Battery electrode structure and method for manufacture thereof

Abstract

There are disclosed solid composite electrodes with electrode active layers that include an electrode active material, an optional election conductive material, an optional binder and other optional additives. The solid composite electrodes are formed by the deposition of an electrode composition (slurry) onto a current collector in one or many layers. The electrode structure may be characterised by a porosity of the electrode composition layer that decreases in a direction from the back side of the layer (close to the current collector) towards the outer side of the layer. The gradient of the decrease in the porosity is controlled by the content of solid substance in the slurry, by the composition of the solvent in the slurry, by the temperature of the layer drying after deposition, as well as by the pressing or calendering conditions for each layer. The electrode structures can be used in for example chemical sources of electric energy such as primary (non-rechargeable) as well as secondary (rechargeable) batteries.

Description

PRIOR APPLICATION DATA [0001] The present application claims benefit from prior U.S. provisional application Ser. No. 60 / 591,083 filed on Jul. 27, 2004 and entitled “Improvements Relating to Electrode Structures in Batteries”, and UK application 0416708.6 filed on 27th Jul. 2004, each incorporated herein by reference in its entirety.TECHNICAL FIELD [0002] The present invention relates to chemical sources of electric energy comprising positive electrodes (cathodes) and negative electrodes (anodes). In particular, the invention relates to rechargeable (secondary) and non-rechargeable (primary) battery cells comprising a negative electrode providing ions (anode), an intermediate separator element containing an electrolyte solution or a hard polymer electrolyte through which ions from a source electrode material move between cell electrodes during charge and discharge cycles of the cell, and a positive electrode (cathode) comprising an electrode depolarizer substance (cathode active mat...

AI Technical Summary

Benefits of technology

[0021] The applicant has found that the non-uniform distribution of the electrochemical reaction rate over the electrode thickness leads to non-uniform consumption of the depolarizer and hence to a reduction of the electrode capacity. Therefore, equalization of the electrochemical overvoltage value over the electrode thickness is desirable to increase the efficiency of the depolarizer utilization. The applicant has found that this task can be addressed by the use of electrodes with a porosity gradient over the thickness, namely the electrodes having the porosity that increases from the face side towards the real side. In other words, it would be expedient for getting better results in the capacity and power of chemical sources of electrical energy to use electrodes with varying porosity, namely electrodes having a porosity that decreases from the back to the face side.

Problems solved by technology

The applicant has found that the non-uniform distribution of the electrochemical reaction rate over the electrode thickness leads to non-uniform consumption of the depolarizer and hence to a reduction of the electrode capacity.

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