0428同步年報-2021-全

Neutron Science 083 A Cost-Effective and Humidity-Tolerant Solid Electrolyte for All-Solid-State Lithium Batteries A new cost-effective material as solid electrolyte enables an all-solid-state cell at room temperature with sound performance. S econdary battery research has become a vigorous research field in recent decades. It reflects the increasing demands from portable devices, electric vehicles and the development of renewable energy. The electrolyte is a critical component of batteries and a particular focus of battery research. The solid-state electrolyte materials are critical to realize an all-solid-state battery, which is potentially less flammable, preventing the formation of a solid-electrolyte interphase, increasing cycling performance and strength. Li-ion-conducting chloride solid electrolytes possess effective physicochemical characteristics such as high ionic conductivity, deformability and oxidative stability, but these materials are expensive and commercially uncompetitive. Chen Ma (University of Science and Technology of China, China) and his collaborators report a new chloride solid electrolyte, Li 2 ZrCl 6 , which costs much less than the present chloride solid electrolytes and has an atypical humidity tolerance. Li 2 ZrCl 6 (LZC) was synthesized with a mechanochemical method. A stoichiometric mixture of LiCl and ZrCl 4 was ball-milled for 45 hours to obtain the as-milled LZC, which was treated with annealing at 350 °C. Surprisingly, the ionic conductivity of the LZC decreased by two orders of magnitudes after the annealing treatment, which was explained by an irreversible structural phase transition. The phase transition was studied with both X-ray and neutron diffraction ( WOMBAT ), revealing that the as- milled LZC crystalizes into the α-phase of space group P 3 m ( Fig. 1(a) ) and transforms into the monoclinic β-phase ( C 2/ m ) after heating ( Fig. 1(e) ). An analysis of the bond-valence-site energy (BVSE) was performed to evaluate the ionic conductivities based on the refined crystal-structure models. The BVSE method was employed to locate the positions of Li + ions in the environment of heavy ions Zr +4 and Cl - . The potential exerted on the Li + ion determines the possible distribution of the Li + ion in the lattice. The Li-ion potential isotherm is plotted in Figs. 1 (b) and 1(f) for α-LZC and β-LZC, respectively. The positions of Fig. 1 : BVSE analysis of Li-ion migration within the α-LZC and β-LZC structures. The crystal structures of α-LZC (a) and β-LZC (e) superimposed with the Li-ion potential map. Li-ion migration paths of α-LZC ((b) and (c)) and β-LZC ((f), and (g)). Energy profiles of the migration paths in α-LZC (d) and β-LZC (h). Each path in (b)–(c) and (f)–(g) corresponds to the energy profile of the same color in (d) and (h), respectively. [Reproduced from Ref. 1]