ИСТИНА

Development of electronic devices and electric vehicles requires further development of rechargeable electrochemical cells. Lithium metal is the most desirable anode material for next generation lithium-sulfur and lithium-air batteries and for improvement of modern lithium-ion cells because it has the highest theoretical capacity (3860 mAh/g) and lowest electrochemical potential. However, lithium often demonstrates filamentary growth during its electrochemical deposition accompanying battery charge. It lead to irreversible capacity loss due to delamination of non-uniform deposits known as “dendrites” from the electrode surface, and also to safety problems which can be caused by short circuits. This all hinder the use of metal lithium as anode material for secondary cells. Lithium metal electrode has been developed since 1960s. Various approaches to suppress dendrite growth are suggested, but stable and safe Li metal anode is still a challenge. Dendrite formation during electrodeposition is rather complicated process and can’t be studied by solely electrochemical techniques. For this reason various additional analytic techniques are used. They include both in situ (optical microscopy, SEM, NMR, holography, etc.) and ex situ (SEM, AFM, XPS etc.) approaches. Most of them, however, provide only local information about surface or don’t have enough spatial resolution to detect smallest changes in surface morphology, which can shed the light on the dendrite growth reasons and mechanisms. The novel way to deal with dendrite issue is to utilize special electrolyte additives. This approach is based on using non-electroactive cations to electrolyte solution in order to screen electrostatic field, which is one of possible reasons of dendrite formation. Recently our group suggested using thetrabutylammonium (TBA+) cations as such additives. Its effectivity was already probed with various electrochemical and microscopic methods. However, mentioned above shortcomings of this methods doesn’t let us clearly determine effectivity of this approach. We have designed electrochemical cell for operando neutron reflectometry studies of lithium electrodeposition. Neutron reflectometry lets us to avoid problems of commonly used techniques because it can be conducted in situ, has good spatial resolution and most important collects averaged data over all electrode, providing qualitative characteristics of deposits. Combined with electrochemical techniques and various ex situ techniques it can give a new way of observing the effect of various approaches. We have conducted preliminary experiments on IBR-2, JINR, Dubna. It has shown that neutron reflectometry allows us to spot solid electrolyte interphase layer and determine deposited lithium layer thickness and morphology.