Structural (amorphous vs. crystalline) analysis of 250 oC and 300 oC calcined electrode plates. a) XRD patterns showing characteristic peaks attributed to. SEM images of control V2O5 electrode plate on Ni foil current collector: (a) surface (b) cross-section (c) cross-section at high magnification. The specific gravimetric capacity of 250 oC calcined plate is slightly higher than that of 300 oC calcined plate, because it is known that amorphous materials undergo a redox reaction not only on the surface but also in the bulk. Our HV plates perform better electrochemical properties than previous V2O5/CNT electrodes in Table 2.42-45.
Intriguingly, the higher capacity of the plate calcined at 250 oC maintains stable cyclability over 2000 charge/discharge cycles at 2.0 A g−1 in Figure. electrode plate (=2.0 mg cm−2) appeared negligibly different from that of the control V2O5 (=2.3 mg cm−2), showing that the lower weight of the electrode plate calcined at 250 oC is mainly due to the removal of the heavy Ni foil current collector (=23 mg cm−2). As a result, the electrode plate calcined at 250 oC showed the significant improvement in the specific gravimetric capacitance expressed as capacitance per weight of electrode plate (=F electrode−1) (e.g. 134 F gel electrode−1 at a scan rate of 1 mV s− 1) than the control V2O5 electrode plate (=29 F gel electrode−1. ) over a wide range of scan speeds in Fig.
The aforementioned substantial improvement in the redox reaction kinetics enabled by the PAN/MWCNT heteronanomat-mediated 3D bicontinuous electron/ion conduction pathways and the specific gravimetric/volumetric capacitance enabled by the removal of heavy Ni-foil current collectors and also the close packing of V2O5 materials from the electrode plate calcined at 250 oC were further emphasized by analysis of the Ragone plot, in which the cell weight was determined by considering only the weight of the electrode plate. 9f verified that the electrode plate calcined at 250 oC showed the remarkable increase in the (electrode plate based) specific gravimetric energy (=Wh kgelectrode−1)/power (=W kgelectrode−1) densities, well beyond those accessible with the control V2O5 electrode plate (manufactured via a conventional slurry casting method), highlighting its potential benefits as an exceptional high energy/high power density energy source. 9a–e of the 250 oC calcined electrode plate compared to the control V2O5 electrode plate was further confirmed by the lower cell impedance in Fig.
Notably, the electrode plates calcined at 250 oC and 300 oC showed significantly lower bulk resistance in the highest frequency region than the control V2O5 electrode plate, demonstrating the easier ion transport due to their well-developed 3D continuous ion conduction channels.
Discussion
Lithium ion battery – firstly proposed full cell toward high energy density
To quantitatively elucidate the effect of the MWCNT content in the ROM powders, conventional OLO cathode (ROM powder/carbon black additive/polyvinylidene fluoride (PVdF) binder w/w/w)) was prepared using a typical slurry casting method. The (in-plane) electronic conductivity of the OLO cathodes increased with MWCNT content in Fig. The discharge rate capability of the OLO cathodes was investigated using a coin half-cell (OLO cathode/PE separator/lithium metal anode).
A conceptual representation depicting the structural uniqueness of the ROM nanomat cathode, along with a photograph showing the mechanical flexibility, is shown in Fig. The composition ratio of ROM nanomat cathode is estimated to be OLO/MWCNT/(PAN/PVP w/w/ w) from TGA measurement in Fig. 16. The highly interconnected electronic channels of ROM nanomat cathode were confirmed by comparing its electronic conductivity with the conventional OLO cathode.
13f shows that the nanomat ROM cathode (=7.55 S cm−1) exhibited a significantly higher electronic conductivity than the conventional OLO cathode (=0.17 S cm−1), which was attributed to the combined effect of the highly interconnected MWCNT networks and (rambutan-shaped) ROM powders. In addition to the superior electronic conductivity, the nanomat ROM cathode exhibited better electrolyte wetting ability than the conventional OLO cathode in Fig. 17b due to the well-developed porous structure. During the repeated bending cycles, the electronic resistance of the nanomat ROM cathode remained almost unchanged, in contrast to the conventional OLO cathode, which showed a gradual increase in the electronic resistance in Fig.
After the bending test, a slight increase in cell resistance was observed in the ROM nanomat cathode compared to the conventional OLO cathode, showing significant increase in cell resistance in Fig. The electrochemical performance of the nanomat ROM cathode was investigated using a coin cell with a PE spacer and Lithium anode. A comparison of the total surface area between the cathodes is shown in Fig. 13h, revealing the lowest surface area of the ROM nanomat cathode.
3D bicontinuous ion/electron transport channels, with the removal of the heavy Al foil current collector, contributed to improved discharge capacities of the nanosized ROM cathode. Another characteristic performance of the nanosized ROM cathode was the cycling performance (expressed as mA h gCathode−1 . ) at a charge/discharge current density of 1.0 C/1.0 C under a voltage range of 2.0–4.7 V. The cells are dissocd. obtained after cycles to elucidate this superior cycling performance of the nanosized ROM cathode.
2-3. Nanomat TLS anode
The fully nanomatte full cell showed significantly higher performance than the conventional full cell, highlighting the beneficial effect of the metal-free current collector architecture in the fully nanomatte full cell. Furthermore, the fully nanomatte full cell showed better discharge rate performance at a charge current density of 0.1 C than the conventional full cell in Fig. 25d, revealing the beneficial effect of the 3D-bicontinuous ion/electron transport pathways on the Faradaic reaction kinetics.
The cycling performance (expressed as mAh gCell−1) of the full nanometer cell was investigated at a charge/discharge current density of 0.5 C/0.5 C in Fig. performance (capacity = 46.9 mAh gCell−1, capacity retention = 76% after 100 cycles). To further elucidate the superior electrochemical performance of the full cell with nanoparticles, the ICP-MS analysis in Fig.
26 was performed, which showed that the amount of metallic Mn deposited on the nanomat TLS anode (=60 ppm) was significantly lower than that on the conventional Si anode (=326 ppm), which was highly contaminated with Mn byproducts. To highlight the superior electrochemical performance of the all-nanomat full cell, the gravimetric energy density (= W h kgCell−1. ) was compared with the values (expressed as W h kgSi anode−1) for previously reported (Si anode-containing ) whole cells. The all-nanosized whole cell showed a higher gravimetric energy density (479 W h kgCell−1, corresponding to a volumetric energy density of 707 W h LCell−1) in the table than the previous results despite the unfair comparison (i.e. W h kgCell−1). −1 versus W h kgSi anode−1).
Comparison of whole cell gravimetric capacity between whole nanometer cell and previous studies. Furthermore, this energy density is significantly higher than the target value (350 Wh kgCell−1)61,62 for long-range EV batteries announced by the 2020 commercialization project of the US Advanced Battery Consortium (USABC ). 25f shows that the full nanometer cell has maintained stable charge/discharge profiles even after 100 bending cycles (5 mm bending diameter).
This unprecedented advancement in electrochemical performance (rate capability, cycling performance, and energy density) with excellent mechanical flexibility underscores the extraordinary features of the all-nanomat cell structure, suggesting its potential as a competent platform technology for high-performance and flexible rechargeable batteries. I demonstrated the full nanomat LIB cells based on the 1D building block - polymeric nanofiber and CNT interwoven heteronanomat skeletons as a facile and efficient approach to enable ultra-high energy density with mechanical flexibility. The full nanomat (OLO/Si) cell provided an exceptional improvement in electrochemical performance, particularly cell-based gravimetric/volumetric energy density = 479 W h kgCell−1.
Summary
Supporting information
The electrochemical performance of the heteromatous V2O5 electrode sheet was characterized using a symmetric bag-type cell in which the V2O5 electrode sheet was assembled with a polypropylene (PP) separator (Celgard 3501) and 2 M KCl aqueous electrolyte.
4-2. Experimental Methods (All nanomat full cell)
Fabrication of Nanomat ROM Cathodes
Fabrication of Nanomat TLS Anodes
Structural/Physicochemical Characterization of the Nanomat Electrodes
Electrochemical Characterization of Nanomat Electrodes and All-Nanomat Full Cells
