Science Time Machine | The “birth” of batteries can actually be thanked to frogs?

One of the important qualities of scientists is their keen insight into abnormal phenomena and their unremitting spirit of exploration. In 1786, Italian biologist Galvani accidentally touched the exposed nerve on the leg of a dissected frog with a surgical scalpel, and an amazing scene occurred: the frog's leg twitched violently in an instant. This unexpected discovery inspired Galvani's friend, Italian physicist Volta. Inspired by this frog leg experiment, Volta successfully developed the first battery in human history - the voltaic pile 1,800 years ago.

On March 20 of the same year, Volta submitted a manuscript describing his invention in detail to the Royal Society of London. Compared with the "Leyden jar" of the time, the Voltaic pile could continuously supply power by connecting the metal wires at both ends, becoming the forerunner of modern batteries. The invention of the Voltaic pile marked the first time that humans had a relatively stable source of electric current, providing unprecedented conditions for scientific research and pushing the field of electricity into a new stage of quantitative research.

Galvani discovered bioelectricity

In 1786, Galvani precisely cut open the abdominal muscles of a frog and carefully separated the nerves of the lower limbs for research. When dissecting the second frog, the scalpel accidentally touched the generator working next to it, and he observed abnormal twitching of the frog's leg muscles.

Galvani was very curious about this phenomenon and initially thought that the frog was not completely dead. After further investigation, he determined the connection between the generator, the scalpel and the frog's nerve twitching, and set out to verify whether the electric current in the air could also induce the same reaction. He connected one end of the frog's leg nerve to an insulated metal rod placed on the roof and the other end to the ground. Galvani found that the frog's legs would also twitch during thunderstorms.

He then conducted more experiments, placing a brass hook with a frog leg nerve on an iron rod, and the frog muscles would twitch regardless of the weather. Finally, Galvani used two different metals to contact the muscles and nerves of dead frogs and connected them, and also observed muscle twitching.

Although these phenomena should have suggested that the twitching was caused by external electric current, Galvani, who focused on bioelectricity research, believed that it was the frog's own bioelectricity that formed a circuit with the outside world. He inferred that the electricity came from the living muscles, and that two different metals formed a circuit between the frog's nerves and muscles, and named this electricity "bioelectricity."

Volta invented the first battery in human history

After learning about the relevant experiments, Italian physicist Alessandro Volta explored them in depth and made a major breakthrough. In 1800, he successfully invented the Voltaic pile, which could generate electric current continuously and changed the world from then on.

In 1799, after celebrating his 45th birthday, Volta, inspired by Galvani's research, decided to study the phenomenon of "bioelectricity" in depth. He creatively designed a device: metal zinc rings and copper rings were stacked alternately, separated by paper or wool soaked in salt water. As the number of rings increased, when stacked to 10, 20, or even 30, a columnar structure was formed, generating a significant current, which was the prototype of the Voltaic pile.

Volta discovered that the more layers are stacked, the stronger the current generated. Through experiments, he proposed the theory of potential difference: when different metals come into contact, opposite charges will be generated on their surfaces, forming a voltage. He also summarized a metal sequence, that is, an electrical element table, in which when any metal comes into contact with the metal behind it in the sequence, the former is positively charged and the latter is negatively charged. This discovery revealed the essential connection between voltage and current, allowing humans to understand electricity beyond the scope of static electricity and enter the era of controllable and flowing current.

On March 20, 1800, Volta formally proposed that electric charge flows in wires like water, flowing from high voltage to low voltage, forming electric current, that is, potential difference. He wrote this theory into a paper "On the Electricity Excited by the Contact of Dissimilar Metallic Materials" and sent it to the Royal Society of London.

On November 20 of the same year, French Emperor Napoleon personally summoned Volta to Paris and watched the battery experiment. Deeply shocked, Napoleon immediately ordered French scholars to set up a special committee to further study and promote this revolutionary invention. In order to promote scientific research, relevant departments organized a series of large-scale experiments and awarded Volta a bonus of 6,000 francs and a medal of honor. In addition, a commemorative gold coin with Volta's portrait was issued to recognize his outstanding contribution.

The scientific community’s path to battery development

The advent of the Voltaic pile marked the beginning of the scientific research on batteries. As the first battery in human history, the Voltaic pile is a milestone. In 1836, British scientist Daniel innovated the Voltaic pile, using dilute sulfuric acid as the electrolyte, successfully solving the problem of battery polarization and creating the first zinc-copper storage battery that can maintain a stable current. The battery is named "storage battery" because it can be recharged and reused.

In 1887, the British Helleson invented the earliest dry cell battery, whose electrolyte was in a paste form, avoiding leakage and being easy to carry, so it quickly became widely used. In 1890, Edison further promoted the development of battery technology by inventing the rechargeable iron-nickel dry cell battery, bringing battery research and development into a new stage.

With the advancement of technology, the dry cell family has continued to grow, and more than 100 types have been developed so far, including but not limited to zinc-manganese dry cells, alkaline zinc-manganese dry cells, zinc-silver oxide batteries, and lithium-manganese batteries. These dry cells are essentially improvements on the voltaic pile. They use ammonium chloride paste instead of the original salt water, use graphite rods instead of copper plates as the positive electrode, and continue to use zinc foil as the negative electrode.

In his later years, Volta still emphasized: "Without Galvani's frog experiment, there would be no Voltaic current. When using Voltaic current, people should first remember Galvani. It was his frog experiment that illuminated my path to wisdom like lightning."

Reference sources: Science Popularization China, "Youth Encyclopedia Knowledge"