How Lithium-ion battery Works?
In this post, we are not going to talk about any electric car, but about the heart of an electric car that is power source means battery-pack.
How Lithium-ion battery pack?
The versatile power supply has turned into the lifesaver of the cutting edge mechanical world particularly the lithium-ion battery. Imagine a world where all cars are driven by induction motors and not internal combustion engines, internal combustion engines induction motor is far better than IC motors in practically all building angles just as being increasingly powerful and less expensive another gigantic hindrance of IC motors is that they just produce usable torque in a limited band of motor rpm considering these variables acceptance engines are unquestionably the ideal decision for a car.
However, the power supply for an induction motor is the real bottleneck in achieving a major induction motor revolution in the automobile industry. How about if we investigate how Tesla with the help of lithium-ion cells understood this issue and why lithium-particle cells will turn out to be shockingly better later in future, let’s take a Tesla cell out from the battery pack and separate it you will see various layers of a chemical compound inside it. Tesla’s lithium-ion battery takes a shot at a fascinating idea related with metals called the electrochemical potential, electrochemical potential is the tendency of a metal to lose electrons in fact the very first cell developed by Alessandro Volta more than two hundred years ago was based on the concept of electrochemical potential a general electrochemical series is shown here according to these values lithium has the highest tendency to lose electrons and fluorine has the least tendency to lose electrons Volta took two metals with different electrochemical potentials in this case zinc and silver made an outside progression of power Some made the main business model of a lithium-ion battery in 1991.
It was again based on the same concept of electrochemical potential lithium which has the highest tendency to lose electrons was used in lithium-ion cells, lithium has only one electron in its outer shell and always wants to lose this electron due to this reason pure lithium is a highly reactive metal it even reacts with water and air the trick of a lithium-ion battery operation is the fact that lithium in its pure form is a reactive metal but when lithium is part of a metal oxide it is quite stable assume that somehow we have separated a lithium atom from this metal oxide this lithium atom is highly unstable and will instantly form a lithium-ion and an electron.
Anyway, lithium as a piece of metal oxide is considerably more stable than this state. If we can provide two different paths for the electron and lithium-ion flow between the lithium and the metal oxide the lithium atom will automatically reach the metal oxide part, during this process we have produced electricity from the electron flow through the one path from this discussion, it is clear that we can produce electricity from this lithium metal oxide if we first separate out lithium atoms from the lithium metal oxide and secondly, manage the electrons lost from such lithium molecules through an outer circuit.
Let’s see how lithium-ion cells achieve these two objectives a practical lithium-ion cell also uses an electrolyte and graphite, graphite has a layered structure these layers are loosely bonded so that the separated lithium ions can be stored very easily. There the electrolyte between the graphite in the metal oxide acts as a guard, which allows only lithium ions through. Now let’s see what happens when we connect a power source across this arrangement the positive side of the power source will obviously attract and remove electrons from the lithium atoms of the metal oxide these electrons flow through the external circuit, as they cannot flow through the electrolyte and reach the graphite layer in the meantime the positively charged lithium ions will be attracted towards the negative terminal and will flow through the electrolyte lithium ions also, reach the graphite layer space and get trapped there once all the lithium particles arrived at the graphite sheet the cell is completely energized in this manner we have accomplished the first objective. Which is the lithium ions and electrons detached from the metal oxide as we discussed this is an unstable state.
As if being perched on top of a hill as soon as the power source is removed and a load is connected to the lithium ions want to go back to their stable state as a part of the metal oxide due to this tendency, the lithium ions move through the electrolyte and electrons via the load just like sliding down a hill thus we get an electrical current through the load.
Please note that the graphite does not have a role in the chemical reaction of the lithium-ion cells.
Graphite is just a storage medium for lithium ions, if the internal temperature of the cell rises due to some abnormal condition the liquid electrolyte will dry up and there will be a short circuit between the anode and cathode and this can lead to a fire or an explosion, to avoid such a situation an insulating layer called the separator is placed between the electrodes the separator is permeable for the lithium ions because of its microporosity.
In a practical cell the graphite and metal oxide are coated onto copper and aluminum foils. The foils only collect current and the positive and negative tabs can be effectively taken out. From the current collectors, an organic salt of lithium acts as the electrolyte and it is coated onto the separator sheet all these three sheets are wound onto the chamber around a core steel center, along these lines making the cell progressively compact.
A standard Tesla cell has a voltage of somewhere in the range of 3 and 4.2 volts. Many such Tesla cells are connected in series and in a parallel fashion to form a module 16. Such modules are connected in series to form a battery pack. In the Tesla car, lithium-ion cells produce a lot of heat during the operation and high temperatures will decay the performance of the cell.
A battery management system is used to manage the temperature state of charge voltage protection and cell health monitoring of such a huge number of cells glycol-based cooling technology is used.
In a Tesla battery pack, the BMS adjusts to the glycol flow rate to maintain the optimum battery temperature. Voltage assurance is another pivotal activity of the BMS, for instance in this three cell, during charging, the higher capacity cell will be charged more than the rest. To tackle this issue the BMS utilizes something many refer to as cell balancing. In cell balancing all the cells are allowed to charge and discharge equally thus protecting them from over and under-voltage. This is the place Tesla scores over Nissan battery technology.
The Nissan Leaf has a huge battery cooling issue because of the enormous size of its cells and the absence of an active cooling method. Multiple cell design has one more advantage during high power demands the discharge strain will be divided equally among each of the cells, instead of many small cells.
If we had used a single giant cell it would have been put under a lot of strain and eventually, it would suffer a premature death by using many small cylindrical cells, the manufacturing technology of which is already well established. Tesla unmistakably settled on a triumphant choice there is an enchanting wonder which happens within lithium-ion cells during their very first charge, which saves the lithium-ion cells from sudden death.
Let’s see what it is the electrons. In the graphite, layer is a major problem the electrolyte will be degraded. If the electrons come into contact with it.
However, the electrons never come into contact with the electrolyte. Due to an accidental discovery the solid electrolyte interface, when you charge the cell for the first time, as explained above the lithium ions move through the electrolyte. Here in this journey solvent molecules in the electrolyte cover the lithium ions when they reach the graphite. The lithium ions along with the solvent molecules react with the graphite and form a layer they’re called the sei layer.
The formation of this sei lair is a blessing in disguise. It prevents any direct contact between the electrons and the electrolyte thus saving the electrolyte from degradation. In this general procedure of the development of the sei layer, it will expend 5% of the lithium the staying 95% of the lithium adds to the fundamental working(to provide power) of the battery. Even though the sei layer was an accidental discovery with over two decades of research and development scientists have optimized the thickness and chemistry of the sei layer for maximum cell performance.
It is amazing to find out that those electronic gadgets we used around two decades back did not use lithium-ion batteries with its amazing speed of growth. The lithium-ion battery market is expected to become a $90 billion annual industry within a few years. The currently achieved number of charge-discharge cycles of a lithium-ion battery is around three thousand. Great minds across the globe are putting their best efforts to increase this to ten thousand cycles. That means you would not have to worry about replacing the battery. In your car, millions of dollars have already been invested in research into replacing the storage medium graphite with silicon. If this is successful the energy density of the lithium-ion cell will increase by more than five times.
Here we discussed how lithium-ion battery works and how we can boost the performance of this battery. We also looked at how Tesla is utilizing Lithium-ion batteries in Tesla electric cars.