74 research outputs found
Nanoscale Voltage Enhancement at Cathode Interfaces in Li-ion Batteries
Interfaces are ubiquitous in Li-ion battery electrodes, occurring across
compositional gradients, regions of multiphase intergrowths, and between
electrodes and solid electrolyte interphases or protective coatings. However,
the impact of these interfaces on Li energetics remains largely unknown. In
this work, we calculated Li intercalation-site energetics across cathode
interfaces and demonstrated the physics governing these energetics on both
sides of the interface. We studied the olivine/olivine-structured
LixFePO4/LixMPO4 (x=0 and 1, M=Co, Ti, Mn) and layered/layered-structured
LiNiO2/TiO2 interfaces to explore different material structures and transition
metal elements. We found that across an interface from a high- to low-voltage
material the Li voltage remains constant in the high-voltage material and
decays approximately linearly in the low-voltage region, approaching the Li
voltage of the low-voltage material. This effect ranges from 0.5-9nm depending
on the interfacial dipole screening. This effect provides a mechanism for a
high-voltage material at an interface to significantly enhance the Li
intercalation voltage in a low-voltage material over nanometer scale. We showed
that this voltage enhancement is governed by a combination of electron transfer
(from low- to high-voltage regions), strain and interfacial dipole screening.
We explored the implications of this voltage enhancement for a novel
heterostructured-cathode design and redox pseudocapacitors
A Spin-dependent Machine Learning Framework for Transition Metal Oxide Battery Cathode Materials
Owing to the trade-off between the accuracy and efficiency,
machine-learning-potentials (MLPs) have been widely applied in the battery
materials science, enabling atomic-level dynamics description for various
critical processes. However, the challenge arises when dealing with complex
transition metal (TM) oxide cathode materials, as multiple possibilities of
d-orbital electrons localization often lead to convergence to different spin
states (or equivalently local minimums with respect to the spin configurations)
after ab initio self-consistent-field calculations, which causes a significant
obstacle for training MLPs of cathode materials. In this work, we introduce a
solution by incorporating an additional feature - atomic spins - into the
descriptor, based on the pristine deep potential (DP) model, to address the
above issue by distinguishing different spin states of TM ions. We demonstrate
that our proposed scheme provides accurate descriptions for the potential
energies of a variety of representative cathode materials, including the
traditional LiTMO (TM=Ni, Co, Mn, =0.5 and 1.0), Li-Ni anti-sites in
LiNiO (=0.5 and 1.0), cobalt-free high-nickel
LiNiMnO (=1.5 and 0.5), and even a ternary cathode
material LiNiCoMnO (=1.0 and 0.67). We
highlight that our approach allows the utilization of all ab initio results as
a training dataset, regardless of the system being in a spin ground state or
not. Overall, our proposed approach paves the way for efficiently training MLPs
for complex TM oxide cathode materials
Synthesis of dominant plastic microfibre prevalence and pollution control feasibility in Chinese freshwater environments
Microplastic pollution of freshwaters is known to be a great concern in China and these pollutants can be discharged into the coastal environment through fluvial processes, posing threats to the global marine ecosystem. This paper reviewed the literature measuring microplastic pollution in the Chinese freshwater environment and found that microfibres dominate other plastic morphologies in more than 65% of samples collected in surface water, sediments and effluents of wastewater treatment plants and domestic sewers. Current potential sources of microfibre pollution are identified including fishery activities, laundry sewage, and waste textiles according to previous research. Recommendations are offered using the circular economy management framework, such as textile waste reuse and recycling systems in China, for improving current control measures for microplastics in freshwaters
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