Primary Li-SOCl2 Battery

The primary batteries consist of the main components are anode (Positive Electrode) and Cathode(Negative Electrode) and an Electrolyte. The batteries which comprise of lithium as a cathode is known as “Lithium Battery’ and flow of electrons which is formed by the oxidation which makes the electrical energy. 

Lithium Thionyl Cells are available in two different constructions bobbin and spiral wound. In both the versions, a non-aqueous electrolyte offers relatively higher impedance. The solution for the impedance problem is by increasing the surface area by accepting a wound cathode. But this solution cost is higher. The main disadvantage of spiral wound construction is reduced energy density and shorter operating life i.e. the extra surface area results in very higher self-discharge rate.

Bobbin-type Lithium thionyl chloride batteries are mostly suited for low power applications because of its high energy density, low self-discharge rate and long life up to 10 years based on the application. Bobbin lithium batteries offer a wide temperature range of -55C to +85C. high capacity in small packet makes bobbin type batteries to withstand changes in the pressure, temperature and shock make cells perfect for use in remote locations and extreme environmental conditions.

Lithium thionyl chloride(Li-SoCL2) batteries consist of metallic lithium as an anode (which is lightest of the all the metals) and a liquid cathode which comprises of a porous carbon current collector which is filled with thionyl chloride (SOCl2). The Li-SoCL2 cells offer a voltage of 3.6V and are cylindrical in Shape and available in different shapes from 1/2AA to DD format with a spiral structure for power applications and bobbin construction for prolonged discharge.

Lithium thionyl chloride batteries are the most prominent in primary family batteries which offer the highest voltage and energy, low self-discharge rate and longest storage life. These batteries are most suitable for long term applications such as metering, power devices, water, heat and gas meters and most importantly as backup power for memory ICs. 

At Anode:

Li → Li+ + e-

At Cathode:

2SOCl2 + 4Li+ + 4e- →4LiCl + S + SO2

Total chemical reaction inside the cell is:

2SOCl2 + 4Li → 4LiCl + S + SO2

The higher voltage of 3.6V can be achieved by oxidation and deoxidation reaction between cathode and thionyl chloride anode. 

Li/SOCl2 battery structure

Characteristics of Primary Li-SOCl2 Lithium battery:

1.      Long Storage Life Time

  •  Lithium batteries can be used for a long time with better performance.
  •  It can be used above 5 years. In some applications, It can be used more than 10 years(Depends on different working request).
  • The self-discharge time for this battery is less than 2% per year.

2.      Wide operating Temperature range

  •  Lithium batteries can be operated in wide temperature from low to high (-60C to +85C)
  •  Lithium batteries have the organic solvents as the electrolyte so can it can perform well in cold and hotter conditions then manganese dry batteries.

3.      High-grade anti-leakage characteristics

  •  Adopt stainless steel material, laser, and hermetic glass-to-metal welding sealed which keep our battery have a unique performance in a wet environment and there is no leakage.

4.      Higher Operating Voltage

  •  Lithium batteries are operating at a voltage from 3V – 3.6V, which is more than double than manganese dry batteries.
  •  Only one lithium battery will be required instead of 2 manganese dry batteries.

5.      High energy density and less weight

  •  High energy density Could achieve more than 650wh/kg. It is about 3-10 times of the other series lithium batteries.

Use period of Lithium batteries

Calculating the use period of primary lithium batteries and their life:

A. Use Time at Constant Discharge Rate                                             

Assume:

1. Nominal capacity: 1 Ahr Battery

2. Current Value: 5 mA

Using the formula we can calculate use time given below:

Use Time = Nominal Capacity / Use Current    … … … (1.1)

Applying the values in equation 1.1 we get,

Use time = 1 Ah/ 0.05 A

= 200 hrs                                             … … …(1.2)

2. Use Time at Pulse Discharge Condition

Assume:

Battery Nominal Capacity: 1 Ahr

Base Current = 0.5 mA

1st pulse discharge = 2.5mA per 5 sec

2nd Pulse discharge = 10mA per 1 sec

Discharge cycle continuous for 10 second interval.

Consumption capacity Ahr per cycle is calculated by the formula given below:

Consumption capacity(Ahr) per cycle is = area α + area β + area γ    … … … 2.1

Apply the values in the equation 2.1 we get, consumption capacity per cycle is

= {(0.01 – 0.0025) * 1/3600} +{(0.0025 – 0.0005) * 5/3600} + {0.0005 * 10/3600}

= 0.0000125 Ahr

Now the Use Time is,

Use time [hr] = Cycle Number * Time per 1 cycle

= (Nominal Capacity/ Used Capacity per cycle) * Time[Hr] per cycle

= {(2/0.0000125) * (10/360)}

= 444 hours

So the use time of the battery is 444 hours.

Comparison of Bobbin and Spiral Primary Lithium Battery

Energy Density

Energy Density Real

Voltage Characteristics