sp²/sp³ Hybridized Carbon as an Anode with Extra Li-Ion Storage Capacity: Construction and Origin

Abstract

Doping in carbon anodes can introduce active sites, usually leading to extra capacity in Li-ion batteries (LIBs), but the underlying reasons have not been uncovered deeply. Herein, the dodecahedral carbon framework (N-DF) with a low nitrogen content (3.06 wt %) is fabricated as the anode material for LIBs, which shows an extra value of 298 mA h g –1 during 250 cycles at 0.1 A g –1 . Various characterizations and theoretical calculations demonstrate that the essence of the extra capacity mainly stems from non-coplanar sp 2 /sp 3 hybridized orbital controlling non-Euclidean geometrical structure, which acts as new Li-ion active sites toward the excess Li + adsorption. The electrochemical kinetics and in situ transmission electron microscope further reveal that the positive and negative curvature architectures not only provide supernumerary Li + storage sites on the surface but also hold an enhanced (002) spacing for fast Li + transport. The sp 2 /sp 3 hybridized orbital design concept will help to develop advanced electrode materials.

Charging a Negatively Curved Nanographene and Its Covalent Network

“…5,6 Interesting properties and potential applications of carbon schwarzites are predicted on the basis of computational studies. 7,8 First-principles calculations suggest potential application of carbon schwarzites in lithium ion batteries as new anode materials, 9 where the negatively curved surface binds lithium ions with higher affinity than a flat surface 10 and the presence of pores enable threedimensional lithium ion diffusion paths with relatively small energy barriers. Fragments that contain key structural information on carbon schwarzites are negatively curved nanographenes, 11−16 which have polycyclic aromatic frameworks containing seven-, 17−27 eight-membered 28−35 or larger rings.…”

“…Mackay, together with Terrones, first proposed negatively curved carbon allotropes by embedding octagons in the graphitic lattice in 1991, while Schwarz in the 1880s first described the triply periodic minimal surface, the topological model for Mackay crystals . Carbon schwarzites are a long-sought-after target in carbon nanoscience but have not been synthesized unambiguously yet. , Interesting properties and potential applications of carbon schwarzites are predicted on the basis of computational studies. , First-principles calculations suggest potential application of carbon schwarzites in lithium ion batteries as new anode materials, where the negatively curved surface binds lithium ions with higher affinity than a flat surface and the presence of pores enable three-dimensional lithium ion diffusion paths with relatively small energy barriers. Fragments that contain key structural information on carbon schwarzites are negatively curved nanographenes, − which have polycyclic aromatic frameworks containing seven-, − eight-membered − or larger rings.…”

Riemannian Surface on Carbon Anodes Enables Li-Ion Storage at −35 °C

“…Therefore, the key to addressing the low-temperature capacity loss lies in adjusting the surface electron configurations of the carbon anode to reinforce the coordinate interaction between the solvated Li + and adsorption sites for Li + desolvation and reduce the activation energy of the charge-transfer process. In addition, with inspiration from the geometric architectures of carbon allotropes with positive and negative curvatures, it is expected to manipulate the electronic configurations of the surface through the transformation of hybridized orbital types generated by the response of chemical bonds to bending deformations, − where the insertion of one pentagon into an sp 2 -hybridized hexagon lattice generates a surface with a positive curvature like a bowl, while the introduction of one heptagon or larger membered rings produces a surface with a negative curvature like a saddle. , Theoretical calculations demonstrate that the curved surfaces bind lithium with a stronger affinity than the planar surface with zero curvature, particularly the structure with a positive curvature (Figure S1), making it possible to accomplish the high capacity of the carbon anode in an extremely cold environment. However, the carbon anode with a positive curvature as a high capacity electrode material for Li-ion storage at low temperature has never been realized, and the underlying structure-performance relation has not been theoretically and experimentally uncovered.…”

Laser Cladding Induced Spherical Graphitic Phases by Super-Assembly of Graphene-Like Microstructures and the Antifriction Behavior

“…Graphene and its related carbon materials have been proved to play significant roles in various applications ranging from energy storage and conversion to bioimaging and biosensors. − Strategies to synthesize graphene-related structures have been developed to facilitate their use in many applications, while their large-scale production and further incorporation into composite materials with desired local structures still remain a challenge. A laser beam is an excellent heat source used in a wide range of materials processing operations, which enables the in situ formation of novel micro- and nanostructures toward a diverse range of application requirements. − In this respect, much attention has been devoted to the surface modification of alloys, and techniques such as pulsed laser deposition, laser shock peening, , laser surface melting, , and laser cladding , have been studied.…”