Journal
ADVANCED MATERIALS
Volume 32, Issue 14, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.201907526
Keywords
cathode materials; NASICON; occupation mechanism; Zn-ion batteries
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Funding
- National Natural Science Foundation of China [11874254, 51802187, 21975271]
- National Key R&D Program of China [2018YFB0104300]
- Shanghai Sailing Program [18YF1408700]
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDA22010603]
- 135 Projects Fund of CAS-QIBEBT Director Innovation Foundation
- Qingdao Key Lab of Solar Energy Utilization and Energy Storage Technology
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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.
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