Search

Layered transition metal oxide cathodes have been one of the dominant cathodes for lithium‐ion batteries with efficient Li+ intercalation chemistry. However, limited by the weak layered interaction and unstable surface, mechanical and chemical failure plagues their electrochemical performance, especially for Ni‐rich cathodes. Here, adopting a simultaneous elemental‐structural atomic arrangement control based on the intrinsic Ni−Co−Mn system, the surface role is intensively investigated. Within the invariant oxygen sublattice of the crystal, a robust surface with the synergistic concentration gradient and layered‐spinel intertwined structure is constructed on the model single‐crystalline Ni‐rich cathode. With mechanical strain dissipation and chemical erosion suppression, the cathode exhibits an impressive capacity retention of 82 % even at the harsh 60 °C after 150 cycles at 1 C. This work highlights the coupling effect of structure and composition on the chemical‐mechanical properties, and the concept will spur more researches on the cathodes that share the same sublattice. [ABSTRACT FROM AUTHOR]

A single-crystalline Ni-rich (SCNR) cathode with a large particle size can achieve higher energy density, and is safer, than polycrystalline counterparts. However, synthesizing large SCNR cathodes (>5 μm) without compromising electrochemical performance is very challenging due to the incompatibility between Ni-rich cathodes and high temperature calcination. Herein, we introduce Vegard's Slope as a guide for rationally selecting sintering aids, and we successfully synthesize size-controlled SCNR cathodes, the largest of which can be up to 10 μm. Comprehensive theoretical calculation and experimental characterization show that sintering aids continuously migrate to the particle surface, suppress sublattice oxygen release and reduce the surface energy of the typically exposed facets, which promotes grain boundary migration and elevates calcination critical temperature. The dense SCNR cathodes, fabricated by packing of different-sized SCNR cathode particles, achieve a highest electrode press density of 3.9 g cm−3 and a highest volumetric energy density of 3000 Wh L−1. The pouch cell demonstrates a high energy density of 303 Wh kg−1, 730 Wh L−1 and 76% capacity retention after 1200 cycles. SCNR cathodes with an optimized particle size distribution can meet the requirements for both electric vehicles and portable devices. Furthermore, the principle for controlling the growth of SCNR particles can be widely applied when synthesizing other materials for Li-ion, Na-ion and K-ion batteries. [ABSTRACT FROM AUTHOR]

Na-ion cathode materials operating at high voltage with a stable cycling behavior are needed to develop future high-energy Na-ion cells. However, the irreversible oxygen redox reaction at the high-voltage region in sodium layered cathode materials generates structural instability and poor capacity retention upon cycling. Here, we report a doping strategy by incorporating light-weight boron into the cathode active material lattice to decrease the irreversible oxygen oxidation at high voltages (i.e., >4.0 V vs. Na+/Na). The presence of covalent B–O bonds and the negative charges of the oxygen atoms ensures a robust ligand framework for the NaLi1/9Ni2/9Fe2/9Mn4/9O2 cathode material while mitigating the excessive oxidation of oxygen for charge compensation and avoiding irreversible structural changes during cell operation. The B-doped cathode material promotes reversible transition metal redox reaction enabling a room-temperature capacity of 160.5 mAh g−1 at 25 mA g−1 and capacity retention of 82.8% after 200 cycles at 250 mA g−1. A 71.28 mAh single-coated lab-scale Na-ion pouch cell comprising a pre-sodiated hard carbon-based anode and B-doped cathode material is also reported as proof of concept. The irreversible oxygen redox reaction during charging to the high-voltage region causes cathode structural degradation and Na-ion cell capacity fading. Here, the authors report a B-doped cathode active material to mitigate the irreversible oxygen oxidation and increase the cell capacity. [ABSTRACT FROM AUTHOR]

A hybrid solid/liquid electrolyte with superior security facilitates the implementation of high‐energy‐density storage devices, but it suffers from inferior chemical compatibility with cathodes. Herein, an optimal lithium difluoro(oxalato)borate salt was introduced to build in situ an amorphous cathode electrolyte interphase (CEI) between Ni‐rich cathodes and hybrid electrolyte. The CEI preserves the surface structure with high compatibility, leading to enhanced interfacial stability. Meanwhile, the space‐charge layer can be prominently mitigated at the solid/solid interface via harmonized chemical potentials, acquiring promoted interfacial dynamics as revealed by COMSOL simulation. Consequently, the amorphous CEI integrates the bifunctionality to provide an excellent cycling stability, high Coulombic efficiency, and favorable rate capability in high‐voltage Li‐metal batteries, innovating the design philosophy of functional CEI strategy for future high‐energy‐density batteries. [ABSTRACT FROM AUTHOR]

Solid-state batteries provide a safe and high energy density solution to next-generation energy storage devices. However, unsatisfactory power capability and cycling stability raised from lithium diffusion resistance and catalytic reaction at the electrode/electrolyte interface critically restrict their development. In this study, these interfacial issues are ameliorated by LiBO 2 coating to achieve the successful implementation of nickel-rich LiNi 0.6 Co 0.2 Mn 0.2 O 2 in poly(ether-acrylate) based solid-state batteries. The continuous coating acts not only as a physical barrier hindering the decomposition of polymer electrolyte but also as a buffer layer promoting lithium diffusion across the space charge layer owing to its electronic insulativity and ionic conductivity. In consequence, the LiBO 2 coated nickel-rich cathode delivers superior cycling stability with a capacity retention of 84.3% during 150 cycles at 0.5C, remarkably improved lithium diffusion kinetics with an order of magnitude increase in apparent diffusion coefficient and prominent power performance with 97 mA h g−1 at 2C. The effectiveness of inserting such functional interlayer emphasizes the essentiality of interfacial chemistry in building high-performance solid-state Li metal batteries. Image 1 • LiBO 2 coating is constructed on nickel-rich layered LiNi 0.6 Co 0.2 Mn 0.2 O 2. • Coating provides a physical barrier against decomposition of polymer electrolyte. • LiBO 2 suppresses the space charge layer and promotes interfacial ion diffusion. • Cathode shows improved cycling and power capability in solid-state batteries. [ABSTRACT FROM AUTHOR]

Abstract: Solid‐state Li secondary batteries may become high energy density storage devices for the next generation of electric vehicles, depending on the compatibility of electrode materials and suitable solid electrolytes. Specifically, it is a great challenge to obtain a stable interface between these solid electrolytes and cathodes. Herein, this issue can be effectively addressed by constructing a poly(acrylonitrile‐co‐butadiene) coated layer onto the surface of LiNi0.6Mn0.2Co0.2O2 cathode materials. The polymer layer plays a vital role in working as a protective shell to retard side reaction and ameliorate the contact of the solid–solid interface during the cycling process. In the resultant solid‐state batteries, both rate capacity (99 mA h g−1 at 3 C) and cycling stability (75% capacity retention after 400 cycles) are improved after coating. This impressive performance highlights the great importance of layer modification in the cathode and inspires the development of solid‐state batteries toward practical applications. [ABSTRACT FROM AUTHOR]

Abstract: Delivery of high‐energy density with long cycle life is facing a severe challenge in developing cathode materials for rechargeable sodium‐ion batteries (SIBs). Here a composite Na0.6MnO2 with layered–tunnel structure combining intergrowth morphology of nanoplates and nanorods for SIBs, which is clearly confirmed by micro scanning electron microscopy, high‐resolution transmission electron microscopy as well as scanning transmission electron microscopy with atomic resolution is presented. Owing to the integrated advantages of P2 layered structure with high capacity and that of the tunnel structure with excellent cycling stability and superior rate performance, the composite electrode delivers a reversible discharge capacity of 198.2 mAh g−1 at 0.2C rate, leading to a high‐energy density of 520.4 Wh kg−1. This intergrowth integration engineering strategy may modulate the physical and chemical properties in oxide cathodes and provide new perspectives on the optimal design of high‐energy density and high‐stable materials for SIBs. [ABSTRACT FROM AUTHOR]

The rapid capacity decay caused by the poor contact and large polarization at the interface between the cathode and solid electrolytes is still a big challenge to overcome for high-power-density solid batteries. In this study, a superior Li+ conductive transition layer Li1.4Al0.4Ti1.6(PO4)3 is introduced to coat LiNi0.6Co0.2Mn0.2O2, as a model cathode, to mitigate polarization and enhance dynamic characteristics. The critical attribute for such superior dynamics is investigated by the atomic force microscopy with boundary potential analysis, revealing that the formed interfacial transition layer provides a gradual potential slope and sustain-released polarization, and endows the battery with improved cycling stability (90% after 100 cycles) and excellent rate capability (116 mA h g-1 at 2 C) at room temperature, which enlightens the comprehension of interface engineering in the future solid batteries systems. [ABSTRACT FROM AUTHOR]

Spinel‐type LiMn2O4 cathode materials commonly suffer from manganese dissolution due to the severe interfacial side reactions especially at elevated temperature. Here, a 3D hollow fusiform LiMn2O4 cathode material is reported with preferentially exposed stable {111} facets and seamless outer structure, which is clearly confirmed by microfocused ion beam scanning electron microscopy, high‐resolution transmission electron microscopy as well as scanning transmission electron microscopy with atomic resolution. Owing to the optimal geometrical structure design and the preferentially exposed stable {111} facets, the electrode delivers excellent rate capability (107.6 mAh g−1 at 10 C), remarkable cycling stability (83.3% capacity retention after 1000 cycles at 1 C), and outstanding high‐temperature performance. Together with the analyses of electrochemical behaviors, in situ X‐ray diffraction at different temperatures, and ex situ X‐ray photoelectron spectra, the underlying working mechanism for suppressing manganese dissolution is clearly articulated. These findings could provide significant guidelines for precisely designing highly stable cathode materials for LIBs. [ABSTRACT FROM AUTHOR]

As one of the most promising cathode candidates for room‐temperature sodium‐ion batteries (SIBs), P2‐type layered oxides face the challenge of simultaneously realizing high‐rate performance while achieving long cycle life. Here, a stable Na2/3Ni1/6Mn2/3Cu1/9Mg1/18O2 cathode material is proposed that consists of multiple‐layer oriented stacking nanoflakes, in which the nickel sites are partially substituted by copper and magnesium, a characteristic of the material that is confirmed by multiscale scanning transmission electron microscopy and electron energy loss spectroscopy techniques. Owing to the optimal morphology structure modulation and chemical element substitution strategy, the electrode displays remarkable rate performance (73% capacity retention at 30C compared to 0.5C) and outstanding cycling stability in Na half‐cell system couple with unprecedented full battery performance. The underlying thermal stability, phase stability, and Na+ storage mechanisms are clearly elucidated through the systematical characterizations of electrochemical behaviors, in situ X‐ray diffraction at different temperatures, and operando X‐ray diffraction upon Na+ deintercalation/intercalation. Surprisingly, a quasi‐solid‐solution reaction is switched to an absolute solid‐solution reaction and a capacitive Na+ storage mechanism is demonstrated via quantitative electrochemical kinetics calculation during charge/discharge process. Such a simple and effective strategy might reveal a new avenue into the rational design of excellent rate capability and long cycle stability cathode materials for practical SIBs. [ABSTRACT FROM AUTHOR]

The growing concern for high energy density lithium-ion batteries requires high capacity cathode materials. Li-rich materials are among the most promising candidates attributing to its high capacity, high safety, and low cost. However, the capacity faded seriously with long cycling which hinders its further application. Here, we report a high capacity Li-rich material with superior rate capacity and well cycling stability. The prepared Li-rich cathode exhibited a high discharge capacity of 270 mA h g −1 with initial coulombic efficiency of 84%, at the current density of 25 mA g −1 . In addition, high discharge capacity of 200 mA h g −1 was obtained at the current density of 250 mA g −1 and good cycling stability was delivered with 92% capacity retention after 100 cycles at current density of 125 mA g −1 . [ABSTRACT FROM AUTHOR]