Lithium–sulfur (Li–S) batteries are considered as promising next‐generation energy storage devices due to their ultrahigh theoretical energy density, where soluble lithium polysulfides are crucial in ...the Li–S electrochemistry as intrinsic redox mediators. However, the poor mediation capability of the intrinsic polysulfide mediators leads to sluggish redox kinetics, further rendering limited rate performances, low discharge capacity, and rapid capacity decay. Here, an organodiselenide, diphenyl diselenide (DPDSe), is proposed to accelerate the sulfur redox kinetics as a redox comediator. DPDSe spontaneously reacts with lithium polysulfides to generate lithium phenylseleno polysulfides (LiPhSePSs) with improved redox mediation capability. The as‐generated LiPhSePSs afford faster sulfur redox kinetics and increase the deposition dimension of lithium sulfide. Consequently, the DPDSe comediator endows Li–S batteries with superb rate performance of 817 mAh g−1 at 2 C and remarkable cycling stability with limited anode excess. Moreover, Li–S pouch cells with the DPDSe comediator achieve an actual initial energy density of 301 Wh kg−1 and 30 stable cycles. This work demonstrates a novel redox comediation strategy with an effective organodiselenide comediator to facilitate the sulfur redox kinetics under pouch cell conditions and inspires further exploration in mediating Li–S kinetics for practical high‐energy‐density batteries.
An organodiselenide, diphenyl diselenide (DPDSe), is proposed to accelerate the sulfur redox kinetics as a redox comediator, which endows Li–S batteries with superb rate performance, remarkable cycling stability, and high actual energy density of 301 Wh kg−1. This work demonstrates a novel redox comediation strategy to facilitate the sulfur redox kinetics under practical pouch cell conditions.
This study examines how firms’ voluntary disclosure decisions are influenced by product market competition. Using separate measures to capture different dimensions of competition, I show that ...competition from potential entrants increases disclosure quantity while competition from existing rivals decreases disclosure quantity. I also find that competition enhances disclosure quality mainly through reducing the optimism in profit forecasts and reducing the pessimism in investment forecasts. Moreover, I find that the above association is less pronounced for industry leaders, consistent with industry leaders facing less competitive pressures than industry followers.
This paper examines the role of conditional accounting conservatism in mitigating the cost of equity and debt capital in an international setting. The findings are that firms domiciled in countries ...with more conservative financial reporting systems have lower cost of equity and debt capital. The paper further explores the cross‐sectional variation of the above relationships, finding that the negative association between conditional conservatism and the cost of equity and debt capital is more pronounced in countries with stronger legal enforcement, suggesting a complementary role between conservatism and legal institutions in capital markets. In addition, the paper finds that conservatism only reduces the cost of debt in countries where accounting‐based covenants are widely used, consistent with the argument that conditional conservatism improves the efficiency of debt contracts via accelerating covenant violations.
Stochastic gradient descent (SGD) still is the workhorse for many practical problems. However, it converges slow, and can be difficult to tune. It is possible to precondition SGD to accelerate its ...convergence remarkably. But many attempts in this direction either aim at solving specialized problems, or result in significantly more complicated methods than SGD. This paper proposes a new method to adaptively estimate a preconditioner, such that the amplitudes of perturbations of preconditioned stochastic gradient match that of the perturbations of parameters to be optimized in a way comparable to Newton method for deterministic optimization. Unlike the preconditioners based on secant equation fitting as done in deterministic quasi-Newton methods, which assume positive definite Hessian and approximate its inverse, the new preconditioner works equally well for both convex and nonconvex optimizations with exact or noisy gradients. When stochastic gradient is used, it can naturally damp the gradient noise to stabilize SGD. Efficient preconditioner estimation methods are developed, and with reasonable simplifications, they are applicable to large-scale problems. Experimental results demonstrate that equipped with the new preconditioner, without any tuning effort, preconditioned SGD can efficiently solve many challenging problems like the training of a deep neural network or a recurrent neural network requiring extremely long-term memories.
Lithium–sulfur (Li–S) batteries are deemed as future energy storage devices due to ultrahigh theoretical energy density. Cathodic polysulfide electrocatalysts have been widely investigated to promote ...sluggish sulfur redox kinetics. Probing the surface structure of electrocatalysts is vital to understanding the mechanism of polysulfide electrocatalysis. In this work, we for the first time identify surface gelation on disulfide electrocatalysts. Concretely, the Lewis acid sites on disulfides trigger the ring‐opening polymerization of the dioxolane solvent to generate a surface gel layer, covering disulfides and reducing the electrocatalytic activity. Accordingly, a Lewis base triethylamine (TEA) is introduced as a competitive inhibitor. Consequently, Li–S batteries with disulfide electrocatalysts and TEA afford high specific capacity and improved rate responses. This work affords new insights on the actual surface structure of electrocatalysts in Li–S batteries.
Surface gelation on disulfide electrocatalysts in Li–S batteries is identified for the first time. The gel layer, formed through the solvent polymerization triggered by the Lewis acid sites, covers the active electrocatalytic sites and renders reduced redox kinetics. Herein, a Lewis base triethylamine is introduced to suppress the surface gelation and promote the electrocatalytic activity of disulfide electrocatalysts.
By employing enantiomerically pure mono-bidentate N-donors (L
R
/L
S
) as chiral bridging ligands to react with Cu(ClO
4
)
2
(H
2
O)
6
in CH
3
CN-DMF mixed solvent, respectively, a pair of ionic ...one-dimensional (1D) Cu(
ii
) chain enantiomers formulated as {CuL
R
(CH
3
CN)(DMF)H
2
O(ClO
4
)
2
}
n
/{CuL
S
(CH
3
CN)(DMF)H
2
O(ClO
4
)
2
}
n
(
D-1
/
L-1
) were isolated and structurally characterized, where L
R
/L
S
= (−)/(+)-4,5-pinenepyridyl-2-pyrazine. They crystallize in the noncentrosymmetric (NCS)
P
2
1
2
1
2
1
space group of an orthorhombic system due to the introduction of chiral L
R
/L
S
, and the ClO
4
−
groups as counteranions reside in crystal lattices, thus leading to charge separation with large dipole moments in their molecular structures. Based on crystal samples, investigation on their nonlinear optical (NLO) behaviors showed that
D-1
and
L-1
display simultaneously much larger second- and third-harmonic generation (SHG and THG) responses than their analogues based on the same chiral N-donors (L
R
/L
S
) and Cu(NO
3
)
2
(H
2
O)
3
with NO
3
−
acting as the coordination group to bind Cu(
ii
) ions. The SHG intensities of
D-1
/
L-1
are 0.62/0.60 × KDP (KH
2
PO
4
), and THG intensities of
D-1
/
L-1
are 238/228 × α-SiO
2
. Our finding indicates that coordination polymers (CPs) with charge separation and NCS structures,
i.e.
, ionic CPs with NCS arrangements are the ideal NLO crystalline materials for the simultaneous observation of large SHG and THG responses, thus providing a new approach to obtain NLO-active CP crystalline materials with high-performance SHG and THG responses.
We demonstrate that ionic CPs with noncentrosymmetric structures are good candidates for the simultaneous observation of high-performance SHG and THG responses.
Lithium–sulfur (Li–S) batteries promise great potential as high‐energy‐density energy storage devices. However, the parasitic reactions between lithium polysulfides (LiPSs) and Li metal anodes render ...limited cycling lifespan of Li–S batteries. Herein, an organic‐rich solid electrolyte interphase (SEI) is constructed to inhibit the LiPS parasitic reactions and achieve long‐cycling Li–S batteries. Concretely, 1,3,5‐trioxane is introduced as a reactive co‐solvent that decomposes on Li anode surfaces and contributes organic components to the SEI. The as‐constructed organic‐rich SEI effectively inhibits the LiPS parasitic reactions and protects working Li metal anodes. Consequently, the cycling lifespan of Li–S coin cells with 50 µm Li anodes and 4.0 mg cm−2 sulfur cathodes is prolonged from 130 to 300 cycles by the organic‐rich SEI. Furthermore, the organic‐rich SEI enables a 3.0 Ah‐level Li–S pouch cell to achieve a high energy density of 400 Wh kg−1 and stable 26 cycles. This study affords an effective organic‐rich SEI to inhibit the LiPS parasitic reactions and inspires rational SEI design to achieve long‐cycling Li–S batteries.
A robust organic‐rich solid electrolyte interphase (SEI) is constructed to inhibit the lithium polysulfide parasitic reactions and achieve long‐cycling lithium–sulfur batteries. The organic‐rich SEI constructed by the decomposition of 1,3,5‐trioxane effectively protects lithium metal anodes during cycling while the routine SEI induces inhomogeneous lithium deposition and rapid lithium anode failure.
Metal–organic frameworks (MOFs), as an important kind of porous inorganic‐organic hybrid materials with inherent outstanding physicochemistry characteristics, can be widely applied as versatile ...precursors for the facile preparation of functional MOF‐derived materials. However, there are plenty of sophisticated factors during the synthetic process, which is far from reaching the goal of effectively controlling the nature of MOF‐derived materials (such as the composition, morphology and surface area). Therefore, it is urgently necessary to develop regular protocols and concepts for controllable syntheses of MOF‐derived materials. In this minireview, we mainly summarize and analyze complicated factors in the fabrication of MOF‐derived materials according to recently reported literatures, and this provides a new insight into the rational design and syntheses of MOF‐derived materials.
Metal–organic frameworks (MOFs) serve as appropriate sacrificial precursors for fabricating MOF‐derived materials with high‐performance applications. However, it is very difficult to control the characteristics of MOF‐derived materials. Here, the complicated factors about the controllable syntheses are carefully summarized and discussed in this minireview, which will be beneficial to guide the synthetic concepts of MOF‐derived materials.
Mutations in the proline-rich transmembrane protein 2 （PRRT2） are associated with paroxysmal kinesigenic dys- kinesia （PKD） and several other paroxysmal neurological diseases, but the PRRT2 function ...and pathogenic mecha- nisms remain largely obscure. Here we show that PRRT2 is a presynaptic protein that interacts with components of the SNARE complex and downregulates its formation. Loss-of-function mutant mice showed PKD-like phenotypes triggered by generalized seizures, hyperthermia, or optogenetic stimulation of the cerebellum. Mutant mice with spe- cific PRRT2 deletion in cerebellar granule cells （GCs） recapitulate the behavioral phenotypes seen in Prrt2-null mice. Furthermore, recording made in cerebellar slices showed that optogenetic stimulation of GCs results in transient elevation followed by suppression of Purkinje cell firing. The anticonvulsant drug carbamazepine used in PKD treat- ment also relieved PKD-like behaviors in mutant mice. Together, our findings identify PRRT2 as a novel regulator of the SNARE complex and provide a circuit mechanism underlying the PRRT2-related behaviors.
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