Principles and trends in extreme fast charging lithium-ion batteries

Abstract

The booming electric vehicle (EV) industry is laying the cornerstone for decarbonized road transport, a sector responsible for one-sixth of global energy-related emissions. A critical barrier to the wider adoption of EVs is their ability to fast charge on a timescale comparable to refueling gasoline cars. In 2017, the US Department of Energy defined extreme fast charging (XFC), aiming to charge 80% battery capacity within 10 minutes or at 400 kW. The aim of this review is to discuss current trends and provide principles for fast charging battery research and development. We begin by comparing the charge time and power of the fastest-charging electric vehicle models on the recent markets to identify the technological gap. We then benchmark XFC battery performance in the literature based on three key parameters: charge rate, energy density, and cycle life under fast charging conditions, in an effort to standardize XFC battery data reporting. The crucial effects of electrode mass loading and cell format are highlighted. Next, a thorough analysis is conducted regarding limiting electrodes (cathode vs. anode) and their respective rate-limiting steps (mass transport vs. charge transfer) during XFC, which remains a long-standing controversy in the field and requires timely clarification. On this basis, a comprehensive perspective is presented on the most promising current strategies and future lines of research for enabling XFC-capable LIBs, focusing on electrode/electrolyte materials and battery state monitoring techniques. We anticipate that this review sharpens the focus of XFC research and serves as a guide for developing fast-charging energy storage systems including LIBs and beyond.