| Abstract | Litijev titanat ( Li4Ti5O12, LTO) smatra se obećavajućim anodnim materijalom za litij-ionske galvanske članke zbog strukturne i cikličke stabilnosti te male promjene u volumenu kristalne rešetke prilikom interkalacije/deinterkalacije litija. U ovome radu, izrađen je elektrodni anodni materijal u obliku dugmaste elektrode koristeći LTO, PVDF (vezivo) i acetilensko crnilo (vodljivi aditiv) u omjeru 8:1:1 uz otapalo N-metil-2-pirolidon. Provedena su elektrokemijska mjerenja cikličke voltametrije (CV) i kronopotenciometrije te je provedena karakterizacija uzorka LTO prije i poslije procesa pražnjenja pomoću Ramanove spektroskopije. Dobiveni ciklički voltamogram ukazuje na reverzibilnost reakcije prelaska litijevog titanata iz spinelne strukture u strukturu kamene soli tijekom interkalacije litijevih iona. Krivulje punjenja/pražnjenja, dobivene kao rezultat kronopotenciometrije, snimljene su pri C-stopama od 0,1, 0,6, 1,1 i 2,2 C. Kapacitet pražnjenja od 178 mA h g^-1 pri najmanjoj C-stopi (0,1 C) vrlo je blizak teorijskoj vrijednosti 175 mA h g^-1. Povećavanjem C-stope, odnosno jakosti struje u ciklusima punjenja/pražnjenja, smanjuje se kapacitet pražnjenja članka. Također se pri najmanjoj C-stopi uočava plato punjenja/pražnjenja na 1,57 V (punjenje) i 1,56 V (pražnjenje), a teorijska vrijednost potencijala fazne promjene LTO iznosi 1,55 V (prema Li+/Li). Provedbom Ramanove spektroskopije za LTO uzorak prije procesa pražnjenja dobivene su karakteristične vrpce na spektru koje odgovaraju spinelnoj strukturi s Fd3̅m prostornom grupom, a Ramanov spektar za uzorak LTO nakon procesa pražnjenja ukazuje na promjenu faze. |
| Abstract (english) | Lithium titanate ( Li4Ti5O12, LTO) is considered a promising anode material for lithium-ion batteries due to its structural and cyclic stability, as well as minimal changes in crystal lattice volume during lithium intercalation/deintercalation. In this study, an electrode anode material in the form of a button cell electrode was made using LTO, PVDF (binder), and carbon black (to enhance conductivity) in an 8:1:1 ratio with N-methyl-2-pyrrolidone as the solvent. Electrochemical measurements, including cyclic voltammetry (CV) and chronopotentiometry, were conducted, and the LTO sample was characterized before and after the discharge process using Raman spectroscopy. The obtained cyclic voltammogram indicates the reversibilty of the lithium titanate transition from a spinel structure to a rock-salt structure during lithium ion intercalation. Charge/discharge curves, obtained as a result of chronopotentioemtry, were recorded at C-rates of 0,1, 0,6, 1,1 and 2,2 C. The discharge capacity of 178 mA h g^-1 at the lowest C-rate (0,1C) is very close to the theoretical values of 175 mA h g^-1. Increasing the C-rate, i.e., the current intensity during charge/discharge cycles, leads to a decrease in the cell's discharge capacity. Additionally, at the lowest C-rate, a charge/discharge plateau is observed at 1,57 V (charging) and 1,56 V (discharging), while the theoretical potential value for the phase change of LTO is 1,55 V (vs. Li+/Li).
By conducting Raman spectroscopy on the LTO sample before the discharge process, characteristic bands in the spectrum corresponding to a spinel structure with the Fd3̅m space group were obtained. However, the Raman spectrum of the LTO sample after the discharge process indicates a phase change. |
