Helmholtz-Institute Ulm

Both S., Hein S., Danner T., Latz A.

AbstractNickel‐Manganese‐Cobalt (NMC) oxides are widely used as cathode materials in lithium‐ion batteries. While increasing the nickel content increases the available capacity in a given voltage window, it also reduces the structural stability of the material when cycled to high cutoff voltages. Oxygen release from the crystal structure as well as a layered‐to‐rocksalt phase transformation of the layered oxide material cause capacity loss and impedance rise. In this work, we propose a continuum approach to model oxygen release and the associated phase transformation using a 1+1D model informed by atomistic simulations to predict the thickness of reconstructed active material over time. An efficient interface model allows us to combine this approach with 3D microstructure‐resolved simulations in order to study the effect of a resistive layer on a real cathode microstructure. This novel workflow enables us to investigate the effect of individual electrode properties on the phase transformation and guide future electrode design.

Helmbrecht K., Groß A.

Li C., Yu J., Yang D., Li H., Cheng Y., Ren Y., Bi X., Ma J., Zhao R., Zhou Y., Wang J., Huang C., Li J., Pinto-Huguet I., Arbiol J., et. al.

He Y., Ting Y., Hu H., Diemant T., Dai Y., Lin J., Schweidler S., Marques G.C., Hahn H., Ma Y., Brezesinski T., Kowalski P.M., Breitung B., Aghassi‐Hagmann J.

Zhang J., Pan L., Jia L., Dong J., You C., Han C., Tian N., Cheng X., Tang B., Guan Q., Zhang Y., Deng B., Lei L., Liu M., Lin H., et. al.

Ajuria J., Mysyk R., Carriazo D., Saurel D., Arnaiz M., Crosnier O., Brousse T., Ge K., Taberna P., Simon P., Ratso S., Karu E., Varzi A., Badillo J.P., Hainthaler A., et. al.

AbstractNow that fast action is needed to mitigate the effects of climate change, developing new technologies to reduce the worldwide carbon footprint is critical. Sodium ion capacitors can be a key enabler for widespread transport electrification or massive adoption of renewable technologies. However, a years‐long journey needs to be made from the first proof‐of‐concept report to a degree of maturity for technology transfer to the market. To shorten this path, this work gathers all the stakeholders involved in the technical development of the sodium ion capacitor technology, covering the whole value chain from academics (TRL 1–3) and research centers (TRL3–5) to companies and end‐users (TRL 6–9). A 360‐degree perspective is given on how to focus the research and technology development of sodium ion capacitors, or related electrochemical energy storage technologies, from understanding underlying operation mechanisms to setting up end‐user specifications and industrial requirements for materials and processes. This is done not only in terms of performance metrics, but mainly considering relevant practical parameters, i. e., processability, scalability, and cost, leading up to the final sustainability evaluation of the whole of the technology by Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) analysis, which is of utmost importance for society and policymakers.

Xu C., Diemant T., Zhang S., Liu X., Passerini S.

AbstractAl−Se batteries (ASeBs) with high theoretical specific capacity and discharge voltage are promising energy storage devices. However, the detrimental shuttle effect occurring in conventional ionic liquid electrolytes (ILEs) challenges their development. Herein, a thicker cathode/electrolyte interphase (CEI) is constructed via employing locally concentrated IL electrolytes (LCILEs) to overcome these issues. It is demonstrated that LCILEs facilitate the incorporation of Emim+ into the electrode/electrolyte interphases, and, meanwhile, more Al−Cl species deposits are observed in the CEI. The formed CEI effectively prevents the dissolution of poly‐selenides, inhibiting their related parasitic reactions. These result in ASeBs, employing the LCILE, to deliver a specific discharge capacity of 218 mAh g−1 at 0.5 A g−1 after 100 cycles at 20 °C, while the cell using the neat ILE only maintains 38 mAh g−1 under the same conditions. Moreover, an Al−S cell operated in LCILEs reaches 578 mAh g−1 at 0.1 A g−1 after 150 cycles, which is also significantly better than 317 mAh g−1 in the neat ILE. This study provides an LCILE‐based strategy to reinforce the CEI in order to suppress the shuttle effect, realizing Al‐chalcogen batteries with better performance.

Xu C., Diemant T., Zhang S., Liu X., Passerini S.

AbstractAl−Se batteries (ASeBs) with high theoretical specific capacity and discharge voltage are promising energy storage devices. However, the detrimental shuttle effect occurring in conventional ionic liquid electrolytes (ILEs) challenges their development. Herein, a thicker cathode/electrolyte interphase (CEI) is constructed via employing locally concentrated IL electrolytes (LCILEs) to overcome these issues. It is demonstrated that LCILEs facilitate the incorporation of Emim+ into the electrode/electrolyte interphases, and, meanwhile, more Al−Cl species deposits are observed in the CEI. The formed CEI effectively prevents the dissolution of poly‐selenides, inhibiting their related parasitic reactions. These result in ASeBs, employing the LCILE, to deliver a specific discharge capacity of 218 mAh g−1 at 0.5 A g−1 after 100 cycles at 20 °C, while the cell using the neat ILE only maintains 38 mAh g−1 under the same conditions. Moreover, an Al−S cell operated in LCILEs reaches 578 mAh g−1 at 0.1 A g−1 after 150 cycles, which is also significantly better than 317 mAh g−1 in the neat ILE. This study provides an LCILE‐based strategy to reinforce the CEI in order to suppress the shuttle effect, realizing Al‐chalcogen batteries with better performance.

Jin J., Wang Y., Zhao X., Hu Y., Li T., Liu H., Zhong Y., Jiao L., Liu Y., Chen J.

AbstractLayered manganese‐rich oxides (LMROs) are widely recognized as the leading cathode candidates for grid‐scale sodium‐ion batteries (SIBs) owing to their high specific capacities and cost benefits, but the notorious Jahn‐Teller (J‐T) distortion of Mn3+ always induces severe structural degradation and consequent rapid cathode failure, impeding the practical implementation of such materials. Herein, we unveil the “intrinsic distortion against J‐T distortion” mechanism to effectively stabilize the layered frameworks of LMRO cathodes. The intrinsic distortion simply constructed by introducing bulk oxygen vacancies is systematically confirmed by advanced synchrotron X‐ray techniques, atomic‐scale imaging characterizations, and theoretical computations, which can counteract the J‐T distortion during cycling due to their opposite deformation orientations. This greatly decreases and uniformizes the lattice strain within the ab plane and along the c axis of the material, thereby alleviating the P2‐P′2 phase transition as well as suppressing the edge dislocation and intragranular crack formation upon repeated cycles. As a result, the tailored P2‐Na0.72Mg0.1Mn0.9O2 cathode featuring intrinsic distortion delivers a considerably enhanced cycling durability (91.9 % capacity retention after 500 cycles) without sacrificing the Mn3+/Mn4+ redox capacity (186.5 mAh g−1 at 0.3 C). This intrinsic distortion engineering paves a brand‐new and prospective avenue toward achieving high‐performance LMRO cathodes for SIBs.

Jin J., Wang Y., Zhao X., Hu Y., Li T., Liu H., Zhong Y., Jiao L., Liu Y., Chen J.

AbstractLayered manganese‐rich oxides (LMROs) are widely recognized as the leading cathode candidates for grid‐scale sodium‐ion batteries (SIBs) owing to their high specific capacities and cost benefits, but the notorious Jahn‐Teller (J‐T) distortion of Mn3+ always induces severe structural degradation and consequent rapid cathode failure, impeding the practical implementation of such materials. Herein, we unveil the “intrinsic distortion against J‐T distortion” mechanism to effectively stabilize the layered frameworks of LMRO cathodes. The intrinsic distortion simply constructed by introducing bulk oxygen vacancies is systematically confirmed by advanced synchrotron X‐ray techniques, atomic‐scale imaging characterizations, and theoretical computations, which can counteract the J‐T distortion during cycling due to their opposite deformation orientations. This greatly decreases and uniformizes the lattice strain within the ab plane and along the c axis of the material, thereby alleviating the P2‐P′2 phase transition as well as suppressing the edge dislocation and intragranular crack formation upon repeated cycles. As a result, the tailored P2‐Na0.72Mg0.1Mn0.9O2 cathode featuring intrinsic distortion delivers a considerably enhanced cycling durability (91.9 % capacity retention after 500 cycles) without sacrificing the Mn3+/Mn4+ redox capacity (186.5 mAh g−1 at 0.3 C). This intrinsic distortion engineering paves a brand‐new and prospective avenue toward achieving high‐performance LMRO cathodes for SIBs.

Li M., Liu X., Wu J., Dong X., Wang Y., Passerini S.

Verma A.K., Atif S., Padhy A., Choksi T.S., Barpanda P., Govind Rajan A.

Wildersinn L., Stottmeister D., Jeschull F., Groß A., Hofmann A.

Zhao W., Zhang R., Ren F., Karger L., Dreyer S.L., Lin J., Ma Y., Cheng Y., Pal A.S., Velazquez-Rizo M., Ahmadian A., Zhang Z., Müller P., Janek J., Yang Y., et. al.

Qin Y., Yang F., Yuwono J.A., Varzi A.

AbstractSeparators are critical components of zinc‐metal batteries (ZMBs). Despite their high ionic conductivity and excellent electrolyte retention, the widely used glass fiber (GF) membranes suffer from poor mechanical stability and cannot suppress dendrite growth, leading to rapid battery failure. Contrarily, polymer‐based separators offer superior mechanical strength and facilitate more homogeneous zinc (Zn) deposition. However, they typically suffer from sluggish ion transport kinetics and poor wettability by aqueous electrolytes, resulting in unsatisfactory electrochemical performance. Here a dehydroxylation strategy is proposed to overcome the above‐mentioned limitations for polyvinyl alcohol (PVA) separators. A dehydroxylated PVA‐based membrane (DHPVA) is synthesized at a relatively low temperature in a highly concentrated alkaline solution. Part of the hydroxyl groups are removed and, as a result, the hydrogen bonding between PVA chains, which is deemed responsible for the sluggish ion transport kinetics, is minimized. At 20 °C, the ionic conductivity of DHPVA reaches 12.5 mS cm−1, which is almost 4 times higher than that of PVA. Additionally, DHPVA effectively promotes uniform Zn deposition, leading to a significantly extended cycle life and reduced polarization, both in a/symmetric (Cu/Zn and Zn/Zn) and full cells (Zn/NaV3O8). This study provides a new, effective, yet simple approach to improve the performance of ZMBs.