Binder-Free Anodes for Potassium-ion Batteries Comprising Antimony Nanoparticles on Carbon Nanotubes Obtained Using Electrophoretic Deposition.

Antimony has a high theoretical capacity and suitable alloying/dealloying potentials to make it a future anode for potassium-ion batteries (PIBs); however, substantial volumetric changes, severe pulverization, and active mass delamination from the Cu foil during potassiation/depotassiation need to be overcome. Herein, we present the use of electrophoretic deposition (EPD) to fabricate binder-free electrodes consisting of Sb nanoparticles (NPs) embedded in interconnected multiwalled carbon nanotubes (MWCNTs). The anode architecture allows volume changes to be accommodated and prevents Sb delamination within the binder-free electrodes. The Sb mass ratio of the Sb/CNT nanocomposites was varied, with the optimized Sb/CNT nanocomposite delivering a high reversible capacity of 341.30 mA h g-1 (∼90% of the initial charge capacity) after 300 cycles at C/5 and 185.69 mA h g-1 after 300 cycles at 1C. Postcycling investigations reveal that the stable performance is due to the unique Sb/CNT nanocomposite structure, which can be retained over extended cycling, protecting Sb NPs from volume changes and retaining the integrity of the electrode. Our findings not only suggest a facile fabrication method for high-performance alloy-based anodes in PIBs but also encourage the development of alloying-based anodes for next-generation PIBs.

Binder-free germanium nanoparticle decorated multi-wall carbon nanotube anodes prepared via two-step electrophoretic deposition for high capacity Li-ion batteries.

Germanium (Ge) has a high theoretical specific capacity (1384 mA h g-1) and fast lithium-ion diffusivity, which makes it an attractive anode material for lithium-ion batteries (LIBs). However, large volume changes during lithiation can lead to poor capacity retention and rate capability. Here, electrophoretic deposition (EPD) is used as a facile strategy to prepare Ge nanoparticle carbon-nanotube (Ge/CNT) electrodes. The Ge and CNT mass ratio in the Ge/CNT nanocomposites can be controlled by varying the deposition time, voltage, and concentration of the Ge NP dispersion in the EPD process. The optimized Ge/CNT nanocomposite exhibited long-term cyclic stability, with a capacity of 819 mA h g-1 after 1000 cycles at C/5 and a reversible capacity of 686 mA h g-1 after 350 cycles (with a minuscule capacity loss of 0.07% per cycle) at 1C. The Ge/CNT nanocomposite electrodes delivered dramatically improved cycling stability compared to control Ge nanoparticles. This can be attributed to the synergistic effects of implanting Ge into a 3D interconnected CNT network which acts as a buffer layer to accommodate the volume expansion of Ge NPs during lithiation/delithiation, limiting cracking and/or crumbling, to retain the integrity of the Ge/CNT nanocomposite electrodes.

Solution processable Si/Ge heterostructure NWs enabling anode mass reduction for practical full-cell Li-ion batteries.

Here, we report the solution phase synthesis of axial heterostructure Si and Ge (hSG) nanowires (NWs). The NWs were grown in a high boiling point solvent from a low-cost Sn powder to achieve a powder form product which represents an attractive route from lab-scale to commercial application. Slurry processed anodes of the NWs were investigated in half-cell (versus Li-foil) and full-cell (versus NMC811) configurations of a lithium ion battery (LIB). The hSG NW anodes yielded capacities of 1040 mA h g-1 after 150 cycles which corresponds to a 2.8 times increase compared to a standard graphite (372 mA h g-1) anode. Given the impressive specific and areal capacities of the hSG anodes, a full-cell test against a high areal capacity NMC811 cathode was examined. In full-cell configuration, use of the hSG anode resulted in a massive anode mass reduction of 50.7% compared to a standard graphite anode. The structural evolution of the hSG NW anodes into an alloyed SiGe porous mesh network was also investigated using STEM, EDX and Raman spectroscopy as a function of cycle number to fully elucidate the lithiation/delithiation mechanism of the promising anode material.

Cu Current Collector with Binder-Free Lithiophilic Nanowire Coating for High Energy Density Lithium Metal Batteries.

Despite significant efforts to fabricate high energy density (ED) lithium (Li) metal anodes, problems such as dendrite formation and the need for excess Li (leading to low N/P ratios) have hampered Li metal battery (LMB) development. Here, the use of germanium (Ge) nanowires (NWs) directly grown on copper (Cu) substrates (Cu-Ge) to induce lithiophilicity and subsequently guide Li ions for uniform Li metal deposition/stripping during electrochemical cycling is reported. The NW morphology along with the formation of the Li15 Ge4 phase promotes uniform Li-ion flux and fast charge kinetic, resulting in the Cu-Ge substrate demonstrating low nucleation overpotentials of 10 mV (four times lower than planar Cu) and high Columbic efficiency (CE) efficiency during Li plating/stripping. Within a full-cell configuration, the Cu-Ge@Li - NMC cell delivered a 63.6% weight reduction at the anode level compared to a standard graphite-based anode, with impressive capacity retention and average CE of over 86.5% and 99.2% respectively. The Cu-Ge anodes are also paired with high specific capacity sulfur (S) cathodes, further demonstrating the benefits of developing surface-modified lithiophilic Cu current collectors, which can easily be integrated at the industrial scale.

Lithiophilic Nanowire Guided Li Deposition in Li Metal Batteries.

Lithium (Li) metal batteries (LMBs) provide superior energy densities far beyond current Li-ion batteries (LIBs) but practical applications are hindered by uncontrolled dendrite formation and the build-up of dead Li in "hostless" Li metal anodes. To circumvent these issues, we created a 3D framework of a carbon paper (CP) substrate decorated with lithiophilic nanowires (silicon (Si), germanium (Ge), and SiGe alloy NWs) that provides a robust host for efficient stripping/plating of Li metal. The lithiophilic Li22 Si5 , Li22 (Si0.5 Ge0.5 )5, and Li22 Ge5 formed during rapid Li melt infiltration prevented the formation of dead Li and dendrites. Li22 Ge5 /Li covered CP hosts delivered the best performance, with the lowest overpotentials of 40 mV (three times lower than pristine Li) when cycled at 1 mA cm-2 /1 mAh cm-2 for 1000 h and at 3 mA cm-2 /3 mAh cm-2 for 500 h. Ex situ analysis confirmed the ability of the lithiophilic Li22 Ge5 decorated samples to facilitate uniform Li deposition. When paired with sulfur, LiFePO4, and NMC811 cathodes, the CP-LiGe/Li anodes delivered 200 cycles with 82%, 93%, and 90% capacity retention, respectively. The discovery of the highly stable, lithiophilic NW decorated CP hosts is a promising route toward stable cycling LMBs and provides a new design motif for hosted Li metal anodes.