O2 Cathode Research Articles

Uncovering the Crucial Role of Chelating Structures in Cyano-Alkyl-Phosphate Electrolytes for High-Voltage Lithium Metal Batteries.

The inferior oxidative stability of commercial carbonate electrolytes and overgrowth of the electrode-electrolyte interphase (EEI) have largely hindered the development of high-voltage lithium metal batteries. In this study, these challenges are addressed by designing Li+-solvent chelating solvation structures to inhibit solvent decomposition using cyano-alkyl-phosphate as a demonstration. Theoretical and experimental studies confirm that the -P═O and -C≡N groups within diethyl (2-cyanethyl) phosphonate exhibit a comparable ability to coordinate with Li+, facilitating the formation of seven-membered chelating structures. This unique solvation structure contributes to the formation of anion-derived inorganic-rich EEI with high stability and robustness, hindering the further decomposition of the electrolyte. Additionally, the cyano group has a strong complexation with the transition metal (TM) in the cathode to inhibit TM dissolution, thereby ensuring the structural stability of the cathode particle. Utilizing this special chelating structure, the designed electrolyte demonstrates favorable Li plating/stripping reversibility and promising oxidative stability in high-voltage batteries. Consequently, the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode exhibits a high capacity retention (90%) after operating 300 cycles. Under harsh testing conditions, the 4.6 V Li||NCM811 pouch cell with a capacity of 1.4 Ah (∼295 Wh kg-1 based on the total mass of the cell) retains 70% capacity after 80 cycles. This work provides new insights into the correlation between the solvation structure and oxidative stability of electrolytes, contributing significantly to the advancement of high-voltage lithium metal batteries.

Boosting the Structural Reversibility of Layered Oxide Cathode for Realizing Long-Term Cycle Life Through Electronic Structure Regulation.

O3-type layered oxide cathode exhibits great application potential for practical sodium-ion batteries, due to its cost-effectiveness, abundant sodium and manganese resources, and high theoretical capacity. However, the irreversible phase transition, coupled with rapid capacity decay, which is primarily attributed to the Jahn-Teller effect of Mn3+, remains a significant bottleneck for commercial application. Additionally, the sluggish kinetics during the (de)sodiation process require urgent improvement. Herein, an electronic structure regulation strategy is proposed by low-valence Li/Cu co-substitution to address these issues. The roles of Li/Cu on the electronic structure, structural evolution, and electrochemical properties in the Na0.96Ni0.22Fe0.2Mn0.5Li0.04Cu0.04O2 (NFMLC) cathode are comprehensively explored through systematic in situ/ex situ characterization techniques and theoretical calculations. The results reveal that this strategy effectively activates more Ni2+/3+ and Fe3+/4+ redox reactions above 2.5V, while suppressing Mn3+/4+ redox activity below 2.5V, thereby achieving highly structural reversibility. Therefore, the NFMLC electrode displays excellent long-term cycling stability (81.5% capacity retention after 2000 cycles at 5 C), and significantly enhanced rate performance (from 45.5% to 80.4% under a ratio of 5 C to 0.5 C). This work provides a valuable perspective on the design of low-cost, long-life, and high-performance layered oxide cathodes for practical sodium-ion batteries.

Designing Isocyanate‐Containing Elastomeric Electrolytes for Antioxidative Interphases in 4.7 V Solid‐State Lithium Metal Batteries

AbstractTo facilitate the use of solid polymer electrolytes (SPEs) with high‐nickel (Ni) cathodes in high‐voltage lithium (Li) metal batteries (LMBs), it is crucial to address the challenges of low oxidative stability and the formation of vulnerable interphases. In this study, isocyanate groups (−N═C═O) are incorporated to develop an SPE with a bi‐continuous structure, consisting of elastomeric and plastic crystal phases. This rationally designed SPE exhibits high ionic conductivity (0.9 × 10−3 S cm−1 at 25 °C), excellent elasticity (elongation at break of 330%), and enhanced oxidative stability (over 4.8 V vs. Li/Li⁺). A full cell, incorporating this SPE with a thin Li foil of 40 µm, and a high‐Ni LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode operating at 4.7 V vs. Li/Li⁺, demonstrates excellent cyclability, retaining 70% of its initial capacity after 200 cycles under a high C‐rate of 1C at 25 °C. The extended cycling of isocyanate‐containing SPE at 4.7 V vs. Li/Li⁺ is attributed to robust and compact inorganic‐rich interphases enabled by antioxidative −N−C═O components, as well as uniform Li deposition attributed to the bi‐continuous structured SPE. This study suggests that the isocyanate‐containing SPE system is a promising candidate for high‐voltage solid‐state LMBs by constructing stable interphases.

Application of precursor with ultra-small particle size and uniform particle distribution for ultra-high nickel single-crystal cathode materials by coprecipitation method

Ultra-high nickel single-crystal cathode materials have become the most promising for lithium-ion batteries. However, the preparation of ultra-high nickel single-crystal precursors by a continuous coprecipitation method has the disadvantages of large particle size, wide distribution, poor morphology. The extent of the inhomogeneous reactions can be more severe in single-crystal cathodes with larger particle size. Herein, the coprecipitation method with a solid concentrator was adopted, and citrate sodium was used as a complexing agent to improve the physical properties of precursors and electrochemical performance of single-crystal cathode materials. By analyzing the morphology and agglomeration mechanism of the precursor nucleuses under different pH values, it was found that hexagonal nanosheets grew along the 101 direction, and the primary particles showed thicker at pH of 11.4. The hexagonal nanosheets grew along the 001 direction, and the primary particles showed finer at pH of 12.2. The morphology and particle size uniformity of the secondary particles formed by agglomeration at these two pH values showed poor. However, hexagonal nanosheets grew synergistically along the 001 and 101 directions at pH of 11.8, so the primary particles with uniform particle size gradually agglomerated, and then the secondary particles with ultra-small particle size and uniform distribution obtained. Compared to materials prepared by the traditional continuous coprecipitation method, the precursor displays a smaller particle size(D50 = 1.8 µm), higher sphericity, uniformity and denser internal structure. In order to evaluate the performance of Ni0.94Co0.04Mn0.02(OH)2 with ultra-small particle size, the sintering conditions of LiNi0.94Co0.04Mn0.02O2 need to be explored. It was found that the LiNi0.94Co0.04Mn0.02O2 cathode material prepared at 790 °C exhibited higher discharge capacity, cycle and rate performance, compared to materials prepared at 760 °C and 820 °C. We further utilized TEM, EPMA, and XPS to test the internal structure and valence state of LiNi0.94Co0.04Mn0.02O2 cathode material. The results show that the LiNi0.94Co0.04Mn0.02O2 calcined at 790 °C has a good single crystal structure. The LiNi0.94Co0.04Mn0.02O2 cathode materials inherited the structure and particle size of Ni0.94Co0.04Mn0.02(OH)2 precursors, and displayed discharge capacity of 194.7 mAh/g and capacity retention rate of 89.8 % after 100 cycles at 1 C. The microstructure and phase transition of the as-prepared cathode material are well-maintained after long-term cycling, without obvious inter-crystalline micro-crack. The results indicate that its electrochemical performance is better than that of cathode materials with precursors prepared by a continuous coprecipitation method. This work provides new insights for the preparation of small-particle-size precursor and single-crystal cathode materials.

Enhanced Cycling Stability and Rate Capability of Al2O3-Coated NaNi1/3Fe1/3Mn1/3O2 Cathodes for Sodium-Ion Batteries

Enhanced Cycling Stability and Rate Capability of Al2O3-Coated NaNi1/3Fe1/3Mn1/3O2 Cathodes for Sodium-Ion Batteries

Stable electrochemical properties of trace titanium doping layered P3-type K0.5Mn0.92Ti0.08O2 cathode material for potassium ion batteries

The wide application of potassium ion batteries (PIBs) urgently requires the development of ideal cathode materials with low cost, good reaction kinetics and structural stability. Here, a titanium-doped K0.5Mn0.92Ti0.08O2 cathode material for potassium ion batteries is developed by doping modification strategy using a high-temperature solid-state method. The structure and performance structure-activity relationship of binary K0.5Mn1-xTixO2 cathode materials doped with non-electrochemically active element Ti4+ are studied experimentally and theoretically. With the introduction of Ti4+, when the doping amount is <10 mol%, the doped solid solution is hexagonal P3 phase, and the transition metal layer spacing increases. The non-equivalent doping affects the relative content of Mn3+/Mn4+, smoothes the redox peak in the electrochemical process, reduces the doping formation energy, and improves the structural stability. The ex-situ XRD fine structure study of the electrochemical process shows that the structural change of the material during the discharge process is suppressed after doping. The best Ti-doped cathode material K0.5Mn0.92Ti0.08O2 has an initial discharge capacity of 126.9 mAh·g−1 at a current density of 20 mA·g−1, and the capacity retention rate is 53.7 % after 100 cycles. This work provides a feasible strategy for the construction of stable electrode materials for PIBs.

Characterization of identical lithium-ion battery electrodes before and after charge/discharge cycles via in-plane large-area polishing

As an effective method to fabricate a large-area cross-sectional sample for lithium-ion battery electrodes, we perform in-plane polishing of LiNi0.8Co0.15Al0.05O2(NCA) cathode samples and obtain a large cross-sectional area with a diameter of 1.5 mm. The polished cross-sections of NCA cathode particles are sufficiently flat to perform the atomic force microscopy (AFM) measurements on each cathode particle. Following AFM-based Kelvin probe force microscopy and scanning spreading resistance microscopy measurements, an identical in-plane polished NCA sample is assembled into a coin cell for the charge and discharge processes. After 90 charge/discharge cycles, the in-plane-polished sample is successfully disassembled from the coin cell without causing critical damage. In addition, a microcrack structure, which is a typical degradation feature of the cycles of NCA particles, is observed for the identical in-plane polished NCA sample. This indicates that the in-plane polishing method is effective for investigating identical NCA electrode samples before and after the charge/discharge process. Furthermore, the in-plane polishing method can be successfully applied to the large-area polishing of a Si-based anode which is a mixture of Si carbon complexes and graphite particles. This study presents a novel methodology for analyzing the degradation of lithium-ion battery electrode materials.

A Material-Oriented Metallurgical Strategy to Prepare LiNi0.8Co0.15Al0.05O2 Cathode Material from Low-Nickel Matte

A Material-Oriented Metallurgical Strategy to Prepare LiNi0.8Co0.15Al0.05O2 Cathode Material from Low-Nickel Matte

Optimizing O3-type cathode materials with modified collector for sodium-ion batteries: Insights of interfacial reaction between collector and electrolyte

In order to obtain a sodium-ion battery with high energy density and good kinetic properties, high specific capacity of O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM111) cathode material and high ion migration rate of NaClO4 electrolyte are selected. The cycling performance of NaNi1/3Fe1/3Mn1/3O2 is tested at 0.5 C after pre-activation at 0.1 C. During the electrochemical testing, a kind of side reaction products are found on the surface of the electrode piece. Through Scanning emission microscopy (SEM), X-ray photoelectron spectroscopy analysis (XPS) and Raman tests, side reaction products are found on the current collector with NaClO4 and Fluoroethylene carbonate (FEC). The protective layers are constructed on the surface of Al foil to effectively avoid the occurrence of side reactions. The prepared half cells have excellent stability and rate performance by the modified current collector. After 100 cycles at 0.5 C, the specific discharge capacity is 106 mA h g−1. The specific discharge capacity at 5 C is 107.2 mA h g−1. This measure provides a new idea to the NFM111 cathode materials electrochemical test and offers research basis for the design of sodium ion battery with excellent dynamic performance. Meanwhile, it also eliminates industry doubts about the performance of sodium-ion batteries.

Balancing the redox activity against structure stability in high-voltage manganese/iron-based layered oxide cathodes through copper doping for potassium-ion batteries

Earth-abundant manganese/iron-based layered oxide cathodes display high energy densities in cost-effective potassium-ion batteries, but still encounter severe structure distortions and irreversible phase transformations upon cycling. To ameliorate its structural stability, the highly electronegative but electrochemically inactive Cu2+ is rationally introduced into Mn sites of P3-type K0.5Mn0.8Fe0.2O2 cathode materials to regulate crystal structures and elemental valences toward a balance between redox activity and structure stability. Ranging from 4.2 to 1.5 V, the optimal K0.5Mn0.7Fe0.2Cu0.1O2 cathode material with a lower formation energy and a narrower band gap could present a large initial discharging capacity of 91 mAh g−1 at 50 mA g−1 with an excellent capacity retention of 71.6 % over 50 cycles and a competitive capacity retention of 62.3 % at 100 mA g−1 after 100 cycles. Regardless of its compromised K+ diffusion capabilities from a slightly contracted interlayer, a superior rate performance of 71 mAh g−1 can be achieved at 500 mA g−1, implying a dominant function of structural stability in electrochemical depotassiation/potassiation. Additionally, the dynamic redox activities and high electrochemical reversibility of Mn4+/3+ and Fe4+/3+ couples are verified by ex-situ X-ray photoemission spectroscopies. This solid work would enlighten the novel structural manipulations of layered oxide cathodes for high-voltage potassium-ion batteries.

Improving structure stability of single-crystalline Ni-rich cathode at high voltage by element gradient doping and interfacial modification

Single-crystalline Ni-rich cathodes can provide high energy density and capacity retention rates for lithium-ion batteries (LIBs). However, single-crystalline Ni-rich cathodes experience severe transition metal dissolution, irreversible phase transitions, and reduced structural stability during prolonged cycling at high voltage, which will significantly hinder their practical application. Herein, a Li4TeO5 surface coating along with bulk Te-gradient doping strategy is proposed and developed to solve these issues for single-crystalline Ni-rich LiNi0.90Co0.05Mn0.05O2 cathode (LTeO-1.0). It has been found that the bulk Te6+ gradient doping can lead to the formation of robust Te–O bonds that effectively inhibit H2-H3 phase transformations and reinforce the lattice framework, and the in-situ Li4TeO5 coating layer can act as a protective layer that suppresses the parasitic reactions and grain fragmentation. Besides, the modified material exhibits a higher Young’s modulus, which will be conducive to maintaining significant structural and electrochemical stability under high-voltage conditions. Especially, the LTeO-1.0 electrode shows the improved Li+ diffusion kinetics and thermodynamic stability as well as high capacity retention of 95.83% and 82.12% after 200 cycles at the cut-off voltage of 4.3 and 4.5 V. Therefore, the efficacious dual-modification strategy will definitely contribute to enhancing the structural and electrochemical stability of single-crystalline Ni-rich cathodes and developing their application in LIBs.

Stimulating the Electrostatic Interactions in Composite Cathodes Using a Slurry-Fabricable Polar Binder for Practical All-Solid-State Batteries

In this work, poly vinylidene fluoride–chlorotrifluoroethylene (PVdF-CTFE) is introduced as a slurry-fabricable polymer binder to fabricate a stable composite cathode using the complex materials of a Li[Ni0.7Co0.1Mn0.2]O2 cathode, Li6PS5Cl electrolyte, and super C carbon, for sulfide-based all-solid-state batteries (ASSBs). The high electronegativity of fluorine in the poly(vinylidene fluoride–chlorotrifluoroethylene (PVdF-CTFE) binder creates a polarized electronic environment in the composite cathode, promoting electrostatic interactions with Li ions. Compared with that of butadiene rubber (BR), the PVdF-CTFE binder has a stronger binding energy to the complex materials in the composite cathode, which enhances the mechanical rigidity of the composite cathode with highly uniform adhesion. In addition, uniform and close contact between the complex materials in the composite cathode reduces the resistance at the interfaces, lowering the energy barrier for Li+ diffusion, and eventually creates a fast Li+ diffusion pathway in the composite cathode. Thus, the pouch-type ASSBs cell, which comprises the composite cathode with the PVdF-CTFE binder, Li6PS5Cl electrolyte sheet, and silver-carbon (Ag/C) Li-free anode delivers a high reversible capacity of 198.5 mAh g–1 at 0.1 C and long-term cycling stability over 300 cycles with a capacity retention of 74.5 % at 0.5 C at 60 °C.

Exploring the Optimal Binder Content in Composite Electrodes for Sulfide-Based All-Solid-State Lithium-Ion Batteries

All-solid-state batteries (ASSBs) are promising next-generation batteries owing to their improved safety compared with lithium-ion batteries using flammable liquid electrolytes. Among various solid electrolytes, sulfide-based electrolytes exhibit high ionic conductivities, and their ductile properties allow them to be easily processed without high-temperature sintering. In sulfide-based ASSBs, a polymer binder is essential for achieving a good cycling performance by maintaining strong interfacial contacts in the composite electrodes during cycling. In this study, we prepared a composite Si-C anode and a LiNi0.82Co0.1Mn0.08O2 cathode using a nitrile-butadiene rubber binder for ASSB applications, and investigated the effect of the binder content on the mechanical properties and electrochemical performance. The binder content significantly influenced the physical and electrochemical characteristics of the composite electrodes, and the ASSB prepared with 1.5 wt% binder showed the best cycling performance considering capacity retention and rate capability. Furthermore, we investigated how the excess binder adversely affected the cycling performance through time-of-flight secondary ion mass spectrometry analysis.

Diethylenetriaminepentaacetic Acid-based Conducting Solid Polymer Electrolytes Impede Lithium Dendrites and Impart Antioxidant Capacity in Lithium-Ion Batteries.

In the development of lithium-ion batteries (LIBs), cheaper and safer solid polymer electrolytes are expected to replace combustible organic liquid electrolytes to meet the larger market demand. However, low ionic conductivity and inadequate cycling stability impede their commercial viability. Herein, a novel flexible conducting solid polymer electrolytes (CSPEs) based on polyvinyl alcohol (PVA) and ion-polarized diethylenetriaminepentaacetic acid (P-DETP) is developed for the first time and applied in LIBs. PVA and P-DETP form a compact polymer network through hydrogen bonding, enhancing the thermomechanical stability of CSPE while restricting the migration of larger anions. Furthermore, density functional theory calculations confirm that P-DETP can facilitate the dissociation of Li+-TFSI- via electrostatic attraction, resulting in increased mobility of lithium ions. Additionally, P-DETP contributes to the formation of a stable electrode-electrolyte interface layer, effectively suppressing the growth of lithium dendrites and improving antioxidant capacity. These synergistic effects enable CSPE to exhibit remarkable properties including high ionic conductivity (2.8 × 10-4 S cm-1), elevated electrochemical potential (5.1V), and excellent lithium transference number (0.869). Notably, the P-DETP/LiTFSI CSPE demonstrates stable performance not only in LiFePO4 batteries but also adapts to high-nickel ternary LiNi0.88Co0.06Mn0.06O2 cathode, highlighting its immense potential for application in high energy density LIBs.

Grain-Boundary Engineering of Na3Bi/NaF Dual-Functional Heterogeneous Protective Layer for Highly Stable Sodium Metal Anodes

Sodium-metal batteries have been extensively recognized as a potential alternative to lithium-metal batteries. However, the huge volume expansion, inhomogeneous distribution of the electrical field, and sluggish Na+ diffusion at the electrolyte/electrode interface are insurmountable challenges to achieving high cycling performance and a long lifespan. In this work, a dual-functional heterogeneous protective layer consisting of Na3Bi/NaF was constructed on the surface of metallic sodium (abbr. BiF3/Na) by the spontaneous reduction reactions between metallic sodium and BiF3 powder at room temperature. Attributing to the in-situ formation of rich grain boundaries and the built-in electric field between the components, the charge transfer, Na+ diffusion rate as well as mechanical strength of the BiF3/Na anode were extensively improved. Consequently, the sodium metal anode with the Na3Bi/NaF dual-functional heterogeneous layer achieves an excellent cycling capability and long cycling lifespan of more than 2000 hours at a large current density of 2 mA cm-2 and an area capacity of 1 mAh cm-2. In addition, by further matching with the commercialized NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode, the prepared BiF3/Na||NFM full cell exhibits high durability (68.8 mAh g-1 after 2000 cycles at 2 C). This work utilizing grain boundary engineering has provided a promising strategy for achieving dendrite-free sodium metal anodes and high-energy density sodium metal batteries.

Simultaneous structure and surface engineering of metal-organic framework derived LiNi0.5-xFe2xMn1.5-xO4 cathode material for improving high voltage performance of lithium-ion batteries

This study presents a novel material synthesis approach utilizing a terephthalic acid-based metal-organic framework as a precursor and employing an ethanol-assisted hydrothermal treatment to produce high-performance Fe-doped LiNi0.5Mn1.5O4 (LNMO) cathode material. This strategy yields a well-crystallized spinel structure with uniformly distributed transition metal ions. Additionally, the appropriate quantity of Fe dopant can achieve the desired Mn3+/Mn4+ ratio, level of structural disordering, and crystal phase purity for Fe-doped LNMO. The synthesis process also aids in forming an amorphous Li2CO3 surface layer, approximately 1 nm thick, which protects the active material from excessive reaction with electrolyte. The typical Fe-doped LNMO cathode (S-05) exhibits superior performance compared to a commercialized LNMO counterpart. It delivers an initial discharge capacity of 135 mAh g-1 at 1 C with exceptional cycling stability over 500 cycles (capacity retention of 90%) under high voltage (5.0 V vs. Li+/Li). Furthermore, its rate capability significantly improves, with a capacity retention of 85% (5 C/0.2 C). This enhanced performance aligns with evidence of activated Ni2+/Ni3+/Ni4+ redox reactions and suppressed cathode electrolyte interphase resistance, leading to promoted Li+ diffusion. Moreover, it is found the cathode helps alleviate electrolyte degradation at high voltages by inhibiting the formation of singlet oxygen in the electrolyte.

Effect of Conductive Carbon Morphology on the Cycling Performance of Dry-Processed Cathode with High Mass Loading for Lithium-Ion Batteries

The solvent-free dry processing of electrodes is highly desirable to reduce the manufacturing cost of lithium-ion batteries (LIBs) and increase the active mass loading in the electrode. The drying process is based on the fibrillation of the polytetrafluoroethylene binder induced by shear force. This technique offers the advantage of uniformly dispersing the active material and conductive carbon without binder migration, thereby facilitating the fabrication of thick electrode with high mass loading. In this study, we explored the influence of conductive carbon morphology on the cycling performance of dry-processed LiNi0.82Co0.10Mn0.08O2 (NCM) cathodes. In contrast to Super P, which provided electronic pathways through point-contact, the fibrous structure of the vapor-grown carbon fibers (VGCFs) promoted line-contact, ensuring long and less-torturous electronic pathways and enhanced utilization of active materials. Consequently, the cathode employing fibrous VGCFs achieved higher electrical conductivity, resulting in enhanced electrochemical performance. The dry-processed NCM cathode employing VGCF with an areal capacity of 8.5 mAh cm−2 delivered a high discharge capacity of 212 mAh g−1 with good capacity retention. X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were conducted to investigate the degradation behavior of the high-mass-loaded cathodes with two different conductive carbons.

Quantitative pre-lithiation modulation of aluminum foil anode kinetics enables high rate and stable cycling of high-loading all-solid-state batteries

Aluminum (Al) foil holds great promise as a pure alloy anode for all-solid-state batteries (ASSBs) due to its suitable potential, high theoretical capacity, and excellent electronic conductivity. However, it remains challenging to achieve high reversibility and stability of the Al foil anode for ASSBs. Herein, we investigate the morphological and lithium (Li) kinetics evolutions of the Al foil anode paired with sulfide solid-state electrolyte (SSE). We identify that the significant reversible capacity loss stems from diminished Li kinetics at low Li contents (LixAl, 0 < x < 0.5), where the accumulation of pores and pure delithiated Al phase obstructs Li diffusion, increasing interfacial resistance and overpotential. Conversely, the Al foil anode with high Li contents (LixAl, 0.5 < x < 1) demonstrates reversible structures and rapid Li kinetics. Through precise pre-lithiation control, ASSBs with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes exhibit outstanding rate capabilities and cycling stability, achieving over 4,000 cycles with 82.1 % capacity retention at 5C and demonstrating long-term cycling over 1,000 cycles with nearly 100 % capacity retention at ultra-high loadings. This work offers a viable strategy for advancing practical-level ASSBs with enhanced performance and longevity, contributing valuable insights to future battery technology.

Introducing strong metal-oxygen bonds to suppress the Jahn-Teller effect and enhance the structural stability of Ni/Co-free Mn-based layered oxide cathodes for potassium-ion batteries

Mn-based layered oxides (KMO) have emerged as one of the promising low-cost cathodes for potassium-ion batteries (PIBs). However, due to the multiple-phase transitions and the distortion in the MnO6 structure induced by the Jahn-Teller (JT) effect associated with Mn-ion, the cathode exhibits poor structural stability. Herein, we propose a strategy to enhance structural stability by introducing robust metal-oxygen (M–O) bonds, which can realize thepinning effect to constrain the distortion in thetransition metal (TM) layer. Concurrently, all the elements employed have exceptionally high crustal abundance. As a proof of concept, the designed K0.5Mn0.9Mg0.025Ti0.025Al0.05O2 cathode exhibited a discharge capacity of approximately 100 mA h g−1 at 20 mA g−1 with 79% capacity retention over 50 cycles, and 73% capacity retention over 200 cycles at 200 mA g−1, showcased much better battery performance than the designed cathode with less robust M–O bonds. The properties of the formed M–O bonds were investigated using theoretical calculations. The enhanced dynamics, mitigated JT effect, and improved structural stability were elucidated through the in-situ X-ray diffractometer (XRD), in-situ electrochemical impedance spectroscopy (EIS) (and distribution of relaxation times (DRT) method), and ex-situ X-ray absorption fine structure (XAFS) tests. This study holds substantial reference value for the future design of cost-effective Mn-based layered cathodes for PIBs.

A family of dual-anion-based sodium superionic conductors for all-solid-state sodium-ion batteries.

The sodium (Na) superionic conductor is a key component that could revolutionize the energy density and safety of conventional Na-ion batteries. However, existing Na superionic conductors are primarily based on a single-anion framework, each presenting inherent advantages and disadvantages. Here we introduce a family of amorphous Na-ion conductors (Na2O2-MCly, M = Hf, Zr and Ta) based on the dual-anion framework of oxychloride. Benefiting from a dual-anion chemistry and with the resulting distinctive structures, Na2O2-MCly electrolytes exhibit room-temperature ionic conductivities up to 2.0 mS cm-1, wide electrochemical stability windows and desirable mechanical properties. All-solid-state Na-ion batteries incorporating amorphous Na2O2-HfCl4 electrolyte and a Na0.85Mn0.5Ni0.4Fe0.1O2 cathode exhibit a superior rate capability and long-term cycle stability, with 78% capacity retention after 700 cycles under 0.2 C (1C = 120 mA g-1) at room temperature. The discoveries in this work could trigger a new wave of enthusiasm for exploring new superionic conductors beyond those based on a single-anion framework.