Functionalized carbon dots for advanced batteries

Ordered carbonaceous frameworks (OCFs) are a new class of carbon materials with a three-dimensional ordered structure synthesized by simple carbonization of metalloporphyrin crystals with polymerizable moieties. Carbonization via solid-state polymerization results in the formation of graphene-based ordered frameworks in which regularly aligned single-atomic metals are embedded. These unique structural features afford molecular-level designability like organic-based frameworks together with high electrical conductivity, thermal/chemical stability, and mechanical flexibility, towards a variety of applications including electrocatalysis and force-driven phase transition. This feature article summarizes the synthetic strategies and characteristics of OCFs in comparison with conventional organic-based frameworks and porous carbons, to discuss the potential applications and further development of the OCF family.

With the increasing demand for sustainable energy and concerns about the scarcity of lithium resources, sodium and potassium ion batteries have emerged as promising alternative energy storage technologies. MXene, as a novel two-dimensional material, possesses exceptional electrical conductivity, high surface area, and tunable structural features that make it an ideal candidate for high-performance electrode materials. However, its limited theoretical capacity hinders its widespread application. To overcome this limitation, MXene has been combined with other materials through synergistic effects between different components to enhance the overall electrochemical performance and expand its application in sodium/potassium ion batteries. Recently, substantial advancements have been realized in the exploration of MXene-based composites as energy storage materials, encompassing their synthesis, design, and the comprehension of charge storage mechanisms. This paper aims to propose a comprehensive summary of the latest developments in MXene-based composites as electrode materials for sodium ion batteries and potassium ion batteries, with a particular emphasis on the enhanced physicochemical properties resulting from composite formation. Moreover, the challenges faced by MXene materials in sodium ion batteries and potassium ion batteries are thoroughly discussed, and future research directions to further advance this field are proposed.

The imperative for sustainable energy has driven the demand for efficient energy storage systems that can harness renewable resources and store surplus energy for off-peak usage. Among the numerous advancements in energy storage technology, polymeric nanofibers have emerged as promising nanomaterials, offering high specific surface areas that facilitate increased charge storage and enhanced energy density, thereby improving electrochemical performance. This review delves into the pivotal role of nanofibers in determining the optimal functionality of energy storage systems. Electrospinning emerged as a facile and cost-effective method for generating nanofibers with customizable nanostructures, making it attractive for energy storage applications. Our comprehensive review article examines the latest developments in electrospun nanofibers for electrochemical storage devices, highlighting their use as separators and electrode materials. We provide an in-depth analysis of their application in various battery technologies, including supercapacitors, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, lithium–sulfur batteries, and lithium–oxygen batteries, with a focus on their electrochemical performance. Furthermore, we summarize the diverse fabrication techniques, optimization of key influencing factors, and environmental implications of nanofiber production and their properties. This review aims to offer an inclusive understanding of electrospinning’s role in advancing electrochemical energy storage, providing insights into the factors that drive the performance of these critical materials.

Designing and developing advanced electrode materials for high-performance rechargeable batteries have been subjected to extensive studies. Very recently, two-dimensional (2D) nanomaterials have become promising candidates for batteries due to their unique physicochemical properties. In particular, MXenes and phosphorene that exhibit tailored electrical conductivity and ion storage capability have attracted increasing atentions. In this review, we present a comprehensive summary of recent advances of 2D MXenes and phosphorene as electrode materials for high-performance batteries. Their physicochemical properties that include structural configurations and electronic properties of MXenes, and direct bandgap and anisotropic properties of phosphorene are firstly discussed. Then, synthesis methods of the two materials are introduced. Following this, their applications as electrode materials in batteries including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), potassium-ion batteries (PIBs), lithium-sulfur (Li-S) batteries and metal-air batteries are summarized and discussed in details. An emphasis is placed on analyzing performance enhancement mechanisms to to elucidate fundamental understanding. Finally, challenges and opportunities ahead for MXenes and phosphorene as electrode materials for batteries are featured.

MXenes: An exotic material for hybrid supercapacitors and rechargeable batteries

Three-dimensional (3D) graphene-assembled monoliths (GAs), especially ones prepared by self-assembly in the liquid phase, represent promising forms to realize the practical applications of graphene due to their high surface utilization and operability. However, the understanding of the assembly process and structure control of 3D GAs, as a new class of carbon materials, is quite inadequate. In this Perspective, we give a demonstration of the assembly process and discuss the key factors involved in the structure control of 3D GAs to pave the way for their future applications. It is shown that the assembly process starts with the phase separation, which is responsible for the formation of the 3D networked structure and liquid phase as the spacers avoid the parallel overlap of graphene layers and help form an interlinked pore system. Well-tailored graphene sheets and selected assembly media must be a precondition for a well-controlled assembly process and microstructure of a 3D GA. The potential applications in energy storage featuring high rate and high volumetric energy density demonstrate advantages of 3D GAs in real applications.

Synthesis of functional nanocomposites based on carbon black is a promising approach to the development of advanced materials for various purposes. Carbon black and pyrolytic carbon were used to create a new class of carbon materials: Technosorb, Sibunit, Carbostil, and medicinal carbons VNIITU 1 and 2, which show high performance and are successfully applied in catalysis, sorption, medicine and metallurgy. The unique technology for the production of such materials, which has no analogs in the world, has been developed. The main principles for the design of nanocomposites make it possible to develop special highly porous carbon materials with the properties optimized for a new generation of electrochemical systems intended for electric energy generation and storage – from batteries and fuel cells to supercapacitors and metal-ion accumulators.

Harnessing the potential of MOF-derived metal oxide composites to optimize energy efficiency in batteries and supercapacitors

Lithium-sulfur (Li-S) batteries afford great promise on achieving practical high energy density beyond lithium-ion batteries. Lean-electrolyte conditions constitute the prerequisite for achieving high-energy-density Li-S batteries but inevitably deteriorates battery performances, especially the sulfur cathode kinetics. Herein, the polarizations of the sulfur cathode are systematically decoupled to identify the key kinetic limiting factor in lean-electrolyte Li-S batteries. Concretely, an electrochemical impedance spectroscopy combined galvanostatic intermittent titration technique method is developed to decouple the cathodic polarizations into activation, concentration, and ohmic parts. Therein, activation polarization during lithium sulfide nucleation emerges as the dominant polarization as the electrolyte-to-sulfur ratio (E/S ratio) decreases, and the sluggish interfacial charge transfer kinetics is identified as the main reason for degraded cell performances under lean-electrolyte conditions. Accordingly, a lithium bis(fluorosulfonyl)imide electrolyte is proposed to decrease activation polarization, and Li-S batteries adopting this electrolyte provide a discharge capacity of 985 mAh g-1 under a low E/S ratio of 4 μL mg-1 at 0.2 C. This work identifies the key kinetic limiting factor of lean-electrolyte Li-S batteries and provides guidance on designing rational promotion strategies to achieve advanced Li-S batteries.

SnO2 nanosheets grow on sunflower shell carbon sphere used as anode material for high performance lithium-ion and potassium-ion batteries

To exploit LIBs to their maximum applications, innovative electrode materials should be developed and existing materials should be improved. As negative electrode materials are needed in excess in comparison with positive electrode materials (in terms of specific capacity) in a lithium-ion battery, it is important to reduce their amounts so as to reduce the cell size and production cost[1]. Moreover, innovative negative electrode material classes delivering high capacity and offering fast Li diffusion kinetics should be developed. Parallel to this, research in alternative low cost energy storage systems became more intensive. Due to the high abundance and cost effectiveness of the electrode materials used, Na-ion batteries have become one of the best alternative energy storage systems to LIBs. Many of the attractive Li-insertion electrode materials are also tested for Na-insertion as a part of developing this system further. As different from the wide variety of positive electrode materials, there are only few choices for negative electrode materials for Na-ion batteries[2]. Na does not insert into graphite. Binary alloys of Na with Sn, Pb or other metals and conversion metal oxides are expected to have very high gravimetric capacity[3]. However, the enormous volume changes are supposed to bring out poor cycling behavior of these materials. SnO2 is a promising negative electrode material for Li-ion batteries due to its high theoretical specific capacity of 1491 mAh g-1 [4]. The first step in the Li insertion of SnO2 is a conversion reaction involving 4 Li, where metallic Sn particles are formed in a matrix of Li2O. In the second step, metallic Sn alloys with Li and produce Li4.4Sn. Hence in total 8.4 Li ions can be inserted per formula unit of SnO2 [4]. Nevertheless, this material suffers from extreme volume changes which can lead to a drop in the electric contact and further to severe capacity fading during cycling. This can be overcome by preparing nanocrystalline materials, composite materials with carbon derivatives etc. In the present work, SnO2 nanoparticles are synthesized via a hydrothermal process. The obtained SnO2 material has a particle size of ~50 nm. The material was investigated as negative electrode candidate for both Li- and Na-ion batteries in corresponding half cells. The respective electrochemical mechanism was investigated by in situ and quasi in situ X-ray absorption spectroscopy. It was observed that at the end of discharge, SnO2 was converted to metallic Sn nanoparticles in a Li-ion cell (see Figure 1). Meanwhile, no complete reduction of the SnO2 was observed in the Na-ion cell at the end of discharge. The details of the electrochemical mechanism of SnO2 as negative electrode material for Li-ion and Na-ion batteries will be discussed. Acknowledgement: Financial support from DFG within the Research Priority Program SPP 1473, “Materials with new design for improved Li ion batteries-WeNDeLIB” under grant no EH183/16-2 is gratefully acknowledged. This work has benefitted from beam time allocation by the core-level absorption and emission spectroscopies (CLAESS) beamline, ALBA, Barcelona.

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.

Lithium-sulfur (Li-S) batteries are regarded as one of the most promising next-generation energy storage technologies due to their high theoretical specific capacity, material abundance, and low production costs. Despite these advantages, the commercialization of Li-S batteries remains limited, primarily due to significant technical challenges,1-3 including the dissolution and shuttling of lithium polysulfides (PS), a major cause of fast capacity degradation over cycling in Li-S batteries. In our recent work,4 we introduced a novel sulfur cathode design comprising a thin film of nanolayer-polymer-coated carbons (NPC) deposited on sulfur electrodes (NPC-S). This advanced architecture enabled Li-S battery cells to achieve a high specific capacity of ~1,600 mAh/g, approaching sulfur's theoretical specific capacity, without introducing appreciable dead weight or volume to the battery.In this talk, we will present our continued efforts to further develop the advanced Li-S battery technology with the novel strategy of combining the NPC-S approach with a cycle-stabilizing and safety-enhancing approach in the advanced Li-S batteries. This synergistic strategy resulted in not only the near-theoretical specific capacity of sulfur (Figure 1a), but also a significantly improved long-term cycle stability, ~90% capacity retention after cycling at 1C rate for 500 charge-discharge cycles (Figure 1b). We will present various analytical characterizations and theoretical calculations to elucidate the reaction mechanisms of the outstanding performance of the advanced Li-S battery technology. Acknowledgment This work was supported by the Linda and Larry Pearson Endowed Chair at the Leslie A. Rose Department of Mechanical Engineering, South Dakota School of Mines & Technology, and the South Dakota Governor Research Center for Electrochemical Energy Storage. References Wang, S.; Wang, Z.; Chen, F.; Peng, B.; Xu, J.; Li, J.; Lv, Y.; Kang, Q.; Xia, A.; Ma, L. "Electrocatalysts in lithium-sulfur batteries". Nano Research 2023, 1-30.Zhao, F. L.; Xue, J. H.; Shao, W.; Yu, H.; Huang, W.; Xiao, J. "Toward high-sulfur-content, high-performance lithium-sulfur batteries: Review of materials and technologies". J Energy Chem 2023, 80, 625-657. DOI: 10.1016/j.jechem.2023.02.009.Hu, X.; Huang, T.; Zhang, G.; Lin, S.; Chen, R.; Chung, L.-H.; He, J. "Metal-organic framework-based catalysts for lithium-sulfur batteries.". Coordination Chemistry Reviews 2023, 475, 214879.Hasan, M. W.; Huynh, K.; Lama, B.; Razzaq, A. A.; Smdani, M. G.; Akter, F. N.; Maddipudi, B.; Shende, R.; Paudel, T. R.; Xing, W. "A Highly Effective Polysulfide-Trapping Approach for the Development of High Energy Density, Scalable Lithium-Sulfur Batteries". J Electrochem Soc 2024. DOI: 10.1149/1945-7111/ad3ebf. Figure 1

Electrolytic alloy‐type anodes for metal‐ion batteries

Potassium-ion batteries (KIBs) have attracted wide interest for energy storage because of the abundance of the electrode materials involved; however, their electrochemical performances are far behind what can be achieved from lithium-ion batteries (LIBs) or sodium-ion batteries (SIBs). Herein, key promising electrode and electrolyte materials for potassium-ion batteries are identified, the coupled electrochemical reactions in the cell are investigated, and the compatibility between different materials is demonstrated to play the most important role. K2 Mn[Fe(CN)6 ] cathode can deliver a high capacity of ≈125 mAh g-1 and exceptional cycling stability over 61000 cycles (≈9 months) if the side reactions from the anode can be prevented. Graphite is a good anode material but is subjected to degradation in traditional carbonate electrolytes. New concentrated electrolytes are developed and evaluated. A stable KIB system is demonstrated by coupling a stable K2 Mn[Fe(CN)6 ] cathode, a prepotassiated graphite anode with a concentrated electrolyte to achieve a high energy density of ≈260Wh kg-1 (based on the active mass of cathode and anode) and good cycling of over 1000 cycles.