Li₃Co_1.06(1)TeO₆: synthesis, single-crystal structure and physical properties of a new tellurate compound with Co^II/Co^IIImixed valence and orthogonally oriented Li-ion channels

Abstract

A tellurate compound with Co/Co mixed valence states and lithium ions within orthogonally oriented channels was realized in LiCoTeO. The single-crystal structure determination revealed two independent and interpenetrating Li/O and (Co,Te)/O substructures with octahedral oxygen coordination of the metal atoms. In contrast to other mixed oxides, a honeycomb-like ordering of CoO and TeO octahedra was not observed. LiCoTeO crystallizes orthorhombically with the following unit cell parameters and refinement results: Fddd, a = 588.6(2), b = 856.7(2), c = 1781.5(4) pm, R = 0.0174, wR = 0.0462, 608 F values, and 33 variables. Additional electron density in tetrahedral voids in combination with neighboring face-linked and under-occupied octahedral lithium sites offers an excellent possible diffusion pathway for lithium ions. According to the symmetry of the crystal structure the diffusion pathways in LiCoTeO were found in two orthogonal orientations. The Co/Co mixed valence was investigated via X-ray photoelectron spectroscopy (XPS), revealing a composition comparable to that derived from single-crystal X-ray diffractometry. Magnetic susceptibility measurements underlined the coexistence of Co and Co, the title compound, however, showed no magnetic ordering down to low temperatures. The ionic conductivity of LiCoTeO was determined via alternating current (AC) electrochemical impedance spectroscopy and was found to be in the range of 1.6 × 10 S cm at 573 K.

An idealised approach of geometry and topology to the diffusion of cations in honeycomb layered oxide frameworks

“…Honeycomb layered oxides generally can be envisaged to adopt the following compositions of ordered s t r u c t u r e s : A + (A + 3/2 L 3+ 1/6 D 6+ 1/3 O 2 ) , where L can be Zn, Mn, Fe, Co, Cu,Ni, Cr, Mg ; D can be Bi, Te, Sb, Ta, Ir, Nb, W, Sn, Ru, Mo, Os ; A and A * can be alkali atoms (such as Li, Cu, K, Rb, Cs, Ag and Na with A = A * ), transition metal atoms, for instance Cu or noble metal atoms (e.g., Ag, Au, Pd, etc.) [1][2][3][4][5][8][9][10][11][17][18][19][20][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] .…”

“…In fact, there is a correlation between the stacking structure and the resulting electrochemical performance of the honeycomb layered oxides that can be traced to the differing sizes of the cations. For instance, cations with small ionic radii such as tend to form stronger inter-layer bonds as a result of the smaller inter-layer distance 2 , 18 , 22 – 25 , 28 , 30 , 31 , 33 , 37 – 40 . However, has a vastly larger ionic radius with a correspondingly larger inter-layer distance and hence forms weaker inter-layer bonds.…”

Synthesis-Controlled Polymorphism, Magnetic and Electrochemical Properties of Li3Co2SbO6

“…This reinforces the precise synthetic conditions required to control the balance between phases in these systems. More recently, Li3Co1.06TeO6 was reported to crystallise in an orthorhombic Fddd space group with similar unit cell dimensions to other Li3M2M'O6 rock salt-type superstructures, 27 but with Co 2+ and Co 3+ mixed valence states.…”

“…24 Examples of the Fddd phase include Li3M2M'O6 (M = Ni, Co, Mg; M' = Nb, Ta, Sb) and LixMTeO6 (M = Co, Ni; 2 ≤ x ≤ 3). [24][25][26][27] More recently, K + honeycomb tellurates K2M2TeO6 (M = Ni, Mg, Zn, Co and Cu) have been synthesised and studied as rechargeable K-ion battery cathode materials. 28 K2Ni2TeO6 can reversibly insert K + at voltages of ~4 V and has a discharge/charge capacity of ~ 70 mAh g -1 .…”

An Idealised Approach of Geometry and Topology to the Diffusion of Cations in Honeycomb Layered Oxide Frameworks

“…, where L can be Zn, Mn, Fe, Co, Cu,Ni, Cr, Mg ; D can be Bi, Te, Sb, Ta, Ir, Nb, W, Sn, Ru, Mo, Os ; A and A * can be alkali atoms (such as Li, Cu, K, Rb, Cs, Ag and Na with A = A * ), transition metal atoms, for instance Cu or noble metal atoms (e.g., Ag, Au, Pd, etc.) [1][2][3][4][5][8][9][10][11][17][18][19][20][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] .…”