Nonaqueous electrolyte battery

Abstract

A nonaqueous electrolyte battery includes a case, a nonaqueous electrolyte provided in the case, a positive electrode provided in the case, and a negative electrode provided in the case, including a negative electrode active material and an electronic conductor containing a carbonaceous material, wherein a negative electrode working potential is nobler at least 1 V than a lithium electrode potential, and the carbonaceous material has a spacing (d002) of (002) plane of 0.344 nm or more and 0.352 nm or less, and a crystallite size (Lc) in the C-axis direction of 10 nm or less.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-332109, filed Sep. 24, 2003, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonaqueous electrolyte battery. The invention is applicable to both a nonaqueous electrolyte primary battery and a nonaqueous electrolyte secondary battery. 2. Description of the Related Art Electronic appliances are becoming smaller in size and lighter in weight recently owing to rapid technical progress in the field of electronics. As a result, cordless and portable electronic appliances are being more prevalent, and secondary batteries used as a driving source are demanded to be smaller in size, lighter in weight, and higher in energy density. To meet such demands, lithium secondary batteries of high energy density are being developed. Lately...

AI Technical Summary

Benefits of technology

The effect of the invention is achieved as far as the electronic conductor is mainly made of the carbonaceous material, that is, more than 50 wt. % of the electronic conductor is the carbonaceous material. In the electronic conductor, acetylene black or graphite can be added at a rate not exceeding 50 wt. % of the electronic conductor components.

is achieved as far as the electronic conductor is mainly made of the carbonaceous material, that is, more than 50 wt. % of the electronic conductor is the carbonaceous material. In the electronic conductor, acetylene black or graphite can be added at a rate not exceeding 50 wt. % of the electronic conductor components.

A binder can be contained in the negative electrode layer. Such a binder can include, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber.

The blending ratio of the negative electrode active material, the electronic conductor, and the binder is 70 to 96 wt. % of the negative electrode active material, 2 to 28 wt. % of the electronic conductor, and 2 to 28 wt. % of the binder. If the electronic conductor is contained at less than 2 wt. %, the current collecting performance is lowered, and the high rate characteristic may decline. If the binder is contained at less than 2 wt. %, the binding strength of the compound layer and current collector is lowered, and the cycle performance may drop. On the other hand, from the viewpoint of high capacity, the content each of the electronic conductor and binder is preferred to be 28 wt. % or less.

The negative electrode can be manufactured, for example, by suspending the negative electrode active material, electronic conductor and binder in a proper solvent, applying this suspension on a current collector of aluminum foil or the like, and drying and pressing.

The porous separator is, for example, a porous film including polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), a synthetic resin nonwoven fabric, and the like. In particular, a porous film made of polyethylene or polypropylene, or both of them may be preferred because the safety of the secondary battery can be enhanced.

Problems solved by technology

However, since lithium titanate is poor in conductivity, when the negative electrode is manufactured without adding an electronic conductor as in the publication, the battery is inferior under heavy currents.

However, in a nonaqueous electrolyte battery having a negative electrode containing an electronic conductor made of a carbon material and lithium titanate, when the battery is stored in a high temperature environment, or when charging and discharging operation is repeated in a high temperature environment, the electronic conductor reacts with an electrolysis solution, and a large volume of gas is generated, thus the battery characteristics are extremely lowered.

Images