Monolayer MoS2 Fabricated by In Situ Construction of Interlayer Electrostatic Repulsion Enables Ultrafast Ion Transport in Lithium-Ion Batteries

p-n heterogeneous Sb2S3/SnO2 quantum dot anchored reduced graphene oxide nanosheets for high-performance lithium-ion batteries

Antimony sulfide (Sb2S3) has a high theoretical specific capacity due to its two reaction mechanisms of conversion and alloying during the Li+-(de)intercalation process, thus becoming a promising lithium-ion battery (LIB) anode material. However, its poor inherent conductivity and large volume expansion during repeated Li+-(de)intercalation processes greatly hinder the in-depth development of Sb2S3 based LIB anode materials. Herein, an Sb2S3/SnO2@rGO composite was prepared by using an interface engineering technique involving metal-containing ionic liquid precursors, in which Sb2S3/SnO2 quantum dots (QDs) as p-n heterojunctions are uniformly anchored on the surface of reduced graphene oxide (rGO). The p-n heterogeneous interface between Sb2S3 and SnO2 QDs induces an internal electric field, promoting the electronic/ion transport during electrochemical reactions, and the QD-sized Sb2S3/SnO2 heterostructure with a larger surface area provides more active sites for Li+-(de)intercalation reactions. In addition, the rGO matrix acts as a buffer to prevent the aggregation of active Sb2S3 and SnO2 QDs, alleviate the volume expansion, and enhance the conductivity of the composite during repeated cycles. These advantages endow the designed Sb2S3/SnO2@rGO electrode with excellent reaction kinetics and good long cycling stability. As an anode material of LIBs, it can still provide a reversible specific capacity of 474 mA h g-1 after 2000 cycles at a high current density of 3.0 A g-1, which is superior to those of most of the previously reported Sb2S3-based carbon materials. The p-n heterostructure construction strategy of nano-metal sulfide/metal oxides in this work can provide inspiration for the design and synthesis of other advanced energy storage materials.

Trimetallic sulfides coated with N-doped carbon nanorods as superior anode for lithium-ion batteries

Metal sulfides have been considered promising anode materials for lithium-ion batteries (LIBs), due to their high capacity. However, the poor cycle stability induced by the sluggish kinetics and poor structural stability hampers their practical application in LIBs. In this work, MoS2/MnS/SnS trimetallic sulfides heterostructure coated with N-doped carbon nanorods (MMSS@NC) is designed through a simple method involving co-precipitation, metal chelate-assisted reaction, and in-situ sulfurization method. In such designed MMSS@NC, a synergetic effect of heterojunctions and carbon layer is simultaneously constructed, which can significantly improve ionic and electronic diffusion kinetics, as well as maintain the structural stability of MMSS@NC during the repeated lithiation/delithiation process. When applied as anode materials for LIBs, the MMSS@NC composite shows superior long-term cycle performance (1145.0 mAh/g after 1100 cycles at 1.0 A/g), as well as excellent rate performance (565.3 mAh/g at 5.0 A/g). This work provides a unique strategy for the construction of multiple metal sulfide anodes for high-performance LIBs.

Dual carbon engineering enabling 1T/2H MoS2 with ultrastable potassium ion storage performance

Potassium-ion batteries (PIBs) as a promising and low-cost battery technology offer the advantage of utilizing abundant and cost-effective K-salt sources. However, the effective adoption of PIBs necessitates the identification of suitable electrode materials. The 1T phase of MoS2 exhibits enhanced electronic conductivity and greater interlayer spacing compared to the 2H phase, leading to a capable potassium ion storage ability. Herein, we fabricated dual carbon engineered 1T/2H MoS2via a secure and straightforward ammonia-assisted hydrothermal method. The 1T/2H MoS2@rGO@C structure demonstrated an expanded interlayer spacing (9.3 Å). Additionally, the sandwich-like structural design not only enhanced material conductivity but also effectively curbed the agglomeration of nanosheets. Remarkably, 1T/2H MoS2@rGO@C exhibited impressive potassium storage ability, delivering capacities of 351.0 mA h g-1 at 100 mA g-1 and 233.8 mA h g-1 at 1000 mA g-1 following 100 and 1000 cycles, respectively. Moreover, the construction of a K-ion full cell was successfully achieved, utilizing perylene tetracarboxylic dianhydride (PTCDA) as the cathode, and manifesting a capacity of 294.3 mA h g-1 at 100 mA g-1 after 160 cycles. This underscores the substantial potential of employing the 1T/2H MoS2@rGO@C electrode material for PIBs.

Macroporous Directed and Interconnected Carbon Architectures Endow Amorphous Silicon Nanodots as Low-Strain and Fast-Charging Anode for Lithium-Ion Batteries

Fabricating low-strain and fast-charging silicon-carbon composite anodes is highly desired but remains a huge challenge for lithium-ion batteries. Herein, we report a unique silicon-carbon composite fabricated by uniformly dispersing amorphous Si nanodots (SiNDs) in carbon nanospheres (SiNDs/C) that are welded on the wall of the macroporous carbon framework (MPCF) by vertical graphene (VG), labeled as MPCF@VG@SiNDs/C. The high dispersity and amorphous features of ultrasmall SiNDs (~ 0.7 nm), the flexible and directed electron/Li+ transport channels of VG, and the MPCF impart the MPCF@VG@SiNDs/C more lithium storage sites, rapid Li+ transport path, and unique low-strain property during Li+ storage. Consequently, the MPCF@VG@SiNDs/C exhibits high cycle stability (1301.4 mAh g-1 at 1 A g-1 after 1000 cycles without apparent decay) and high rate capacity (910.3 mAh g-1, 20 A g-1) in half cells based on industrial electrode standards. The assembled pouch full cell delivers a high energy density (1694.0 Wh L-1; 602.8 Wh kg-1) and an excellent fast-charging capability (498.5 Wh kg-1, charging for 16.8 min at 3 C). This study opens new possibilities for preparing advanced silicon-carbon composite anodes for practical applications.

Hierarchical Spatial Confinement Unlocking the Storage Limit of MoS2 for Flexible High-Energy Supercapacitors

Molybdenum sulfide (MoS2) is a promising electrode material for supercapacitors; however, its limited Mo/S edge sites and intrinsic inert basal plane give rise to sluggish active electronic states, thus constraining its electrochemical performance. Here we propose a hierarchical confinement strategy to develop ethylene molecule (EG)-intercalated Co-doped sulfur-deficient MoS2 (Co-EG/SV-MoS2) for efficient and durable K-ion storage. Theoretical analyses suggest that the intercalation-confined EG and lattice-confined Co can enhance the interfacial K-ion storage capacity while reducing the K-ion diffusion barrier. Experimentally, the intercalated EG molecules with mildly reducing properties induced the creation of sulfur vacancies, expanded the interlayer spacing, regulated the 2H-1T phase transition, and strengthened the structural grafting between layers, thereby facilitating ion diffusion and ensuring structural durability. Moreover, the Co dopants occupying the initial Mo sites initiated charge transfer, thus activating the basal plane. Consequently, the optimized Co-EG/SV-MoS2 electrode exhibited a substantially improved electrochemical performance. Flexible supercapacitors assembled with Co-EG/SV-MoS2 delivered a notable areal energy density of 0.51 mW h cm-2 at 0.84 mW cm-2 with good flexibility. Furthermore, supercapacitor devices were integrated with a strain sensor to create a self-powered system capable of real-time detection of human joint motion.

Boosting Charge Transport and Catalytic Performance in MoS2 by Zn2+ Intercalation Engineering for Lithium-Sulfur Batteries

Transition metal dichalcogenides (TMDs) have been widely studied as catalysts for lithium-sulfur batteries due to their good catalytic properties. However, their poor electronic conductivity leads to slow sulfur reduction reactions. Herein, a simple Zn2+ intercalation strategy was proposed to promote the phase transition from semiconducting 2H-phase to metallic 1T-phase of MoS2. Furthermore, the Zn2+ between layers can expand the interlayer spacing of MoS2 and serve as a charge transfer bridge to promote longitudinal transport along the c-axis of electrons. DFT calculations further prove that Zn-MoS2 possesses better charge transfer ability and stronger adsorption capacity. At the same time, Zn-MoS2 exhibits excellent redox electrocatalytic performance for the conversion and decomposition of polysulfides. As expected, the lithium-sulfur battery using Zn0.12MoS2-carbon nanofibers (CNFs) as the cathode has high specific capacity (1325 mAh g-1 at 0.1 C), excellent rate performance (698 mAh g-1 at 3 C), and outstanding cycle performance (it remains 604 mAh g-1 after 700 cycles with a decay rate of 0.045% per cycle). This study provides valuable insights for improving electrocatalytic performance of lithium-sulfur batteries.

Textured Asymmetric Membrane Electrode Assemblies of Piezoelectric Phosphorene and Ti3C2Tx MXene Heterostructures for Enhanced Electrochemical Stability and Kinetics in LIBs

Black phosphorus with a superior theoretical capacity (2596 mAh g-1) and high conductivity is regarded as one of the powerful candidates for lithium-ion battery (LIB) anode materials, whereas the severe volume expansion and sluggish kinetics still impede its applications in LIBs. By contrast, the exfoliated two-dimensional phosphorene owns negligible volume variation, and its intrinsic piezoelectricity is considered to be beneficial to the Li-ion transfer kinetics, while its positive influence has not been discussed yet. Herein, a phosphorene/MXene heterostructure-textured nanopiezocomposite is proposed with even phosphorene distribution and enhanced piezo-electrochemical coupling as an applicable free-standing asymmetric membrane electrode beyond the skin effect for enhanced Li-ion storage. The experimental and simulation analysis reveals that the embedded phosphorene nanosheets not only provide abundant active sites for Li-ions, but also endow the nanocomposite with favorable piezoelectricity, thus promoting the Li-ion transfer kinetics by generating the piezoelectric field serving as an extra accelerator. By waltzing with the MXene framework, the optimized electrode exhibits enhanced kinetics and stability, achieving stable cycling performances for 1,000 cycles at 2 A g-1, and delivering a high reversible capacity of 524 mAh g-1 at - 20 ℃, indicating the positive influence of the structural merits of self-assembled nanopiezocomposites on promoting stability and kinetics.

Interfacial engineering of transition metal dichalcogenide/carbon heterostructures for electrochemical energy applications

To support the global goal of carbon neutrality, numerous efforts have been devoted to the advancement of electrochemical energy conversion (EEC) and electrochemical energy storage (EES) technologies. For these technologies, transition metal dichalcogenide/carbon (TMDC/C) heterostructures have emerged as promising candidates for both electrode materials and electrocatalysts over the past decade, due to their complementary advantages. It is worth noting that interfacial properties play a crucial role in establishing the overall electrochemical characteristics of TMDC/C heterostructures. However, despite the significant scientific contribution in this area, a systematic understanding of TMDC/C heterostructures' interfacial engineering is currently lacking. This literature review aims to focus on three types of interfacial engineering, namely interfacial orientation engineering, interfacial stacking engineering, and interfacial doping engineering, of TMDC/C heterostructures for their potential applications in EES and EEC devices. To accomplish this goal, a combination of experimental and theoretical approaches was used to allow the analysis and summary of the fundamental electrochemical properties and preparation strategies of TMDC/C heterostructures. Moreover, this review highlights the design and utilization of the interfacial engineering of TMDC/C heterostructures for specific EES and EEC devices. Finally, the challenges and opportunities of using interfacial engineering of TMDC/C heterostructures in practical EES and EEC devices are outlined. We expect that this review will effectively guide readers in their understanding, design, and application of interfacial engineering of TMDC/C heterostructures.

Kinetic Limits of Graphite Anode for Fast-Charging Lithium-Ion Batteries

Fast-charging lithium-ion batteries are highly required, especially in reducing the mileage anxiety of the widespread electric vehicles. One of the biggest bottlenecks lies in the sluggish kinetics of the Li+ intercalation into the graphite anode; slow intercalation will lead to lithium metal plating, severe side reactions, and safety concerns. The premise to solve these problems is to fully understand the reaction pathways and rate-determining steps of graphite during fast Li+ intercalation. Herein, we compare the Li+ diffusion through the graphite particle, interface, and electrode, uncover the structure of the lithiated graphite at high current densities, and correlate them with the reaction kinetics and electrochemical performances. It is found that the rate-determining steps are highly dependent on the particle size, interphase property, and electrode configuration. Insufficient Li+ diffusion leads to high polarization, incomplete intercalation, and the coexistence of several staging structures. Interfacial Li+ diffusion and electrode transportation are the main rate-determining steps if the particle size is less than 10 μm. The former is highly dependent on the electrolyte chemistry and can be enhanced by constructing a fluorinated interphase. Our findings enrich the understanding of the graphite structural evolution during rapid Li+ intercalation, decipher the bottleneck for the sluggish reaction kinetics, and provide strategic guidelines to boost the fast-charging performance of graphite anode.

Boosting Lean Electrolyte Lithium-Sulfur Battery Performance with Transition Metals: A Comprehensive Review

Lithium-sulfur (Li-S) batteries have received widespread attention, and lean electrolyte Li-S batteries have attracted additional interest because of their higher energy densities. This review systematically analyzes the effect of the electrolyte-to-sulfur (E/S) ratios on battery energy density and the challenges for sulfur reduction reactions (SRR) under lean electrolyte conditions. Accordingly, we review the use of various polar transition metal sulfur hosts as corresponding solutions to facilitate SRR kinetics at low E/S ratios (< 10 µL mg-1), and the strengths and limitations of different transition metal compounds are presented and discussed from a fundamental perspective. Subsequently, three promising strategies for sulfur hosts that act as anchors and catalysts are proposed to boost lean electrolyte Li-S battery performance. Finally, an outlook is provided to guide future research on high energy density Li-S batteries.