by josh perry, editor
a direct, precise test of the internal temperatures and electrode potentials of commercially-available lithium-ion batteries, based on new research from the warwick manufacturing group (wmg) at the university of warwick (coventry, u.k.), has reveled that batteries can be charged five times faster than current limits.
researchers have developed a method for internal battery temperature testing.
(university of warwick)
according to a report from the university, the new sensor technology works during a battery’s normal operation without affecting performance and has the potential to advance battery material science, new battery designs, and the design of energy storage systems.
maximum charging rates are created by manufacturers to avoid overheating, which impacts battery performance and could even lead to thermal runaway with its dangerous consequences. the charging rates were always based on conservative limits from external testing, while this new method gives much greater insight into battery potential, especially in the automotive industry.
“the technology the wmg researchers have developed for this new direct in-situ battery sensing employs miniature reference electrodes and fibre bragg gratings (fbg) threaded through bespoke strain protection layer,” the report explained.
it added, “an outer skin of fluorinated ethylene propylene (fep) was applied over the fibre, adding chemical protection from the corrosive electrolyte. the result is a device that can have direct contact with all the key parts of the battery and withstand electrical, chemical and mechanical stress inflicted during the batteries operation while still enabling precise temperature and potential readings.”
the research was recently published in electrochimica acta. the abstract stated:
“the charging rates of commercial high-energy li-ion cells are limited by the manufacturer's specifications leading to lengthy charging times. however, these cells are typically capable of much faster charging, if one ensures that the thermal and electrode-specific voltage profiles do not exceed safety limits.
“unfortunately, precise and in-situ measurements of these parameters have not been achieved to date without altering the operation of these cells.
“here we present a method to assess the maximum current for commercial 18650s, using novel instrumentation methods enabling in operando measurements. we found the maximum charging current that could be safely applied to the evaluated high-energy cells is 6.7 times higher than the manufacturer-stated maximum.
“subsequently a rapid-charging protocol was developed that leads to over five-fold reduction in charging times without compromising the safety limits of the cells. we anticipate our work to be a starting point for a more sophisticated understanding of commercial li-ion cells through deployment of diverse in-situ sensor systems.
“this understanding will enable advances in battery materials science, thermal engineering and electrical engineering of battery technology. furthermore, this work has the potential to help the design of energy storage systems for high performance applications such as motor racing and grid balancing.”