Lithium Thionyl Chloride (Li-SoCl2) batteries are primary (non-rechargeable) batteries that many industries widely use. These batteries are famous for their high energy density, long shelf life, and excellent performance in extreme temperatures, making them perfect for providing reliable power to devices and equipment for extended periods. As a result of these characteristics, they have become a popular choice for IoT, Utility, Medical and Industrial applications as single cells or assembled into battery packs. They have a high voltage of 3.6V and a flat discharge characteristic for excellent performance throughout use.
In this blog we’ll be taking an in-depth look at Lithium Thionyl Chloride batteries, their characteristics, cell construction and what to consider when choosing them to power your application.
Li-SoCl2 batteries offer numerous advantages, such as high capacity (energy density), a wide operating temperature range, long shelf life with low self-discharge, and high voltage stability. These features make them a compelling choice for various applications. To explore these advantages in more detail and compare them with other battery chemistries, continue reading.
In battery chemistry, the energy density is closely linked to the capacity. Batteries with higher energy densities can typically store more charge within a given volume or mass, resulting in higher capacities.
Capacity refers to the total amount of electrical charge that a battery can store. It is typically measured in Ampere-hours (Ah) or milliampere-hours (mAh). A higher capacity means the battery can provide more total charge and, therefore, power to a device before it needs to be recharged or replaced.
Energy density, on the other hand, represents the amount of energy that can be stored in a given volume or mass of the battery. It is typically expressed in watt-hours per litre (Wh/L) or watt-hours per kilogram (Wh/kg). Higher energy density means that more energy can be stored within the same physical size or weight of the battery.
In terms of energy density, Li-SoCl2 outperforms all other battery chemistries’ with an impressive 700 Watts hours per KG. Meaning they can provide more energy compared to other chemistries in the same size format. Making them the best option for long term power or if size and weight are critical factors in the applications design.
Here are the approximate energy densities of some commonly used battery chemistries.
|Chemistry||Energy Density WH/KG||Primary/Rechargeable|
|Lithium Thionyl Chloride (Li-SoCl2)||400-700||Primary|
|Lithium Polymer (Li-Po)||100-265||Rechargeable|
|Nickel-Metal Hydride (NiMH)||60-120||Rechargeable|
Note that these are approximate ranges, and the exact energy density of a particular battery will depend on various factors such as its design, purity of materials used and operating conditions.
Li-SoCl2 cells exhibit excellent performance across a wide range of temperatures, from extreme cold to high heat. They can operate reliably in temperatures as low as -60°C (-76°F) and as high as 85°C (185°F). Tadiran Batteries Extended Temperature range goes beyond the normal and has an operational temperature range of −55 °C (-67) > +130°C (266 ºF).
In comparison to other battery technology Li-SoCl2 has the widest operating range by far. Please see the Battery Chemistry Operating Temp Comparison table.
|Chemistry||Operating temp range||Primary/Rechargeable|
|Lithium Thionyl Chloride (Li-SoCl2)||-60°C~+130°C||Primary|
|Lithium polymer (Li-Po)||-10°C~+60°C||Rechargeable|
|Nickel-metal hydride (NiMH)||-20°C~+50°C||Rechargeable|
Li-SoCl2 cells have an impressive shelf life that often exceeds 10 years as a minimum but some have been proven to last 40 years in operation. They owe this impressive shelf life due to having low self-discharge rates, meaning they can retain their charge for extended periods when not in use. The low self-discharge characteristics of Lithium Thionyl Chloride (Li-SoCl2) batteries can be attributed, in part, to the phenomenon of passivation.
Passivation is a process where a protective layer forms on the surface of the lithium anode, preventing undesirable reactions and reducing self-discharge. In Li-SoCl2 batteries, the thionyl chloride electrolyte plays a crucial role in passivating the lithium anode. When the battery is not in use, the thionyl chloride electrolyte forms a stable, protective layer on the lithium surface, limiting its interaction with the surrounding environment.
This passivation layer acts as a barrier, reducing the loss of stored charge and minimizing self-discharge over time. As a result, Li-SoCl2 batteries can retain their charge for long periods, making them ideal for applications requiring low self-discharge rates, such as in remote sensors, backup power systems, and other devices that experience intermittent use.
In comparison, other chemistries may have different mechanisms to reduce self-discharge but often struggle to match the long-term low self-discharge performance of Li-SoCl2 batteries. For example, lithium-ion batteries, while known for their high energy density and relatively low self-discharge, can experience a slow but continuous self-discharge over time due to factors like electrode reactions and ionic diffusion. This can result in a gradual loss of stored energy, making them less suitable for applications requiring long shelf life or infrequent usage.
Li-SoCl2 cells offer a notable advantage over other primary battery chemistries in terms of high voltage stability. Unlike alkaline or zinc-carbon cells that exhibit voltage drops as they discharge, Li-SoCl2 cells maintain a relatively constant output voltage throughout their discharge cycle. This characteristic ensures consistent power supply, which is crucial for applications where voltage stability is critical, such as medical devices, precision instruments, and wireless communication systems. The high voltage stability of Li-SoCl2 cells allows for predictable and accurate operation, improves energy utilization, and minimizes the risk of performance issues caused by voltage fluctuations.
When it comes to Lithium Thionyl Chloride (Li-SoCl2) cells, there are two common construction types: bobbin and spirally wound. These construction methods refer to how the electrode and electrolyte layers are arranged within the cell, which changes their electrical performance.
Bobbin construction cells have a distinct feature where the anode and cathode have a relatively small shared surface area. In this type of cell, a single cylinder of cathode material is surrounded by the anode material. Due to the low common surface area, these cells have limited capability for high-rate discharges but an increased space to hold more anode material, allowing for more energy to be stored.
On the other hand, spirally wound construction involves rolling the electrodes, separator, and electrolyte into a tightly wound spiral configuration. The positive and negative electrodes are wound together with a separator in between, forming a spiral-shaped core. This core is then inserted into a cylindrical metal casing, providing structural support and serving as the outer shell of the battery. The larger surface area of the anode and cathode allows for high-rate discharges.
Both construction methods have their advantages and are suitable for different applications. Bobbin construction cells are commonly employed in applications requiring long operational life and high energy storage, where the applications base current is measurable in Microamps, such as utility metering, tracking devices, and industrial equipment. A notable example of a bobbin-constructed Li-SoCl2 cell is the Tadiran LTC series or the Saft LS range.
Spirally wound construction, on the other hand, offer high pulse rates and improved resistance to vibrations and shocks. This makes spirally wound Li-SoCl2 cells more suitable for applications that require durability and reliability in challenging environments. These cells are often found in aerospace, defence, and oil and gas industries. The Saft LSH series is a well-known example of spirally wound Li-SoCl2 cells.
Want to know more about Spirally Wound and Bobbin cells? Saft’s LS and LSH range. What is the difference? – Cell Pack Solutions
While Lithium Thionyl Chloride (Li-SoCl2) cells offer several advantages, they also have some notable disadvantages that should be taken into consideration when choosing the chemistry.
People often assume all lithium batteries are rechargeable, but Lithium Thionyl Chloride (Li-SoCl2) batteries are non-rechargeable or primary cells. Meaning they can only be used once in an application and then need replacing. The costs involved when replacing batteries in remote locations should be considered and factored in when choosing an appropriate battery chemistry. It must be noted that in low drain applications, a Li-SoCl2 cell can often last into the 10’s & 20’s of years.
Li-SoCl2 cells are sensitive to overvoltage conditions. Exposing these cells to voltages higher than their specified limits can lead to safety hazards, such as gas generation, leakage, or even rupture. It is essential to carefully adhere to the recommended voltage range and avoid subjecting Li-SoCl2 cells to excessive voltage.
Li-SoCl2 cells have a relatively high nominal voltage, typically around 3.6 volts. While this can be advantageous in certain applications, it also requires careful consideration when designing devices or circuits that are not compatible with this higher voltage level. If you require a higher voltage and want to use Li-SoCl2 then speak to one of our team about creating a custom battery pack.
When it comes to cost, there is a notable difference between Lithium Thionyl Chloride (Li-SoCl2) batteries and alkaline batteries. Generally, Li-SoCl2 batteries tend to be more expensive than alkaline batteries. The higher cost of Li-SoCl2 batteries can be attributed to several factors, including the specialized chemistry and manufacturing processes involved.
|Battery||Li-SoCl2 D Tadiran SL2780||Alkaline D cell GP13A|
|Voltage||3.6V||3.5V (3x 1.5V GP13A connected in series)|
|Dimensions||32.9⌀ x 61.5 mm||32.9⌀ x 98.7 x 61.5 mm|
|Weight||93g||405g (3x 135g)|
|Cost||£16.76 ex VAT||£3.90 ex VAT (3x GP13A)|
Comparing the cost of a Tadiran SL2780/s 3.6V 19Ah D cell vs the equivalent in alkaline. To truly compare Li-SoCl2 and Alkaline in terms of cost, we must consider other electrical factors to get a more accurate comparison. In the comparison below 3x GP D cells in series are used to get a 3.5V voltage similar to Li-SoCl2. Although 3x GP13A are more cost effective initially, the capacity and performance is still inferior in comparison. You should also factor the cost of maintenance in terms of battery changes when considering which chemistry to choose.
Please note: that this is a loose comparison and does not factor in performance data. Please see the specific data sheets for this Data.
Lithium Thionyl Chloride batteries power applications across a wide range of industries due to their unique characteristics and advantages. Here are some popular industries and applications where Li-SoCl2 batteries are commonly utilized:
These are just a few examples of the industries and applications where Li-SoCl2 batteries are widely used. Their unique characteristics make them a preferred choice in scenarios where long-term power supply, durability, and high performance are essential.
Want to know more about Lithium Thionyl Chloride?
Speak to one of our team to find out if Li-SoCL2 is the right chemistry for your project.