Laser modification and characterization of Li-Mn-O thin film cathodes for lithium-ion batteries

Abstract

The development of future battery systems is mainly focused on powerful rechargeable lithium-ion batteries. To satisfy this demand, current studies are focused on cathodes based on nano-composite materials which lead to an increase in power density of the LIB primarily due to large electrochemically active surface areas. Electrode materials made of lithium manganese oxides (Li-Mn-O) are assumed to replace commonly used cathode materials like LiCoO 2 due to less toxicity and lower costs. Thin films in the Li-Mn-O system were synthesized by non-reactive r.f. magnetron sputtering of a LiMn 2 O 4 target on silicon and stainless steel substrates. In order to enhance power density and cycle stability of the cathode material, direct laser structuring methods were investigated using a laser system operating at a wavelength of 248 nm. Therefore, high aspect ratio micro-structures were formed on the thin films. Laser annealing processes were investigated in order to achieve an appropriate crystalline phase for unstructured and structured thin films as well as for an increase in energy density and control of grain size. Laser annealing was realized via a high power diode laser system. The effects of post-thermal treatment on the thin films were studied with Raman spectroscopy, X-ray diffraction and scanning electron microscopy. The formation of electrochemically active and inactive phases was discussed. Surface chemistry was investigated via X-ray photoelectron spectroscopy. Interaction between UV-laser radiation and the thin film material was analyzed through ablation experiments. Finally, to investigate the electrochemical properties, the manufactured thin film cathodes were cycled against a lithium anode. The formation of a solid electrolyte interphase on the cathode side was discussed.

Comparative studies of laser annealing technique and furnace annealing by X-ray diffraction and Raman analysis of lithium manganese oxide thin films for lithium-ion batteries

“…The film thickness was determined with a surface profilometer (Tencor P-10) and counted 2-3.3 μm depending on the position of the substrate on the plate. The density of an as-deposited Li-Mn-O thin film with a thickness of about~67 nm was measured to be about 4 g/cm 3 via X-ray reflectivity [21] and was considered for calculation of the active mass for electrochemical cycling of laser annealed thin films assuming that no mass losses occur [30] during the annealing process at temperatures of T = 680°C.…”

“…Other in-situ studies were focused on reversible and irreversible transformations of stoichiometric LiMn 2 O 4 in air [16] or on in-situ X-ray diffraction (XRD) studies during lithium deintercalation from the spinel host structure [17]. rf magnetron sputtering is one promising method for synthesizing thin lithium manganese oxide films which have model character [18][19][20][21] and to study clearly their structural behavior due to the absence of carbon and binder as can be found in tape cast electrodes. Rapid laser annealing is one possible technique for crystallization of thin cathodes such as LiCoO 2 [22][23][24] or Li-Mn-O [20,21].…”

“…rf magnetron sputtering is one promising method for synthesizing thin lithium manganese oxide films which have model character [18][19][20][21] and to study clearly their structural behavior due to the absence of carbon and binder as can be found in tape cast electrodes. Rapid laser annealing is one possible technique for crystallization of thin cathodes such as LiCoO 2 [22][23][24] or Li-Mn-O [20,21]. Besides that, other rapid annealing processes for Li-Mn-O thin films have already been applied in the past by using halogen lamps for so-called rapid thermal annealing [25][26][27][28][29].…”

Laser Materials Processing for Energy Storage Applications

“…A rather new application field for laser material processing is the development of 3D structures in lithium-ion batteries based on nano-scaled materials and thin films [71][72][73][74][75][76][77][78][79][80][81][82]. For this purpose, laser annealing and laser structuring of thin film electrodes made of LiCoO2, SnO2 and LiMn2O4 were recently investigated.…”

Surface micro-structuring of intercalation cathode materials for lithium-ion batteries: a study of laser-assisted cone formation

“…Unfortunately, this approach is unfeasible for each type of electrode system, in particular for thick film electrodes [9][10][11][12][13]. Therefore, laser direct structuring of the active electrode material has been developed for thin film electrodes made of LiCoO 2 , LiMn 2 O 4 , SnO 2 or fluorine doped SnO 2 (FTO) [14][15][16][17][18][19][20][21][22][23]. In a very recent approach, it was shown that laser-structuring can be applied for LiCoO 2 , LiMn 2 O 4 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 and silicon composite electrodes with film thicknesses of 50 to 100 µm [24][25][26][27][28].…”