ABSTRACT
"Polymer-in-ceramic" (PIC) electrolytes are widely investigated for all-solid-state batteries (ASSBs) due to their good thermal stability and mechanical performance. However, achieving fast and diversified lithium-ion transport inside the PIC electrolyte and uniform Li+ deposition at the electrolyte/Li anode interface simultaneously remains a challenge. Besides, the effect of ceramic particle size on Li+ transport and Li anodic compatibility is still unclear, which is essential for revealing the enhanced mechanism of the performance for PIC electrolytes. Herein, PIC with moderate ceramic size and contents are prepared and studied to strike a balance between ionic conductivity and anodic compatibility. Through moderate filler-filler interfacial impedance and appropriate surface roughness, a particle size of 17 µm is optimized to facilitate homogeneous Li+ flux on anode and enhance Li+ conductivity of the electrolyte. The PIC electrolyte with ceramic particle size of 17 µm achieves a high lithium ion transference number (0.74) and an ionic conductivity of 4.11 × 10-4 S cm-1 at 60 °C. The Li/PIC/Li symmetric cell can stably cycle for 2800 h at 0.2 mA cm-2 with 0.2 mAh cm-2. Additionally, the Li/PIC/LiFePO4 cell also delivers a superior cycling performance at 0.5C, a high capacity retention of 93.28% after 100 cycles and 83.17% after 200 cycles, respectively.
ABSTRACT
As an attractive cathode candidate for sodium-ion batteries, P2-type Na2/3Ni1/3Mn2/3O2 is famous for its high stability in humid air, attractive capacity, and high operating voltage. However, the low Na+ transport kinetics, oxygen-redox reactions, and irreversible structural evolution at high-voltage areas hinder its practical application. Herein, a comprehensive study of a microbar P2-type Ni2/3Ni1/4Mg1/12Mn2/3O2 material with {010} facets is presented, which exhibits high reversibility of structural evolution and anionic redox activity, leading to outstanding rate capability and cyclability. The notable rate performance (53 mA h g-1 at 20 C, 2.0-4.3 V) contributed to the high exposure of {010} facets via controlling the growth orientation of the precursor, which is certified by density functional theory calculation and lattice structural analysis. Mg substitution strengthens the reversibility of anionic oxygen redox and structural evolution in high-voltage areas that was confirmed by the in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy tests, leading to outstanding cyclic reversibility (68.9% after 1000 cycles at 5 C) and slowing down the voltage fading. This work provides new insights into constructing electrochemically active planes combined with heteroatom substitution to improve the Na+ transport kinetics and structural stability of layered oxide cathodes for sodium storage.
ABSTRACT
Nowadays fast charging has become an important characteristic of lithium-ion batteries (LIBs), so is of great significance to study the fast charging of LIBs. However, previous research of fast charging has focused more on high energy density LIBs, due to the growing demand for electric vehicles. Herein, the fast-charging properties under ambient temperature and high temperature for (60 mAh LiCoO2/graphite batteries) micro-LIBs are firstly investigated. The electrochemical test results reveal that this kind of battery possesses 4C fast-charging capability. Further increase in charging rate will accelerate battery capacity decay without reducing charging time. Although high temperature increases the fast-charging capacity and shortens the fast-charging time to 10 min at 6C under 65 °C, increase of side reactions resulted from high temperature also exacerbates the performance of battery. Post-mortem analysis further demonstrates the structural changes of cathode and anode materials, residual lithium deposits, peeling of graphite and the incrassation of the solid electrolyte interphase (SEI), especially under high temperature, which lead to fast -charging performance degradation. This work reveals the possible causes of micro battery performance deterioration during fast charging under ambient and high temperature and provides some reference for designing micro-LIBs with fast -charging properties.
ABSTRACT
Downsizing the cell size of honeycomb monoliths to nanoscale would offer high freedom of nanostructure design beyond their capability for broad applications in different fields. However, the microminiaturization of honeycomb monoliths remains a challenge. Here, we report the fabrication of microminiaturized honeycomb monoliths-honeycomb alumina nanoscaffold-and thus as a robust nanostructuring platform to assemble active materials for micro-supercapacitors. The representative honeycomb alumina nanoscaffold with hexagonal cell arrangement and 400 nm inter-cell spacing has an ultrathin but stiff nanoscaffold with only 16 ± 2 nm cell-wall-thickness, resulting in a cell density of 4.65 × 109 cells per square inch, a surface area enhancement factor of 240, and a relative density of 0.0784. These features allow nanoelectrodes based on honeycomb alumina nanoscaffold synergizing both effective ion migration and ample electroactive surface area within limited footprint. A micro-supercapacitor is finally constructed and exhibits record high performance, suggesting the feasibility of the current design for energy storage devices.
