The electrochemical performance and charge transfer resistance of an all-solid-state lithium ion battery consisting of LiCoO2 (LCO; cathode), Li6.75La3Zr1.75Nb0.25O12 (LLZONb; solid electrolyte), and lithium (anode) were investigated. This battery has favorable charge–discharge behavior and exhibits good stable cycle performance. No other reaction phase or exfoliation was evident at the interface between LCO and LLZONb after 100 charge–discharge cycles. The interfacial resistance between LCO and LLZONb is comparable to that of lithium ion batteries with liquid organic electrolytes, and the activation energy of the interfacial resistance of this battery is still lower than that of a lithium ion battery with a liquid organic electrolyte.