How does 1865 lithium battery store electricity?

You must have imagined that you would peel away the lithium battery cells and see what is inside. Of course, it is very dangerous to do so. We can show everyone the internal structure of the lithium battery by simulation. After the battery is opened, you can clearly see the material and structure of the internal structure. Its positive electrode is made of metal aluminum, and the negative electrode is made of metal copper. There is electrolyte and graphite in between, and there is a diaphragm between the two electrodes. This is the basic structure of a 18650 cylindrical battery. The reason why lithium batteries choose the metal element lithium as the core material is because lithium is a relatively active metal in the periodic table and is easier to lose electrons. Therefore, using lithium as a battery material can increase the cell voltage. Lithium ions in the electrolyte (lithium in ionic state) must flow adequately in the battery, but the electrons must be isolated, otherwise it will cause a short circuit. In the uncharged state, both lithium ions and electrons are bound to one end of the positive electrode, and the lithium ions will form a compound with the positive electrode material. At this time, it is in a stable state, but the battery itself does not have any potential energy. Once the battery is charged, the electrons will move to the negative stage with the use of the external power source and be stored in the negative stage material. Lithium ions will also be attracted to the negative stage material for storage through the separator. In a state of high potential energy (that is, a charged state). The negative grade material is made of graphite. Because graphite has a fluffy porous structure, it can confine electrons. What happens in the negative stage is not a chemical reaction, but a physical reaction. Lithium ions and electrons do not form compounds in the negative stage. Instead, they are bound by physical means, resulting in potential energy. Once the battery is connected to an external load, electrons will flow into the positive electrode along with the wire to drive the load to do work. At this time, lithium ions will also return to the positive electrode material through the separator. In the cathode material, lithium ions and electrons meet again to form a stable compound. Of course, if the separator between the positive and negative electrodes loses its insulation purpose, the electrons running straight from the inside of the battery to the positive electrode will form a short circuit, which will cause an explosion. Therefore, the stability of the separator plays a vital role in the safety of lithium batteries. Diaphragm is a kind of chemical material. It has two important characteristics: it can be insulated (to prevent electrons from passing through) and breathable (to allow lithium ions to pass smoothly). When the battery cell starts to work, as the lithium ions migrate left and right through the separator (the process from positive to negative, from negative to positive), a SEI passivation layer will be formed on the negative side of the separator. The chemical layer can make the battery more stable, and the research and development personnel have calculated the optimal thickness through a large number of experiments. This process probably consumes about 5% of lithium ions, so it will affect part of the battery capacity. In the 18650 battery, the negative electrode is made of copper, and the positive electrode is made of aluminum. Graphite is applied to the positive electrode material, and then the lithium compound is applied to the negative material to form an electrode. ▲ Insert the diaphragm between the electrodes to form the prototype of the lithium battery, then curl the electrode and the diaphragm into a cylindrical shape, add electrolyte, and then seal it to form the cylindrical 18650 lithium battery we want. The discharge voltage of the 18650 battery is 3V to 4.2V. During the heavy discharge process, the voltage will also decrease. Once the cell voltage is lower than 3V, there is a risk of damage. So we need a battery management system to protect each battery cell from being overcharged and discharged. This system is called BMS for short. A set of BMS control system is equipped in each battery pack composed of single cells. Since the ambient temperature has a great influence on the charging and discharging of the battery, it is necessary to design a cooling system to allow so many battery cells to work at the same temperature as possible. Tesla uses ethylene glycol as the cooling medium, which is what we commonly call the water cooling system. This system can ensure that the temperature of each battery cell is as consistent as possible, thereby ensuring that the degree of charge and discharge is as consistent as possible. Nissan LEAF uses a soft-pack battery cell. Its electrodes are not crimped, but are stacked straight. The principle is the same as the cylindrical battery cell analyzed above, except that the external shape looks different and the physical characteristics are also different. There are some differences. Tesla ModelS uses a battery pack composed of cylindrical cells. When the soft-pack-shaped battery cell is designed as a battery pack, the gap between the cell and the cell is smaller. Therefore, under the same charged condition, the volume of the soft pack battery is smaller. The space utilization rate is higher, which is convenient for the general layout of electric vehicles. And the soft-packed battery cell has better safety performance against puncture than the cylindrical battery cell. Of course, the cylindrical battery has a relatively high energy density due to its crimping process, and the arrangement of a glycol water cooling system between the cells can make the battery work more stably. The 21700 cells used in Tesla's new Model 3 are still cylindrical. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.