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1.
Tokio Kobayashi Wenwen Zhao Hongahally Basappa Rajendra Keisuke Yamanaka Toshiaki Ohta Naoaki Yabuuchi 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(12)
To realize the development of rechargeable sodium batteries, new positive electrode materials without less abundant elements are explored. Enrichment of sodium contents in host structures is required to increase the theoretical capacity as electrode materials, and therefore Na‐excess compounds are systematically examined in a binary system of Na2TiO3–NaMnO2. After several trials, synthesis of Na‐excess compounds with a cation disordered rocksalt structure is successful by adapting a mechanical milling method. Among the tested electrode materials, Na1.14Mn0.57Ti0.29O2 in this binary system delivers a large reversible capacity of ≈200 mA h g?1, originating from reversible redox reactions of cationic Mn3+/Mn4+ and anionic O2?/On? redox confirmed by X‐ray absorption spectroscopy. Holes in oxygen 2p orbitals, which are formed by electrochemical oxidation, are energetically stabilized by electron donation from Mn ions. Moreover, reversibility of anionic redox is significantly improved compared with a former study on a binary system of Na3NbO3–NaMnO2 tested as model electrode materials. 相似文献
2.
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
3.
Jun Yang Manjing Tang Hao Liu Xueying Chen Zhanwei Xu Jianfeng Huang Qingmei Su Yongyao Xia 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(52)
Inspired by its high‐active and open layered framework for fast Li+ extraction/insertion reactions, layered Ni‐rich oxide is proposed as an outstanding Na‐intercalated cathode for high‐performance sodium‐ion batteries. An O3‐type Na0.75Ni0.82Co0.12Mn0.06O2 is achieved through a facile electrochemical ion‐exchange strategy in which Li+ ions are first extracted from the LiNi0.82Co0.12Mn0.06O2 cathode and Na+ ions are then inserted into a layered oxide framework. Furthermore, the reaction mechanism of layered Ni‐rich oxide during Na+ extraction/insertion is investigated in detail by combining ex situ X‐ray diffraction, X‐ray photoelectron spectroscopy, and electron energy loss spectroscopy. As an excellent cathode for Na‐ion batteries, O3‐type Na0.75Ni0.82Co0.12Mn0.06O2 delivers a high reversible capacity of 171 mAh g?1 and a remarkably stable discharge voltage of 2.8 V during long‐term cycling. In addition, the fast Na+ transport in the cathode enables high rate capability with 89 mAh g?1 at 9 C. The as‐prepared Ni‐rich oxide cathode is expected to significantly break through the limited performance of current sodium‐ion batteries. 相似文献
4.
Wei Zhang Huangxu Li Zhian Zhang Ming Xu Yanqing Lai Shu‐Lei Chou 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
Developing high‐voltage cathode materials is critical for sodium‐ion batteries to boost energy density. NASICON (Na super‐ionic conductor)‐structured NaxMnM(PO4)3 materials (M represents transition metal) have drawn increasing attention due to their features of robust crystal framework, low cost, as well as high voltage based on Mn4+/Mn3+ and Mn3+/Mn2+ redox couples. However, full activation of Mn4+/Mn3+ redox couple within NASICON framework is still a great challenge. Herein, a novel NASICON‐type Na4MnCr(PO4)3 material with highly reversible Mn4+/Mn3+ redox reaction is discovered. It proceeds a two‐step reaction with voltage platforms centered at 4.15 and 3.52 V versus Na+/Na, delivering a capacity of 108.4 mA h g?1. The Na4MnCr(PO4)3 cathode also exhibits long durability over 500 cycles and impressive rate capability up to 10 C. The galvanostatic intermittent titration technique (GITT) test shows fast Na diffusivity which is further verified by density functional theory calculations. The high electrochemical activity derives from the 3D robust framework structure, fast kinetics, and pseudocapacitive contribution. The sodium storage mechanism of the Na4MnCr(PO4)3 cathode is deeply studied by ex situ X‐ray diffraction (XRD) and ex situ X‐ray photoelectron spectroscopy (XPS), revealing that both solid‐solution and two‐phase reactions are involved in the Na+ ions extraction/insertion process. 相似文献
5.
Xiang Li Yu Qiao Shaohua Guo Zhenming Xu Hong Zhu Xiaoyu Zhang Yang Yuan Ping He Masayoshi Ishida Haoshen Zhou 《Advanced materials (Deerfield Beach, Fla.)》2018,30(14)
Conventional cathodes of Li‐ion batteries mainly operate through an insertion–extraction process involving transition metal redox. These cathodes will not be able to meet the increasing requirements until lithium‐rich layered oxides emerge with beyond‐capacity performance. Nevertheless, in‐depth understanding of the evolution of crystal and excess capacity delivered by Li‐rich layered oxides is insufficient. Herein, various in situ technologies such as X‐ray diffraction and Raman spectroscopy are employed for a typical material Li1.2Ni0.2Mn0.6O2, directly visualizing O?? O? (peroxo oxygen dimers) bonding mostly along the c‐axis and demonstrating the reversible O2?/O? redox process. Additionally, the formation of the peroxo O? O bond is calculated via density functional theory, and the corresponding O? O bond length of ≈1.3 Å matches well with the in situ Raman results. These findings enrich the oxygen chemistry in layered oxides and open opportunities to design high‐performance positive electrodes for lithium‐ion batteries. 相似文献
6.
Rational Design of Na(Li1/3Mn2/3)O2 Operated by Anionic Redox Reactions for Advanced Sodium‐Ion Batteries
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In an effort to develop high‐energy‐density cathodes for sodium‐ion batteries (SIBs), low‐cost, high capacity Na(Li1/3Mn2/3)O2 is discovered, which utilizes the labile O 2p‐electron for charge compensation during the intercalation process, inspired by Li2MnO3 redox reactions. Na(Li1/3Mn2/3)O2 is systematically designed by first‐principles calculations considering the Li/Na mixing enthalpy based on the site preference of Na in the Li sites of Li2MnO3. Using the anionic redox reaction (O2?/O?), this Mn‐oxide is predicted to show high redox potentials (≈4.2 V vs Na/Na+) with high charge capacity (190 mAh g?1). Predicted cathode performance is validated by experimental synthesis, characterization, and cyclic performance studies. Through a fundamental understanding of the redox reaction mechanism in Li2MnO3, Na(Li1/3Mn2/3)O2 is designed as an example of a new class of promising cathode materials, Na(Li1/3M2/3)O2 (M: transition metals featuring stabilized M4+), for further advances in SIBs. 相似文献
7.
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
8.
Ti‐Substituted NaNi0.5Mn0.5‐xTixO2 Cathodes with Reversible O3−P3 Phase Transition for High‐Performance Sodium‐Ion Batteries
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Peng‐Fei Wang Hu‐Rong Yao Xin‐Yu Liu Jie‐Nan Zhang Lin Gu Xi‐Qian Yu Ya‐Xia Yin Yu‐Guo Guo 《Advanced materials (Deerfield Beach, Fla.)》2017,29(19)
Sodium‐ion batteries (SIBs) have been considered as potential candidates for stationary energy storage because of the low cost and wide availability of Na sources. O3‐type layered oxides have been considered as one of the most promising cathodes for SIBs. However, they commonly show inevitable complicated phase transitions and sluggish kinetics, incurring rapid capacity decline and poor rate capability. Here, a series of sodium‐sufficient O3‐type NaNi0.5Mn0.5‐ x Ti x O2 (0 ≤ x ≤ 0.5) cathodes for SIBs is reported and the mechanisms behind their excellent electrochemical performance are studied in comparison to those of their respective end‐members. The combined analysis of in situ X‐ray diffraction, ex situ X‐ray absorption spectroscopy, and scanning transmission electron microscopy for NaNi0.5Mn0.2Ti0.3O2 reveals that the O3‐type phase transforms reversibly into a P3‐type phase upon Na+ deintercalation/intercalation. The substitution of Ti for Mn enlarges interslab distance and could restrain the unfavorable and irreversible multiphase transformation in the high voltage regions that is usually observed in O3‐type NaNi0.5Mn0.5O2, resulting in improved Na cell performance. This integration of macroscale and atomicscale engineering strategy might open up the modulation of the chemical and physical properties in layered oxides and grasp new insight into the optimal design of high‐performance cathode materials for SIBs. 相似文献
9.
Na‐ion batteries (NIBs) are ideal candidates for solving the problem of large‐scale energy storage, due to the worldwide sodium resource, but the efforts in exploring and synthesizing low‐cost and eco‐friendly anode materials with convenient technologies and low‐cost raw materials are still insufficient. Herein, with the assistance of a simple calcination method and common raw materials, the environmentally friendly and nontoxic N‐doped C@Zn3B2O6 composite is directly synthesized and proved to be a potential anode material for NIBs. The composite demonstrates a high reversible charge capacity of 446.2 mAh g?1 and a safe and suitable average voltage of 0.69 V, together with application potential in full cells (discharge capacity of 98.4 mAh g?1 and long cycle performance of 300 cycles at 1000 mA g?1). In addition, the sodium‐ion storage mechanism of N‐doped C@Zn3B2O6 is subsequently studied through air‐insulated ex situ characterizations of X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and Fourier‐transform infrared (FT‐IR) spectroscopy, and is found to be rather different from previous reports on borate anode materials for NIBs and lithium‐ion batteries. The reaction mechanism is deduced and proposed as: Zn3B2O6 + 6Na+ + 6e? ? 3Zn + B2O3 ? 3Na2O, which indicates that the generated boracic phase is electrochemically active and participates in the later discharge/charge progress. 相似文献
10.
Lecai Wang Li Li Hanyong Wang Jingbo Yang Yitian Ma Jiawei Wu Feng Wu Renjie Chen 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(13)
Ni‐rich Li‐ion cathode materials promise high energy density, but are limited in power density and cycle life, resulting from their poor dynamic characteristics and quick degradation. On the other hand, capacitor electrode materials promise high power density and long cycle life but limited capacities. A joint energy storage mechanism of these two kinds is performed in the material‐compositional level in this paper. A valence coupling between carbon π‐electrons and O2? is identified in the as‐prepared composite material, using a tracking X‐ray photoelectron spectroscopy strategy. Besides delivering capacity simultaneously from its LiNi0.8Co0.1Mn0.1O2 and capacitive carbon components with impressive amount and speed, this material shows robust cycling stability by preventing oxygen emission and phase transformation via the discovered valence coupling effect. Structural evolution of the composite shows a more flattened path compared to that of the pure LiNi0.8Co0.1Mn0.1O2, revealed by the in situ X‐ray diffraction strategy. Without obvious phase transformation and losing active contents in this composite material, long cycling can be achieved. 相似文献
11.
In Situ Encapsulating α‐MnS into N,S‐Codoped Nanotube‐Like Carbon as Advanced Anode Material: α → β Phase Transition Promoted Cycling Stability and Superior Li/Na‐Storage Performance in Half/Full Cells
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Dai‐Huo Liu Wen‐Hao Li Yan‐Ping Zheng Zheng Cui Xin Yan Dao‐Sheng Liu Jiawei Wang Yu Zhang Hong‐Yan Lü Feng‐Yang Bai Jin‐Zhi Guo Xing‐Long Wu 《Advanced materials (Deerfield Beach, Fla.)》2018,30(21)
Incorporation of N,S‐codoped nanotube‐like carbon (N,S‐NTC) can endow electrode materials with superior electrochemical properties owing to the unique nanoarchitecture and improved kinetics. Herein, α‐MnS nanoparticles (NPs) are in situ encapsulated into N,S‐NTC, preparing an advanced anode material (α‐MnS@N,S‐NTC) for lithium‐ion/sodium‐ion batteries (LIBs/SIBs). It is for the first time revealed that electrochemical α → β phase transition of MnS NPs during the 1st cycle effectively promotes Li‐storage properties, which is deduced by the studies of ex situ X‐ray diffraction/high‐resolution transmission electron microscopy and electrode kinetics. As a result, the optimized α‐MnS@N,S‐NTC electrode delivers a high Li‐storage capacity (1415 mA h g?1 at 50 mA g?1), excellent rate capability (430 mA h g?1 at 10 A g?1), and long‐term cycling stability (no obvious capacity decay over 5000 cycles at 1 A g?1) with retained morphology. In addition, the N,S‐NTC‐based encapsulation plays the key roles on enhancing the electrochemical properties due to its high conductivity and unique 1D nanoarchitecture with excellent protective effects to active MnS NPs. Furthermore, α‐MnS@N,S‐NTC also delivers high Na‐storage capacity (536 mA h g?1 at 50 mA g?1) without the occurrence of such α → β phase transition and excellent full‐cell performances as coupling with commercial LiFePO4 and LiNi0.6Co0.2Mn0.2O2 cathodes in LIBs as well as Na3V2(PO4)2O2F cathode in SIBs. 相似文献
12.
A High‐Capacity O2‐Type Li‐Rich Cathode Material with a Single‐Layer Li2MnO3 Superstructure
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Yuxuan Zuo Biao Li Ning Jiang Wangsheng Chu Hao Zhang Ruqiang Zou Dingguo Xia 《Advanced materials (Deerfield Beach, Fla.)》2018,30(16)
A high capacity cathode is the key to the realization of high‐energy‐density lithium‐ion batteries. The anionic oxygen redox induced by activation of the Li2MnO3 domain has previously afforded an O3‐type layered Li‐rich material used as the cathode for lithium‐ion batteries with a notably high capacity of 250–300 mAh g?1. However, its practical application in lithium‐ion batteries has been limited due to electrodes made from this material suffering severe voltage fading and capacity decay during cycling. Here, it is shown that an O2‐type Li‐rich material with a single‐layer Li2MnO3 superstructure can deliver an extraordinary reversible capacity of 400 mAh g?1 (energy density: ≈1360 Wh kg?1). The activation of a single‐layer Li2MnO3 enables stable anionic oxygen redox reactions and leads to a highly reversible charge–discharge cycle. Understanding the high performance will further the development of high‐capacity cathode materials that utilize anionic oxygen redox processes. 相似文献
13.
High‐Energy/Power and Low‐Temperature Cathode for Sodium‐Ion Batteries: In Situ XRD Study and Superior Full‐Cell Performance
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Jin‐Zhi Guo Peng‐Fei Wang Xing‐Long Wu Xiao‐Hua Zhang Qingyu Yan Hong Chen Jing‐Ping Zhang Yu‐Guo Guo 《Advanced materials (Deerfield Beach, Fla.)》2017,29(33)
Sodium‐ion batteries (SIBs) are still confronted with several major challenges, including low energy and power densities, short‐term cycle life, and poor low‐temperature performance, which severely hinder their practical applications. Here, a high‐voltage cathode composed of Na3V2(PO4)2O2F nano‐tetraprisms (NVPF‐NTP) is proposed to enhance the energy density of SIBs. The prepared NVPF‐NTP exhibits two high working plateaux at about 4.01 and 3.60 V versus the Na+/Na with a specific capacity of 127.8 mA h g?1. The energy density of NVPF‐NTP reaches up to 486 W h kg?1, which is higher than the majority of other cathode materials previously reported for SIBs. Moreover, due to the low strain (≈2.56% volumetric variation) and superior Na transport kinetics in Na intercalation/extraction processes, as demonstrated by in situ X‐ray diffraction, galvanostatic intermittent titration technique, and cyclic voltammetry at varied scan rates, the NVPF‐NTP shows long‐term cycle life, superior low‐temperature performance, and outstanding high‐rate capabilities. The comparison of Ragone plots further discloses that NVPF‐NTP presents the best power performance among the state‐of‐the‐art cathode materials for SIBs. More importantly, when coupled with an Sb‐based anode, the fabricated sodium‐ion full‐cells also exhibit excellent rate and cycling performances, thus providing a preview of their practical application. 相似文献
14.
Jung‐Hyun Kim Nicholas P. W. Pieczonka Peng Lu Zhongyi Liu Ruimin Qiao Wanli Yang Misle M. Tessema Yang‐Kook Sun Bob R. Powell 《Advanced Materials Interfaces》2015,2(10)
Although LiNi0.5Mn1.5O4 (LNMO) high‐voltage spinel is a promising candidate for a next generation cathode material, LNMO/graphite full cells experience severe capacity fading caused by degradation reactions at electrode/electrolyte interfaces and consequent active Li+ loss in the cells. In this study, it is first reported that in situ formation of a Ti–O enriched cathode/electrolyte interfacial (CEI) layer on a Ti‐substituted LiNi0.5Mn1.2Ti0.3O4 (LNMTO) spinel cathode effectively mitigates electrolyte oxidation and transition metal dissolution, which improves the Coulombic efficiency and cycle life of LNMTO/graphite full cells. The Ti–O enriched CEI layer is produced in situ during an initial cycling of LNMTO as a result of selective Mn and Ni dissolution at its surface, as evidenced by various surface characterizations using X‐ray photoelectron spectroscopy, transmission electron microscopy, time‐of‐flight secondary ion mass spectrometry, Raman spectroscopy, and synchrotron‐based soft X‐ray absorption spectroscopy. The Ti–O enriched CEI has an advantage over traditional LNMO powder coatings, namely the formation of conformal CEI without compromising electronic conduction pathways between cathode particles. 相似文献
15.
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
16.
Zhonghui Sun Xing‐Long Wu Jianan Xu Dongyang Qu Bolin Zhao Zhenyi Gu Wenhao Li Haojie Liang Lifang Gao Yingying Fan Kai Zhou Dongxue Han Shiyu Gan Yuwei Zhang Li Niu 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(19)
Metallic selenides have been widely investigated as promising electrode materials for metal‐ion batteries based on their relatively high theoretical capacity. However, rapid capacity decay and structural collapse resulting from the larger‐sized Na+/K+ greatly hamper their application. Herein, a bimetallic selenide (MoSe2/CoSe2) encapsulated in nitrogen, sulfur‐codoped hollow carbon nanospheres interconnected reduced graphene oxide nanosheets (rGO@MCSe) are successfully designed as advanced anode materials for Na/K‐ion batteries. As expected, the significant pseudocapacitive charge storage behavior substantially contributes to superior rate capability. Specifically, it achieves a high reversible specific capacity of 311 mAh g?1 at 10 A g?1 in NIBs and 310 mAh g?1 at 5 A g?1 in KIBs. A combination of ex situ X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy tests reveals the phase transition of rGO@MCSe in NIBs/KIBs. Unexpectedly, they show quite different Na+/K+ insertion/extraction reaction mechanisms for both cells, maybe due to more sluggish K+ diffusion kinetics than that of Na+. More significantly, it shows excellent energy storage properties in Na/K‐ion full cells when coupled with Na3V2(PO4)2O2F and PTCDA@450 °C cathodes. This work offers an advanced electrode construction guidance for the development of high‐performance energy storage devices. 相似文献
17.
Suppressing Surface Lattice Oxygen Release of Li‐Rich Cathode Materials via Heterostructured Spinel Li4Mn5O12 Coating
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Xu‐Dong Zhang Ji‐Lei Shi Jia‐Yan Liang Ya‐Xia Yin Jie‐Nan Zhang Xi‐Qian Yu Yu‐Guo Guo 《Advanced materials (Deerfield Beach, Fla.)》2018,30(29)
Lithium‐rich layered oxides with the capability to realize extraordinary capacity through anodic redox as well as classical cationic redox have spurred extensive attention. However, the oxygen‐involving process inevitably leads to instability of the oxygen framework and ultimately lattice oxygen release from the surface, which incurs capacity decline, voltage fading, and poor kinetics. Herein, it is identified that this predicament can be diminished by constructing a spinel Li4Mn5O12 coating, which is inherently stable in the lattice framework to prevent oxygen release of the lithium‐rich layered oxides at the deep delithiated state. The controlled KMnO4 oxidation strategy ensures uniform and integrated encapsulation of Li4Mn5O12 with structural compatibility to the layered core. With this layer suppressing oxygen release, the related phase transformation and catalytic side reaction that preferentially start from the surface are consequently hindered, as evidenced by detailed structural evolution during Li+ extraction/insertion. The heterostructure cathode exhibits highly competitive energy‐storage properties including capacity retention of 83.1% after 300 cycles at 0.2 C, good voltage stability, and favorable kinetics. These results highlight the essentiality of oxygen framework stability and effectiveness of this spinel Li4Mn5O12 coating strategy in stabilizing the surface of lithium‐rich layered oxides against lattice oxygen escaping for designing high‐performance cathode materials for high‐energy‐density lithium‐ion batteries. 相似文献
18.
Carbon‐Coated Na3.32Fe2.34(P2O7)2 Cathode Material for High‐Rate and Long‐Life Sodium‐Ion Batteries
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Mingzhe Chen Lingna Chen Zhe Hu Qiannan Liu Binwei Zhang Yuxiang Hu Qinfen Gu Jian‐Li Wang Lian‐Zhou Wang Xiaodong Guo Shu‐Lei Chou Shi‐Xue Dou 《Advanced materials (Deerfield Beach, Fla.)》2017,29(21)
Rechargeable sodium‐ion batteries are proposed as the most appropriate alternative to lithium batteries due to the fast consumption of the limited lithium resources. Due to their improved safety, polyanion framework compounds have recently gained attention as potential candidates. With the earth‐abundant element Fe being the redox center, the uniform carbon‐coated Na3.32Fe2.34(P2O7)2/C composite represents a promising alternative for sodium‐ion batteries. The electrochemical results show that the as‐prepared Na3.32Fe2.34(P2O7)2/C composite can deliver capacity of ≈100 mA h g?1 at 0.1 C (1 C = 120 mA g?1), with capacity retention of 92.3% at 0.5 C after 300 cycles. After adding fluoroethylene carbonate additive to the electrolyte, 89.6% of the initial capacity is maintained, even after 1100 cycles at 5 C. The electrochemical mechanism is systematically investigated via both in situ synchrotron X‐ray diffraction and density functional theory calculations. The results show that the sodiation and desodiation are single‐phase‐transition processes with two 1D sodium paths, which facilitates fast ionic diffusion. A small volume change, nearly 100% first‐cycle Coulombic efficiency, and a pseudocapacitance contribution are also demonstrated. This research indicates that this new compound could be a potential competitor for other iron‐based cathode electrodes for application in large‐scale Na rechargeable batteries. 相似文献
19.
Natalia Voronina Jae Hyeon Jo Aishuak Konarov Jongsoon Kim Seung‐Taek Myung 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(20)
In this work, rhombohedral KTi2(PO4)3 is introduced to investigate the related theoretical, structural, and electrochemical properties in K cells. The suggested KTi2(PO4)3 modified by electro‐conducting carbon brings about a flat voltage profile at ≈1.6 V, providing a large capacity of 126 mAh (g‐phosphate)?1, corresponding to 98.5% of the theoretical capacity, with 89% capacity retention for 500 cycles. Structural analyses using electrochemical performance measurements, first‐principles calculations, ex situ X‐ray absorption spectroscopy, and operando X‐ray diffraction provide new insights into the reaction mechanism controlling the (de)intercalation of potassium ions into the host KTi2(PO4)3 structure. It is observed that a biphasic redox process by Ti4+/3+ occurs upon discharge, whereas a single‐phase reaction followed by a biphasic process occurs upon charge. Along with the structural refinement of the electrochemically reduced K3Ti2(PO4)3 phase, these new findings provide insight into the reaction mechanism in Na superionic conductor (NASICON)‐type KTi2(PO4)3. The present approach can also be extended to the investigation of other NASICON‐type materials for potassium‐ion batteries. 相似文献
20.
Soumyadeep Sinha Pravin N. Didwal Dip K. Nandi Rakesh Verma Jae Yu Cho Soo‐Hyun Kim Chan‐Jin Park Jaeyeong Heo 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(37)
Although sodium‐ion batteries (SIBs) are considered promising alternatives to their Li counterparts, they still suffer from challenges like slow kinetics of the sodiation process, large volume change, and inferior cycling stability. On the other hand, the presence of additional reversible conversion reactions makes the metal compounds the preferred anode materials over carbon. However, conductivity and crystallinity of such materials often play the pivotal role in this regard. To address these issues, atomic layer deposited double‐anion‐based ternary zinc oxysulfide (ZnOS) thin films as an anode material in SIBs are reported. Electrochemical studies are carried out with different O/(O+S) ratios, including O‐rich and S‐rich crystalline ZnOS along with the amorphous phase. Amorphous ZnOS with the O/(O+S) ratio of ≈0.4 delivers the most stable and considerably high specific (and volumetric) capacities of 271.9 (≈1315.6 mAh cm?3) and 173.1 mAh g?1 (≈837.7 mAh cm?3) at the current densities of 500 and 1000 mA g?1, respectively. A dominant capacitive‐controlled contribution of the amorphous ZnOS anode indicates faster electrochemical reaction kinetics. An electrochemical reaction mechanism is also proposed via X‐ray photoelectron spectroscopy analyses. A comparison of the cycling stability further establishes the advantage of this double‐anion‐based material over pristine ZnO and ZnS anodes. 相似文献