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Li‐ion batteries have been of a great interest for over three decades. A geometric electrode surface area is generally used for Li‐ion electrochemical parameters calculations. Since the real electrode is a complex system composed of the thick porous structure, the contact surface area between the active mass and electrolyte is far larger than geometrical. This approximation leads to a large deviation of obtained results, especially within different laboratories and for volume and surface changing materials, e. g., silicon. The article presents a new method of in situ analysis of active surface area variations applicable for Li‐ion electrodes. The method relies on the electrochemical impedance spectroscopy measurement (EIS) performed at an arbitrarily chosen state of charge during superimposed DC current flow. The correlation between a local ion concentration with a charge transfer resistance allows to evaluate the differences of the active surface area. The presented method is not affected by the SEI layer presence, the material composition, nor the lithiation mechanism. Due to limited EIS frequency range the presented method can be performed with a relatively short time. Our new in situ surface area determination can greatly improve the accuracy of the electrochemical parameters evaluation and enable the proper result analysis. We believe that our method can become a standard procedure implemented in every research focusing on the electrochemical parameter determination of the volume changing active materials.

In this work, a facile, wet chemical synthesis was utilized to achieve a series of lithium manganese oxide (LiMn2O4, (LMO) with 1–5%wt. graphene oxide (GO) composites. The average crystallite sizes estimated by the Rietveld method of LMO/GO nanocomposites were in the range of 18–27 nm. The electrochemical performance was studied using CR2013 coin-type cell batteries prepared from pristine LMO material and LMO modified with 5%wt. GO. Synthesized materials were tested as positive electrodes for Li-ion batteries in the voltage range between 3.0 and 4.3 V at room temperature. The specific discharge capacity after 100 cycles for LMO and LMO/5%wt. GO were 84 and 83 mAh g−1, respectively. The LMO material modified with 5%wt. of graphene oxide flakes retained more than 91% of its initial specific capacity, as compared with the 86% of pristine LMO material.