1. What Is the Difference Between Disposable and Rechargeable Batteries?
Batteries come in two types: those that are used once and thrown away, and those that can be recharged and reused. The first are called primary batteries, and the second are secondary batteries (also called rechargeable or storage batteries). A primary battery is one that cannot be recharged and used again after it has discharged its energy [1]. A secondary battery is a storage battery that has "reversibility," meaning it can return to its original state after being used [1].
It is important to note that thinking of charging only as "storing electricity" explains only half the story. The materials inside the battery that changed during discharge are returned to their original state during charging [1]. Imagine rolling a ball down a hill to use it, and carrying it back up the hill to recharge it. However, inside a real battery, it is not a ball but materials and ions that are moving.
So, when was this "returnable" battery born?
2. How Did Inventors Get From the First Battery to the Rechargeable Battery in About 60 Years?
Volta’s battery was disposable. Around 1800, Volta invented a battery by placing a copper positive electrode and a zinc negative electrode into a liquid of dilute sulfuric acid. This is considered the first primary battery, or disposable battery [2].
Rechargeable batteries appeared in 1859. The first secondary battery that could repeat charging and discharging is said to be the lead-acid battery invented by Planté in France in 1859 [3]. Since Volta’s battery was from around 1800 and the lead-acid battery was from 1859, batteries were "use it and done" tools for about 60 years. However, because sources use the phrase "is said to be," please read this number as an estimate.
So, what was happening inside Planté’s battery that was different from Volta’s?
3. How Do Lead-Acid Batteries Recharge by Changing Materials and Changing Them Back?
In a lead-acid battery, when it discharges, the materials at both the positive and negative electrodes change into lead sulfate. When it charges, the reverse reaction occurs, and they return to their original materials [3].
This is the difference from disposable batteries. Even after use, there is a path back to the original state. In the ball example, it is like being able to carry the ball that rolled down the hill back up to the top. Lead-acid batteries are still widely used today, for example, to start car engines [3]. This means this battery has been in use for more than 160 years since its invention in 1859.
So, what about batteries for smartphones and computers? In lithium-ion batteries, the way they "return" is even clearer.
4. How Do Lithium-Ion Batteries Recharge by Moving Ions Back and Forth?
In the explanation for the 2019 Nobel Prize in Chemistry, the Royal Swedish Academy of Sciences states that the advantage of lithium-ion batteries lies in the fact that they rely on lithium ions moving back and forth between the negative and positive electrodes, rather than on chemical reactions that destroy the electrodes [4]. In lead-acid batteries, materials changed into lead sulfate, but here, it is ions that move, traveling between the electrode materials.
The direction reverses when charging and using. When charging is complete, lithium ions are gathered on the negative electrode side. When discharging, the ions move to the positive electrode side, and electrical energy can be extracted. During charging, the current flows in the opposite direction, and electrons and lithium ions move out from the positive electrode [5]. It is easy to imagine if you think of ions traveling back and forth like students moving between a classroom and the schoolyard. However, ions are invisible and move in and out of the gaps in the electrode materials.
Why lithium? Lithium is the lightest metal and has a high tendency to ionize, so it can provide high voltage in a small, lightweight package [5]. This seems to be one reason it is suitable for portable devices.
So, how were electrodes that allow ions to move in and out discovered?
5. How Did Lithium-Ion Batteries Go From Lithium Metal Anodes to Hundreds of Recharges?
In the 1970s, Whittingham made a high-energy battery using titanium disulfide for the positive electrode, with gaps that could trap lithium ions. However, the negative electrode was lithium metal, which was prone to explosion and not suitable for practical use [4].
In the 1980s, Goodenough showed in 1980 that cobalt oxide containing lithium ions could produce up to 4 volts [4]. Then, in 1985, Akira Yoshino completed the basic structure of the lithium-ion battery by using lithium cobalt oxide for the positive electrode and changing the negative electrode from polyacetylene to a carbon material [6]. The Nobel committee states that this was the first practical battery, using a carbon material called petroleum coke for the negative electrode [4].
It could be charged hundreds of times. The Nobel committee states that Yoshino’s battery could be charged hundreds of times before its performance dropped [4]. Commercialization began with Sony in 1991, and also progressed with a joint venture of Asahi Kasei and Toshiba from 1992 onwards [6]. It took 126 years from the lead-acid battery of 1859 to the basic structure of 1985.
6. Why Can't Rechargeable Batteries Be Used Forever Even Though They Last Many Charges?
Akira Yoshino states that the "memory effect" (where voltage drops if you recharge without using it all the way), which was a problem in other secondary batteries, is almost non-existent in lithium-ion batteries [7]. This was a statement made in an interview.
However, degradation is not absent. It is said that repeating the use of discharging to 0% and charging to 100% causes degradation [5]. The Sakai City Fire Department warns that handling such as leaving them in a hot car interior poses a risk of heat generation and fire [8]. Even "returnable" batteries have lifespans that change depending on how they are used.
7. How Can You Sort the Batteries in Your Home Into Disposable and Rechargeable?
Let’s collect batteries from around your home. Look at batteries for remote controls, and the devices themselves like smartphones and game consoles. Check the labels on the batteries or devices, and the instruction manuals, for markings like "rechargeable."
Once found, sort them into disposable and rechargeable ones. Which group do remote control batteries fall into?
Do not take apart batteries or get them wet. Do not charge disposable batteries. In this note, we only looked at lead-acid and lithium-ion batteries. How other rechargeable batteries "return" is left as a question for next time. You can read about Akira Yoshino’s research path in Japanese on the Asahi Kasei special site [6].