As an electric car owner, it is important that you check your vehicle hours before you start another journey on the road. As an energy-conscious and range-conscious kind of driver, you would check whether your unit still has enough juice to last a trip. In that aspect, you will realize that your electric vehicle’s battery is an integral part of your environment-friendly, hassle-free drive. You would choose a car model that comes not only with the latest technologies and new features, but also with a battery that powers your unit better than the leading brands.
The kind of batteries that are used to power most electric vehicles are lithium-ion (li-on) batteries, which is the fastest growing and most promising battery technology today. An eco-friendly alternative to lead acid batteries, lithium-ion has thrice the energy density of a standard lead acid battery. With a higher energy density potential, the longer-lasting and lightweight lithium-ion battery is able to release the same output of power. Lithium-ion is rechargeable and low on maintenance, and its cost is rapidly decreasing.
How lithium-ion batteries work
In a lithium-ion battery cell are four main components that are made out of different material compositions. Each component performs their specific functions:
- Cathode – Made of lithium metal oxide powder, the cathode emits lithium ion to anode during charging and receives lithium ion during discharging.
- Anode – The anode is made of graphite powder. It receives the lithium ion from cathode during charging and emit lithium ion during discharging.
- Electrolyte – The electrolyte passes the lithium ions between the cathode and the anode. This component is made out of lithium salts and organic solvents.
- Separator – This component prevents any short circuit between the cathode and the anode. This is where the lithium ions pass through pores. The separator is made of micro-porous membranes.
To create electricity flow for use in electronic applications, the lithium ions move between the anode and the cathode. The lithium in the anode is ionized and then emitted to the electrolyte in the discharge cycle. The lithium ions pass through the separator and insert into the holes in the cathode. Electrons, at the same time, are released from the anode, which becomes the electric current that travels to an outside electric circuit. In the charge cycle which is a reversible chemical reaction, the lithium ions go from the cathode to the anode. That way, the lithium-ion battery is recharged.
How lithium-ion came to power electric vehicles
The US is continuously developing renewable energy sources and alternative fuels to power its vehicles. The biggest focus is on electricity, which is now generated through wind and solar panels. Engineers are also looking at natural gas and hydrogen fuel to operate power grids to generate the electricity demand of electric vehicles. Why the switch from gasoline and other oil-based fuels to electricity? There are three main reasons:
- Reduce greenhouse gas emissions.
- Cut dependence on foreign oil exports.
- Keep and create more local jobs (by reviving its automobile sector with emphasis on electric vehicles and battery manufacturing).
All these have to do with electric vehicles which the federal and state governments are aggressively promoting through a plethora of financial incentives for car buyers and mandates for auto manufacturers. The success of electric vehicles will have to do with batteries, still its major Achilles’ heel. Scientists and engineers in the field of electric mobility are closer to developing an electric car battery that is safer, powerful, and more energy-efficient.
As mentioned earlier, most electric vehicles use lithium-ion batteries. As more car buyers are choosing electric units over vehicles that run on internal combustion engines, lithium-ion is projected to become the most popular battery of choice for plug-in hybrid and full-battery electric vehicles. Though lead acid and nickel metal batteries still retain considerable market share, lithium-ion batteries will dominate the market by 2017, according to the Deutsche Bank in 2009.
Why lithium-ion battery for electric cars? This is the same kind of battery that powers our mobile phones, tablets, laptops, and other consumer electronics. Lithium-ion has continuously evolved in its practical applications that now include electric cars. But keep in mind that the lithium-ion that powers consumer electronics is not the same as the one that powers electric vehicles. There are still differences in their applications.
The lithium-ion batteries that power consumer electronics are based on lithium cobalt oxide (LiCoO2) cathodes. Why they are not used in electric cars? They are susceptible to thermal runaway when accidentally overcharged or during high temperature operations. In other words, they catch fire. This kind of lithium-ion battery is not suitable for power-intensive applications, like electric vehicles. The lithium-ion in electric cars use lithium iron phosphate (LiFePO4) which has an energy density slightly lower than the LiCoO2, but is safer and longer-lasting. The non-combustible LiFePO4 mixing formula was developed two decades ago.
Advantages of lithium-ion for electric car
Lithium-ion batteries have several advantages over lead acid and nickel metal batteries for use by electric vehicles. Advantages include higher energy density, longer cycle life, high energy efficiency, and no memory affects (decrease in energy capacity after battery is discharged).
- Higher energy density – Range-conscious drivers would want a battery that runs a longer distance between charges while consuming more power. The lightweight lithium-ion is capable of storing more energy, thus making it the ideal battery for automotive use. Lithium-ion wastes no energy as it optimizes every amount of power it collects and stores in every square inch of wattage.
- Longer cycle life – A lithium-ion battery, when well cared for, could last between 2000 to 5000 charging cycles, better than lead acid and nickel-based batteries.
- Low self-discharge – Rechargeable batteries and cells lose their maximum energy capacity with every charge over time. The self-discharge rate of lithium-ion is much lower than that of nickel-based batteries.
- No priming necessary – Some rechargeable batteries require priming when they receive their first charge. Lithium-ion does not. One regular charge is all it needs.
- Zero maintenance – Unlike nickel-based batteries, lithium-ion does not require periodic discharge and other similar maintenance to ensure their performance. Like electric cars that hold them, lithium-ion batteries are basically maintenance-free and suffer no memory effects.
- Fast and efficient charging – Depending on your charger, a lithium-ion battery can be charged fast. And even if you fail to reach full charge, your battery would still work well. You can charge your electric vehicle up to what you can for a trip and never worry about an undercharged battery pack.
Disadvantages of lithium-ion batteries
As with every piece of technology, lithium-ion batteries are not without a couple of disadvantages.
- High production costs – High battery cost means high electric vehicle price. Lithium-ion batteries are 40% more expensive to manufacture than lead acid and nickel-based batteries. However, the cost is expected to decrease as lithium-ion is increasingly used in many applications.
- Protection requirement – Lithium-ion is much sensitive to how it is charged and discharged, so it requires a battery management system (BMS) to protect against overcharging and short circuits. This protection circuitry will ensure the battery maintains voltage and operate within safe limits.
- Aging – When not stored in proper conditions, lithium-ion batteries suffer a decrease in their energy capacity over time. This is why you keep your electric car in the garage during winter and outside the garage at summer.
- Safety issues – Lithium-ion batteries are vulnerable to overcharging and short-circuiting. Overcharging destroys the chemical structure of the cathode and the anode, and causes the lithium ions to form lithium metal deposits called dendrites, which can cause the lithium-ion battery to short circuit. When it does, high electric flows are created and the battery temperature is increased, heating up the neighboring cells and resulting to an explosion and/or fire.
