LiMn1‐yFeyPO4 (LMFP) is a significant and cost‐effective cathode material for Li‐ion batteries, with a higher working voltage than LiFePO4 (LFP) and improved safety features compared to layered oxide ...cathodes. However, its commercial application faces challenges due to a need for a synthesis process to overcome the low Li‐ion diffusion kinetics and complex phase transitions. Herein, a solid‐state synthesis process using LFP and nano LiMn0.7Fe0.3PO4 (MF73) is proposed. The larger LFP acts as a structural framework fused with nano‐MF73, preserving the morphology and high performance of LFP. These results demonstrate that the solid‐state reaction occurs quickly, even at a low sintering temperature of 500 °C, and completes at 700 °C. However, contrary to the expectations, the larger LFP particles disappeared and fused into the nano‐MF73 particles, revealing that Fe ions diffuse more easily than Mn ions in the olivine framework. This discovery provides valuable insights into understanding ion diffusion in LMFP. Notably, the obtained LMFP can still deliver an initial capacity of 142.3 mAh g−1, and the phase separation during the electrochemical process is significantly suppressed, resulting in good cycling stability (91.1% capacity retention after 300 cycles). These findings offer a promising approach for synthesizing LMFP with improved performance and stability.
LiMn1‐yFeyPO4 (LMFP) is a significant and cost‐effective cathode material for Li‐ion batteries. However, its commercial applicability is hindered by the lack of a suitable synthesis method to surmount the slow Li‐ion diffusion kinetics and complex phase transitions. Here, an LiFePO4 (LFP) and nano LiMn0.7Fe0.3PO4 (MF73) solid‐state synthesis procedure are proposed. These findings indicate that the solid‐state reaction takes place rapidly, even at a low sintering temperature of 500 °C, and is complete at 700 °C.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Lithium‐Ion Batteries
In article number 2309629, Yingqiang Wu, Li Wang, Fengli Bei, Xiangming He, and co‐workers present a LiMnxFe1‐xPO4 solid‐state synthesis method using LiFePO4 and nano ...LiMn0.7Fe0.3PO4 that coexist at room temperature, happen at low sintered temperatures (300–600 °C) and complete at high sintered temperatures (700∼800 °C). Following sintering at high temperatures, LiMnxFe1‐xPO4 achieved the uniform fusion of Mn and Fe ions. This discovery provides valuable insights into understanding ion diffusion in LiMnxFe1‐xPO4.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
To explore the effect of the addition of poly(vinylidene fluorine) (PVDF) to a nanothermite system, an Al/MnO2/PVDF energetic nanocomposite was prepared using an electrospray method, Al/MnO2 ...nanothermite was prepared as a control group. Then, the energetic nanocomposite and nanothermite were tested and analyzed by XRD, FE-SEM and TG-DSC, and the reaction products were collected. The results show that energetic nanocomposite would have three obvious exothermic peaks in the range of room temperature to 800 °C with a total more than 1700 J g−1 heat release while the control experiment, Al/MnO2 nanothermite, could be found one exothermic peak with a 1100 J g−1 heat release. The residues are mainly MnAl2O4, MnF2 and AlF3 which indicates that Al/MnO2/PVDF energetic nanocomposite could make full use of manganese oxide. Finally, thermal analysis experiments were carried out under different heating rates to calculate the activation energy. The calculation results show that the addition of PVDF could significantly reduce the activation energy, which would help spark the thermite at comparatively low energy and temperature.
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Among various cathode materials for lithium-ion batteries, xLi
2
MnO
3
⋅(1-x)LiMO
2
(M=Ni, Co, Mn) with layered structure has great potential due to its high specific capacity. In this work, LaPO
4
...-coated Li
1.2
Mn
0.54
Co
0.13
Ni
0.13
O
2
cathode material was successfully synthesized by wet chemical deposition method, and La doping was achieved by calcination. The results of SEM, TEM, and HRTEM showed that LaPO
4
is successfully coated on the surface of the material, La is successfully doped into the material, and the interlayer spacing of the material becomes larger after modification. The results of XRD and XPS also showed that La was successfully doped into the material. The electrochemical characterization results showed that LaPO
4
modification significantly improved the electrochemical performance of the material. Most importantly, the lithium-ion diffusion coefficient of 2 wt%-LaPO
4
is as high as 4.07 × 10
−14
cm
2
·s
−1
, which is four times that of the pristine material. Its specific capacity at 10 C is 100.3 mAh·g
−1
, which is about 90% higher than that of the unmodified material 52.8 mAh·g
−1
. The LaPO
4
-modified lithium-rich manganese-based cathode material has such good rate performance, which is attributed to the triple effect of LaPO
4
modification on promoting lithium-ion diffusion, which promotes the diffusion of lithium ion in three stages, from bulk phase to interface and then to electrolyte. The schematic can be seen in the graphical abstract.
Graphical abstract
LaPO
4
coating and La
3+
doping schematic diagram
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To explore the effect of potassium perchlorate (KClO4) on Al nanoparticles/MnO2-nanorods nanothermite systems, in this paper, Al/MnO2 nanothermites with different mass fraction of KClO4 were prepared ...by electrospray. The samples were characterized by XRD, SEM, TG-DSC analysis. According to the results of TG-DSC, the addition of KClO4 seemed to cause no direct improvement on their exothermic reactions. But the results of activation energy calculations showed that KClO4 could remarkably reduce the activation energy of nanothermite systems by up to 48.8%. The XRD results indicated that residues consisted mainly of Mn3O4. The reasons why KClO4 has little effect on thermal properties but makes a great difference on kinetics were analyzed and discussed. Finally, onset combustion tests were carried out. The results and findings provide a useful approach to decrease the activation energy and combustion rate of nanothermites, which may facilitate practical and combustible applications.
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The freestanding Sb2S3 films were easily synthesized at the interface of water and toluene at room temperature, where Na2S and (C2H5OCS2)3Sb (xanthate, O-ethyldithiocarbonate) acted as sulfur and ...antimony source, respectively. After 3 h of aging, the Sb2S3 films with a flat surface toward organic side and rough surface toward aqueous side were assembled by sheaflike Sb2S3 nanowires. The Sb2S3 nanorings formed by end-to-end connection of the bundled nanowires appeared in the water layer when the reaction time reached 24 h. The Sb2S3 nanorings showed higher photocatalytic activity for methyl orange degradation under visible light than the Sb2S3 films owing to broader spectrum response and better aqueous dispersion.
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A complete mechanistic study on the nucleation of polymeric nanoparticles covering the generation of the clusters and the forthcoming aggregation to the nuclei is performed by in situ 1H nuclear ...magnetic resonance (NMR) experiments using polyaniline as an example. An aniline tetramer and a monomer-stabilized nitrenium are proved to be the basic cluster and predominant propagating intermediate in the nucleation. It is observed that the nuclei are generated via a sequential mechanism involving a translocation of the protonated tetramers to the aqueous bulk, dissociation of sodium dodecyl sulfate (SDS) micelles, and deprotonation to induce the fusion of the dissociated micelles and intermolecular packing of the oligomers. Despite its importance, direct observation of the nucleation is challenging. This work emphasizes the importance of utilizing the solvent in solvation shell as the sensitive probe to explore the most transient process in nucleation, demonstrating its efficiency in achieving information such as the stepwise procedures, the nuclei sizes, the growth kinetics, and so forth. The approach reported herein may prove of great value in establishing the missing link of the atomic origin of nanoparticles, a key topic toward the preparation of functional nanostructures with well-controlled architectures, and can be readily extended to the study of other organic or inorganic systems.
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In this study, reduced graphene oxide (RGO) coated Li1.2Mn0.54Co0.13Ni0.13O2 (RGO@LMNCO) materials with different amounts of RGO were synthesized using a facile hydrothermal method. The double ...electron layer on the graphene surface was opened by adding a certain amount of electrolyte（NaCl）to the solution to increase the activity of the graphene, thus contributing to the uniform dispersion of the nano-cathode material on the RGO and reducing the secondary agglomeration. The physical characterization and electrochemical test results confirmed that LMNCO material with 2 wt% RGO (2 wt%RGO@LMNCO) was most uniformly dispersed on RGO and exhibited the optimal overall electrochemical performance. The above result suggested that this strategy can be more conductive to exerting the superiority of RGO coating. RGO coating enhanced electronic and ionic conductivity while modifying the potential energy surface of LMNCO effectively and suppressing surface oxygen loss. Subsequently, it can be beneficial to avoid side reactions between the cathode material surface and the electrolyte. As a result, the surface stability of cathode materials was increased. The 2 wt%RGO@LMNCO electrode exhibited a maximum capacity of 308.7mAh g−1 at 0.2 C. With the increase of the charge/discharge current rate from 0.2 C to 10 C, it still reached 112.3mAh g−1. After 50 cycles at 0.2 C rate, the discharge capacity was decreased from 287.5 to 284.8 mAh·g−1, thus maintaining a capacity retention of 99.06%. Furthermore, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to analyze the synthesized sample. The main reason for enhanced electrochemical performance is that the RGO-LMNCO synthesized by the novel coating strategy, which can more effectively exert the modulation effect of graphene on the cathode material surface, exhibits better dispersion and uniform coating.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The rate performance of lithium iron phosphate (LiFePO4) is mainly limited by its poor electronic conductivity and slow Li-ion diffusion rate. Graphene-based materials are often compounded with ...LiFePO4 (LFP) to improve their rate performance, mainly because of their excellent electrical conductivity. Unlike most past composite work focusing on the conductive network between LFP and graphene, in this work, we further developed the functionality of graphene-based materials as nanoparticle carriers, where the nitrogen-doping strategy endows graphene with properties that make it an efficient structural regulation platform during the solvothermal process. Compared to reduced graphene oxide, not only does the nitrogen-doped sites confer more nucleation growth sites for LFP on the graphene surface during the solvothermal process, but also the localized formation of an EG-enriched microenvironment helps to further inhibit the in situ growth of LFP along 010. The efficient structural regulation platform assisted the synthesis of (010)-oriented LFP with a smaller particle size, which further shortens the Li-ion diffusion paths. The optimized LFP composite electrode materials exhibit a discharge-specific capacity of 133.1 mA·h/g at 10C, which exceeds/is comparable to that of previously reported LFP compounded with graphene-based materials. This work broadens the functionality of graphene-based carriers and provides new ideas for the controllable synthesis of nanoparticles.
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The rate performance of lithium iron phosphate (LiFePO
) is mainly limited by its poor electronic conductivity and slow Li-ion diffusion rate. Graphene-based materials are often compounded with ...LiFePO
(LFP) to improve their rate performance, mainly because of their excellent electrical conductivity. Unlike most past composite work focusing on the conductive network between LFP and graphene, in this work, we further developed the functionality of graphene-based materials as nanoparticle carriers, where the nitrogen-doping strategy endows graphene with properties that make it an efficient structural regulation platform during the solvothermal process. Compared to reduced graphene oxide, not only does the nitrogen-doped sites confer more nucleation growth sites for LFP on the graphene surface during the solvothermal process, but also the localized formation of an EG-enriched microenvironment helps to further inhibit the in situ growth of LFP along 010. The efficient structural regulation platform assisted the synthesis of (010)-oriented LFP with a smaller particle size, which further shortens the Li-ion diffusion paths. The optimized LFP composite electrode materials exhibit a discharge-specific capacity of 133.1 mA·h/g at 10C, which exceeds/is comparable to that of previously reported LFP compounded with graphene-based materials. This work broadens the functionality of graphene-based carriers and provides new ideas for the controllable synthesis of nanoparticles.
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IJS, KILJ, NUK, PNG, UL, UM
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