The positive electrodes of these four types of batteries are lead dioxide, nickel hydroxide, nickel hydroxide and lithium cobalt oxide, while the negative electrodes are lead, cadmium, hydrogen storage alloy and graphite.

In addition to the above two categories, there is also a special existence in chemical batteries, which is the fuel cell, which uses hydrogen and other fuels to react with oxygen to produce electricity.

If hydrogen is used as fuel, then the reaction opposite to the electrolysis of water will occur to produce electricity, and the reaction product of hydrogen fuel cells is only water, so there is no pollution to the environment.

It is not difficult to understand the principle of physical batteries, biological batteries and fuel cells that generate electricity, so how do traditional chemical batteries generate electricity?

In simple terms, a chemical battery is a device that generates electricity through a chemical reaction.

The oxidation reaction releases electrons, while the reduction reaction gives electrons, these two reactions are carried out on different occasions respectively, and if they are connected with wires, the flow of electrons is produced in the wires, that is, an electric current is generated. In order for each reaction to occur at the positive and negative electrodes, there is an "electrolyte" around them. In addition, in actual batteries, in order to prevent short circuits between the positive and negative electrodes, the positive and negative electrodes are separated by an insulated separator.

Knowing this simple principle, we can make a simple battery by ourselves. “

Liu Yuan talked eloquently, roughly talked about the basic knowledge of the battery, looked at the time, 20 minutes passed, the rhythm was about the same, and then ordered a few classmates to come up and help open the box he brought.

When the students looked at it, they sighed, only to see that there were lemons inside, and they didn't know what Teacher Liu wanted to do.

I saw Liu Yuan take out a thin piece of copper and iron from the bag next to him, insert them into the lemon respectively, connect them with wires, and connect them with a small light bulb and switch in the middle, after the series was completed, Liu Yuan said mysteriously, "Students, the next time is to witness the miracle." ”

I saw him press the switch, the light bulb shimmered, and the students let out a low cheer.

"Do you know how it works?"

Everyone shook their heads collectively.

"Lemons have acids in them that dissolve a small part of aluminum, which releases electrons on the wire, while copper gets electrons from the wire, which creates a weak electric current on the wire. The negative electrode of this battery is an aluminum sheet, the positive electrode is a copper sheet, and lemon juice is the electrolyte. ”

Liu Yuan asked the students back to their seats, and then said, "The textbook says that different chemical batteries have different voltages, so what is the reason for this?

This is because the ease of releasing electrons or obtaining electrons varies with different substances, and the voltage of the battery is determined by the ease with which electrons are released and how easy it is obtained.

Substances that are easy to release electrons include lithium, potassium, calcium, sodium, magnesium, aluminum, zinc, etc., in order of ease, while substances that are easy to obtain electrons include gold, platinum, silver, mercury, copper, etc., from high to low.

Everyone who has studied chemistry knows that the metal selected for the negative electrode is as lively as possible, and the metal selected for the positive electrode is as dull as possible, and the greater the difference in the ionization tendency of the positive and negative electrode metals, the more a large number of electrons move at the same time, and the higher the voltage battery can be manufactured.

Now our common dry batteries are zinc-manganese dry batteries and alkaline dry batteries. The similarity between the two batteries is that their electrodes are made of zinc and manganese dioxide. So, both batteries have a voltage of 1.5V.

The above two types of dry batteries use manganese dioxide as the positive electrode and zinc as the negative electrode. The negative electrode of the battery is a paste of zinc particles mixed with a potassium hydroxide solution as an electrolyte, where zinc releases electrons and becomes ions.

At the positive electrode of the battery, manganese dioxide gains electrons and hydrogen ions to form basic manganese oxide. In this way, electrons flow from the zinc side, where electrons are easily released, to the manganese dioxide, where electrons are easily obtained, and an electric current is generated.

However, alkaline dry batteries process the zinc on the negative electrode into a paste, which greatly increases the surface area of the negative electrode, so that a large current discharge can be carried out, thereby improving the performance of the battery. In addition, alkaline dry batteries use an alkaline solution that conducts electricity easily in the electrolyte, so compared to zinc-manganese dry batteries, alkaline dry batteries are characterized by efficient current generation and slow voltage drops.

As a result, even if two batteries use the same material, their performance can vary greatly depending on the electrode shape and configuration.

Rechargeable batteries began in 1959 with the invention of lead-acid batteries by French physicist Gaston Plant. Subsequently, nickel-cadmium batteries, nickel-metal hydride batteries, and lithium-ion batteries in secondary batteries were also developed one after another. Especially after the advent of the wireless era, such as mobile phones, laptops and even drones have been popularized, which is indispensable for the application of secondary batteries.

At the time of the birth of mobile phones, they were loaded with nickel-cadmium batteries, which were later replaced by nickel-metal hydride batteries, and now all mobile phones have been replaced with lithium-ion batteries. It can be said that with the advancement of batteries, the popularization of portable appliances such as mobile phones, laptops, drones and even electric vehicles has become possible.

Nickel-cadmium batteries have a voltage of about 1.2V, and because they are capable of high-current discharge, they are usually used for short-term use such as rechargeable shavers and electric toothbrushes.

The subsequent nickel-metal hydride battery also had a voltage of 1.2 V, but its capacity was twice that of nickel-cadmium batteries, so the emergence of nickel-metal hydride batteries made a small contribution to the miniaturization of electrical equipment at that time.

However, nickel-cadmium batteries also have a big disadvantage, that is, the cadmium used in nickel-cadmium batteries is very toxic, so most of them are now replaced by nickel-metal hydride batteries.

NiMH batteries, as the name suggests, are hydrogen as the negative electrode and nickel as the positive electrode. At the negative electrode of the battery, the hydrogen stored in the hydrogen storage alloy loses electrons and becomes hydrogen ions, while at the positive electrode of the battery, the basic nickel oxide binds to hydrogen ions and gains electrons. The separator of a nickel-metal hydride battery is a thin plate that prevents the metal powder at the electrodes from moving. At the same time, in order to move the ions, a solution of potassium hydroxide as an electrolyte is infiltrated into the separator. In this way, hydrogen ions are transferred between the negative and positive electrodes, enabling charging and discharging.

At present, there are many brands of nickel-metal hydride batteries on sale, and it is one of the most common secondary batteries around us. Because the current model is almost the same as the dry battery, nickel-metal hydride batteries are increasingly replacing alkaline dry batteries and zinc-manganese dry batteries.

Next we talk about lithium-ion batteries. Lithium-ion batteries use lithium cobalt oxide for the positive electrode and carbon for the negative electrode. Lithium ions are transferred between the layered carbon and the layered lithium cobalt oxide to charge and discharge. When discharged, the lithium in the negative electrode emits electrons and becomes lithium ions, and the lithium ions move to the positive electrode to get the electrons to be intercalated, so that an electric current is generated. The opposite reaction occurs when charging.

Lithium-ion batteries are smaller than nickel-metal hydride batteries but have a larger capacity, and because lithium is the metal with the greatest tendency to ionize and is also the lightest weight, it is considered to be an essential anode element for high-voltage, miniaturization, and light-weight batteries.

The voltage of lithium-ion batteries is three times higher than that of nickel-metal hydride batteries, so a mobile device that can be driven by a few nickel-metal hydride batteries may only need one lithium-ion battery to use. Nowadays, mobile phones, digital cameras, and laptops are all miniaturized and lightweight, and it can be said that they are all due to the invention of lithium-ion batteries.

People did not use lithium-ion batteries at the beginning, and there was a twist and turn in the middle, at first people directly used lithium as the negative electrode, but because the activity of lithium metal is very strong, only a little amount of lithium is needed, and after contact with water, it will heat up violently, and at the same time, hydrogen will be generated, causing fire hazards. As a result, primary batteries that use lithium metal as the anode have been on the market for about 40 years, but their use in secondary batteries is considered dangerous and not feasible.

If lithium metal is applied to the negative electrode of a secondary battery, fine whisker-like lithium crystals will form on the surface of the negative electrode during charging, and this crystal is easily connected to the positive electrode to produce a short circuit. If this problem is not addressed, it can become the cause of battery heating and even fire.

However, the fate of a battery also has to take into account the course of history, in the 80s of the last century, with the portability of digital cameras and the emergence of mobile phones, the development of batteries that can be charged and discharged multiple times, high energy density has become an inevitable requirement of history. Thus, lithium-ion batteries were born.

The emergence of lithium-ion batteries originated from Dr. Akira Yoshino of Asahi Kasei Co., Ltd. in Japan, who first considered how to use the conductive plastic polyacetylene as the negative electrode of the battery, and in order to make polyacetylene as the negative electrode of the battery and create a high-performance lithium secondary battery, it is necessary to add lithium to the positive electrode, but how to join, Akira Yoshino has no good way.

In 1982, Japanese scientist Koichi Mizushima published a paper on the cathode material embedded in lithium, which is lithium cobalt oxide, which is the material that Akira Yoshino has been looking for. So, with this cathode material as a breakthrough, Akira Yoshino thought of the prototype of the current lithium-ion battery.

In the developed lithium-ion battery, an organic solvent is used instead of an aqueous solution for the electrolyte, and lithium atoms are embedded in carbon instead of lithium metal at the negative electrode, thereby suppressing the activity of lithium and improving the safety of the battery.

However, there are risks associated with the use of organic solvent electrolytes. Organic solvents burn when exposed to high temperatures, so if a short circuit occurs inside the battery, the temperature rises and the battery will catch fire. In addition, even now, it is not uncommon for mobile phone batteries to swell, which is caused by the formation of gases inside the battery.