Reviewing the Safe Shipping of Lithium-Ion and Sodium-Ion Cells: A Materials Chemistry Perspective

Abstract

High energy density lithium-ion (Li-ion) batteries are commonly used nowadays. Three decades’ worth of intense research has led to a good understanding on several aspects of such batteries. But, the issue of their safe storage and transportation is still not widely understood from a materials chemistry perspective. Current international regulations require Li-ion cells to be shipped at 30% SOC (State of Charge) or lower. In this article, the reasons behind this requirement for shipping Li-ion batteries are firstly reviewed and then compared with those of the analogous and recently commercialized sodium-ion (Na-ion) batteries. For such alkali-ion batteries, the safest state from their active materials viewpoint is at 0 V or zero energy, and this should be their ideal state for storage/shipping. However, a “fully discharged” Li-ion cell used most commonly, composed of graphite-based anode on copper current collector, is not actually at 0 V at its rated 0% SOC, contrary to what one might expect—the detailed mechanism behind the reason for this, namely, copper dissolution, and how it negatively affects cycling performance and cell safety, will be summarized herein. It will be shown that Na-ion cells, capable of using a lighter and cheaper aluminum current collector on the anode, can actually be safely discharged to 0 V (true 0% SOC) and beyond, even to reverse polarity (negative voltages). It is anticipated that this article spurs further research on the 0 V capability of Na-ion systems, with some suggestions for future studies provided.

Optimization Strategies Toward Functional Sodium‐Ion Batteries

“…[134,135] Overcharging/discharging will also cause oxidative/reductive electrolyte decomposition with gas production, breaking the CEI/ SEIs, and progressively consuming sodium ions in electrolyte, leading to failure of the device. [89,126,[136][137][138][139][140][141] Electrode materials, for example, PBAs with high content of coordinated water, will cause side reactions with electrolyte and gas evolution. [142] Sodiumcompensating (presodiation) cathode additives, such as NaN 3 , Na 2 CO 3 , and NaNO 2 , can increase the initial coulombic efficiency and cathode capacity, however, might cause gas production upon charging.…”

Lipoic Acid-Assisted In Situ Integration of Ultrathin Solid-State Electrolytes

“…Lithium-ion batteries (LIBs) exhibit great potential in long-range electric vehicles because of their high energy density. , Solid-state electrolytes (SSEs) with high safety have been extensively employed for LIBs. , Recently, various research studies have been concentrated on improving ionic conductivity and interfacial stability. − However, as a critical parameter affecting the energy density, the thickness of the SSEs has received less attention. − In fact, ultrathin SSEs usually possess the advantages of lower impedance, shorter ion migration path, and more efficient ion-transport capability. − Unfortunately, reducing the thickness of SSEs will inevitably sacrifice the mechanical properties (especially strength), consequently increasing the risk of lithium dendrites penetration during battery cycling, and poses serious safety hazards, which urgently requires more research into designing thinner and robust SSEs. − Besides, purely reducing the thickness of SSEs also increases the difficulty of the preparation technique, indirectly leading to enhancement of the manufacturing cost.…”

An ionic liquid synthesis route for mixed-phase sodium titanate (Na2Ti3O7 and Na2Ti6O13) rods as an anode for sodium-ion batteries

“…1,2 Sodium-ion batteries (SIBs) are regarded as a potential alternative to LIBs for a range of large-scale energy storage applications, due to a higher abundance of constituent materials, 3 price 4 and safety. 5 Some of the key challenges which currently restrict implementation of Na-ion technologies stem from the larger radius of sodium ions (1.02 Å) vs. Li (0.76 Å), alongside the need for reliable synthesis methods which produce nanostructured materials through energy-efficient means. In order to optimise electrochemical performance and make Na-ion a genuine competitor for Li-ion, the choice of electrode material and structural optimisation are key areas for focus.…”