Title: A reactive force field study of Li/C systems for electrical energy storage

Abstract

Graphitic carbon is still the most ubiquitously used anode material in Li-ion batteries. In spite of its ubiquity, there are few theoretical studies that fully capture the energetics and kinetics of Li in graphite and related nanostructures at experimentally relevant length, time-scales, and Li-ion concentrations. In this paper, we describe the development and application of a ReaxFF reactive force field to describe Li interactions in perfect and defective carbon-based materials using atomistic simulations. We develop force field parameters for Li–C systems using van der Waals-corrected density functional theory (DFT). Grand canonical Monte Carlo simulations of Li intercalation in perfect graphite with this new force field not only give a voltage profile in good agreement with known experimental and DFT results but also capture the in-plane Li ordering and interlayer separations for stage I and II compounds. In defective graphite, the ratio of Li/C (i.e., the capacitance increases and voltage shifts) both in proportion to the concentration of vacancy defects and metallic lithium is observed to explain the lithium plating seen in recent experiments. We also demonstrate the robustness of the force field by simulating model carbon nanostructures (i.e., both 0D and 1D structures) that can be potentially used as batterymore » electrode materials. Whereas a 0D defective onion-like carbon facilitates fast charging/discharging rates by surface Li adsorption, a 1D defect-free carbon nanorod requires a critical density of Li for intercalation to occur at the edges. Our force field approach opens the opportunity for studying energetics and kinetics of perfect and defective Li/C structures containing thousands of atoms as a function of intercalation. As a result, this is a key step toward modeling of realistic carbon materials for energy applications.« less

Authors:

Raju, Muralikrishna ^[1]; Ganesh, P. ^[2]; Kent, Paul R. C. ^[2]; van Duin, Adri C.T. ^[1]

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+ Show Author Affiliations

1. The Pennsylvania State Univ., University Park, PA (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Thu Apr 02 00:00:00 EDT 2015

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1185648

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Theory and Computation

Additional Journal Information:

Journal Volume: 11; Journal Issue: 5; Journal ID: ISSN 1549-9618

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

25 ENERGY STORAGE; Li intercalation; Li diffusion; graphene; graphite; carbon onions; Li-ion battery; reactive force-field; supercapacitor