Dimercaptan–polyaniline composite electrodes for lithium batteries with high energy density

B3S2 monolayer as an anode material for Na/K-ion batteries: a first-principles study

Two-dimensional (2D) materials used as anodes in metal-ion batteries have attracted increased attention due to their high specific surface area, abundant active sites and good electronic properties. Searching for 2D materials with high storage capacities and low diffusion energy barriers is one of the most effective ways to design novel anode materials. In this work, based on first-principles calculations, we design a new 2D B3S2 monolayer with high thermodynamic and dynamic stability. The obtained B3S2 monolayer has a high cohesive energy, ensuring the feasibility of experimental synthesis. These characteristics of the B3S2 monolayer prompt us to explore its application as an anode material. The B3S2 monolayer exhibits not only a metallic nature but also a low diffusion energy barrier (0.037 eV) and open-circuit voltage (0.09 V). More importantly, the B3S2 monolayer shows a very high theoretical capacity of 1658 mA h g-1 as an anode material for sodium-ion batteries, which is comparable to other similar or common 2D materials. All of these intriguing properties make the B3S2 monolayer a promising 2D anode material for sodium-ion batteries.

Interfacial effects on lithium-ion diffusion in two-dimensional lateral black phosphorus-graphene heterostructures

Lateral heterostructures constructed from different two-dimensional (2D) materials can be potentially used in lithium-ion batteries (LIBs). The interface between two different components strongly affects LIB charge and discharge processes. Herein, the atomic structures, electronic properties, and Li-ion diffusion characteristics of lateral black phosphorus-graphene (BP-G) heterostructures are studied via first-principles calculations. The obtained results reveal that BP-G heterostructures with either zigzag (ZZ) or misoriented interfaces constructed according to Clar's rule possess a small number of interfacial states and are electronically stable. Furthermore, compared with the perfect ZZ interface of BP-G, Clar's interfaces provide a larger number of diffusion paths with much lower energy barriers. The findings of this study suggest that lateral BP-G heterostructures can provide insights for rapid charge and discharge processes in LIBs.

Storing Mg Ions in Polymers: A Perspective

The electrochemical performance of rechargeable Mg batteries (RMBs) is primarily determined by the cathodes. However, the strong interaction between highly polarized Mg²⁺ and the host lattice is a big challenge for inorganic cathode materials. While endowed with weak interaction with Mg²⁺ , organic polymers are capable of fast reaction kinetics. Besides, with the advantages of light weight, abundance, low cost, and recyclability, polymers are deemed as ideal cathode materials for RMBs. Although polymer cathodes have remarkably progressed in recent years, there are still significant challenges to overcome before reaching practical application. In this perspective, the challenges faced by polymer cathodes are critically focused, followed by the retrospection of efforts devoted to design polymers. Some feasible strategies are proposed to explore new structures and chemistries for the practical application of polymer cathodes in RMBs.

Synthesis and Characterization of Redox-Responsive Disulfide Cross-Linked Polymer Particles for Energy Storage Applications

Cross-linking poly(glycidyl methacrylate) microparticles with redox-responsive bis(5-amino-l,3,4-thiadiazol-2-yl) disulfide moieties yield redox-active particles (RAPs) capable of electrochemical energy storage via a reversible 2-electron reduction of the disulfide bond. The resulting RAPs show improved electrochemical reversibility compared to a small-molecule disulfide analogue in solution, attributed to spatial confinement of the polymer-grafted disulfides in the particle. Galvanostatic cycling was used to investigate the impact of electrolyte selection on stability and specific capacity. A dimethyl sulfoxide/magnesium triflate electrolyte was ultimately selected for its favorable electrochemical reversibility and specific capacity. Additionally, the specific capacity showed a strong dependence on particle size where smaller particles yielded higher specific capacity. Overall, these experiments offer a promising direction in designing synthetically facile and electrochemically stable materials for organosulfur-based multielectron energy storage coupled with beyond Li ion systems such as Mg.

First-principles study on h-BSi3 sheet as a promising high-performance anode for sodium-ion batteries

Seeking cheap, efficient and sustainable alternatives to lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) has emerged as a realm of research, due to the abundance of Na in the earth's crust. We have investigated the relative performance of novel intrinsically metallic h-BSi₃ (BS) sheet as an anode for SIBs, compared to LIBs, through Density Functional Theory studies. Our calculations show that BS has higher chemisorption interactions with Na than Li atoms while drawing substantial electron densities from both, turning them into cations. BS is able to reach a high specific capacity of 1127.62 mA h g^-1 for Na, while only as half of that for Li, at ambient temperatures ranging 300-600 K. The moderate sodiation (0.77 V) and lithiation (0.79 V) voltages facilitate BS to prevent the SEI layer formation, metal plating and harmful dendrite growth and to maintain good energy density. BS retains good electronic and ionic conductivities after hosting both Na and Li adatoms, while the former diffuses with about as half the barriers as those of the latter, supporting faster charge/discharge rate and greater preservation of storage capacities in high current densities when BS is used as an anode in SIBs. Na adsorptions cause relatively lower structural deformations to BS, and refrain from forming clusters, leading to good cyclic stability. The superior electrochemical performance of Na, thus, makes BS a potential anode material for SIBs.

Redox-active zinc thiolates for low-cost aqueous rechargeable Zn-ion batteries

Aqueous zinc-ion batteries (AZIBs) are promising candidates for large-scale electrical energy storage due to the inexpensive, safe, and non-toxic nature of zinc. One key area that requires further development is electrode materials that store Zn²⁺ ions with high reversibility and fast kinetics. To determine the viability of low-cost organosulfur compounds as OEMs for AZIBs, we investigate how structural modification affects electrochemical performance in Zn-thiolate complexes 1 and 2. Remarkably, modification of one thiolate in 1 to sulfide in 2 reduces the voltage hysteresis from 1.04 V to 0.15 V. While 1 exhibits negligible specific capacity due to the formation of insulating DMcT polymers, 2 delivers a capacity of 107 mA h g⁻¹ with a primary discharge plateau at 1.1 V vs. Zn²⁺/Zn. Spectroscopic studies of 2 suggest a Zn²⁺ and H⁺ co-insertion mechanism with Zn²⁺ as the predominant charge carrier. Capacity fading in Zn-2 cells likely results from the formation of (i) soluble H⁺ insertion products and (ii) non-redox-active side products. Increasing electrolyte concentration and using a Nafion membrane significantly enhances the stability of 2 by suppressing H⁺ insertion. Our findings provide insight into the molecular design strategies to reduce the polarization potential and improve the cycling stability of the thiolate/disulfide redox couple in aqueous battery systems.

This study demonstrates the viability of the thiolate/disulfide redox couple in AZIB applications, and provides an in-depth study on the electrochemical mechanism of Zn-thiolates electrode materials.

Polymerization of Aniline Derivatives to Yield Poly[N,N-(phenylamino)disulfides] as Polymeric Auxochromes

Polymerizations of phenylamines with a disulfide transfer reagent to yield poly[N,N-(phenylamino) disulfides] (poly-NADs) were investigated due to their unique repeat units that resulted in conjugation along the backbone that was perturbed by the aromatic rings and gave different colors for the polymers. These polymers were synthesized from 10 different anilines and sulfur monochloride in a step-growth polymerization. The polymers were characterized by nuclear magnetic resonance spectroscopy, size exclusion chromatography-multiangle light scattering, and UV-vis spectroscopy. These polymers possessed a polymeric backbone solely consisting of nitrogen and sulfur [-N(R)SS-], which was conjugated and yielded polymers of moderate molecular weight. Most notably, these polymers were an array of colors ranging from pale yellow to a deep purple depending on the substitution of the aromatic ring. The more electron-poor systems produced lighter yellow polymers, while the electron-rich systems gave orange, green, red, and even purple polymers.

Multiscale Understanding of Covalently Fixed Sulfur-Polyacrylonitrile Composite as Advanced Cathode for Metal-Sulfur Batteries

Metal-sulfur batteries (MSBs) provide high specific capacity due to the reversible redox mechanism based on conversion reaction that makes this battery a more promising candidate for next-generation energy storage systems. Recently, along with elemental sulfur (S8 ), sulfurized polyacrylonitrile (SPAN), in which active sulfur moieties are covalently bounded to carbon backbone, has received significant attention as an electrode material. Importantly, SPAN can serve as a universal cathode with minimized metal-polysulfide dissolution because sulfur is immobilized through covalent bonding at the carbon backbone. Considering these unique structural features, SPAN represents a new approach beyond elemental S8 for MSBs. However, the development of SPAN electrodes is in its infancy stage compared to conventional S8 cathodes because several issues such as chemical structure, attached sulfur chain lengths, and over-capacity in the first cycle remain unresolved. In addition, physical, chemical, or specific treatments are required for tuning intrinsic properties such as sulfur loading, porosity, and conductivity, which have a pivotal role in improving battery performance. This review discusses the fundamental and technological discussions on SPAN synthesis, physicochemical properties, and electrochemical performance in MSBs. Further, the essential guidance will provide research directions on SPAN electrodes for potential and industrial applications of MSBs.

2D Redox-Active Covalent Organic Frameworks for Supercapacitors: Design, Synthesis, and Challenges

Due to the tunable skeletons, variable pore environments, and predesignable structures, covalent organic frameworks (COFs) can be served as a versatile platform to tailor redox activities for efficient energy storage. Redox-active COFs with specific functional groups can not only promote high-speed mass transport in the permanently open channels, but also provide dense active sites for reversible redox reactions so as to efficiently adsorb the electrolyte ions, thus becoming emerging and promising electroactive materials. This review summarizes the design principles and synthetic methods of redox-active COFs, with a focus on surveying the representative advances in supercapacitors. The key progress, major challenges, and future directions in this promising field are highlighted as well.

Conjugated sulfonamides as a class of organic lithium-ion positive electrodes

The applicability of organic battery materials in conventional rocking-chair lithium (Li)-ion cells remains deeply challenged by the lack of Li-containing and air-stable organic positive electrode chemistries. Decades of experimental and theoretical research in the field has resulted in only a few recent examples of Li-reservoir materials, all of which rely on the archetypal conjugated carbonyl redox chemistry. Here we extend the chemical space of organic Li-ion positive electrode materials with a class of conjugated sulfonamides (CSAs) and show that the electron delocalization on the sulfonyl groups endows the resulting CSAs with intrinsic oxidation and hydrolysis resistance when handled in ambient air, and yet display reversible electrochemistry for charge storage. The formal redox potential of the uncovered CSA chemistries spans a wide range between 2.85 V and 3.45 V (versus Li⁺/Li⁰), finely tunable through electrostatic or inductive molecular design. This class of organic Li-ion positive electrode materials challenges the realm of the inorganic battery cathode, as this first generation of CSA chemistries already displays gravimetric energy storage metrics comparable to those of the stereotypical LiFePO₄.

Redox Potential Tuning of s-Tetrazine by Substitution of Electron-Withdrawing/Donating Groups for Organic Electrode Materials

Herein, we tune the redox potential of 3,6-diphenyl-1,2,4,5-tetrazine (DPT) by introducing various electron-donating/withdrawing groups (methoxy, t-butyl, H, F, and trifluoromethyl) into its two peripheral benzene rings for use as electrode material in a Li-ion cell. By both the theoretical DFT calculations and the practical cyclic voltammetry (CV) measurements, it is shown that the redox potentials (E_1/2) of the 1,2,4,5-tetrazines (s-tetrazines) have a strong correlation with the Hammett constant of the substituents. In Li-ion coin cells, the discharge voltages of the s-tetrazine electrodes are successfully tuned depending on the electron-donating/withdrawing capabilities of the substituents. Furthermore, it is found that the heterogeneous electron transfer rate (k₀) of the s-tetrazine molecules and Li-ion diffusivity (D_Li) in the s-tetrazine electrodes are much faster than conventional electrode active materials.

Molecular Simulations of the Microstructure Evolution of Solid Electrolyte Interphase during Cyclic Charging/Discharging

Lithium (Li) metal is regarded as one of the most promising anode materials for use in next-generation high-energy-density rechargeable batteries because of its high volumetric and gravimetric specific capacity, as well as low reduction potential. Unfortunately, uncontrolled dendritic Li growth during cyclic charging/discharging leads to low columbic efficiency and critical safety issues. Hence, comprehensive understanding of the formation mechanism for Li-dendrite growth, particularly at the onset of dendrite formation, is essential for developing Li-metal anode batteries. In this study, reactive molecular dynamics (MD) simulations in combination with the electrochemical dynamics with implicit degrees of freedom (EChemDID) method were performed to investigate the formation and evolution of solid electrolyte interphase (SEI) films for a Li-metal anode under cyclic charging/discharging processes in two distinct dimensions, namely, electrolyte compositions and initial surface morphologies. Our simulations indicated that regardless of the electrolyte compositions and initial anode morphologies, inhomogeneous Li reduction, namely, the formation of Li-reduction "hotspots" during cyclic charging cycles, took place and could serve as the seed for subsequent dendrite growth. The fluorine-containing electrolyte additives could notably mitigate the Li-anode roughening processes by forming dense-SEI-layer products or suppressing electrolyte decomposition. A series of Li-ion-drifting simulations suggest that Li ions navigate through the SEI layer via pathways composed of low-density atoms and become reduced at these reduction hotspots, promoting inhomogeneous deposition and subsequent dendrite growth. The present study reveals atomistic details of the early stage of dendrite growth during cyclic loadings under different electrolyte compositions and anode morphologies, thereby providing insights for designing artificial SEI layers or electrolytes for long-life, high-capacity Li-ion batteries.

Review on organosulfur materials for rechargeable lithium batteries

Organic electrode materials have been considered as promising candidates for the next generation rechargeable battery systems due to their high theoretical capacity, versatility, and environmentally friendly nature. Among them, organosulfur compounds have been receiving more attention in conjunction with the development of lithium-sulfur batteries. Usually, organosulfide electrodes can deliver a relatively high theoretical capacity based on reversible breakage and formation of disulfide (S-S) bonds. In this review, we provide an overview of organosulfur materials for rechargeable lithium batteries, including their molecular structural design, structure related electrochemical performance study and electrochemical performance optimization. In addition, recent progress of advanced characterization techniques for investigation of the structure and lithium storage mechanism of organosulfur electrodes are elaborated. To further understand the perspective application, the additive effect of organosulfur compounds for lithium metal anodes, sulfur cathodes and high voltage inorganic cathode materials are reviewed with typical examples. Finally, some remaining challenges and perspectives of the organosulfur compounds as lithium battery components are also discussed. This review is intended to serve as general guidance for researchers to facilitate the development of organosulfur compounds.

Prediction of two-dimensional CP3 as a promising electrode material with a record-high capacity for Na ions

Borophene with a maximum Li/Na capacity of 1984 mA h g^-1 (nanoscale 2016, 8, 15 340-15 347) has shown the highest capacity among two-dimensional (2-D) anode materials identified so far. Herein, we report the record break for Na-ion using a newly proposed 2-D material, namely, CP₃. We fully investigated Li- and Na-ion adsorption and diffusion processes on a CP₃ monolayer. We found that the material can enable stable Li/Na adsorption considering charge accumulation on CP₃ surfaces. The ion diffusion barriers for Li and Na were identified to be 98 meV and 356 meV, respectively. These values were comparable or smaller than those of the typical high-capacity electrode materials such as borophene. Most remarkably, the maximum Na capacity in CP₃ monolayer can reach up to 2298.9 mA h g^-1, which breaks the value recorded using borophene (1984 mA h g^-1). Our work highly promises that the 2-D CP₃ material could serve as an outstanding electrode material for Na-ion batteries with an extremely high storage capacity.

Enhanced ion diffusion induced by structural transition of Li-modified borophosphene

Density functional theory (DFT) calculations have been carried out to investigate the performance of borophosphene in lithium-ion batteries. Our study has revealed the following: (1) the Dirac cone in the electronic structure demonstrates the metallic nature of borophosphene, implying the enhanced electronic conductivity of the anode electrodes; (2) borophosphene shows high adsorption of Li ions with binding energies in the range of -0.6 to -1.1 eV; (3) the theoretical storage capacity is significantly high, up to 1282.7 mA h g-1, and more interestingly, a structural transition is observed in the host borophosphene at a high density of Li ions; (4) at low concentrations, graphene-like borophosphene shows isotropic diffusion of Li atoms with a barrier around 0.5 eV, while at high density, the phosphorene-like borophosphene exhibits a reduced barrier in the range of 0.12-0.14 eV along the zigzag direction, suggesting strong promotion of Li-ion transportation; (5) meanwhile, owing to the structural transition, phosphorene-like borophosphene exhibits highly anisotropic migration of Li ions along the zigzag and armchair directions. These new findings present the great advantages of borophosphene as an anode material in lithium-ion batteries.

Ti2P monolayer as a high performance 2-D electrode material for ion batteries

Electrical conductivity, storage capacity and ion diffusion ability are three crucial parameters for battery electrode materials. However, rare existing two-dimensional (2-D) electrode materials can achieve high performances in all these parameters. Here, we report that a 2-D transition-metal phosphide, the Ti₂P monolayer, is a promising superior electrode material which realizes high performances in all the parameters mentioned above. The Ti₂P monolayer has a stable honeycomb crystal structure. It has a metallic electronic structure with Li/Na adsorption, which ensures good electrical conductivity during the battery operation. We find that Li/Na can chemically bond to the Ti₂P substrate, with specific charge exchanges. Our results show the Li/Na capacity in the Ti₂P monolayer is about 846 mA h g^-1, which is much higher than that of the graphite anode. Remarkably, the Li/Na diffusion barrier on the Ti₂P monolayer is only 12-16 meV, which is lower than that in all 2-D anode materials proposed till now. Our work highly promises that theTi₂P monolayer can serve as a superior anode material for Li-ion/Na-ion batteries by providing good electrical conductivity, high storage capacity and ultrafast ion diffusion.

Transition-Metal Phosphorus Trisulfides and its Vacancy Defects: Emergence of a New Class of Anode Material for Li-Ion Batteries

In the search of suitable anode candidates with high specific capacity, favorable potential, and structural stability for lithium-ion batteries (LIBs), transition-metal phosphorus trisulfides (TMPS3 ) can be considered as one of the most promising alternatives to commercial graphite. Here, it was demonstrated that the limitations of commercial anode materials (i.e., low specific capacity, large volume change, and high lithium diffusion barrier as well as nucleation) can be circumvented by using TMPS3 monolayer surfaces. The study revealed that lithium binds strongly to TMPS3 monolayers (-2.31 eV) without any distortion of the surface, with Li@TMPS3 exhibiting enhanced stability compared with other 2D analogues (graphene, phosphorene, MXenes, transition-metal sulfides and phosphides). The binding energy of lithium was overwhelmingly enhanced with vacancy defects. The vacancy-mediated TMPS3 surfaces showed further amplification of Li binding energy from -2.03 to -2.32 eV and theoretical specific capacity of 441.65 to 484.34 mAh g-1 for MnPS3 surface. Most importantly, minimal change in volume (less than 2 %) after lithiation makes TMPS3 monolayers a very effective candidate for LIBs. Additionally, the ultralow lithium diffusion barrier (0.08 eV) compared with other existing commercial anode material proves the superiority of TMPS3 .

Mellitic Triimides Showing Three One-Electron Redox Reactions with Increased Redox Potential as New Electrode Materials for Li-Ion Batteries

The mellitic triimide (MTI) bearing three imide groups on a benzene core with C3 symmetry is proposed as a new building block for organic electrode materials in lithium-ion batteries. MTI was anticipated to deliver a higher theoretical specific capacity of up to 282 mAh g^-1 with increased reduction potentials compared with the well-known pyromellitic diimide building block bearing two imide groups because the additional imide group can accept one more electron and provide an electron-withdrawing effect. A model compound, ethyl-substituted mellitic triimide (ETTI), shows three well distinguished and reversible one-electron redox reactions at -0.97, -1.62, and -2.34 V versus Ag/Ag⁺ in 0.1 m tetrabutylammonium hexafluorophosphate electrolyte, but the redox potentials were increased in 2 m lithium bis(trifluoromethanesulfonyl)imide electrolyte: -0.60 V, -0.86 V, and -1.42 V vs. Ag/Ag⁺ . The DFT calculations revealed that the unique C3 symmetric structural design leads to the higher reduction potential of MTI in the Li-based electrolyte by formation of a stable 7-membered ring with a Li ion and the two carbonyl oxygen atoms from the adjacent imide groups. In a Li-ion coin cell, the ETTI electrode delivered a specific capacity of 176 mAh g^-1 , corresponding to 81 % of capacity utilization, with three clear voltage plateaus. The higher average discharge voltage (2.41 V vs. Li/Li⁺ ) of ETTI allows it to deliver one of the highest specific energies (421 Wh kg^-1 ) among reported diimide-based electrode materials. Finally, its redox mechanism was investigated by ex situ FTIR measurements and DFT calculations.

Ex-Ante Prediction of Disruptive Innovation: The Case of Battery Technologies

Battery technologies represent a highly relevant field that is undergoing conversions in the context of, for instance, battery electric vehicles or stationary power storage for renewable energies. Currently, lithium-ion batteries represent the predominant technology that has, however, a considerable environmental impact that could hinder the emergence of sustainable energy systems. Driven by these conversions, several authors claim that potentially disruptive technologies could occur. The concept of disruptive innovation has been highly regarded in research and practice, but has only been successfully regarded from an ex-post perspective. However, without the possibility to establish ex-ante predictions of disruptive innovation, several authors disregard the concept of having significant relevance for practice. In response to this research gap, the present paper attempts to establish an ex-ante prediction of potential disruptive innovation. The method is based on the disruption hazard model by Sood and Tellis, testing seven hypotheses regarding a potential disruption hazard of redox-flow batteries towards lithium-ion batteries. The paper finds that redox-flow batteries could represent a disruptive technology, but this evaluation is limited to an expert evaluation. The authors discuss this finding, as the technical characteristics of redox-flow batteries support its role as a potential disruptive innovation, concluding with implications, limitations as well as suggestions for future research.

A Conjugated Copolymer of N-Phenyl-p-phenylenediamine and Pyrene as Promising Cathode for Rechargeable Lithium-Ion Batteries

A novel conjugated copolymer has been synthesized and employed as an organic cathode material in rechargeable lithium-ion batteries (LIBs). Due to the synergistic effects from conducting aniline and pyrene units, the resultant batteries based on the as-obtained copolymer can deliver a promising reversible specific capacity of 113 mAh g^-1 with a high voltage output of 3.2 V and a remarkable 75.2 % capacity retention after 180 cycles. Moreover, an excellent rate performance is also achieved with a fast recovery of the capacity at different current densities.

Recent Progress in Multivalent Metal (Mg, Zn, Ca, and Al) and Metal-Ion Rechargeable Batteries with Organic Materials as Promising Electrodes

The emerging demand for electronic and transportation technologies has driven the development of rechargeable batteries with enhanced capacity storage. Especially, multivalent metal (Mg, Zn, Ca, and Al) and metal-ion batteries have recently attracted considerable interests as promising substitutes for future large-scale energy storage devices, due to their natural abundance and multielectron redox capability. These metals are compatible with nonflammable aqueous electrolytes and are less reactive when exposed in ambient atmosphere as compared with Li metals, hence enabling potential safer battery systems. Luckily, green and sustainable organic compounds could be designed and tailored as universal host materials to accommodate multivalent metal ions. Considering these advantages, effective approaches toward achieving organic multivalent metal and metal-ion rechargeable batteries are highlighted in this Review. Moreover, organic structures, cell configurations, and key relevant electrochemical parameters are presented. Hopefully, this Review will provide a fundamental guidance for future development of organic-based multivalent metal and metal-ion rechargeable batteries.

s-Tetrazines as a New Electrode-Active Material for Secondary Batteries

Because of the limitations of conventional metal-oxide-based electrodes, studies on organic redox-active materials as alternative electrodes for secondary batteries are emerging. However, reported organic electrode materials are still limited to a few kinds of organic redox groups. Therefore, the development of new redox-active groups for high-performance electrode materials is indispensable. Here, we evaluate s-tetrazine derivatives as a new electrode material in Li-ion batteries and study their charge/discharge mechanisms by ex situ XPS measurements. The porous carbon CMK-3 was introduced to encapsulate the s-tetrazines, which allowed 100 % utilization of the theoretical capacity and stable cycle performance of the s-tetrazines by preventing dissolution of the molecules into the electrolytes. This new class of redox-active group can pave the way for the next-generation of energy storage systems.

Synthesis of a 2D nitrogen-rich π-conjugated microporous polymer for high performance lithium-ion batteries

Here we synthesized a 2D π-conjugated microporous polymer NGA-CMP. Heated sample NGA-CMP400 is used for the first time as an anode for LIBs and shows high capacity lithium-ion storage with excellent cycle performance at high current density.

Two-Dimensional GaN: An Excellent Electrode Material Providing Fast Ion Diffusion and High Storage Capacity for Li-Ion and Na-Ion Batteries

Identifying applicable anode materials is a significant task for Li- and Na-ion battery (LIB and NIB) technologies. We propose the GaN monolayer (2D GaN) can be a good anode candidate. The GaN monolayer manifests stable Li/Na adsorption and inherently low theoretical voltages. Most excitingly, both high storage capacity and extremely fast Li/Na diffusion can be simultaneously realized in the GaN monolayer. For Li, the storage capacity and diffusion barrier is 938 mA h g^-1 and 79 meV, respectively. And, the values for Na are 625 mA h g^-1 and 22 meV. Compared with known two-dimensional (2D) anode materials with similar scale of ion diffusion barriers, the GaN monolayer almost possesses the highest Li/Na storage capacity discovered to date. Our work suggests that the 2D GaN is a prospective anode material offering fast ion diffusion and high storage capacity.

Superlithiated Polydopamine Derivative for High-Capacity and High-Rate Anode for Lithium-Ion Batteries

Organic electrode materials, with low-cost synthesis and environmental friendliness, have gained significant research interest in lithium-ion batteries (LIBs). Polydopamine (PDA), as a bioderived organic electrode material, exhibits a low capacity of ∼100 mAh g^-1, greatly limiting the practical application in LIBs. In this work, we find that a simple heat treatment at 300 °C can endow PDA-derived material (PDA300) with superior electrochemical performance. The obtained PDA300 electrode exhibits an ultrahigh capacity of 977 mAh g^-1 at 50 mA g^-1. Further combining the PDA300 with highly conductive Ti₃C₂T _x MXene, the obtained PDA300/Ti₃C₂T _x composite is demonstrated by high capacity (1190 mAh g^-1, 50 mA g^-1), excellent rate capability (remaining 552 mAh g^-1 at 5 A g^-1), and good cycling stability (82% retaining after 1000 cycles). The outstanding lithium storage performance is highly associated with the superlithiation process of the unsaturated carbon-carbon bonds in the PDA derivative and the introduction of the highly conductive Ti₃C₂T _x substrate with a unique two-dimensional nanostructure. This work will provide new opportunities for the expansion of high-performance organic anodes for LIBs.

Amino group enhanced phenazine derivatives as electrode materials for lithium storage

The development of organic molecule-based batteries is hampered by stability issues caused by the dissolution of the active organic materials in electrolytes. Herein, phenazine (PNZ) and 2,3-diaminophenazine (DAP) are investigated as organic electrode materials. The presence of amino functional groups in DAP dramatically enhances its electrochemical performances due to suppressed dissolution in the electrolyte.

Hexagonal Ti2B2 monolayer: a promising anode material offering high rate capability for Li-ion and Na-ion batteries

Combining the first-principles density functional method and crystal structure prediction techniques, we report a series of hexagonal two-dimensional transition metal borides including Sc₂B₂, Ti₂B₂, V₂B₂, Cr₂B₂, Y₂B₂, Zr₂B₂, and Mo₂B₂.

Lithium adsorption and migration in group IV–VI compounds and GeS/graphene heterostructures: a comparative study

The migration energy barriers of lithium migration on monolayer GeS along armchair and zigzag directions, and the distortion degree comparison for bulk GeS and GeS/graphene heterostructures during lithiation.

Molecular Engineering with Organic Carbonyl Electrode Materials for Advanced Stationary and Redox Flow Rechargeable Batteries

Organic carbonyl electrode materials that have the advantages of high capacity, low cost and being environmentally friendly, are regarded as powerful candidates for next-generation stationary and redox flow rechargeable batteries (RFBs). However, low carbonyl utilization, poor electronic conductivity and undesired dissolution in electrolyte are urgent issues to be solved. Here, we summarize a molecular engineering approach for tuning the capacity, working potential, concentration of active species, kinetics, and stability of stationary and redox flow batteries, which well resolves the problems of organic carbonyl electrode materials. As an example, in stationary batteries, 9,10-anthraquinone (AQ) with two carbonyls delivers a capacity of 257 mAh g^-1 (2.27 V vs Li⁺ /Li), while increasing the number of carbonyls to four with the formation of 5,7,12,14-pentacenetetrone results in a higher capacity of 317 mAh g^-1 (2.60 V vs Li⁺ /Li). In RFBs, AQ, which is less soluble in aqueous electrolyte, reaches 1 M by grafting -SO₃ H with the formation of 9,10-anthraquinone-2,7-disulphonic acid, resulting in a power density exceeding 0.6 W cm^-2 with long cycling life. Therefore, through regulating substituent groups, conjugated structures, Coulomb interactions, and the molecular weight, the electrochemical performance of carbonyl electrode materials can be rationally optimized. This review offers fundamental principles and insight into designing advanced carbonyl materials for the electrodes of next-generation rechargeable batteries.

Amorphous MoS3 as the sulfur-equivalent cathode material for room-temperature Li-S and Na-S batteries

Many problems associated with Li-S and Na-S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS₃ as such a material for room-temperature Li-S and Na-S batteries. In Li-S batteries, MoS₃ exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS₃ can also be used as the cathode material of even more challenging Na-S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS₃ It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.

Organic Thiocarboxylate Electrodes for a Room-Temperature Sodium-Ion Battery Delivering an Ultrahigh Capacity

Organic room-temperature sodium-ion battery electrodes with carboxylate and carbonyl groups have been widely studied. Herein, for the first time, we report a family of sodium-ion battery electrodes obtained by replacing stepwise the oxygen atoms with sulfur atoms in the carboxylate groups of sodium terephthalate which improves electron delocalization, electrical conductivity and sodium uptake capacity. The versatile strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes with the same carbon scaffold. By introducing two sulfur atoms to a single carboxylate scaffold, the molecular solid reaches a reversible capacity of 466 mAh g^-1 at a current density of 50 mA g^-1 . When four sulfur atoms are introduced, the capacity increases to 567 mAh g^-1 at a current density of 50 mA g^-1 , which is the highest capacity value reported for organic sodium-ion battery anodes until now.