Solid-state lithium metal batteries as promising energy storage devices have gathered many attentions for its appealing properties, such as improved safety and capacity density. Nevertheless, high ...interfacial resistance, uneven current density and severe Li dendrite growth caused by rigid contact at the cathode-electrolyte interface in solid-state batteries greatly restrict its electrochemical performance and further practical application. Herein, a cathode-electrolyte integrating strategy is proposed to achieve the soft interfacial contact through employing poly(vinylidene fluoride)-based composite electrolyte as the cathode binder and subsequent heat-pressing procedure. Due to the modification strategy, fabricated cells with integrated structure show lower resistance, faster Li-ion transport, enhanced capacity and improved cycle stability. The integrated LiFePO4/Li cell exhibits superior electrochemical performance, which present a capacity retention of 93.8% and 91.6% after 300 cycles at 0.5 C and 400 cycles at 1 C, respectively, being able to compare favorably with the conventional cells using liquid electrolyte. Overall, the study provides a solution for designing advanced solid-state lithium metal batteries.
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•PVDF-based composite solid electrolyte and composite cathode are prepared.•A cathode-electrolyte integrated cell is fabricated by heat-pressing.•The cathode-electrolyte integrating strategy boosts the cycle stability.
The single-crystalline Ni-rich cathode has aroused much attention for extenuating the cycling and safety crises in comparison to the polycrystalline cathode. However, planar gliding and kinetic ...hindrance hinder its chemo-mechanical properties with cycling, which induce delamination cracking and damage the mechanical integrity in single crystals. Herein, a robust Li
(Sc
Ti
)
(PO
)
(LSTP) ion/electron conductive network was constructed to decorate single-crystal LiNi
Co
Mn
O
(SC90) particles. Via physicochemical characterizations and theoretical calculations, this LSTP coating that evenly grows on the SC90 particle with good lattice matching and strong bonding effectively restricts the anisotropic lattice collapse along the c-axis and the cation mixing activity of SC90, thus suppressing planar gliding and delamination cracking during repeated high-voltage lithiation/delithiation processes. Moreover, such a 3D LSTP network can also facilitate the lithium-ion transport and prevent the electrolyte's corrosion, lightening the kinetic hindrance and triggering the surface phase transformation. Combined with the Li metal anode, the LSTP-modified SC90 cell exhibits a desirable capacity retention of 90.5% at 5 C after 300 cycles and stabilizes the operation at 4.3/4.5 V. Our results provide surface modification engineering to mitigate planar gliding and kinetic hindrance of the single-crystalline ultra-high Ni-rich cathode, which inspires peers to design other layered cathode materials.
•The relationship between mechanical integrity issues and electrochemical properties is systematically studied.•The bulk structure and interaction mechanism of substituted cations and nickel-rich ...layered oxides are studied in depth.•This paper provides guidance for the study of the mechanical properties of energy materials.
Mechanical integrity issues of Ni-rich cathode materials are major bottlenecks for their commercial application, stemming from the abrupt anisotropic lattice contraction during H2 ↔ H3 phase transitions. Herein, zirconium is used to modify LiNi0.9Co0.05Mn0.05O2 to solve the mechanical integrity issues. The relationship between the mechanical integrity issues and electrochemical performance is systematically examined to gain insights into the Zr activity-governing mechanisms. Results find that the addition of zirconium not only improves the diffusion ability of lithium ions by providing a rapid channel for diffusion of lithium ions, but also enhances mechanical properties by inhibiting cation mixing. As a result, the optimal LiNi0.9Co0.05Mn0.05O2 achieves superiority capacity retention of 84.12 % after 200 cycles at 5C, higher than that of unmodified LiNi0.9Co0.05Mn0.05O2 74.32 %. This work deeply investigates the information on the bulk structure and interaction mechanism between substitution cations and Ni-rich layered oxides, which provides a new insight to design and construct of advanced high-capacity cathode materials.
•High Lithium Extraction Rate.•Success direct regeneration of de-lithiated product.•Mechanism about de-lithiation and regeneration processes.
The recycling of spent lithium-ion batteries has become ...an urgent imperative. Electrochemical technology is emerging as an environmentally friendly approach for selectively extracting lithium from discarded cathode materials, garnering significant attention. However, the lack of a clear understanding of the structural evolution during the de-lithiation process, and the re-lithiation mechanism of transition-metal oxides after lithium extraction, hinder the direct regeneration of de-lithiated materials into battery-worthy materials. This limitation also impeds the further advancement of this promising technology. Here, for the first time the structural transformation associated with water-molecule intercalation during the electrochemical process of spent layer material (LiNi0.55Co0.15Mn0.3O2) is demonstrated. X-ray diffraction technique monitors the structural evolution upon de-lithiation, revealing an unusual phase transformation from H3 to “H4” driven by water-molecule intercalation. This transformation triggers significant lattice expansion along c-axis and introduces notable lattice distortion in de-lithiated material. These characteristics render direct calcination for material regeneration impractical, due to lattice collapse from dehydration, obstructing lithium intercalation at high temperatures. Interestingly, low-temperature calcination can endow resynthesized materials with a well-ordered layer structure after creating a lithium-water-balance layer structure for de-lithiated materials by hydrothermal process. Consequently, the regenerated material delivers a capacity of 132.5 mAh/g at 5C.
Layered manganese oxide represents one most potential cathode for sodium-ion batteries thanks to high theoretical specific capacity, low cost and environmental friendliness. Nevertheless, its surface ...structure degrades owing to the hydration reaction when being stored in the humid air. Herein, Na0.67Mn0.92Cu0.04Fe0.04O2 (NMCFO) cathode material is functionalized by tetradecylphosphonic acid (TPA) on the surface to enhance the air stability. It is demonstrated that the TPA protection layer could improve the surface hydrophobicity, and further inhibit the hydration reaction to produce residual alkali, effectively maintaining modified material’s crystal structure and electrochemical performance. After 28 days of placement in the humid air, the modified material delivers a specific capacity of 94.0 mAh g−1 at 5C, and exhibits a capacity retention of 92.22% after 100 cycles at 1C. In summary, we provide an effective pathway to protect layered manganese oxide and other moisture-sensitive materials without sacrificing cell performance.
The nickel-rich layered cathode material LiNi0.8Co0.15Al0.05O2 (NCA) is receiving enormous attention for its high energy density and low cost. Nevertheless, its wide application is limited by its ...unsatisfactory cycle performance and rate performance. In this study, the synergetic modification of the Nd2AlO3N coating and Nd3+ doping is realized to enhance the electrochemical performance of NCA. The Nd2AlO3N coating can protect the electrode-electrolyte interface and inhibit the side reactions. In the meantime, the Nd3+ doping, with the larger ion radius of Nb3+ and stronger Nd-O bond energy, can effectively enhance the kinetics performance and stabilize the crystal structure of the NCA cathode material. The modified materials with above characters demonstrate an excellent electrochemical stability and kinetics performance, among which the Nd4000 sample has the quite best performance, and its capacity/capacity retention still reach 168 mAh g−1/91% after 200 cycles, which are distinctly higher than the pristine 144.6 mAh g−1/78.5%. The electrochemical impedance spectra and cyclic voltammetry results also demonstrate that the charge transfer resistance and electrode polarization are suppressed with neodymium modifying during the cycle, and the lithium ion diffusion coefficient is significantly increased compared with the pristine sample.
The lithiated metal oxide precursor with α-NaFeO2 structure and low crystallinity prepared by a hydrothermal process is verified to be Li-Ni-Co-Mn-Mo composite oxide. The layered ...Li(Ni0.5Co0.2Mn0.3)1-xMoxO2 (x=0, 0.005, 0.01 and 0.02) cathode material with high crystallinity for lithium ion batteries (LIBs) is obtained from the lithiated metal oxide precursor by heat treatment. The results of SEM and EDS mapping characterization indicate that the molybdenum is distributed in the materials homogeneously. The effects of molybdenum on the structure, morphology and electrochemical performances of the LiNi0.5Co0.2Mn0.3O2 are extensively studied. According to the results of electrochemical characterizations, the Li(Ni0.5Co0.2Mn0.3)0.99Mo0.01O2 sample exhibits the best discharge cycling performance with capacity retention of 97.0% after 50 cycles, and an excellent rate performance of 125.5 mAh·g−1 at 8C rate. The Li(Ni0.5Co0.2Mn0.3)0.99Mo0.01O2 sample also shows a lower potential polarization, smaller impedance parameters and a larger Li+ diffusion by CV and EIS analyses.
Involving more nickel proportion in Ni-rich cathodes, edging to LiNiO2, is an inevitable trend to satisfy the demand of high energy density in lithium-ion batteries, but an inducement for the severer ...formation of undesirable lithium residues. To overcome the consequent degradation behaviors, a LiCoO2@Co3O4 complex coating layer is successfully realized on the surface of LiNiO2 via a facile wet-chemical method taking advantage of the Li-reactive ability of Co3O4. As a result, the 0.4 wt.% Co modified material exhibits competitively enhanced cyclic performance with 178.1 mAh g−1 after 50 cycles at 1 C, 11% higher than the pristine one in retention rate. Even at higher rates and temperature, it shows better electrochemical stability as well. The superior electrochemical properties of LiCoO2@Co3O4 coated LiNiO2 is ascribed to the dual-function of the coating method, where Co3O4 is formed during heat treatment and simultaneously reacted with surface lithium residues to generate LiCoO2. In combination of bulk and surface characterization, the significant effects of the coating layer on stabilizing material interface and strengthening the kinetic characteristics for LiNiO2 cathode materials are investigated and elucidated in detail.
To improve the electrical properties of modified CaMnO
3
powders, we synthesized Ca
1−
x
Er
x
MnO
3
(CEM) (0 ≤
x
≤ 0.3) powders by sol–gel autocombustion technology. The effects of the Er-doping ...concentration on the structure and electrical properties of the powders were studied. The results show that Er-doping can decrease the resistivity of the CEM powders effectively and the variation of the resistivity presents a typical V-type with increasing Er-doping concentration. The resistivity reaches the lowest point of 0.5258 Ω m at
x
= 0.25. Meanwhile, the Ca
0.75
Er
0.25
MnO
3
powder showed good frequency stability and higher conductivity at high temperatures. x-Ray diffraction (XRD) patterns and valence analysis illustrate that the grain size and average valence of the Mn ions, which relate to the resistivity of the CEM powders, are affected by the Er-doping concentration. When
x
= 0.25, the average valence of the Mn ions reaches the lowest point of 3.576. Scanning electron microscopy (SEM) analysis demonstrates that higher Er-doping concentration leads to smaller grain size in the CEM powders. Er-doping restrains the growth of the powder particles while decreasing the porosity and increasing the unit cell volume, resulting in improvement of the electrical properties of the modified powders.
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