Based on market forecast, the sales of electric vehicles (EVs) are forecast to grow steadily over the next decade, while efforts to combat climate change also involve phasing out gasoline-powered vehicles. The development of electric vehicles has benefited from rechargeable batteries, which are also the basic system for using clean and renewable energy. Electric vehicles use the powertrain battery to power all engine components to perform their intended functions.
What is the current situation of EV?
The environmental cost of producing electric vehicle powertrain batteries has proven to be high, but sadly, only a few automakers are taking the issue seriously. The raw material used to make these batteries is lithium and its variants. These variants include cobalt-nickel, manganese, and several other materials. The material that dominates the market is cobalt-manganese, which is used by many electric vehicle companies.
But Tesla, on the other hand, uses a combination of lithium cobalt and manganese. Some automakers are developing a new cobalt-free powertrain, but cobalt remains an important mineral without which electric vehicle powertrains will be difficult to manufacture.
Lithium-ion batteries are widely used in portable consumer electronics such as smartphones and laptops. They are also used in electric vehicles due to their higher energy density than lead-acid or nickel-metal hydride batteries. This advantage allows automakers to develop smaller batteries without sacrificing storage capacity. Lithium-ion batteries also feature a high power-to-weight ratio, high energy efficiency, high-temperature performance, and low self-discharge. Additionally, individual components of lithium-ion batteries can be recycled, making them an environmentally friendly option.
How do lithium-ion batteries work?
Lithium-ion batteries work by an electrochemical reaction in which electrons are transferred between two electrodes, one of which is negatively charged and the other is positively charged. The electrodes are immersed in a conductive electrolyte that facilitates the movement of charged ions between the electrodes.
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How does lithium-ion battery charging work?
Lithium-ion cells have intercalation compounds, which are characterized by a layered crystal structure that allows the migration or deposition of lithium ions. When charging a Li-ion battery, ions move from the positive electrode to the negative electrode and wait for the next discharge cycle.
The latest generation of batteries has enhanced ion mobility, allowing for faster charging without the associated risk of overheating. To this end, chipmakers have developed a range of integrated solutions for Li-ion battery management to simplify charger design. These companies now offer chips that allow engineers to design products that take advantage of the constant-current phase to accelerate charging.
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How does lithium-ion battery discharge work?
During discharge, ions move from the negative electrode to the positive electrode through the electrolyte, while electrons flow from the negative electrode to the positive electrode through an external circuit that powers the electronic device. The combination of ions and electrons on the positive electrode leads to lithium deposition. Once all ions have returned to the positive electrode, the battery is fully discharged and needs to be recharged.
During an EV’s discharge, the battery’s stored energy is depleted, and the battery’s voltage drops as current flows from the battery to the motor. The rate of discharge depends on the power demand of the motor and the capacity of the battery, which determines how much energy the battery can provide before it needs to be recharged. Efficient battery discharge is critical to optimizing the range and performance of electric vehicles.
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The formula of lithium-ion battery capacity
The battery charging equation is expressed in terms of battery capacity. It depends on the value of the battery’s rated capacity (in ampere hours, Ah) and the time to reach this value. The equation is defined as:
I = M x Cn
Among them, I is the charging or discharging current in ampere, M is the coefficient of C, C is the value of the rated capacity, and n is the time to determine C.
Some industry standards for electric vehicle batteries
The current industry standard for electric vehicle battery development is the use of lithium-ion technology, which has advanced significantly over the past 30 years. Lithium-ion batteries offer superior energy density compared to other technologies, but they require precise control of the charging process and proper packaging. Currently, lithium-ion technology is considered the best choice for a balance of capacity, charging flexibility, and durability.
Although all-solid-state batteries have attracted a lot of attention, their development has not progressed enough to make them a major source of batteries for electric vehicles. Solid-state batteries aim to replace the liquid electrolytes of conventional lithium-ion batteries with solid-state materials, which can be in the form of polymers or inorganic powders such as ceramics.
The liquid electrolyte in lithium-ion batteries can permeate both the cathode and anode. High temperatures accelerate the chemical degradation of electrolytes, while the flammability of organic solvents can lead to system failures and fires. In contrast, all-solid-state batteries are less volatile and can remain stable and safe at high temperatures.
