High-performance LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2) cathode by nanoscale lithium sulfide coating via atomic layer deposition

The commercialization of nickel-rich LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811) has been hindered by its continuous loss of practical capacity and reduction in average working voltage.To address these issues,surface modification has been well-recognized as an effective strategy.Different from the coatings reported in literature to date,in this work,we for the first time report a sulfide coating,amorphous Li_(2)S via atomic layer deposition (ALD).Our study revealed that the conformal nano-Li_(2)S coating shows exceptional protection over the NMC811 cathodes,accounting for the dramatically boosted capacity retention from~11.6%to~71%and the evidently mitigated voltage reduction from 0.39 to 0.18 V after 500 charge–discharge cycles.In addition,the Li_(2)S coating remarkably improved the rate capability of the NMC811 cathode.Our investigation further revealed that all these beneficial effects of the ALD-deposited nano-Li_(2)S coating lie in the following aspects:(i) maintain the mechanical integrity of the NMC811 electrode:(ii) stabilize the NMC electrode/electrolyte interface:and (iii) suppress the irreversible phase transition of NMC structure.Particularly,this study also has revealed that the nano-Li_(2)S coating has played some unique role not associated with traditional non-sulfide coatings such as oxides.In this regard,we disclosed that the Li_(2)S layer has reacted with the released O_(2) from the NMC lattices,and thereby has dramatically mitigated electrolyte oxidation and electrode corrosion.Thus,this study is significant and has demonstrated that sulfides may be an important class of coating materials to tackle the issues of NMCs and other layered cathodes in lithium batteries.

Metallic and highly conducting two-dimensional atomic arrays of sulfur enabled by molybdenum disulfide nanotemplate

Element sulfur in nature is an insulating solid.While it has been tested that one-dimensional sulfur chain is metallic and conducting,the investigation on two-dimensional sulfur remains elusive.We report that molybdenum disulfide layers are able to serve as the nanotemplate to facilitate the formation of two-dimensional sulfur.Density functional theory calculations suggest that confined inbetween layers of molybdenum disulfide,sulfur atoms are able to form two-dimensional triangular arrays that are highly metallic.As a result,these arrays contribute to the high conductivity and metallic phase of the hybrid structures of molybdenum disulfide layers and two-dimensional sulfur arrays.The experimentally measured conductivity of such hybrid structures reaches up to 223 S/m.Multiple experimental results,including X-ray photoelectron spectroscopy(XPS),transition electron microscope(TEM),selected area electron diffraction(SAED),agree with the computational insights.Due to the excellent conductivity,the current density is linearly proportional to the scan rate until 30,000 mV s^(−1) without the attendance of conductive additives.Using such hybrid structures as electrode,the two-electrode supercapacitor cells yield a power density of 10^(6) Wh kg^(−1) and energy density ~47.5 Wh kg^(−1) in ionic liquid electrolytes.Our findings offer new insights into using two-dimensional materials and their Van der Waals heterostructures as nanotemplates to pattern foreign atoms for unprecedented material properties.

Molecular Layer Deposition of Crosslinked Polymeric Lithicone for Superior Lithium Metal Anodes

In this work,we for the first time developed a novel lithium-containing crosslinked polymeric material,a lithicone that enables excellent protection effects over lithium(Li)metal anodes.This new lithicone was synthesized via an accurately controllable molecular layer deposition(MLD)process,in which lithium tert-butoxide(LTB)and glycerol(GL)were used as precursors.The resultant LiGL lithicone was analyzed using a suite of characterizations.Furthermore,we found that the LiGL thichicone could serve as an exceptional polymeric protection film over Li metal anodes.Our experimental data revealed that the Li electrodes coated by this LiGL lithicone can achieve a superior cycling stability,accounting for an extremely long cyclability of>13,600 Listripping/plating cycles and having no failures so far in Li/Li symmetric cells at a current density of 5 mA/cm^(2)and an areal capacity of 1 mAh/cm^(2).We found that,with a sufficient protection by this LiGL coating,Li electrodes could realize long-term stable cyclability with little formation of Li dendrites and solid electrolyte interphase.This novel LiGL represents a facile and effective solution to the existing issues of Li anodes and potentially paves a technically feasible route for lithium metal batteries.