Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Defect physics, delithiation mechanism, and electronic and ionic
  conduction in layered lithium manganese oxide cathode materials   Layered LiMnO$_2$ and Li$_2$MnO$_3$ are of great interest for lithium-ion
battery cathodes because of their high theoretical capacities. The practical
application of these materials is, however, limited due to poor electrochemical
performance. We herein report a comprehensive first-principles study of defect
physics in LiMnO$_2$ and Li$_2$MnO$_3$ using hybrid-density functional
calculations. We find that manganese antisites have low formation energies in
LiMnO$_2$ and may act as nucleation sites for the formation of impurity phases.
The antisites can also occur with high concentrations in Li$_2$MnO$_3$;
however, unlike in LiMnO$_2$, they can be eliminated by tuning the experimental
conditions during preparation. Other intrinsic point defects may also occur and
have an impact on the materials' properties and functioning. An analysis of the
formation of lithium vacancies indicates that lithium extraction from LiMnO$_2$
is associated with oxidation at the manganese site, resulting in the formation
of manganese small hole polarons; whereas in Li$_2$MnO$_3$ the intrinsic
delithiation mechanism involves oxidation at the oxygen site, leading to the
formation of bound oxygen hole polarons $\eta_{\rm O}^{+}$. The layered oxides
are found to have no or negligible bandlike carriers and they cannot be doped
n- or p-type. The electronic conduction proceeds through hopping of hole and/or
electron polarons; the ionic conduction occurs through lithium monovacancy
and/or divacancy migration mechanisms. Since $\eta_{\rm O}^{+}$ is not stable
in the absence of negatively charged lithium vacancies in bulk Li$_2$MnO$_3$,
the electronic conduction near the start of delithiation is likely to be poor.
We suggest that the electronic conduction associated with $\eta_{\rm O}^{+}$
and, hence, the electrochemical performance of Li$_2$MnO$_3$ can be improved
through nanostructuring and/or ion substitution.

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The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th