Photo Rechargeable Li‐Ion Batteries Using Nanorod Heterostructure Electrodes

Abstract

sectors, such as in high energy density demand portable devices, solar vehicles, solar impulse planes, satellites, etc. [4][5][6] This concept was initially proposed by Hodes et al. in 1976, where they have shown a three-electrode system comprised of cadmium selenide, sulfur, and silver sulfide (CdSe/S/Ag 2 S). [7] In this system, one of the components acted as photoelectrode while the others acted as the components for the energy storage. Such efforts have continued with other threeelectrode systems, such as n-cadmium selenide telluride/cesium sulfide/tin sulfide [8] and hybrid titania (TiO 2 ) poly(3,4ethylenedioxythiophene) as photo anode and a perchlorate (ClO 4 − )-doped polypyrroles counter electrode. This approach was improved by using a two-electrode system with a hybrid mixture of lithium iron phosphate (LFP) nanocrystals and N719 dye as the active photo-electrode assembled with lithium metal as counter electrode. [9] The N719 dye acts as photon absorber and lithium iron phosphate (LFP) as cathode. In this system, during the photocharging, the electrons produced during the photo-excitation of the dye generate holes in the valance band which repel Li-ions from their intercalated state. The continuous photo-conversion drives the battery to reach back in the charged state (in 30 h) with a 200 W solar spectrum (simulator). [9] It has low photo conversion efficiency and it was observed that soon after the first cycle, the charge capacity started fading due to dissolution of the organic dye in to the organic electrolyte.A different approach was attempted later, where a polycrystalline metal halide based 2D perovskite was used as a photoactive electrode ((C 6 H 9 C 2 H 4 NH 3 ) 2 PbI 4 ) that could provide both energy storage (battery functionality) and photo charging (photovoltaic functionality). [10] This perovskite system provided a low photo conversion efficiency of ≈0.034%. Furthermore, the system suffered from various other challenges such as the conversion reaction between lithium and perovskite generating lead (Pb), where it can further alloy with lithium causing a large volume expansion.More recently, it was reported that an organic molecule based photo-electrode could also be used for photo charging. [11] Absorption of light of a desired wavelength by lithiatedtetrakislawsone electrodes generates electron-hole pairs, and the holes oxidize the lithiated-tetrakislawsone to tetrakislawsone while the generated electrons flow from the tetrakislawsone New ways of directly using solar energy to charge electrochemical energy storage devices such as batteries would lead to exciting developments in energy technologies. Here, a two-electrode photo rechargeable Li-ion battery is demonstrated using nanorod of type II semiconductor heterostructures with in-plane domains of crystalline MoS 2 and amorphous MoO x . The staggered energy band alignment of MoS 2 and MoO x limits the electron holes recombination and causes holes to be retained in the Li intercalated MoS 2 electrode. The holes generated in the MoS 2 pushes...

Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future

“…Meanwhile, MoS 2 matches MoO x energy level, but the conduction band position of MoO x is negative than that of MoS 2 , hence the optical efficiency only reaches 0.05% (Figure 4d). [ 67 ] Boruah et al also chose MoS 2 as the photoactive cathode material for the zinc ion battery, in which ZnO was designed as the electron transport and hole blocking layer for the photoelectrode material ( Figure a–c). [ 135 ] The photoconversion efficiencies of the photocathode reaches 0.2% and The capacity increased by 38% under illumination.…”

“…Semiconductors used as photoelectrodes include metal oxides, IV, III‐V compounds, and metallic chalcogenides. [ 67,68 ] Metal oxide (TiO 2 , Fe 2 O 3, WO 3, and Co 3 O 4 , Etc.) wide bandgap semiconductors have been intensively researched.…”

“…[ 72 ] Kumar et al adopted the staggered band arrangement of MoS 2 and MoO x to limit electron–hole recombination and lead to hole retention in Li‐intercalated MoS 2 electrodes (Figure 4d). [ 67 ] The holes generated in MoS 2 push the intercalated Li + , thereby charging the LiB.…”

“…[96,133,134] For instance, Kumar et al proposed such a novel heterostructure of MoS 2 /MoO x nanorod (NR) as dual-function electrodes for photo rechargeable LiBs. [67] In the MoS 2 /MoO x NR structure, MoS 2 is covalently connected with the MoO x domain, which can provide high interlayer area for Li + . Meanwhile, MoS 2 matches MoO x energy level, but the conduction band position of MoO x is negative than that of MoS 2 , hence the optical efficiency only reaches 0.05% (Figure 4d).…”

“…d) schematic of electron-hole separation in the heterostructure MoS 2 /MoO x NR; Energy efficiency; Use stored electrochemical energy with or without light. Reproduced with permission [67]. Copyright 2021, Wiley-VCH.…”