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1.
Classical layered transition metal oxides have remained the preferred cathode materials for commercial lithium-ion batteries. Variation in the transition metal composition and local ordering can greatly affect the structure stability. In classical layered cathodes, high concentrations of electrochemically inert Mn elements usually act as a pillar to stabilize the structure. When excess amount of Li and Mn are present in the layered structure, the capacity of the Li-rich layered oxide (molar ratio of lithium over transition metal is larger than one by design) can exceed that expected from transition metal redox. However, the over lithiation in the classical layered structure results in safety issues, which remains challenging for the commercialization of Li-rich layered oxides. To characterize the safety performance of a series of Li-rich layered cathodes, we utilize differential scanning calorimeter and thermal gravimetric analysis; this is coupled with local structural changes using in situ temperature dependent synchrotron X-ray diffraction and X-ray adsorption spectroscopy. These methods demonstrate that the gradual decrease of the Mn–M (M = Ni, Co, Mn and Li) coordination number directly reduces structural stability and accelerates oxygen release. For safety characterization tests in practice, we evaluate the thermal runaway process through accelerating rate calorimeter in 1.0 Ah pouch cells to confirm this trend. Using the insights obtained in this work, we design a polymorphic composition to improve the thermal stability of Li-rich layered cathode material, which outperforms Ni-rich layered oxides in terms of both electrochemical and safety performances. 相似文献
2.
Bo Cao Tianyi Li Wenguang Zhao Liang Yin Hongbin Cao Dong Chen Luxi Li Feng Pan Mingjian Zhang 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(42):2301834
Understanding the mechanism of the rate-dependent electrochemical performance degradation in cathodes is crucial to developing fast charging/discharging cathodes for Li-ion batteries. Here, taking Li-rich layered oxide Li1.2Ni0.13Co0.13Mn0.54O2 as the model cathode, the mechanisms of performance degradation at low and high rates are comparatively investigated from two aspects, the transition metal (TM) dissolution and the structure change. Quantitative analyses combining spatial-resolved synchrotron X-ray fluorescence (XRF) imaging, synchrotron X–ray diffraction (XRD) and transmission electron microscopy (TEM) techniques reveal that low-rate cycling leads to gradient TM dissolution and severe bulk structure degradation within the individual secondary particles, and especially the latter causes lots of microcracks within secondary particles, and becomes the main reason for the fast capacity and voltage decay. In contrast, high-rate cycling leads to more TM dissolution than low-rate cycling, which concentrates at the particle surface and directly induces the more severe surface structure degradation to the electrochemically inactive rock-salt phase, eventually causing a faster capacity and voltage decay than low-rate cycling. These findings highlight the protection of the surface structure for developing fast charging/discharging cathodes for Li-ion batteries. 相似文献
3.
Polyanion-Type Na3V2(PO4)2F3@rGO with High-Voltage and Ultralong-Life for Aqueous Zinc Ion Batteries
Jieduo Guan Qiaofeng Huang Lianyi Shao Xiaoyan Shi DongDong Zhao Liubin Wang Zhipeng Sun 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(15):2207148
Aqueous zinc ion batteries (AZIBs) have attracted much interest in the next generation of energy storage devices because of their elevated safety and inexpensive price. Polyanionic materials have been considered as underlying cathodes owing to the high voltage, large ionic channels and fast ionic kinetics. However, the low electronic conductivity limits their cycling stability and rate performance. Herein, mesoporous Na3V2(PO4)2F3 (N3VPF) nanocuboids with the size of 80–220 nm cladded by reduced graphene oxide (rGO) have been successfully prepared to form 3D composite (N3VPF@rGO) by a novel and fast microwave hydrothermal with subsequent calcination strategy. The enhanced conductivity, strengthened pseudocapacitive behaviors, enlarged DZn2+, and stable structure guarantee N3VPF@rGO with splendid Zn2+ storage performance, such as high capacity of 126.9 mAh g-1 at 0.5 C (1 C = 128 mA g-1), high redox potentials at 1.48/1.57 V, high rate capacity of 93.9 mAh g-1 at 20 C (short charging time of 3 mins) and extreme cycling stability with capacity decay of 0.0074% per cycle after 5000 cycles at 15 C. The soft package batteries also present preeminent performance, demonstrating the practical application values. In situ X-ray diffraction, ex situ transmission electron microscopy and X-ray photoelectron spectroscopy reveal a reversible Zn2+ insertion/extraction mechanism. 相似文献
4.
采用高温固相合成法制备富锂锰基正极材料Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54-x)Zn_xO_2(x=0,0.03,0.06,0.10),Zn~(2+)掺杂对Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2的表面特性和电化学性能都有影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼光谱分析、充放电测试、倍率特性测试、循环性能测试,分析了该合成材料的晶体结构、形貌特征、微观结构和电化学性能。富锂锰基正极材料为a-NaFeO_2层状结构,R-3m空间群,结晶度高,结构稳定性好,其中Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.48)Zn_(0.06)O_2的电化学性能较好。掺杂Zn~(2+)可以提高富锂锰基正极材料的充放电比容量、倍率性能、循环性能等电化学性能。 相似文献
5.
Dongchang Chen Jinpeng Wu Joseph K. Papp Bryan D. McCloskey Wanli Yang Guoying Chen 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(22)
Owing to the capacity boost from oxygen redox activities, Li‐rich cation‐disordered rocksalts (LRCDRS) represent a new class of promising high‐energy Li‐ion battery cathode materials. Redox‐inactive transition‐metal (TM) cations, typically d0 TM, are essential in the formation of rocksalt phases, however, their role in electrochemical performance and cathode stability is largely unknown. In the present study, the effect of two d0 TM (Nb5+ and Ti4+) is systematically compared on the redox chemistry of Mn‐based model LRCDRS cathodes, namely Li1.3Nb0.3Mn0.4O2 (LNMO), Li1.25Nb0.15Ti0.2Mn0.4O2 (LNTMO), and Li1.2Ti0.4Mn0.4O2 (LTMO). Although electrochemically inactive, d0 TM serves as a modulator for oxygen redox, with Nb5+ significantly enhancing initial charge storage contribution from oxygen redox. Further studies using differential electrochemical mass spectroscopy and resonant inelastic X‐ray scattering reveal that Ti4+ is better in stabilizing the oxidized oxygen anions (On?, 0 < n < 2), leading to a more reversible O redox process with less oxygen gas release. As a result, much improved chemical, structural and cycling stabilities are achieved on LTMO. Detailed evaluation on the effect of d0 TM on degradation mechanism further suggests that proper design of redox‐inactive TM cations provides an important avenue to balanced capacity and stability in this newer class of cathode materials. 相似文献
6.
Xiang Li Yu Qiao Shaohua Guo Kezhu Jiang Masayoshi Ishida Haoshen Zhou 《Advanced materials (Deerfield Beach, Fla.)》2019,31(11)
Li‐rich oxide cathodes are of prime importance for the development of high‐energy lithium‐ion batteries (LIBs). Li‐rich layered oxides, however, always undergo irreversible structural evolution, leading to inevitable capacity and voltage decay during cycling. Meanwhile, Li‐rich cation‐disordered rock‐salt oxides usually exhibit sluggish kinetics and inferior cycling stability, despite their firm structure and stable voltage output. Herein, a new Li‐rich rock‐salt oxide Li2Ni1/3Ru2/3O3 with Fd‐3m space group, where partial cation‐ordering arrangement exists in cationic sites, is reported. Results demonstrate that a cathode fabricated from Li2Ni1/3Ru2/3O3 delivers a large capacity, outstanding rate capability as well as good cycling performance with negligible voltage decay, in contrast to the common cations disordered oxides with space group Fm‐3m. First principle calculations also indicate that rock‐salt oxide with space group Fd‐3m possesses oxygen activity potential at the state of delithiation, and good kinetics with more 0‐TM (TM = transition metals) percolation networks. In situ Raman results confirm the reversible anionic redox chemistry, confirming O2?/O? evolution during cycles in Li‐rich rock‐salt cathode for the first time. These findings open up the opportunity to design high‐performance oxide cathodes and promote the development of high‐energy LIBs. 相似文献
7.
Yingying Mi Wen Liu Xiaolin Li Julia Zhuang Henghui Zhou Hailiang Wang 《Nano Research》2017,(11):3698-3705
Despite promising characteristics such as high specific energy and low cost,current Li-S batteries fall short in cycle life.Improving the cycling stability of S cathodes requires immobilizing the lithium polysulfide (LPS) intermediates as well as accelerating their redox kinetics.Although many materials have been explored for trapping LPS,the ability to promote LPS redox has attracted much less attention.Here,we report for the first time on transition metal phosphides as effective host materials to enhance both LPS adsorption and redox.Integrating MoP-nanoparticle-decorated carbon nanotubes with S deposited on graphene oxide,we enable Li-S battery cathodes with substantially improved cycling stability and rate capability.Capacity decay rates as low as 0.017% per cycle over 1,000 cycles can be realized.Stable and high areal capacity (> 3 mAh·cm-2) can be achieved under high mass loading conditions.Comparable electrochemical performance can also be achieved with analogous material structures based on CoP,demonstrating the potential of metal phosphides for long-cycle Li-S batteries. 相似文献
8.
Nitin Muralidharan Rachid Essehli Raphael P. Hermann Ruhul Amin Charl Jafta Junjie Zhang Jue Liu Zhijia Du Harry M. Meyer III Ethan Self Jagjit Nanda Ilias Belharouak 《Advanced materials (Deerfield Beach, Fla.)》2020,32(34):2002960
In recent years, cobalt has become a critical constraint on the supply chain of the Li-ion battery industry. With the ever-increasing projections for electric vehicles, the dependency of current Li-ion batteries on the ever-fluctuating cobalt prices poses serious environmental and sustainability issues. To address these challenges, a new class of cobalt-free materials with general formula of LiNixFeyAlzO2 (x + y + z = 1), termed as the lithium iron aluminum nickelate (NFA) class of cathodes, is introduced. These cobalt-free materials are synthesized using the sol–gel process to explore their compositional landscape by varying aluminum and iron. These NFA variants are characterized using electron microscopy, neutron and X-ray diffraction, and Mössbauer and X-ray photoelectron spectroscopy to investigate their morphological, physical, and crystal-structure properties. Operando experiments by X-ray diffraction, Mössbauer spectroscopy, and galvanostatic intermittent titration have been also used to study the crystallographic transitions, electrochemical activity, and Li-ion diffusivity upon lithium removal and uptake in the NFA cathodes. NFA compositions yield specific capacities of ≈200 mAh g−1, demonstrating reasonable rate capability and cycling stability with ≈80% capacity retention after 100 charge/discharge cycles. While this is an early stage of research, the potential that these cathodes could have as viable candidates in next-generation cobalt-free lithium-ion batteries is highlighted here. 相似文献
9.
Synthetic Control of Kinetic Reaction Pathway and Cationic Ordering in High‐Ni Layered Oxide Cathodes
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Dawei Wang Ronghui Kou Yang Ren Cheng‐Jun Sun Hu Zhao Ming‐Jian Zhang Yan Li Ashifia Huq J. Y. Peter Ko Feng Pan Yang‐Kook Sun Yong Yang Khalil Amine Jianming Bai Zonghai Chen Feng Wang 《Advanced materials (Deerfield Beach, Fla.)》2017,29(39)
Nickel‐rich layered transition metal oxides, LiNi1?x (MnCo)x O2 (1?x ≥ 0.5), are appealing candidates for cathodes in next‐generation lithium‐ion batteries (LIBs) for electric vehicles and other large‐scale applications, due to their high capacity and low cost. However, synthetic control of the structural ordering in such a complex quaternary system has been a great challenge, especially in the presence of high Ni content. Herein, synthesis reactions for preparing layered LiNi0.7Mn0.15Co0.15O2 (NMC71515) by solid‐state methods are investigated through a combination of time‐resolved in situ high‐energy X‐ray diffraction and absorption spectroscopy measurements. The real‐time observation reveals a strong temperature dependence of the kinetics of cationic ordering in NMC71515 as a result of thermal‐driven oxidation of transition metals and lithium/oxygen loss that concomitantly occur during heat treatment. Through synthetic control of the kinetic reaction pathway, a layered NMC71515 with low cationic disordering and a high reversible capacity is prepared in air. The findings may help to pave the way for designing high‐Ni layered oxide cathodes for LIBs. 相似文献
10.
Choudhury A Bhowmick AK Ong C Soddemann M 《Journal of nanoscience and nanotechnology》2010,10(8):5056-5071
Structure of nanofillers and their subsequent interaction with a polymer is very important in determining thermal stability of polymer nanocomposite. In this paper, we tried to correlate structure of various 0, 1 and 2 dimensional nanofillers with the thermal stability of hydrogenated nitrile butadiene rubber (HNBR) nanocomposites. Organically modified and unmodified layered silicates such as montmorillonite (Cloisite Na+, Cloisite 30B and Cloisite 15A), rod-like fibrous filler (sepiolite) and spherical nanoparticles (nanosilica) were chosen for this purpose. A significant improvement in thermal stability (obtained by thermogravimeric analysis and differential scanning calorimetry) was observed for silica-filled nanocomposites. However, the activation energy of the nanocomposites calculated by different kinetic methods (both non-isothermal and isothermal methods) was found to be significantly high for sepiolite, 30B and silica-filled nanocomposites. The results were explained with the help of structure of the nanofillers, their interaction with the elastomer and the subsequent dispersion, as measured by X-ray diffraction, transmission electron microscopy and atomic force microscopy. From these analyses it was concluded that organically modified montmorillonite, sepiolite and nanosilica increase the thermal stability of the nanocomposite to a great extent due to the interaction of the reactive groups on the surface of these fillers with the polymer and high thermal stability of these inorganic fillers. Finally, degradation mechanism of HNBR in presence of the nanofillers at severe operating temperatures was investigated with the help of FTIR spectroscopy. 相似文献
11.
Bin-Wei Zhang Liuyue Cao Cheng Tang Chunhui Tan Ningyan Cheng Wei-Hong Lai Yun-Xiao Wang Zhen-Xiang Cheng Juncai Dong Yuan Kong Shi-Xue Dou Shenlong Zhao 《Advanced materials (Deerfield Beach, Fla.)》2023,35(1):2206828
Room-temperature sodium–sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS2 and Mo1 (S@MoS2-Mo1/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS2-Mo1/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g−1 at 0.1 A g−1 and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level. 相似文献
12.
In this study, polypyrrole (PPy) thin films were electrodeposited on carbon nanotube (CNT) backbones by applying a constant deposition potential in 0.1 M pyrrole solution with different electrolytes, such as NaCl, NaNO3, or NaClO4. The hybrid films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, and cyclic voltammetry. SEM images revealed the nanostructrure of PPy films generated on CNT surface. The electrochemical and anion exchange properties of the PPy-CNT composite films have been investigated. Nanostructured composite thin films of PPy-CNTs were studied by cyclic voltammetry between 0.4 and -0.8 V in aqueous solution to evaluate their cycling stability and capacity for electrically switched anion exchange. The presence of the CNT backbone greatly improved the anion exchange capacity and stability of the PPy-CNT composite film, which may be attributed to the high surface area of CNT matrix, nanostructure of the PPy film, and the interaction between CNTs and PPy. 相似文献
13.
Exposing {010} Active Facets by Multiple‐Layer Oriented Stacking Nanosheets for High‐Performance Capacitive Sodium‐Ion Oxide Cathode
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Yao Xiao Peng‐Fei Wang Ya‐Xia Yin Yan‐Fang Zhu Yu‐Bin Niu Xu‐Dong Zhang Jienan Zhang Xiqian Yu Xiao‐Dong Guo Ben‐He Zhong Yu‐Guo Guo 《Advanced materials (Deerfield Beach, Fla.)》2018,30(40)
As one of the most promising cathodes for rechargeable sodium‐ion batteries (SIBs), O3‐type layered transition metal oxides commonly suffer from inevitably complicated phase transitions and sluggish kinetics. Here, a Na[Li0.05Ni0.3Mn0.5Cu0.1Mg0.05]O2 cathode material with the exposed {010} active facets by multiple‐layer oriented stacking nanosheets is presented. Owing to reasonable geometrical structure design and chemical substitution, the electrode delivers outstanding rate performance (71.8 mAh g?1 and 16.9 kW kg?1 at 50C), remarkable cycling stability (91.9% capacity retention after 600 cycles at 5C), and excellent compatibility with hard carbon anode. Based on the combined analyses of cyclic voltammograms, ex situ X‐ray absorption spectroscopy, and operando X‐ray diffraction, the reaction mechanisms behind the superior electrochemical performance are clearly articulated. Surprisingly, Ni2+/Ni3+ and Cu2+/Cu3+ redox couples are simultaneously involved in the charge compensation with a highly reversible O3–P3 phase transition during charge/discharge process and the Na+ storage is governed by a capacitive mechanism via quantitative kinetics analysis. This optimal bifunctional regulation strategy may offer new insights into the rational design of high‐performance cathode materials for SIBs. 相似文献
14.
球磨Mg0.97La0.03Ni合金的热稳定性及电性能研究 总被引:4,自引:1,他引:4
采用XRD、DTA、SEM及电池性能测试仪等对球磨Mg0.97La0.03Ni合金的结构、形貌、活化性能、热稳定性、电化学稳定性及容量衰减机理等进行了详细的研究。结果表明:样品的热稳定性及循环稳定性随着球磨时间的延长而增加。经400r/min球磨50h的样品在第二次活化时即达到最大值450mAh/g.经25次循环充放电后.该样品的容量与其最大值相比下降了53%.容量衰减的主要原因有:在循环充放电过程中.非晶体逐渐分解生成Mg2NiH4和Ni等晶体相,同时在颗粒表面形成腐蚀产物Mg(OH)2等。 相似文献
15.
《材料科学技术学报》2019,35(7):1479-1484
The thermal oxidation of ZrAl2 in the temperature range of 550–750 °C in pure oxygen has been investigated by a combinational experimental approach using X-ray diffraction, scanning electron microscopy/energy dispersive spectrometer, Auger electron spectroscopy and cross-sectional transmission electron microscopy. The thermal oxidation leads to the growth of anomalously thick (up to 4.5 μm) amorphous (Zr0.33Al0.67)O1.66 surficial layers at temperatures as high as 750 °C. The oxidation kinetics obeys a parabolic law with an activation energy of 143 kJ/mol. The underlying mechanism for the formation of such micrometer-thick amorphous oxide surficial layers has been discussed on the basis of interface thermodynamics and the occurrence of high interface stability associated with a synchronous oxidation of Al and Zr elements. 相似文献
16.
《Advanced Powder Technology》2021,32(8):2816-2827
This study systematically investigated the physicochemical characteristics of hexagonal boron nitride (h-BN) nanoparticles dispersed in polyalphaolefin 6 (PAO6) from a molecular level to explore the thermal stability of nano-lubricants. The nanoparticles were characterized via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and energy-dispersive spectrometry (EDS) to analyze the chemical bonds, element distribution, and impurity. We not only theoretically reveal the rheological behavior of nano-lubricants but also propose precise models to predict the viscosity. Moreover, this study comprehensively analyzed the thermal stability of nano-lubricants under different gas environments through thermogravimetric analysis and revealed that the nanofluid thermal stability was improved owing to the small-size effect. The results show that the thermal conductivity of the nano-lubricants was significantly higher than that of PAO6. Finally, the mechanism of thermal property enhancement by the h-BN nanoparticles is revealed. 相似文献
17.
The commercialization of lithium-sulfur batteries is hindered by low cycle stability and low efficiency, which are induced by sulfur active material loss and polysulfide shuttle reaction through dissolution into electrolyte. In this study, sulfur-impregnated disordered carbon nanotubes are synthesized as cathode material for the lithium-sulfur battery. The obtained sulfur-carbon tube cathodes demonstrate superior cyclability and Coulombic efficiency. More importantly, the electrochemical characterization indicates a new stabilization mechanism of sulfur in carbon induced by heat treatment. 相似文献
18.
Qingrong Huang Xiaodong Zhang Xiaowei Lv Xiaoqi Wang Wen Wen Feng Wu Renjie Chen Li Li 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(42):2302086
The comparatively poor endurance of Ni-rich cathode materials restricts their application in high-energy lithium-ion batteries. A thorough understanding of the degradation characteristics of such materials under complex electrochemical aging protocols is required to further improve their reliability. In this work, the irreversible capacity losses of LiNi0.8Mn0.1Co0.1O2 under different electrochemical aging protocols are quantitatively evaluated via a well-designed experiment. In addition, it is discovered that the origin of irreversible capacity losses is highly related to electrochemical cycling parameters and can be divided into two types. Type I is heterogeneous degradation caused by low C-rate or high upper cut-off voltage cycling and features abundant capacity loss during H2-H3 phase transition. Such capacity loss is attributed to the irreversible surface phase transition that limits the accessible state of charge during the H2-H3 phase transition stage via the pinning effect. Type II is fast charging/discharging induced homogeneous capacity loss that occurs consistently throughout the whole phase transition time. This degradation pathway shows a distinctive surface crystal structure, which is dominated by a bending layered structure rather than a typical rock-salt phase structure. This work offers detailed insight into the failure mechanism of Ni-rich cathodes and provides guidance on designing long-cycle life, high-reliability electrode materials. 相似文献
19.
Li‐Rich Li[Li1/6Fe1/6Ni1/6Mn1/2]O2 (LFNMO) Cathodes: Atomic Scale Insight on the Mechanisms of Cycling Decay and of the Improvement due to Cobalt Phosphate Surface Modification
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Xing Li Kangjia Zhang David Mitlin Eunsu Paek Mingshan Wang Fei Jiang Yun Huang Zhenzhong Yang Yue Gong Lin Gu Wengao Zhao Yingge Du Jianming Zheng 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(40)
Lithium‐rich Li[Li1/6Fe1/6Ni1/6Mn1/2]O2 (0.4Li2MnO3‐0.6LiFe1/3Ni1/3Mn1/3O2, LFNMO) is a new member of the xLi2MnO3·(1 ? x)LiMO2 family of high capacity–high voltage lithium‐ion battery (LIB) cathodes. Unfortunately, it suffers from the severe degradation during cycling both in terms of reversible capacity and operating voltage. Here, the corresponding degradation occurring in LFNMO at an atomic scale has been documented for the first time, using high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM), as well as tracing the elemental crossover to the Li metal anode using X‐ray photoelectron spectroscopy (XPS). It is also demonstrated that a cobalt phosphate surface treatment significantly boosts LFNMO cycling stability and rate capability. Due to cycling, the unmodified LFNMO undergoes extensive elemental dissolution (especially Mn) and O loss, forming Kirkendall‐type voids. The associated structural degradation is from the as‐synthesized R‐3m layered structure to a disordered rock‐salt phase. Prior to cycling, the cobalt phosphate coating is epitaxial, sharing the crystallography of the parent material. During cycling, a 2–3 nm thick disordered Co‐rich rock‐salt structure is formed as the outer shell, while the bulk material retains R‐3m crystallography. These combined cathode–anode findings significantly advance the microstructural design principles for next‐generation Li‐rich cathode materials and coatings. 相似文献
20.
Jian Zhang Yongchang Liu Xudong Zhao Lunhua He Hui Liu Yuzhu Song Shengdong Sun Qiang Li Xianran Xing Jun Chen 《Advanced materials (Deerfield Beach, Fla.)》2020,32(11):1906348
Sodium-ion batteries (SIBs) have attracted incremental attention as a promising candidate for grid-scale energy-storage applications. To meet practical requirements, searching for new cathode materials with high energy density is of great importance. Herein, a novel Na superionic conductor (NASICON)-type Na4MnCr(PO4)3 is developed as a high-energy cathode for SIBs. The Na4MnCr(PO4)3 nanoparticles homogeneously embedded in a carbon matrix can present an extraordinary reversible capacity of 160.5 mA h g−1 with three-electron reaction at ≈3.53 V during the Na+ extraction/insertion process, realizing an unprecedentedly high energy density of 566.5 Wh kg−1 in the phosphate cathodes for SIBs. It is intriguing to reveal the underlying mechanism of the unique Mn2+/Mn3+, Mn3+/Mn4+, and Cr3+/Cr4+ redox couples via X-ray absorption near-edge structure spectroscopy. The whole electrochemical reaction undergoes highly reversible single-phase and biphasic transitions with a moderate volume change of 7.7% through in situ X-ray diffraction and ex situ high-energy synchrotron X-ray diffraction. Combining density functional theory (DFT) calculations with the galvanostatic intermittent titration technique, the superior performance is ascribed to the low ionic-migration energy barrier and desirable Na-ion diffusion kinetics. The present work can offer a new insight into the design of multielectron-reaction cathode materials for SIBs. 相似文献