The controlled bottom-up design of polymers with metal oxide backbones is a grand challenge in materials design, as it could give unique control over the resulting chemical properties. Herein, we report a 1D-organo-functionalized polyoxometalate polymer featuring a purely inorganic backbone. The polymer is self-assembled from two types of monomers, inorganic Wells-Dawson-type polyoxometalates, and aromatic organo-boronates. Their covalent linkage results in 1D polymer strands, which combine an inorganic oxide backbone (based on BÀO and NbÀO linkages) with functional organic side-chains. The polymer shows high bulk proton conductivity of up to 1.59 10 À1 S cm À1 at 90 8C and 98 % relative humidity. This synthetic approach could lead to a new class of organic-inorganic polymers where function can be designed by controlled tuning of the monomer units.
All-solid-state
potassium batteries are promising candidates in
the fields of large-scale energy storage owing to their intrinsic
safety, stability, and cost-effectiveness. However, a suitable solid-state
electrolyte with high ionic conductivity and favorable interfacial
stability is a major challenge for the design and development of these
batteries. Herein, we report the synthesis of new KB3H8·nNH3B3H7 (n = 0.5 and 1) complexes to develop suitable solid-state
K-ion conductors for batteries. Both the complexes undergo a reversible
phase transition below the thermal decomposition temperature. The
optimal KB3H8·NH3B3H7 delivers a solid-state K-ion conductivity of 1.3 ×
10–4 S cm–1 at 55 °C with
an activation energy of 0.44 eV after a transition from a monoclinic
to an orthorhombic phase, which is the highest value of K borohydrides
reported to date and places KB3H8·NH3B3H7 among the leading solid-state K-ion
conductors. Moreover, KB3H8·NH3B3H7 reveals a K-ion transference number of
nearly 0.93, an electrochemical stability window of 1.2 to 3.5 V vs
K+/K, a good capability of K dendrite suppression, and
a remarkable stability against the K metal anode due to the formation
of the stable interface. These performances make KB3H8·NH3B3H7 a promising
electrolyte for all-solid-state potassium batteries.
Solid-state
electrolytes based on closo-decaborates
have caught increasing interest owing to the impressive room-temperature
ionic conductivity, remarkable thermal/chemical stability, and excellent
deformability. In order to develop new solid-state ion conductors,
we investigated the influence of iodine substitution on the thermal,
structural, and ionic conduction properties of closo-decaborates. A series of iodinated closo-decaborates,
M2[B10H10–n
I
n
] (M = Li, Na; n =
1, 2, 10), were synthesized and characterized by thermal analysis,
powder X-ray diffraction, and electrochemical impedance spectroscopy;
the stability and ionic conductivity of these compounds were studied.
It was found that with the increase of iodine substitution on the closo-decaborate anion cage, the thermal decomposition temperature
increases. All M2[B10H10–n
I
n
] exhibit an amorphous
structure. The ionic conductivity of Li2[B10H10–n
I
n
] is higher than that of the Li2[B10H10] parent compound. An ionic conductivity of 2.96 × 10–2 S cm–1 with an activation energy of 0.23 eV was
observed for Li2[B10I10] at 300 °C,
implying that iodine substitution can improve the ionic conductivity.
However, the ionic conductivity of Na2[B10H10–n
I
n
]
is lower than that of Na2[B10H10]
and increases with the increase of iodine substitution, which could
be associated with the increase of the electrostatic potential, mass,
and volume of the iodinated anions. Moreover, Li2[B10I10] offers a Li-ion transference number of 0.999,
an electrochemical stability window of 3.3 V and good compatibility
with the Li anode, demonstrating its potential for application in
high-temperature batteries.
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