Gradient Lithium Metal Infusion in Ag-Decorated Carbon Fibers for High-Capacity Lithium Metal Battery Anodes.

Lithium (Li) metal is a promising anode material for high-energy-density Li batteries due to its high specific capacity. However, the uneven deposition of Li metal causes significant volume expansion and safety concerns. Here, we investigate the impact of a gradient-infused Li-metal anode using silver (Ag)-decorated carbonized cellulose fibers (Ag@CC) as a three-dimensional (3D) current collector. The loading level of the gradient-infused Li-metal anode is controlled by the thermal infusion time of molten Li. In particular, a 5 s infusion time in the Ag@CC current collector creates an appropriate space with a lithiophilic surface, resulting in improved cycling stability and a reduced volume expansion rate. Moreover, integrating a 5 s Ag@CC anode with a high-capacity cathode demonstrates superior electrochemical performance with minimal volume expansion. This suggests that a gradient-infused Li-metal anode using Ag@CC as a 3D current collector represents a novel design strategy for Li-metal-based high-capacity Li-ion batteries.

Acid- and Gas-Scavenging Electrolyte Additive Improving the Electrochemical Reversibility of Ni-Rich Cathodes in Li-Ion Batteries.

In view of their high theoretical capacities, nickel-rich layered oxides are promising cathode materials for high-energy Li-ion batteries. However, the practical applications of these oxides are hindered by transition metal dissolution, microcracking, and gas/reactive compound formation due to the undesired reactions of residual lithium species. Herein, we show that the interfacial degradation of the LiNi0.9CoxMnyAlzO2 (NCMA, x + y + z = 0.1) cathode and the graphite (Gr) anode of a representative Li-ion battery by HF can be hindered by supplementing the electrolyte with tert-butyldimethylsilyl glycidyl ether (tBS-GE). The silyl ether moiety of tBS-GE scavenges HF and PF5, thus stabilizing the interfacial layers on both electrodes, while the epoxide moiety reacts with CO2 released by the parasitic reaction between HF and Li2CO3 on the NCMA surface to afford cyclic carbonates and thus suppresses battery swelling. NCMA/Gr full cells fabricated by supplementing the baseline electrolyte with 0.1 wt % tBS-GE feature an increased capacity retention of 85.5% and deliver a high discharge capacity of 162.9 mAh/g after 500 cycles at 1 C and 25 °C. Thus, our results reveal that the molecular aspect-based design of electrolyte additives can be efficiently used to eliminate reactive species and gas components from Li-ion batteries and increase their performance.

Critical Void Dimension of Carbon Frameworks to Accommodate Insoluble Products of Lithium-Oxygen Batteries.

High-energy density lithium-oxygen batteries (LOBs) seriously suffer from poor rate capability and cyclability due to the slow oxygen-related electrochemistry and uncontrollable formation of lithium peroxide (Li2O2) as an insoluble discharge product. In this work, we accommodated the discharge product in macro-scale voids of a carbon-framed architecture with meso-dimensional channels on the carbon frame and open holes connecting the neighboring voids. More importantly, we found that a specific dimension of the voids guaranteed high capacity and cycling durability of LOBs. The best LOB performances were achieved by employing the carbon-framed architecture having voids of 0.8 µm size as the cathode of the LOB when compared with the cathodes having voids of 0.3 and 1.4 µm size. The optimized void size of 0.8 µm allowed only a monolithic integrity of lithium peroxide deposit within a void during discharging. The deposit was grown to be a yarn ball-looking sphere exactly fitting the shape and size of the void. The good electric contact allowed the discharge product to be completely decomposed during charging. On the other hand, the void space was not fully utilized due to the mass transfer pathway blockage at the sub-optimized 0.3 µm and the formation of multiple deposit integrities within a void at the sur-optimized 1.4 µm. Consequently, the critical void dimension at 0.8 µm was superior to other dimensions in terms of the void space utilization efficiency and the lithium peroxide decomposition efficiency, disallowing empty space and side reactions during discharging.

Amphi-Active Superoxide-Solvating Charge Redox Mediator for Highly Stable Lithium-Oxygen Batteries.

A multifunctional electrolyte additive for lithium oxygen batteries (LOBs) was designed to have (1) a redox-active moiety to mediate decomposition of lithium peroxide (Li2O2 as the final discharge product) during charging and (2) a solvent moiety to solvate and stabilize lithium superoxide (LiO2 as the intermediate discharge product) in electrolyte during discharging. 4-Acetamido-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yl)oxyl) or AAT was employed as the additive working for both charge and discharge processes (amphi-active). The redox-active moiety was rooted in TEMPO, while the acetamido (AA) functional group inherited the high donor number (DN) of N,N-dimethylacetamide (DMAc). Integrating two functional moieties (TEMPO and AA) into a single molecule resulted in the bifunctionality of AAT (1) facilitating Li2O2 decomposition by the TEMPO moiety and (2) encouraging the solvent mechanism of Li2O2 formation by the high-DN AA moiety. Significantly improved LOB performances were achieved by the superoxide-solvating charge redox mediator, which were not obtained by a simple cocktail of TEMPO and DMAc.

Metal-Ion Chelating Gel Polymer Electrolyte for Ni-Rich Layered Cathode Materials at a High Voltage and an Elevated Temperature.

Nickel-rich layered oxides (LiNi1-x-yCoxMnyO2; (1 - x - y) ≥ 0.6), the high-energy-density cathode materials of lithium-ion batteries (LIBs), are seriously unstable at voltages higher than 4.5 V versus Li/Li+ and temperatures higher than 50 °C. Herein, we demonstrated that the failure mechanism of a nickel-rich layered oxide (LiNi0.6Co0.2Mn0.2O2) behind the instability was successfully suppressed by employing cyanoethyl poly(vinyl alcohol) having pyrrolidone moieties (Pyrd-PVA-CN) as a metal-ion-chelating gel polymer electrolyte (GPE). The metal-ion-chelating GPE blocked the plating of transition-metal ions dissolved from the cathode by capturing the ions (anode protection). High-concentration metal-ion environments developed around the cathode surface by the GPE suppressed the irreversible phase transition of the cathode material from the layered structure to the rock-salt structure (cathode protection). Resultantly, the capacity retention was significantly improved at a high voltage and a high temperature. Capacity retention and coulombic efficiency of a full-cell configuration of a nickel-rich layered oxide with graphite were significantly improved in the presence of the GPE especially at a high cutoff voltage (4.4 V) and an elevated temperature (55 °C).

Synergistic effect of quinary molten salts and ruthenium catalyst for high-power-density lithium-carbon dioxide cell.

With a recent increase in interest in metal-gas batteries, the lithium-carbon dioxide cell has attracted considerable attention because of its extraordinary carbon dioxide-capture ability during the discharge process and its potential application as a power source for Mars exploration. However, owing to the stable lithium carbonate discharge product, the cell enables operation only at low current densities, which significantly limits the application of lithium-carbon dioxide batteries and effective carbon dioxide-capture cells. Here, we investigate a high-performance lithium-carbon dioxide cell using a quinary molten salt electrolyte and ruthenium nanoparticles on the carbon cathode. The nitrate-based molten salt electrolyte allows us to observe the enhanced carbon dioxide-capture rate and the reduced discharge-charge over-potential gap with that of conventional lithium-carbon dioxide cells. Furthermore, owing to the ruthernium catalyst, the cell sustains its performance over more than 300 cycles at a current density of 10.0 A g-1 and exhibits a peak power density of 33.4 mW cm-2.

Inhibition of spontaneous and experimental lung metastasis of soft-tissue sarcoma by tumor-targeting Salmonella typhimurium A1-R.

Prognosis of patients with lung metastases of soft-tissue sarcoma is still poor. Therefore, novel systemic therapy is needed to improve the survival of soft-tissue sarcoma. In the present study, tumor-targeting therapy with a genetically-modified auxotrophic strain of Salmonella typhimurium, termed A1-R, was evaluated. Mouse models of primary soft tissue sarcoma and spontaneous lung metastasis were obtained by orthotopic intra-muscular injection of HT1080-RFP human fibrosarcoma cells. S. typhimurium A1-R was administered from day 14, once a week for two weeks. On day 28, lung samples were excised and observed with a fluorescence imaging system. The number of lung metastasis was 8.8 ± 3.4 in the untreated group and 0.8 ± 0.8 in the treated group (P = 0.024). A mouse model of experimental lung metastasis was obtained by tail vein injection of HT1080-RFP cells. The mice were treated with S. typhimurium A1-R (i.v.) on day 7, once a week for three weeks. S. typhimurium A1-R significantly reduced lung metastases and improved overall survival (P = 0.004). S. typhimurium A1-R bacterial therapy has future potential for treating advanced soft tissue sarcoma and improving prognosis of patients with lung metastasis.