Core/shell structures for Li-ion capacitors

Abbasi, Rabail Badar (author), Dominko, Robert (mentor)

Lithium ion capacitor (LIC) is an interesting category of energy storage systems, which combines an electrode from a lithium ion battery (LIB) and an electrode from an electrical double layer capacitor (EDLC). The resulting hybrid energy device exhibits rapid charge/discharge capability, long cycle life and high energy density. The widescale usage of LICs is limited however, due to the inherent low concentration of Li-ions present within it. As such, prelithiation technologies have been developed and implemented with varying levels of success. However, all approaches involve an additional measure to be undertaken, which introduces its own challenges. The most optimal solution is to remove the need for prelithiation completely. In this thesis, we propose a method of eliminating the requirement of prelithation by designing a core-shell structure for the anodic active material, with the shell being the material responsible for electrochemical activity, and the core facilitating electronic conductivity. Amorphous titanium dioxide (α-TiO2), a well-researched anode material, is used as the shell, while copper (Cu), a highly conductive metal, is used as a core; Cu@TiO2. Three wet chemistry-based approaches are undertaken to synthesize the anodic material. The best performing anodic material exhibited a specific capacity of ~ 151 mAh g-1, measured in a half cell against Li foil. The anode was then tested in a LIC against cathode with activated carbon as the active material. The resulting LIC showed high specific capacity and stable cycling behaviour up to 1000 cycles at 2.5 A g-1, with a coulombic efficiency of ~ 98.8%. Rate capability tests also showed relatively high stability of the anode material at low to high current rates. The results of this thesis open up potential avenues for further research focused on designing anode structures for LICs.

• Language: English
• Keywords: Lithium-ion capacitor, Core-shell structure, Amorphous titanium dioxide, Copper, Activated carbon, Lithium-ion battery anode, Prelithiation
• Work type: Master's thesis/paper
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2022
• PID: 20.500.12556/RUL-141441
• Publication date in RUL: 29.09.2022

Secondary language

• Language: Slovenian
• Title: Core/shell structures for Li-ion capacitors

Abstract

Litij-ionski kondenzator (LIC) je zanimiva kategorija sistemov za shranjevanje energije, ki združuje elektrodo iz litij-ionske baterije (LIB) in elektrodo iz električnega dvoplastnega kondenzatorja (EDLC). Nastala hibridna energetska naprava ima sposobnost hitrega polnjenja/praznjenja, dolgo življenjsko dobo in visoko energijsko gostoto. Vendar pa je široka uporaba LIC omejena zaradi inherentne nizke koncentracije Li-ionov, ki so prisotni v njih. Kot take so bile razvite in implementirane tehnologije prelitiacije z različnimi stopnjami uspeha. Vendar pa vsi pristopi vključujejo dodatne ukrepe, ki jih je treba izvesti, kar predstavlja svoje izzive. Najbolj optimalna rešitev je popolna odprava potrebe po prelitiaciji. V tem diplomskem delu predlagamo metodo za odpravo zahteve po predlitaciji z oblikovanjem strukture jedro-lupina za anodno aktivni material, pri čemer je lupina material, odgovoren za elektrokemično aktivnost, jedro pa omogoča elektronsko prevodnost. Kot ovoj je uporabljen amorfni titanov dioksid (α-TiO2), dobro raziskan anodni material, medtem ko je baker (Cu), zelo prevodna kovina, uporabljen kot jedro; Cu@TiO2. Za sintezo anodnega materiala so uporabljeni trije pristopi, ki temeljijo na mokri kemiji. Najbolj zmogljiv anodni material je pokazal specifično kapaciteto ~ 151 mAh g-1, merjeno v polovični celici proti Li foliji. Anoda je bila nato testirana v LIC proti katodi z aktivnim ogljem kot aktivnim materialom. Nastali LIC je pokazal visoko specifično zmogljivost in stabilno ciklično obnašanje do 1000 ciklov pri 2,5 A g-1, s kulonsko učinkovitostjo ~ 98,8 %. Preskusi zmogljivosti hitrosti so pokazali tudi razmeroma visoko stabilnost anodnega materiala pri nizkih do visokih stopnjah toka. Rezultati te diplomske naloge odpirajo potencialne poti za nadaljnje raziskave, osredotočene na oblikovanje anodnih struktur za LIC.

• Keywords: Litij-ionski kondenzator, struktura jedra in lupine, amorfni titanov dioksid, baker, aktivno oglje, anoda litij-ionske baterije, prelitiranje