Mo-doped nickel-rich LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode material is prepared by a solid-state method to enhance the high voltage electrochemical performances of the NCM622 material for lithium-ion ...batteries. The molybdenum element is proved to be homogeneously distributed inside the particles of the NCM622 material according to the result from the EDS mapping of the particle cross-section. The effects of Mo doping on the crystal structure, morphology, electrochemical properties and high-temperature performances of the NCM622 material are investigated in detail. The Mo-doped sample delivers a discharge capacity of 203.1 mAh/g and a capacity retention of 82.96% after 100 cycles at 1C under a high cut-off voltage of 4.6 V. Besides, the Mo-modified material exhibits a better rate performance of 159.9 mAh/g at 8C and lower voltage fading compared with the unmodified material. The significant improvements in electrochemical properties are ascribed to the fact that trace Mo ions doped into the transition-metal layer help to enlarge the lithium slab spacing, stabilize the crystal structure and suppress the electrode polarization. It is also demonstrated that Mo doping effectively suppresses the pulverization of particles and reduces the charge transfer resistance according to the SEM and EIS analyses.
•The molybdenum element is uniformly doped inside the particles of the LiNi0.6Co0.2Mn0.3O2 cathode material.•High-voltage electrochemical performances and crystal structure stabilities are improved by Mo doping.•Mo doping reduces the Li/Ni disorder degree, enlarges the lithium slab spacing and suppresses the pulverization of particles.
Planar gliding along with anisotropic lattice strain of single‐crystalline nickel‐rich cathodes (SCNRC) at highly delithiated states will induce severe delamination cracking that seriously ...deteriorates LIBs’ cyclability. To address these issues, a novel lattice‐matched MgTiO3 (MTO) layer, which exhibits same lattice structure as Ni‐rich cathodes, is rationally constructed on single‐crystalline LiNi0.9Co0.05Mn0.05O2 (SC90) for ultrastable mechanical integrity. Intensive in/ex situ characterizations combined with theoretical calculations and finite element analysis suggest that the uniform MTO coating layer prevents direct contact between SC90 and organic electrolytes and enables rapid Li‐ion diffusion with depressed Li‐deficiency, thereby stabilizing the interfacial structure and accommodating the mechanical stress of SC90. More importantly, a superstructure is simultaneously formed in SC90, which can effectively alleviate the anisotropic lattice changes and decrease cation mobility during successive high‐voltage de/intercalation processes. Therefore, the as‐acquired MTO‐modified SC90 cathode displays desirable capacity retention and high‐voltage stability. When paired with commercial graphite anodes, the pouch‐type cells with the MTO‐modified SC90 can deliver a high capacity of 175.2 mAh g−1 with 89.8% capacity retention after 500 cycles. This lattice‐matching coating strategy demonstrate a highly effective pathway to maintain the structural and interfacial stability in electrode materials, which can be a pioneering breakthrough in commercialization of Ni‐rich cathodes.
A lattice‐matched MTO coating has successfully been built on ultrahigh single‐crystal LiNi0.9Co0.05Mn0.05O2 particle by a neoteric in situ chemical reaction process, which can not only relieve lattice strain by avoiding inhomogeneity of the Li‐ion concentration, but also suppress cation mixing and irreversible oxygen loss for ensuring the smooth transportation of Li‐ion, thus preventing planar gliding and delamination cracking along the sliding planes.
Planar gliding along with anisotropic lattice strain of single-crystalline nickel-rich cathodes (SCNRC) at highly delithiated states will induce severe delamination cracking that seriously ...deteriorates LIBs' cyclability. To address these issues, a novel lattice-matched MgTiO
(MTO) layer, which exhibits same lattice structure as Ni-rich cathodes, is rationally constructed on single-crystalline LiNi
Co
Mn
O
(SC90) for ultrastable mechanical integrity. Intensive in/ex situ characterizations combined with theoretical calculations and finite element analysis suggest that the uniform MTO coating layer prevents direct contact between SC90 and organic electrolytes and enables rapid Li-ion diffusion with depressed Li-deficiency, thereby stabilizing the interfacial structure and accommodating the mechanical stress of SC90. More importantly, a superstructure is simultaneously formed in SC90, which can effectively alleviate the anisotropic lattice changes and decrease cation mobility during successive high-voltage de/intercalation processes. Therefore, the as-acquired MTO-modified SC90 cathode displays desirable capacity retention and high-voltage stability. When paired with commercial graphite anodes, the pouch-type cells with the MTO-modified SC90 can deliver a high capacity of 175.2 mAh g
with 89.8% capacity retention after 500 cycles. This lattice-matching coating strategy demonstrate a highly effective pathway to maintain the structural and interfacial stability in electrode materials, which can be a pioneering breakthrough in commercialization of Ni-rich cathodes.
P2-type Na0.67MnO2 with a stable structure and an open framework can provide numerous channels for fast Na+ de/intercalation, for which it is considered to be advantageous in application of the ...cathode material for Na-ion batteries. However, the complex phase transition occurring during cycling and the lattice distortion triggered by the Jahn–Teller effect severely restrict its development. Herein, the modified Na0.67MnO2 with Cu or Fe single-element doping as well as Cu and Fe double-element doping was synthesized by the sol–gel method, and the effects of doping on the crystal structure and electrochemical performances of Na0.67MnO2 were studied. It was demonstrated that the phase of the material did not change after the introduction of Cu and Fe elements, and the cycling stability and rate performance were greatly improved by Cu and Fe double-doping owing to their synergistic effect. The Na0.67Mn0.92Fe0.04Cu0.04O2 (NMFCO) cathode delivers discharge specific capacities of 110.5 mA h g–1 at 5 C and 91.8 mA h g–1 at 10 C and exhibits the high-capacity retention of 94.35% at 1 C and 90.68% at 5 C after 100 cycles. Overall, this study offers a guiding direction for accelerating the modification of P2-type Na0.67MnO2 as a cathode active material for high performance Na-ion batteries.
LiMn2O4 (LMO) has established its own niche in the highly competitive market of cathode materials. However, issues such as oxygen evolution, manganese dissolution, and electrolyte decomposition have ...hampered its further development. To address these challenges, a simple and effective strategy has been proposed, which involves incorporating WO2.72 as an oxygen vacancy inducer into LMO to enhance its structural stability. It is demonstrated that WO2.72 can induce the formation of oxygen vacancies on the material surface, which aids in the adsorption and storage of active oxygen. The vacancies also reduce the energy barrier for the migration of lithium ions, thus improving the electrochemical performance of the battery. Additionally, the formation of a Li2WO4 coating helps to eliminate residual lithium and improve the interface between the electrode and electrolyte. Accordingly, the WO2.72-modified LMO exhibits a more stable bulk structure and a better electrode-electrolyte contact interface, resulting in superior electrochemical performance. The optimized W4000 sample demonstrates outstanding cycle performance, with a capacity retention of 90.4% after 300 cycles at 10 C, which is significantly higher than that of bare LMO (68.9%).
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•WO2.72 was introduced as the oxygen vacancy inducer.•Oxygen vacancies facilitate the adsorption and storage of reactive oxygen species.•Oxygen vacancies improve the diffusion kinetics of lithium ions.•Li2WO4 coating formed on the LMO surface.•Improving the high-temperature electrochemical performance of LMO.
In this paper, a green, efficient and low-cost process for the selective recovery of lithium from spent LiFePO
by anodic electrolysis is proposed. The leaching rates of Li, Fe and P under different ...conditions were explored and the optimal conditions are obtained. In the optimal conditions, Li, Fe and P leaching rates were 96.31%, 0.06% and 0.62% respectively. The Li/Fe selectivity was over 99.9%. The product obtained is isostructural FePO
and retains the original particle morphology. The FePO
obtained can be synthesised into LiFePO
/C by direct regeneration process or impurity removal regeneration process. The material synthesized by the latter process has a better electrochemical performance, with a discharge specific capacity of 144.5 mAh/g at 1.0C and a capacity retention of 92.0% over 500cycles. The superior performance can be attributed to an impurity removal process that reduced agglomeration and improved particle morphology.
Ni-rich transition metal layered oxides as one of the most promising cathodes for Li-ion batteries possess discernible advantages such as high energy density and discharge capacity. Despite their ...superiority, Ni-rich cathodes suffer from severe microcracks within the secondary particles, particularly when the nickel content exceeds 80%, which causes liquid electrolyte penetrates the interior of secondary particles and reacts with more active materials, leading to rapid degradation of cell performance. Therefore, increasing researches focus on understanding the causes of microcracks generation and overcoming particle cracking. Herein, the intrinsic origins of microcracks in Ni-rich cathodes, together with effective modification strategies for suppressing the nucleation and propagation of microcracks are reviewed.
•The in-depth understanding of microcrack generation is established.•Modification strategies of Ni-rich cathode for enabling structural stability.•Perspectives toward designing the crack-free Ni-rich cathode are provided.
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ZrO2 in different crystal states were coated on the surface of the Li-Rich Mn-based materials to analyze their difference in electrochemical performance improvement.
Li-rich oxides ...are considered as the most commercial potential cathode materials due to the high theoretical specific discharge capacity. Here, ZrO2 in different crystalline states are applied as the coating layers to enhance the electrochemical performance of hollow LiLi0.2Mn0.54Ni0.13Co0.13O2 materials. Meanwhile, a series of characterizations (XRD, SEM, TEM, EDX etc.) are conducted to compare the effects of ZrO2 coating layer with different crystalline states on the host material. The results elucidate that the Li-rich Mn-based material with the polycrystal ZrO2 coating layer has a slight advantage in rate performance, while the host material with the single crystal ZrO2-coating layer has a better cycling performance and effectively suppresses voltage decay with the effect of excellently inhibiting layered to spinel-like phase transition and metal dissolution during charging and discharging process.
Naturally-fermented mixed fruit products are popular in Asia for their abundant nutrition, potential antioxidant activity, and hypoglycemic activity. In this work, the changes in chemical composition ...(including pH, titratable acid, total and reducing sugar, total soluble solids, protein content, total phenols, and organic acids) and preliminary in vitro bioactivities (including ABTS radical scavenging activity, DPPH radical scavenging activity, α-amylase, and α-glucosidase inhibition) of naturally-fermented mixed fruit products during a 120-day fermentation period and their correlations were investigated. Results showed that a variety of organic acids changed dramatically, such that lactic acid content raised from 0 mg/mL at 0 day to 9.11 mg/mL at 60 days; and citric acid content raised from 3.38 mg/mL at 0 day to 6.52 mg/mL at 90 days. Correlation analysis indicated that total phenols, citric acid, lactic acid, and titratable acid were the key factors influencing the continuous increase of ABTS, DPPH radical scavenging, and α-amylase inhibition during fermentation. In general, natural fermentation provides a great increase in the nutritional potential and functional value of the fruit and the results of this study provide evidence for the scientific guide in the industrial production of fermented fruit.
•Lactic acid and citric acid continued to rise in the first 60 days of fermentation.•Functional activity is enhanced by the presence of phenols and organic acids.•Natural fermentation increases the functional value of the fruits considerably.
Li-rich cathode materials have higher discharge capacity and lower cost than conventional electrode materials such as LiCoO2. However, they suffer from rapid capacity fading caused by irreversible ...phase transition and interfacial instability during the electrochemical cycling. La–Co–O (denoted as LC) compound possess good electronic conductivity and superior thermal stability, which could be used as a promising coating layer to suppress Mn dissolution as well as to facilitate electrical transfer. Furthermore, La–Co–O (LC) coating layer could decrease the Mn3+ ions on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 (denoted as LMNC), thus stabilize the surface structure. Herein, we present La–Co–O (LC) coating layer on the surface of LMNC via an artful sol-gel-based method with a thickness below 50 nm. XPS, EDS and TEM tests were applied to confirm the existence of LC coating layer. 2 mol% LC coated LMNC sample shows much improved cycle stability at 1C (206.3 mAh g−1, 86.2% capacity retention after 100 cycles) and good rate capability especially at high rates. In addition, LC coating could effectively suppress voltage fading of LMNC. EIS results reveal that the LC modified LMNC materials exhibit better electrochemical kinetics than the pristine one.
