Browsing by Author "Chen, LQ"

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    Correlated migration invokes higher Na+‐ion conductivity in NaSICON‐type solid electrolytes
    (Wiley, 2019-10-01) Zhang, ZZ; Zou, Z; Kaup, K; Xiao, RJ; Shi, S; Avdeev, M; Hu, YS; Wang, D; He, B; Li, H; Huang, XY; Nazar, LF; Chen, LQ
    Na super ion conductor (NaSICON), Na1+nZr2SinP3–nO12 is considered one of the most promising solid electrolytes; however, the underlying mechanism governing ion transport is still not fully understood. Here, the existence of a previously unreported Na5 site in monoclinic Na3Zr2Si2PO12 is unveiled. It is revealed that Na+‐ions tend to migrate in a correlated mechanism, as suggested by a much lower energy barrier compared to the single‐ion migration barrier. Furthermore, computational work uncovers the origin of the improved conductivity in the NaSICON structure, that is, the enhanced correlated migration induced by increasing the Na+‐ion concentration. Systematic impedance studies on doped NaSICON materials bolster this finding. Significant improvements in both the bulk and total ion conductivity (e.g., σbulk = 4.0 mS cm−1, σtotal = 2.4 mS cm−1 at 25 °C) are achieved by increasing the Na content from 3.0 to 3.30–3.55 mol formula unit−1. These improvements stem from the enhanced correlated migration invoked by the increased Coulombic repulsions when more Na+‐ions populate the structure rather than solely from the increased mobile ion carrier concentration. The studies also verify a strategy to enhance ion conductivity, namely, pushing the cations into high energy sites to therefore lower the energy barrier for cation migration. © 2019 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim
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    A customized strategy to design intercalation-type Li-free cathodes for all-solid-state batteries
    (Oxford University Press, 2023-01-10) Wang, D; Yu, J; Yin, X; Shao, S; Li, Q; Wang, YC; Avdeev, M; Chen, LQ; Shi, SQ
    Pairing Li-free transition-metal-based cathodes (MX) with Li-metal anodes is an emerging trend to overcome the energy-density limitation of current rechargeable Li-ion technology. However, the development of practical Li-free MX cathodes is plagued by the existing notion of low voltage due to the long-term overlooked voltage-tuning/phase-stability competition. Here, we propose a p-type alloying strategy involving three voltage/phase-evolution stages, of which each of the varying trends are quantitated by two improved ligand-field descriptors to balance the above contradiction. Following this, an intercalation-type 2H-V1.75Cr0.25S4 cathode tuned from layered MX2 family is successfully designed, which possesses an energy density of 554.3 Wh kg−1 at the electrode level accompanied by interfacial compatibility with sulfide solid-state electrolyte. The proposal of this class of materials is expected to break free from scarce or high-cost transition-metal (e.g. Co and Ni) reliance in current commercial cathodes. Our experiments further confirm the voltage and energy-density gains of 2H-V1.75Cr0.25S4. This strategy is not limited to specific Li-free cathodes and offers a solution to achieve high voltage and phase stability simultaneously. TheAuthor(s) 2023. Published byOxfordUniversity Press on behalf of China Science Publishing&Media Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License
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    Efficient potential-tuning strategy through p-type doping for designing cathodes with ultrahigh energy density
    (Oxford Academic, 2020-07-27) Wang, ZQ; Wang, D; Zou, Z; Song, T; Ni, DX; Li, ZZ; Shao, XC; Yin, WJ; Wang, YC; Luo, WW; Wu, MS; Avdeev, M; Xu, B; Shi, S; Ouyang, CY; Chen, LQ
    Designing new cathodes with high capacity and moderate potential is the key to breaking the energy density ceiling imposed by current intercalation chemistry on rechargeable batteries. The carbonaceous materials provide high capacities but their low potentials limit their application to anodes. Here, we show that Fermi level tuning by p-type doping can be an effective way of dramatically raising electrode potential. We demonstrate that Li(Na)BCF2/Li(Na)B2C2F2 exhibit such change in Fermi level, enabling them to accommodate Li+(Na+) with capacities of 290–400 (250–320) mAh g−1 at potentials of 3.4–3.7 (2.7–2.9) V, delivering ultrahigh energy densities of 1000–1500 Wh kg−1. This work presents a new strategy in tuning electrode potential through electronic band structure engineering. © The Author(s) 2020. Creative Commons CC BY Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.
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    Identifying descriptors for Li+ conduction in cubic Li-argyrodites via hierarchically encoding crystal structure and inferring causality
    (Elsevier, 2021-09-01) Zhao, Q; Zhang, LW; He, B; Ye, AJ; Avdeev, M; Chen, LQ; Shi, S
    Identifying descriptors linked to Li+ conduction enables rational design of solid state electrolytes (SSEs) for advanced lithium ion batteries, but it is hindered by the diverse and confounding descriptors. To address this, by integrating global and local effects of Li+ conduction environment, we develop a generic method of hierarchically encoding crystal structure (HECS) and inferring causality to identify descriptors for Li+ conduction in SSEs. Taking the cubic Li-argyrodites as an example, 32 HECS-descriptors are constructed, encompassing composition, structure, conduction pathway, ion distribution, and special ions derived from the unit cell information. Partial correlation analysis reveals that the smaller anion size plays a significant role in achieving lower activation energy, which results from the competing effects between the lattice space and bottleneck size controlled by framework site disorder. Moreover, the promising candidates are suggested, in which Li6-xPS5-xCl1+x (e.g., Li5.5PS4.5Cl1.5 with the room ionic conductivity of 9.4mS cm−1 and the activation energy of 0.29eV) have been experimentally evaluated as excellent candidates for practical SSEs and the rest are novel compositions waiting for validation. Our work establishes a rational correlation between the HECS-descriptors and Li+ conduction and the proposed approach can be extended to other types of SSE materials. © 2021 Elsevier B.V.
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    Lead-free (Ag,K)NbO3 materials forhigh-performance explosive energy conversion
    (Science Advances, 2020-05-20) Liu, Z; Lu, T; Xue, F; Nie, HC; Withers, RL; Studer, AJ; Kremer, F; Narayanan, N; Dong, XL; Yu, DH; Chen, LQ; Liu, Y; Wang, GS
    Explosive energy conversion materials with extremely rapid response times have broad and growing applications in energy, medical, defense, and mining areas. Research into the underlying mechanisms and the search for new candidate materials in this field are so limited that environment-unfriendly Pb(Zr,Ti)O3 still dominates after half a century. Here, we report the discovery of a previously undiscovered, lead-free (Ag0.935K0.065)NbO3 material, which possesses a record-high energy storage density of 5.401 J/g, enabling a pulse current ~ 22 A within 1.8 microseconds. It also exhibits excellent temperature stability up to 150°C. Various in situ experimental and theoretical investiga-tions reveal the mechanism underlying this explosive energy conversion can be attributed to a pressure-induced octahedral tilt change from a−a−c+ to a−a−c−/a−a−c+, in accordance with an irreversible pressure-driven ferroelectric-antiferroelectric phase transition. This work provides a high performance alternative to Pb(Zr,Ti)O3 and also guidance for the further development of new materials and devices for explosive energy conversion. Copyright © 2020 The Authors. CC-By 4.0 licence
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    Uncovering the potential of M1‐site‐activated NASICON cathodes for Zn‐Ion batteries
    (Wiley, 2020-02-20) Hu, P; Zou, Z; Sun, XW; Wang, D; Ma, J; Kong, QY; Xiao, DD; Gu, L; Zhou, XH; Zhao, JW; Dong, SM; He, B; Avdeev, M; Shi, S; Cui, GL; Chen, LQ
    There is a long‐standing consciousness that the rhombohedral NASICON‐type compounds as promising cathodes for Li+/Na+ batteries should have inactive M1(6b) sites with ion (de)intercalation occurring only in the M2 (18e) sites. Of particular significance is that M1 sites active for charge/discharge are commonly considered undesirable because the ion diffusion tends to be disrupted by the irregular occupation of channels, which accelerates the deterioration of battery. However, it is found that the structural stability can be substantially improved by the mixed occupation of Na+/Zn2+ at both M1 and M2 when using NaV2(PO4)3 (NVP) as a cathode for Zn‐ion batteries. The results of atomic‐scale scanning transmission electron microscopy, analysis of ab initio molecular dynamics simulations, and an accurate bond‐valence‐based structural model reveal that the improvement is due to the facile migration of Zn2+ in NVP, which is enabled by a concerted Na+/Zn2+ transfer mechanism. In addition, significant improvement of the electronic conductivity and mechanical properties is achieved in Zn2+‐intercalated ZnNaV2(PO4)3 in comparison with those of Na3V2(PO4)3. This work not only provides in‐depth insight into Zn2+ intercalation and dynamics in NVP unlocked by activating the M1 sites, but also opens a new route toward design of improved NASICON cathodes. © 1999-2021 John Wiley & Sons, Inc.