Changing how battery particles are ordered speeds up charging times without affecting energy storage
A lithium-ion battery that uses copper and copper nanowires to organise its particles can charge to 60 per cent in 6 minutes, without affecting its energy storage. This more efficient battery could one day power electric cars, allowing drivers to travel further without waiting as long for the vehicle to charge.
Batteries, which are largely lithium-ion, use binding agents to stick their particles together to provide a solid structure. This can create a thick battery fluid with a random distribution of particles, leading to slower charging times. The particles of thinner battery fluids are ordered to charge more quickly, but tend to store less energy.
To overcome these issues, Yao Hongbin at the University of Science and Technology of China in Hefei and his colleagues have designed a lithium-ion battery with a structured anode, the positive end of a battery.
Lithium battery anodes are typically made of graphite particles through which charge flows, with these particles generally arranged in a fairly random order. Hongbin and his team organised the particles in order of both particle size and the number of gaps between particles, known as porosity.
Their battery charged to 60 per cent and 80 per cent in 5.6 and 11.4 minutes, respectively, while maintaining a high energy storage on standard tests.
The researchers didn’t record the time to get to a 100 per cent charge. Electric car manufacturers often recommend vehicles be charged to up to 80 per cent to maintain battery longevity. A Tesla typically takes 40 minutes to an hour to get from 40 per cent to 80 per cent charge.
“In our design, we control the whole density in the electrode,” says Yao. “We use a higher porosity in the top [of the anode] but lower porosity in the bottom, so that the average porosity has a normal value.”
To organise the particles by both size and porosity, Yao and his team coated the graphite anode particles with copper and mixed in copper nanowires. The particles were then heated, cooled and compressed, setting the ordered structure.
“This natural sedimentation process is nice, however, I feel that the additional processing steps needed to coat the graphite and make the copper nanowires could add appreciable cost,” says Billy Wu at Imperial College London.
Heating and cooling the anode may also add an additional cost to what is traditionally a cheaper battery component, says Wu.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abm6624