Northvolt’s Advanced Technology Group, formed by the company Cubeg, recently acquired by the Swedish manufacturer, has made a breakthrough for the next generation of batteries made up of lithium metal cells. This is indicated by the external tests performed about them that they have certified that they are capable of withstanding 672 charge and discharge cycles maintaining 80% of its energy capacity. Now, the goal is to increase the electrical load and go from 5 Ah cells to 20 Ah cellswhich can be used by its aerospace customers.
Current anodes are composed of a mixture of graphite and copper although the pure lithium metal it is shown as a promising alternative, since it offers the highest energy density among solid materials. Using it in place of graphite and copper in the electrode of today’s batteries could deliver dramatic performance gains. The integration of lithium metal is one of the most interesting options to be used as energy stores in applications of all kinds, including electric vehicles.
However, the handicap of lithium metal anodes it is in the short life cycle they offer, given their chemical instability, which causes them to end up falling apart. They are also at increased risk of dendrite formation and short circuits. Its use in conjunction with solid-state electrolytes is being widely developed as a solution to these problems, but designs using a thin protective barrier and stable liquid electrolyte as a means of enabling lithium metal anodes are also being explored.
After the round of performance tests completed, Cubegthe American start-up acquired by northvolt in March 2021, has shown that it has achieved extend the life of a lithium metal cell. Specifically, this third-party validation demonstrated that a battery cell of 5.1Ah with an energy density of 380Wh/kg reached a useful life of 672 charge and discharge cycles. The cell was charged and discharged those 672 times before its energy content dropped below 80% of original value. This degradation limit is generally accepted by the industry to mark the end of a battery cell’s first useful life. From there, it can be used in a second life application before being recycled.
By way of comparison, the high-performance lithium-ion cells available today for commercial electric vehicles reach around 250Wh/kg. Your future generations, with high nickel content cells and anode doped with silicon and with a tighter design, they will be able to provide between 250 and 300Wh/kg.
According to Northvolt’s statement, the cell was tested “under typical conditions with real-world requirements, including ambient temperature. The results demonstrate that it is the world’s highest performing and longest lasting lithium metal cell validated independently in a commercially representative cell size.
According to Richard Wang, founder and CEO of Cuberg, cell life cycles are a key performance criterion for a battery that primarily affects its possible applications. “While the energy density of lithium metal cells far exceeds that of conventional lithium-ion cells, their low cycle lives have limited their appeal.” The latest results confirm that the technology can meet all the key performance requirements demanded by mobility applications.
The 5.1 Ah cell tested is not at the level needed to be usable by your customer’s applications. According to Northvolt, Cubeg’s next move will be develop and validate a 20 Ah cell “intended as a commercial format for its aerospace clients”. To date, the group has delivered nearly 2,000 cells to its electric aviation customers.
Cuberg has expanded its production facility in San Leandro, San Francisco Bay Area, following its acquisition by Northvolt. At these facilities, it has shown that lithium metal cells can be manufactured using the same production processes that are used for today’s lithium-ion batteries.