Exploration of tetrahedral structures in silicate cathodes using a motif-network scheme

Abstract

Using a motif-network search scheme, we studied the tetrahedral structures of the dilithium/disodium transition metal orthosilicates A2MSiO4 with A = Li or Na and M = Mn, Fe or Co. In addition to finding all previously reported structures, we discovered many other different tetrahedral-network-based crystal structures which are highly degenerate in energy. These structures can be classified into structures with 1D, 2D and 3D M-Si-O frameworks. A clear trend of the structural preference in different systems was revealed and possible indicators that affect the structure stabilities were introduced. For the case of Na systems which have been much less investigated in the literature relative to the Li systems, we predicted their ground state structures and found evidence for the existence of new structural motifs.

The dielectric relaxation behavior induced by sodium migration in the Na2CoSiO4 structure within a three-dimensional Co–O–Si framework

“…15) and a good electrical conductivity which is reported to be purely ionic. 16 The Na + diffusion indicates a very low activation barrier and a 3D network of diffusion pathways through the SiO 4 and MO 4 frameworks, 17 which both suggest favorable Na + intercalation kinetics.…”

New methods and typical applications of crystal structure prediction

“…针对这个思路, 研究人员通过AGA晶体结构预测以及第一性原理计 算, 系统研究了Fe 3−x Co x C等组分的结构、磁矩和磁晶 各向异性能 [31] . 除了验证已知的Fe 3 C (Pnma)结构之 图 5 (网络版彩图)四面体结构产生的示意图 [36] . 从中心氧 原子出发, 四个最近邻原子随机指定为两个A原子、一个M 原子及一个Si原子; 不断迭代直至四面体结构中的所有位置 均被合理占据 吴福伦等.…”

“…Color online) Schematic drawing of a tetrahedral structure[36]. Starting from a central oxygen atom, the four nearest neighbors are randomly designated as two A atoms, one M atom, and one Si atom.…”

Facile solid-state synthesis of eco-friendly sodium iron silicate with exceptional sodium storage behaviour

“…[15,16] In addition, the high availability of earth-abundant materials such as Fe and Si can help to make Na 2 FeSiO 4 (NFSO) the cheapest energy source available for RSBs. [17] However, NFSO still requires a great deal of attention to enhance its electrochemical performance. Zhang et al initially prepared NFS from Li 2 FeSiO 4 (LFS) using a complex electrochemical ion-exchange (EIE) method and reported two Na-ion extractions from the NFS structure with a discharge capacity of 330 mAh g -1 .…”