The formation mechanism of Li4Ti5O12−y solid solutions prepared by carbothermal reduction and the effect of Ti3+ on electrochemical performance

Yang, Guijun; Park, Soo‐Jin

doi:10.1038/s41598-019-41206-0

Cited by 16 publications

(4 citation statements)

References 39 publications

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“…50 As both defective TiO 2 and LTO show the same blue color, 13,17,51 which is attributed in both cases to the presence of Ti 3+ , one can argue that both show a similar position of the defect state within the band gap. 52,53 Following these arguments, we obtain a U value of 2.65 eV, yielding gap state positions around 1 eV below the CBM. Note that a U value of 2.65 eV was already used successfully in a previous work of our group regarding the formation of polarons in LTO.…”

Section: ■ Methodsmentioning

confidence: 64%

Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Kick

Scheurer

Oberhofer

2021

ACS Appl. Energy Mater.

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Lithium-ion batteries are without a doubt a key technology in the coming energy revolution. It is thus all the more surprising that one of the more prevalent Li battery anode materials, reduced lithium titanium oxide (LTO, Li4Ti5O12), is still poorly understood on a microscopic level. While recent theoretical and experimental evidence suggests that a polaron hopping mechanism is responsible for the increased electronic conductivity of reduced LTO, no such explanation exists for the concurrent improvements to the ionic mobility. In this computational study, we show that the presence of polaronic Ti3+ centers can indeed lead to a significant lowering of Li hopping barriers in both bulk and surface reduced LTO. For the latter, we find a reduced barrier height of roughly 40 meV compared to that of our pristine reference. This is in accordance with experimental findings showing that lithium-ion diffusion in reduced LTO is twice as high as that for pristine LTO. Finally, we show thatin accordance with experimental observationspolaron formation upon lithiation of LTO leads to a similar behavior. Altogether, our analysis hints at a correlated movement of Li ions and polarons, highlighting LTO’s potential for rational defect engineering.

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Section: ■ Methodsmentioning

confidence: 64%

Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Kick

Scheurer

Oberhofer

2021

ACS Appl. Energy Mater.

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“…The first endothermic peak located at around 85 °C with a weight loss of 3.4% corresponds to the dehydration process of the water adsorbed at the surface of the sample. 42 By increasing the temperature to 195 °C, the second endothermic peak is closely related to the phase transformation from H 2 Ti 3 O 7 to TiO 2 (B). 40 The corresponding weight loss for this process is 8.0% (11.4–3.4%), which is very close to the theoretical value (7.0%).…”

Section: Resultsmentioning

confidence: 99%

Phase transformation and interface crystallography between TiO₂ and different Ti_nO_2n−1 phases

Yang

et al. 2023

CrystEngComm

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“…The Li + diffusion coefficients ( D Li + ) of the five cells can be calculated according to the Randles–Sevcik equation as follows , where A is the contact area of the electrode (1.13 cm 2 ), n is the number of electrons in the redox reaction, C 0 is the molar concentration of lithium ions (mol/cm 3 ), and ν is the sweep rate of potential (V/s). Thus, the lithium-ion diffusion coefficients of LTO-P25, LTO-AG, LTO-FL, LTO-8602, LTO-P25/LFP, and LTO-AG/LFP are 6.86 × 10 –12 , 5.84 × 10 –12 , 3.89 × 10 –13 , 6.44 × 10 –12 , 9.70 × 10 –13 , and 3.55 × 10 –13 cm 2 /s, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…The Li + diffusion coefficients (D Li + ) of the five cells can be calculated according to the Randles−Sevcik equation as follows 44,45…”

Section: T H Imentioning

confidence: 99%

Unveiling the Formation Mechanism and Phase Purity Control of Nanostructured Li₄Ti₅O₁₂ via a Hydrothermal Process

Dai

Manawan

et al. 2021

Crystal Growth & Design

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Although numerous efforts have been devoted to the spinal Li 4 Ti 5 O 12 anode material of lithium-ion batteries (LIBs), controllable synthesis of high-purity Li 4 Ti 5 O 12 nanoparticles under hydrothermal conditions has not yet been achieved. The current work systematically investigates the relationship between phase compositions of the Li−Ti−O system with the corresponding critical conditions. By determining the phase composition using the Rietveld refinement of XRD patterns, the relationship between key hydrothermal parameters and the resultant purity of Li 4 Ti 5 O 12 is revealed, and the formation mechanism of Li 4 Ti 5 O 12 using crystalline TiO 2 nanoparticles (Evonik Aeroxide P25, Hombikat 8602, and rutile TiO 2 ) and amorphous hydrous TiO 2 spheres (AHTS) as TiO 2 precursors in an aqueous LiOH solution is demonstrated accordingly. The hydrothermal process cannot generate Li 4 Ti 5 O 12 directly, while lithium titanium oxide intermediates (LTOIs), e.g., Li 2 TiO 3 and Li 2−x H x Ti 2 O 4 (OH) 2 , are obtained upon partial lithiation of crystalline or amorphous TiO 2 in the LiOH solution, respectively. Nanostructured TiO 2 @LTOIs can be formed since the underlying phase transition follows the classic in situ crystallization mechanism, as evidenced by the successful self-template synthesis using AHTS. Li 4 Ti 5 O 12 is formed by the solid-state reaction between the TiO 2 core and the LTOI shell at elevated temperatures (∼700 °C). At optimal conditions, the molar ratio of Li/Ti in all TiO 2 @LTOIs should be greater than a stoichiometric ratio of 4:5 since the solid-state reaction is found to promote the evaporation of lithium species. The comparative studies for the lithium storage properties of our assembled half-and full-cell LIBs demonstrate that the high phase purity of Li 4 Ti 5 O 12 enhances the electrochemical performances and that the spherical morphology delivers better cyclic stability.

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The formation mechanism of Li4Ti5O12−y solid solutions prepared by carbothermal reduction and the effect of Ti3+ on electrochemical performance

Cited by 16 publications

References 39 publications

Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Phase transformation and interface crystallography between TiO₂ and different Ti_nO_2n−1 phases

Unveiling the Formation Mechanism and Phase Purity Control of Nanostructured Li₄Ti₅O₁₂ via a Hydrothermal Process

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The formation mechanism of Li4Ti5O12−y solid solutions prepared by carbothermal reduction and the effect of Ti3+ on electrochemical performance

Cited by 16 publications

References 39 publications

Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Polaron-Assisted Charge Transport in Li-Ion Battery Anode Materials

Phase transformation and interface crystallography between TiO2 and different TinO2n−1 phases

Unveiling the Formation Mechanism and Phase Purity Control of Nanostructured Li4Ti5O12 via a Hydrothermal Process

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Phase transformation and interface crystallography between TiO₂ and different Ti_nO_2n−1 phases

Unveiling the Formation Mechanism and Phase Purity Control of Nanostructured Li₄Ti₅O₁₂ via a Hydrothermal Process