Chemistry at the cathode/electrolyte interface plays an important role for lithium-sulfur batteries in which stable cycling of the sulfur cathode requires confinement of the lithium polysulfide intermediates and their fast electrochemical conversion on the electrode surface. While many materials have been found to be effective for confining polysulfides, the underlying chemical interactions remain poorly understood. We report a new and general lithium polysulfide-binding mechanism enabled by surface oxidation layers of transition-metal phosphide and chalcogenide materials. We for the first time find that CoP nanoparticles strongly adsorb polysulfides because their natural oxidation (forming Co-O-P-like species) activates the surface Co sites for binding polysulfides via strong Co-S bonding. With a surface oxidation layer capable of confining polysulfides and an inner core suitable for conducting electrons, the CoP nanoparticles are thus a desirable candidate for stabilizing and improving the performance of sulfur cathodes in lithium-sulfur batteries. We demonstrate that sulfur electrodes that hold a high mass loading of 7 mg cm and a high areal capacity of 5.6 mAh cm can be stably cycled for 200 cycles. We further reveal that this new surface oxidation-induced polysulfide-binding scheme applies to a series of transition-metal phosphide and chalcogenide materials and can explain their stabilizing effects for lithium-sulfur batteries.

Discovering new chemistry and materials to enable rechargeable batteries with higher capacity and energy density is of paramount importance. While Li metal is the ultimate choice of a battery anode, its low efficiency is still yet to be overcome. Many strategies have been developed to improve the reversibility and cycle life of Li metal electrodes. However, almost all of the results are limited to shallow cycling conditions (e.g., 1 mAh cm) and thus inefficient utilization (<1%). Here we achieve Li metal electrodes that can be deeply cycled at high capacities of 10 and 20 mAh cm with average Coulombic efficiency >98% in a commercial LiPF/carbonate electrolyte. The high performance is enabled by slow release of LiNO into the electrolyte and its subsequent decomposition to form a LiN and lithium oxynitrides (LiN O)-containing protective layer which renders reversible, dendrite-free, and highly dense Li metal deposition. Using the developed Li metal electrodes, we construct a Li-MoS full cell with the anode and cathode materials in a close-to-stoichiometric amount ratio. In terms of both capacity and energy, normalized to either the electrode area or the total mass of the electrode materials, our cell significantly outperforms other laboratory-scale battery cells as well as the state-of-the-art Li ion batteries on the market.

The conversion reaction mechanism has widely been accepted in interpreting and evaluating the lithium storage capability of transition metal oxides (MOs). However, this mechanism cannot well explain the phenomenon of the extra capacity which exists in almost all MO materials and attracts much attention.Up to now, the extra capacity phenomenon has generally been ascribed to the reversible conversion of polymeric gel-like films. However, the essential role of metal nanoparticles in this process has not been systematically investigated. To further illustrate the role of metal nanoparticles for the extra capacity, Fe 3 O 4 @C and Fe@C monodispersed hierarchical core-shell microspheres were designed and adopted as the case study. Naturally Fe 3 O 4 @C composites exhibited a large Li storage capacity beyond its theoretical value. However, Fe@C microspheres, which are usually regarded to be inert for lithium storage, still presented a certain electrochemical capacity. Fe nanoparticles might serve as electrocatalysts for the reversible conversion of some components of solid electrolyte interface films, and bring extra capacity to Fe 3 O 4 and electrochemical capacity to Fe. This study can enlighten us for the exploiting of advanced active materials and electrolytes for Li ion batteries, and new energy storage devices.Fe@C composites, XRD and EDS of Fe@C composites, CV curves and cycling performances of FeCO 3 and FeOOH, extra capacity of MOs, CV analysis of Fe-based inorganic compounds and metal-nanoparticle-related materials, TEM images and cycling performance of M/C nanosheets, and HRTEM images of Fe@C composites aer the initial charge. See

There are rising concerns over the impact of COVID-19 on the agricultural production, which may become a nonnegligible threat to the long-term food supply and food security. This paper discusses the impact of COVID-19 on agricultural production in China, followed by government responses to alleviate the negative effects. The results show that unreasonable restrictions would block the outflow channels of agricultural products, hinder necessary production inputs, destroy production cycles, and finally undermine production capacity. It is expected that China's experiences could give warnings and suggestions to other countries that are experiencing serious outbreak to protect domestic agricultural production, especially developing countries.