THE IMPACT OF EXFOLIATED-GRAPHENE (EG) AS AN ADDITIONAL CONDUCTIVE MATERIAL ON LINI0.5MN1.5O4 (LNMO) CATHODE MATERIAL OF LITIUM-ION BATTERIES

• Main Author: Nadia Suryadi, Putri
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/70494
• Institution: Institut Teknologi Bandung

LiNi0,5Mn1,5O4 (LNMO) is a promising cathode material for fast charging in lithium-ion battery technology. LNMO structure contains a three-dimensional lithium-ion diffusion path, thereby accelerating the movement of litium ions during the intercalation and deintercalation processes. Then, LNMO has an energy density of up to 650 Wh kg-1 and a high working voltage (4.7 V), so it is potential to be applied to electric vehicles. In addition, LNMO does not contain cobalt, which is harmless to the environment and superior in terms of economy. However, LNMO has several drawbacks, namely Jahn-Teller distortion, which makes the crystal structure of LNMO unstable, and electrolyte decomposition at high voltage causes the formation of a thick cathode electrolyte interphase (CEI) which can reduce conductivity. The addition of material to LNMO is an effective strategy to protect particles from electrolyte attack. However, the material must be conductive to facilitate the charge transfer. This research reports on LNMO synthesis using the coprecipitation method and studies the effect of adding graphene-based materials, such as exfoliated-graphene (EG) with varying mass percentages, to improve the electrochemical performance of LNMO cathode materials in lithium-ion battery applications. The results of X-Ray Diffraction (XRD) characterization show the XRD pattern of LNMO material with a crystal structure of Fd3?m. The impurity phases are detected at 37.4° and 43.7° of LixNi1-xO; meanwhile, Na0.7MnO2.05 is at 37.4°. Then, the comparison of the XRD patterns between LNMO and LNMO materials that have been mixed with EG (LNMO-EG) has a difference of 26.5°. The intensity at the peak of 26.5o is clearly visible with the addition of the mass percentage of EG material which confirms the existence of EG in the modified LNMO material. The particle morphology of the LNMO and LNMO-EG materials has the same shape: truncated octahedral and 1-2 µm in size. A truncated octahedral morphology which indicates the presence of three planes, such as (111) and (100), supports the LNMO material to produce an excellent electrochemical performance that is because each plane has a role in stability (111) and ionic conductivity (100). The existence of EG is detected as graphene sheets which connecting each LNMO particles. Then, in the LNMO-EG, it can be seen that there is EG material in the form of sheets that connect the LNMO particles. The strategy can improve the electronic conductivity and protect the LNMO particles from electrolyte attack. Electrochemical Impedance Spectroscopy (EIS) test results confirmed the lower Rct value due to the addition of EG material. Based on the charge-discharge test in the first cycle at 0.1 C, it confirmed that the crystal structure of the LNMO formed by Fd3?m was due to the redox reaction of Mn3+/Mn4+ around 4.0 V. On other hand, the addition of EG with a low percentage was considered less effective, but when EG is too high, it will inhibit the movement of Li+ ions. This was confirmed through the electrochemical performance of the LNMO material in the rate capability and cycle stability tests. According to the test results, LNMO 5% EG has optimum performance with a specific discharge capacity of 93.67 mAh g-1 at 5 C and capacity retention of 95.22% after 100 cycles at 1 C.