Fast ionic conduction in cubic hafnium garnet Li7La3Hf2O12

Abstract

A new member of the family of garnets with fast lithium ion conduction has been found with the composition Li 7 La 3 Hf 2 O 12 . The anion arrangement corresponds to the oxygen framework in garnets, e.g., in Ca 3 Fe 2 Si 3 O 12 . Hafnium is coordinated octahedrally while the lanthanum environment can be described as a distorted cube. Lithium occupies a large number of positions with tetrahedral, trigonal planar, and metaprismatic coordination. Li 7 La 3 Hf 2 O 12 shows a lithium bulk ion conductivity of 2.4 × 10 −4 Ω −1 cm −1 at room temperature with an activation energy of 0.29 eV.

Estimation of the concentration and mobility of mobile Li+ in the cubic garnet-type Li7La3Zr2O12

“…35 The current work is quite different from the previous studies, where we have systematically investigated the true concentration of Li + at various temperatures and estimated the true mobility/ diffusivity of mobile ions. 9,10,21 However, in their studies they have used the value of the total density of Li + , N, as the true concentration of mobile Li + that are involved in the conduction process.…”

Li+ transport properties of W substituted Li7La3Zr2O12 cubic lithium garnets

“…A series of garnet-like solid electrolytes have been reported as a novel family of fast lithium ion conductors by Weppner and his group. [1][2][3][4][5][6][7][8][9][10] Among them, Li 7 La 3 Zr 2 O 12 (LLZ) sintered at 1230 • C reported by Murugan et al has received considerable importance in recent times as result of its high total (bulk + grain boundary) ionic conductivity of 5 × 10 −4 S cm −1 at 25 • C, combined with good chemical stability against lithium metal and commercial electrodes. 5 Li 7 La 3 Zr 2 O 12 (LLZ) exists in tetragonal and cubic phase.…”

Synthesis of cubic Li7La3Zr2O12 by modified sol–gel process

“…In the last few years, a series of garnet-like structural compounds have been investigated as a novel family of fast lithium ion conductors by Weppner and his group [1][2][3][4][5][6][7][8][9][10]. Among them, Li 6 BaLa 2 Ta 2 O 12 and Li 7 La 3 Zr 2 O 12 (LLZ) have been paid much attention because of their stable nature against Li metal [3,5].…”