Mechanism of the Na-substituted Spinel Phase Generation in a Li4Ti5O12 Electrode via Sodium-ion Battery Cycling
Mechanism of the Na-substituted Spinel Phase Generation in a Li4Ti5O12 Electrode via Sodium-ion Battery Cycling
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DOI：
10.5796/electrochemistry.18-00029
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发表时间：
2018-01-01
期刊：
影响因子：
2.5
通讯作者：
Kohyama, Masanori
中科院分区：
文献类型：
--
作者：
Kitta, Mitsunori;Kohyama, Masanori
尖晶石钛酸锂（LTO; Li 4 Ti 5 O 12）作为钠离子电池（SIB）的负极材料吸引了很多关注，而Na插入和提取过程中的大体积变化阻碍了LTO基电极的实际应用。期望形成Na取代的LTO相如（Na-3）（8a）（LiTi 5）（16 d）（0 -12）（32 e），由于与Na插入相（Na-6）（16 c）（LiTi 5）（16 d）（0 -12）（32 e）的小体积变化，其预期在SIB中显示出优异的性能，类似于LIB中的无应变LTO电极。在这项工作中，我们已经发现，这种钠取代相是通过放电（钠提取）过程从钠插入的LTO电极形成的，该电极由两个相组成：（Na-6）（16 c）（LiTi 5）（16 d）（O-12）（32 e）和（Li-6）（16 c）（LiTi 5）（16 d）（O-12）（32 e）。Na取代相的产生通过以约10 C速率的高电流密度放电发生，这引起高电化学极化，超过放电电池电压中的Li提取电化学电势。因此，由于Na+和Li+离子的提取作为电化学平衡过程，形成Na取代的LTO相和纯LTO相。本发现是在SIB中的基于LTO的电极的实际应用的重要一步。(c)日本电化学学会，版权所有。
Spinel lithium titanate (LTO; Li4Ti5O12) attracts much attention as a negative electrode material for a sodium-ion battery (SIB), while large volume changes in Na-insertion and extraction processes prevent practical applications of LTO-based electrodes. It is desirable to form a Na-substituted LTO phase as (Na-3)(8a)(LiTi5)(16d)(O-12)(32e), which is expected to show excellent performance in a SIB, due to a small volume change from a Na-inserted phase, (Na-6)(16c)(LiTi5)(16d)(O-12)(32e), analogous to a strain-free LTO electrode in a LIB. In this work, we have discovered that such a Na-substituted phase is really formed via the discharge (Na-extraction) process from a Na-inserted LTO electrode consisting of two phases as (Na-6)(16c)(LiTi5)(16d)(O-12)(32e) and (Li-6)(16c)(LiTi5)(16d)(O-12)(32e). The Na-substituted phase generation occurs by the discharge with a high current density about 10 C rate, which induces high electrochemical polarization, exceeding the Li-extraction electrochemical potential in the discharging cell voltage. Thus both the Na-substituted LTO and pure LTO phases are formed due to the extraction of both Na+ and Li+ ions as an electrochemical equilibrium process. The present finding is a significant step toward practical application of the LTO-based electrode in a SIB. (c) The Electrochemical Society of Japan, All rights reserved.