Solid Electrolytes Based on NASICON-Structured Phosphates for Lithium Metal Batteries

Abstract

All-solid-state lithium batteries are a promising alternative to commercially available lithium-ion batteries due to their ability to achieve high energy density, safety, and compactness. Electrolytes are key components of all-solid-state batteries, as they are crucial in determining the batteries’ efficiency. Herein, the structure of LiM2(PO4)3 (M = Ti, Ge, Zr) and lithium-ion migration mechanisms are introduced as well as different synthetic routes and doping (co-doping), and their influence on conductivity is discussed. The effective methods of reducing electrolyte/electrode interface resistance and improving ion-conducting properties are summarized. In addition, different polymer/NASICON composites are considered. The challenges and prospects of practical applications of NASICON-type lithium phosphates as electrolytes for all-solid-state batteries are discussed.

Y-Doped LiZr2(PO4)3 in a PVDF-HFP Composite Electrolyte for Solid-State Li-Metal Batteries

“…Moreover, the mechanical strength of solid electrolytes could suppress the formation of lithium dendrites, allowing the use of the high-specific-capacity lithium metal as the anode in all-solid-state batteries. − Solid electrolytes are broadly classified into three categories based on their composition: solid inorganic electrolytes (SIEs), solid polymer electrolytes (SPEs), and solid composite electrolytes (SCEs). NASICON (Na Super Ionic CONductor)-type inorganic materials are one of the most promising candidates for application as Li-ion conducting solid electrolytes due to their decent ionic conductivity (>10 –5 S cm –1 ) and wide electrochemical stability window (∼5 V). , Hong and Goodenough reported the first NASICON-type compositions with the general formula Na 1+ x Zr 2 Si x P 3– x O 12 (0 ≤ x ≤ 3). , Since then, numerous lithium analogue NASICON-type LiM 2 (PO 4 ) 3 , with M = Zr, Ti, Ge, Sn, etc., compositions have been synthesized with various aliovalent/isovalent substitutions to improve the bottleneck area for Li-ion migration, increase the Li-ion concentration, and suppress the secondary phase formation. ,− Depending on compositions and sintering conditions, NASICON-type LiZr 2 (PO 4 ) 3 (LZP) displays a complex polymorphism with different structures (triclinic, monoclinic, rhombohedral, and orthorhombic). Among these, rhombohedral LZP shows the highest room-temperature (RT) Li-ion conductivity (∼10 –5 S cm –1 ).…”

Recent Strategies for Lithium-Ion Conductivity Improvement in Li7La3Zr2O12 Solid Electrolytes

“…ASSB can work in broader conditions (elevated temperatures, high pressures, and aggressive atmospheres) than traditional lithium-ion power sources with liquid electrolytes [ 6 , 7 , 8 , 9 , 10 ]. The compounds with different structures considered to be lithium-ion solid electrolytes for ASSB are perovskite-type, LISICON-type, NASICON-type, and garnet-like structured solid conductors [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Solid electrolytes based on Li 7 La 3 Zr 2 O 12 (LLZ) with a garnet structure are in great demand.…”

Nafion-212 Membrane Solvated by Ethylene and Propylene Carbonates as Electrolyte for Lithium Metal Batteries

“…Achieving higher energy densities requires the improvement of battery design and the development of new electrochemical energy sources that are not yet widely used. Lithium metal batteries offer the prospect of achieving high energy densities up to 500 Wh/kg due to the lower potential and higher specific capacity of lithium metal compared with the graphite and silicon anodes [1][2][3]. Several issues arise when designing lithium metal batteries, including the growth of Li dendrites, the flammability of liquid electrolytes, and poor electrochemical battery performance [4][5][6].…”