Recycled Tandem Catalysts Promising Ultralow Overpotential Li-CO2 Batteries.

Lithium-carbon dioxide (Li-CO2 ) batteries are regarded as a prospective technology to relieve the pressure of greenhouse emissions but are confronted with sluggish CO2 redox kinetics and low energy efficiency. Developing highly efficient and low-cost catalysts to boost bidirectional activities is craved but remains a huge challenge. Herein, derived from the spent lithium-ion batteries, a tandem catalyst is subtly synthesized and significantly accelerates the CO2 reduction and evolution reactions (CO2 RR and CO2 ER) kinetics with an in-built electric field (BEF). Combining with the theoretical calculations and advanced characterization techniques, this work reveals that the designed interface-induced BEF regulates the adsorption/decomposition of the intermediates during CO2 RR and CO2 ER, endowing the recycled tandem catalyst with excellent bidirectional activities. As a result, the spent electronics-derived tandem catalyst exhibits remarkable bidirectional catalytic performance, such as an ultralow voltage gap of 0.26 V and an ultrahigh energy efficiency of 92.4%. Profoundly, this work affords new opportunities to fabricate low-cost electrocatalysts from recycled spent electronics and inspires fresh perceptions of interfacial regulation including but not limited to BEF to engineer better Li-CO2 batteries.

Hybrid Polymer-Alloy-Fluoride Interphase Enabling Fast Ion Transport Kinetics for Low-Temperature Lithium Metal Batteries.

Low-temperature lithium metal batteries are of vital importance for cold-climate condition applications. Their realization, however, is plagued by the extremely sluggish Li+ transport kinetics in the vicinity of Li metal anode at low temperatures. Different from the widely adopted electrolyte engineering, a functional interphase design concept is proposed in this work to efficiently improve the low-temperature electrochemical reaction kinetics of Li metal anodes. As a proof of concept, we design a hybrid polymer-alloy-fluoride (PAF) interphase featuring numerous gradient fluorinated solid-solution alloy composite nanoparticles embedded in a polymerized dioxolane matrix. Systematic experimental and theoretical investigations demonstrate that the hybrid PAF interphase not only exhibits superior lithiophilicity but also provides abundant ionic conductive pathways for homogeneous and fast Li+ transport at the Li-electrolyte interface. With enhanced interfacial dynamics of Li-ion migration, the as-designed PAF-Li anode works stably for 720 h with low voltage hysteresis and dendrite-free electrode morphology in symmetric cell configurations at -40 °C. The full cells with PAF-Li anode display a commercial-grade capacity of 4.26 mAh cm-2 and high capacity retention of 74.7% after 150 cycles at -20 °C. The rational functional interphase design for accelerating ion-transfer kinetics sheds innovative insights for developing high-areal-capacity and long-lifespan lithium metal batteries at low temperatures.

Correlation between Electrolyte Chemistry and Solid Electrolyte Interphase for Reversible Ca Metal Anodes.

The development of rechargeable Ca metal batteries (RCMBs) is hindered by the Ca2+ passivating solid electrolyte interphases (SEIs). The cation solvation structure dictated by electrolyte chemistry plays a critical role in the SEIs properties. While a relatively weak cation-solvent binding is preferred in Li metal anodes to promote anion-derived SEIs, we demonstrate an enhanced Ca deposition/stripping reversibility under a strong cation-solvent interaction, which is materialized in strongly-solvating solvent and highly-dissociated salt combinations. Such electrolyte formulations benefit the formation of solvent-occupied solvation structure and minimize the anion reduction, resulting in organic-rich/CaF2 -poor SEIs for reversible Ca metal anodes. Furthermore, RCMBs paired with an organic cathode using the optimized electrolytes are demonstrated as a proof-of-concept. Our work reveals the paradigm shift in SEIs design for Ca metal anodes, opening up new opportunities for emerging RCMBs.

First-Principles Insights into Lithium-Rich Ternary Phosphide Superionic Conductors: Solid Electrolytes or Active Electrodes.

Lithium-rich ternary phosphides are recently found to possess high ionic conductivity and are proposed as promising solid electrolytes (SEs) for solid-state batteries. While lithium ions can facilely transport within these materials, their electrochemical and interfacial stability in complex battery setups remain largely uncharacterized. We study the phase stability and electrochemical stability of phosphide-type SEs via first-principles calculations and thermodynamic analysis. Our results indicate that these SEs have intrinsic electrochemical stability windows narrower than 0.5 V. The SEs exhibit low anodic limits of about 1 V vs Li/Li+ due to the oxidation of the electrolytes to form various P binary compounds, indicating the poor electrochemical stability in contact with the cathode. In particular, we find that the thermodynamic driving force of such electrochemical decomposition is critically dependent on the new phases formed at the interfaces. Therefore, these phosphides might not be suitable as electrolytes. Despite the electrochemical instability, further calculations of Li diffusion kinetics show that the Li conduction is highly efficient through face-sharing octahedral and tetrahedral sites with low energy barriers, in spite of the possible variation of the local environments. In addition, an analysis of the terminal decomposition products shows impressive Li storage capacity as high as 2547 mAh·g-1 based on the conversion mechanism, indicating they are capable as high-rate and energy-dense anode materials for battery applications.

Electrochemically-Matched and Nonflammable Janus Solid Electrolyte for Lithium-Metal Batteries.

Solid-state batteries based on ceramic electrolytes are promising alternatives to lithium-ion batteries with better safety and energy density. While solid electrolytes such as the garnet-type Li7La3Zr2O12 (LLZO) are chemically stable with lithium metal, their rigidity leads to poor interfacial contact with the cathodes. Nonflammable organic phosphates, however, are characterized by a liquid nature and can immerse the conventional porous cathodes to form a good contact. However, the phosphates are unstable with lithium metal anodes. We design a quasi-solid Janus electrolyte based on the ceramic LLZO and a trimethyl phosphate (TMP) gel which combines the best of both worlds. The electrochemical window of the Janus electrolyte is significantly extended compared with the TMP to accommodate the lithium metal anode. The contact between the cathode and the electrolyte is maintained by the semifluid nature of the TMP gel. A lithium-metal battery with such a Janus electrolyte can stably cycle at room temperature at 1C while still retaining a capacity of 115 mAh g-1 over 100 times. In contrast, the batteries based on LLZO and TMP individually cannot function properly. More importantly, despite the quasi-solid nature, the battery does not contain flammable functional parts and can alleviate the safety concerns of current batteries containing organic-type electrolytes. This work provides a simple but effective strategy for safe, inexpensive, and energy-dense solid-state batteries.

Synthesis and Electrochemical Performance of NiCO2S4 as Anode for Lithium-Ion Batteries.

NiCO2S4 with different morphology was controllably fabricated by a facile hydrothermal and solvothermal route. The as-obtained samples were analyzed and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results reveal that the sample (NCS-1) prepared by hydrothermal method manifest a mixture of nanorods and nanospheres. The sample (NCS-2) synthesized by solvothermal process takes on spherical nanoparticles (NPs). It is found that the morphology of the sample has much influence on the electrochemical property. When applied as anode for lithium-ion batteries (LIBs), the NiCO2S4 NPs (NCS-2) possess the highest reversible discharge capacity of 1469.8 mAh g-1 compared with other two samples at the current density of 100 mA g-1 in the voltage window of 0.01-3 V. Additionally, it remains a specific capacity of 1163.7 mAh g-1 at a current density of 100 mAg-1 after 100 cycles. This excellent electrochemical performance arises from its unique mesoporous structure, which can reduce the transport lengths of both lithium ions and electrons. The mesoporous NiCO2S4 NPs show the great potential development of high-capacity anode materials for LIBs.

Synthesis of PbS and Ag2S Nanorods via Polyol Process.

PbS and Ag2S nanorods have been synthesized using a polyol process in the presence of poly(vinylpyrrolidone) (PVP). First, the production of Pb or Ag was realized via the thermal decomposition of a lead/silver salt. Then the Pb or Ag precursor was directly combined with S power under heating, leading to the formation of the final products. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). PbS cubes and cubes with a hole in the center were prepared under different reaction conditions. Possible formation mechanisms of different PbS or Ag2S morphologies have briefly been discussed.