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Predicting the Electrochemical Properties of MnO2Nanomaterials Used in Rechargeable Li Batteries: Simulating Nanostructure at the Atomistic Level

Sayle, T.X.T., Maphanga, R. Rapela, Ngoepe, Phuti E., Sayle, Dean C. (2009) Predicting the Electrochemical Properties of MnO2Nanomaterials Used in Rechargeable Li Batteries: Simulating Nanostructure at the Atomistic Level. Journal of the American Chemical Society, 131 (17). pp. 6161-6173. ISSN 1520-5126. (doi:10.1021/ja8082335) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:40490)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided.
Official URL:
http://dx.doi.org/10.1021/ja8082335

Abstract

Nanoporous ?-MnO2 can act as a host lattice for the insertion and deinsertion of Li with application in rechargeable lithium batteries. We predict that, to maximize its electrochemical properties, the ?-MnO2 host should be symmetrically porous and heavily twinned. In addition, we predict that there exists a “critical (wall) thickness” for MnO2 nanomaterials above which the strain associated with Li insertion is accommodated via a plastic, rather than elastic, deformation of the host lattice leading to property fading upon cycling. We predict that this critical thickness lies between 10 and 100 nm for ?-MnO2 and is greater than 100 nm for ?-MnO2: the latter accommodates 2 × 2 tunnels compared with the smaller 1 × 1 tunnels found in ?-MnO2. This prediction may help explain why certain (nano)forms of MnO2 are electrochemically active, while others are not. Our predictions are based upon atomistic models of ?-MnO2 nanomaterials. In particular, a systematic strategy, analogous to methods widely and routinely used to model crystal structure, was used to generate the nanostructures. Specifically, the (space) symmetry associated with the nanostructure coupled with basis nanoparticles was used to prescribe full atomistic models of nanoparticles (0D), nanorods (1D), nanosheets (2D), and nanoporous (3D) architectures. For the latter, under MD simulation, the amorphous nanoparticles agglomerate together with their periodic neighbors to formulate the walls of the nanomaterial; the particular polymorphic structure was evolved using simulated amorphization and crystallization. We show that our atomistic models are in accord with experiment. Our models reveal that the periodic framework architecture, together with microtwinning, enables insertion of Li anywhere on the (internal) surface and facilitates Li transport in all three spatial directions within the host lattice. Accordingly, the symmetrically porous MnO2 can expand and contract linearly and crucially elastically under charge/discharge. We also suggest tentatively that our predictions for MnO2 are more general in that similar arguments may apply to other nanomaterials, which might expand and contract elastically upon charging/discharging.

Item Type: Article
DOI/Identification number: 10.1021/ja8082335
Subjects: Q Science
Q Science > QC Physics
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Stewart Brownrigg
Date Deposited: 07 Mar 2014 00:05 UTC
Last Modified: 16 Nov 2021 10:15 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/40490 (The current URI for this page, for reference purposes)

University of Kent Author Information

Sayle, T.X.T..

Creator's ORCID:
CReDIT Contributor Roles:

Sayle, Dean C..

Creator's ORCID: https://orcid.org/0000-0001-7227-9010
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