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
3D carbon frameworks are promising hosts to achieve highly reversible lithium (Li) metal anodes, whereas insufficient effects are attributed to their single electron conductivity causing local aggregating of electron/Li+ and uncontrollable Li dendrites. Herein, an ion/electron redistributed 3D flexible host is designed by lithiophilic carbon fiber cloth (CFC) modified with metal-organic framework (MOF)-derived porous carbon sheath with embedded CoP nanoparticles (CoP-C@CFC). Theory calculations demonstrate the strong binding energy and plenty of charge transfer from the reaction between CoP and Li atom are presented, which is beneficial to in situ construct a Li3 P@Co ion/electron conductive interface on every single CoP-C@CFC. Thanks to the high ionic conductive Li3 P and electron-conductive Co nanoparticles, the rapid dispersion of Li+ and obviously reduced local current density can be achieved simultaneously. Furthermore, in situ optical microscopy observations display obvious depression for volume expansion and Li dendrites. As expected, a miraculous average Coulombic efficiency (CE) of 99.96% over 1100 cycles at 3 mA cm-2 and a low overpotential of 11.5 mV with prolonged cycling of over 3200 h at 20% depth of discharge are successfully obtained. Consequently, the CoP-C@CFC-Li||LiFePO4 full cells maintain a capacity retention of 95.8% with high CE of 99.96% over 500 cycles at 2 C and excellent rate capability.
ABSTRACT
Electrode (including cathode and anode) /electrolyte interfaces play a vital role in determining battery performance. Especially, high-voltage lithium metal batteries (HVLMBs) with the Ni-rich layered oxide ternary cathode (NCM) can be considered a promising energy storage technology due to their outstanding energy density. However, it is still extremely challenging to address the unstable electrode/electrolyte interface and structural collapse of polycrystalline NCM at high voltage, greatly restraining its practical applications. In this work, a novel electrolyte additive, tris(2-cyanoethyl) borate (TCEB), has been used to construct the robust nitrogen (N) and boron (B)-rich protective films on single-crystal LiNi0.6Co0.1Mn0.3O2 (SNCM) cathode and lithium metal anode surfaces, which could effectively mitigate parasitic reactions against electrolyte corrosion and retain the structural integrity of electrode. Remarkably, the SNCM||Li metal cell using TCEB-containing electrolyte maintains unprecedentedly superb capacity retention of 80% after 100 cycles at an ultrahigh charging voltage of 4.7 V (versus Li/Li+). This finding provides a valuable reference to construct a stable electrode/electrolyte interface for the HVLMBs with achieving high-energy density.
ABSTRACT
Lithium (Li) metal is widely considered the most promising anode material because of its ultrahigh specific energy. However, the obvious volume change and uncontrollable dendrite growth hinder its commercial applications. Herein, we designed a 3D scaffold of Cu3P nanoarray-modified Cu foam via in situ conversion (3D MIECS). Uniform lithiophilic Cu3P nanoarrays were in situ grown inside the Cu foam (Cu3P NA@CF) that presented a high specific surface area and very low nucleation overpotential. Specifically, the lithiated Cu3P nanoarrays possess the features of mixed ion/electron conductivity and structural stability responsible for uniform Li deposition in the whole three-dimensional space of the metal skeleton, showing scarcely any volume expansion or structural collapse during the continuous Li plating/stripping process. Therefore, the modified Cu foam host achieves dendrite-free cycling over 600 cycles at a current density of 3 mA cm-2 with a coulombic efficiency (CE) of 99.1%. A 3D MIECS-Li||LiFePO4 full cell holds a capacity retention of 80% with a stable CE of 99.63% over 1000 cycles at 3 C.
