Challenges and Strategies for Fast Charge of Li‐Ion Batteries

Abstract

Long charging time for Li‐ion batteries is a critical obstacle for the widespread adoption of electric vehicles, especially when compared with the rapid refueling of traditional internal combustion engine vehicles. Fast charging results in accelerated performance degradation and low energy efficiency for Li‐ion batteries. The batteries adopted in the present electric vehicle market are mainly based on chemistry consisting of a graphite anode and a layered lithium transition‐metal oxide cathode. The fast‐charging capability of such batteries is limited by Li plating on the graphite anode and structural instability of the layered lithium transition‐metal oxide cathode. In this Minireview, the challenges and possible solutions to these fast charge problems are reviewed at both the materials and cell levels.

Design aspects of electrolytes for fast charge of Li‐ion batteries

“…All these issues result in low coulombic efficiency and the loss in the inventory of cyclable Li + ions, which have been identified to be the root origin for the capacity degradation of Li-ion batteries under fast charge conditions. 4,6 Aiming to solve the above problems, the design for fast charge electrolytes should take the following aspects into account.…”

“…Structural degradation is the primary source for performance decay of the layered cathode materials. 4,6 Nearly all capacity fade problems of the layered cathode materials can be ultimately attributed to the loss of oxygen, and the evolution of oxygen involves many activated oxygen intermediates, such as covalent peroxide bonds (MO-OM), oxygen radicals, and excited-state singlet oxygen ( 1 O 2 ). 5 In this regard, nonflammable electrolytes 13,45,46 and oxygen scavenging additives [47][48][49] are expected to be capable of preventing the propagation of oxygen radicals and scavenging the activated oxygen intermediates, which consequently stabilizes the crystalline structure of the layered cathode materials and mitigates parasitic reactions with the electrolyte solvents.…”

“…Li plating is the culprit for the capacity fade of Li-ion batteries under fast charge. 4 An electrolyte additive that can regulate Li metal electrodeposition and stabilize the plated Li metal is highly demanded for mitigating the Li plating related problems. Even without Li plating, the Li-ion cells under fast charge are still subject to rapid capacity fade because the SEI cannot effectively prevent electrolyte solvents from reductive decomposition at the anode 6 and protect graphite from structural exfoliation 50 as a result that the SEI fails to block the solvated Li + ions from permeating to the SEI-electrode interface.…”

“…In many cases, fast charge triggers Li plating at the graphite anode and structural degradation of the layered cathode material at the cathode. [1][2][3][4] Carbonate solvents are thermodynamically unstable with the plated Li metal and the activated oxygen intermediates released from degradation of the delithiated cathode materials at high state-of-charges. 5 Parasitic reactions of the electrolyte with plated Li and released oxygen deplete not only electrolyte solvents but also cyclable Li + ions.…”

Research Progress of Lithium Plating on Graphite Anode in Lithium‐Ion Batteries

“…Some other research works also presented charge strategies to optimize Li plating, resulting in suppressed ageing rate and improved safety. [ 22,86‐88 ]…”