Lithium-Ion Battery

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How it Works

A lithium-ion battery is made out of:

  • An anode
  • A cathode
  • A separator
  • An electrolyte
  • Two current collectors (positive and negative)

 The anode and cathode store the lithium, and when the charging or discharging process happens, the electrolyte carries positively charged lithium ions inside the battery through the separator. When the ions are released from the:

  • Anode to the cathode, the battery is discharging, and providing an electric current
  • Cathode to the anode, the battery is charging, and receiving an electric current

 When the ions are being released from the anode or from the cathode, a charge will be created in one of the current.

  • When the battery is discharging, the charge goes from the negative current collector to the positive current collector, through a device
  • When the battery is charging, the charge goes from the positive current collector to the negative current collector

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Batteries in Electric Cars

 In an electric car a battery is connected to one or more electric motors, which drive the wheels. When you press the accelerator, the car instantly feeds power to the motor, which gradually consumes the energy stored in the batteries.
 A typical 40kWh battery pack from a mainstream electric car might be enough to power it for 240 kilometres or more, while Tesla's biggest 100kWh battery is good for around 600 kilometres and can be recharged by a designated EV charging socket that is rated in kW from about 3kW up to about 50kW - or 120kW on Tesla's supercharger network. At a home or workplace, these sockets are either 3kW 'slow' units, or 7kW 'fast' chargers capable of recharging an EV in 6-12 hours

Battery Life

 It is normally said that a battery on an electric car is a proven technology that will last for years, and even car manufacturers confirm it.
 For example, Nissan and Tesla warrant that their electric car batteries will last eight years or 160,000 kilometres, but in an electric car, it's not good enough for a car designed to last many thousands of kilometres, so EV manufacturers go to great lengths to make electric car batteries last longer, by for example “buffering” where drivers can't use the full amount of power they store, additional spare capacity to compensate for degradation over time, reducing the number of cycles or by doing some clever cooling systems like Tesla.

Tesla's Cooling System

 In Tesla's battery, the coolant, which is made out of liquid glycol is distributed throughout the pack to cool the cells. But considering that every Tesla has a lot of cells to cool, this is a challenge. To get over this challenge, Tesla has a system that is based on a ribbon shaped metallic cooling tube that snakes through the pack.

Batteries Life Cycle

 When batteries do reach the end of their working life, they can be:

  • Recycled, which typically involves separating out valuable materials such as cobalt and lithium salts, stainless steel, copper, aluminum, and plastic. About half of materials of a battery are recycled, but as this technology keeps evolving, it is not the best solution
  • Repurposed, which could create a closed-loop system for recycling, meaning that the factories that produce the batteries could eventually be powered using the repurposed batteries once their lives powering vehicles comes to an end. It can also be fed back into the energy cycle for homes
  • Renovated to help power more vehicles in the future

Advantages

  • They are better for the environment, since lithium-ion batteries do not contain cadmium (a toxic, heavy metal) and release way less air pollution (zero tailpipe/exhaust emissions from the vehicle itself), although dumping any batteries into landfills is never a good thing
  • Lithium-ion batteries are more reliable than older technologies such as nickel-cadmium and do not suffer from a problem known as the "memory effect" (where nickel-cadmium batteries appear to become harder to charge unless they're discharged fully first)
  • They are relatively light for the amount of energy they store compared to heavy-duty rechargeable batteries (such as the lead-acid ones used to start cars)

Disadvantages

  • Despite considerable advances over the years rechargeable batteries still store only a fraction as much energy as ordinary gas; in more scientific words, they have a much lower energy density (they store less energy per unit of weight)
  • It takes hours to recharge an electric car, unlike gas-powered automobiles that can recharge (or in this case, refuel) in a few minutes
  • Li-ion batteries will catch fire if they are overcharged or if an internal malfunction causes a short circuit; in both cases, the batteries heat up in what's called a "thermal runaway," eventually catching fire or exploding
  • Battery cost is very expensive, despite decreasing in the past couple of years: at cell level the prices have fallen from about $700 per kilowatt-hour (kWh) in 2009 to about $150 to $175 per kWh today, according to Boston Consulting Group