Overview of multi-stage charging strategies for Li-ion batteries

To reduce the carbon footprint in the transportation sector and improve overall vehicle efficiency, a large number of electric vehicles are being manufactured. This is due to the fact that environmental concerns and the depletion of fossil fuels have become significant global problems. Lithium-ion batteries (LIBs) have been distinguished themselves from alternative energy storage technologies for electric vehicles (EVs) due to superior qualities like high energy and power density, extended cycle life, and low maintenance cost to a competitive price. However, there are still certain challenges to be solved, like EV fast charging, longer lifetime, and reduced weight. For fast charging, the multi-stage constant current (MSCC) charging technique is an emerging solution to improve charging efficiency, reduce temperature rise during charging, increase charging/discharging capacities, shorten charging time, and extend the cycle life. However, there are large variations in the implementation of the number of stages, stage transition criterion, and C-rate selection for each stage. This paper provides a review of these problems by compiling information from the literature. An overview of the impact of different design parameters (number of stages, stage transition, and C-rate) that the MSCC charging techniques have had on the LIB performance and cycle life is described in detail and analyzed. The impact of design parameters on lifetime, charging efficiency, charging and discharging capacity, charging speed, and rising temperature during charging is presented, and this review provides guidelines for designing advanced fast charging strategies and determining future research gaps.