Theoretical insights into the electrochemical potential of Cu3Si as an electrode material for lithium-ion batteries

The growing electric vehicle requirements have attracted great interest in development of lithium ion batteries (LIBs) with large gravimetric and volumetric capacities, long cycle lifespan. To meet these applications, high quality electrode materials are needed. However, conventional bulk electrode materials cannot fully reach the increasing demands due to their inherent limits in performance. In recent years, nanostructured electrode materials with higher rate capability have been acknowledged by low lithium-ion diffusion distance and high electrode/electrolyte area. However, electrode made from nanostructured electrode materials meets these challenges. (1) Nanoparticles tend to self-aggregate and the side reaction with the electrolyte due to high specific surface area, which lead to low initial coulombic efficiency and poor cycling life. (2) Nanoparticles have a huge volume changes during Li+ insertion/ extraction that result in fracture of nanostructured particle, delaminating of the conductive coating and low capacity with cycle increasing. (3) Nanostructured particles have low tap density which results in a low volumetric energy density.Therefore, the electrode materials with optimal structure should be developed to deal with above-mentioned problems. Micro-/nanostructures with controlled size and morphology have attracted considerable attention as high-performance anode materials for next-generation LIBs. This micro-/nanostructure should be a porous microstructure composed of primary nanocrystallines tightly compacted to form 3D channels for ion diffusion. Moreover, this structure can exploit many advantages of nanostructure for lithium ion batteries due to the reduction of side reactions with electrolyte, leading to high density and long cycling life with high safety. Some simple micro-/nano-structured metal oxides such as Mn-based oxides, Co-based oxides, Fe-based oxides and Sn-based oxides, have been recently reported for use in LIBs. Mn-based oxide electrodes (MnO, MnO2, Mn2O3, Mn3O4, ZnMn2O4, NiMn2O4 and CoMn2O4) are developed due to low operating voltages (1.3-1.5 V for lithium extraction) and high energy density. Among these Mn-based anodes, CoMn2O4 has been considered for substitution of the conventional graphite anode in LIBs. The shape and micro/nanostructure of CoMn2O4 material play an important role in the electrochemical performances. In this paper, uniform hierarchical porous CoMn2O4 microspheres and microflowers were realized by adjusting the urea concentration through a solvothermal process followed by a post-annealing treatment. In the low urea concentration, the microflower with diameter size of around 10 μm is composed of porous nanosheets with a thickness of about 20 nm. In the high urea concentration, a large amount of uniform CoMn2O4 microspheres is obtained with average diameter of about 8 μm. CoMn2O4 microsphere is highly porous and composed of numerous primary nanoparticles. As expected, the distribution of the O, Mn and Co elements is homogeneously distributed on the surface for CoMn2O4 microflower and microsphere. The actual molar ratios of Mn and Co for CoMn2O4 microflower and microspheres obtained from energy-dispersive X-ray (EDX) analysis are close to 2, which are consistent with the ratio of that in the precursor solution. The chemical compositional and crystalline structural changes of as-prepared samples were characterized using X-ray diffraction (XRD) and thermogravimetric analysis (TGA). These results show the precursor in the low urea concentration is a MnCo-complex structure (including CoMn-layered double hydroxide and CoMn-glycolates or alkoxide derivatives) in an alkaline environment under this solvothermal conditions. Meanwhile, in the high urea concentration, the precursor Co1/3Mn2/3CO3 sample is formed. The possible formation mechanism of as-prepared CoMn2O4 microsphere and microflower precursors is explained due to the presence of CO2 pressure into the reaction solution. When used as anode materials for lithium-ion batteries, the porous CoMn2O4 microflower and microspheres exhibited good long-life cycling performance at high rate density. At a current density of 100 mA g-1, the CoMn2O4 microflower and microspheres exhibit an initial capacity of 1200 and 1225 mA h g-1 and the capacity is maintained at 710 and 220 mAh g-1 after 50 cycles. Excellent rate capabilities (~813 mAh g-1 at 200 mA g-1 and ~612 mAh g-1 at 600 mA g-1) are observed for CoMn2O4 microspheres. Based on these results, the good electrochemical properties can result from the porous CoMn2O4 microspheres. On the one hand, the micro-/nano porous structured CoMn2O4 microspheres could significantly enhance the electrode integrity by buffering the volume changes with repeating Li+ insertion/ extraction, which is contributed to good cycling stability. On the other hand, the micro-/nano porous structured CoMn2O4 microspheres provide extra active position for Li+ storage and short Li+ ion diffusion length, contributing to the high specific capacity and better rate capability. The CoMn2O4 hierarchical porous microspheres, which have good electrochemical performance and ease of fabrication, hold the great promise as the anode materials for high-performance LIBs. Figure 1

Exploring the potential of Ti2BT2 (T = F, Cl, Br, I, O, S, Se and Te) monolayers as anode materials for lithium and sodium ion batteries

This study presents the facile synthesis of a high-performance anode material for lithium-ion batteries (LIBs), based on a composite of Mn2SnO4 and carbon derived from sugarcane bagasse (SCB), denoted as Mn2SnO4@C. The synthesis involved the impregnation followed by pyrolysis at 600oC for 2 hours, which not only utilized sugarcane bagasse as a cost-effective carbon source but also enabled in situ incorporation of Mn2SnO4 into a carbon matrix, using MnCl2/SnCl2 salt mixtures as the precursors. The composite demonstrates a unique structure associated with the transition of metal oxides during lithiation/delithiation cycles. Electrochemical evaluations reveal that the Mn2SnO4@C composite exhibits excellent lithium storage performanceincluding a high speciMic capacity and good cycling stability described by the high capacity of 1002 mAh g-1 at the Mirst discharge cycle and the discharge capacity of 541 mA g-1 obtained during Minal cycles of 80 cycles process. Additionally, coulombic efMiciency reached over 95% after the Mirst three cyclesand achieved 100% thereafter. These results draw an attention to the potential of the Mn2SnO4@C composite as a promising anode material for next-generation LIBs. Furthermore, this work highlights the feasibility of utilizing agricultural biomass as the eco-friendly and cost-effective product for advanced energy storage systems.

Biphenylene network (BPN), a newly discovered two-dimensional sp2-hybridized carbon allotrope composed of 4-6-8 carbon rings, shows great potential for energy storage applications. In this study, biphenylene concentric nanorings (BPNCRs), derived from hydrogen-terminated finite-sized BPN units, are explored as anode materials for lithium-ion batteries (LIBs) using density functional theory (DFT) based simulations. The lithium intercalation and adsorption on BPNCRs of varying sizes are investigated. BPNCR with an inner-outer ring diameter of 5-17 Å is found to exhibit an impressive specific capacity of 1509 mA h g-1 and an energy density of ∼4500 mW h g-1, with a low open-circuit voltage of 0.01 V (average voltage: 0.102 V). An increase in inter-ring spacing offers more lithium intercalation, which leads to further capacity enhancement and open-circuit voltage reduction. For example, BPCNR with an inner-outer ring diameter of 5-19 Å delivers a capacity of 1973 mA h g-1 with an OCV of 0.001 V. Notably, for every 1 Å increase in inter-ring spacing, the capacity increases by ∼500 mA h g-1. Finally, a three-dimensional assembly of lithiated BPNCR is modelled to evaluate its stability in the bulk form. Bulk-BPCNR is not only found to be stable but also provides experimental viability and promises the best features of both nano-particles and micro-particles at the same time. It is also noted that all intercalated lithium atoms are charged, thereby, ruling out lithium plating. These promising results suggest BPNCRs as high-performance anode materials for next-generation LIBs.

Nanostructured anode materials for high-performance lithium-ion batteries

As a class of redox active materials with some preferable properties, including rigid structure, insoluble characters, and large amounts of nitrogen atoms, covalent triazine frameworks (CTFs) have been frequently adopted as electrode materials in Lithium-ion batteries (LIBs). Herein, a triazine-based covalent organic framework employing 3,4-ethylenedioxythiophene (EDOT) as the bridging unit is synthesized by the presence of carbon powder through Stille coupling reaction. The carbon powder was added in an in-situ manner to overcome the low intrinsic conductivity of the polymer, which led to the formation of the polymer@C composite (PTT-O@C, PTT-O is a type of CTFs). The composite material is then employed in LIBs as anode material. The designed polymer shows a narrow band gap of 1.84 eV, proving the effectiveness of the nitrogen-enriched triazine unit in reducing the band gap of the resultant polymers. The CV results showed that the redox potential of the composite (vs. Li/Li+) is around 1.0 V, which makes it suitable to be used as the anode material in lithium-ion batteries. The composite material could exhibit the stable specific capacity of 645 mAh/g at 100 mA/g and 435 mAh/g at 500 mA/g, respectively, much higher than the pure carbon materials, indicating the good reversibility of the material. This work provides some additional information on electrochemical performance of the triazine and EDOT based CTFs, which is helpful for developing a deep understanding of the structure–performance correlations of the CTFs as anode materials.

Sb2O5/Co-containing carbon polyhedra as anode material for high-performance lithium-ion batteries

Waste-glass-derived silicon/CNTs composite with strong Si-C covalent bonding for advanced anode materials in lithium-ion batteries

Silicon-based electrodes are widely recognized as promising anodes for high-energy-density lithium-ion batteries (LIBs). Silicon is a representative anode material for next-generation LIBs due to its advantages of being an abundant resource and having a high theoretical capacity and a low electrochemical reduction potential. However, its huge volume change during the charge–discharge process and low electrical conductivity can be critical problems in its utilization as a practical anode material. In this study, we solved the problem of the large volume expansion of silicon anodes by using the carbon coating method with a low-cost phenolic resin that can be used to obtain high-performance LIBs. The surrounding carbon layers on the silicon surface were well made from a phenolic resin via a solvent-assisted wet coating process followed by carbonization. Consequently, the electrochemical performance of the carbon-coated silicon anode achieved a high specific capacity (3092 mA h g−1) and excellent capacity retention (~100% capacity retention after 50 cycles and even 64% capacity retention after 100 cycles at 0.05 C). This work provides a simple but effective strategy for the improvement of silicon-based anodes for high-performance LIBs.

Hollow silica-embedded dehydrogenated polyacrylonitrile fibers as anode for the next-generation lithium-ion batteries

Nanosheets of earth-abundant jarosite were fabricated via a facile template-engaged redox coprecipitation strategy at room temperature and employed as novel anode materials for lithium-ion batteries (LIBs) for the first time. These 2D materials exhibit high capacities, excellent rate capability, and prolonged cycling performance. As for KFe3(SO4)2(OH)6 jarosite nanosheets (KNSs), the reversible capacities of above 1300 mAh g(-1) at 100 mA g(-1) and 620 mAh g(-1) after 4000 cycles at a very high current density of 10 A g(-1) were achieved, respectively. Moreover, the resulting 2D nanomaterials retain good structural integrity upon cycling. These results reveal great potential of jarosite nanosheets as low-cost and high-performance anode materials for next-generation LIBs.

Amorphous structure and sulfur doping synergistically inducing defect-rich short carbon nanotubes as a superior anode material in lithium-ion batteries

Graphene (Gr) and graphene quantum dots (GQDs) have emerged as promising anode materials for lithium-ion batteries (LIBs) due to their high conductivity and tunable surface chemistry. In this study, we systematically investigate the impact of lithium (Li) adsorption on the structural, electronic, and electrochemical properties of Gr and GQDs using density functional theory (DFT) calculations. Adsorption energy analysis reveals that Li preferentially binds to functionalized GQDs, with Li–GQD–O exhibiting the strongest interaction (−5.026 eV), indicating enhanced Li storage capability. Electronic structure analysis shows a significant reduction in the HOMO–LUMO gap upon Li adsorption, improving charge transport properties crucial for battery performance. Functionalized GQDs, particularly those with oxygen-containing groups, further enhance electronic conductivity and charge transfer characteristics. The computed lithiation voltages confirm that functionalization modulates the electrochemical potential, with Li–GQD–O and Li–GQD–OOH exhibiting favorable energy characteristics for stable Li storage. Additionally, Li diffusion barriers obtained via the nudged elastic band (NEB) method reveal ultrafast Li-ion mobility on graphene (0.02 eV) and slightly higher, yet controlled, diffusion on GQDs (0.05 eV), suggesting tunable charge transport properties. These results provide valuable insights into the role of functionalization in optimizing Gr/GQDs as high-performance anode materials for next-generation LIBs.

In-situ synthesis of Ge/reduced graphene oxide composites as ultrahigh rate anode for lithium-ion battery

This study explores the electrochemical properties of additive-free NiCo₂O₄ derived from NiCo-metal-organic frameworks (MOFs) as a high-performance anode material for lithium-ion batteries (LIBs), excluding the effect of additives. NiCo-MOF was synthesized via an ultrasonic-assisted method and deposited on stainless steel foils using alternating current electrophoretic deposition (AC-EPD). The resulting thin films exhibited outstanding cycling stability and rate performance, maintaining a specific capacity of ~1200 mAh/g over 250 cycles at a high current density of 2.35 A/g, with nearly 100% Coulombic efficiency. Differential capacity analysis revealed enhanced redox activity at 0.8 V and 1.7 V during lithiation and delithiation, attributed to the decomposition of NiCo₂O₄ into metallic Ni and Co, followed by their oxidation to Ni2⁺ and Co3⁺, respectively. The gradual activation of electroactive sites, coupled with improved electrode kinetics and structural adjustments, contributed to the observed capacity increase over cycles. These findings underscore the potential of NiCo₂O₄ as a robust and efficient anode material for next-generation LIBs.