithium-Ion Battery.

The rapid expansion of flexible and wearable electronics has necessitated a focus on ensuring their safety and operational reliability. Gel polymer electrolytes (GPEs) have become preferred alternatives to traditional liquid electrolytes, offering enhanced safety features and adaptability to the design requirements of flexible lithium-ion batteries. This review provides a comprehensive and critical overview of recent advancements in GPE technology, highlighting significant improvements in its physicochemical properties, which contribute to superior long-term cycling stability and high-rate capacity compared with traditional organic liquid electrolytes. Special attention is given to the development of smart GPEs endowed with advanced functionalities such as self-protection, thermotolerance, and self-healing properties, which further enhance battery safety and reliability. This review also critically examines the application of GPEs in high-energy cathode materials, including lithium nickel cobalt manganese (NCM), lithium nickel cobalt aluminum (NCA), and thermally stable lithium iron phosphate (LiFePO4). Despite the advancements, several challenges in GPE development remain unresolved, such as improving ionic conductivity at low temperatures and ensuring mechanical integrity and interfacial compatibility. This review concludes by outlining future research directions and the remaining technical hurdles, providing valuable insights to guide ongoing and future efforts in the field of GPEs for lithium-ion batteries, with a particular emphasis on applications in high-energy and thermally stable cathodes.

Reviewing Li-Rich Disordered Rocksalts as Next-Generation High-Energy Cathode Material

Reviewing Li-Rich Disordered Rocksalts as Next-Generation High-Energy Cathode Material

Scalable Synthesis of Single Crystal Ni-Rich Cathodes for Advanced Lithium-Ion Batteries

Long-range electrical vehicles require high energy density lithium-ion batteries that utilize stable, high-energy cathode materials. Among various cathodes, Ni-rich NMC cathodes with a layered structure, knows for their high capacity, high voltage, and cost-effectiveness, stand out as one of the most promising cathodes. Traditional polycrystalline Ni-rich NMC encounter issues such as pulverization, gas generation and moisture sensitivity, limiting their widespread use in EV batteries on large scale. The single crystal format of Ni-rich cathode can effectively eliminate and mitigate these issues. However, synthesizing of high-performance single crystal Ni rich NMC, especially when Ni ≥0.8, presents a significant challenge.We’ve explored an innovative phase separation approach for direct synthesis of high-performance single crystal NMC811. The comprehensive investigation into the reaction mechanism of single crystal growth was conducted to understand the relationship between synthesis, morphology, and performance in growing single crystal NMC811. The enhanced performance of these materials was realized through the precise morphological and structural control of precursors and has been confirmed in practical 2Ah pouch cells. The developed approach is readily adaptable to current industry manufacturing processes and provides valuable new insights that can be broadly applied to cost-efficient large-scale synthesis of single crystals and various advanced battery materials technologies.

Lithium Orbital Hybridization Chemistry to Stimulate Oxygen Redox with Reversible Phase Evolution in Sodium-Layered Oxide Cathodes.

Searching for high energy-density electrode materials for sodium ion batteries has revealed Na-deficient intercalation compounds with lattice oxygen redox as promising high-capacity cathodes. However, anionic redox reactions commonly encountered poor electrochemical reversibility and unfavorable structural transformations during dynamic (de)sodiation processes. To address this issue, we employed lithium orbital hybridization chemistry to create Na-O-Li configuration in a prototype P2-layered Na43/60Li1/20Mg7/60Cu1/6Mn2/3O2 (P2-NaLMCM') cathode material. That Li+ ions, having low electronegativity, reside in the transition metal slabs serves to stimulate unhybridized O 2p orbitals to facilitate the stable capacity contribution of oxygen redox at high state of charge. The prismatic-type structure evolving to an intergrowth structure of the Z phase at high charging state could be simultaneously alleviated by reducing the electrostatic repulsion of O-O layers. As a consequence, P2-NaLMCM' delivers a high specific capacity of 183.8 mAh g-1 at 0.05 C and good cycling stability with a capacity retention of 80.2% over 200 cycles within the voltage range of 2.0-4.5 V. Our findings provide new insights into both tailoring oxygen redox chemistry and stabilizing dynamic structural evolution for high-energy battery cathode materials.

Spheroidization: The Impact of Precursor Morphology on Solid-State Lithiation Process for High-Quality Ultrahigh-Nickel Oxide Cathodes.

Layered oxides with ultrahigh nickel content are considered promising high energy cathode materials. However, their cycle stability is constrained by a series of heterogeneous structural transformations during the complex solid-state lithiation process. By in-depth investigation into the solid-state lithiation process of LiNi0.92Co0.04Mn0.04O2, it is found that the protruded parts on the surface of precursor particles tend to be surrounded by locally excessive LiOH, which promotes the formation of a rigid and dense shell during the early stage of lithiation process. The shell will hinder the diffusion of lithium and topotactic lithiation within the particles, culminating in spatially heterogeneous intermediates that can impair the electrochemical properties of the cathode material. The spheroidization of the precursor can enhance uniformity in structural evolution during solid-phase lithiation. Ultrahigh nickel cathodes derived from spherical precursors demonstrate high initial discharge specific capacity (234.2 mAh g-1, in the range of 2.7-4.3 V) and capacity retention (89.3 % after 200 cycles), significantly superior to the non-spherical samples. This study not only sheds light on the intricate relationship between precursor shape and structural transformation but also introduces a novel strategy for enhancing cathode performance through precursor spheroidization.

Long-Cycle Lithium Batteries with LiNi0.8Co0.1Mn0.1O2 Cathodes above 4.5V Enabled by Uniform Coating of Nanosized Garnet Electrolytes

Abstract The pursuit of high-energy cathode materials has been focused on raising the charging cutoff voltage of nickel (Ni)-rich layered oxide cathode such as LiNi0.8Co0.1Mn0.1O2 (NCM811). However, the NCM811 suffers from rapid capacity fading upon cycling at cutoff voltage higher than 4.5 V, owing to their structural degradation and labile surface reactivity. Surface-coating with solid electrolytes has been recognized as an effective method to mitigate the performance failure of NCM811 at high voltage. Herein, the nano-sized Li6.4La3Ta0.6Zr1.4O12 (LLZTO) is uniformly coated on the surface of single-crystal NCM811 particles, accompanied with the long-range Ta5+ diffusion into the transition metal layer of NCM811 lattice. It is revealed that the LLZTO coating can not only inhibit the surface reactions of NCM811 with liquid electrolytes but also play an important role in suppressing the bulk microcracking within the NCM811 particles. The incorporation of Ta5+ ion expands the lattice spacing and thereby improves the homogeneity of the Li+ diffusion in the single-crystal NCM811, which alleviates the mechanical strain and intragranular cracks caused by nonuniform phases-transformation at high charging voltage. The synergy of surface protection and structural stabilization realized by LLZTO coating enables the NCM811-based lithium batteries to achieve a remarkable electrochemical performance. Typically, LLZTO coated NCM811 delivers a high reversible specific capacity of 202.1 mAh⋅g−1 with an excellent capacity retention as high as 70% over 1000 cycles upon charging to 4.5 V at 1 C.

High-Energy Earth-Abundant Cathodes with Enhanced Cationic/Anionic Redox for Sustainable and Long-Lasting Na-Ion Batteries.

Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na0.67Fe0.3Mn0.5Mg0.1Ti0.1O2 cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210mAhg-1 at 20mAg-1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200mAg-1, even when operated with a high charge cut-off voltage of 4.5V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.

Boosting the Electrochemical Performance of Primary and Secondary Lithium Batteries with Mn-Doped All-Fluoride Cathodes.

Transition metal fluorides are potentially high specific energy cathode materials of next-generation lithium batteries, and strategies to address their low conductivity typically involve a large amount of carbon coating, which reduces the specific energy of the electrode. In this study, MnyFe1-yF3@CFx was generated by the all-fluoride strategy, converting most of the carbon in MnyFe1-yF3@C into electrochemical active CFx through a controllable NF3 gas phase fluorination method, while still retaining a tightly bound graphite layer to provide initial conductivity, which greatly improved the energy density of the composite. This synergistic effect of nonfluorinated residual carbon (∼11%) and Mn doping ensures the electrochemical kinetics of the composite. The loading mass of the active substance had been increased to 86%. The theoretical and actual discharge capacity of MnyFe1-yF3@CFx composite was up to 765 mAh g-1 (pure FeF3 is 712 mAh g-1) and 728 mAh g-1, respectively. The discharge capacity at the high-voltage (3.0 V) platform was more than three times higher than that of the non-Mn-doped composite (FeF3@CFx).

Regulating anionic redox reversibility in Li-rich layered cathodes via diffusion-induced entropy-assisted surface engineering

Cobalt-free lithium- and manganese-rich layered oxides (LMROs) are regarded as effective cathode materials for lithium storage due to their high capacity and cost-effectiveness. However, challenges with structural degradation, resulting in poor cyclability and rate performance, have hindered their widespread use. Essentially, rapid structural degradation arises from irreversible and complex redox reactions, triggering oxygen release, transition metal migration, and electrolyte decomposition. To tackle this issue, we propose an epitaxial entropy-assisted construction approach to develop a sturdy surface with adaptable composition, stabilising the surface crystal structure and preventing undesirable interface reactions. This distinct reconstructed surface comprises diverse heterogeneous elements and composite microstructures. The heteroatom-doped layer, with multi-doping sites like Li, O site, and tetrahedral positions, effectively manages the chemical environment and electronic structure of surface lattice oxygen. This epitaxial entropy stabilisation approach, stemming from multi-element synergy, effectively controls redox progress to limit oxygen release and curb transition metal migration, reducing structural decay. Additionally, the composite coated layer, containing oxygen defects and heterogeneous spinel phases, can hinder electrolyte corrosion and promote Li+ transport. Using these epitaxial entropy surface modifications, the LMRO cathode demonstrates regulated anionic redox reversibility and enhanced cycling stability across diverse operational conditions. This epitaxial entropy-assisted surface engineering offers a promising avenue for stabilising high-energy cathode materials.

Exploring the impact of synergistic dual-additive electrolytes on 5 V-class LiNi0·5Mn1·5O4 cathodes

Tris (trimethylsilyl) phosphate (TMSP) and tris(2,2,2-trifluoroethyl) phosphate (TTFP) was added to carbonate solvent-based electrolytes as dual-additives to enhance the performance of LiNi0·5Mn1·5O4 (LNMO). The X-ray photoelectron spectroscopy results revealed that both TMSP with high oxidation ability and TTFP with high oxidation resistance participated in the formation of cathode–electrolyte interphase (CEI) films. Electrochemical impedance spectroscopy confirmed that the constructed CEI films had excellent electronic insulation and ionic conductivity, reducing the interfacial impedance of the LNMO electrode, and improving the electrochemical performance of LNMO/Li half-cells and LNMO/Li4Ti5O12 full-cells. As measured by the nuclear magnetic resonance, the incorporation of TMSP and TTFP significantly reduced the HF content in the electrolytes. Therefore, both LNMO/Li half-cells (500 cycles with 95.7% capacity retention) and LNMO/Li4Ti5O12 full-cells (200 cycles with 79.9% capacity retention) displayed higher cycling stabilities at 5 C owing to the synergistic effect of TMSP and TTFP. In comparison, capacity retentions of ∼76.5% after 500 cycles and ∼37.2% after 200 cycles were respectively achieved for the LNMO/Li half-cells and LNMO/Li4Ti5O12 full-cells with the standard electrolyte at 5 C. This study provides strong evidence that additive combinations can improve the electrochemical performance of high-energy and high-voltage cathode materials.

Boosting Zn2+ intercalation in manganese oxides for aqueous zinc ion batteries via delocalizing the d-electrons spin states of Mn site

Rechargeable aqueous zinc-ion batteries (AZIBs) have received increasing attention on account of their eco-friendliness and low cost. However, the limited capacity and poor rate properties of cathodes remain a major challenge due to the low electrochemical reactivity of cathode materials and sluggish Zn2+ transport kinetics. Herein, we design a 1,5-naphthalenediamine (NAPD) pre-intercalate potassium manganese dioxide (KMO-NAPD) with high capacity and rate capability for AZIBs. The introduction of NAPD can delocalize the d-electrons spin states of the Mn site and activate the reactivity of KMO-NAPD for Zn2+ intercalation. Moreover, the interaction between intercalated Zn2+ and KMO-NAPD is weakened due to the decreased electrostatic interaction force, which promotes the diffusion of Zn2+. Consequently, the KMO-NAPD cathode exhibits high specific capacity (237 mAh g−1 at 1 A g−1) satisfying rate capability (129 mAh g−1 at 4 A g−1), and excellent cycling stability (85 % capacity retention after 1000 cycles). Furthermore, the fabricated AZIBs based on the KMO-NAPD exhibit a high energy density of 294.3 Wh kg−1 and a peak power density of 8.6 kW kg−1. This study opens up a new path for the development of high-energy organic-inorganic hybrid cathode materials with modulated electronic structures for advanced AZIBs.

Triggering cationic/anionic hybrid redox stabilizes high-temperature Li-rich cathodes materials via three-in-one strategy

Efficiently advancing lithium-ion batteries toward high energy density entails overcoming challenges in Li-rich layered oxides, including severe voltage and capacity fading, irreversible oxygen escape and compromised thermal robustness due to the uncontrollable oxygen anionic redox (OAR). Herein, a three-in-one modification strategy, aim at strengthening the reversibility of OAR and structural integrity of MnO6 octahedron, is rationally introduced on Li1.2Mn0.53Ni0.20Co0.07O2 cathode through a universal H3BO3-treatment. Through the introduction of oxygen vacancies and gradient B-doping, the energy level of unhybridized O 2p states is decreased to narrow the band energy gap with transition metal (TM) band, which triggers cationic/anionic hybrid redox at high voltage, thereby stabilizing the peroxo-like (O2)n- species and hindering irreversible oxygen escape, while the lithium borate nano-coating serves to mitigate side reactions, particularly during charging at elevated temperatures. As a result, the modulated cathode exhibits notable capacity retention of 96.3 % after 500 cycles at 1 C with limited voltage fading rate (1.73 mV per cycle) and even stable cyclic performance at high temperature (60 °C). This approach provides an effective and straightforward method to tackle the voltage decay and capacity fading of high-energy Li-rich layered cathode materials.

Enhancing the Stability of 4.6 V LiCoO2 Cathode Material via Gradient Doping.

LiCoO2 (LCO) can deliver ultrahigh discharge capacities as a cathode material for Li-ion batteries when the charging voltage reaches 4.6 V. However, establishing a stable LCO cathode at a high cut-off voltage is a challenge in terms of bulk and surface structural transformation. O2 release, irreversible structural transformation, and interfacial side reactions cause LCO to experience severe capacity degradation and safety problems. To solve these issues, a strategy of gradient Ta doping is proposed to stabilize LCO against structural degradation. Additionally, Ta1-LCO that was tuned with 1.0 mol% Ta doping demonstrated outstanding cycling stability and rate performance. This effect was explained by the strong Ta-O bonds maintaining the lattice oxygen and the increased interlayer spacing enhancing Li+ conductivity. This work offers a practical method for high-energy Li-ion battery cathode material stabilization through the gradient doping of high-valence elements.

Prolonging the Cycle Stability of Anion Redox P3-Type Na0.6Li0.2Mn0.8O2 through Al2O3 Atomic Layer Deposition Surface Modification.

Sodium-ion batteries (SIBs) are becoming an alternative option for large-scale energy storage systems owing to their low cost and abundance. The lattice oxygen redox (LOR), which has the potential to increase the reversible capacity of materials, has promoted the development of high-energy cathode materials in SIBs. However, the utilization of oxygen anion redox reactions usually results in harmful lattice oxygen release, which hastens structural deformation and declines electrochemical performance, severely hindering their practical application. Herein, a ribbon-ordered superstructured P3-type Na0.6Li0.2Mn0.8O2 (NLMO) cathode with a uniform Al2O3 coating through atomic layer deposition (ALD) was synthesized. The cycling stability and rate capability of the materials were improved by a proper thickness of the Al2O3 layer. Differential electrochemical mass spectrometry (DEMS) results clearly suggest that the Al2O3 coating can inhibit the CO2 release caused by the highly active surface of the NLMO material. Moreover, the results of transmission electron microscopy (TEM) and etching X-ray photoelectron spectroscopy (XPS) show that the Al2O3 coating can effectively prevent electrolyte and electrode side reactions and the dissolution of Mn. This surface engineering strategy sheds light on the way to prolong the cycling stability of anionic redox cathode materials.

Exploring the unexpected electrochemical dynamics of lithium vanadyl phosphate electrodes in zinc battery systems

Our study explores the potential of β-LiVOPO4 as a high-energy and stable cathode material for zinc-ion batteries, achieving a high working voltage through comprehensive characterization techniques.

Insights into the First Multi Transition Element Containing Ruddlesden Popper-Type Cathode for Fluoride Ion Batteries

Fluoride ion batteries (FIBs) have emerged as a recent solid-state battery technology, offering an alternative to traditional battery systems. However, the existing FIBs have encountered challenges related to their poor cycling performance and improved electrodes based on fluoride insertion chemistry are highly sought.Here, we investigate Ruddlesden-Popper type La2Ni0.75Co0.25O4+𝛿 as a promising intercalation-based active cathode material for all-solid-state FIBs. We determine the structural changes of La2Ni0.75Co0.25O4+𝛿 during Fluoride intercalation / de-intercalation by X-ray Diffraction (XRD), electrochemical measurements and X-ray absorption spectroscopy to understand the detailed complex reaction behaviour of the phase, focussing on understanding the changes of Ni, Co oxidation states and coordination environments. Under optimized operating conditions, we obtained a cycle life of 120 cycles at a critical cut-off capacity of 40 mAh/g and over 250 cycles under pressure of 452MPa. The average Coulombic efficiencies ranged from 95% to 99% for the cell running under pressure. Thus, La2Ni0.75Co0.25O4+𝛿 corresponds to the most promising cycling-stable high-energy cathode materials for all-solid-state FIBs with the improved capacity.

Locally Concentrated Ionic Liquid Electrolytes for Lithium/Sulfurized Polyacrylonitrile Batteries

Low-cost sulfurized polyacrylontrile (SPAN), which shows negligible polysulfide dissolution and stable cycling up to hundreds of cycles due to a solid-phase mechanism in carbonate-based electrolytes, is a valuable high-energy cathode material for long-lifespan lithium metal batteries (LMBs).1 -3 However, the conventional carbonate-based electrolytes for commercial lithium-ion batteries are incompatible with lithium metal anodes (LMAs).4 The unstable solid-electrolyte interphases (SEIs) result in lithium dendrite growth and low lithium stripping/plating CEs, which further cause safety concerns and limited lifespan of Li/SPAN cells with low negative to positive areal capacity (N/P) ratio. Therefore, the development of Li/sulfurized polyacrylonitrile (SPAN) batteries requires electrolytes that can form stable electrolyte/electrode interphases (EEIs) simultaneously on lithium metal anodes (LMAs) and SPAN cathodes. With the remarkable compatibility toward LMAs and low flammability,4–7 locally concentrated ionic liquid electrolytes (LCILEs) might be promising candidates for Li/SPAN cells.Herein, a low-flammability locally concentrated ionic liquid electrolyte (LCILE) employing monofluorobenzene (mFBn) as the diluent is proposed for Li/SPAN cells.8 Unlike non-solvating diluents in other LCILEs, mFBn partially solvates Li+, decreasing the coordination between Li+ and bis(fluorosulfonyl)imide (FSI-). In turn, this triggers a more substantial decomposition of FSI- and consequently results in the formation of a SEI rich in inorganic compounds, which enables a remarkable Coulombic efficiency (99.72%) of LMAs. Meanwhile, a protective cathode/electrolyte interphase (CEI), derived mainly from FSI- and organic cations, is generated on the SPAN cathodes, preventing the dissolution of polysulfides. Benefiting from the robust interphases simultaneously formed on both the electrodes, highly stable cycling of Li/SPAN cells for 250 cycles with a capacity retention of 71% is achieved employing the LCILE and only 80% lithium metal excess.

Enabling High-Capacity Electrochemical Magnesium Intercalation in Prussian Blue Cathode Via Synthesis Route Optimization

Magnesium-ion batteries (MIBs) have emerged as a promising candidate for post-lithium-ion batteries. However, their widespread adoption is hindered by the limited number of host materials that can intercalate magnesium ions reversibly in a nonaqueous electrolyte with a high operating voltage, such as Prussian Blue analogues. Unfortunately, the capacity of Prussian Blue is by far limited (<100 mAh g−1), resulting in low energy density, despite their high operating voltage. In this study, we present a systematic synthesis route optimization that allows for high-capacity magnesium ion insertion into Prussian Blue. Our defect-free and water-free Prussian Blue demonstrates reversible magnesium intercalation with a first discharge capacity of 127 mAh g−1 at 25 °C and 156 mAh g−1 at 60 °C, with an average discharge voltage of ~2.1 V (vs. Mg/Mg2+) in a nonaqueous, chloride-free electrolyte. The high-capacity magnesium ion insertion into our optimized Prussian Blue offers insights into the importance of material preparation for high-energy cathode materials in MIBs.