Li4 Ti5 O12 Anode: Structural Design from Material to Electrode and the Construction of Energy Storage Devices

TiB4 and SrB8 monolayers: high capacity and zero strain-like anode materials for Li/Na/K/Ca ion batteries

Storage capacity, average open circuit voltage (OCV), diffusion barrier, lattice parameter changes, etc. are key indicators of whether a material would be suitable for use as a Li-ion or non-Li-ion battery (LIB or NLIB) anode. The rapid development of 2D materials over the past few decades has opened up new possibilities for these metrics. Using first-principles calculations, we prove that two 2D materials, TiB4 and SrB8, show excellent performance in terms of the above metrics when used as anodes for LIBs or NLIBs. As detailed, TiB4 has an Li\Na\K\Ca storage capacity of 588 mA h g-1, 588 mA h g-1, 588 mA h g-1, and 1176 mA h g-1, respectively, and SrB8 has an Li\Na\K\Ca storage capacity of 308 mA h g-1, 308 mA h g-1, 462 mA h g-1, and 616 mA h g-1, respectively, and they show good electrical conductivity whether existing Li, Na, K or Ca is adsorbed or not. The diffusion barriers on both surfaces are low, indicating good rate performance. The average OCV is also very low. In particular, the lattice parameters of the two materials change very little during the embedding of Li\Na\K\Ca. For Ti9B36 the corresponding values are about 0.37% (Li), 0.33% (Na), 0.64% (K) and 0.03% (Ca), and for Sr8B64 the corresponding values are about 0.70% (Li), 0.16% (Na), 0.13% (K) and 0.004% (Ca), which imply zero strain-like character and great cycling performance. All the above results show that TiB4 and SrB8 monolayers are very promising Li\Na\K\Ca ion battery anodes.

Suppressing gas swelling in self-assembled Li4Ti5O12 (400) for high-performance rechargeable batteries

Lithium titanate is a promising anode material for lithium-ion batteries due to its high-rate capability and long-cycle duration. However, gas swelling during electrochemical reactions has hindered its industrial application. Here, we synthesize self-assembled (400)-orientation lithium titanate (SA-LTONF) with ultrafine nanoparticles using a feasible thermal method. The SA-LTONF with an organic carbon coating exhibited superior electrochemical performance. To understand such high-rate capability, we perform density functional theory (DFT) calculations which elucidate the orientation-dependent electrochemical mechanism of hydrogen evolution and the atomically dynamic mechanism of lithium-ion migration in Li4Ti5O12 and Li7Ti5O12. Our findings provide a unique insight into the gas generation and ultrafast lithium-ion transportation in lithium titanate and offer guidance for nanoarchitecture construction and materials design of lithium titanate for commercial applications.

Electrochemical evaluation of porous CaFe2O4 anode material prepared via solution combustion synthesis at increasing fuel-to-oxidizer ratios and calcination temperatures

The drawbacks of common anodes in lithium-ion batteries (LIBs) and hybrid supercapacitors (HSCs), such as the high voltage plateau of Li₄Ti₅O₁₂ (1.55 V vs. Li/Li⁺) and the moderate capacity of graphite (372 mAh-g^-1), have established a need for better materials. Conversion materials, and in particular iron oxide and CaFe₂O₄ (CFO), have amassed recent attention as potential anode replacements. In this study, we evaluate the material and electrochemical effects of the solution combustion synthesis (SCS) of porous CFO across novel fuel-to-oxidizer ratios and calcination temperatures. We demonstrate that nearly doubling the amount of fuel used during synthesis increases capacities between 120 and 150% at high current densities (~ 1000 mA-g^-1) and across 500 additional charging-discharging cycles, an effect brought on in part by enhanced compositional purity in these samples. However, in order to ensure long-term cyclic stability, it is necessary to also calcine porous CFO to 900 °C to enhance crystallite size, particle size and spacing, and compositional purity.

Polymer-templated mesoporous lithium titanate microspheres for high-performance lithium batteries

The spinel Li4Ti5O12 (LTO) is a promising lithium ion battery anode material with the potential to supplement graphite as an industry standard, but its low electrical conductivity and Li-ion diffusivity need to be overcome. Here, mesoporous LTO microspheres with carbon-coatings were formed by phase separation of a homopolymer from microphase-separated block copolymers of varying molar masses containing sol-gel precursors. Upon heating the composite underwent a sol-gel condensation reaction followed by the eventual pyrolysis of the polymer templates. The optimised mesoporous LTO microspheres demonstrated an excellent electrochemical performance with an excellent specific discharge capacity of 164 mA h g-1, 95% of which was retained after 1000 cycles at a C-rate of 10.

FeNb2O6/reduced graphene oxide composites with intercalation pseudo-capacitance enabling ultrahigh energy density for lithium-ion capacitors

Lithium-ion capacitors (LICs), which combine the characteristics of lithium-ion batteries and supercapacitors, have been well studied recently. Extensive efforts are devoted to developing fast Li⁺ insertion/deintercalation anode materials to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes. Herein, we design a FeNb₂O₆/reduced graphene oxide (FNO/rGO) hybrid material as a fast-charge anode that provides a solution to the aforementioned issue. The synergetic combination of FeNb₂O₆, whose unique structure promotes fast electron transport, and highly conductive graphene shortens the Li⁺ diffusion pathways and enhances structural stability, leading to excellent electrochemical performance of the FNO/rGO anode, including a high capacity (770 mA h g⁻¹ at 0.05 A g⁻¹) and long cycle stability (95.3% capacitance retention after 500 cycles). Furthermore, the FNO/rGO//ACs LIC achieves an ultrahigh energy density of 135.6 W h kg⁻¹ (at 2000 W kg⁻¹) with a wide working potential window from 0.01 to 4 V and remarkable cycling performance (88.5% capacity retention after 5000 cycles at 2 A g⁻¹).

FeNb₂O₆/reduced graphene oxide (FNO/rGO) hybrid material as a fast charge anode for LICs that provides a solution to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes.

Focus on Spinel Li4 Ti5 O12 as Insertion Type Anode for High-Performance Na-Ion Batteries

Sodium-ion batteries (SIBs) toward large-scale energy storage applications has fascinated researchers in recent years owing to the low cost, environmental friendliness, and inestimable abundance. The similar chemical and electrochemical properties of sodium and lithium make sodium an easy substitute for lithium in lithium-ion batteries. However, the main issues of limited cycle life, low energy density, and poor power density hamper the commercialization process. In the last few years, the development of electrode materials for SIBs has been dedicated to improving sodium storage capacities, high energy density, and long cycle life. The insertion type spinel Li₄ Ti₅ O₁₂ (LTO) possesses "zero-strain" behavior that offers the best cycle life performance among all reported oxide-based anodes, displaying a capacity of 155 mAh g^-1 via a three-phase separation mechanism, and competing for future topmost high energy anode for SIBs. Recent reports offer improvement of overall electrode performance through carbon coating, doping, composites with metal oxides, and surface modification techniques, etc. Further, LTO anode with its structure and properties for SIBs is described and effective methods to improve the LTO performance are discussed in both half-cell and practical configuration, i.e., full-cell, along with future perspectives and solutions to promote its use.

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

Although Li₄Ti₅O₁₂ (LTO) is considered as a promising anode material for high-power Li-ion batteries with high safety, the sluggish Li-ion diffusion coefficient restricts its widespread 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 capacities of 173.4 mAh g^-1 at 1C rate after 100 cycles and 140.5 mAh g^-1 at 5C after 1000 cycles than those of pristine LTO. Meanwhile, even at a high rate of 20C, it displays an ultrahigh capacity of 133.1 mAh g^-1 after 500 cycles with a Coulombic efficiency of 100%. Detailed analysis reveals that the lithium storage mechanisms in the oxygen-deficient LTO, especially at high rate, were dominated by the insertion behavior and dual-phase conversion due to the fast ion-diffusion ability, rather than the widely reported surface capacitance by other approaches. This work highlights that defect generation by plasma in nanomaterials is an effective way to promote ion mobility, especially at high rates, and thus can be extended to other electrode materials for advanced energy-storage applications.