Recently, development of portable and cordless types of such electronic apparatuses as AV equipment and personal computers has made rapid progress, and a secondary cell of small size, light weight and providing a high energy density is highly demanded as a driving power supply for such apparatus. Particularly, a secondary lithium cell with a negative electrode of metallic lithium used as an active material is highly expected to be a cell capable of providing a high voltage and a high energy density. However, because of insufficiency in safety and reliability, such lithium cell has not been practically applied for the present.
It is considered that the safety is reduced because the negative electrode of metallic lithium is changed to a dendritic shape by repetitive charging and discharging, leading to possible internal short circuiting and heat generating reaction between the electrolyte and lithium of the dendritic shape.
In order to solve the problem, a secondary lithium ion cell with a negative electrode of carbon material that is capable of reversibly intercalating and deintercalating lithium and a positive electrode of such oxide of a transition metal containing lithium as LiCoO.sub.2, LiNiO.sub.2 and LiMn.sub.2 O.sub.4 has been suggested.
In such secondary lithium ion cell, since lithium is intercalated into the carbon material of negative electrode during charging, precipitation of lithium is theoretically never caused on the negative electrode plate, it is advantageous in that internal short circuiting of the cell is restricted, and the cell is superior in safety and reliability.
Even in the case of such secondary lithium ion cell with a negative pole of carbon material that is capable of reversibly intercalating and deintercalating lithium, however, lithium is deposited on the negative electrode plate gradually as charging and discharging are repetitively conducted, and it has been a problem that the cell is reduced in safety and reliability in the final stage of its cycle life.
Hence, it is an object of the invention to solve the problem, and provide a cell superior in charging and discharging cycle life characteristics, safety and reliability by preventing precipitation of lithium on a negative electrode plate in the final stage of cycle life.