Maximum atom efficiency as well as distinct chemoselectivity is expected for electrocatalysis on atomically dispersed (or single site) metal centres, but its realization remains challenging so far, because carbon, as the most widely used electrocatalyst support, cannot effectively stabilize them. Here we report that a sulfur-doped zeolite-templated carbon, simultaneously exhibiting large sulfur content (17 wt% S), as well as a unique carbon structure (that is, highly curved three-dimensional networks of graphene nanoribbons), can stabilize a relatively high loading of platinum (5 wt%) in the form of highly dispersed species including site isolated atoms. In the oxygen reduction reaction, this catalyst does not follow a conventional four-electron pathway producing H₂O, but selectively produces H₂O₂ even over extended times without significant degradation of the activity. Thus, this approach constitutes a potentially promising route for producing important fine chemical H₂O₂, and also offers opportunities for tuning the selectivity of other electrochemical reactions on various metal catalysts.

In this paper, the structural change of the sulfur cathode during the electrochemical reaction of a lithium sulfur battery employing 0.5 M <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">LiCF</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo>SO</mml:mo><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:math>LiCF3SO3 -tetra(ethylene glycol) dimethyl ether (TEGDME) was studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and wave dispersive spectroscopy (WDS). The discharge process of the lithium sulfur cell could be divided in the first discharge region (2.4-2.1 V) where the reduction of elemental sulfur to form soluble polysulfides and further reduction of the soluble polysulfide occur, and the second discharge region (2.1-1.5 V) where the soluble polysulfides are reduced to form a nonuniform <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S solid film covered over the carbon matrix. It was also found that the charge of lithium sulfur cell leads to the conversion from <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S to the soluble polysulfide, resulting in the removal of <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S layer formed on carbon matrix. However, the oxidization of the soluble polysulfide to solid sulfur hardly occurs and few <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S are left on carbon matrix even at 100% depth of charge. © 2003 The Electrochemical Society. All rights reserved.

This paper reports on the investigation of rate capability and cycle characteristics of a lithium sulfur battery. The second discharge region where solid <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S is formed on the surface of the carbon matrix in the cathode was highly sensitive to cathode thickness and discharge rate. The scanning electron microscope (SEM) observation suggests that thick <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S layer formed at the surface of the cathode causes the diminution of the second discharge region at high discharge rate. Upon repeated cycle, the delocalization of the surface <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S layer happened, however, the irreversible <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S gradually increased with cycle as evidence by (SEM) and wave dispersive spectroscopy measurements, causing capacity fade. The formation of the irreversible <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S was more significant for higher rates of discharge. It is believed that the destruction of the carbon matrix by stress generated during the localized deposition of <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo></mml:math>Li2S is responsible for the formation of irreversible <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">Li</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>S</mml:mo><mml:mo>.</mml:mo></mml:math>Li2S. © 2003 The Electrochemical Society. All rights reserved.

Uncontrolled growth of insulating lithium sulfide leads to passivation of sulfur cathodes, which limits high sulfur utilization in lithium-sulfur batteries. Sulfur utilization can be augmented in electrolytes based on solvents with high Gutmann Donor Number; however, violent lithium metal corrosion is a drawback. Here we report that particulate lithium sulfide growth can be achieved using a salt anion with a high donor number, such as bromide or triflate. The use of bromide leads to ~95 % sulfur utilization by suppressing electrode passivation. More importantly, the electrolytes with high-donor-number salt anions are notably compatible with lithium metal electrodes. The approach enables a high sulfur-loaded cell with areal capacity higher than 4 mA h cm⁻² and high sulfur utilization ( > 90 %). This work offers a simple but practical strategy to modulate lithium sulfide growth, while conserving stability for high-performance lithium-sulfur batteries.

The long-term cycling of anode-free Li-metal cells (i.e., cells where the negative electrode is in situ formed by electrodeposition on an electronically conductive matrix of lithium sourced from the positive electrode) using a liquid electrolyte is affected by the formation of an inhomogeneous solid electrolyte interphase (SEI) on the current collector and irregular Li deposition. To circumvent these issues, we report an atomically defective carbon current collector where multivacancy defects induce homogeneous SEI formation on the current collector and uniform Li nucleation and growth to obtain a dense Li morphology. Via simulations and experimental measurements and analyses, we demonstrate the beneficial effect of electron deficiency on the Li hosting behavior of the carbon current collector. Furthermore, we report the results of testing anode-free coin cells comprising a multivacancy defective carbon current collector, a Li_xNi_0.8Co_0.1Mn_0.1-based cathode and a nonaqueous Li-containing electrolyte solution. These cells retain 90% of their initial capacity for over 50 cycles under lean electrolyte conditions.