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The approach of substituting electrochemically active with inactive elements has widely been used to improve the electrochemical performance of Li-rich intercalation cathode materials.This especially is true for Li-rich compounds where almost all of the Li+ ions are reversibly(de)intercalated during electro-chemical cycling.The beneficial mechanism behind this substitution with electrochemically inactive ele-ments is still not clear yet.Li2RuO3 is chosen as basis for a model solid solution system to investigate the effect of electrochemically inactive elements owing to its high specific capacity of more than 300 mAh g-1 and the significant contribution of anion redox mechanism.Herein,Li2Ru1-xTixC3 solid solution series are synthesized and the effect of substituting with electrochemical inactive Ti for Ru on structure and elec-trochemical performance have been comprehensively investigated.The electrochemical performance is significantly improved,especially for Li2Ru0.8Ti0.2O3,and the capacity retention after 50 cycles increases from 81％to 90％,as compared to the end member Li2RuO3.Results of electrochemical impedance spec-troscopy show that Ti substitution reduces the charge transfer impedance,which favors the Li+ diffusion across the electrolyte-electrode interface and improves the electronic conductivity.For the first time,nuclear magnetic resonance was utilized to confirm that a small part of Ti ions exchange their position with Li ions in the Li layer.This research provides a better understanding of electrochemical inactive ele-ment substitution and strong insights for the functional design of the next generation of Li-rich cathode materials.