1. Foreword
How does the battery work? It's very simple, it just uses the chemical reaction between the acidic substance inside the battery and two different metals. One metal carries more electrons to form the negative electrode, and the other metal has fewer electrons to form the positive electrode.
So how to make the battery work? How does the battery generate current? In the process of teacher Kathy's explanation, you can learn that some materials are conductors and some are insulators, what is current, why all electrical experts and scientists maintain a common lie, the importance of free electrons and ions. It's all simple to understand through chemistry.
▲ Figure 1.1.1 Different batteries
2. Conductors and insulators
In order to explain the working principle of batteries and what current is, two terms need to be defined. Free electrons and positively charged ions. To do this we need to start with basic concepts.
Atom is composed of a positively charged and massive core, also known as nucleus , and a peripheral electron cloud with negative charge. The electron cloud is attracted and bound together by the nucleus.
▲ Figure 1.1.2 atomic clock ’s atomic nucleus and external electron cloud
These alone are not enough to explain current or electricity. However, for some atoms, they are not tightly bound to external electrons, and their electrons are relatively easy to break away from the constraints of the nucleus and move freely. This is called a free electron, which is pretty cool, right?
After losing some electrons, the atom consists of a positively charged nucleus and insufficient external electrons, thus forming a positively charged ion. These free electrons do not belong to any particular atom until they are recaptured, as do positively charged ions, which are atoms that have lost one or two electrons.
3. Current
Current is formed by flowing electrons, which is the definition of current. The speed of a single electron is not actually fast, but it can form a simultaneous flow of electrons moving in the same direction. There are many free electrons and ions in metals. Electrons can travel relatively easily between ions, making the material a conductor. Plastics have few free electrons and ions, so it is difficult for electricity to pass through them. They are called insulators. In a normal wire, the metal on the inside allows electricity to pass through, and the insulation on the outside prevents the electricity from reaching outside sources, such as your hands.
So how do you make electrons move in metals? All it takes is one battery. Any battery has a positive and negative terminal. A large number of electrons will accumulate on the negative electrode, and a large number of ions will be collected on the positive electrode. Opposites attract and likes repel, so electrons from the negative electrode will be repelled from the negative electrode and flow toward the attracted positive electrode. If an external wire is used to connect the negative terminal of the battery to the positive terminal, electrons can flow through the wire to the positive terminal.
▲ Figure 1.2.2 Wrong idea of current flow
By the way, let me tell you a fact that breaks the traditional concept. Normally we think of current flowing from the positive terminal to the negative terminal of the battery. This statement comes from Franklin 's definition of positive charge and negative charge. In 1745 he defined it arbitrarily and insisted that in a discharge electricity flows from the positive pole to the negative pole. It took 150 years before people discovered the existence of electrons. At that time, we had established corresponding equipment, teachings, and rules that current flowed from the positive pole to the negative pole. So in order not to change all the equipment and rules, the actual situation is no longer considered.
Whenever we talk about the direction of current flow, in reality it is the negatively charged electrons that flow in the opposite direction. It can be said that whether consciously or unconsciously, all science teachers and electronic engineers in the world are maintaining a common lie. Really incredible, right?
▲ Figure 1.3.2 The actual flow of current
4. Battery
But so far, how the battery works has not been discussed.How exactly does a battery generate and maintain the positive and negative electrodes? Each battery utilizes a chemical reaction between two metals and an acidic or alkaline substance. Acids tend to move electrons, and bases react with moving ions. This causes the reacting metal to either carry an excess of electrons to form a negative electrode, or lose electrons to form a positive electrode.
The earliest batteries were built in 1800 and consisted of silver and zinc sheets placed in a cup filled with salt water. Salt water acts as an acid here. This results in a weaker battery. The salt reacts with zinc, adding electrons to form a negative electrode. Reaction with silver removes electrons to form the positive electrode.
▲ Figure 1.4.1 Voltaic battery in 1800
Soon people used different metal sheets soaked in acid to make batteries. The lead-acid battery currently used in cars is composed of lead and lead oxide soaked in sulfuric acid.
Because acid is not a very convenient chemical substance to use, the acid can easily corrode the external container, and the acid liquid is also easy to spill. In 1899, people began to use alkaline substances to replace acid in batteries.
5. alkaline battery
Most contemporary batteries use alkali instead of acid to form batteries. There are many types of batteries available today. Let’s take a look at the structure of an alkaline battery. Substances in chemistry often have many aliases. For example, alkaline substances in acid-base reactions are called base, alkeline, etc. This can drive people crazy.
Alkaline batteries come in many specifications with different shapes and sizes. But the same metals inside participate in the same chemical reactions. The following shows the internal structure of a typical alkaline battery.
▲ Figure 1.5.1 Alkaline battery structure
In the center of the battery, there is metallic zinc mixed with some alkaline substances, such as potassium hydroxide. The periphery is manganese oxide . Potassium hydroxide reacts with metallic zinc, but the positively charged ions move out, leaving excess negatively charged electrons. Next, the chemical reacts with the manganese oxide, adding many ions, thus forming an excess of positively charged ions. The zinc and manganese oxide are separated by a layer of plastic, so electrons don't flow into the cathode and combine with ions. The electrons gather and repel each other, eventually converging on the central collector metal rod. This reaction continues on both sides until a strong electromotive force is formed, and the chemical reaction stops.
The common AA alkaline battery voltage is 1.5V. When the battery is connected to the circuit loop , electrons are triggered from the negative electrode to flow along the wire to the positive electrode of the battery, and the chemical reaction starts again, maintaining the internal electromotive force at 1.5V.
▲ Figure 1.5.2 Battery in the circuit
ˆ After the chemical substance reacts with the metal, the chemical substance gradually becomes weaker and weaker, and eventually loses the ability to react. After the ions in the zinc are consumed, the battery is scrapped.
6. Rechargeable battery
Alkaline batteries are disposable batteries and cannot be recharged repeatedly. Rechargeable batteries work similarly. The corresponding ions and electrons are moved through chemical reactions. The positive electrode carries more ions and the negative electrode carries more electrons. When the current flows in the opposite direction, the chemical reactions inside the rechargeable battery proceed in the opposite direction. The corresponding ions return to the original metal, and the alkali or acidic substances gradually become stronger.
Different batteries have different structures, chemical reactions and different metals. But they all contain acids or bases, two different metals or metal compounds , so that one side has excess negatively charged electrons and the other side has excess positively charged ions. This is how batteries work.
The chemical process here is very simple, right?
References
[1]
The Tamer of Lightning: The History of Electricity: https://zhuoqing.blog.csdn.net/article/details/128426612
