Lithium secondary battery with high energy density

Abstract

The present invention relates to electrodes for a lithium secondary battery with a high energy density and a secondary battery with a high energy density using the same. A negative electrode includes a material which can be alloyed with lithium alloy. A positive electrode is made of a transition metal oxide which can reversibly intercalate or deintercalate lithium. Here, the entire reversible lithium storage capacity of the positive electrode is greater than the capacity of lithium dischargeable from the positive electrode. Further, the present invention relates to electrodes for a lithium secondary battery in which metal lithium is coated on a negative electrode, a positive electrode, or both, a method of manufacturing the electrodes, and a lithium secondary battery including the electrodes. The lithium secondary battery of the present invention is excellent in safety because metal lithium does not remain after being activated and excellent in a capacity per unit weight.

Description

[0001]Priority to Korean patent application number 2009-0045776 filed on May 26, 2009, the entire disclosure of which is incorporated by reference herein, is claimed.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a lithium secondary battery with a high energy density and, more particularly, to a lithium secondary battery with metal lithium coated on the electrode surface of a negative electrode or a positive electrode or both, in which the negative electrode includes a material which can be alloyed with lithium and having a capacity per unit weight of 700 mAh / g to 4300 mAh / g, the positive electrode is made of a transition metal oxide capable of reversibly intercalating and deintercalating lithium, and the entire reversible lithium storage capacity is included in the positive electrode (i.e., when the battery is fabricated, the entire reversible lithium storage capacity is included in the positive electrode and greater than a lithium ...

AI Technical Summary

Benefits of technology

[0010]It is, therefore, an object of the present invention to provide a lithium secondary battery which is capable of solving a danger according to the use of metal lithium and also has a high energy density of the same degree as a metal lithium battery.

[0011]A method of previously doping metal lithium on a lithium secondary battery and then fully consuming the doped metal lithium in a process of activating the battery is used. Accordingly, the capacity of the battery can be increased and at the same time, dangers resulting from metal lithium, such as explosion, can be solved. In other words, in the battery of the present invention, the lithium storage and discharge ability of negative electrode and positive electrode materials included in the battery is utilized to the maximum extent. Accordingly, a reversible capacity after activation can be significantly increased, and metal lithium during the activation can be fully consumed, thereby being capable of avoiding a danger of metal lithium.

Problems solved by technology

However, the material is problematic in that the loss of an initial irreversible capacity is great.

However, the material is problematic in that it has a great reaction with an electrolyte in the full charge state because it needs to be charged with a high voltage in order to achieve a high capacity characteristic.

Further, a battery using the material is insufficient in the safety of a unit cell when the capacity of the unit cell is increased and thus problematic in that thermal runaway and ignition are generated when being overcharged or stored in a hot box of 150° C.

The lithium secondary battery, however, has a drawback in that most of the transition metal oxide (i.e., an inactive solid compound) remains within the battery after lithium is used, thereby deteriorating the energy density, because the lithium important to increase the capacity is stored in an initial lithium transition metal oxide.

However, the above methods can steadily increase reversibility according to lithium charge and discharge, but is problematic in that it does not fundamentally prevent ignition and explosion resulting from metal lithium when the battery is used in abnormal environments or the battery is overheated upon misuse.

However, this patent is problematic in that lithium metal difficult to mechanically handle must be used in order to dope only a necessary amount of lithium (i.e., very thin within 5 to 20 micron) on a common capacitor or a lithium battery.

Further, this patent has a difficulty in that if this patent is applied to a capacitor or battery with a high capacity and a wide electrode area, the thin metal lithium foil must be adhered to the wide area.

If the current collector having holes is used, there are problems in that the mechanical strength of the electrode is weakened and a process of manufacturing the electrode is complicated as compared with a case in which a uniform metallic foil current collector with no hole is used.

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