[Complete Battery Guide]⑨ Even Edison Made It... Differences Between Secondary and Primary Batteries

Editor's NoteWe are now in the battery era. Batteries are found in almost everything, from mobile phones and laptops to electric vehicles. [Complete Battery Mastery] is a section created to easily convey the basics of batteries, their ecosystem, company information, industry trends, and outlook to general readers, students, and investors interested in the battery industry and related companies. We will meet you every Saturday.

The Korean word '전지 (電池)' is translated into English as both 'Battery' and 'Cell.' The smallest unit that makes up a battery, including the anode, cathode, electrolyte, and separator, is commonly referred to as a 'cell.' A battery can consist of a single cell or multiple cells connected together to form one battery.

Batteries can be broadly divided into chemical batteries and physical batteries. Among these, the batteries we commonly talk about in daily life are chemical batteries in the narrow sense. Chemical batteries are devices that generate electricity through chemical reactions. Chemical batteries are further classified into primary batteries, secondary batteries, and fuel cells based on their operation. A primary battery (Primary Cell) is a chemical battery that can be used only once during its lifespan, while a secondary battery (Secondary Cell) can be repeatedly charged and discharged for continuous use. Lithium-ion batteries used in smartphones and electric vehicles are secondary batteries. For reference, physical batteries include nuclear batteries, solar thermal batteries, geothermal batteries, and thermoelectric devices.

The Volta cell and Daniel cell introduced in the previous article are significant for creating the prototype of batteries by utilizing oxidation and reduction principles. However, their shape and method differ greatly from the batteries we use today. After the early battery pioneers, inventions by various scientists have contributed to the current form of batteries.

The Emergence of the 'Dry Cell'

In modern times, batteries became widespread among the public after the introduction of the manganese battery. Manganese batteries are still widely used in watches, remote controls, and toys. The person who discovered the basic principle of the manganese battery was the French engineer Georges Leclanch?. The battery designed by Leclanch? in 1877 consisted of a sealed glass bottle containing a porous ceramic. Inside the glass bottle, a zinc plate (Zn) was inserted and filled with an ammonium chloride (NH4Cl) solution. The porous ceramic was filled with manganese dioxide (MnO2) and carbon powder, with a carbon rod inserted in the center.

The zinc plate and ammonium chloride acted as the anode and anode electrolyte, respectively, while the carbon rod served as the cathode, and manganese dioxide was the cathode active material. The Leclanch? cell produced an electromotive force of 1.5V, which was 0.4V higher than the Daniel cell, and had the advantage of being portable since the electrolyte liquid did not flow. However, since it still used liquid, it was classified as a wet cell.

Le Clanche training camp

The person who improved the Leclanch? cell was Carl Gassner, a German physician and inventor. Gassner mixed the electrolyte with plaster to make it paste-like. This was the beginning of the dry cell, or dry battery. Gassner filed a patent related to this in 1888 and began mass production in 1896. Gassner's dry battery was inexpensive, easy to manufacture, and highly portable, achieving great commercial success. After Gassner's dry battery, various types of manganese batteries appeared.

Both the Leclanch? cell and Gassner's dry battery are manganese batteries with similar principles. Electrons released as the zinc metal at the anode oxidizes flow through the wire to the cathode carbon rod, generating current. The zinc that loses electrons reacts with chloride ions (Cl-) from the ammonium chloride electrolyte to form zinc chloride (ZnCl2). Ammonium ions (NH4+) move toward the cathode.

At the cathode, manganese dioxide undergoes a reduction reaction by gaining electrons and combines with hydrogen gas to form manganese oxyhydroxide (MnOOH). The carbon rod does not directly participate in the chemical reaction but acts as a current collector. The cathode active material, manganese dioxide, also serves as a depolarizer by preventing the 'polarization phenomenon' that produces hydrogen gas.

Later, the manganese dry battery was improved to have a cylindrical zinc metal surrounding the anode. If you peel off the outer metal casing of a manganese dry battery, you will find an insulator surrounding a cylindrical zinc case, a separator, and cathode active material arranged in order. A carbon rod is positioned at the center.

'Strong and Long-lasting Battery'

Manganese dry batteries dominated the battery market for decades until the alkaline battery appeared in 1959. Alkaline batteries use an alkaline (basic) electrolyte, which can extend the lifespan and usage period more than three times compared to conventional manganese batteries.

The first alkaline battery was invented in 1959 by Lewis Fredrick Urry of the American battery company Eveready Battery Company. Eveready is the predecessor of Energizer, well known for the slogan 'Strong and Long-lasting Battery.'

Alkaline batteries are similar to conventional manganese batteries in that they use zinc for the anode and manganese dioxide for the cathode. The nominal voltage is also the same at 1.5V. However, the electrolyte was replaced from acidic ammonium chloride to alkaline potassium hydroxide (KOH). The hydroxide ions (OH-) generated by the ionization of potassium hydroxide move faster, allowing a stronger current to be produced.

Since alkaline batteries also use manganese, they can broadly be considered a type of manganese battery. However, the structure of alkaline batteries is the opposite of conventional manganese batteries. The metal case acts as the cathode current collector, with cathode active material and anode active material arranged inside. A brass rod serving as the anode current collector is at the center. The amount of zinc in the anode active material is greater than in manganese batteries, allowing the chemical reaction to last longer. Alkaline batteries are sold not only in cylindrical form but also as button cells.

The First Secondary Battery, Still in Use

Secondary batteries, which can be used repeatedly through charging and discharging, are currently enjoying a golden age with the advent of lithium-ion batteries, but their history is quite long. The world's first secondary battery was the lead-acid battery devised in 1859 by French scientist Gaston Plante. Just as manganese batteries, the prototype of primary batteries, are still in use, lead-acid batteries have been loved for over 160 years and firmly hold their place as automotive batteries today.

The lead-acid battery consists of a structure where lead (Pb) plates used as the anode and lead dioxide (PbO2) plates used as the cathode are immersed in a dilute sulfuric acid (H2SO4) electrolyte solution. The nominal voltage of a lead-acid battery is about 2V. Typically, automotive lead-acid batteries connect 6 to 7 cells in series to produce 12 to 13V.

Plante's Lead-Acid Battery

When the two electrodes of a lead-acid battery are connected in a circuit, two electrons leave the lead plate at the anode and flow through the wire to the cathode, generating current. The lead ions (Pb2+) that lose electrons combine with sulfate ions in the electrolyte to form lead sulfate (PbSO4). At the cathode, lead dioxide reacts chemically with the sulfuric acid solution to produce lead sulfate and water (H2O). As this process repeats, the sulfuric acid solution mixed with water becomes diluted, and chemical reactions cease, marking the end of the battery's life.

While primary batteries cannot be reused, lead-acid batteries can create a reverse chemical reaction by applying voltage to the cathode. When an external voltage is connected to charge the lead-acid battery, the lead sulfate (PbSO4) precipitated at the anode gains electrons to become lead, and sulfate ions are released back into the electrolyte solution. At the cathode, lead sulfate reacts with water to become lead dioxide, releasing hydrogen and sulfate ions. The discharged lead-acid battery is restored to its original state through the charging process. By repeating discharge and charge cycles, lead-acid batteries can be used continuously.

In theory, lead-acid batteries can be used indefinitely by repeating charge and discharge cycles, but in practice, this is not the case. Overcharging or deep discharging lead-acid batteries can generate hydrogen or oxygen gas, posing an explosion risk. Also, if unused for a long time, lead sulfate precipitates adhere to the plates, causing sulfation, which degrades battery performance. Advances in lead-acid battery technology have largely overcome these issues.

Lead-Acid Batteries Used in Electric Vehicles

Despite their long history, lead-acid batteries remain robust because they are stable and inexpensive. As of November 2023, the price of lead, the main raw material for lead-acid batteries, was $2,097 per ton on the London Metal Exchange (LME). After lead-acid batteries, nickel (Ni)-based secondary batteries appeared. Nickel prices are much higher at $17,750 per ton compared to lead. Lead-acid batteries have a simple structure, making them easy to manufacture and less prone to fire hazards caused by overheating. They also do not exhibit the memory effect seen in nickel-based secondary batteries.

Lead-acid batteries are still effectively used not only in internal combustion engine vehicles but also in electric vehicles powered primarily by lithium-ion batteries. While lithium-ion batteries provide power to the motors needed for driving, lead-acid batteries supply power to various other electronic devices. Components such as starters, lighting, and infotainment systems, originally used in internal combustion engine vehicles, are still utilized in electric vehicles. It is considered more efficient to use existing products with proven performance and reliability rather than developing new parts tailored to lithium-ion battery specifications.

Lead-acid batteries were also used in early electric vehicles in the 1890s. Despite their advantages, lead-acid batteries had many limitations as the main power source for electric vehicles. To produce the high capacity needed to move a car, they were too heavy and had long charging times. With the mass introduction of inexpensive internal combustion engine vehicles, lead-acid battery electric vehicles gradually disappeared. Today, they are used only in some applications such as golf carts.

Inventor Edison Also Made Nickel-Iron Secondary Batteries

Shortly after Plante developed the lead-acid battery, Swedish scientist Waldemar Jungner invented the nickel-cadmium (Ni-Cd) battery in 1899. Also known as the 'Jungner battery,' it used nickel hydroxide for the cathode, cadmium for the anode, and potassium hydroxide as the electrolyte.

Nickel-cadmium batteries have advantages over lead-acid batteries, such as shorter charge-discharge times, resistance to vibration and shock, and the ability to generate strong currents. However, because they use the toxic substance cadmium, they have always been accompanied by environmental concerns. Nickel-cadmium batteries were the hallmark of secondary batteries until lithium-ion batteries became popular in the 1990s.

Electric car developed by Edison. Equipped with a nickel-iron battery, it can travel up to 1000 miles.

The advent of lead-acid battery-powered cars also greatly influenced inventor Thomas Edison. In 1901, Edison developed the nickel-iron battery for use in electric vehicles. The nickel-iron battery uses iron for the anode, nickel oxyhydroxide for the cathode, and potassium hydroxide solution as the electrolyte. It had high energy density and short charging times but was expensive to manufacture and thus not widely adopted at the time. Edison even produced electric cars equipped with nickel-iron batteries. These cars could travel 1,000 miles (about 1,609 km) on a single charge.

Edison's nickel-iron batteries are durable and have a long lifespan, and they are still used in industrial applications today. In addition, there are various nickel-based secondary batteries such as nickel-metal hydride, nickel-sulfur, and nickel-zinc batteries.