PVDF-HFP Based, Quasi-Solid Nanocomposite Electrolytes for Lithium Metal Batteries.

Composite polymer electrolytes are systems of choice for future solid-state lithium metal batteries (LMBs). Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is among the most interesting matrices to develop new generation quasi-solid electrolytes (QSEs). Here it is reported on nanocomposites made of PVDF-HFP and pegylated SiO2 nanoparticles. Silica-based hybrid nanofillers are obtained by grafting chains of poly(ethylene glycol) methyl ether (PEG) with different molecular weight on the surface of silica nanoparticles. The functionalized nanofiller improves the mechanical, transport and electrochemical properties of the QSEs, which show good ionic conductivity values and high resistance against dendrite penetration, ensuring boosted long and safe device operation. The most promising result is obtained by dispersing 5 wt% of SiO2 functionalized with short PEG chains (PEG750, Mw = 750 g mol-1) in the PVDF-HFP matrix with an ease solvent-casting procedure. It shows ionic conductivity of 0.1 mS cm-1 at 25 °C, more than 250 h resistance to stripping/plating, and impressive results during cycling tests in LMB with LiFePO4 cathode.

Phase-separated solvothermal high yields recovery of lithium and cobalt cathode precursors from end-of-life LiCoO2 lithium-ion batteries.

Lithium-ion batteries (LIBs) recycling is one of the most urgent challenges affecting this technological sector. Indeed, their continuously growing production and demand is already leading to the creation of large volumes of end-of-life LIBs (EoL-LIBs). At the same time, the growing demand for LIBs is not sustainable from the point of view of supply of the critical raw materials needed to produce the essential components of LIBs. The development of efficient and sustainable recycling strategies provides a solution to these two urgent issues. Here we propose a new ternary deep eutectic solvent (DES) composition based on choline chloride, citric acid, and ethylene glycol in molar ratio 1:1:1 for the reductive degradation of LiCoO2 cathode. The optimized leaching process (5g of DES for 100 mg of black mass for 30 min at 140 °C) leads to the full degradation of the cathode with extraction yields above 97% for both Li and Co. Simple electrochemical tests confirm irreversible DES degradation, making its recovery and reuse impractical. We demonstrate that a subsequent thermal treatment, using DES as a sacrificial agent, allows to separate and recover Co3O4 and LiCl with adequate purity to be exploited for LiCoO2 resynthesis. As a proof of concept, a new batch of LiCoO2 is synthesized and used for new cells' assembly. The performance of the resynthesized material is comparable with that of the commercial benchmark material, demonstrating the possibility of a full closed-loop recycling route.