Metastable and nanosize cation-disordered rocksalt-type oxides: revisit of stoichiometric LiMnO2 and NaMnO2
Metastable and nanosize cation-disordered rocksalt-type oxides: revisit of stoichiometric LiMnO2 and NaMnO2
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DOI：
10.1039/c8ta03667e
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发表时间：
2018-07
影响因子：
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通讯作者：
Takahito Sato;Kei Sato;Wenwen Zhao;Yoshio Kajiya;N. Yabuuchi
中科院分区：
文献类型：
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作者：
Takahito Sato;Kei Sato;Wenwen Zhao;Yoshio Kajiya;N. Yabuuchi
采用机械球磨的方法成功地制备了具有阳离子无序岩盐型结构的化学计量比LiMnO2和NaMnO2亚稳态晶型。尽管具有化学计量比(Li：Mn摩尔比=1：1)的阳离子无序岩盐相的电化学活性较低，但与热力学稳定的层状相相比，这两种样品作为电极材料在Li/Na电池中表现出更好的性能。这两种亚稳态样品都具有很大的可逆容量，相当于其理论容量的80%，在可逆的Mn3+/Mn4+氧化还原的基础上，极化相对较小。此外，对于岩盐LiMnO2，与热力学稳定相相比，向尖晶石相的相变得到了有效的抑制。亚稳相的使用也大大提高了NaMnO2的电极可逆性，具有良好的容量保持性。具有独特纳米结构的亚稳相为设计高能量密度的先进电极材料开辟了一条新的途径，因此有望在可充电锂/钠电池应用中产生广泛的影响。
Stoichiometric LiMnO2 and NaMnO2 with a cation-disordered rocksalt-type structure as metastable polymorphs were successfully prepared by mechanical milling. Although cation-disordered rocksalt phases with a stoichiometric composition (Li : Mn molar ratio = 1 : 1) are expected to be electrochemically less active, both samples show superior performance as electrode materials when compared with thermodynamically stable layered phases in Li/Na cells. Both metastable samples deliver large reversible capacities, which correspond to >80% of their theoretical capacities, with relatively small polarization on the basis of reversible Mn3+/Mn4+ redox. Moreover, for rocksalt LiMnO2, the phase transition into a spinel phase is effectively suppressed compared with a thermodynamically stable phase. The electrode reversibility of NaMnO2 is also drastically improved by the use of the metastable phase with good capacity retention. Metastable phases with unique nanostructures open a new path for the design of advanced electrode materials with high energy density, and thus a broad impact is anticipated for rechargeable Li/Na battery applications.