Owing to the ever‐increasing safety concerns about conventional lithium‐ion batteries, whose applications have expanded to include electric vehicles and grid‐scale energy storage, batteries with ...solidified electrolytes that utilize nonflammable inorganic materials are attracting considerable attention. In particular, owing to their superionic conductivities (as high as ≈10−2 S cm−1) and deformability, sulfide materials as the solid electrolytes (SEs) are considered the enabling material for high‐energy bulk‐type all‐solid‐state batteries. Herein the authors provide a brief review on recent progress in sulfide Li‐ and Na‐ion SEs for all‐solid‐state batteries. After the basic principles in designing SEs are considered, the experimental exploration of multicomponent systems and ab initio calculations that accelerate the search for stronger candidates are discussed. Next, other issues and challenges that are critical for practical applications, such as instability in air, electrochemical stability, and compatibility with active materials, are discussed. Then, an emerging progress in liquid‐phase synthesis and solution process of SEs and its relevant prospects in ensuring intimate ionic contacts and fabricating sheet‐type electrodes is highlighted. Finally, an outlook on the future research directions for all‐solid‐state batteries employing sulfide superionic conductors is provided.
Sulfide Li+ and Na+ superionic conductors are considered to be enabling materials in safe and high‐energy all‐solid‐state batteries. This progress report provides a brief review on superionic conductor solid electrolytes through both experimental and theoretical approaches on ionic conductivity, electrochemical stability, interface compatibility, and air‐stability. Further, design strategies, practical considerations, and emerging solution processes of solid electrolytes are discussed.
For mass production of all‐solid‐state lithium‐ion batteries (ASLBs) employing highly Li+ conductive and mechanically sinterable sulfide solid electrolytes (SEs), the wet‐slurry process is ...imperative. Unfortunately, the poor chemical stability of sulfide SEs severely restrict available candidates for solvents and in turn polymeric binders. Moreover, the binders interrupt Li+‐ionic contacts at interfaces, resulting in the below par electrochemical performance. In this work, a new scalable slurry fabrication protocol for sheet‐type ASLB electrodes made of Li+‐conductive polymeric binders is reported. The use of intermediate‐polarity solvent (e.g., dibromomethane) for the slurry allows for accommodating Li6PS5Cl and solvate‐ionic‐liquid‐based polymeric binders (NBR‐Li(G3)TFSI, NBR: nitrile−butadiene rubber, G3: triethylene glycol dimethyl ether, LiTFSI: lithium bis(trifluoromethanesulfonyl)imide) together without suffering from undesirable side reactions or phase separation. The LiNi0.6Co0.2Mn0.2O2 and Li4Ti5O12 electrodes employing NBR‐Li(G3)TFSI show high capacities of 174 and 160 mA h g−1 at 30 °C, respectively, which are far superior to those using conventional NBR (144 and 76 mA h g−1). Moreover, high areal capacity of 7.4 mA h cm−2 is highlighted for the LiNi0.7Co0.15Mn0.15O2 electrodes with ultrahigh mass loading of 45 mg cm−2. The facilitated Li+‐ionic contacts at interfaces paved by NBR‐Li(G3)TFSI are evidenced by the complementary analysis from electrochemical and 7Li nuclear magnetic resonance measurements.
A new slurry‐fabricable solvate ionic liquid (SIL)‐based Li+‐conductive polymeric binder for all‐solid‐state lithium‐ion batteries is developed. Sheet‐type electrodes are tailored from a slurry using solvent with intermediate polarity (e.g., dibromomethane) which enables the accommodation of sulfide solid electrolytes and SIL together without suffering from any side reactions or phase separation. The resulting electrodes significantly outperform those made of conventional insulating binders.
A new, highly conductive (4.1 × 10−4 S cm−1 at 30 °C), highly deformable, and dry‐air‐stable glass 0.4LiI‐0.6Li4SnS4 is prepared using a homogeneous methanol solution. The solution process enables ...the wetting of any exposed surface of the active materials with highly conductive solidified electrolytes (0.4LiI‐0.6Li4SnS4), resulting in considerable improvements in the electrochemical performance of these electrodes over conventional mixture electrodes.
Owing to their potential for greater safety, higher energy density, and scalable fabrication, bulk-type all-solid-state lithium-ion batteries (ASLBs) employing deformable sulfide superionic ...conductors are considered highly promising for applications in battery electric vehicles. While fabrication of sheet-type electrodes is imperative from the practical point of view, reports on relevant research are scarce. This might be attributable to issues that complicate the slurry-based fabrication process and/or issues with ionic contacts and percolation. In this work, we systematically investigate the electrochemical performance of conventional dry-mixed electrodes and wet-slurry fabricated electrodes for ASLBs, by varying the different fractions of solid electrolytes and the mass loading. This information calls for a need to develop well-designed electrodes with better ionic contacts and to improve the ionic conductivity of solid electrolytes. As a scalable proof-of-concept to achieve better ionic contacts, a premixing process for active materials and solid electrolytes is demonstrated to significantly improve electrochemical performance. Pouch-type 80 × 60 mm2 all-solid-state LiNi0·6Co0·2Mn0·2O2/graphite full-cells fabricated by the slurry process show high cell-based energy density (184 W h kg−1 and 432 W h L−1). For the first time, their excellent safety is also demonstrated by simple tests (cutting with scissors and heating at 110 °C).
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•Slurry-mixed electrodes using polymeric binders suffer from poor ionic contacts.•Premixing of active materials and SEs significantly increases the capacity.•Pouch-type ASLBs with high energy density (184 W h kgcell−1) are fabricated.•Excellent safety for pouch-type ASLBs is demonstrated by cutting and heating tests.
The digital twin technique has been broadly utilized to efficiently and effectively predict the performance and problems associated with real objects via a virtual replica. However, the ...digitalization of twin electrochemical systems has not been achieved thus far, owing to the large amount of required calculations of numerous and complex differential equations in multiple dimensions. Nevertheless, with the help of continuous progress in hardware and software technologies, the fabrication of a digital twin‐driven electrochemical system and its effective utilization have become a possibility. Herein, a digital twin‐driven all‐solid‐state battery with a solid sulfide electrolyte is built based on a voxel‐based microstructure. Its validity is verified using experimental data, such as effective electronic/ionic conductivities and electrochemical performance, for LiNi0.70Co0.15Mn0.15O2 composite electrodes employing Li6PS5Cl. The fundamental performance of the all‐solid‐state battery is scrutinized by analyzing simulated physical and electrochemical behaviors in terms of mass transport and interfacial electrochemical reaction kinetics. The digital twin model herein reveals valuable but experimentally inaccessible time‐ and space‐resolved information including dead particles, specific contact area, and charge distribution in the 3D domain. Thus, this new computational model is bound to rapidly improve the all‐solid‐state battery technology by saving the research resources and providing valuable insights.
A digital twin‐driven all‐solid‐state battery provides insight into physical and electrochemical behaviors. It is anticipated that this digital twin model will be widely utilized to improve the electrochemical performance of all‐solid‐state batteries in the near future.
Owing to an absence or lack of soft (and/or liquid) components, electrochemo‐mechanical effects are imperative for all‐solid‐state batteries (ASBs) based on inorganic solid electrolytes (SEs). As ...this aspect has been overlooked, relevant investigation has remained scarce. In this work, the development of a new operando differential electrochemical pressiometry (DEP) for ASBs is reported. The time‐ (or capacity‐) derivative differential pressure signals (dP/dt or dP/dQ) reflecting corresponding differential volume changes of electrode active materials feature the specific state of charges (SOCs). This finding leads to a precise estimation of the SOCs of graphite (Gr) electrodes in LiNi0.70Co0.15Mn0.15O2 (NCM)/Gr all‐solid‐state full cells using sulfide SEs with varying capacity ratios of negative to positive electrodes (n/p ratios); this is corroborated by complementary analysis using a three‐electrode electrochemical cell and ex situ X‐ray diffraction measurements. Furthermore, electrochemo‐mechanical behaviors of NCM/Gr full cells with Gr electrodes employing SEs excluding or including reductively unstable Li10GeP2S12 are investigated. Notable volume changes caused by lithiation of Li10GeP2S12 are detected. Importantly, significantly delayed SOC for Gr caused by a severe side reaction with Li10GeP2S12 is disclosed by the operando DEP result.
A new operando differential electrochemical pressiometry for all‐solid‐state batteries is developed. Precisely measured pressure changes in real time feature specific phase transitions of graphite in LiNi0.70Co0.15Mn0.15O2/graphite and are applied to the estimation of the state of charges. Its validity is verified for LiNi0.70Co0.15Mn0.15O2/graphite full cells i) with varying n/p ratios and ii) employing reductively unstable Li10GeP2S12 for graphite electrodes.
Most inorganic solid electrolytes (SEs) suffer from narrow intrinsic electrochemical windows and incompatibility with electrode materials, which results in the below par electrochemical performances ...of all-solid-state Li-ion or Li batteries (ASLBs). Unfortunately, in-depth understanding on the interfacial evolution and interfacial engineering via scalable protocols for ASLBs to mitigate these issues are at an infancy stage. Herein, we report on rationally designed Li3BO3–Li2CO3 (LBO-LCO or Li3–x B1–x C x O3 (LBCO)) coatings for LiCoO2 in ASLBs employing sulfide SE of Li6PS5Cl. The new aqueous-solution-based LBO-coating protocol allows us to convert the surface impurity on LiCoO2 and Li2CO3, into highly Li+-conductive LBCO layers (6.0 × 10–7 S cm–1 at 30 °C for LBCO vs 1.4 × 10–9 S cm–1 at 100 °C for Li2CO3 or 1.4 × 10–9 S cm–1 at 30 °C for LBO), which also offer interfacial stability with sulfide SE. By applying these high-surface-coverage LBCO coatings, significantly enhanced electrochemical performances are obtained in terms of capacity, rate capability, and durability. It is elucidated that the LBCO coatings suppress the evolution of detrimental mixed conducting interphases containing Co3S4 and effectively passivate the interfaces by the formation of alternative interface phases.
Polymeric binders that can undergo slurry fabrication and minimize the disruption of interfacial Li+ contact are imperative for sheet‐type electrodes and solid electrolyte films in practical ...all‐solid‐state Li batteries (ASLBs). Although dry polymer electrolytes (DPEs) are a plausible alternative, their use is complicated by the severe reactivity of sulfide solid electrolytes and the need to dissolve Li salts. In this study, a new scalable fabrication protocol for a Li+‐conductive DPE‐type binder, nitrile‐butadiene rubber (NBR)‐LiTFSI, is reported. The less‐polar dibromomethane and more‐polar hexyl butyrate in cosolvents work synergistically to dissolve NBR and LiTFSI, while preserving Li6PS5Cl0.5Br0.5. It is found that the dispersion of NBR can be controlled by the fraction of the antisolvent (hexyl butyrate), which in turn affects the corresponding performance of the ASLBs. Sheet‐type LiNi0.70Co0.15Mn0.15O2 electrodes tailored using NBR‐LiTFSI outperform those prepared using the conventional insulating binder (NBR) in terms of capacity (163 vs 147 mA h g−1) and initial Coulombic efficiency (78.9 vs 70.4%), which is attributed to the facilitated interfacial Li+ transport, as confirmed by 6Li nuclear magnetic resonance and electrochemical measurements. Moreover, NBR‐LiTFSI is functional at 70 °C and in a graphite anode. Finally, the promising performance of pouch‐type LiNi0.70Co0.15Mn0.15O2/graphite ASLBs is also demonstrated.
A new scalable slurry fabrication protocol using a cosolvent targeting dry polymer electrolyte (DPE)‐based binders for all‐solid‐state batteries is developed. Binder dispersion is controlled by adjusting the ratios in the cosolvent, affecting the electrochemical performance. LiNii0.70Co0.15Mn0.15O2 and graphite electrodes tailored from slurries using cosolvents of dibromomethane and hexyl butyrate, targeting the accommodation of DPE and Li6PS5Cl0.5Br0.5, exhibit significantly improved performance.
Bulk‐type all‐solid‐state lithium‐ion batteries (ASLBs) for large‐scale energy‐storage applications have emerged as a promising alternative to conventional lithium‐ion batteries (LIBs) owing to their ...superior safety. However, the electrochemical performance of bulk‐type ASLBs is critically limited by the low ionic conductivity of solid electrolytes (SEs) and poor ionic contact between the active materials and SEs. Herein, highly conductive (0.14 mS cm−1) and dry‐air‐stable SEs (Li4SnS4) are reported, which are prepared using a scalable aqueous‐solution process. An active material (LiCoO2) coated by solidified Li4SnS4 from aqueous solutions results in a significant improvement in the electrochemical performance of ASLBs. Side‐effects of the exposure of LiCoO2 to aqueous solutions are minimized by using predissolved Li4SnS4 solution.
Superionic conductor: Highly conductive (0.14 mS cm−1) and dry‐air‐stable Li4SnS4 is obtained by a scalable aqueous‐solution process, which enables direct wetting of solid electrolytes onto active material (LiCoO2). Moreover, the basicity of aqueous Li4SnS4 solution alleviates detrimental surface degradation of LiCoO2 upon contact with water.
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