Importance of lithium power sources is confirmed by the fact that on October 10, 2019, the Nobel Prize in Chemistry in 2019 was awarded for the development of lithium-ion batteries. 10 years earlier, in 2010,physicists Andre Geim and Kostya Novoselov were awarded the Nobel Prize in Physics "For groundbreaking experiments regarding the two dimensional material graphene". A synergistic effect of theory and practicality in the area of lithium batteries, and the theory and practicality in the field of graphene materials creates the unique possibility generate the innovative high-energy Li batteries based on the graphene materials.

Due to the ability of LiFePO4 (LFP) to be charged with large currents, LFP batteries are widely used in household appliances and elect­ric vehicles, so the recycling of spent LFP batteries becomes an urgent need. First, they contain toxic components of electrolyte that cannot be buried in landfills; secondly, the cost of lithium which contains in the electrode material continuously increases, and therefore its return to circulation is profitable and expe­dient. To achieve this goal, much attention is paid to hydrometallurgical processing based on the chemical extraction of Li2CO3 and FePO4 during the regeneration of the electrode material. Here we report on the wet chemistry recycling of used LFP batteries. The main task of the work was to simplify the LiFePO4 regene­ration process by leaching with a solution of citric acid due to the elimination of the stage of isolation of Li2CO3 and FePO4, i.e. without selective separation of the filtrate components. The source of spent LiFePO4 was an industrial lithium iron phosphate battery failed due to an internal short circuit. It was found that using citric acid in the ratio H3Cit:LiFePO4=0.5:1, it is possible to efficiently and quickly separate the electrode material from the aluminum current collector. Further pyrolysis and heat treatment of the citrate solution makes it possible to obtain a high-purity LiFePO4/C composite material without extraneous impurities, except for amorphous carbon, which is formed during the pyrolysis of iron (II) and lithium citrates and the thermal decomposition of the binding material in an inert atmosphere. The specific capacity of the LiFePO4/C composite material recovered by the proposed method (145 mA∙h/g) insignificantly differs from that of commercial analogues. This, in our opinion, indicates good prospects of the lithium-iron phosphate regeneration method proposed in this paper.

The physicochemical properties of graphene and graphene materials obtained by the method of controlled detonation gas synthesis are presented. The fundamental possibility of controlling the graphene and graphene materials physicochemical properties by changing the synthesis conditions is shown. Dynamics of changes in the impedance spectra of Li-S and Li-S-Li batteries with graphene in non-aqueous liquid electrolyte 0.7 M LiIm, 0.25 M LiNO3, DME:DOL (2:1) were studied. The results of electrochemical testing of experimental samples and prototypes of elements of the lithium-sulfur system by the methods of cyclic voltammetry and galvanostatic cycling are presented. The effect of interface stabilization was expressed in a decrease in impedance spectra, an increase in discharge capacity, and more stable long-term cycling with high parameters. The investigation showed a positive effect of graphene materials in the active mass of the multilayered S-based electrode with special design.