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  1. An Introduction to Battery Separators

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    Batteries consist of the following basic components: an anode, a cathode, and an electrolyte. However, another key part that is often overlooked is the battery separator. This component is vital to the functionality and performance of batteries. Below, we outline what it is, its origins, and its applications.

    What Is a Battery Separator?

    Battery Separator in Battery

    A battery separator is a type of polymeric membrane that is positioned between the positively charged anode and the negatively charged cathode. This positioning helps prevent electrical short circuiting.

    When the membrane becomes moistened by the electrolyte, it acts as a catalyst that increases the movement of ions from one electrode to the other. The ions move from the cathode to the anode when the battery is being charged and from the anode to the cathode when the battery is being discharged. Since the membrane controls the number of ions that move between terminals, it is also responsible for the charge and discharge of the battery under ideal conditions.

    One thing to keep in mind is that separators allow ions to pass through freely, but they are not electrically conductive. Therefore, they always act as isolators.

    The History of Battery Separators

    The first rechargeable battery was invented by French physicist Gaston Planté in 1859. This battery, like later variations, featured a wet cell/flooded design. It was not until the development of sealed nickel-cadmium batteries in 1947 and maintenance-free lead-acid batteries in the 1970s that battery separators were introduced.

    The porous component absorbs electrolytes while pressed against the electrodes, ensuring the initiation of the required chemical reaction. It also allows for a tightly wound or stacked separator/electrode arrangement that forms a solid mechanical unit offering similar performance to earlier flooded batteries in a smaller and leak-proof package.  Since the gases created during charging are absorbed, there is no need for venting. This design eliminates the risk of water loss.

    The first battery separators were made from wood. However, the material quickly deteriorated within the electrolyte. They were later manufactured from cellulose, glass fiber mat, polyurethane, and rubber. Today, nickel-based batteries utilize separators made from porous cellophane, nylon, or polyolefin film, sealed lead-acid batteries use separators made from glass fiber mat soaked in sulfuric acid, and lithium-ion batteries use separators made from polyolefin.

    Primary Cell Applications of Battery Separators

    Lithium metal batteries are sometimes referred to as primary or non-rechargeable batteries. They have two or more cells that are electrically connected together and equipped with the necessary devices. The term “cell” refers to an encased electrochemical unit—i.e., one positive electrode and one negative electrode—that exhibits a voltage differential between the two terminals. One of the most common primary cells is the lithium thionyl chloride cell. In these cells, the separator acts as an electron insulator. It allows the ions to move between electrodes while electrically isolating the electrodes. By performing this function, it prevents short circuiting from occurring.

    Quality Battery Separators From H&V

    If you’re looking for high-quality battery separators, turn to the experts at Hollingsworth & Vose! We produce battery separator materials for alkaline and lithium thionyl chloride batteries. For general information about battery separators or specific information about our products, contact us today.