Plasma-Introduced Oxygen Defects Confined in Li₄Ti₅O₁₂ Nanosheets for Boosting Lithium-Ion Diffusion

Abstract

Although Li4Ti5O12 (LTO) is considered as promising anode material for high-power Li-ion battery with high safety, the sluggish Li-ion diffusion coefficient restricts its wide application. In this work, oxygen vacancy was successfully incorporated into LTO by an eco-friendly and cost-effective plasma process. The deficient LTO delivers much higher capacity of 173.4 mAh g-1 at 1 C rate after 100 cycles and 140.5 mAh g-1 at 5 C after 1000 cycles than those of the pristine LTO. Meanwhile, even at high rate of 20 C it displays an ultrahigh capacity of 133.1 mAh g-1 after 500 cycles with a Coulombic efficiency of 100%. Detailed analysis discovers that the lithium storage mechanisms in the oxygen-deficient LTO, especially at high rate, were dominated by the insertion behavior and dual-phases conversion due to the fast ion diffusion ability, rather than the widely reported surface capacitance by other approaches. This work highlights that the defect generation by plasma in nanomaterials is an effective way to promote the ion mobility, especially at high rate, thus can be extended to other electrode materials for advanced energy-storage applications.

Defect Engineering on Electrode Materials for Rechargeable Batteries

“…Therefore, the rational design of electrode materials with abundant active sites is needed to further improve energy and power density for better application in batteries. As a powerful technology, defect engineering can give electrode materials some new functions, such as more active sites, faster ions diffusion, etc . In addition, the presence of defects can increase the surface energy of the system and promote electrochemical phase transitions .…”

Ti3+ Self‐Doped Li4Ti5O12 Anchored on N‐Doped Carbon Nanofiber Arrays for Ultrafast Lithium‐Ion Storage

“…It reveals the advantages of oxygen vacancies and NCF arrays, which can ensure the structure intact after cycling (Figure S8, Supporting Information). Our H‐LTO@NCF electrode exhibits better cycling stability (with only 0.15% degradation rate per 100 cycles after 10 000 cycles) than many other LTO‐based electrodes such as mesoporous LTO nanosheets (0.44% after 1000 cycles), LTO‐rGO film (1.00% after 500 cycles) and LTO nanosheets with oxygen defects (1.83% after 1000 cycles) (Table S1, Supporting Information).…”

“…The production of lithium‐ion batteries (LIBs) with high power density is highly desired for the growing market of hybrid and electrical vehicles . Spinel lithium titanite (Li 4 Ti 5 O 12 , LTO), as a high‐rate anodic electrode of LIBs, has roused much attention .…”

“…Ion doping can enhance the intrinsic properties of LTO through influencing the lattice structure and chemical bond and thereby facilitate the electron/ion transport within the crystal . Till now, a variety kind of ions have been studied, such as N 3− , F − , Al 3+ , Mn 4+ , and Mo 6+ .…”

Recent Developments of Nanomaterials and Nanostructures for High‐Rate Lithium Ion Batteries

“…Experimentally, Meng et al incorporated oxygen vacancies in MoO 2 anode by annealing precursors in nitrogen atmosphere at 600°C for 3 h. [117] The effect of oxygen vacancies on lithium migration was studied by density functional theory, which revealed that the unbalanced charge distribution around the oxygen vacancies has preferential orientation pointing to neighbouring Mo sites, as shown in Figure 13e and f. [117] As a result, a positively charged area around the vacancy centre with a local built-in electric field are formed, as shown in Figure 13g, which enhance the migration ability of lithium ions by providing extra columbic force in the negative-charged area. [117] In addition to annealing, plasma treatment was reported to introduce oxygen vacancies in conventional anode material (Li 4 Ti 5 O 12 , LTO) by Zhu et al [118] The authors argue that the incorporation of oxygen vacancies by bombardment of energetic particles tends to reduce Ti 4 + to Ti 3 + to some extent in order to maintain the overall neutrality, which results in a slightly expanded lattice, and thus facilitates lithium migration. [119] As described above, the transport of lithium ions is affected by a series of factors, including temperature, stress/strain, interaction between species in the system, as well as the presence of point defects.…”