Understanding Interfaces at the Positive and Negative Electrodes on Sulfide-Based Solid-State Batteries.

Despite the high ionic conductivity and attractive mechanical properties of sulfide-based solid-state batteries, this chemistry still faces key challenges to encompass fast rate and long cycling performance, mainly arising from dynamic and complex solid-solid interfaces. This work provides a comprehensive assessment of the cell performance-determining factors ascribed to the multiple sources of impedance from the individual processes taking place at the composite cathode with high-voltage LiNi0.6Mn0.2Co0.2O2, the sulfide argyrodite Li6PS5Cl separator, and the Li metal anode. From a multiconfigurational approach and an advanced deconvolution of electrochemical impedance signals into distribution of relaxation times, we disentangle intricate underlying interfacial processes taking place at the battery components that play a major role on the overall performance. For the Li metal solid-state batteries, the cycling performance is highly sensitive to the chemomechanical properties of the cathode active material, formation of the SEI, and processes ascribed to Li diffusion in the cathode composite and in the space-charge layer. The outcomes of this work aim to facilitate the design of sulfide solid-state batteries and provide methodological inputs for battery aging assessment.

Towards lithium-free solid-state batteries with nanoscale Ag/Cu sputtered bilayer electrodes.

Enhancing the reversible Li growth efficiency in "Li-free" solid-state batteries is key for the deployment of this technology. Here, we demonstrate a nanoscale material design path that enables the reversible cycling of a lithium-free solid-state battery, using Li7La3Zr2O12 (LLZO) electrolyte. By means of nanometric Ag-Cu bilayers, directly sputtered onto the LLZO, we can effectively control Li deposition. The robust thin film bilayer, which is compatible with LLZO, enables stable cycling, accommodating the volume changes without the need for extra external pressure.

Selection and Surface Modifications of Current Collectors for Anode-Free Polymer-Based Solid-State Batteries.

Anode-free batteries (AFB) have attracted increasing interest in recent times because they allow the elimination of the conventional anode from the cell, exploiting lithium inventory from a lithiated cathode. This implies a much simpler, cost-effective, and sustainable approach. The AFB configuration with liquid electrolytes is being explored widely in research but rarely using solid electrolytes. One of the main issues of AFB is the poor reversibility of the lithium-plating/striping process at the anode side. Therefore, in this work, different metal foils have been tested as anode current collectors (CC), and copper foil has been selected as the most promising one. Surface modifications of the selected copper foil have been achieved by its coating using composite layers made of carbon and different metal nanoparticles-such as Ag, Sn, or Zn-in different proportions and with different amounts of a binder. The impact of such coatings and their thickness on the electrochemical performance of single-layer solid-state anode-free pouch cells, based on a PEO electrolyte and a LiFePO4 cathode has been systematically studied. Consequently, a post-mortem analysis of the investigated solid-state AFB is also presented, trying to identify and elucidate possible failure mechanisms to enhance the electrochemical performance of solid-state AFB in the future.

Designing Spinel Li4Ti5O12 Electrode as Anode Material for Poly(ethylene)oxide-Based Solid-State Batteries.

The development of a promising Li metal solid-state battery (SSB) is currently hindered by the instability of Li metal during electrodeposition; which is the main cause of dendrite growth and cell failure at elevated currents. The replacement of Li metal anode by spinel Li4Ti5O12 (LTO) in SSBs would avoid such problems, endowing the battery with its excellent features such as long cycling performance, high safety and easy fabrication. In the present work, we provide an evaluation of the electrochemical properties of poly(ethylene)oxide (PEO)-based solid-state batteries using LTO as the active material. Electrode laminates have been developed and optimized using electronic conductive additives with different morphologies such as carbon black and multiwalled carbon nanotubes. The electrochemical performance of the electrodes was assessed on half-cells using a PEO-based solid electrolyte and a lithium metal anode. The optimized electrodes displayed an enhanced capability rate, delivering 150 mAh g-1 at C/2, and a stable lifespan over 140 cycles at C/20 with a capacity retention of 83%. Moreover, postmortem characterization did not evidence any morphological degradation of the components after ageing, highlighting the long-cycling feature of the LTO electrodes. The present results bring out the opportunity to build high-performance solid-state batteries using LTO as anode material.

Solid-State Li-Ion Batteries Operating at Room Temperature Using New Borohydride Argyrodite Electrolytes.

Using a new class of (BH4)- substituted argyrodite Li6PS5Z0.83(BH4)0.17, (Z = Cl, I) solid electrolyte, Li-metal solid-state batteries operating at room temperature have been developed. The cells were made by combining the modified argyrodite with an In-Li anode and two types of cathode: an oxide, LixMO2 (M = ⅓ Ni, ⅓ Mn, ⅓ Co; so called NMC) and a titanium disulfide, TiS2. The performance of the cells was evaluated through galvanostatic cycling and Alternating Current AC electrochemical impedance measurements. Reversible capacities were observed for both cathodes for at least tens of cycles. However, the high-voltage oxide cathode cell shows lower reversible capacity and larger fading upon cycling than the sulfide one. The AC impedance measurements revealed an increasing interfacial resistance at the cathode side for the oxide cathode inducing the capacity fading. This resistance was attributed to the intrinsic poor conductivity of NMC and interfacial reactions between the oxide material and the argyrodite electrolyte. On the contrary, the low interfacial resistance of the TiS2 cell during cycling evidences a better chemical compatibility between this active material and substituted argyrodites, allowing full cycling of the cathode material, 240 mAhg-1, for at least 35 cycles with a coulombic efficiency above 97%.

A new method using compressed CO2 for the in situ functionalization of mesoporous silica with hyperbranched polymers.

The present work focuses on the development of a new eco-efficient method, based on the use of compressed CO2 as a solvent, reaction medium and catalyst, for the in situ polymerization of ethyleneimine inside mesoporous silica.