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Lithium metal batteries (LMBs) represent the most promising next-generation high-energy density batteries. The solid electrolyte interphase (SEI) film on the lithium metal anode plays a crucial role in regulating lithium deposition and improving the cycling performance of LMBs. In this review, we comprehensively present the formation process of the SEI film, while elucidating the key properties such as electronic conductivity, ionic conductivity, and mechanical performance. Furthermore, various approaches for constructing the SEI film are discussed from both electrolyte regulation and artificial coating design perspectives. Lastly, future research directions along with development recommendations are also provided. This review aims to provide possible strategies for the further improvement of SEI film in LMBs and highlight their inspiration for future research directions., (© 2024 Wiley-VCH GmbH.)

As promising alternatives to liquid electrolytes, polymer electrolytes attract much research interest recently, but their widespread use is limited by the low ionic conductivity. In this study, we use electrostatic spinning to introduce particles of an ionic conductor into polyacrylonitrile (PAN) fibers to prepare a porous membrane as the host of gel polymer electrolytes (GPEs). The relevant in-situ produced GPE performs a high ionic conductivity of 6.0×10 -3  S cm -1 , and a high lithium transfer number (t Li + ) of 0.85 at 30 °C, respectively. A symmetrical Li cell with this GPE can cycle stably for 550 h at a current density of 0.5 mA cm -2 . While the capacity retention of the NCM|GPE|Li cell is 79.84 % after 500 cycles at 2 C. Even with an increased cut-off voltage of 4.5 V, the 1 st coulomb efficiency reaches 91.58 % with a specific discharge capacity of 213.4 mAh g -1 . This study provides a viable route for the practical application of high energy density lithium metal batteries., (© 2024 Wiley-VCH GmbH.)

A lithium-sulfur (Li-S) battery is a promising candidate for an electrochemical energy-storage system. However, for a long time, it suffered from the "shuttle effect" of the intermediate products of soluble polysulfides and safety issues concerning the combustible liquid electrolyte and lithium anode. In this work, sulfide polyacrylonitrile (SPAN) is employed as a solid cycled cathode to resolve the "shuttle effect" fundamentally, a gel polymer electrolyte (GPE) based on poly(ethylene glycol) diacrylate (PEGDA) is matched to the SPAN cathode to minimize the safety concerns, and finally, a quasi-solid-state Li-SPAN battery is combined by an in situ thermal polymerization strategy to improve its adaptability to the existing battery assembly processes. The PEGDA-based GPE achieved at 60 °C for 40 min ensures little damage to the in situ battery, a good electrode-electrolyte interface, a high ionic conductivity of 6.87 × 10 -3 S cm -1 at 30 °C, and a wide electrochemical window of 4.53 V. Ultimately, the as-prepared SPAN composite exerts a specific capacity of 1217.3 mAh g -1 after 250 cycles at 0.2 C with a high capacity retention rate of 89.9%. The combination of the SPAN cathode and in situ thermally polymerized PEGDA-based GPE provides a new inspiration for the design of Li-SPAN batteries with both high specific energy and high safety.

The rational design of high-performance non-noble metal electrocatalysts at large current densities is important for the development of sustainable energy conversion devices such as alkaline water electrolyzers. However, improving the intrinsic activity of those non-noble metal electrocatalysts remains a great challenge. Therefore, Ni 2 P/MoO x decorated three-dimensional (3D) NiFeP nanosheets (NiFeP@Ni 2 P/MoO x ) with abundant interfaces were synthesized using facile hydrothermal and phosphorization methods. NiFeP@Ni 2 P/MoO x exhibits excellent electrocatalytic activity for hydrogen evolution reaction (HER) at a high current density of -1000 mA cm -2 with a low overpotential of 390 mV. Surprisingly, it can operate steadily at a large current density of -500 mA cm -2 for 300 h, indicating its long-term durability under high current densities. The boosted electrocatalytic activity and stability can be ascribed to the as-fabricated heterostructures via interface engineering, leading to modifying the electronic structure, improving the active area, and enhancing the stability. Besides, the 3D nanostructure is also beneficial for exposing abundant accessible active sites. Therefore, this research proposes a considerable route for fabricating non-noble metal electrocatalysts by interface engineering and 3D nanostructure applied in large-scale hydrogen production facilities., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

A flexible free-standing cathode is innovatively constructed with NaCrO 2 as the electrochemical active substance via an electrospinning technique. The as constructed NaCrO 2 @C flexible free-standing cathode exhibits exceptional rate performance (106 mA h g -1 at 10C) and cyclability (retention rate of 87.5% after 300 cycles at 0.2C). This work provides a brand-new perspective to the development of flexible free-standing cathodes.

A stable solid electrolyte interphase (SEI) layer is crucial for lithium metal anode (LMA) to survive in long-term cycling. However, chaotic structures and chemical inhomogeneity of natural SEI make LMA suffering from exasperating dendrite growth and severe electrode pulverization, which hinder the practical application of LMAs. Here, we design a catalyst-derived artificial SEI layer with an ordered polyamide-lithium hydroxide (PA-LiOH) bi-phase structure to modulate ion transport and enable dendrite-free Li deposition. The PA-LiOH layer can substantially suppress the volume changes of LMA during Li plating/stripping cycles, as well as alleviate the parasitic reactions between LMA and electrolyte. The optimized LMAs demonstrate excellent stability in Li plating/stripping cycles for over 1000 hours at an ultra-high current density of 20 mA cm -2 in Li||Li symmetric cells. A high coulombic efficiency up to 99.2 % in Li half cells in additive-free electrolytes is achieved even after 500 cycles at a current density of 1 mA cm -2 with a capacity of 1 mAh cm -2 ., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Oxidative decomposition reactions of common cyclic carbonates in the presence of BF 4 - anions were investigated using density functional theory. A polarized continuum model was utilized to model solvent effects in the oxidation of ethylene carbonate (EC) and propylene carbonate (PC) clusters. We have found that the presence of BF 4 - significantly reduces EC and PC oxidation stability, from 7.11 to 6.17 and from 7.10 to 6.06 V (vs Li + /Li), respectively. The sequence of EC and PC oxidative decomposition paths and the oxidative products were affected by the BF 4 - anion. The decomposition products of the oxidized EC-BF 4 - contained CO 2 , vinyl alcohol, and acetaldehyde, while the decomposition products of the oxidized PC-BF 4 - contained CO 2 , acetone, and propanal, in agreement with the previous experimental studies. The oxidative decomposition reactions for PC-BF 4 - are compared with those for the isolated PC, PC 2, PC-ClO 4 - , and PC-PF 6 - .

The practical implementation of lithium-sulfur batteries (LSBs) has been impeded by the sluggish redox kinetics of lithium polysulfides (LiPSs) and shuttle effect of soluble LiPSs during charge/discharge. It is desirable to exploit materials combining superior electrical conductivity with excellent catalytic activity for use as electrocatalysts in LSBs. Herein, we report the employment of chemical vapor transport (CVT) method followed by an electrochemical intercalation process to fabricate high-quality single-crystalline semimetallic β-MoTe 2 nanosheets, which are utilized to manipulate the LiPSs conversion kinetics. The first-principles calculations prove that β-MoTe 2 could lower the Gibbs free-energy barrier for Li 2 S 2 transformation to Li 2 S. The wavefunction analysis demonstrates that the p-p orbital interaction between Te p and S p orbitals accounts for the strong electronic interaction between the β-MoTe 2 surface and Li 2 S 2 /Li 2 S, making bonding and electron transfer more efficient. As a result, a β-MoTe 2 /CNT@S-based LSB cell can deliver an excellent cycling performance with a low capacity fade rate of 0.11% per cycle over 300 cycles at 1C. Our work might not only provide a universal route to prepare high-quality single-crystalline transition-metal dichalcogenides (TMDs) nanosheets for use as electrocatalysts in LSBs, but also suggest a different viewpoint for the rational design of LiPSs conversion electrocatalysts.

It is crucial for metal-air batteries and fuel cells to design non-precious-metal catalysts instead of platinum-based materials to boost the sluggish oxygen reduction reaction (ORR). Herein, Co 3 ZnC/Co nanoparticles with heterojunctions supported on N-doped porous carbon and carbon nanotubes (CNTs) are fabricated by pyrolyzing the hydrogel prepared from melamine and citric acid chelated with Co 2+ /Zn 2+ ions. This hybrid shows strong ORR catalytic activity as its half-wave potential reaches 0.88 V (vs reversible hydrogen electrode (RHE)) in 0.1 M KOH and Zn-air batteries with the catalyst have higher discharge plateaus and capacity than those employing Pt/C. The hybrid mixed with RuO 2 can also be used as an efficient bifunctional catalyst for rechargeable Zn-air batteries. The excellent performance is primarily derived from the Co 3 ZnC/Co heterojunctions, the electron transfer of which boosts the ORR catalysis. Moreover, the suitable ratio of Co/Zn in precursors results in the epitaxial growth of hollow CNTs and abundant mesopores, hence promoting the adsorption of oxygen and the transport of ORR-related species.

Because of their high ionic conductivity, utilizing gel polymer electrolytes (GPEs) is thought to be an effective way to accomplish high-energy-density batteries. Nevertheless, most GPEs have poor adaptability to Ni-rich cathodes to alleviate the problem of inevitable rapid capacity decay during cycling. Therefore, to match LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), we applied pentaerythritol tetraacrylate (PETEA) monomers to polymerize in situ in a polyacrylonitrile (PAN) membrane to obtain GPEs (PETEA-TCGG-PAN). The impedance variations and key groups during the in situ polymerization of PETEA-TCGG-PAN are investigated in detail. PETEA-TCGG-PAN with a high lithium-ion transference number (0.77) exhibits an electrochemical decomposition voltage of 5.15 V. Noticeably, the NCM811|PETEA-TCGG-PAN|Li battery can cycle at 2 C for 120 cycles with a capacity retention rate of 89%. Even at 6 C , the discharge specific capacity is able to reach 101.47 mAh g -1 . The combination of LiF and Li 2 CO 3 at the CEI interface is the reason for the improved rate performance. Moreover, when commercialized LFP is used as the cathode, the battery can also cycle stably for 150 cycles at 0.5 C . PETEA and PAN can together foster the transportation of Li + with the construction of a fast ion transport channel, making a contribution to stable charge-discharge of the above batteries. This study provides an innovative design philosophy for designing in situ GPEs in high-energy-density lithium metal batteries.

Aqueous batteries that use metal anodes exhibit maximum anodic capacity, whereas the energy density is still unsatisfactory partially due to the high redox potential of the metal anode. Current metal anodes are plagued by the dilemma that the redox potential of Zn is not low enough, whereas Al, Mg, and others with excessively low redox potential cannot work properly in aqueous electrolytes. Mn metal with a suitably low redox potential is a promising candidate, which was rarely explored before. Here, we report a rechargeable aqueous Mn-metal battery enabled by a well-designed electrolyte and robust inorganic-organic interfaces. The inorganic Sn-based interface with a bottom-up microstructure was constructed to preliminarily suppress water decomposition. With this bubble-free interface, the organic interface can be formed via an esterification reaction of sucrose triggered by acyl chloride in the electrolyte, generating a dense physical shield that isolates water while permitting Mn 2+ diffusion. Hence, a Mn symmetric cell achieves a superior plating/stripping stability for 200 hours, and a Mn||V 2 O 5 battery maintains approximately 100 % capacity after 200 cycles. Moreover, the Mn||V 2 O 5 battery realizes a much higher output voltage than that of the Zn||V 2 O 5 battery, evidencing the possibility of increasing the energy density through using a Mn anode. This work develops a systematic strategy to stabilize a Mn-metal anode for Mn-metal batteries, opening a new door towards enhanced voltage of aqueous batteries., (© 2022 Wiley-VCH GmbH.)

Highlights: Three-dimensional (3D) core-shell heterostructured Ni x S y @MnO x H y nanorods grown on nickel foam (Ni x S y @MnO x H y /NF) were successfully fabricated via a simple hydrothermal reaction and a subsequent electrodeposition process. The fabricated Ni x S y @MnO x H y /NF shows outstanding bifunctional activity and stability for hydrogen evolution reaction and oxygen evolution reaction, as well as overall-water-splitting performance. The main origins are the interface engineering of Ni x S y @MnO x H y , the shell-protection characteristic of MnO x H y , and the 3D open nanorod structure, which remarkably endow the electrocatalyst with high activity and stability. Exploring highly active and stable transition metal-based bifunctional electrocatalysts has recently attracted extensive research interests for achieving high inherent activity, abundant exposed active sites, rapid mass transfer, and strong structure stability for overall water splitting. Herein, an interface engineering coupled with shell-protection strategy was applied to construct three-dimensional (3D) core-shell Ni x S y @MnO x H y heterostructure nanorods grown on nickel foam (Ni x S y @MnO x H y /NF) as a bifunctional electrocatalyst. Ni x S y @MnO x H y /NF was synthesized via a facile hydrothermal reaction followed by an electrodeposition process. The X-ray absorption fine structure spectra reveal that abundant Mn-S bonds connect the heterostructure interfaces of Ni x S y @MnO x H y , leading to a strong electronic interaction, which improves the intrinsic activities of hydrogen evolution reaction and oxygen evolution reaction (OER). Besides, as an efficient protective shell, the MnO x H y dramatically inhibits the electrochemical corrosion of the electrocatalyst at high current densities, which remarkably enhances the stability at high potentials. Furthermore, the 3D nanorod structure not only exposes enriched active sites, but also accelerates the electrolyte diffusion and bubble desorption. Therefore, Ni x S y @MnO x H y /NF exhibits exceptional bifunctional activity and stability for overall water splitting, with low overpotentials of 326 and 356 mV for OER at 100 and 500 mA cm -2 , respectively, along with high stability of 150 h at 100 mA cm -2 . Furthermore, for overall water splitting, it presents a low cell voltage of 1.529 V at 10 mA cm -2 , accompanied by excellent stability at 100 mA cm -2 for 100 h. This work sheds a light on exploring highly active and stable bifunctional electrocatalysts by the interface engineering coupled with shell-protection strategy., (© 2022. The Author(s).)

The Li-O 2 battery has attracted substantial attention due to its high theoretical energy density. In particular, high-efficiency oxygen catalysts are very important for the design of practical Li-O 2 batteries. Herein, we have synthesized heterogeneous crystalline-coated partially crystalline bimetallic organic coordination polymers (PC@C-BMOCPs), which are further pyrolyzed to obtain Co- and Fe-based nanoparticles embedded within rodlike N-doped carbon (Co/Fe@NC) as a bifunctional oxygen reduction reaction/oxygen evolution reaction (ORR/OER) catalyst used in the Li-O 2 battery. Owing to excellent ORR/OER catalytic ability, the Co/Fe@NC bifunctional catalyst exhibits an efficient reversible reaction between O 2 and Li 2 O 2 . Additionally, a large number of mesoporous channels are present in the core-shell Co/Fe@NC nanoparticles. These channels not only promote the diffusion of Li + and O 2 , but also create ample room to store insoluble discharge product Li 2 O 2 . The Li-O 2 batteries utilizing the bifunctional Co/Fe@NC oxygen electrode exhibit a large capacity of 17,326 mAh g -1 , a long cycling life of more than 250 cycles, and excellent reversibility. This work provides a universally applicable strategy for designing nonnoble metal ORR/OER catalysts with excellent electrochemical performance for metal-air batteries.

Exploring highly active and stable bifunctional water-splitting electrocatalysts at ultra-high current densities is remarkably desirable. Herein, 3D nickel-iron phosphides nanosheets modified by MnO x nanoparticles are grown on nickel foam (MnO x /NiFeP/NF). Resulting from the electronic coupling effect enabled by interface modifications, the intrinsic activities of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are improved. Meanwhile, 3D nanosheets provide abundant active sites for HER and OER, leading to accelerating the reaction kinetics. Besides, the shell-protection characteristic of MnO x improves the durability of MnO x /NiFeP/NF. Therefore, MnO x /NiFeP/NF shows exceptional bifunctional electrocatalytic activities toward HER (an overpotential of 255 mV at 500 mA cm -2 ), OER (overpotentials of 296 and 346 mV at 500 and 1000 mA cm -2 , respectively), and overall water splitting (cell voltages of 1.796 and 1.828 V at 500 and 1000 mA cm -2 , respectively). Furthermore, it owns remarkably outstanding stability for overall water splitting at ultra-high current densities (120 and 70 h at 500 and 1000 mA cm -2 , respectively), which outperforms almost all of the non-noble metal electrocatalysts. This work presents efficient strategies of interface modifications, 3D nanostructures, and shell protection to afford ultra-high current densities., (© 2021 Wiley-VCH GmbH.)

Lithium metal batteries (LMBs) have received extensive attention and research interest as high specific energy systems. However, the issues of Li dendrites growth in LMBs restrict their practical applications. The development of lithiophilic collectors can effectively solve the issues of Li dendrites growth. This study reports excellent lithium storage performance of lithiophilic nanosheet arrays which consist of electronic conductor Ni and ionic conductor Li 2 O (Ni-LONSs) on Ni foil (NF) fabricated via a simple preparation method for LMBs. The ionic conductor Li 2 O of the Ni-LONSs layer is lithiophilic and can induce uniform Li deposition on the Ni-LONSs collector. In addition, the nanosheet array structure of the Ni-LONSs collector is beneficial to slow down the volume change of the Li plating/stripping. In comparison with the NF collector, due to the specific nanosheet array structure of Ni-LONSs collector, the Ni-LONSs collector demonstrates excellent coulombic efficiency of 97.2% after 280 cycles (95.7% after 100 cycles of NF collector) and satisfactory cycling lifespan of 340 h (about 120 h of NF collector) at 0.5 mA cm -2 with 1.0 mAh cm -2 . Furthermore, the Ni-LONSs collector shows superior electrochemical performance in Ni-LONS/Li∣LiFePO 4 full cells. The excellent lithium storage performance of Ni-LONSs collector with mixed ionic/electronic conductor is conducive to the development and practical applications of LMBs., (© 2021 IOP Publishing Ltd.)

Mn-based layered oxides are very attractive as cathodes for potassium-ion batteries (PIBs) due to their low-cost and environmentally friendly precursors. Their transfer to practical application, however, is inhibited by some issues including consecutive phase transitions, sluggish K + deintercalation/intercalation, and serious capacity loss. Herein, Mg-Ni co-substituted K 1/2 Mn 5/6 Mg 1/12 Ni 1/12 O 2 is designed as a promising cathode material for PIBs, with suppressed phase transitions that occurred in K 1/2 MnO 2 and improved K + storage performance. Part of Mg 2+ and Ni 2+ occupies the K + layer, playing the role of a "nailed pillar", which restrains metal oxide layer gliding during the K + (de)intercalation. The "Mg-Ni pinning effect" not only suppresses the phase transitions but also reduces the cell volume variation, leading to the improved cycle performance. Moreover, K 1/2 Mn 5/6 Mg 1/12 Ni 1/12 O 2 has low activation barrier energy for K + diffusion and high electron conductivity as demonstrated by first-principles calculations, resulting in better rate capability. In addition, K 1/2 Mn 5/6 Mg 1/12 Ni 1/12 O 2 also delivers a higher reversible capacity owing to the participation of the Ni element in electrochemical reactions and the pseudocapacitive contribution. This study provides a basic understanding of structural evolution in layered Mn-based oxides and broadens the strategic design of cathode materials for PIBs.

O3-type NaCrO 2 is attracting increasing attention as potential cathode material for sodium-ion batteries (SIBs). Bare NaCrO 2 is usually synthesized by a solid-state reaction and suffers from serious capacity decay and poor power capability. Modification by coating is an effective method to improve the electrochemical properties, but it inevitably reduces the energy density. To avoid the decrease of energy density and optimize the electrochemical performance, a specific route, i.e., a freeze-drying-assisted sol-gel method, has been adopted to synthesize bare NaCrO 2 in this work. Three-phase coexistence during charging is confirmed for the first time, which contributes to delaying the disappearance of the O3 phase and then improving the structural reversibility, resulting in superior cycle stability (∼50% capacity retention after 3000 cycles at 5C). Meanwhile, as-synthesized NaCrO 2 delivers an outstanding rate capability (82.1 mAh g -1 at 50C), which is attributed to the fast Na + diffusivity and high electronic conductivity proved by density functional theory (DFT) calculations. It is worth mentioning that NaCrO 2 also exhibits excellent electrochemical properties when used as a cathode for potassium-ion batteries (PIBs). This work provides new perspectives on the structural evolution of NaCrO 2 , and the results are expected to contribute to the development of SIBs and PIBs.

As bifunctional oxygen evolution/reduction electrocatalysts, transition-metal-based single-atom-doped nitrogen-carbon (NC) matrices are promising successors of the corresponding noble-metal-based catalysts, offering the advantages of ultrahigh atom utilization efficiency and surface active energy. However, the fabrication of such matrices (e.g., well-dispersed single-atom-doped M-N 4 /NCs) often requires numerous steps and tedious processes. Herein, ultrasonic plasma engineering allows direct carbonization in a precursor solution containing metal phthalocyanine and aniline. When combining with the dispersion effect of ultrasonic waves, we successfully fabricated uniform single-atom M-N 4 (M = Fe, Co) carbon catalysts with a production rate as high as 10 mg min -1 . The Co-N 4 /NC presented a bifunctional potential drop of ΔE = 0.79 V, outperforming the benchmark Pt/C-Ru/C catalyst (ΔE = 0.88 V) at the same catalyst loading. Theoretical calculations revealed that Co-N 4 was the major active site with superior O 2 adsorption-desorption mechanisms. In a practical Zn-air battery test, the air electrode coated with Co-N 4 /NC exhibited a specific capacity (762.8 mAh g -1 ) and power density (101.62 mW cm -2 ), exceeding those of Pt/C-Ru/C (700.8 mAh g -1 and 89.16 mW cm -2 , respectively) at the same catalyst loading. Moreover, for Co-N 4 /NC, the potential difference increased from 1.16 to 1.47 V after 100 charge-discharge cycles. The proposed innovative and scalable strategy was concluded to be well suited for the fabrication of single-atom-doped carbons as promising bifunctional oxygen evolution/reduction electrocatalysts for metal-air batteries.

Low-cost, high-activity, non-precious metal electrocatalysts are needed to enhance the bifunctional oxygen activities of rechargeable Zn-Air batteries. In this study, a Fe-enriched FeNi 3 inter-metallic nanoparticle/nitrogen-doped carbon (Fe-enriched-FeNi 3 /NC) electrocatalyst was designed and prepared using a facile method based on plasma engineering. The excess Fe-ions in the Fe-enriched FeNi 3 nanoparticles led to a high degree of lattice distortion that produced abundant oxygen-active sites. The electrocatalyst exhibited excellent oxygen evolution reaction (OER) activity as well as favorable oxygen reduction reaction (ORR) activity in an alkaline electrolyte. In addition, the electrocatalyst revealed a lower potential difference (ΔE = 0.80 V vs. RHE) in a bifunctional oxygen reaction compared to that of the benchmark 20 wt% Pt/C + Ir/C (ΔE = 0.84 V vs. RHE), and most of the reported FeNi 3 alloy-doped carbon catalysts. Based on DFT calculations, the lattice distortion in Fe-enriched-FeNi 3 /NC promoted a higher density of active electrons around the Fermi level. Owing to its great bifunctional oxygen activities, Fe-enriched FeNi 3 /NC was applied as an ORR/OER catalyst in the air cathode in a homemade zinc-air battery and exhibited an excellent discharge-charge voltage gap (0.89 V), peak power density (89 mW/cm 2 ), and high specific capacity of 734 mAh/g at 20 mA/cm 2 , which outperformed the benchmark 20 wt% Pt/C + Ir/C electrocatalyst. In summary, this research provides a novel strategy to enhance the OER/ORR activities of transition metal-based alloys through lattice distortion defects. In addition, it provides a new pathway for achieving noble metal-free air cathode materials for the next generation Zn-air battery., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Lithium metal anodes (LMAs) are critical for high-energy-density batteries such as Li-S and Li-O 2 batteries. The spontaneously formed solid electrolyte interface on LMAs is fragile, which may not accommodate the cyclic Li plating/stripping. This usually will result in a low coulombic efficiency (CE), short cycle life, and potential safety hazards induced by the uncontrollable growth of lithium dendrites. In this study, we fabricate a Li alginate-based artificial SEI (ASEI) layer that is chemically stable and allows easy Li ion transport on the surface of LMAs, thus enabling the stable operation of lithium metal anodes. Compared to bare LMAs, the ASEI layer-protected LMAs exhibit a more stable Li plating/stripping behavior and present effective dendrite suppression. The symmetric Li∥Li cells with the ASEI layer-protected LMAs can stably run for 850 and 350 h at current densities of 0.5 and 1 mA cm -2 , respectively. Additionally, the LiFePO 4 ∥Li full cell with the ASEI layer-protected LMA exhibits a capacity retention of about 94.0% coupled with a CE of 99.6% after 1000 cycles at 4 C. We believe that this study of engineering an ASEI brings a new and promising approach to the stabilization of LMAs for high-performance lithium metal batteries.

A multifunctional coating with high ionic and electronic conductivity is constructed on the surface of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM) to boost the battery stability upon cycling and during storage as well. Phosphoric acid reacts with residual lithium species on the pristine NCM to form a Li 3 PO 4 coating with extra carbon nanotubes (CNTs) penetrating through, which shows high ionic and electronic conductivity. NCM, Li 3 PO 4 , CNTs, and the electrolyte jointly form a four-phase cathode electrolyte interface, which plays a key role in the great enhancement of capacity retention, from 50.3% for pristine NCM to 84.8% for the modified one after 500 cycles at 0.5C at room temperature. The modified NCM also delivers superior electrochemical performances at a high cut-off voltage (4.5 V), high temperature (55 °C), and high rate (10C). Furthermore, it can deliver 154.2 mA h g -1 at the 500th cycle after exposed to air with high humidity for 2 weeks. These results demonstrate that the well-constructed multifunctional coating can remarkably enhance the chemical and electrochemical performances of NCM. The improved cycling, storage, and rate performance are attributed to the four-phase cathode electrolyte interface delivering high electron and ionic conductivity and securing the cathode against attack. This work broadens the horizon for constructing effective electrode/electrolyte interfaces for electrochemical energy storage and conversion.

The metal-air battery is a form of renewable energy generation technology that produces energy electrochemically and can address energy concerns in the near future. However, state-of-the-art Pt electrocatalysts often suffer from agglomeration or detachment from carbon supports under prolonged operation, eventually limiting the long-term utilization of metal-air batteries. In this work, Pt nanoparticles were deposited on sulfur-doped nanocarbon to increase its stability. We first synthesized sulfur-doped (S-doped) and pristine carbon as support materials via a plasma process, and thereafter loaded platinum (Pt) nanoparticles onto the S-doped and pristine carbon matrix. From a sintering test at 600 °C, the Pt nanoparticles supported on pristine carbon increased from 2.4 to 5.2 nm; meanwhile, the average size of Pt NPs supported on S-doped carbon only increased from 2.2 to 2.51 nm. From the electrochemical analyses, the mass activity of Pt on pristine and S-doped carbon supports decreased by 25% and 10%, respectively, after 1500 cycles. The results proposed that the sulfide C-S-C bond provided a strong platinum-S-doped carbon support interaction between the support materials and the loaded Pt nanoparticles. Thus, S-doped carbon supports can serve as a stabilizer of Pt nanoparticles to enhance their durability in the application of metal-air batteries and other electrochemical devices.

Lithium-sulfur (Li-S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the "shuttle effect" of the sulfur cathode, resulting in poor cyclic performance, is a big barrier for the development of Li-S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal-organic framework (MOF)-derived N-doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm -2 ) and exhibit large specific capacities at different C-rates. Specially, an outstanding long-term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high-energy-density Li-S batteries., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Highly efficient and low-cost nonprecious metal electrocatalysts that favor a four-electron pathway for the oxygen reduction reaction (ORR) are essential for high-performance metal-air batteries. Herein, we show an ultrasonication-assisted synthesis method to prepare Mn 3 O 4 quantum dots (QDs, ca. 2 nm) anchored on nitrogen-doped partially exfoliated multiwall carbon nanotubes (Mn 3 O 4 QDs/N-p-MCNTs) as a high-performance ORR catalyst. The Mn 3 O 4 QDs/N-p-MCNTs facilitated the four-electron pathway for the ORR and exhibited sufficient catalytic activity with an onset potential of 0.850 V (vs reversible hydrogen electrode), which is only 38 mV less positive than that of Pt/C (0.888 V). In addition, the Mn 3 O 4 QDs/N-p-MCNTs demonstrated superior stability than Pt/C in alkaline solutions. Furthermore, a Zn-air battery using the Mn 3 O 4 QDs/N-p-MCNTs cathode catalyst successfully generated a specific capacity of 745 mA h g -1 at 10 mA cm -2 without the loss of voltage after continuous discharging for 105 h. The superior ORR activity of Mn 3 O 4 QDs/N-p-MCNTs can be ascribed to the homogeneous Mn 3 O 4 QDs loaded onto the N-doped carbon skeleton and the synergistic effects of Mn 3 O 4 QDs, nitrogen, and carbon nanotubes. The interface binding energy of -3.35 eV calculated by the first-principles density functional theory method illustrated the high stability of the QD-anchored catalyst. The most stable adsorption structure of O 2 , at the interface between Mn 3 O 4 QDs and the graphene layer, had the binding energy of -1.17 eV, greatly enhancing the ORR activity. In addition to the high ORR activity and stability, the cost of production of Mn 3 O 4 QDs/N-p-MCNTs is low, which will broadly facilitate the real application of metal-air batteries.

Rechargeable lithium metal anodes (LMAs) with long cycling life have been regarded as the "Holy Grail" for high-energy-density lithium metal secondary batteries. The skeleton plays an important role in determining the performance of LMAs. Commercially available copper foam (CF) is not normally regarded as a suitable skeleton for stable lithium storage owing to its relatively inappropriate large pore size and relatively low specific surface area. Herein, for the first time, we revisit CF and address these issues by rationally designing a highly porous copper (HPC) architecture grown on CF substrates (HPC/CF) as a three-dimensional (3D) hierarchically bicontinuous porous skeleton through a novel approach combining the self-assembly of polystyrene microspheres, electrodeposition of copper, and a thermal annealing treatment. Compared to the CF skeleton, the HPC/CF skeleton exhibits a significantly improved Li plating/stripping behavior with high Coulombic efficiency (CE) and superior Li dendrite growth suppression. The 3D HPC/CF-based LMAs can run for 620 h without short-circuiting in a symmetric Li/Li@Cu cell at 0.5 mA cm -2 , and the Li@Cu/LiFePO 4 full cell exhibits a high reversible capacity of 115 mAh g -1 with a high CE of 99.7% at 2 C for 500 cycles. These results demonstrate the effectiveness of the design strategy of 3D hierarchically bicontinuous porous skeletons for developing stable and safe LMAs.

A peculiar nanostructure consisting of nitrogen-doped, carbon-encapsulated (N-C) SnO2@Sn nanoparticles grafted on three-dimensional (3D) graphene-like networks (designated as N-C@SnO2@Sn/3D-GNs) has been fabricated via a low-cost and scalable method, namely an in situ hydrolysis of Sn salts and immobilization of SnO2 nanoparticles on the surface of 3D-GNs, followed by an in situ polymerization of dopamine on the surface of the SnO2/3D-GNs, and finally a carbonization. In the composites, three-layer core-shell N-C@SnO2@Sn nanoparticles were uniformly grafted onto the surfaces of 3D-GNs, which promotes highly efficient insertion/extraction of Li(+). In addition, the outermost N-C layer with graphene-like structure of the N-C@SnO2@Sn nanoparticles can effectively buffer the large volume changes, enhance electronic conductivity, and prevent SnO2/Sn aggregation and pulverization during discharge/charge. The middle SnO2 layer can be changed into active Sn and nano-Li2O during discharge, as described by SnO2 + Li(+) → Sn + Li2O, whereas the thus-formed nano-Li2O can provide a facile environment for the alloying process and facilitate good cycling behavior, so as to further improve the cycling performance of the composite. The inner Sn layer with large theoretical capacity can guarantee high lithium storage in the composite. The 3D-GNs, with high electrical conductivity (1.50 × 10(3) S m(-1)), large surface area (1143 m(2) g(-1)), and high mechanical flexibility, tightly pin the core-shell structure of the N-C@SnO2@Sn nanoparticles and thus lead to remarkably enhanced electrical conductivity and structural integrity of the overall electrode. Consequently, this novel hybrid anode exhibits highly stable capacity of up to 901 mAh g(-1), with ∼89.3% capacity retention after 200 cycles at 0.1 A g(-1) and superior high rate performance, as well as a long lifetime of 500 cycles with 84.0% retention at 1.0 A g(-1). Importantly, this unique hybrid design is expected to be extended to other alloy-type anode materials such as silicon, germanium, etc.

Nano-Germanium/polypyrrole composite has been synthesized by chemical reduction method in aqueous solution. The Ge nanoparticles were directly coated on the surface of the polypyrrole. The morphology and structural properties of samples were determined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis was carried out to determine the polypyrrole content. The electrochemical properties of the samples have been investigated and their suitability as anode materials for the lithium-ion battery was examined. The discharge capacity of the Ge nanoparticles calculated in the Ge-polypyrrole composite is 1014 mAh g(-1) after 50 cycles at 0.2 C rate, which is much higher than that of pristine germanium (439 mAh g(-1)). The composite also demonstrates high specific discharge capacities at different current rates (1318, 1032, 661, and 460 mAh g(-1) at 0.5, 1.0, 2.0, and 4.0 C, respectively). The superior electrochemical performance of Ge-polypyrrole composite could be attributed to the polypyrrole core, which provides an efficient transport pathway for electrons. SEM images of the electrodes have demonstrated that polypyrrole can also act as a conductive binder and alleviate the pulverization of electrode caused by the huge volume changes of the nanosized germanium particles during Li(+) intercalation/de-intercalation.

ZnFe(2)O(4)/C hollow spheres have been synthesized via a facile solvothermal route using low cost raw materials. The resulting composite showed a very high specific capacity of 841 mAh g(-1) after 30 cycles and good rate capability., (This journal is © The Royal Society of Chemistry 2011)