Supertetrahedral Networks and Lithium‐Ion Mobility in Li₂SiP₂ and LiSi₂P₃

Abstract

The new phosphidosilicates Li SiP and LiSi P were synthesized by heating the elements at 1123 K and characterized by single-crystal X-ray diffraction. Li SiP (I4 /acd, Z=32, a=12.111(1) Å, c=18.658(2) Å) contains two interpenetrating diamond-like tetrahedral networks consisting of corner-sharing T2 supertetrahedra [(SiP ) ]. Sphalerite-like interpenetrating networks of uniquely bridged T4 and T5 supertetrahedra make up the complex structure of LiSi P (I4 /a, Z=100, a=18.4757(3) Å, c=35.0982(6) Å). The lithium ions are located in the open spaces between the supertetrahedra and coordinated by four to six phosphorus atoms. Temperature-dependent Li solid-state MAS NMR spectroscopic data indicate high mobility of the Li ions with low activation energies of 0.10 eV in Li SiP and 0.07 eV in LiSi P .

Synthesis and Structure of the Sodium Phosphidosilicate Na2SiP2

“…The supertetrahedral compounds in the system Na‐Si‐P are rather sodium‐poor and the only known sodium‐rich compound is Na 5 SiP 3 . Therefore we focused on the sodium‐rich part of the system and came across Na 2 SiP 2 which turned out to be structurally quite different from the lithium analogue reported earlier , . Here we report the synthesis, crystal structure, NMR and impedance spectroscopy of Na 2 SiP 2 .…”

“…Fast lithium and sodium ion conductors composed of earth abundant elements as potential components of all solid‐state batteries attract immense interest . Recently, several phosphidosilicates with isolated or condensed SiP 4 tetrahedra have demonstrated lithium or sodium ion conductivity, for example Li 8 SiP 4 , Li 2 SiP 2 ,, LiSi 2 P 3 , and the series Na 23 Si 9 n +19 P 12 n +33 ( n = 0–3) . These compounds have also been studied in the framework of the electrochemical mechanism of SiP 2 /Li anodes , .…”

“…These compounds have also been studied in the framework of the electrochemical mechanism of SiP 2 /Li anodes , . Except Li 8 SiP 4 with isolated [SiP 4 ] 8– tetrahedra, the crystal structures feature networks of interpenetrating T2–T5 supertetrahedra according to the Yaghi notation , , . It was shown that larger supertetrahedral entities favor the ion conductivity by diluting the alkali metal ions between the lower charged clusters .…”

Zn(Cu)Si2+xP3 Solid Solution Anodes for High‐Performance Li‐Ion Batteries with Tunable Working Potentials

“…[22][23][24] Inspired by the desired properties of these materials, we designed and synthesized a new family of cation-disordered ZnSi 2 P 3 of sphalerite structure as advanced anodes for LIBs. [22][23][24] Inspired by the desired properties of these materials, we designed and synthesized a new family of cation-disordered ZnSi 2 P 3 of sphalerite structure as advanced anodes for LIBs.…”

Relevance of solid electrolytes for lithium-based batteries: A realistic view

“…While Li conductivities of 3.5 × 10 −5 S/cm were determined in the dry state, several orders of magnitude higher conductivities were observed when exposed to humid air, albeit at the expense of electrochemical stability [92]. A new family of potentially fast Li solid electrolytes based on phosphidosilicates in the system Li-Si-P was recently discovered by the groups of Johrendt and Fässler [93,94]. Li 2 SiP 2 and LiSi 2 P 3 feature interpenetrating 3D networks of corner-sharing SiP 4 supertetrahedra while the Li ions are located in the cavities and channels of the supertetrahedral networks.…”