Balancing
interfacial stability and Li+ transfer kinetics
through surface engineering is a key challenge in developing high-performance
battery materials. Although conformal coating enabled by atomic layer
deposition (ALD) has shown great promise in controlling impedance
increase upon cycling by minimizing side reactions at the electrode–electrolyte
interface, the coating layer itself usually exhibits poor Li+ conductivity and impedes surface charge transfer. In this work,
we have shown that by carefully controlling postannealing temperature
of an ultrathin ZrO2 film prepared by ALD, Zr4+ surface doping could be achieved for Ni-rich layered oxides to accelerate
the charge transfer yet provide sufficient protection. Using single-crystal
LiNi0.6Mn0.2Co0.2O2 as
a model material, we have shown that surface Zr4+ doping
combined with ZrO2 coating can enhance both the cycle performance
and rate capability during high-voltage operation. Surface doping
via controllable postannealing of ALD surface coating layer reveals
an attractive path toward developing stable and Li+-conductive
interfaces for single-crystal battery materials.
The manufacture of 3D mesostructures is receiving rapidly increasing attention, because of the fundamental significance and practical applications across wide-ranging areas. The recently developed approach of buckling-guided assembly allows deterministic formation of complex 3D mesostructures in a broad set of functional materials, with feature sizes spanning nanoscale to centimeter-scale. Previous studies mostly exploited mechanically controlled assembly platforms using elastomer substrates, which limits the capabilities to achieve on-demand local assembly, and to reshape assembled mesostructures into distinct 3D configurations. This work introduces a set of design concepts and assembly strategies to utilize dielectric elastomer actuators as powerful platforms for the electro-mechanically controlled 3D assembly. Capabilities of sequential, local loading with desired strain distributions allow access to precisely tailored 3D mesostructures that can be reshaped into distinct geometries, as demonstrated by experimental and theoretical studies of ∼30 examples. A reconfigurable inductive–capacitive radio-frequency circuit consisting of morphable 3D capacitors serves as an application example.
Lithium-rich
layered oxides have received great attention due to
their high energy density as cathode material. However, the progressive
structural transformation from layered to spinel phase triggered by
transition-metal migration and the irreversible release of lattice
oxygen leads to voltage fade and capacity decay. Here, we report a
Fe, Cl codoped and Co-free Li-rich layered cathode with significantly
improved structural stability. It is revealed that the Fe and Cl codoping
can facilitate the Li-ion diffusion and improve the rate performance
of the materials. Moreover, the calculations show that the structural
stability is enhanced by Fe and Cl codoping. As a result, the Fe and
Cl codopant reduces the irreversible release of lattice oxygen, mitigates
voltage fade, and improves the first-cycle Coulombic efficiency. This
work provides a low-cost, environmentally friendly, practical strategy
for high-performance cathode materials.
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