Gel polymer electrolytes (GPEs) are emerging as suitable candidates for high-performing lithium-sulfur batteries (LSBs) due to their excellent performance and improved safety. Within them, poly(vinylidene difluoride) (PVdF) and its derivatives have been widely used as polymer hosts due to their ideal mechanical and electrochemical properties. However, their poor stability with lithium metal (Li⁰) anode has been identified as their main drawback. Here, the stability of two PVdF-based GPEs with Li⁰ and their application in LSBs is studied. PVdF-based GPEs undergo a dehydrofluorination process upon contact with the Li⁰. This process results in the formation of a LiF-rich solid electrolyte interphase that provides high stability during galvanostatic cycling. Nevertheless, despite their outstanding initial discharge, both GPEs show an unsuitable battery performance characterized by a capacity drop, ascribed to the loss of the lithium polysulfides and their interaction with the dehydrofluorinated polymer host. Through the introduction of an intriguing lithium salt (lithium nitrate) in the electrolyte, a significant improvement is achieved delivering higher capacity retention. Apart from providing a detailed study of the hitherto poorly characterized interaction process between PVdF-based GPEs and the Li⁰, this study demonstrates the need for an anode protection process to use this type of electrolytes in LSBs.

The growing requirements for electrified applications entail exploring alternative battery systems. Lithium‐sulfur batteries (LSBs) have emerged as a promising, cost‐effective, and sustainable solution; however, their practical commercialization is impeded by several intrinsic challenges. With the aim of surpassing these challenges, the implementation of a holistic LSB concept is proposed. To this end, the effectiveness of coupling a high‐performing 2D graphene‐based sulfur cathode with a well‐suited sparingly solvating electrolyte (SSE) is reported. The incorporation of bis(fluorosulfonyl)imide (LiFSI) salt to tune sulfolane and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropylether based SSE enables the formation of a robust and compact lithium fluoride‐rich solid electrolyte interphase. Consequently, the lithium compatibility is improved, achieving a high Coulombic efficiency (CE) of 98.8% in the Li||Cu cells and enabling thin and dense lithium depositions. When combined with a high‐performing 2D graphene‐based sulfur cathode, a symbiotic effect is shown, leading to high discharge capacities, remarkable rate capability (2.5 mAh cm⁻² at C/2), enhanced cell stability, and wide temperature applicability. Furthermore, the scalability of this strategy is successfully demonstrated by assembling high‐performing monolayer prototype cells with a total capacity of 93 mAh, notable capacity retention of 70% after 100 cycles, and a high average CE of 99%.

Symmetrical cells based on apatite electrolytes show the potential of LaFe_0.8Cu_0.2O₃ as a cathode material for IT applications.

The redox behavior of terbium and praseodymium doped yttria-stabilized zirconia (YSZ) is studied. The aim is to identify spectroscopic probes and a suitable experimental procedure to monitor the oxygen activity in YSZ electrolytes in solid oxide cells with spatial resolution and at operation conditions (e.g. at high temperatures). Sintered ceramics and crystals with 0.3 to 10 at% content of Pr or Tb ions in YSZ were prepared. Upon equilibration in atmospheres from 10⁻²⁰ to 100 bar PO₂ around 800 °C, the majority of these rare earth ions are in the 3 + oxidation state. At oxygen pressures above 0.001 bar, the small proportion of Tb⁴⁺ and Pr⁴⁺ formed give rise to intense optical absorption around 300–500 nm and to decreased reflectance. From the reflectance measurements it is shown that the Tb⁴⁺ concentration increases as PO₂ ^1/4, as correspond to the trapping of the holes generated upon the oxygen incorporation as Tb⁴⁺. This competitive absorption causes a decrease of the Tb³⁺ luminescence. A quantitative relationship of the Tb³⁺ luminescence intensity with PO₂ at 800 °C has been found, which is compatible with the trapping model. The spatial resolution of the experimental procedure could be very roughly estimated of the order of 100 μm.

The purpose of this perspective article is to showcase the different strategies followed in the last years for the integration of graphene into lithium–sulfur batteries. The article will also disclose the limitations and difficulties found out when trying to scale up graphene-based electrodes and their compatibility with novel electrolytes for the development of pre-industrial pouch cells operating under realistic conditions. Representative works and recent results on the use of graphene for Li-S batteries are included to provide context in the path carried out in the last years, underlining every step forward regarding the benefits of using graphene in this technology. Starting with the first graphene integration approaches within the sulfur-based electrodes, addressing the impact of chemical modifications, and going forward with the development of graphene-based binder-free self-standing aerogels and graphene-carbon composites with optimized performances at coin cell level, a complete evaluation of the different initial strategies is carried out. Further on, the efforts are focused on unraveling the synergistic effects of graphene-based electrodes with tuned electrolyte compositions, and finally the strategies to scale-up the systems to prototype pouch cells are also reviewed.