Nickel rich layered oxide (LiNi0.8+M0.2-O2) based cathodes offer the highest energy density in state-of-the-art Li-ion batteries. From ethnical and price related perspectives, Li-ion batteries should be cobalt free, and the Ni content in today's high energy Li-ion batteries is steadily increasing. Unfortunately, suffers the thermal and cycling stability enormous with increased nickel contents. These materials suffer from reactive surfaces and a pronounces change in volume upon cycling. This results in particle cracking generating new surface, as well as the reconstructions of the crystal lattice in close vicinity to the surface causing a barrier for the motion of Li-ions. As a result, these materials tend to lose capacity over cycling quicker than tradition cathode materials. NTNU together with SINTEF has synthesised ultra-high Ni cathodes with optimised composition and morphology. These materials can be cycled over 400 times before the capacity loss was in excess of 20%. Furthermore, SINTEF and NTNU have developed methods for wet chemical surface modifications with coupling agents to further increase the cyclability. Phosphate based coating have shown to increase the thermal stability, however they come with the cost of increased internal resistance.
Virkninger
Prosjektets deltagere:
Gjennom prosjektet har vi fått økt kompetanse i syntese, overflatemodifikasjon og karakterisering av høy Nikkelkatoder. Vi fikk en generell økt forståelse av muligheter og bergensininger i dette materialsystem. Tett kontakt mellom SINTEF og NTNU har styrket kompetansen og samarbeid mellom begge institusjonene som er en grunnlaget for å skape framtidige prosjekter sammen.
Målgruppe, brukere:
Resultantene er nok først og fremst relevant for forskningsmiljøet, men også for den raskt voksende norske batteriindustrien.
Effekter
Arbeid på lovende syntesemetoder og overflatemodifikasjoner for å øke levetid av høyenergikatoder er og vil bli publisert. Dette kan på lengre sikt resultere i økt rekkevidde og levetid av batterier i for eksempel elbiler. Økt kompetanse gir NTNU og SINTEF muligheten til å være etterspurte samarbeidspartnere hos norsk industri og bidrar til å realisere det grønne skiftet.
The last decade has been the start of the revolution in electric mobility with the transition from fossil fuels to batteries as energy for transportation due to the introduction of Li-ion batteries with significantly higher energy density compared to other battery chemistries. There is a significant need to increase the gravimetric and volumetric energy density of Li ion batteries from today's state-of-the-art levels without increasing the costs for the end user. To increase the energy density in Li ion batteries, by increasing the capacity and voltage, there are several ideas and possible chemistries to select from. Post Li-ion technologies such as Li-sulphur and Li-air are some possibilities, but will require a significantly longer development time than the methodologies proposed here. HiCath will focus on development and modification of oxide intercalation cathode materials for Li-ion batteries, including optimisation of electrode structures and tailoring electrolyte compositions suitable for high voltage operations.
The main objective of HiCath is to develop a high energy cathode for Li ion batteries (high voltage and high capacity) based on oxide materials and modifications of these. We aim to develop Ni-rich NMC materials with a protective surface coating with a sacrificial Li source to counteract the first cycle inefficiency.
Currently, the applied binder for all cathodes is polyvinylidene fluoride (PVDF) which requires the polar aprotic solvent N-Methyl-2-pyrrolidone (NMP). This solvent is harmful and makes the electrode preparation complicated and expensive as NMP evaporates upon drying and has to be captured and reprocessed. Therefore, novel water based binders will be used to improve the environmental footprint of the battery, reducing the need for the NMP solvent. There will be no new development of binders, but knowledge from ongoing projects will be used to evaluate the effect of binders on the novel cathode structures developed.