Defect-mediated ripening of core-shell nanostructures

Zhang, Qiubo; Peng, Xiaoyuan; Nie, Yifan; Zheng, Qi; Shangguan, Junyi; Zhu, Chao; Bustillo, Karen C.; Ercius, Peter; Wang, Lin‐Wang; Limmer, David T.; Zheng, Haimei

doi:10.1038/s41467-022-29847-8

Cited by 35 publications

(23 citation statements)

References 38 publications

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“…However, when the temperature reaches 270 °C, the increased reactivity of the system in the annealing medium can slightly affect the cationic homogeneity along the NPs, modifying the cell parameter, with a consequent increase of the strain in the nanostructure. 31,32 On the other hand, the sample annealed at 210 °C in the oven (CFO210-oven) has cell parameter and crystal size values consistent with those obtained for the solvent-mediated annealed samples, but the calculated microstrain is much larger. The different heating treatment environment has thus a different effect on the capability of the NPs of releasing the stress.…”

Section: ■ Results and Discussionsupporting

confidence: 64%

Hardening of Cobalt Ferrite Nanoparticles by Local Crystal Strain Release: Implications for Rare Earth Free Magnets

Muzzi

Lottini

Yaacoub

et al. 2022

ACS Appl. Nano Mater.

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In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets.

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Section: ■ Results and Discussionsupporting

confidence: 64%

Hardening of Cobalt Ferrite Nanoparticles by Local Crystal Strain Release: Implications for Rare Earth Free Magnets

Muzzi

Lottini

Yaacoub

et al. 2022

ACS Appl. Nano Mater.

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“…The magnified images (Figure 4d) of its morphology show cracks on the surface of the particle. Since the healing of the cracks experience a process from nucleation to growth, 50 the presence of cracks in RSNCM523 formed by non-topotactic transformation may be related to the inhomogeneous nucleation sites produced by different microstructures (rock salt/spinel) on the surface of SNCM523. Because of this, there are also unrepaired cracks in the bulk of RSNCM523 in addition to the surface (Figure 4e).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Topotactic Transformation of Surface Structure Enabling Direct Regeneration of Spent Lithium-Ion Battery Cathodes

et al. 2023

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Recycling spent lithium-ion batteries (LIBs) has become an urgent task to address the issues of resource shortage and potential environmental pollution. However, direct recycling of the spent LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode is challenging because the strong electrostatic repulsion from a transition metal octahedron in the lithium layer provided by the rock salt/spinel phase that is formed on the surface of the cycled cathode severely disrupts Li + transport, which restrains lithium replenishment during regeneration, resulting in the regenerated cathode with inferior capacity and cycling performance. Here, we propose the topotactic transformation of the stable rock salt/spinel phase into Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 and then back to the NCM523 cathode. As a result, a topotactic relithiation reaction with low migration barriers occurs with facile Li + transport in a channel (from one octahedral site to another, passing through a tetrahedral intermediate) with weakened electrostatic repulsion, which greatly improves lithium replenishment during regeneration. In addition, the proposed method can be extended to repair spent NCM523 black mass, spent LiNi 0.6 Co 0.2 Mn 0.2 O 2 , and spent LiCoO 2 cathodes, whose electrochemical performance after regeneration is comparable to that of the commercial pristine cathodes. This work demonstrates a fast topotactic relithiation process during regeneration by modifying Li + transport channels, providing a unique perspective on the regeneration of spent LIB cathodes.

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“…All ripening processes involve a gain of materials at one site (growth) and a loss of materials at another (etching). 14 Plasmon-mediated ripening is known to move Ag from smaller particles to give Ag nano-prisms, driven by the photon energy. Moreover, galvanic exchange is also known to deposit a metal at one site (e.g., the shell layer) with a concurrent etching at another site (the hollow interior), 15 driven by the chemical exchange and a free-flow of electrons.…”

Section: Resultsmentioning

confidence: 99%