Scientists from the Japan Advanced Institute of Science and Technology (JAIST) have developed a novel binder material that could help lithium-ion batteries reach 1,700 cycles.
The team used a binder made from a bis-imino-acenaphthenequinone-paraphenylene (BP) copolymer to protect the graphite anode, which they claim preserve the electrode’s capacity at 95% of its original value even after >1700 charge cycles.
The research was undertaken to find a way to combat capacity fade in lithium-ion batteries using the widely used poly(vinylidene fluoride) (PVDF) binder.
Images of the binders taken with a scanning electron microscope before and after cycling revealed tiny cracks had formed on the BP copolymer, whereas large cracks had formed on PVDF.
The study was published in the journal ACS Applied Energy Materials.
The work was led by professor Noriyoshi Matsumi and professor Tatsuo Kaneko, senior lecturer Rajashekar Badam, PhD student Agman Gupta, and former postdoctoral fellow Aniruddha Nag.
Professor Matsumi said: "Whereas a half-cell using PVDF as a binder exhibited only 65% of its original capacity after about 500 charge-discharge cycles, the half-cell using the BP copolymer as a binder showed a capacity retention of 95% after over 1700 such cycles.
"The realisation of durable batteries will help in the development of more reliable products for long-term use. This will encourage consumers to purchase more expensive battery-based assets like electric vehicles, which will be used for many years."
Researchers found the BP binder offered significantly better mechanical stability and adherence to the anode, in part from the interactions between the bis-imino-acenaphthenequinone groups and graphite, and also from the good adherence of the copolymer's ligands to the copper current collector of the battery.
BP copolymer is also more conductive than PVDF as it forms a thinner conductive solid electrolyte interface.
BP copolymer also doesn’t react easily with the electrolyte, which prevents its degradation.