Lithium-thionyl chloride (Li-SOC) Battery Introduction

Lithium-thionyl chloride (Li-SOC) Battery Components:

* **Negative Electrode:** The negative electrode of a lithium-thionyl chloride (Li-SOC) battery is primarily composed of metallic lithium (Li). Lithium metal possesses high energy density and a negative potential, making it a commonly used negative electrode material in lithium batteries.

* **Positive Electrode:** The active material of the positive electrode is its electrolyte solvent, namely thionyl chloride (SOCl2). Additionally, the positive electrode may contain other materials, such as carbon, to optimize battery performance.

* **Electrolyte:** The electrolyte is an anhydrous lithium tetrachloroaluminate solution of thionyl chloride (SOCl2). It provides channels for ion conduction, promoting the battery's charge and discharge reactions.

* **Separator:** The separator is a crucial component that isolates the positive and negative electrodes and prevents short circuits. It is typically made of polyolefin or glass fiber materials, requiring sufficient mechanical strength to support the positive and negative electrodes while also possessing excellent ion conductivity.

* **Casing:** Lithium-thionyl chloride batteries employ a fully sealed structure. The casing material is typically metal or plastic to effectively prevent electrolyte leakage.

The sulfur and sulfur dioxide generated in the reaction dissolve in excess thionyl chloride electrolyte. Furthermore, sulfur dioxide production during discharge causes a certain degree of pressure buildup. Since the reaction product lithium chloride (LC) is insoluble in the electrolyte, its deposition on the porous carbon cathode support negatively impacts battery performance. During battery storage, once the lithium anode comes into contact with the electrolyte, it reacts with thionyl chloride to form insoluble LiCl. This is a contact chemical reaction, and the reaction product does not deposit on the porous carbon cathode support but rather adheres to the lithium surface, forming a protective passivation film, as shown in the figure. This passivation film helps extend the battery's storage life, but it causes voltage hysteresis at the start of discharge. For batteries stored at high temperatures for extended periods, the voltage hysteresis is particularly pronounced when discharged at low temperatures or during high-current pulse discharge.

The presence of trace amounts of iron and water vapor in the battery leads to HCl formation, worsening the battery's polarization effect and significantly reducing the battery's operating voltage. Especially at higher operating currents and lower temperatures, self-discharge is exacerbated, leading to premature battery failure. This is one of the reasons why moisture and iron impurities must be carefully controlled during the raw material and production processes of lithium-thionyl chloride (LTC) batteries.

Characteristics of Lithium-Thionyl Chromium Batteries:

* **High and Stable Operating Voltage:** The nominal voltage of LTC batteries is typically 3.6V, and it remains stable during operation, making it widely used in electronic devices requiring stable voltage.

* **Wide Operating Temperature Range:** LTC batteries operate within a temperature range of -40℃ to 85℃, enabling them to function normally under various extreme temperature conditions.

* **High Energy Density:** LTC batteries are among the primary batteries with the highest energy density, possessing a high energy storage capacity.

* **Good Storage Performance:** LTC batteries have an extremely low self-discharge rate of only 1% per year, allowing them to maintain a high level of charge even after prolonged periods of non-use.

* **Good Structural Reliability:** LTC batteries employ a fully sealed structure, effectively eliminating the risk of electrolyte leakage and improving battery safety and reliability.

However, LTC batteries also have some drawbacks, such as the potential for passivation after prolonged periods of inactivity leading to voltage hysteresis and a relatively low maximum discharge current.