Chemo-mechanical expansion of lithium electrode materials – on the route to mechanically optimized all-solid-state batteries

Koerver, Raimund; Zhang, Wenbo; Biasi, Lea de; Schweidler, Simon; Kondrakov, Aleksandr; Kolling, Stefan; Brezesinski, Torsten; Hartmann, Pascal; Zeier, Wolfgang G.; Janek, Jürgen

doi:10.1039/c8ee00907d

Cited by 629 publications

(621 citation statements)

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“…The appearance of distinct cracks, even after the first discharge, in NCA80 for all‐solid‐state cells (Figure 3d) is not common for Ni‐rich cathode materials in LIBs using LEs . Although the uniaxially applied pressure is released after the cold‐pressing process, any stresses may remain locally due to elastic and plastic deformation of the SEs . Importantly, the cells are operated under external uniaxial pressure.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the wisdom, that is, the increased capacity at the expense of degraded cycling and thermal stabilities upon increasing Ni content in NCM, might hold for ASLBs as well. Furthermore, in a previous work by Janek and co‐workers, the importance of chemo‐mechanics for all‐solid‐state batteries was suggested . Only a few percent of volumetric strain in LiMO 2 during charge–discharge could lead to detachment from SEs .…”

Section: Introductionmentioning

confidence: 98%

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Ni‐Rich Layered Cathode Materials with Electrochemo‐Mechanically Compliant Microstructures for All‐Solid‐State Li Batteries

Jung

Kim

et al. 2019

Advanced Energy Materials

176

104

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While Ni‐rich cathode materials combined with highly conductive and mechanically sinterable sulfide solid electrolytes are imperative for practical all‐solid‐state Li batteries (ASLBs), they suffer from poor performance. Moreover, the prevailing wisdom regarding the use of Li[Ni,Co,Mn]O2 in conventional liquid electrolyte cells, that is, increased capacity upon increased Ni content, at the expense of degraded cycling stability, has not been applied in ASLBs. In this work, the effect of overlooked but dominant electrochemo‐mechanical on the performance of Ni‐rich cathodes in ASLBs are elucidated by complementary analysis. While conventional Li[Ni0.80Co0.16Al0.04]O2 (NCA80) with randomly oriented grains is prone to severe particle disintegration even at the initial cycle, the radially oriented rod‐shaped grains in full‐concentration gradient Li[Ni0.75Co0.10Mn0.15]O2 (FCG75) accommodate volume changes, maintaining mechanical integrity. This accounts for their different performance in terms of reversible capacity (156 vs 196 mA h g−1), initial Coulombic efficiency (71.2 vs 84.9%), and capacity retention (46.9 vs 79.1% after 200 cycles) at 30 °C. The superior interfacial stability for FCG75/Li6PS5Cl to for NCA80/Li6PS5Cl is also probed. Finally, the reversible operation of FCG75/Li ASLBs is demonstrated. The excellent performance of FCG75 ranks at the highest level in the ASLB field.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Ni‐Rich Layered Cathode Materials with Electrochemo‐Mechanically Compliant Microstructures for All‐Solid‐State Li Batteries

Jung

Kim

et al. 2019

Advanced Energy Materials

176

104

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“…[28,33,34] For this reason, sulfidebased SSBs will require coated cathode materials in order to avoid reactions between the SE and the CAM, thereby preventing the oxidation of the SE. Additionally, state-of-the-art CAMs undergo significant volume changes during lithium (de) intercalation (Figure 2c), [35,36] which often leads to detrimental contact loss within the composite cathode ( Figure 2d). [27] It will therefore be of interest to explore whether coatings can mechanically confine CAMs in order to reduce such volume changes, which may mitigate crack formation as well, or perhaps enhance adhesion within the cathode composite in order to prevent contact losses.…”

Section: Cam Coatings For Ssbs: General Considerationsmentioning

confidence: 99%

“…[35] Whether a coating survives these strains without cracking depends on the mechanical properties of the coating material and its adhesion to the CAM. A simple estimate shows that typical volume changes of a few percent cause less than 1% of lateral strain along the coating.…”

Section: Figure 2 A)mentioning

confidence: 99%

On the Functionality of Coatings for Cathode Active Materials in Thiophosphate‐Based All‐Solid‐State Batteries

Culver

Koerver

Zeier

et al. 2019

Advanced Energy Materials

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266

309

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achievable by SSBs. Meanwhile, polymer-, oxide-, and sulfide-based ionic conductors are being heavily investigated as the solid electrolyte (SE) separator. [9][10][11][12][13][14][15] Nevertheless, recent estimates [16,17] show that only batteries possessing sulfide-based SEs will be leading contenders for room-temperature applications.The sulfides, which are better denoted as thiophosphates, provide the highest lithium-ion conductivity, a relatively low E modulus, and can be processed at low temperatures. [2,3,18] Currently, only thiophosphates allow for the preparation of thick cathode composites with sufficient rate capability. [19,20] Unfortunately, thiophosphates also have a rather narrow electrochemical stability window, i.e., the onset of oxidative decomposition begins even before 3 V versus Li + /Li due to S(0)/S(−2) redox reactions, while reductive decomposition is theoretically expected at potentials of about 1.7 V versus Li + /Li due to P(+5)/P(−3) redox reactions. [21,22] Importantly, the perfect SE does not actually exist. The perfect SE would combine the ionic transport properties of thiophosphates, the mechanical properties of polymers, and the oxidation stability of oxides. Therefore, in order to exploit the superionic transport properties of thiophosphates, the implementation of protective coatings to overcome the intrinsic electrochemical instabilities is most certainly a necessity. The thermodynamic prerequisites for coatings (Figure 1) have already been treated in a number of theoretical papers, [18,21,[23][24][25] which provide the initial design guidelines.Beyond the thermodynamic considerations, it is well known that within SSBs, thiophosphate SEs are oxidized and decomposed in direct contact with cathode active materials (CAMs), in particular at high potentials during charging. [2,[26][27][28] Several years ago, Takada summarized the early work on SSBs and described the need for coatings against the formation of space charge layers at the interface between high-voltage cathodes and thiophosphate SEs. [29] Haruyama et al. concluded from density functional theory calculations that space charge layers between LiCoO 2 (LCO) and thiophosphate-based SEs are responsible for high impedances and that the addition of a buffer layer reduces such effects. [30] However, experimental evidence for such claims has not yet been reported. While these considerations are certainly valuable, from a current perspective, effects arising from the space charge layer are likely overstated and the role of oxidative degradation of the SE is understated. [31] Though the The last decade has seen considerable advancements in the development of solid electrolytes for solid-state battery applications, with particular attention being paid to sulfide superionic conductors. Importantly, the intrinsic electrochemical instability of these high-performance separators highlights the notion that further progress in the field of solid-state batteries is contingent on the optimization of component material interfaces in order to se...

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“…Here, we focus on aspects of material fatigue (rather than aging) of Ni-rich NCMs and Li-rich HE-NCMs and how fatigue, in general, affects the cell degradation. [92] In general, Ni-rich NCM CAMs suffer from larger volumetric changes with delithiation than low-Ni compounds. The material fatigue of layered transition metal oxides is commonly the result of correlated changes in electronic and structural properties.…”

Section: Introductionmentioning

confidence: 99%

Chemical, Structural, and Electronic Aspects of Formation and Degradation Behavior on Different Length Scales of Ni‐Rich NCM and Li‐Rich HE‐NCM Cathode Materials in Li‐Ion Batteries

et al. 2019

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costs are required. Current state-of-theart LIBs using, e.g., well-established LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM111) cathode material are yet not able to fulfill all these demands. In order to increase the energy density of LIBs, battery produ cers and researchers pursue various strategies. Substitution of expensive Co by Ni to achieve LiNi 1−x−y Co x Mn y O 2 compounds with x < 0.3 in order to increase the structural stability at high state-of-charge (SOC) is one possible approach. Another promising material class is represented by Li-rich high-energy NCM (HE-NCM) materials (cLi 2 MnO 3 ⋅[1 − c]LiTMO 2 [TM = Ni, Co, Mn, etc.]). All of these subgroups of layered oxides have in common a crystal structure that is prone to irreversible changes and fatigue during continuous Li (de-)intercalation. The relevant changes in electronic and crystal structure strongly depend on the particular cathode composition and micro/nanostructure. The development of a target-oriented roadmap to improved LIBs that meet the above requirements must address the underlying mechanisms on different cell levels, i.e., from the atomic level to the electrode level. A comprehensive summary of the properties and developments in the field of Ni-rich NCM [1][2][3][4][5][6][7][8][9] and Li-rich HE-NCM [10][11][12][13][14][15][16] has been presented recently In order to satisfy the energy demands of the electromobility market, both Ni-rich and Li-rich layered oxides of NCM type are receiving much attention as high-energy-density cathode materials for application in Li-ion batteries. However, due to different stability issues, their longevity is limited. During formation and continuous cycling, especially the electronic and crystal structure suffers from various changes, eventually leading to fatigue and mechanical degradation. In recent years, comprehensive battery research has been conducted at Karlsruhe Institute of Technology, mainly aiming at better understanding the primary degradation processes occurring in these layered transition metal oxides. The characteristic process of formation and mechanisms of fatigue are fundamentally characterized and the effect of chemical composition on cell chemistry, electrochemistry, and cycling stability is addressed on different length scales by use of state-of-the-art analytical techniques, ranging from "standard" characterization tools to combinations of advanced in situ and operando methods. Here, the results are presented and discussed within a broader scientific context. by several authors. Here, we focus on the detailed characterization of these materials on different length scales, including the processes during formation and fatigue.After a brief introduction of the different materials addressed here, their characteristic process of formation and mechanisms of fatigue are discussed with respect to cell chemistry, electrochemistry, and cycling stability. Based on the fundamental results of our experimental studies on the material level, the effect of formation and fatigue on different cell levels is evalu...

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Chemo-mechanical expansion of lithium electrode materials – on the route to mechanically optimized all-solid-state batteries

Abstract: The volume effects of electrode materials can cause local stress development, contact loss and particle cracking in the rigid environment of a solid-state battery.

Cited by 629 publications

References 109 publications

Ni‐Rich Layered Cathode Materials with Electrochemo‐Mechanically Compliant Microstructures for All‐Solid‐State Li Batteries

Ni‐Rich Layered Cathode Materials with Electrochemo‐Mechanically Compliant Microstructures for All‐Solid‐State Li Batteries

On the Functionality of Coatings for Cathode Active Materials in Thiophosphate‐Based All‐Solid‐State Batteries

Chemical, Structural, and Electronic Aspects of Formation and Degradation Behavior on Different Length Scales of Ni‐Rich NCM and Li‐Rich HE‐NCM Cathode Materials in Li‐Ion Batteries

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