Lithium-ion battery (LIBs) technology has matured significantly during the past two decades as not only the world but also energy has become increasingly mobile. LIBs have grown to become the dominant battery technology across a wide range of applications. It is a disruptive technology that will significantly alter a variety of industry sectors, including consumer electronics, energy, oil and gas, transportation, and maritime.

Listed below are the key strengths of lithium-ion batteries for underwater applications, as identified by GlobalData.

Lighter and higher power-density than traditional batteries

Lithium is the lightest of all metals, has the greatest electrochemical potential, and provides the largest energy density per weight. Rechargeable batteries using lithium metal anodes (negative electrodes) are capable of providing both high voltage and excellent capacity.

The energy density of the LIB is typically twice that of the standard Ni-Cd battery. Improvements in electrode active materials have the potential of increasing the energy density close to three times that of the Ni-Cd. In addition to high capacity, the load characteristics are reasonably good and behave similarly to the Ni-Cd in terms of discharge characteristics. The flat discharge curve offers effective utilisation of the stored power in a desirable voltage spectrum.

With its high energy density, LIB solutions are significantly smaller in size and weigh less than competitive products. Therefore, LIB battery is the best source of power for UUV, torpedoes, submersibles and submarines. Its compact design brings higher efficiency and strengthens reliability for diverse marine applications.

In terms of the energy storage and power output requirements of a conventional submarine, LIBs offer far superior performance compared to alternative battery technologies.

Smaller and in novel shapes

The high cell voltage of lithium-ion battery allows the manufacture of battery packs consisting of only one cell. Many of today’s mobile phones run on a single cell, an advantage that simplifies battery design. One of the key advantages of LIBs are their ability to be moulded into different shapes and sizes to fill any space available in the devices they power.

Higher energy density batteries are an advantage for submarines, as they can provide significant space savings, reducing the overall size of the submarine and consequently reducing propulsion, power, and support system requirements. Similarly, a much greater energy storage capacity can be achieved compared to a lead-acid battery-powered submarine of the same size. This capacity can extend the underwater endurance of the submarine and greatly increase its stealth.

Fast recharging and good performance

It has a low self-discharge rate of approximately 5–10%, which is significantly lower in comparison with other battery types in the market. No memory and scheduled cycling are needed to prolong battery life. Due to these desirable traits, Li-ion battery systems were tested for application in underwater vehicles and have demonstrated high potential in replacing lead-acid battery systems in diesel-electric submarines.

Long endurance

The life-time of a lead-acid battery in a submarine ranges from four to eight years and depends on parameters such as usage cycles and temperature. The life-time of LIBs varies between different types of Li-ion chemistries, used cycle depth, charge and discharge rates, and temperature. But it is reasonable to expect that a lithium-Ion based submarine battery should provide significantly longer lifetimes. Claims of long life-time must be taken with some consideration though as not many applications have had cells in operation for more than ten years. Accelerated aging tests are used but do not replicate the exact conditions which the batteries face during their life.

Less maintenance required

The LIB is a low maintenance battery. There is no memory, and no scheduled cycling is required to prolong the battery’s life. Also, the self-discharge is less than half compared to Ni-Cd and NiMH, making the Li-ion well suited for modern fuel gauge applications.

This is an edited extract from the Lithium-ion Batteries for Underwater Applications – Thematic Research report produced by GlobalData Thematic Research.