Abstract: Disclosed is metal composite oxides having the new crystal structure. Also disclosed are ionic conductors including the metal composite oxides and electrochemical devices comprising the ionic conductors. The metal composite oxides have an ion channel formed for easy movement of ions due to crystallographic specificity resulting from the ordering of metal ion sites and metal ion defects within the unit cell. Therefore, the metal composite oxides according to the present invention are useful in an electrochemical device requiring an ionic conductor or ionic conductivity.

Abstract: Disclosed herein is an electrolyte for lithium secondary batteries comprising: a chelating agent, which forms complexes with transition metal ions in the battery, and at the same time does not react and coordinate with lithium ions; a non-aqueous solvent; and an electrolyte salt, as well as a lithium secondary battery comprising the electrolyte. The chelating agent, which is contained in the electrolyte for lithium secondary batteries, can suppress a side reaction in which transition metal ions are reduced and deposited as transition metals on the anode. Also, the chelating agent can suppress internal short-circuits in the battery and the resulting voltage drop of the battery and a reduction in the safety and performance of the battery, which can occur when transition metals are deposited on the anode.

Abstract: The present invention relates to a lithium secondary battery comprising an overdischarge-preventing agent. Particularly, the present invention provides a lithium secondary battery comprising an overdischarge-preventing agent having superior effects for an overdischarge test and showing 90% or more capacity recovery after the test, by introducing lithium nickel oxide into a cathode for a lithium secondary battery comprising a lithium transition metal oxide capable of occluding and releasing lithium ions as an overdischarge-preventing agent to supply lithium ions such that irreversible capacity of an anode can be compensated or better, thereby lowering voltage of a cathode first to prevent voltage increase of an anode during the overdischarge test.

Abstract: The present invention relates to a lithium secondary battery comprising an overdischarge-preventing agent. Particularly, the present invention provides a lithium secondary battery comprising an overdischarge-preventing agent having superior effects for an overdischarge test and showing 90% or more capacity recovery after the test, by introducing lithium nickel oxide into a cathode for a lithium secondary battery comprising a lithium transition metal oxide capable of occluding and releasing lithium ions as an overdischarge-preventing agent to supply lithium ions such that irreversible capacity of an anode can be compensated or better, thereby lowering voltage of a cathode first to prevent voltage increase of an anode during the overdischarge test.