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Mahesh

31/01/24 05:56 AM IST

Electric Vehicle Batteries

In News
  • Last year was a good year for Electric Vehicles (EV) in India with sales recording a 50% growth compared to 2022.
  • While actual volumes remain small (6% of vehicles registered in 2023), the industry is poised for phenomenal growth with the Indian EV market expected to reach $100 billion by 2030.
Lithium batteries
  • Almost all EVs on the road today are powered by lithium-ion batteries.
  • It consists of two electrodes (an anode and a cathode) separated by a liquid electrolyte
  • Lithium atoms in the anode give up electrons which travel to the cathode through an external wire — this stream of electrons provide the current which powers the motor of the vehicle.
  • Simultaneously, lithium ions (now positively charged from loss of an electron) travel through the electrolyte to reach the cathode.
  • During charging, the process is reversed with lithium ions being forced to travel back through the electrolyte to the anode.
Why lithium is important?
  • Lithium, the lightest solid element known to man, has a high propensity to give up its electron.
  • Its small size enables the lithium ion to efficiently travel between electrodes through the electrolyte.
  • This translates to lighter and smaller batteries with an ability to store large amounts of energy.
  • However, today’s Li-ion batteries still leave a lot to be desired. Its energy density while high compared to earlier battery technologies, pales in comparison to petrol.
  • Batteries are still slow to charge (compared to the few minutes it takes to fill petrol at a pump).
  • There is a need to make batteries more affordable and increase their life-span.
  • And then there are environmental concerns primarily related to the mining of lithium and other elements (such as cobalt, nickel).
Improving the battery
  • The first approach retains the basic structure of the lithium-ion battery while making tweaks to the electrodes.
  • An ideal electrode should be light weight; store a lot of lithium; provide sufficient pathways for lithium to easily enter and exit the electrode (translating to higher voltages and faster charging); and be made of materials that are cheap, non-toxic and easily available. But invariably there are trade-offs involved.
  • For example, Tesla uses cathodes based on Nickel-Manganese-Cobalt (NMC) and Lithium Iron Phosphate (LFP) in their batteries.
  • While NMC batteries have high energy density and thus provide longer range, LFP batteries have longer life, better stability, are less toxic and have faster charging times.
Battery Management Systems (BMS)
  • Another approach to improving battery performance involves deploying sensing and control infrastructure around the battery to increase safety, extend battery life and speed-up charging.
  • For instance, a temperature sensor can be installed to detect dangerous conditions and shut down the battery, preventing a fire.
  • Monitoring parameters such as internal temperature, voltage and current and appropriately modulating the charging current and voltage can result in faster charging while maintaining battery life.
  • This can be understood using a simple analogy. Charging a battery involves moving lithium ions from the cathode to the anode.
  • A Battery Management System (BMS) consists of sensors to measure parameters such as temperature, voltage and current; electronic circuitry to control the battery; and a compute engine to process the sensor data and issue appropriate control commands.
  • Advances in battery management and charging algorithms are generally easier to deploy since they do not involve any fundamental changes to the battery chemistry.
Solid state lithium batteries
  • The Solid-State Lithium Battery (SSB), which seeks to fix two common drawbacks in prevalent batteries.
  • The liquid electrolyte used in EV batteries is highly flammable. The SSB replaces this with a heat resistant lightweight solid electrolyte.
  • Further, the anode of an EV battery consists of a carbon based porous/layered scaffolding (typically graphite) — which houses lithium atoms (a crude analogy is water stored in a sponge). The carbon scaffolding provides the required stability during charging and discharging, as lithium is highly reactive.
  • However, the solid electrolyte in an SSB provides sufficient structural stability and good separation between the anode and the cathode, that the carbon scaffolding is no longer needed at the anode.
  • This can significantly reduce the weight of battery and also improve charging speed.
  • If SSB’s live up to their promise, consumers can expect EVs that travel further with a single charge, are faster to charge and are safer across a wider range of temperatures, sometime before the end of this decade.
Significance for India
  • India has a good eco-system that can support further progress in EV batteries — an expanding market, an environment that supports start-ups, friendly government policies, and successful home-grown EV companies (Ather, Ola Electric).
  • Further, fundamental research in material science at India’s premier universities (IIT- Madras and Mumbai) and government research labs promotes innovation.
  • The semiconductor industry in India (Texas instruments included) is also contributing advanced sensors and processors that will power the next generation of BMS.
Source- The Hindu

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