Chances are you might have at least two lithium-ion batteries on your body right now – one on your wrist, and one in the phone in your pocket. You may have multiple more if you’re holding a car key fob or have a pacemaker or any other electronic device.
But do you know how those batteries actually work?
For a technology at the heart of modern life, batteries remain something of a mystery. While humans have used batteries for hundreds of years, it’s only within the past decade that the science of batteries has advanced enough to make long-range electric vehicles like the Volkswagen ID.4 electric vehicle possible. Among all alternatives, researchers suggest that battery-powered vehicles hold the promise today of reducing carbon emissions from personal vehicles enough to help make significant progress against climate change. And Volkswagen hopes to have the next evolution of these batteries powering its vehicles within a few years.
Batteries rely on basic chemistry to work, formulas that were first identified by Alessandro Volta in 1799. Basically, every battery cell has two electrodes – one positive (the cathode), one negative (the anode) – and a substance in between called an electrolyte. When connected to an electric circuit, electrons move from the anode to the cathode through the electrolyte, while ions move in the opposite direction, creating electric current. In rechargeable batteries, the process reverses.
It wasn’t long after the invention of the early batteries that people began experimenting with vehicles built around them. In the early years of the auto industry at the turn of the 20th century, EVs were among the best-sellers, thanks to their quiet operation, ease of driving and low maintenance needs around newly paved cities. Only when roads improved and gas vehicles became more affordable did the first EV era end, aided by the increasing prevalence of gasoline stations, the lack of charging options for batteries, and the short range of early EVs.
The modern revival of EVs was made possible by lithium-ion batteries, first invented in the 1970s, and Volkswagen’s own electric history shows how far EV batteries have evolved. In the early 1970s, Volkswagen built a handful of Microbus vans converted to electric power, using the lead-acid batteries that you find under the hood of gas-powered vehicles today. The tray of batteries in the floor provided 25 miles of range– and added 1,847 lbs. of weight. Today, the largest lithium-ion battery pack in the Europe-only ID.3 EV holds nearly four times as much energy (82 kWh) at a third of the weight.
And the battery lies at the heart of why EVs are considered by experts to be one of the best choices for vehicles that combat climate change. Liquid fueled vehicles only use about a third of the energy it contains to move the vehicle – the rest escapes as heat and friction, and it generates carbon dioxide when burned. Similar waste happens with alternative fuels, from ethanol to hydrogen. But according to the EPA, EVs typically convert over 75% percent of their energy to movement and, if charged with renewable energy, have zero direct emissions in use.
Most EV owners will never see the batteries that power their vehicles. In the Volkswagen MEB electric vehicle platform, the batteries are built into the floor, for optimal weight distribution. EV batteries – like those in the upcoming ID.4 electric vehicle – aren’t one huge cell. It’s a modular package, where flat, individual “pouch” batteries are stacked 24 to a “module,” with up to 12 modules then connected into a single unit like the squares of a chocolate bar.
There are multiple reasons for building EV batteries this way. Smaller cells carry more energy per pound. It can be easy to add or subtract battery modules to offer EVs with different ranges and prices. Most importantly, as each individual battery can be controlled through software, it can be easier to maximize power flow and battery life, helping ensure a steady delivery of energy as the batteries discharge.
These systems can store and deploy tremendous amounts of electrical power. A typical cell phone battery runs at 3.7 volts; the battery pack in Volkswagen’s MEB electric vehicle platform operates at up to 408 volts. This helps allow the ID.4 EV to provide ample energy to its electric motors and power all the internal accessories, including heating and air conditioning.
Battery power for vehicles comes with some drawbacks. EVs simply don’t hold as much energy as a liquid-fuel vehicle and therefore have shorter ranges. It can take hours to recharge a large battery pack with a home 110-volt supply, and although there are fast charging options, everyday use of high-power charging can degrade EV cells. And EV batteries are the most expensive component in the vehicle.
Volkswagen Group has started to tackle these challenges with battery innovation start-up QuantumScape, and the concept of the solid-state lithium battery. Today, most lithium-ion batteries use either a liquid or gel electrolyte. A solid electrolyte could in theory create a battery that holds more energy per pound, at a lower cost, with fast recharging times in normal use. Volkswagen Group has invested approximately $300 million with QuantumScape since 2012 to research and develop such batteries, toward the goal of bringing the technology to market over the next few years.