Reinvestigations of the Li2O–WO3 system

Tabero, P.; Frąckowiak, Artur

doi:10.1007/s10973-017-6355-8

Cited by 11 publications

(7 citation statements)

References 26 publications

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“…In our opinion, the surface nano‐WO 3 on Ni(OH) 2 should react with LiOH or Li 2 O to form Li x W y O z phases, which normally have melting points in the temperature range of 700–750 °C. [ 23 ] As a result, these Li x W y O z phases can easily wet the surfaces of the secondary grains during synthesis and then infuse along all the grain boundaries between the primary particles. We infer that it is primarily the Li x W y O z phase which wets the surfaces of the primary particle grains that behaves like a barrier to slow down Ni interdiffusion and therefore hinders the growth of the primary grains as temperature increases.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of Action of the Tungsten Dopant in LiNiO₂ Positive Electrode Materials

Geng

Rathore

Heino

et al. 2021

Advanced Energy Materials

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The addition of tungsten has been reported to greatly improve the capacity retention of Ni‐rich layered oxide cathode materials in lithium‐ion batteries. In this work, Ni(OH)2 precursors, coated with WO3 and also W‐containing precursors prepared by co‐precipitation followed by heat treatment with LiOH·H2O, are studied. Structural analysi s and electron microscopy show that W is incorporated as amorphous LixWyOz phases concentrated in all the grain boundaries between the primary particles of LiNiO2 (LNO) and on the surface of the secondary particles. Tungsten does not substitute for Ni or Li in the LNO lattice no matter how W is added at the precursor synthesis stage. Scanning electron microscopy (SEM) images show that adding W greatly suppresses primary particle growth during synthesis. In agreement with previous literature reports, cycling test results show that 1% W added to LNO can greatly improve charge–discharge capacity retention while also delivering a high specific capacity. The LixWyOz amorphous phases act as coating layer on both the primary and secondary particles, restrict primary particle growth during synthesis and increase the resistance of the secondary particles to microcracking.

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Section: Resultsmentioning

confidence: 99%

Mechanism of Action of the Tungsten Dopant in LiNiO₂ Positive Electrode Materials

Geng

Rathore

Heino

et al. 2021

Advanced Energy Materials

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“…In general, the occurrence of two shoulders in a densification curve implies the existence of two different sintering mechanisms. [8] As LWO melts at 742 °C, [15] the second shoulder from 750 °C for 9 wt.% LWO is very likely attributed to liquid phase sintering as detailed later. As the dilatometry is performed with a heating rate of 300 K/h up to temperatures of 1100 °C and no holding time only low relative densities were achieved.…”

Section: Resultsmentioning

confidence: 99%

The Impact of Lithium Tungstate on the Densification and Conductivity of Phosphate Lithium‐Ion Conductors

Odenwald

Davaasuren

et al. 2021

ChemElectroChem

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Phosphate lithium‐ion conductors are outstanding electrolyte materials for solid‐state lithium batteries. As polycrystalline ceramics, they must be sintered at high temperatures. Lithium tungstate Li2WO4 (LWO) is reported for the first time as an effective sintering aid to reduce the sintering temperature for one of the most common solid‐state lithium‐ion conductors, Li1.5Al0.5Ti1.5(PO4)3 (LATP). While densification of LATP without sintering aids requires temperatures of at least 950 °C to obtain a relative density of 90 %, here relative densities of 90–95 % are achieved even at 775 °C when 5 wt.% of LWO are added. At 800 °C the LATP containing 5–7 wt.% LWO densifies to a relative density of 97.2 %. The ionic conductivity of LWO containing LATP is generally higher than that of pure LATP sintered at the same temperature. LATP containing 7 wt.% LWO shows high ionic conductivity of 4.4×10−4 S/cm after sintering at 825 °C. A significant reduction in sintering temperature, an increase in density and in the ionic conductivity of LATP as well as its non‐toxicity render LWO a very promising sintering aid for the development of LATP‐based solid state batteries.

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“…The solid-state synthesis of mixed metal oxide materials may be significantly facilitated by utilizing organic salts as both metal sources and sintering additives. 47 The application of sintering aids facilitates the sintering process and generally leads to processing temperature reduction. However, the most important advantage of their implementation into synthesis is introducing the vacancy-mediated LPS process.…”

Section: Resultsmentioning

confidence: 99%

An Innovative Solid-State Approach to Zinc Orthostannate: Remarkable Sintering Temperature Reduction via Lithium Doping and Mechanochemical Activation of Low-Melting Precursors

Marynowski

Saski

Pałuba

et al. 2022

ACS Appl. Electron. Mater.

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Zinc orthostannate, often called zinc tin oxide (ZTO), possesses unique physical characteristics and is a promising wide band gap (3.6 eV) n-type semiconductor material for a broad range of applications. The standard solid-state fabrication of ZTO requires prolonged heat treatment of zinc oxide and stannic oxide powders at around 1000 °C. The biggest drawback of this process is the evaporation of zinc oxide during the synthesis. We report an innovative and efficient mechanochemically supported solid-state approach to Li-doped ZTO synthesis with the implementation of a low-melting lithium hydroxide sintering aid, which offers a significant lowering of the sintering temperature down to 850 °C and time to 90 min, maintaining the high quality of the resulting Lidoped ZTO materials. The effect of sintering temperatures in the range 850−900 °C on photoluminescence characteristics of the ZTO materials was studied, and the PL spectra well corroborate with the XPS data and the presence of O as well as Zn or Sn vacancies. The band gap value of the resulting ZTO materials oscillated around 3.6 eV. Moreover, a comprehensive spectroscopic and microscopic examination of the optimized Li-doped ZTO materials provided more profound insight into its vacancy-mediated formation via liquid-phase sintering and its gradual advancement in the low-temperature regime of 850−900 °C. Additionally, the surface analysis of the selected highest quality materials enabled the determination of the Zn diffusion from the Li-doped ZTO lattice to its surface, expanding the knowledge of the diffusion−evaporation process.

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Reinvestigations of the Li2O–WO3 system

Cited by 11 publications

References 26 publications

Mechanism of Action of the Tungsten Dopant in LiNiO₂ Positive Electrode Materials

Mechanism of Action of the Tungsten Dopant in LiNiO₂ Positive Electrode Materials

The Impact of Lithium Tungstate on the Densification and Conductivity of Phosphate Lithium‐Ion Conductors

An Innovative Solid-State Approach to Zinc Orthostannate: Remarkable Sintering Temperature Reduction via Lithium Doping and Mechanochemical Activation of Low-Melting Precursors

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Reinvestigations of the Li2O–WO3 system

Cited by 11 publications

References 26 publications

Mechanism of Action of the Tungsten Dopant in LiNiO2 Positive Electrode Materials

Mechanism of Action of the Tungsten Dopant in LiNiO2 Positive Electrode Materials

The Impact of Lithium Tungstate on the Densification and Conductivity of Phosphate Lithium‐Ion Conductors

An Innovative Solid-State Approach to Zinc Orthostannate: Remarkable Sintering Temperature Reduction via Lithium Doping and Mechanochemical Activation of Low-Melting Precursors

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Mechanism of Action of the Tungsten Dopant in LiNiO₂ Positive Electrode Materials

Mechanism of Action of the Tungsten Dopant in LiNiO₂ Positive Electrode Materials