Graphitic Carbon Nitride (g‐C 3 N 4 ): An Interface Enabler for Solid‐State Lithium Metal Batteries

A robust Fe-based heterogeneous photocatalyst for the visible-light-mediated selective reduction of an impure CO2 stream

The transformation of CO2 into value-added products from an impure CO2 stream, such as flue gas or exhaust gas, directly contributes to the principle of carbon capture and utilization (CCU). Thus, we have developed a robust iron-based heterogeneous photocatalyst that can convert the exhaust gas from the car into CO with an exceptional production rate of 145 μmol g-1 h-1. We characterized this photocatalyst by PXRD, XPS, ssNMR, EXAFS, XANES, HR-TEM, and further provided mechanistic experiments, and multi-scale/level computational studies. We have reached a clear understanding of its properties and performance that indicates that this highly robust photocatalyst could be used to design an efficient visible-light-mediated reduction strategy for the transformation of impure CO2 streams into value-added products.

Competitive Li+ Coordination in Ionogel Electrolytes for Enhanced Li-Ion Transport Kinetics

Developing ionogel electrolytes based on ionic liquid instead of volatile liquid in gel polymer electrolytes is regarded to be effective to diminish safety concerns in terms of overheating and fire. Herein, a zwitterion-based copolymer matrix based on the copolymerization of trimethylolpropane ethoxylate triacrylate (ETPTA) and 2-methacryloyloxyethylphosphorylcholine (MPC, one typical zwitterion) is developed. It is shown that introducing zwitterions into ionogel electrolytes can effectively optimize local lithium-ion (Li+ ) coordination environment to improve Li+ transport kinetics. The interactions between Li+ and bis(trifluoromethanesulfonyl)imide (TFSI- )/MPC lead to the formation of Li+ coordination shell jointly occupied by MPC and TFSI- . Benefiting from the competitive Li+ attraction of TFSI- and MPC, the energy barrier of Li+ desolvation is sharply decreased and thus the room-temperature ionic conductivity can reach a value of 4.4 × 10-4 S cm-1 . Besides, the coulombic interaction between TFSI- and MPC can greatly decrease the reduction stability of TFSI- , boosting in situ derivation of LiF-enriched solid electrolyte interface  layer on lithium metal surface. As expected, the assembled Li||LiFePO4 cells deliver a high reversible discharge capacity of 139 mAh g-1 at 0.5 C and good cycling stability. Besides, the pouch cells exhibit a steady open-circuit voltage and can operate normally under abuse testing (fold, cut), showing its outstanding safety performance.

An Atomically Dispersed Mn-Photocatalyst for Generating Hydrogen Peroxide from Seawater via the Water Oxidation Reaction (WOR)

In this work, we have fabricated an aryl amino-substituted graphitic carbon nitride (g-C₃N₄) catalyst with atomically dispersed Mn capable of generating hydrogen peroxide (H₂O₂) directly from seawater. This new catalyst exhibited excellent reactivity, obtaining up to 2230 μM H₂O₂ in 7 h from alkaline water and up to 1800 μM from seawater under identical conditions. More importantly, the catalyst was quickly recovered for subsequent reuse without appreciable loss in performance. Interestingly, unlike the usual two-electron oxygen reduction reaction pathway, the generation of H₂O₂ was through a less common two-electron water oxidation reaction (WOR) process in which both the direct and indirect WOR processes occurred; namely, photoinduced h⁺ directly oxidized H₂O to H₂O₂ via a one-step 2e^- WOR, and photoinduced h⁺ first oxidized a hydroxide (OH^-) ion to generate a hydroxy radical (^•OH), and H₂O₂ was formed indirectly by the combination of two ^•OH. We have characterized the material, at the catalytic sites, at the atomic level using electron paramagnetic resonance, X-ray absorption near edge structure, extended X-ray absorption fine structure, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, magic-angle spinning solid-state NMR spectroscopy, and multiscale molecular modeling, combining classical reactive molecular dynamics simulations and quantum chemistry calculations.

Stabilizing the interface of PEO solid electrolyte to lithium metal anode via a g-C3N4 mediator

g-C₃N₄ is introduced to the PEO electrolyte as a mediator to stabilize the interface to lithium metal anode. As a result, the interface resistance is stabilized after cycling and the symmetric cell exhibits a cycle life over 900 h, indicating that the interface stability is evidently promoted.

Interfacial Defect of Lithium Metal in Solid-State Batteries

All-solid-state battery with Li metal anode is a promising rechargeable battery technology with high energy density and improved safety. Currently, the application of Li metal anode is plagued by the failure at the interfaces between lithium metal and solid electrolyte (SE). However, little is known about the defects at Li-SE interfaces and their effects on Li cycling, impeding further improvement of Li metal anodes. Herein, by performing large-scale atomistic modeling of Li metal interfaces with common SEs, we discover that lithium metal forms an interfacial defect layer of nanometer-thin disordered lithium at the Li-SE interfaces. This interfacial defect Li layer is highly detrimental, leading to interfacial failure such as pore formation and contact loss during Li stripping. By systematically studying and comparing incoherent, coherent, and semi-coherent Li-SE interfaces, we find that the interface with good lattice coherence has reduced Li defects at the interface and has suppressed interfacial failure during Li cycling. Our finding discovered the critical roles of atomistic lithium defects at interfaces for the interfacial failure of Li metal anode, and motivates future atomistic-level interfacial engineering for Li metal anode in solid-state batteries.

Wearable Tin-Based Perovskite Solar Cells Achieved by a Crystallographic Size Effect

Tin-based perovskite solar cells (PSCs) demonstrate a potential application in wearable electronics due to its hypotoxicity. However, poor crystal quality is still the bottleneck for achieving high-performance flexible devices. In this work, graphite phase-C₃ N₄ (g-C₃ N₄ ) is applied into tin-based perovskite as a crystalline template, which delays crystallization via a size-effect and passivates defects simultaneously. The double hydrogen bond between g-C₃ N₄ and formamidine cation can optimize lattice matching and passivation. Moreover, the two-dimensional network structure of g-C₃ N₄ can fit on the crystals, resulting an enhanced hydrophobicity and oxidation resistance. Therefore, the flexible tin-based PSCs with g-C₃ N₄ realize a stabilized power conversion efficiency (PCE) of 8.56 % with negligible hysteresis. In addition, the PSCs can maintain 91 % of the initial PCE after 1000 h under N₂ environment and keep 92 % of their original PCE after 600 cycles at a curvature radius of 3 mm.

Sustainable and Robust Graphene Cellulose Paper Decorated with Lithiophilic Au Nanoparticles to Enable Dendrite-free and High-Power Lithium Metal Anode

Lithium metal anodes (LMAs) with high energy density have recently captured increasing attention for development of next-generation batteries. However, practical viability of LMAs is hindered by the uncontrolled Li dendrite growth and infinite dimension change. Even though constructing 3D conductive skeleton has been regarded as a reliable strategy to prepare stable and low volume stress LMAs, engineering the renewable and lithiophilic conductive scaffold is still a challenge. Herein, a robust conductive scaffold derived from renewable cellulose paper, which is coated with reduced graphene oxide and decorated with lithiophilic Au nanoparticles, is engineered for LMAs. The graphene cellulose fibres with high surface area can reduce the local current density, while the well-dispersed Au nanoparticles can serve as lithiophilic nanoseeds to lower the nucleation overpotential of Li plating. The coupled relationship can guarantee uniform Li nucleation and unique spherical Li growth into 3D carbon matrix. Moreover, the natural cellulose paper possesses outstanding mechanical strength to tolerate the volume stress. In virtue of the modulated deposition behaviour and near-zero volume change, the hybrid LMAs can achieve reversible Li plating/stripping even at an ultrahigh current density of 10 mA cm^-2 as evidenced by high Coulombic efficiency (97.2 % after 60 cycles) and ultralong lifespan (1000 cycles) together with ultralow overpotential (25 mV). Therefore, this strategy sheds light on a scalable approach to multiscale design versatile Li host, promising highly stable Li metal batteries to be feasible and practical.