Vol 60, No 5 (2024)

The effect of pluronics L61 and F68 with the same length of hydrophobic poly(propylene oxide) blocks and different lengths of hydrophilic poly(ethylene oxide) blocks on the conductivity of planar bilayer lipid membranes made of azolectin was investigated. The integral conductivity of the membranes increases with increasing concentrations of both pluronics. With the same concentration of pluronics in solution, the conductivity for L61 is higher. According to the literature data [24]. At close concentrations of membrane-bound pluronics, membrane conductivities are also close. It was concluded that the appearance of identical hydrophobic parts of pluronics L61 and F68 in the membrane causes the same increase in conductivity in the first approximation. The shape of the conductivity-concentration curves is superlinear for L61 and sublinear for F68. In the presence of both pluronics, conduction spikes with an amplitude from 10 to 300 pSm and higher are observed for approximately 40% of the membranes. We associate the observed surges in conductivity with the appearance of conductive pores or defects in the membrane. The number of pores registered in the membrane was a random variable with a large variance and did not correlate with the concentration of pluronic. The difference between the average pore conductivities for membranes with L61 and F68 was not statistically significant.

The aim of the work was to study the possibility of suppressing the formation of dendrites of metallic lithium during the operation of secondary lithium batteries, including those with a metallic lithium anode. The electrochemical deposition of lithium on copper and lithium substrates in the presence and absence of two surfactants, cetyltrimethylammonium bromide and hexadecylpyridinium bromide was studied by current transient and electrochemical impedance methods. A typical lithium-ion battery electrolyte based on lithium hexafluorophosphate and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) was used. It was shown that the presence of the so-called SEI (solid electrolyte interphase) layer on the electrode surface has a significant effect on the electrodeposition process. It was also shown that the mechanism of lithium electrodeposition on copper and lithium substrates is different. It can be assumed that the observed effect of surfactants on the dendrite formation is associated not with the adsorption of surfactants on lithium and blocking the growth of deposits, but with the effect of surfactants on the properties of the SEI layer formed on these substrates.

In this work, we studied the effect of additions of decahydronaphthalene (decalin) and its derivative, perfluorodecalin (octadecafluorodecalin), on the deposition and dissolution of lithium metal, including dendrite formation, at the anodes of secondary lithium power sources in an electrolyte based on lithium hexafluorophosphate and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). The study was carried out using the methods of current transients and electrochemical impedance. The results showed that, in contrast to traditional cationic surfactants cetyltrimethylammonium bromide and hexadecylpyridinium bromide, which we studied earlier, decalin and perfluorodecalin demonstrate specific interaction with the surface of the lithium electrode. Moreover, the interaction with decalin is so strong that it actually blocks the processes of both deposition and anodic dissolution of lithium at the surface of the lithium electrode. The interaction of perfluorodecalin with the lithium surface turned out to be weaker. As a result, perfluorodecalin does not interfere with the cycling of the metal lithium anode, but at the same time shows an inhibitory effect on the dendrite formation. In the electrolyte with the addition of perfluorodecalin, lithium anode was able to undergo more than 80 charge-discharge cycles with a Coulomb efficiency of 70–80%, while without the additive, the number of cycles was less than 40, and the Coulomb efficiency was 60% or lower.