Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications 1-3. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. Here we report that disordered rock salt 4,5 Li3+xV2O5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li + reference electrode. The increased potential compared to graphite 6,7 reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li3V2O5 anode yields a cell voltage much higher than does a battery using a commercial fastcharging lithium titanate anode or other intercalation anode candidates (Li3VO4 and LiV0.5Ti0.5S2) 8,9. Further, disordered rock salt Li3V2O5 can perform over 1,000 charge-discharge cycles with negligible capacity decay and exhibits exceptional rate capability, delivering over 40 per cent of its capacity in 20 seconds. We attribute the low voltage and high rate capability of disordered rock salt Li3V2O5 to a redistributive lithium intercalation mechanism with low energy barriers revealed via ab initio calculations. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries.

Riboswitches are structural elements in the 5′ untranslated regions of many bacterial messenger RNAs that regulate gene expression in response to changing metabolite concentrations by inhibition of either transcription or translation initiation. The preQ1 (7-aminomethyl-7-deazaguanine) riboswitch family comprises some of the smallest metabolite sensing RNAs found in nature. Once ligand-bound, the transcriptional Bacillus subtilis and translational Thermoanaerobacter tengcongensis preQ1 riboswitch aptamers are structurally similar RNA pseudoknots; yet, prior structural studies have characterized their ligand-free conformations as largely unfolded and folded, respectively. In contrast, through single molecule observation, we now show that, at near-physiological Mg2+ concentration and pH, both ligand-free aptamers adopt similar pre-folded state ensembles that differ in their ligand-mediated folding. Structure-based Gō-model simulations of the two aptamers suggest that the ligand binds late (Bacillus subtilis) and early (Thermoanaerobacter tengcongensis) relative to pseudoknot folding, leading to the proposal that the principal distinction between the two riboswitches lies in their relative tendencies to fold via mechanisms of conformational selection and induced fit, respectively. These mechanistic insights are put to the test by rationally designing a single nucleotide swap distal from the ligand binding pocket that we find to predictably control the aptamers′ pre-folded states and their ligand binding affinities.

As a typical transition metal dichalcogenide, MoS offers numerous advantages for nanoelectronics and electrochemical energy storage due to its unique layered structure and tunable electronic properties. When used as the anode in lithium-ion cells, MoS undergoes intercalation and conversion reactions in sequence upon lithiation, and the reversibility of the conversion reaction is an important but still controversial topic. Here, we clarify unambiguously that the conversion reaction of MoS is not reversible, and the formed LiS is converted to sulfur in the first charge process. LiS/sulfur becomes the main redox couple in the subsequent cycles and the main contributor to the reversible capacity. In addition, due to the insulating nature of both LiS and sulfur, a strong relaxation effect is observed during the cycling process. This study clearly reveals the electrochemical lithiation-delithiation mechanism of MoS, which can facilitate further developments of high-performance MoS-based electrodes.

We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states of warm dense copper that is produced isochorically through the absorption of an ultrafast optical pulse. The temperature of the superheated electron-hole plasma, which ranges from 4000 to 10 000 K, was determined by comparing the measured x-ray absorption spectrum with a simulation. The electronic structure of warm dense copper is adequately described with the high temperature electronic density of state calculated by the density functional theory. The dynamics of the electron temperature is consistent with a two-temperature model, while a temperature-dependent electron-phonon coupling parameter is necessary.

LiNO 3 has been widely used as an effective electrolyte additive in lithium-sulfur (Li-S) batteries to suppress the polysulfide shuttle effect. To better understand the mechanism of suppressed shuttle effect by LiNO 3 , herein we report a comprehensive investigation of the influence of LiNO 3 additive on the formation process of the solid electrolyte interphase (SEI) layer on lithium anode of Li-S batteries by operando X-ray absorption spectroscopy (XAS). We observed that a compact and stable SEI layer composed of Li 2 SO 3 and Li 2 SO 4 on top of lithium anode is formed during the initial discharge process due to the synergetic effect of shuttled polysulfides and LiNO 3 , which can effectively suppress the subsequent reaction between polysulfides in electrolyte and lithium metal and thus result in the alleviation of polysulfide shuttle effect. In contrast, when using electrolyte without LiNO 3 , the shuttled polysulfides continuously react with lithium metal to form insulating Li 2 S on lithium anode, leading to the irreversible capacity loss. Our present operando XAS study provides a valuable insight into the important role of LiNO 3 for the protection of lithium anodes, which will be beneficial for the further development of new electrolyte additives for high-performance Li-S batteries.