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1.
Adv Mater ; : e2202137, 2022 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-35502520

RESUMO

The layered sodium transition metal oxide, NaTMO2 (TM; transition metal), with a binary or ternary phases has displayed the outstanding electrochemical performances as a new class of strategy cathode materials for sodium-ion batteries (SIBs). Despite their demonstrated ability and advantages, however, a precise and comprehensive understanding of the underlying structure accounting for their intrinsic structural stability during cycling is still lacking even as the mixed-phase compounds exhibit their inherent structural complexity compared with their single-phase counterparts. Herein, we offer an in-depth phase analysis of our developed Na1-x TMO2 cathode materials, Na0.76 Ni0.20 Fe0.40 Mn0.40 O2 with P2- and O3-type phases (NFMO-P2/O3). We also provide structural visualization on an atomic scale and unveil the following findings: (i) the existence of a mixed-phase intergrowth layer distribution and unequal distribution of P2 and O3 phases along two different crystal plane indices; and, (ii) a complete reversible charge/discharge process for the initial two cycles that displays a simple phase transformation that is unprecedented. Moreover, first-principles calculations method supported evidence of the formation of a binary NFMO-P2/O3 compound, over the proposed hypothetical monophasic structures (O3, P3, O'3, and P2 phases). As a result, the synergetic effect of the simultaneous existence of P- and O-type phases with their unique structures allow an extraordinary level of capacity retention in a wide range of voltage (1.5-4.5 V). We believe that the insightful understanding of our proposed materials can introduce new perspectives for the development of high-voltage cathode materials for SIBs. This article is protected by copyright. All rights reserved.

2.
Artigo em Inglês | MEDLINE | ID: mdl-35441399

RESUMO

Dissolution of transition metal ions, such as Ni 2+ , Mn 2+ , from layered-structured Ni-rich cathode can migrate to the anode side and aggravate the electrochemical polarization and capacity degradation of lithium-ion batteries (LIBs). The investigations of the impact and distribution of Ni species on the solid electrolyte interphase (SEI) on anode are crucial to understand the failure mechanism of LIBs in this scenario, yet few works have been reported due to the complicated structure of SEI. Herein, we used Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) technique coupled with multivariate data analysis (MVA) to intuitively characterize the distribution of Ni species in SEI. We find that, in EC-based electrolyte, SEI on the graphite electrode exhibits a multi-stratum structure. In contrary to the conventional view, the outer and intermediate stratums are dominated by the decomposition products related with LiPF 6 salt, such as phosphates, fluorophosphates, and LiF, during the formation cycles. After accelerated aging the full cell of LiNi 0.88 Co 0.08 Mn 0.04 O 2 (NCM88)/graphite for 50 cycles, the concentration of Ni dissolved in electrolyte reaches ca. 690 ppm. With multivariate curve resolution analysis of TOF-SIMS 3D data, a strong correlation between the dissolved-Ni and organic species in SEI on graphite is illustrated. The ion exchange reaction between Ni 2+ and Li + in SEI is demonstrated to be the main reason for the increase of SEI resistivity.

3.
Nat Commun ; 13(1): 2319, 2022 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-35484128

RESUMO

High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi0.88Co0.09Mn0.03O2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 µm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg-1 at 0.1 C and 25 °C.

4.
Adv Mater ; 34(19): e2200744, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35276756

RESUMO

Surface reconstruction of Ni-rich layered oxides (NLO) degrades the cycling stability and safety of high-energy-density lithium-ion batteries (LIBs), which challenges typical surface-modification approaches to build a robust interface with electrochemical activity. Here, a strategy of leveraging the low-strain analogues of Li- and Mn-rich layered oxides (LMR) to reconstruct a stable surface on the Ni-rich layered cathodes is proposed. The new surface structure not only consists of a gradient chemical composition but also contains a defect-rich structure regarding the formation of oxygen vacancies and cationic ordering, which can simultaneously facilitate lithium diffusion and stabilize the crystal structure during the (de)lithiation. These features in the NLO lead to a dramatic improvement in electrochemical properties, especially the cyclability under high voltage cycling, exhibiting the 30% increase in capacity retention after 200 cycles at the current density of 1 C (3.0-4.6 V). The findings offer a facile and effective way to regulate defect chemistry and surface structure in parallel on Ni-rich layered structure cathodes to achieve high-energy density LIBs.

5.
Artigo em Inglês | MEDLINE | ID: mdl-34981923

RESUMO

The prosperity of the electric vehicle industry is driving the research and development of lithium-ion batteries. As one of the core components in the entire battery system, cathode materials are currently facing major challenges in pushing a higher capacity up to the materials' theoretical limits and transitioning away from unaffordable metals. The search for next-generation cathode materials has shifted to high-nickel and cobalt-free cathodes to meet these requirements. In this review, we distinctly point out the shortcomings of cobalt in stabilizing layered structures and systematically summarize the recent efforts to eliminate cobalt and achieve higher nickel content in layered cathode materials. Finally, a reasonable prospect is put forward for further development of layered cathode materials and other promising candidates, which is likely to spur a wave of efforts toward developing high-performance and low-cost Li-ion batteries.

6.
Nano Lett ; 22(1): 263-270, 2022 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-34905368

RESUMO

Nonuniform Li deposition causes dendrites and low Coulombic efficiency (CE), seriously hindering the practical applications of Li metal. Herein, we developed an artificial solid-state interphase (SEI) with planar polycyclic aromatic hydrocarbons (PAHs) on the surface of Li metal anodes by a facile in situ formation technology. The resultant dihydroxyviolanthron (DHV) layers serve as the protective layer to stabilize the SEI. In addition, the oxygen-containing functional groups in the soft and conformal SEI film can regulate the diffusion and transport of Li ions to homogenize the deposition of Li metal. The artificial SEI significantly improves the CEs and shows superior cyclability of over 1000 h at 4 mAh cm-2. The LiFePO4/Li cell (2.8 mAh cm-2) enables a long cyclability for 300 cycles and high CEs of 99.8%. This work offers a new strategy to inhibit Li dendrite growth and enlightens the design on stable SEI for metal anodes.

7.
Nat Commun ; 12(1): 6024, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34654811

RESUMO

Mechanical integrity issues such as particle cracking are considered one of the leading causes of structural deterioration and limited long-term cycle stability for Ni-rich cathode materials of Li-ion batteries. Indeed, the detrimental effects generated from the crack formation are not yet entirely addressed. Here, applying physicochemical and electrochemical ex situ and in situ characterizations, the effect of Co and Mn on the mechanical properties of the Ni-rich material are thoroughly investigated. As a result, we successfully mitigate the particle cracking issue in Ni-rich cathodes via rational concentration gradient design without sacrificing the electrode capacity. Our result reveals that the Co-enriched surface design in Ni-rich particles benefits from its low stiffness, which can effectively suppress the formation of particle cracking. Meanwhile, the Mn-enriched core limits internal expansion and improve structural integrity. The concentration gradient design also promotes morphological stability and cycling performances in Li metal coin cell configuration.

8.
Nat Commun ; 12(1): 5370, 2021 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-34508097

RESUMO

High-energy density lithium-rich layered oxides are among the most promising candidates for next-generation energy storage. Unfortunately, these materials suffer from severe electrochemical degradation that includes capacity loss and voltage decay during long-term cycling. Present research efforts are primarily focused on understanding voltage decay phenomena while origins for capacity degradation have been largely ignored. Here, we thoroughly investigate causes for electrochemical performance decline with an emphasis on capacity loss in the lithium-rich layered oxides, as well as reaction pathways and kinetics. Advanced synchrotron-based X-ray two-dimensional and three-dimensional imaging techniques are combined with spectroscopic and scattering techniques to spatially visualize the reactivity at multiple length-scales on lithium- and manganese-rich layered oxides. These methods provide direct evidence for inhomogeneous manganese reactivity and ionic nickel rearrangement. Coupling deactivated manganese with nickel migration provides sluggish reaction kinetics and induces serious structural instability in the material. Our findings provide new insights and further understanding of electrochemical degradation, which serve to facilitate cathode material design improvements.

9.
Polymers (Basel) ; 13(15)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34372089

RESUMO

Conjugated polymers with narrower bandgaps usually induce higher carrier mobility, which is vital for the improved thermoelectric performance of polymeric materials. Herein, two indacenodithiophene (IDT) based donor-acceptor (D-A) conjugated polymers (PIDT-BBT and PIDTT-BBT) were designed and synthesized, both of which exhibited low-bandgaps. PIDTT-BBT showed a more planar backbone and carrier mobility that was two orders of magnitude higher (2.74 × 10-2 cm2V-1s-1) than that of PIDT-BBT (4.52 × 10-4 cm2V-1s-1). Both exhibited excellent thermoelectric performance after doping with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, where PIDTT-BBT exhibited a larger conductivity (0.181 S cm-1) and a higher power factor (1.861 µW m-1 K-2) due to its higher carrier mobility. The maximum power factor of PIDTT-BBT reached 4.04 µW m-1 K-2 at 382 K. It is believed that conjugated polymers with a low bandgap are promising in the field of organic thermoelectric materials.

10.
Nat Commun ; 12(1): 3085, 2021 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-34035292

RESUMO

Defect engineering on electrode materials is considered an effective approach to improve the electrochemical performance of batteries since the presence of a variety of defects with different dimensions may promote ion diffusion and provide extra storage sites. However, manipulating defects and obtaining an in-depth understanding of their role in electrode materials remain challenging. Here, we deliberately introduce a considerable number of twin boundaries into spinel cathodes by adjusting the synthesis conditions. Through high-resolution scanning transmission electron microscopy and neutron diffraction, the detailed structures of the twin boundary defects are clarified, and the formation of twin boundary defects is attributed to agminated lithium atoms occupying the Mn sites around the twin boundary. In combination with electrochemical experiments and first-principles calculations, we demonstrate that the presence of twin boundaries in the spinel cathode enables fast lithium-ion diffusion, leading to excellent fast charging performance, namely, 75% and 58% capacity retention at 5 C and 10 C, respectively. These findings demonstrate a simple and effective approach for fabricating fast-charging cathodes through the use of defect engineering.

11.
Molecules ; 26(4)2021 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-33670379

RESUMO

A p-type thermoelectric conjugated polymer based on indacenodithiophene and benzothiadiazole is designed and synthesized by replacing normal aliphatic side chains (P1) with conjugated aromatic benzene substituents (P2). The introduced bulky substituent on P2 is detrimental to form the intensified packing of polymers, therefore, it hinders the efficient transporting of the charge carriers, eventually resulting in a lower conductivity compared to that of the polymers bearing aliphatic side chains (P1). These results reveal that the modification of side chains on conjugated polymers is crucial to rationally designed thermoelectric polymers with high performance.


Assuntos
Benzeno/química , Compostos Orgânicos/química , Polímeros/química , Centrais Elétricas
12.
Adv Mater ; 33(13): e2008194, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33645858

RESUMO

Oxygen-redox of layer-structured metal-oxide cathodes has drawn great attention as an effective approach to break through the bottleneck of their capacity limit. However, reversible oxygen-redox can only be obtained in the high-voltage region (usually over 3.5 V) in current metal-oxide cathodes. Here, we realize reversible oxygen-redox in a wide voltage range of 1.5-4.5 V in a P2-layered Na0.7 Mg0.2 [Fe0.2 Mn0.6 □0.2 ]O2 cathode material, where intrinsic vacancies are located in transition-metal (TM) sites and Mg-ions are located in Na sites. Mg-ions in the Na layer serve as "pillars" to stabilize the layered structure during electrochemical cycling, especially in the high-voltage region. Intrinsic vacancies in the TM layer create the local configurations of "□-O-□", "Na-O-□" and "Mg-O-□" to trigger oxygen-redox in the whole voltage range of charge-discharge. Time-resolved techniques demonstrate that the P2 phase is well maintained in a wide potential window range of 1.5-4.5 V even at 10 C. It is revealed that charge compensation from Mn- and O-ions contributes to the whole voltage range of 1.5-4.5 V, while the redox of Fe-ions only contributes to the high-voltage region of 3.0-4.5 V. The orphaned electrons in the nonbonding 2p orbitals of O that point toward TM-vacancy sites are responsible for reversible oxygen-redox, and Mg-ions in Na sites suppress oxygen release effectively.

13.
Bioorg Med Chem Lett ; 33: 127749, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33340663

RESUMO

In an in-house screening, 1H-pyrrolo[2,3-b]pyridine scaffold was found to have high inhibition on TNIK. Several series of compounds were designed and synthesized, among which some compounds had potent TNIK inhibition with IC50 values lower than 1 nM. Some compounds showed concentration-dependent characteristics of IL-2 inhibition. These results provided new applications of TNIK inhibitors and new prospects of TNIK as a drug target.


Assuntos
Descoberta de Drogas , Inibidores de Proteínas Quinases/farmacologia , Piridinas/farmacologia , Pirróis/farmacologia , Relação Dose-Resposta a Droga , Humanos , Estrutura Molecular , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/química , Piridinas/síntese química , Piridinas/química , Pirróis/síntese química , Pirróis/química , Relação Estrutura-Atividade
14.
ACS Nano ; 14(11): 15669-15677, 2020 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-33147406

RESUMO

Materials storing energy via an alloying reaction are promising anode candidates in rechargeable lithium-ion batteries (LIBs) due to their much higher energy density than the current graphite anode. Until now, the volumetric expansion of such electrode particles during lithiation has been considered as solely responsible for cycling-induced structural failure. In this work, we report different structural failure mechanisms using single-crystalline bismuth nanowires as the alloying-based anode. The Li-Bi alloying process exhibits a two-step transition, that is, Bi-Li1Bi and Li1Bi-Li3Bi. Interestingly, the Bi-Li1Bi phase transition occurs not only in the bulk Bi nanowire but also on the particle surface showing its characteristic behavior. The bulk alloying kinetics favors a Bi-(012)-facilitated anisotropic lithiation, whose mechanism and energetics are further studied using the density functional theory calculations. More importantly, the protrusion of Li1Bi nanograins as a result of anisotropic Li-Bi alloying is found to dominate the surface morphology of Bi particles. The growth kinetics of Li1Bi protrusions is understood atomically with the identification of two different controlling mechanisms, that is, the dislocation-assisted strain relaxation at the Bi/Li1Bi interface and the short-range migration of Bi supporting the off-Bi growth of Li1Bi. As loosely rooted to the bulk substrate and easily peeled off and detached into the electrolyte, these nanoscale protrusions developed during battery cycling are believed to be an important factor responsible for the capacity decay of such alloying-based anodes at the electrode level.

15.
Nature ; 585(7823): 63-67, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32879503

RESUMO

Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications1-3. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. Here we report that disordered rock salt4,5 Li3+xV2O5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li+ reference electrode. The increased potential compared to graphite6,7 reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li3V2O5 anode yields a cell voltage much higher than does a battery using a commercial fast-charging lithium titanate anode or other intercalation anode candidates (Li3VO4 and LiV0.5Ti0.5S2)8,9. Further, disordered rock salt Li3V2O5 can perform over 1,000 charge-discharge cycles with negligible capacity decay and exhibits exceptional rate capability, delivering over 40 per cent of its capacity in 20 seconds. We attribute the low voltage and high rate capability of disordered rock salt Li3V2O5 to a redistributive lithium intercalation mechanism with low energy barriers revealed via ab initio calculations. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries.

16.
J Am Chem Soc ; 142(35): 14966-14973, 2020 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-32786761

RESUMO

The search for batteries with high energy density has highlighted lithium-rich manganese-based layered oxides due to their exceptionally high capacity. Although it is clear that both cationic and anionic redox are present in the charge compensation mechanism, the microstructural evolution of the Li2MnO3-like phase during anionic redox and its role in battery performance and structural stability are still not fully understood. Here, we systematically probe microstructural evolution using spatially resolved synchrotron X-ray measurements and reveal an underlying interaction between the Li2MnO3-like domains and bulk rhombohedral structure. Mn ion activation and a previously unobserved structural distortion are discovered at high voltages, and can be related to structural strain present in the Li2MnO3-like phase upon substantial lithium ion extraction. Moreover, we elucidate a correlation between this structural distortion and irreversible phase transitions by thermally perturbing delithiated samples. These insights highlight a pathway toward achieving high capacity cathode materials required for future commercial applications.

17.
Adv Sci (Weinh) ; 7(16): 2001002, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32832356

RESUMO

There are growing interests in metal-free heteroatom-doped carbons for electrochemical CO2 reduction. Previous studies extensively focus on the effect of N-doping, and their products severely suffer from low current density (mostly <2 mA cm-2) and limited selectivity (<90%). Here, it is reported that heteroatom codoping offers a promising solution to the above challenge. As a proof of concept, N,P-codoped mesoporous carbon is prepared by annealing phytic-acid-functionalized ZIF-8 in NH3. In CO2-saturated 0.5 m NaHCO3, the catalyst enables CO2 reduction to CO with great selectivity close to 100% and large CO partial current density (≈8 mA cm-2), which are, to the best of knowledge, superior to all other relevant competitors. Theoretical simulations show that the improved activity and selectivity are stemmed from the enhanced surface adsorption of *COOH and *CO intermediates as a result of the synergy of N and P codoping.

18.
Polymers (Basel) ; 12(7)2020 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-32629831

RESUMO

π-conjugated backbones play a fundamental role in determining the thermoelectric (TE) properties of organic semiconductors. Understanding the relationship between the structure-property-function can help us screen valuable materials. In this study, we designed and synthesized a series of conjugated copolymers (P1, P2, and P3) based on an indacenodithiophene (IDT) building block. A copolymer (P3) with an alternating donor-acceptor (D-A) structure exhibits a narrower band gap and higher carrier mobility, which may be due to the D-A structure that helps reduce the charge carrier transport obstacles. In the end, its power factor reaches 4.91 µW m-1 K-2 at room temperature after doping, which is superior to those of non-D-A IDT-based copolymers (P1 and P2). These results indicate that moderate adjustment of the polymer backbone is an effective way to improve the TE properties of copolymers.

19.
ACS Nano ; 14(7): 9117-9124, 2020 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-32584544

RESUMO

Sodium-ion batteries have attracted widespread attention for cost-effective and large-scale electric energy storage. However, their practical deployment has been largely retarded by the lack of choice of efficient anode materials featuring large capacity and electrochemical stability and robustness. Herein, we report a durian-inspired design and template-free fabrication of a robust sodium anode based on triangular pyramid arrays of Bi0.75Sb0.25 alloy electrodeposited on Cu substrates. The Bi0.75Sb0.25 arrays exhibit an appreciable electrochemical robustness for sodium storage, sustaining a reversible capability 335 mAh g-1 at a high rate of 2.5 A g-1 and 87% of the initial capacity over 2000 cycles. We further demonstrate the applicability of the Bi0.75Sb0.25 array anode in sodium full cells by pairing it with a Na3V2(PO4)3/C cathode. This full cell achieves a high specific energy of 203 Wh kg-1 (based on both active electrodes). Such an enhanced performance is attributed to the thorny-durian-like architecture and bimetallic alloy composition. The pyramid tip induces ion enrichment for rapid charge-transfer reaction, while the alloy design reduces the electrode volume swelling for stable Na cycling.

20.
Adv Mater ; 32(30): e2000992, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32538508

RESUMO

Palladium is a promising material for electrochemical CO2 reduction to formate with high Faradaic efficiency near the equilibrium potential. It unfortunately suffers from problematic operation stability due to CO poisoning on surface. Here, it is demonstrated that alloying is an effective strategy to alleviate this problem. Mesoporous PdAg nanospheres with uniform size and composition are prepared from the co-reduction of palladium and silver precursors in aqueous solution using dioctadecyldimethylammonium chloride as the structure-directing agent. The best candidate can initiate CO2 reduction at zero overpotential and achieve high formate selectivity close to 100% and great stability even at <-0.2 V versus reversible hydrogen electrode. The high selectivity and stability are believed to result from the electronic coupling between Pd and Ag, which lowers the d-band center of Pd and thereby significantly enhances its CO tolerance, as evidenced by both electrochemical analysis and theoretical simulations.

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