TY - JOUR

T1 - Investigation of the Physico-Chemical Properties of Plastic Electrolytes in a Binary System (n-C4H9)4NBF4-(n-C4H9)3CH3NBF4

AU - Stebnitskii, Ivan

AU - Bannykh, Denis

AU - Uvarov, Nikolai

AU - Mateyshina, Yulia

N1 - This study was funded by the Russian Science Foundation, project no. 20-13-00302, https://www.rscf.ru/en.

PY - 2025/1/29

Y1 - 2025/1/29

N2 - A comprehensive study of the influence of (n-C4H9)3CH3NBF4 on the transport properties of (n-C4H9)4NBF4 ─representatives of the class of organic ionic-plastic crystals ─ has been carried out. In pure salts there are several solid-solid phase transitions in the temperature range 25 °C─Tmelting: in (n-C4H9)4NBF4 ─ at 67 °C and Tmelting = 162 °C, and in (n-C4H9)3CH3NBF4 ─ at 56 and 105 °C and Tmelting = 158 °C. According to XRD and DSC data, the introduction of the second salt leads to the stabilization of high-temperature plastic cubic phases (Pm-3n or P-43n) of the salts in the solid solution series at room temperature. Vickers microhardness measurements showed that the high-temperature phases of the salts are characterized by lower Hv values than the low-temperature phases: Hv ((n-C4H9)3CH3NBF4) = 1.7 ± 0.1, which is 5.5 times lower than that of the low-temperature phase. The microhardness of the solid solutions has close values (Hv = 1.4-1.8), which indicates the presence of plasticity of the materials. The conductivity of the solid solutions has a nontrivial character: the increase in conductivity by 0.5-0.7 orders of magnitude is caused by the substitution of large cations (n-C4H9)4N+ by smaller (n-C4H9)3CH3N+, and vice versa by the substitution of small cations by large ones at low dopant concentrations (10 mol %), but high dopant concentrations (more than 10 mol %) led to a decrease in conductivity and the appearance of a minimum on the conductivity isotherms. The obtained concentration dependence of the conductivity can be explained by the opposite influence of two factors:the occurrence of mechanical stresses in the lattice, leading to an increase in the ion mobility, and an increase in the enthalpy of defect formation, leading to a decrease in the conductivity, with the first factor predominating.

AB - A comprehensive study of the influence of (n-C4H9)3CH3NBF4 on the transport properties of (n-C4H9)4NBF4 ─representatives of the class of organic ionic-plastic crystals ─ has been carried out. In pure salts there are several solid-solid phase transitions in the temperature range 25 °C─Tmelting: in (n-C4H9)4NBF4 ─ at 67 °C and Tmelting = 162 °C, and in (n-C4H9)3CH3NBF4 ─ at 56 and 105 °C and Tmelting = 158 °C. According to XRD and DSC data, the introduction of the second salt leads to the stabilization of high-temperature plastic cubic phases (Pm-3n or P-43n) of the salts in the solid solution series at room temperature. Vickers microhardness measurements showed that the high-temperature phases of the salts are characterized by lower Hv values than the low-temperature phases: Hv ((n-C4H9)3CH3NBF4) = 1.7 ± 0.1, which is 5.5 times lower than that of the low-temperature phase. The microhardness of the solid solutions has close values (Hv = 1.4-1.8), which indicates the presence of plasticity of the materials. The conductivity of the solid solutions has a nontrivial character: the increase in conductivity by 0.5-0.7 orders of magnitude is caused by the substitution of large cations (n-C4H9)4N+ by smaller (n-C4H9)3CH3N+, and vice versa by the substitution of small cations by large ones at low dopant concentrations (10 mol %), but high dopant concentrations (more than 10 mol %) led to a decrease in conductivity and the appearance of a minimum on the conductivity isotherms. The obtained concentration dependence of the conductivity can be explained by the opposite influence of two factors:the occurrence of mechanical stresses in the lattice, leading to an increase in the ion mobility, and an increase in the enthalpy of defect formation, leading to a decrease in the conductivity, with the first factor predominating.

KW - Electrical conductivity

KW - Melting

KW - Solutions

KW - Phase transitions

KW - Salts

UR - https://www.mendeley.com/catalogue/d4c89944-5ef8-3ae0-bc1a-dc232de7475b/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85216794037&origin=inward&txGid=76f8cbc8ac05a48519333d6e1f2d6938

U2 - 10.1021/acs.jpcc.4c07086

DO - 10.1021/acs.jpcc.4c07086

M3 - Article

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

ER -