Volume 5 Issue 4, April 2020

All-solid-state lithium batteries typically suffer from low coulombic efficiencies and lithium dendrite growth at high current densities. Now, a silver–carbon composite anode is demonstrated that mitigates some of these problems, even for a prototype cell with a high energy density of over 900 Wh L^–1.

Hot carrier solar cells require mechanisms to dramatically reduce the rate at which carriers thermalize in semiconductors. Now, side-valley trapping of hot carriers with long decay lifetimes is shown to increase the chance of extraction of carriers while they are still hot.

Mandatory building energy audits in New York City lead to a modest reduction of energy use of 2.5% and 4.9% for multifamily and office buildings, respectively. This suggests that other approaches besides mandatory audit policies, such as building energy grading and carbon intensity targets, may be needed to achieve sustainability goals.

Evaluating the impact of renewable energy innovation research funding is important to design more productive research and development programmes. Pless et al. discuss the key challenges in effective evaluation of research funding outcomes and identify solutions.

Non-flammable high-performance electrolytes are in high demand for rechargeable batteries. Here the authors design cyclic phosphate-based electrolytes to enable stable operations of graphite anodes and high-voltage cathodes for lithium-ion batteries.

Solid-state Li metal batteries represent one of the most promising rechargeable battery technologies. Here the authors report an exceptional high-performance prototype solid-state pouch cell made of a sulfide electrolyte, a high-Ni layered oxide cathode and, in particular, a silver–carbon composite anode with no excess Li.

Although more cities are considering mandatory building energy audits, their effect on energy use in buildings is not clear. Using data from New York, Kontokosta et al. estimate the extent to which Local Law 87 mandating building energy audits has contributed to a decrease in energy use.

Carbon dioxide can be reduced electrocatalytically to fuels using copper catalysts, but the key features that determine the selectivity of these materials to specific products remains uncertain. Here Arán–Ais et al. use in situ methods to explore the influence of morphology and oxidation state on the performance of copper catalysts.

Stacking multiple junctions with different bandgaps and operating under concentrated light allows solar cells to reach efficiencies beyond the limits of standard devices. Geisz et al. present a six-junction solar cell based on III–V materials with a 47.1% efficiency—the highest reported to date.

Hot carrier solar cells offer greater conversion efficiency than single junction cells but they have yet to be demonstrated in real devices. Esmaielpour et al. show that hot carriers are harnessed from metastable valleys in III–V heterojunction devices at voltages greater than the absorber bandgap.