Researchers at the University of Cambridge have identified an entirely new class of materials that could allow lithium-ion batteries to charge faster and deliver higher power performance—and at lower costs—than the nanoparticles used in battery electrodes.
This new class of materials—known as niobium tungsten oxides—could allow not only our smartphones to charge in minutes but could also make higher-power batteries that charge faster and more safely than those used in today’s EV and energy storage systems – thus potentially overcoming the battery barrier to mass adoption of EVs and solar power.
The materials that researchers have identified have excellent lithium transport rates that could help scientists and battery designers to create a super-fast charging battery, the researchers said in a paper published in the journal Nature.
Niobium tungsten oxides are also safer than graphite used for the negative electrodes in lithium-ion batteries, the researchers say. Charged at high rates, graphite tends to form metal fibers that can create a short circuit and cause the batteries to catch fire and even explode.
In addition, the niobium tungsten oxides could keep costs lower than those associated with the nanoparticles that researchers have been trying to put into batteries in their effort to make everything smaller so that the lithium ions have to travel a shorter distance, according to the paper’s authors.
Batteries have three key components in their simplest form—a positive electrode, a negative electrode, and an electrolyte. When we charge a battery, lithium ions move from the positive electrode through the crystal structure and electrolyte to the negative electrode, where they are stored. The faster the lithium ions move, the faster a battery can charge, and the more energy it can deliver for a certain amount of time.
So far, research has focused on making particles in the electrode materials smaller, but the nanoparticles have their own limitations—they are tricky to make, they tend to be ‘fluffy’, and they create unwanted chemical reactions with the electrolyte, according to Professor Clare Grey from Cambridge’s Department of Chemistry and the paper’s senior author.
“Nanoparticles can be tricky to make, which is why we’re searching for materials that inherently have the properties we’re looking for even when they are used as comparatively large micron-sized particles. This means that you don’t have to go through a complicated process to make them, which keeps costs low,” Grey said.
The niobium tungsten oxides, on the other hand, have a rigid, open structure that does not trap the inserted lithium. These materials are also bigger than many other electrode materials. The oxides are held open by ‘pillars’ of oxygen, which enable lithium ions to move through them in three dimensions.
“The oxygen pillars, or shear planes, make these materials more rigid than other battery compounds, so that, plus their open structures means that more lithium ions can move through them, and far more quickly,” says Dr Kent Griffith, a postdoctoral researcher in Cambridge’s Department of Chemistry and the paper’s first author.
The niobium tungsten oxides are also safer than graphite and “would definitely be worth looking at for fast–charging applications where you need a safer alternative to graphite,” Grey said.
Unlike nanoparticles, which are tricky and expensive to make, the niobium tungsten oxides are simple to make, the researchers say.
“A lot of the nanoparticle structures take multiple steps to synthesise, and you only end up with a tiny amount of material, so scalability is a real issue,” said Griffith. “But these oxides are so easy to make, and don’t require additional chemicals or solvents.”
“Unconventional materials and mechanisms that enable lithiation of micrometre-sized particles in minutes have implications for high-power applications, fast-charging devices, all-solid-state energy storage systems, electrode design and material discovery,” the researchers say in their paper.
Plenty of breakthroughs are being made in the vital field of energy storage, and this new class of material could well play a part in removing one of the key bottlenecks in the global transition towards cleaner energy.