The successful development of all-solid-state batteries will provide solutions for many problems facing current Li-ion batteries, such as high flammability, limited energy density, poor cyclability and low cation transference number. In this quest, the development of high-performance solid-state electrolytes is critical. Composite polymer electrolytes (CPE), comprising ionconducting (active) inorganic fillers and polymer matrices, have emerged as a promising strategy to yield better conductivity, interfacial stability, and mechanical strength than their single-phase counterparts. Recent experiments indicate that active garnet fillers may enhance the ionic conductivity of CPEs by inducing anion trapping onto their surface. Moreover, substitutions that modify the lithium molar content within the filler were shown to impact this enhancement. However, the molecular underpinning behind this phenomenon is poorly understood, hindering the development of strategies to exploit it optimally. In this study, we use an enhanced hybrid Monte Carlo technique in combination with extensive molecular dynamics simulations to bridge this gap. By focusing on the archetypal CPE formed by Ga-doped Li 7−3x Ga x La 3 Zr 2 O 12 (Ga x -LLZO) embedded within a poly(ethylene oxide) (PEO) and lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) polymer matrix, we describe how the dynamic electrostatic trapping of anions leads to overall conductivity enhancement by increasing the lithium transference number and tracer diffusivity in the polymer phase. The extent of this enhancement can be fine-tuned by modulating the Li molar content of LLZO through the doping of Ga. We predict an optimal Li molar content of 5.95, which is lower than the optimal 6.50 reported in the literature for single LLZO.

The increasing interest in lithium-oxygen batteries (LOB), having the highest theoretical energy densities among the advanced lithium batteries, has triggered the search for in-situ characterization techniques, including Electrochemical Atomic Force Microscopy (EC-AFM). In this work we addressed the characterization of the formation and decomposition of lithium peroxide (Li2O2) on a carbon cathode using a modified AFM technique, called Flow Electrochemical Atomic Force Microscopy (FE-AFM), where an oxygen-saturated solution of the non-aqueous lithium electrolyte is circulated through a liquid AFM cell. This novel technique does not require keeping the AFM equipment inside a glove-box, and it allows performing a number of experiments using the same substrate with different electrolytes without dissembling the cell. We study the morphology of Li2O2 on graphite carbon using lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) in dimethyl sulphoxide (DMSO) as electrolyte under different operational conditions and compare our results with those reported using other electrolytes and in-situ and ex-situ EC-AFM.

In this work, we perform DFT calculations using the hybrid functional HSE to properly describe the insulating nature of lithium peroxide and study its more energetically favourable surfaces [0001], [1100] and [1120]. We then analyse how the insulating character and the correct description of the hole polarons at the Li 2 O 2 surfaces affect the electrochemical steps of Li 2 O 2 decomposition in the charging process of the Li-O 2 battery. We then study the effect of doping and propose possible scenarios in which the ions as Na + or K + dissolved in the electrolyte can dope and promote Li vacancies generation in the Li 2 O 2 that, in turn, reduce the energy barrier of the limiting steps of the Li 2 O 2 decomposition. The origin of this reduction are the lattice distortions associated with doping that weaken the surface binding.

In a recent paper, He et al. (ChemElectroChem 2014, 1, 2052–2057) described a methodology for measuring out‐of‐cell oxygen diffusivity in lithium–air battery (LAB) cathodes, combining an electrochemical device with a classical gas‐transport model. We will demonstrate here that the authors erroneously assumed that the Knudsen diffusivity of gaseous oxygen in the porous cathode is smaller than the diffusivity in the electrolyte and, consequently, that the oxygen mass transport would limit the current output of the battery. Therefore, it is impossible to determine the oxygen diffusivity in LAB cathodes by using the electrochemical device proposed by the authors, comprising an oxygen pump, the LAB cathode, and an oxygen sensor.