ORALS

We are facing big challenges in developing full-solid Li/Na ion batteries concerning the limited performances and problems of electrodes and solid electrolytes. There are, however, potential possibilities to overcome these challenges. In this presentation, we demonstrate a different route, that is, our disorder/ordering engineering concept [1] to develop high performance cathode/anode/electrolyte materials. The disorder/order engineering refers to two aspects. First, part of the disordered or glass structure in cathode/anode materials is transformed into the ordered domains. Second, the long-range ordered solids are transformed into disordered or amorphous ones. In this talk, we present three case studies concerning the effect of the disorder/order engineering on the electrochemical performances of cathodes, anodes, and solid electrolytes, respectively, for Li/Na-ion batteries. <br />Case 1: A series of vanadium-tellurite glasses with various V/Te ratios were synthesized via melt-quenching [1,2]. Then, the glass was pulverized and mixed with carbon to make Li-ion battery anodes. The anodes underwent discharging/charging cycles. During cycling, a fascinating phenomenon was observed, i.e., nanocrystals formed in glass matrix. As a consequence, the cycling stability and electronic/ionic conductivity of the anodes were enhanced. This kind of nanocrystal formation has a fundamentally different origin compared to the thermally induced crystallization [1,3].<br />Case 2: NaFePO₄ with maricite structure, which is a thermodynamically stable phase, was considered to be electrochemically inactive for sodium-ion storage. Recently, we succeeded in creating disorder in the NaFePO4 cathode by a mechanochemical route to enhance electrochemical performances of Na-ion batteries [4]. The derived NaFePO₄ cathodes containing both amorphous and maricite phases exhibit much improved sodium storage performance with an initial capacity of 115 mA h g^-1 at 1 C and an excellent cycling stability of capacity retention of 91.3% after 800 cycles.<br />Case 3: The crystalline Ag₃PS₄ was transformed into amorphous state via a chemo-mechanical milling process. The Ag⁺ conductivity of the amorphous sample was found to be about three orders of magnitude higher than that of the crystalline counterpart. The amorphous sample exhibits lower activation energy (<i>E</i>_a) for the Ag⁺ migration, and hence, lower Ag+ conductivity compared to the crystalline one. By performing structural characterizations, we explored the origin of the enhanced Ag⁺ conductivity of the amorphous sample. The present study provides valuable information for developing solid electrolytes.

References:
1. Y.F. Zhang, P.X. Wang, T. Zheng, D.M. Li, G.D. Li, Y.Z. Yue. Enhancing Li-ion battery anode performances via disorder/order engineering. Nano Energy 49 (2018) 596-602.\n2. J. Kjeldsen, Y.Z. Yue, C.B. Bragatto, A.C.M. Rodrigues. Electronic Conductivity of Vanadium-Tellurite Glass-Ceramics. J. Non-Cryst. Solids 378 (2013) 196-200.\n3. Y.F. Zhang, P.X. Wang, G.D. Li, J.H. Fan, C.W. Gao, Z.Y. Wang, Y.Z. Yue, Clarifying the charging induced nucleation in glass anode of Li-ion batteries and its enhanced performances, Nano Energy 57 (2019) 592-599.\n4. F.Y. Xiong, Q.Y. An, L.X. Xia, Y.Zhao, L.Q. Mai, H.Z. Tao, Y.Z. Yue, Revealing the atomistic origin of the disorder-enhanced Na-storage performance in NaFePO₄ battery cathode, Nano Energy 57 (2019) 608-615.