Lithium Batteries for Biomedical Applications

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the capacity of LiCoO2 (at 131 mAh/g). Li metal also has a very low standard potential of 3.05 V at 25C, which, when combined with any of the cathode materials discussed here, makes an electrochemical couple with high potential. These two factors, high capacity and low reduction potential, make lithium a good anode material for many batteries. However, there are some limitations. Most significant is the reactivity of lithium metal with water, which prohibits the use of aqueous electrolytes in lithium batteries under ordinary conditions. This typically limits lithium-anode battery systems to the use of organic electrolytes or inorganic electrolytes/soluble cathodes. In using these nonaqueous electrolytes, the conductivity of the electrolyte is limited, leading to increased cell resistance. However, the selfdischarge of the system is also typically low, which is important for long life in implanted devices. In general, lithium-anode batteries can be designed to provide high safety and reliability for implantable medical applications, as has been demonstrated by ample field data over the last 30 years.

Lithium Batteries for Biomedical Applications

Esther S.Takeuchi and Randolph A. Leising Abstract Lithium batteries have been successfully used in implantable biomedical devices for the last 30 years, and in some cases the use of lithium power sources has significantly contributed to the viability of the device. These battery systems fall into two major categories: primary, or single-use, cells containing lithium-metal anodes; and secondary, or rechargeable, systems utilizing lithium-ion chemistry. Primary lithium batteries have been used for implantable devices such as cardiac pacemakers, drug pumps, neurostimulators, and cardiac defibrillators. Rechargeable batteries have been used with left ventricular assist devices and total artificial hearts. All of these cells share the characteristics of high safety, reliability, energy density, and predictability of performance. Additionally, state-of-charge indication and low self-discharge are important features, along with charging safety and high cycle life for rechargeable cells.

Lithium/Iodine Batteries Lithium-anode batteries have played a key role in making implantable biomedical devices a viable therapy. The first implantable device to use a lithium battery was the cardiac pacemaker. The first implantable pacemaker was developed over 40 years ago,2 and a number of different types of power sources were used in early versions of the device. These power sources included zinc/mercury Mallory cells, rechargeable Ni-Cd batteries, nuclear batteries, and several lithium-battery systems. However, for the last 30 years, the lithium/ iodine battery has been the dominant battery choice for powering implantable pacemakers. The basic cell reaction in a lithium/ iodine battery is

Keywords: biomaterials, chemical reactions, electrical properties, mixed oxides, rechargeable lithium batteries.

Introduction

Lithium-Anode Systems

The year 2002 marks the 30th anniversary of the fir

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