Lithium (Li) dendrite formation is one of the major hurdles limiting the development of Li-metal batteries, including Li-O batteries. Herein, we report the first observation of the dendrite-free epitaxial growth of a Li metal up to 10-μm thick during charging (plating) in the LiBr-LiNO dual anion electrolyte under O atmosphere. This phenomenon is due to the formation of an ultrathin and homogeneous Li O-rich solid-electrolyte interphase (SEI) layer in the preceding discharge (stripping) process, where the corrosive nature of Br seems to give rise to remove the original incompact passivation layer and NO oxidizes (passivates) the freshly formed Li surface to prevent further reactions with the electrolyte. Such reactions keep the SEI thin (<100 nm) and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process.

A fundamental obstacle in systemic therapy for cancer patients is the specific targeting of therapy directly to solid tumors. A strain of the domestic bacterium Bifidobacterium longum, which is non-pathogenic and anaerobic, showed selective localization to and proliferation within solid tumors after systemic application. Here, we propose a novel approach to cancer gene therapy in which anaerobic and non-pathogenic bacteria of the genus B. longum are used to achieve tumor-specific gene delivery and enzymeprodrug therapy. We constructed a plasmid, pBLES100-S-eCD, which included eCD. Transfected B. longum produced CD in hypoxic tumors and achieved tumor site-specific conversion of 5-FC to 5-FU. Furthermore, we demonstrated antitumor efficacy in rat bearing autochthonous mammary tumors injected with the transfected B. longum directly or intravenously. This method was confirmed to be effective for enzyme-prodrug therapy not only by intratumoral injection but also by systemic administration. To estimate the toxicity of this bacterial vector, the systemic immunogenicity was evaluated by ASA reaction and the anaphylactic activity of IgG was evaluated by PCA reaction in guinea pigs. In the ASA reaction, no anaphylaxis symptoms were observed in any immunized guinea pigs injected with transfected B. longum. In the PCA reaction, B. longum/S-eCD specific-PCA-induced antibody was not detected. Thus, we proposed that anaerobic bacteria of the genus B. longum were an attractive and safe tumor-targeting vector and transfected B. longum was a potential anticancer agent that could effectively and specifically treat solid tumors. (Cancer Sci 2006; 97: 649-657)

The main issues with Li-O batteries are the high overpotential at the cathode and the dendrite formation at the anode during charging. Various types of redox mediators (RMs) have been proposed to reduce the charging voltage. However, the RMs tend to lose their activity during cycling owing to not only decomposition reactions but also undesirable discharge (shuttle effect) at the Li metal anode. Moreover, the dendrite growth of the Li metal anode is not resolved by merely adding RMs to the electrolytes. Here we report a simple yet highly effective method to reduce the charge overpotential while protecting the Li metal anode by incorporating LiBr and LiNO in a tetraglyme solvent as the electrolyte for Li-O cells. The Br/Br couple acts as an RM to oxidize the discharge product LiO at the cathode, whereas the NO anion oxidizes the Li metal surface to prevent the shuttle reaction. In this work, we found that both anions work synergistically in the mixed Br/NO electrolyte to dramatically suppress both parasitic reactions and dendrite formation by generating a solid LiO thin film on the Li metal anode. As a result, the charge voltage was reduced to below 3.6 V over 40 cycles. The O evolution during charging was more than 80% of the theoretical value, and CO emission during charging was negligible. After cycling, the Li metal anode showed smooth surfaces with no indication of dendrite formation. These observations clearly demonstrate that the Br/NO dual-anion electrolyte can solve the problems associated with both the overpotential at the cathode and the dendrite formation at the anode.

Nano-structured silicon is an attractive alternative anode material to conventional graphite in lithium-ion batteries. However, the anode designs with higher silicon concentrations remain to be commercialized despite recent remarkable progress. One of the most critical issues is the fundamental understanding of the lithium–silicon Coulombic efficiency. Particularly, this is the key to resolve subtle yet accumulatively significant alterations of Coulombic efficiency by various paths of lithium–silicon processes over cycles. Here, we provide quantitative and qualitative insight into how the irreversible behaviors are altered by the processes under amorphous volume changes and hysteretic amorphous–crystalline phase transformations. Repeated latter transformations over cycles, typically featured as a degradation factor, can govern the reversibility behaviors, improving the irreversibility and eventually minimizing cumulative irreversible lithium consumption. This is clearly different from repeated amorphous volume changes with different lithiation depths. The mechanism behind the correlations is elucidated by electrochemical and structural probing.

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