Atomistic Dynamics Investigation of the Thermomechanical Properties and Li Diffusion Kinetics in ψ-Graphene for LIB Anode Material

Thomas, Siby,Nam, Eun Bi,Lee, Sang Uck American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.42

<P>A fundamental understanding of the thermomechanical properties of electrode materials and Li-ion diffusion kinetics is indispensable for designing high-performance Li-ion batteries (LIBs) with high structural stability and safety. Herein, we performed both molecular dynamics (MD) simulations and density functional theory (DFT) calculations to investigate the thermomechanical properties and Li diffusion kinetics in a two-dimensional (2D) defect-filled graphene-like membrane consisting of 5-, 6-, and 7-membered rings, called psi (ψ)-graphene. Our results reveal that ψ-graphene has a negative linear thermal expansion coefficient, a high specific heat capacity, and high elastic constants that satisfy the Born’s criterion for mechanical stability, which can be elucidated as the evidence of strong anharmonicity in ψ-graphene because of the soft out-of-plane bending modes. These characteristics can help prevent the thermal runaway that can occur during overheating and prevent structural damage because of the severe volume expansion of the LIBs. In addition, the Li diffusion coefficient was estimated to be 10<SUP>-9</SUP> cm<SUP>2</SUP>/s at 300 K with a low Li migration activation energy (<0.16 eV), which suggests favorable electrode kinetics with fast Li conduction. Our DFT calculations also show that ψ-graphene can possess a fairly good theoretical capacity (339 mA h g<SUP>-1</SUP>) and a lower Li diffusion barrier (<0.21 eV). Our results suggest that the new fundamental insights presented here will help to stimulate further experimental work on ψ-graphene for promising future applications as a superior electrode material for LIBs.</P> [FIG OMISSION]</BR>

Phographene as a High-Performance Anode Material with High Specific Capacity and Fast Li Diffusion: From Structural, Electronic, and Mechanical Properties to LIB Applications

Thomas, Siby,Lee, Chi Ho,Jana, Saibal,Jun, Byeongsun,Lee, Sang Uck American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol.123 No.35

<P>The progress of ecofriendly, clean, and sustainable energy resources always demands suitable anode materials for batteries with high structural stability and superior storage capacity. Herein, we use density functional theory predictions to examine the potential features of newly proposed planar membranes consist of 5-, 6- and 8- membered carbon rings, named as α- and β-phographene (PhoG). Our calculations disclose that both α- and β-PhoG structures possess high structural, thermal, and mechanical stability with intrinsic metallic characteristics. We have further extended our calculations of PhoG as a suitable anode material for use in Lithium-ion batteries. Our results reveal the Li adsorption in PhoG is exothermic and the α-PhoG show a higher theoretical specific capacity of Li<SUB>2.4</SUB>C<SUB>6</SUB> for Li atoms (892 mAh g<SUP>-1</SUP>) compared to the LiC<SUB>6</SUB> of graphite. We also found that both the α- and β-PhoG structures show fast Li mobility with a low diffusion barrier for Li atoms (<0.30 eV) as well as low average open circuit voltage (∼0.26 V). Our findings show that both the PhoG structures, especially α-PhoG, are suitable anode candidates for use in future Li-ion batteries owing to the metallic characteristic combined with the low open circuit voltage, low diffusion barrier, high Li storage capacity, and high thermo-mechanical stability. Our results would supply guidelines to develop better high-capacity anode materials for future Li-ion batteries.</P> [FIG OMISSION]</BR>

Two-dimensional haeckelite h567: A promising high capacity and fast Li diffusion anode material for lithium-ion batteries

Thomas, Siby,Jung, Hoejoong,Kim, Suyeon,Jun, Byeongsun,Lee, Chi Ho,Lee, Sang Uck Elsevier 2019 Carbon Vol.148 No.-

<P><B>Abstract</B></P> <P>There is great interest in finding suitable electrode materials for metal-ion batteries with good performance, low diffusion barriers and high capacity. Using the art of density functional theory (DFT), we systematically evaluated the possibility of planar carbon haeckelite structures (h567, r57, and o567) for a suitable anode in Lithium-ion batteries (LIBs). Our results show that haeckelites possess significant structural, mechanical, and electronic stability with high metallicity for LIB anode applications. Especially, the haeckelite h567 shows improved specific capacity (Li<SUB>1<I>.</I>875</SUB>C<SUB>6</SUB> ∼ 697 mAhg<SUP> <I>−</I>1</SUP>) compared to LiC<SUB>6</SUB> graphite due to the negative Li binding energy without clustering of Li atoms. In addition, it is worth noticing that the low open-circuit voltage (<0.30 V) and Li diffusion energy barrier (E<SUB> <I>a</I> </SUB> < 0.35 eV) of the haeckelite h567comparable to that of the graphite is beneficial to the overall performance of the LIBs. Based on the excellent electronic structure, superior Li mobility, extremely high in-plane stiffness, low open-circuit voltage, and high specific capacity, haeckelite h567 can be a promising anode material for the low-cost and high-performance LIBs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Temperature-dependent lithium diffusion in phographene: Insights from molecular dynamics simulation

Siby Thomas,Saibal Jana,Byeongsun Jun,이치호,Sang Uck Lee 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-

It is noteworthy to elucidate the underlying atomistic insights of next-generation battery electrodematerials to overcome the existing constraints associated with its rapid progress. By employing classicalmolecular dynamics (MD) simulations, we have studied the temperature dependent structural, thermomechanical,and Lithium diffusion properties of α- and β-phographene (PhoG) for Lithium-ion battery(LIB) anode applications. Our results show that at 300 K both the PhoGs possess negative thermalexpansion coefficient and is expounded as proof of anharmonicity present in it due to the existence ofpliable bending modes in the out-of-plane direction. The computed ultrahigh stiffness of PhoG helps toprevent the acute lattice expansion issue upon Li intercalation. The study also brings out that Li atomcould freely diffuse on the surface of the PhoGs, and thus a fast Li diffusivity and superior conductivity isobserved. The calculated Li diffusion activation energies (<0.20 eV) of these membranes are lower thanmany of the typical for Li-based graphitic anode with a Li diffusion coefficient of 10 10–10 12cm2 s 1. Inthis regard, the excellent structural and thermo-mechanical stability, and low activation energy barrier inPhoGs assures its application as an anode material in high-performance LIBs.

B3S monolayer: prediction of a high-performance anode material for lithium-ion batteries

Jana, Saibal,Thomas, Siby,Lee, Chi Ho,Jun, Byeongsun,Lee, Sang Uck Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.20

<P>To mitigate the ever-growing global temperature rise, renewable energy is needed and use of fossil fuels has to be reduced on an urgent basis. Next-generation renewable energy technology demands electrode materials with suitable structural, electronic, and mechanical properties. Through particle swarm-intelligence and first-principles structure calculations, we have designed a new novel B3S monolayer, which is dynamically, mechanically, and thermally stable and of higher cohesive energy compared to synthesized B2S3 thus ensuring the feasibility of experimental synthesis. As an anode material, the B3S monolayer can be expected to have high performance with high storage capacity (1662 mA h g<SUP>−1</SUP>), low open-circuit voltage (∼0.16 V) and a low lithium diffusion barrier (<I>E</I>a < 0.4 eV). Furthermore, the metallicity of the B3S monolayer is sustained after lithium adsorption, indicating good electrical conductivity and battery operating cycle. Our results clarify that these intriguing properties make B3S monolayer an appealing candidate for anode material in lithium-ion batteries.</P>

Strain induced structural transformation, mechanical and phonon stability in silicene derived 2D-SiB

Manju M.S.,Siby Thomas,Anees P.,Sang Uck Lee,Ajith K. M. 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.90 No.-

Two-dimensional monolayer SiB is a silicene derivative exhibiting buckling of atoms similar to that seenin silicene. This manuscript presents a systematic study of the strain-dependent variation of thestructural, mechanical, and dynamical properties of SiB. Strain was applied in the uniaxial armchair,uniaxial zigzag, and biaxial directions within the range of0.2 to 0.3. The resultant strain energy plotindicates anisotropic behavior of SiB in these directions. The SiB showed a mechanical strength that washigher than its counterpart, silicene, by an order of 30%. The elastic constant data from the undeformedSiB indicated an anisotropic nature, which was also seen with all the strain directions. Charge densitycontours, along with Bader charge analysis, confirmed the ionic nature of SiB in its original form. Thisnature became covalent as the strain varied from the compressive to the tensile regime in the uniaxialzigzag and biaxial directions. The majorfinding described in this manuscript is a newflat conformationhaving orthorhombic symmetry in contrast to the buckled structure. In addition, this material wasobserved to attain stability with the application of uniaxial tensile armchair and zigzag directionalstrains. Ab-initio molecular dynamics simulation confirmed the thermal stability of SiB in its newconformation.