The Role of the Reducible Dopant in Solid Electrolyte-Lithium Metal Interfaces

Garnet solid electrolytes, of the form Li7La3Zr2O12 (LLZO), remain an enticing prospect for solid-state batteries owing to their chemical and electrochemical stability in contact with metallic lithium. Dopants, often employed to stabilize the fast ion conducting cubic garnet phase, typically have no effect on the chemical stability of LLZO in contact with Li metal but have been found recently to impact the properties of the Li/garnet interface. For dopants more “reducible” than Zr (e.g., Nb and Ti), contradictory reports of either raised or reduced Li/garnet interfacial resistances have been attributed to the dopant. Here, we investigate the Li/LLZO interface in W-doped Li7La3Zr2O12 (LLZWO) to determine the influence of a “reducible” dopant on the electrochemical properties of the Li/garnet interface. Single-phase LLZWO is synthesized by a new sol–gel approach and densified by spark plasma sintering. Interrogating the resulting Li/LLZWO interface/interphase by impedance, muon spin relaxation and X-ray absorption spectroscopies uncover the significant impact of surface lithiation on electrochemical performance. Upon initial contact, an interfacial reaction occurs between LLZWO and Li metal, leading to the reduction of surface W6+ centers and an initial reduction of the Li/garnet interfacial resistance. Propagation of this surface reaction, driven by the high mobility of Li+ ions through the grain surfaces, thickens the resistive interphases throughout the material and impedes Li+ ion transport between the grains. The resulting high resistance accumulating in the system impedes cycling at high current densities. These insights shed light on the nature of lithiated interfaces in garnet solid electrolytes containing a reducible dopant where high Li+ ion mobility and the reducible nature of the dopant can significantly affect electrochemical performance

A facile synthetic approach to nanostructured Li2S cathodes for rechargeable solid-state Li–S batteries

Li–S solid state batteries, employing Li2S as a pre-lithiated cathode, present a promising low cost, high capacity and safer alternative to their liquid electrolyte counterparts, where dissolution of intermediate polysulfide species can result in loss of active material and a subsequent decrease in ionic conductivity. A nanostructured Li2S material would afford greater flexibility in optimising the cathode composite for more harmonious electrode–electrolyte interactions, yet facile routes to such nanoscale materials are limited. Here, we report a facile and scalable microwave approach to directly synthesize nanostructured Li2S from a glyme solution containing lithium polysulfides. As-synthesized Li2S presents an ideal architecture for the construction of free-standing cathodes for all-solid-state Li–S batteries

2020 roadmap on solid-state batteries

Li-ion batteries have revolutionized the portable electronics industry and empowered the electric vehicle (EV) revolution. Unfortunately, traditional Li-ion chemistry is approaching its physicochemical limit. The demand for higher density (longer range), high power (fast charging), and safer EVs has recently created a resurgence of interest in solid state batteries (SSB). Historically, research has focused on improving the ionic conductivity of solid electrolytes, yet ceramic solids now deliver sufficient ionic conductivity. The barriers lie within the interfaces between the electrolyte and the two electrodes, in the mechanical properties throughout the device, and in processing scalability. In 2017 the Faraday Institution, the UK's independent institute for electrochemical energy storage research, launched the SOLBAT (solid-state lithium metal anode battery) project, aimed at understanding the fundamental science underpinning the problems of SSBs, and recognising that the paucity of such understanding is the major barrier to progress. The purpose of this Roadmap is to present an overview of the fundamental challenges impeding the development of SSBs, the advances in science and technology necessary to understand the underlying science, and the multidisciplinary approach being taken by SOLBAT researchers in facing these challenges. It is our hope that this Roadmap will guide academia, industry, and funding agencies towards the further development of these batteries in the future

Synthesis and characterization of cobalt-containing perovskite-type oxides

A number of cobalt-containing perovskite-type oxides were synthesized and characterized in this study. All materials were half-doped with cobalt in their B-sites, i.e. contain the Co0.5M0.5 B-site state where M = Fe, Mn, Cr, Ni; the materials adopted single layered, double-layered and simple perovskite-type structures. The materials La2 xSrxCo0.5M0.5O4 (M = Fe, Cr) have shown enhanced stability under reducing conditions (10% H2/N2, up to 1000 ºC) with the formation of oxygen deficient compounds, while no evidence for oxygen hyperstoichiometry was observed under oxidizing conditions. Materials such La1.2Sr0.8Co0.5Mn0.5O4.1 and La1.7Sr0.3Co0.5Ni0.5O4.08, however, exhibit oxygen hyperstoichiometry under oxidizing conditions and also withstand reducing conditions via formation of oxygen deficiency. Oxygen vacancies were disordered and confined to the equatorial planes of the single layered structure in all materials, while oxygen hyperstoichiometry was accommodated in the interstitial (0, 0 .5, 0.25) sites of the tetragonal structure. In La1+xSr2 xCoMnO7-δ, oxygen vacancies were confined to the common apex of the double layered structure. The new brownmillerite phase LaSrCoFeO5 was synthesized and fluorination produced the new oxyfluoride LaSrCoFeO5F. Magnetic interactions between Co2+(3+) ions and ions such as Fe3+, Mn3+, Cr3+, Ni2+ in different perovskite-type structures were also studied and a range of magnetically ordered materials, at low and room temperatures, were investigated

Structural and Magnetic Characterization of La_1+xSr_1-xCo_0.5M_0.5O_4±δ (M=Cr, Mn)

International audienceThe K2NiF4 phases La1+xSr1-xCo0.5Cr0.5O4±δ (x=0, 0.15) and La1+xSr1-xCo0.5Mn0.5O4±δ (x=0, 0.2) have been synthesised and examined by X-ray powder diffraction, thermal analysis, neutron powder diffraction and magnetic susceptibility measurements. Mn3+/Co3+ and Cr3+/Co3+ states predominate in the oxidised forms. Structural stability and crystal symmetry are retained under reducing conditions which cause reduction of Co3+ into Co2+ and the creation of oxide ion vacancies within the equatorial planes of the K2NiF4 structure. Excess oxygen in La1.2Sr0.8Co0.5Mn0.5O4.1 is accommodated in the ideal interstitial positions (0, 0.5, 0.25) of the tetragonal structure. these materials depending upon the atmosphere applied. No long-range magnetic order has been observed because of competing AFM and FM interactions in these B-site disordered materials

FeO_<i>x</i>‑Coated SnO₂ as an Anode Material for Lithium Ion Batteries

Nanostructured iron oxide is coated on commercial SnO₂ nanoparticles via a simple solution route. The method involves the thermal decomposition of an iron carbonyl complex (Fe­(CO)₅) in the presence of SnO₂ and a surfactant in an organic solvent. The resulting FeO_<i>x</i>/SnO₂ nanocomposite showed an enhanced performance as an anode material for lithium ion batteries. In a conventional electrolyte containing 5 wt % fluoroethylene carbonate (FEC), a composite FeO_<i>x</i>/SnO₂ (∼1:3 mol ratio) exhibited a stable capacity ∼480 mAh/g (at a rate of 400 mA/g) for up to 150 cycles compared with <130 mAh/g for bare SnO₂. The enhanced cycle performance of FeO_<i>x</i>/SnO₂ is attributed to (i) the in situ formation of electronically conductive nanostructured Fe/Li₂O matrix and (ii) the formation of better-preserved solid–electrolyte interface in the presence of FEC

Liquid-Phase Approach to Glass-Microfiber-Reinforced Sulfide Solid Electrolytes for All-Solid-State Batteries

Deformable, fast-ion conducting sulfides enable the construction of bulk-type solid-state batteries that can compete with current Li-ion batteries in terms of energy density and scalability. One approach to optimizing the energy density of these cells is to minimize the size of the electrolyte layer by integrating the solid electrolyte in thin membranes. However, additive-free thin membranes, as well as many membranes based on preprepared scaffolds, are difficult to prepare or integrate in solid cells on a large scale. Here, we propose a scalable solution-based approach to produce bulk-type glass-microfiber-reinforced composites that restore the deformability of sulfide electrolytes and can easily be shaped into thin membranes by cold pressing. This approach supports both the ease of preparation and enhancement of the energy density of sulfide-based solid-state batteries