Integrated Fast Assembly of Free-Standing Lithium Titanate/Carbon Nanotube/Cellulose Nanofiber Hybrid Network Film as Flexible Paper-Electrode for Lithium-Ion Batteries

Abstract

A free-standing lithium titanate (Li4Ti5O12)/carbon nanotube/cellulose nanofiber hybrid network film is successfully assembled by using a pressure-controlled aqueous extrusion process, which is highly efficient and easily to scale up from the perspective of disposable and recyclable device production. This hybrid network film used as a lithium-ion battery (LIB) electrode has a dual-layer structure consisting of Li4Ti5O12/carbon nanotube/cellulose nanofiber composites (hereinafter referred to as LTO/CNT/CNF), and carbon nanotube/cellulose nanofiber composites (hereinafter referred to as CNT/CNF). In the heterogeneous fibrous network of the hybrid film, CNF serves simultaneously as building skeleton and a biosourced binder, which substitutes traditional toxic solvents and synthetic polymer binders. Of importance here is that the CNT/CNF layer is used as a lightweight current collector to replace traditional heavy metal foils, which therefore reduces the total mass of the electrode while keeping the same areal loading of active materials. The free-standing network film with high flexibility is easy to handle, and has extremely good conductivity, up to 15.0 S cm(-1). The flexible paper-electrode for LIBs shows very good high rate cycling performance, and the specific charge/discharge capacity values are up to 142 mAh g(-1) even at a current rate of 10 C. On the basis of the mild condition and fast assembly process, a CNF template fulfills multiple functions in the fabrication of paper-electrode for LIBs, which would offer an ever increasing potential for high energy density, low cost, and environmentally friendly flexible electronics.

Challenges of Spinel Li4Ti5O12 for Lithium‐Ion Battery Industrial Applications

“…In comparison, many kinds of organic carbon precursors are used for preparing high-rate Li 4 Ti 5 O 12 /C anodic materials, because the organic carbon precursors are prone to forming uniform and thickness-controllable carbon films on the surface of Li 4 Ti 5 O 12 particles during the pyrolysis process. On the other hand, inorganic carbon sources (such as graphene, [30] carbon nanotubes (CNTs), [31] black carbon, [32] wileyonlinelibrary.com active carbon, [33] graphitized nano-carbon [34] and bamboo carbon, [35] etc.) Common organic carbon sources used for improving the rate performance of Li 4 Ti 5 O 12 anodes include sucrose, [23] glucose, [23] malic acid, [24] citric acid, [25] pitch, [26] ethylenediamine (EDA), [27] certain polymers, [28] and so forth.…”

“…However, although almost all of the organic materials can be decomposed into carbon after pyrolysis, the conductivity and degree of graphitization are different. Among the kinds of inorganic carbon sources, the low-dimensional graphene [30,36] and CNTs [31,37] carbon sources can obviously improve the rate performance of Li 4 Ti 5 O 12 batteries, which are summarized in detail in the subsequent "Advanced carbon sources" section. Nugroho et al [29] studied the influence of organic carbon sources with different functional groups and chain lengths (including oleylamine, oleic acid, hexylamine) on the particle size, morphology, crystallinity and electrochemical properties of Li 4 Ti 5 O 12 /C composites.…”

“…CNTs are made from a monolayer of graphene rolled to form a tube. [31,59] Sun et al [60] performed an in situ synthesis of mesoporous nanoscale Li 4 Ti 5 O 12 nanoclusters in a CNT network skeleton via a solution-based method followed by heat treatment to form a binder-free electrode with a high conductivity, flexibility, and mechanical strength. Such unique structures and properties contribute to CNTs popularity in research on carbon materials.…”

Advanced composites of complex Ti-based oxides as anode materials for lithium-ion batteries

“…Inorganic carbon includes carbon nanotubes (CNTs) [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61], graphene [13,40,, carbon nanofibers [90][91][92], activated carbon [93,94], black carbon [95,96] and graphitized nanocarbon [97,98]. Inorganic carbon often exhibits better electronic conduction than organic carbon, yielding a higher rate capability.…”

Lithium Titanate/Carbon Nanotubes Composites Processed by Ultrasound Irradiation as Anodes for Lithium Ion Batteries

“…In spite of being quite similar to the results obtained for nLTO/SWCNT composites under the same conditions, the coulombic efficiency of the ink jet printed devices is lower (around 98%). Still in the same thickness range, LTO/CNT composites prepared by extrusion 46 and template-based solution route 47 present capacities of 142 mAh.g −1 (1.75 A.g −1 ) and 81 mAh.g −1 (17.5 A.g −1 ), respectively. All the examples aforementioned show that composites of nLTO and carbon nanotubes, manufactured by a combination of liquid phase processing and ultrasonic spray deposition, can be competitive anodes for large scale industrial applications.…”