Compliant Yet Brittle Mechanical Behavior of Li2S–P2S5 Lithium‐Ion‐Conducting Solid Electrolyte

McGrogan, Frank Patrick; Swamy, Tushar; Bishop, Sean R.; Eggleton, Erica; Porz, Lukas; Chen, Xinwei; Chiang, Yet‐Ming; Vliet, Krystyn J. Van

doi:10.1002/aenm.201602011

Cited by 252 publications

(141 citation statements)

References 36 publications

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“…Galvanostatic current densities were thus chosen to lie in the neighborhood of the critical current density, determined by a step-wise current density ramp experiment until a short-circuit event is observed. [45] X-ray diffraction (XRD) was also used to confirm that the sample is amorphous. Scanning electron microscopy (SEM) and atomic force microcopy (AFM) were used for surface analysis.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes

Porz

Swamy

Sheldon

et al. 2017

Advanced Energy Materials

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917

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vast improvements in energy density may be achieved with lithium metal anodes owing to their high gravimetric capacity (3869 mA h g −1 ) and low density (0.534 g cm −3 ). However, adoption of rechargeable lithium metal batteries has been unsuccessful thus far due to safety concerns associated with short circuits that occur when Li dendrites grow through the liquid electrolyte during the charging process. [4][5][6] Although several approaches have reduced dendrite formation, [7][8][9][10] to date the phenomenon has not been avoided under all relevant conditions. Nonflammable inorganic solid electrolytes, paired with Li metal anodes, could result in high energy density yet safe rechargeable lithium batteries. [11][12][13][14][15] As reviewed by Takada, [12] inorganic solid electrolytes have now been widely studied, [16][17][18][19][20] but are not yet commercialized. Monroe and Newman have suggested that dendrite growth during the plating process may be suppressed if the liquid electrolyte is replaced with a Li-ion conducting solid electrolyte of a sufficiently high shear modulus. [21,22] According to this criterion, numerous inorganic solid electrolytes should be able to suppress dendrite formation. However, multiple research groups have recently reported cases where ceramic solid electrolytes paired with a Li metal anode experience a short circuit Li deposition is observed and measured on a solid electrolyte in the vicinity of a metallic current collector. Four types of ion-conducting, inorganic solid electrolytes are tested: Amorphous 70/30 mol% Li 2 S-P 2 S 5 , polycrystalline β-Li 3 PS 4 , and polycrystalline and single-crystalline Li 6 La 3 ZrTaO 12 garnet. The nature of lithium plating depends on the proximity of the current collector to defects such as surface cracks and on the current density. Lithium plating penetrates/infiltrates at defects, but only above a critical current density. Eventually, infiltration results in a short circuit between the current collector and the Li-source (anode). These results do not depend on the electrolytes shear modulus and are thus not consistent with the Monroe-Newman model for "dendrites." The observations suggest that Li-plating in pre-existing flaws produces crack-tip stresses which drive crack propagation, and an electrochemomechanical model of plating-induced Li infiltration is proposed. Lithium short-circuits through solid electrolytes occurs through a fundamentally different process than through liquid electrolytes. The onset of Li infiltration depends on solid-state electrolyte surface morphology, in particular the defect size and density.

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Section: Resultsmentioning

confidence: 99%

Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes

Porz

Swamy

Sheldon

et al. 2017

Advanced Energy Materials

Self Cite

917

973

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“…As such, full coverage of the CAM particles with a coating material that is electronically insulating would therefore inhibit the electrode from functioning. On the other hand, where the coating material is of a rather soft nature (e.g., polymer based) and more comparable to the thiophosphate-based SEs (E ≈ 20 GPa [49,50] ), the coating may be deformed and thinned out until minimal fracturing of the coating allows for contact between the particles. Assuming homogeneous coverage of the CAM particles with a protective coating, contact must then be achieved during electrode processing.…”

Section: Deformation Of Cam Coatingsmentioning

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

269

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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“…Their deformation properties, wholly different from their oxide counterparts, 24,25 facilitate the consolidation of sulfide SSEs into dense bodies of various geometric form factors and the resulting increase in bulk density can increase conductivity. [88][89][90] Doped LPS of congruently melting compositions, such as the argyrodite (Li 6 PS 5 X where X = Cl, Br, I) family, can exhibit superior conductivity and electrochemical stability in comparison to pure LPS counterparts.…”

mentioning

confidence: 99%

Review—Practical Challenges Hindering the Development of Solid State Li Ion Batteries

Kerman

Luntz

Viswanathan

et al. 2017

J. Electrochem. Soc.

603

471

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Solid state electrolyte systems boasting Li + conductivity of >10 mS cm −1 at room temperature have opened the potential for developing a solid state battery with power and energy densities that are competitive with conventional liquid electrolyte systems. The primary focus of this review is twofold. First, differences in Li penetration resistance in solid state systems are discussed, and kinetic limitations of the solid state interface are highlighted. Second, technological challenges associated with processing such systems in relevant form factors are elucidated, and architectures needed for cell level devices in the context of product development are reviewed. Specific research vectors that provide high value to advancing solid state batteries are outlined and discussed. Solid state battery systems are of great interest because of potential benefits in gravimetric and volumetric energy density, operable temperature range, and safety in comparison to traditional liquid electrolyte based systems. However, unresolved fundamental issues remain in the quest to fully understand the behavior of all-solid batteries, especially in the area of electrochemical interfaces.1 There are also a number of significant engineering challenges that require methodical effort to enable a tangible product. Some transitions from academic laboratories to entrepreneurial efforts attempting to overcome these challenges remain unsuccessful in efforts to bring a product to the market.2,3 Vital parameters that require robust understanding from a product development standpoint are material cost, cell lifetime and shelf life, cell energy density on a volumetric and gravimetric basis, operable capabilities for given temperature conditions, and safety. The advantage of energy density remains to be realized in solid state electrolytes (SSEs) since most studies to date utilize thick SSEs or cathodes with low active loading compared to liquid counterparts. 4,5 Furthermore, the desire to use SSEs in conjunction with Li metal anodes requires understanding and managing the morphology of Li metal plating, which can impact volumetric energy density. Operation at both higher and lower temperature compared to conventional technologies is a significant potential advantage of SSE systems. However, reports of solid state cells achieving parity with traditional systems at room temperature or any other temperature do not currently exist. The safety, specifically decreased flammability, of SSE systems is another potential advantage but requires ongoing validation and study.6 Unlike current liquid electrolyte systems, 7 the manufacturability and material component costs of SSEs have not been well characterized, and thus the value of these features will need to be weighed accordingly with any added cost. Operating lifetime of SSEs capturing intrinsic materials parameters such as voltage stability, 8 as well as catastrophic failure modes such as shorting, 9 have been briefly investigated, but in the absence of high energy density electrode formulations and appli...

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Compliant Yet Brittle Mechanical Behavior of Li₂S–P₂S₅ Lithium‐Ion‐Conducting Solid Electrolyte

Cited by 252 publications

References 36 publications

Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes

Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes

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

Review—Practical Challenges Hindering the Development of Solid State Li Ion Batteries

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