To move from fossil fuels to renewable energy, we need to be able to store electricity. Storage technology exists both for the grid and for home use. So far, most of it relies on lithium-ion batteries.
I have written that the vanadium flow battery is probably the future of storage. But households can’t use such gigantic batteries.
What alternatives to lithium-ion batteries can homeowners and businesses use?
Before we can move onto that question, we need to understand existing lithium technology.
How lithium-ion batteries work
I have written more generally about how batteries work elsewhere. When we talk of lithium batteries, whether to power a cell phone or store solar power, we mean a battery with multiple cells. The cells can either be cylinders like a standard AA battery or prismatic (square or rectangular).
Of the several kinds of lithium-ion batteries that exist, we most commonly use lithium carbon oxide batteries. Unless the context specifies otherwise, assume that lithium-ion means lithium carbon oxide.
Each cell has a positive electrode (cathode) of lithium cobalt oxide, a negative electrode (anode) of graphite (carbon), and an electrolyte.
Lithium ions pass through the electrolyte from negative to positive as you use the battery. They flow back from positive to negative when you charge it.
A lithium-ion battery pack requires a built-in computer. The computer
- monitors battery temperature
- maintains safe voltage and current levels
- controls the flow of electricity in and out of the battery pack
- monitors the energy capacity of each individual cell
- monitors the complete process of charging the battery pack
The computer displays how much charge is left in the battery. It automatically shuts off the flow of power if the battery pack gets too hot or comes close to discharging completely.
Advantages of lithium-ion batteries
The electrodes are made of lithium and carbon, two lightweight elements. Therefore, they are lighter than other batteries of the same size.
In addition, lithium-ion batteries have higher energy density than other rechargeable batteries. They store at least half again as much electricity as nickel-metal hydride batteries and six times as much as lead-acid batteries.
A fully charged nickel-metal hydride battery loses 20% of its charge per month. A lithium-ion battery loses only 5%.
And you can recharge lithium-ion batteries hundreds of times before they wear out.
Some rechargeable batteries must discharge completely before they can recharge, but not lithium-ion—which is both and advantage and a disadvantage.
Disadvantages of lithium-ion batteries
Lithium-ion batteries don’t maintain charge very long, so must be recharged frequently. And don’t let them discharge completely. It ruins them.
They degrade quickly and last only two or three years after they come off the assembly line. Even if you don’t use them at all. They degrade even faster in heat.
Mining this relatively rare metal has negative environmental consequences. Lithium has many other uses besides making batteries. As demand for lithium batteries increases, the cost of lithium increases for all its uses.
The required built-in computer makes lithium-ion batteries even more costly.
Because elemental lithium is unstable, it took scientists years to develop safe compounds. Lithium-ion batteries use highly toxic cobalt in the anode.
When elemental lithium escapes, it forms whiskers of metal called dendrites, to grow inside the batteries. Dendrites reduce performance and shorten the battery’s lifespan. They can grow so fast and so rigid that they pierce the membrane between the electrodes. That causes a short circuit that can lead to spontaneous combustion.
The common lithium carbon oxide batteries can also catch fire if they’re overcharged or get too hot otherwise. It only happens two or three times per million battery packs, but when it does, it causes catastrophic damage.
Some alternatives to standard lithium carbon oxide batteries
I can’t simply say alternatives to lithium-ion here. Numerous companies offer lithium iron phosphate batteries. They don’t overheat or explode. Germany’s leading battery producer, Sonnen, has marketed a lithium iron phosphate battery called ecoin the US since 2017. It costs $9,500 for 4 kWh of storage capacity and comes with a warranty that it will sustain at least 70% of that capacity for ten years.
By comparison, Tesla’s lithium carbon oxide Powerwall can store of 13.5 kilowatt-hours (kWh). It lists for $6,700, with a similar warranty.
Scientists have begun to explore lithium-air batteries and lithium-sulfur batteries, which theoretically have much higher energy density than lithium carbon oxide batteries. So far, they don’t work well, but the now standard lithium-ion batteries didn’t work well at first, either.
Some alternatives that don’t use lithium at all
Solar batteries actually don’t require lithium at all. Aluminum and phosphorous show great promise as alternative metals. They can come in all the different varieties as the lithium batteries already described.
Nickel-zinc batteries offer a cost effective, safe, and environmentally friendly alternative to lithium. Their low cycle life has been the chief barrier to commercialization. Zinc dissolution and formation of dendrites inhibit their performance. A new hybrid cathode of zinc oxide and graphene using nanotechnology seems to solve these problems.
Saltwater conducts ions, so it can be used in rechargeable batteries. With only a third of the chemical stability of lithium-ion batteries, it can’t replace lithium for batteries in electric vehicles. But it remains suitable for stationary home or grid storage of electricity.
Before filing for bankruptcy in 2017, Aquion offered a saltwater battery called Aspen. This environmentally benign battery earned Cradle to Cradle certification. A Chinese company acquired Aquion and moved all production and marketing to China. So far, they haven’t said if they plan to return to the residential market.
Formerly, its customers could buy a single battery with 2.2 kWh of capacity for $1,000. If they needed more storage, they could simply buy more than one battery. Seven Aspen batteries would provide 15.4 kWh of storage for not much more than the price of one Powerwall.
BlueSky Energy markets saltwater batteries for residential storage.
A new system suitable for grid-level storage from Stanford University with manganese sulfate stores electrons as hydrogen gas. The researchers have started the process of obtaining patents in anticipation of scaling it up for commercial application.
Under exploration, but not out of the lab yet
Sodium sulfur batteries have molten electrodes and a solid-state alumina ceramic electrolyte. They share many desirable characteristics with lithium-ion batteries, but they only operate at temperatures of at least 300ºC. Safety concerns present an obstacle to widespread use.
Room temperature sodium sulfur batteries have less capacity. Ongoing experiments with new electrolyte materials and nanotechnology in electrode design seek to make room temperature sodium sulfur batteries work at low cost, high efficiency, and greater safety.
Proton exchange membrane fuel cells require no lithium. They use platinum as a catalyst. Otherwise, they only need cheap and abundant materials to generate electricity from hydrogen. Potentially, they can power commercial and passenger ships as well as store electricity. But commercial availability is at least five years away.
10 disruptive battery technologies trying to compete with lithium-ion batteries / Sofiane Boukhalfa and Navneeta Kaul, Solar Power World. January 29, 2019
How do solar batteries compare? Tesla Powerwall vs. Sonnen eco vs. LG Chem RESU vs. Pika Energy Smart Harbor / EnergySage
How lithium-ion batteries work / Marshall Brain, How Stuff Works. November 14, 2006
Portland General Electric system. Some rights reserved by Portland General Electric
Lithium battery schematic. Public domain from Wikimedia Commons
Air Force microgrid. Public domain. Air Force photo by Donna Lindner
Lithium battery fire. Daniel Steger for openphoto.net
Saltwater storage battery. BlueSky