High‐Energy Nickel‐Cobalt‐Aluminium Oxide (NCA) Cells on Idle: Anode‐ versus Cathode‐Driven Side Reactions

Abstract

We report on the first year of calendar ageing of commercial high‐energy 21700 lithium‐ion cells, varying over eight state of charge (SoC) and three temperature values. Lithium‐nickel‐cobalt‐aluminium oxide (NCA) and graphite with silicon suboxide (Gr‐SiOx) form cathodes and anodes of those cells, respectively. Degradation is fastest for cells at 70–80 % SoC according to monthly electrochemical check‐up tests. Cells kept at 100 % SoC do not show the fastest capacity fade but develop internal short circuits for temperatures T≥40 °C. Degradation is slowest for cells stored close to 0 % SoC at all temperatures. Rates of capacity fade and their temperature dependencies are distinctly different for SoC values below and above 60 %, respectively. Differential voltage analyses, apparent activation energy analysis, and endpoint slippage tracking provide useful insights into the degradation mechanisms and the respective roles of anode and cathode potential. We discuss how reversible losses of lithium might play a role in alleviating the rate of irreversible losses on commercial cells.

Emerging Organic Surface Chemistry for Si Anodes in Lithium‐Ion Batteries: Advances, Prospects, and Beyond

“…[ 15 ] Though nanostructured Si anodes can improve the cycle life of Si anodes, the associated synthesis and processing complexities, and relatively high material cost call for more efforts to meet the demands of large‐scale applications. [ 6b,16 ] Any battery material evaluation must also consider possible low tap density and high specific surface area (SSA) of nanosized electrodes made from nanoparticles, all of which are known to result in low volumetric energy density and severe initial Coulombic efficiency (ICE) loss. Moreover, progressive degradation of the electrical contact is a known notorious aspect that impedes the application of nano‐Si.…”

“…[1] Energy storage techniques, therefore, have become a pressing need in particular with grid-scale and mobile energy application scenarios (e.g., electric already commercialized the utilization of small amounts of Si as an additive in graphite anode, reaching a cell energy level of 300 Wh kg −1 to enable longer travel ranges of EVs. [6] Nonetheless, to further improve cell metrics toward higher energy density, a Si-based anode with increasing Si contents deems necessary. This imposes severe challenges in juggling many aspects of anode attributes such as cycle-life, capacity, tap density, and cost.…”

High‐Throughput Experimentation and Computational Freeway Lanes for Accelerated Battery Electrolyte and Interface Development Research

“…Some studies do however require very long experimental times and exhibit very smooth trends such as calendric ageing studies changing the perspective of the efficacy of acceleration of experiments through automatization versus acceleration of research through automatic analysis. [ 175 ]…”

Entropy profiling for the diagnosis of NCA/Gr-SiOx Li-ion battery health

“…This suggests that the entropy change curve is more sensitive to anode phase transformations than the DVA curve. [ 17,18]. Loss of active material (LAM) in the positive electrode Q LAM,PE is calculated from the capacity difference between D 4 and Q full , the maximum measured capacity.…”

“…These are well-established methods for degradation mechanism identification [14,15]. However, so far the application of these methods to degradation has been based only on LAM/LLI, without further microstructural interpretation [16,17,18]. Additionally, all these methods are performed at constant temperature, however, temperature dependence also contains information relevant to degradation.…”