An Outlook on Lithium Ion Battery Technology

Abstract

Lithium ion batteries as a power source are dominating in portable electronics, penetrating the electric vehicle market, and on the verge of entering the utility market for grid-energy storage. Depending on the application, trade-offs among the various performance parameters-energy, power, cycle life, cost, safety, and environmental impact-are often needed, which are linked to severe materials chemistry challenges. The current lithium ion battery technology is based on insertion-reaction electrodes and organic liquid electrolytes. With an aim to increase the energy density or optimize the other performance parameters, new electrode materials based on both insertion reaction and dominantly conversion reaction along with solid electrolytes and lithium metal anode are being intensively pursued. This article presents an outlook on lithium ion technology by providing first the current status and then the progress and challenges with the ongoing approaches. In light of the formidable challenges with some of the approaches, the article finally points out practically viable near-term strategies.

Figure 1

Capacity and voltage ranges of anode and cathode materials for lithium-based batteries. The voltage stability window for the currently used liquid electrolytes in lithium ion batteries and the possibility to widen the stability window by the formation of optimal SEI layers on the electrodes are indicated.

Figure 2

Crystal structures of graphite Li_xC₆, layered LiMO₂ (M = Mn, Co, and Ni), spinel LiMn₂O₄, and olivine LiFePO₄.

Figure 3

(a) Positions of the various redox couples relative to the top of the oxygen:2p band and (b) schematic energy levels of an anode, cathode, and electrolyte in an open circuit. The possibility to widen the stability window by the formation of optimal SEI layers on the electrodes are indicated in panel b.

Figure 4

(a) TOF-SIMS chemical mapping of the organic electrolyte decomposition layer and dissolved transition-metal layer in the form of fluorides on an NMC cathode particle. (b) Comparison after 3,000 cycles of the amounts of transition-metal dissolution, forming metal fluorides (e.g., MnF₂), from an undoped and a 1 mol % Al-doped NMC cathode relative to that from a fresh electrode. (c) Comparison after 3,000 cycles of the amounts of dissolved transition metals and the calculated thickness of Li metal dendrites on graphite anodes that were paired with an undoped and a 1 mol % Al-doped NMC cathode. (d) Schematic illustrating the evolution of the SEI on graphite anode during cycling under the influence of dissolved transition-metal ion crossover from the cathode to the anode. Reproduced with permission from ref (37). Copyright 2017 American Chemical Society.