Rechargeable lithium-ion batteries (LIBs) are widely used in cell phones, laptops, and electric vehicles. A LIB cell consists of three main parts: anode, cathode, and electrolyte. The battery type is named after its cathode materials, such as Li(Ni,Co,Mn)O₂ (NCM) battery, which is composed of lithium, nickel, cobalt, and manganese. NCM has been the most used cathode for LIB industry due to its considerable capacity and energy density. NCM has different compositions, such as LiNi_0.5Co_0.2Mn_0.3O₂ (NCM 523), LiNi_0.6Co_0.2Mn_0.2O₂ (NCM 622), and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM 811). With the applied NCM 622 and NCM 811 cathodes in coin cells in this research, the goal is to test their battery performance and to understand the composition effects on their electrochemical properties. From the charge-discharge and cycling performance measurements, NCM 811 shows higher capacity and better stability as compared to NCM 622. X-ray diffraction and electron microscopes are employed to examine the phase, morphology, crystal structure, and microstructure and to explore the relationship between composition, structure and battery performance. The goal is to have safe batteries with higher capacity, long cycling life and higher energy and power densities.