Avoid 'lots', 'a lot', 'plenty' and 'loads'
Choose more formal equivalents when describing a large number or quantity.
Less formal:
(1a) Lots of/plenty of research has been published on the development of hybrid vehicles.
(2a) A lot of studies have been published on the development of hybrid vehicles.
More formal:
(1b) A great deal of research has been published on the development of hybrid vehicles.
(1c) Much research has been published [...]
(1d) A significant amount of research has been published...
(2b) Many studies have been published on the development of hybrid vehicles.