Graphite, a predominantly chosen anode material for commercial lithium ion batteries (LIBs), has been reported to have negligible intercalation capacity as an anode for sodium ion batteries (NIBs). Disordered carbon exhibits high Na intercalation capacity and emerges as a leading candidate for NIB applications.However, the mechanism of Na + ion insertion into disordered carbon is still controversial. Here, wepropose an ab initio model for disordered carbon and investigate the intercalation mechanism of Na into the layered domains. Our ab initio calculations reveal that a larger interlayer distance and the presence of defects can effectively overcome the van der Waals interaction between graphene sheets and help Na intercalation to form NaC 8 . The calculation results clarify the mechanism of the Na intercalation and account for the presence of sloping and flat regions of charge-discharge curves in disordered carbon reported in numerous experiments. This reveals new prospects for helping Na intercalation into graphite.

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The Li 4 Ti 5 O 12 defect spinel is a promising anode material for lithium ion batteries because it transforms to/from Li 7 Ti 5 O 12 with a negligible volume change during charging/discharging. Ab initio calculation is a powerful approach for modern materials design and mechanistic studies. However, the atomistic models of the stoichiometric Li 4 Ti 5 O 12 and Li 7 Ti 5 O 12 defect spinel have not been optimized due to the requirements of large unit cells and numerous atomistic arrangements of Li and Ti ions at the 16d sites of the defect spinel. In this study, ab initio calculations were systematically performed and the most energetically favorable full supercell models were constructed for both Li 4 Ti 5 O 12 and Li 7 Ti 5 O 12 defect spinel. The equilibrium lattice parameter of Li 4 Ti 5 O 12 was 8.4257 Å, while a slight lattice shrinkage of 0.77% and an average intercalation voltage of 1.41 V during charging/discharging were obtained. Moreover, the Li 4 Ti 5 O 12 phase shows insulating property with a wide bandgap of around 2.3 eV, while the Li 7 Ti 5 O 12 phase exhibits metallic property. All the calculated structural and electrochemical properties agree closely with the experimental findings in literature. Further theoretical studies on the Li 4 Ti 5 O 12 defect spinel or other defect spinel in general can be realized according to the full supercell models proposed in this study.

The garnet-type Li7La3Zr2O12 (LLZO) ceramic solid electrolyte combines high Li-ion conductivity at room temperature with high chemical stability. Several all-solid-state Li batteries featuring the LLZO electrolyte and the LiCoO2 (LCO) or LiCoO2–LLZO composite cathode were demonstrated. However, all batteries exhibit rapid capacity fading during cycling, which is often attributed to the formation of cracks due to volume expansion and the contraction of LCO. Excluding the possibility of mechanical failure due to crack formation between the LiCoO2/LLZO interface, a detailed investigation of the LiCoO2/LLZO interface before and after cycling clearly demonstrated cation diffusion between LiCoO2 and the LLZO. This electrochemically driven cation diffusion during cycling causes the formation of an amorphous secondary phase interlayer with high impedance, leading to the observed capacity fading. Furthermore, thermodynamic analysis using density functional theory confirms the possibility of low- or non-conducting secondary phases forming during cycling and offers an additional explanation for the observed capacity fading. Understanding the presented degradation paves the way to increase the cycling stability of garnet-based all-solid-state Li batteries.

incorporation of conductive agents, [9][10][11] doping of metal ions, [12][13][14] and nanonization, that is, reduction in particle size. [15,16] Although all of these methods yielded notable results, our proposed alternative synthesis is greatly on-par, in addition to being a one-pot, facile, and inexpensive process which requires no additional precursors and processing-a very favorable route with manufacturing considerations.Chiang and co-workers summarized available electronic conductivity data for LTO, in which the defective-LTO (with oxygen vacancies) was of the highest reported electronic conductivity. [17] Therefore, it has gotten great interest and numerous researchers had engineered processes to generate oxygen vacancies in the LTO structure. [18][19][20] With amorphous carbon coating, Chen and co-workers demonstrated lower Li ion (Li + ) interfacial transfer resistance which dramatically enhanced the battery performance. [21] Altogether achieving a "double" effect, Wang et al. introduced nanosized LTO with surface modifications of Ti (III) and carbon with improved surface conductivity and restricted particle growth due to the carbonization of polyaniline (PANI); [22] however, they were not able to maximize the effects of oxygen vacancies by generating a low level; and their nonuniform carbon layers can possibly impede Li + transport, especially when graphitized. [23] Finally, the importance of these modifications in relation to the Li + interfacial charge-transfer resistance was not highlighted in the aforementioned studies.Herein, we propose a one-pot, facile, and extremely inexpensive strategy by using conventional solid-state precursors of lithium carbonate (Li 2 CO 3 ) and titanium oxide (TiO 2 ) in an ethanol solution, through which a high level of oxygen vacancies and conformal amorphous carbon coating were simultaneously achieved. The formation mechanism of the one-pot synthesized, highly oxygen-deficient, and amorphous-carbon-coated LTO, as well as the origin of its superior electrochemical properties, are elaborated with the aid of the ab initio calculation. The enhanced interfacial electrochemical properties as well as the stabilization of highly oxygen-deficient structure are attributed to the conformal amorphous carbon. The dramatic reduction of overall resistance was in the Li + interfacial charge transfer, which sheds light to an emerging importance of interfacial modification, is highlighted in this paper.The lithium titanate defect spinel, Li 4 Ti 5 O 12 (LTO), is a promising "zero-strain" anode material for lithium-ion batteries in cycling-demanding applications. However, the low-rate capability limits its range of applications. Surface modifications, for example, coating and defect engineering, play an intriguing role in interfacial electrochemical processes. Herein, a novel synthesis of highly oxygen-deficient "defective-LTO" anode material with highrate performance is reported. It is synthesized using conventional precursors via a one-pot thermal reduction process. A high level of ox...

Ga-substituted Li7La3Zr2O12 (LLZO) garnet is among the most promising solid electrolytes for next-generation all-solid-state Li battery (SSLB) applications due to its very high Li-ion conductivity. However, the attempts to use...

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The Cu–Sn binary system is important for various applications, especially for recent developments in the electronics packaging industry. The ϵ-Cu3Sn and η-Cu6Sn5 (η′ phases) phases are frequently encountered in electronics products. However, the two phases have been described as line compounds in previous thermodynamic modeling, and their compositional homogeneities were not considered. In this study, the thermodynamic properties of the Cu–Sn binary system are modeled and the phase diagram is calculated by the CALPHAD method, using experimental information reported in the literature. The ϵ and η (η′) phases are described using compound energy models with two and three sublattices, respectively, so that their compositional homogeneities could be calculated. Good agreement was observed between the calculated result and the existing experimental data.