High-voltage Oxide Research Articles

Self-Templated 3D Sulfide-Based Solid Composite Electrolyte for Solid-State Sodium Metal Batteries.

Rechargeable solid-state sodium metal batteries (SSMBs) experience growing attention owing to the increased energy density (vs Na-ion batteries) and cost-effective materials. Inorganic sulfide-based Na-ion conductors also possess significant potential as promising solid electrolytes (SEs) in SSMBs. Nevertheless, due to the highly reactive Na metal, poor interface compatibility is the biggest obstacle for inorganic sulfide solid electrolytes such as Na3SbS4 to achieve high performance in SSMBs. To address such electrochemical instability at the interface, new design of sulfide SE nanostructures and interface engineering are highly essential. In this work, a facile and straightforward approach is reported to prepare 3D sulfide-based solid composite electrolytes (SCEs), which utilize porous Na3SbS4 (NSS) as a self-templated framework and fill with a phase transition polymer. The 3D structured SCEs display obviously improved interface stability toward Na metal than pristine sulfide. The assembled SSMBs (with TiS2 or FeS2 as cathodes) deliver outstanding electrochemical cycling performance. Moreover, the cycling of high-voltage oxide cathode Na0.67Ni0.33Mn0.67O2 (NNMO) is also demonstrated in SSMBs using 3D sulfide-based SCEs. This study presents a novel design on the self-templated nanostructure of SCEs, paving the way for the advancement of high-energy sodium metal batteries.

Expanding the Phase Space for Halide-Based Solid Electrolytes: Li-Mg-Zr-Cl Spinels.

Chloride-based solid electrolytes are intriguing materials owing to their high Li+ ionic conductivity and electrochemical compatibility with high-voltage oxide cathodes for all-solid-state lithium batteries. However, the leading examples of these materials are limited to trivalent metals (e.g., Sc, Y, and In), which are expensive and scarce. Here, we expand this materials family by replacing the trivalent metals with a mix of di- and tetra-valent metals (e.g., Mg2+ and Zr4+). We synthesize Li2Mg1/3Zr1/3Cl4 in the spinel crystal structure and compare its properties with the high-performing Li2Sc2/3Cl4 that has been reported previously. We find that Li2Mg1/3Zr1/3Cl4 has lower ionic conductivity (0.028 mS/cm at 30 °C) than the isostructural Li2Sc2/3Cl4 (1.6 mS/cm at 30 °C). We attribute this difference to a disordered arrangement of Mg2+ and Zr4+ in Li2Mg1/3Zr1/3Cl4, which may block Li+ migration pathways. However, we show that aliovalent substitution across the Li2-z Mg1-3z/2Zr z Cl4 series between Li2MgCl4 and Li2ZrCl6 can boost ionic conductivity with increasing Zr4+ content, presumably due to the introduction of Li+ vacancies. This work opens a new dimension for halide-based solid electrolytes, accelerating the development of low-cost solid-state batteries.

Interphase engineering by tunable redox of (p-d) π-bond additive toward extended lifespan of sodium-ion batteries

The durability of the cathode and anode interphases is critical for long-term stable cycling of sodium-ion batteries, however, difficult to achieve precise modulation in conventional carbonate-based electrolytes. Herein, from the perspective of functional additives, the sulfur-containing interphase engineering is introduced by the cyclic sulfate esters with tunable redox mechanism, which are oriented to alter specific decomposition and film-forming pathways on the surface of the cathode and anode, compensating for the deficiencies of the fluorinated interphases, such as improving the inhomogeneous and fragile characteristics, while enhancing the ion transport efficiency. As a result, the cells based on hard carbon (HC) and high voltage Na3V2(PO4)2O2F (NVPF) demonstrate excellent cycling stability (1000 and 8000 cycles with more than 80 % and 83 % capacity retention, respectively). Moreover, the assembled HC//NVPF full cell also achieves a cycle life of more than 2500 cycles with a capacity retention of 91%, which is far superior to that of conventional carbonate electrolytes. Furthermore, the high-voltage oxide cathode also demonstrates extended cycling stability (80 % capacity retention after 300 cycles). In short, the proposed sulfur-based additive strategy enables to effectively improve the problems encountered in carbonate-based electrolytes, providing certain reference and application value.

Amorphous Oxyhalide Matters for Achieving Lithium Superionic Conduction.

The recently surged halide-based solid electrolytes (SEs) are great candidates for high-performance all-solid-state batteries (ASSBs), due to their decent ionic conductivity, wide electrochemical stability window, and good compatibility with high-voltage oxide cathodes. In contrast to the crystalline phases in halide SEs, amorphous components are rarely understood but play an important role in Li-ion conduction. Here, we reveal that the presence of amorphous component is common in halide-based SEs that are prepared via mechanochemical method. The fast Li-ion migration is found to be associated with the local chemistry of the amorphous proportion. Taking Zr-based halide SEs as an example, the amorphization process can be regulated by incorporating O, resulting in the formation of corner-sharing Zr-O/Cl polyhedrons. This structural configuration has been confirmed through X-ray absorption spectroscopy, pair distribution function analyses, and Reverse Monte Carlo modeling. The unique structure significantly reduces the energy barriers for Li-ion transport. As a result, an enhanced ionic conductivity of (1.35 ± 0.07) × 10-3 S cm-1 at 25 °C can be achieved for amorphous Li3ZrCl4O1.5. In addition to the improved ionic conductivity, amorphization of Zr-based halide SEs via incorporation of O leads to good mechanical deformability and promising electrochemical performance. These findings provide deep insights into the rational design of desirable halide SEs for high-performance ASSBs.

Polymeric ionic conductor networks enable stable cycling of high-voltage lithium metal batteries using solid-state poly-ether electrolytes

Integrating high-voltage oxide cathodes with solid electrolytes significantly advances energy storage devices. Although poly(1,3-dioxolane) (PDOL)-based solid-state electrolytes are easy to prepare and compatible with lithium anodes, they suffer from poor...

The Universal Super Cation-Conductivity in Multiple-cation Mixed Chloride Solid-State Electrolytes.

As exciting candidates for next-generation energy storage, all-solid-state lithium batteries (ASSLBs) are highly dependent on advanced solid-state electrolytes (SSEs). Here, using cost-effective LaCl3 and CeCl3 lattice (UCl3 -type structure) as the host and further combined with a multiple-cation mixed strategy, we report a series of UCl3 -type SSEs with high room-temperature ionic conductivities over 10-3 S cm-1 and good compatibility with high-voltage oxide cathodes. The intrinsic large-size hexagonal one-dimensional channels and highly disordered amorphous phase induced by multi-metal cation species are believed to trigger fast multiple ionic conductions of Li+ , Na+ , K+ , Cu+ , and Ag+ . The UCl3 -type SSEs enable a stable prototype ASSLB capable of over 3000 cycles and high reversibility at -30 °C. Further exploration of the brand-new multiple-cation mixed chlorides is likely to lead to the development of advanced halide SSEs suitable for ASSLBs with high energy density.

Electrolyte Reactivity on the MgV2O4 Cathode Surface.

Predictive understanding of the molecular interaction of electrolyte ions and solvent molecules and their chemical reactivity on electrodes has been a major challenge but is essential for addressing instabilities and surface passivation that occur at the electrode-electrolyte interface of multivalent magnesium batteries. In this work, the isolated intrinsic reactivities of prominent chemical species present in magnesium bis(trifluoromethanesulfonimide) (Mg(TFSI)2) in diglyme (G2) electrolytes, including ionic (TFSI-, [Mg(TFSI)]+, [Mg(TFSI):G2]+, and [Mg(TFSI):2G2]+) as well as neutral molecules (G2) on a well-defined magnesium vanadate cathode (MgV2O4) surface, have been studied using a combination of first-principles calculations and multimodal spectroscopy analysis. Our calculations show that nonsolvated [Mg(TFSI)]+ is the strongest adsorbing species on the MgV2O4 surface compared with all other ions while partially solvated [Mg(TFSI):G2]+ is the most reactive species. The cleavage of C-S bonds in TFSI- to form CF3- is predicted to be the most desired pathway for all ionic species, which is followed by the cleavage of C-O bonds of G2 to yield CH3+ or OCH3- species. The strong stabilization and electron transfer between ionic electrolyte species and MgV2O4 is found to significantly favor these decomposition reactions on the surface compared with intrinsic gas-phase dissociation. Experimentally, we used state-of-the-art ion soft landing to selectively deposit mass-selected TFSI-, [Mg(TFSI):G2]+, and [Mg(TFSI):2G2]+ on a MgV2O4 thin film to form a well-defined electrolyte-MgV2O4 interface. Analysis of the soft-landed interface using X-ray photoelectron, X-ray absorption near-edge structure, electron energy-loss spectroscopies, as well as transmission electron microscopy confirmed the presence of decomposition species (e.g., MgFx, carbonates) and the higher amount of MgFx with [Mg(TFSI):G2]+ formed in the interfacial region, which corroborates the theoretical observation. Overall, these results indicate that Mg2+ desolvation results in electrolyte decomposition facilitated by surface adsorption, charge transfer, and the formation of passivating fluorides on the MgV2O4 cathode surface. This work provides the first evidence of the primary mechanisms leading to electrolyte decomposition at high-voltage oxide surfaces in multivalent batteries and suggests that the design of new, anodically stable electrolytes must target systems that facilitate cation desolvation.

Using Synchrotron Techniques, Investigation of Electrochemical Interfaces in Ni-Rich NMC and Sulfide Electrolytes in All-Solid-State Lithium Metal Batteries

a Nano-electrochemistry Laboratory, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan, R.O.C b National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan, R.O.CIn all-solid-state lithium metal batteries enable long cyclability of high voltage oxides cathode persistent problem for the large scale application as their underprivileged interfacial steadiness in contrast to sulfide solid-state electrolyte. In this context, the interfaces of the solid electrolyte and Ni-rich NMC811 active material are looked upon as interfacial chemical responses induced by delithiation. In this study, we monitor the impedance progress at the unstable electrode|electrolyte interface due to the electrochemical interfacial response and help us understand the complex nature of reactivity and degradation kinetics with the solid-solid interface redox decomposition, which makes decoupling each effect difficult. we investigated the interfacial phenomenon between LPSC and high voltage cathode NMC811. The effects of spontaneous retort by the side of the interface were separated, and the intrinsic electrochemical decomposition of LPSC was quantified. Moreover, we show that the notch of interfacial degradation surges and the presence of oxidation mechanisms. At the higher delithiation stage, the cathode might twitch structural defenselessness and oxygen utter and resulting in further stark degradation. This complex kinetic degradation behavior was investigated at the solid-solid interface in a delithiation NMC811 and SSE based on the local oxidation state of NMC811, and LPSC SE interfacial chemical response. In this work, we used various characterization techniques to investigate the interfacial phenomenon between LPSC|NMC811 combining EIS and advanced synchrotron techniques such as sXAS, XPS, XRF-XANES mapping, and In-situ Raman spectroscopy. Keywords: delithiation, Ni-rich cathode, Sulfide-solid-state electrolyte, interfacial reaction, Synchrotron XPS, XRF.

(Battery Division Student Research Award Sponsored by Mercedes-Benz Research & Development) Energy Storage with the Abundant Divalent Metal Batteries

The transitions to electric vehicles and renewable power sources are not only a change of personal lifestyles but also tactical approaches to a sustainable future for us and our offspring, in which the energy supply will no longer be at the expense of natural resource depletion and environmental damage. The cornerstones of this sensational transition are rechargeable batteries, particularly lithium-ion batteries (LIBs). And it is not difficult to imagine that the consumption and demand for LIBs will skyrocket in the foreseeable future if EVs dominate the market. However, the massive growth of the LIBs industry will lead to another resource crisis due to the scarcity of materials used in LIBs, such as lithium and cobalt1.While battery recycling could partially relieve these issues, it is desirable to find abundant and cheap substitutes, especially for the regions where lithium resources are less accessible. Magnesium (Mg) and calcium (Ca) are among the most abundant elements in the earth's crust (>1000 times more abundant than lithium)2. More importantly, they store charges by two electron-transfer reactions and have fairly low redox potentials3. When appropriate high-potential cathodes are paired with Mg or Ca metal, the resulting rechargeable magnesium and calcium batteries (RMBs and RCBs) could render energy densities comparable to or even higher than LIBs4. However, these systems are always typified by irreversibility. The underlying reason is that it is much more difficult to desolvate and transfer the divalent Mg2+ or Ca2+ than Li+ at the electrolyte-electrode interface and inside electrode materials, and the extra energy required for reaction sometimes causes undesirable parasitic reactions such as electrolyte decomposition and irreversible phase transition in the intercalating cathodes (especially high-voltage oxide cathodes) 5-7. These issues have plagued the practicality of RMBs for over a decade.In this study, we found that the charge transfer kinetics involving Mg2+ and Ca2+ in both transitional metal oxide cathodes and the metal anodes can be significantly enhanced with methoxylethyleneamine chelants in the solvation sheath8. A peculiar observation is that the methoxylethyleneamine chelants demonstrate a much higher affinity toward the Mg2+ than the ether solvent as demonstrated by the Nuclear Magnetic Resonance (NMR) results, requiring higher energy to remove them from the solvation sheath. However, the large desolvation energies do not translate to more sluggish reaction kinetics; on the contrary, low overpotentials were observed. With a combined effort of the surface chemistry analysis with X-ray photoelectron spectroscopy, solvation sheath characterization with NMR and Raman spectroscopy, electrochemical modeling with Marcus-Chidsey kinetics for interfacial electron transfer, and quantum chemistry calculations, we have identified that the cause of such unconventional behavior is that the charge transfer reactions occur without desolvation. This process is significantly facilitated by the polarizable structures of the chelants in the solvation sheath. By boosting the main reaction kinetics, the undesirable side reactions are suppressed without the solid electrolyte interface as in LIBs, thus opening up a completely different electrolyte design approach to stabilize high-energy RMBs and RCBs. Furthermore, this achievement could help reduce reliance on mining raw materials to build LIBs and provide cheaper and safer options for future energy storage. Reference Herrington, R. Nature Reviews Materials 2021, 6, 456-458. Muldoon, J.; Bucur, C. B.; Gregory, T. Quest for Nanoaqueous Multivalent Secondary Batteries Magnesium and Beyond. Chemical Reviews 2014, 114, 11683-11720. Li, M.; Lu, J.; Ji, X.; Li, Y.; Shao, Y.; Chen, Z.; Zhong, C.; Amine, K. Design strategies for nonaqueous multivalent-ion and monovalent-ion battery anodes. Nature Reviews Materials 2020, 5, 276-294. Canepa, P.; Gautam, G. S.; Hannah, D. C.; Malik, R.; Liu, M.; Gallagher, K. G.; Persson, K. A.; Ceder, G. Odyssey of Multivalent Cathode Materials: Open Questions and Future Challenges. Chemical Reviews 2017, 117, 4287-4341.

Li3InCl6-coated LiCoO2 for high-performance all solid-state batteries

Halide solid electrolytes (HSEs) could be coated on high-voltage oxide cathodes at molecular-level via a solution process, which is highly favorable for reducing the interface impedance. However, during the preparation of composite cathodes, hydrate intermediates of HSEs are easily hydrolyzed to produce inactive impurities. In this work, the vacuum drying assisted method facilitates the generation of pure Li3InCl6 (LIC) on the surface of LiCoO2 (LCO) to improve the electrolyte/electrode solid–solid interface as well as the electrochemical stability of solid electrolyte under high voltage. By introducing Li7P3S11 as an anode buffer layer, 30 wt. %-LIC-coated LCO demonstrates high specific capacity of 121.7 mAh g−1 and good cycling stability. Our study highlights a promising method to build advanced composite cathodes for all-solid-state batteries.

Stacking Faults Assist Lithium-Ion Conduction in a Halide-Based Superionic Conductor.

In the pursuit of urgently needed, energy dense solid-state batteries for electric vehicle and portable electronics applications, halide solid electrolytes offer a promising path forward with exceptional compatibility against high-voltage oxide electrodes, tunable ionic conductivities, and facile processing. For this family of compounds, synthesis protocols strongly affect cation site disorder and modulate Li+ mobility. In this work, we reveal the presence of a high concentration of stacking faults in the superionic conductor Li3YCl6 and demonstrate a method of controlling its Li+ conductivity by tuning the defect concentration with synthesis and heat treatments at select temperatures. Leveraging complementary insights from variable temperature synchrotron X-ray diffraction, neutron diffraction, cryogenic transmission electron microscopy, solid-state nuclear magnetic resonance, density functional theory, and electrochemical impedance spectroscopy, we identify the nature of planar defects and the role of nonstoichiometry in lowering Li+ migration barriers and increasing Li site connectivity in mechanochemically synthesized Li3YCl6. We harness paramagnetic relaxation enhancement to enable 89Y solid-state NMR and directly contrast the Y cation site disorder resulting from different preparation methods, demonstrating a potent tool for other researchers studying Y-containing compositions. With heat treatments at temperatures as low as 333 K (60 °C), we decrease the concentration of planar defects, demonstrating a simple method for tuning the Li+ conductivity. Findings from this work are expected to be generalizable to other halide solid electrolyte candidates and provide an improved understanding of defect-enabled Li+ conduction in this class of Li-ion conductors.

Fabricating a PVDF skin for PEO-based SPE to stabilize the interface both at cathode and anode for Li-ion batteries

Poly (ethylene oxide) (PEO)-based solid polymer electrolyte is always the most promising candidate for preparing thinner, lighter and safer lithium-ion batteries. However, the lithium dendrites growth of lithium anode and the high-voltage oxidation of cathode are easy to cause the PEO-based battery failure. The way to deal with the different challenges on both sides of the anode and cathode is pursued all the time. In this study, we reported a new strategy to construct the PVDF/PEO/PVDF three-layer structure for solid polymer electrolyte (marked as PVDF@PEO) using PVDF as the functional “skin”. The PVDF@PEO electrolyte can effectively prevent from the lithium dendrites, and shows a stable cycling life over 1000 h in the Li/PVDF@PEO/Li cell. In addition, the PVDF@PEO electrolyte exhibits higher oxidation resistance and can be matched with high-voltage LiCoO2 cathode. The Li/PVDF@PEO/ LiCoO2 cell delivered a specific capacity of about 150 mAh g−1 over 150 cycles and maintained good cycling stability. Our research provides insights that the polymer electrolytes constructed with PVDF functional “skin” can simultaneously meet the challenges of both anode and cathode in solid-state lithium-ion batteries (SSLIBs).

A 1.2 kV SiC MOSFET with Integrated Heterojunction Diode and P-shield Region

A 1.2 kV SiC MOSFET with an integrated heterojunction diode and p-shield region (IHP-MOSFET) was proposed and compared to a conventional SiC MOSFET (C-MOSFET) using numerical TCAD simulation. Due to the heterojunction diode (HJD) located at the mesa region, the reverse recovery time and reverse recovery charge of the IHP-MOSFET decreased by 62.5% and 85.7%, respectively. In addition, a high breakdown voltage (BV) and low maximum oxide electric field (EMOX) could be achieved in the IHP-MOSFET by introducing a p-shield region (PSR) that effectively disperses the electric field in the off-state. The proposed device also exhibited 3.9 times lower gate-to-drain capacitance (CGD) than the C-MOSFET due to the split-gate structure and grounded PSR. As a result, the IHP-MOSFET had electrically excellent static and dynamic characteristics, and the Baliga’s figure of merit (BFOM) and high frequency figure of merit (HFFOM) were increased by 37.1% and 72.3%, respectively. Finally, the switching energy loss was decreased by 59.5% compared to the C-MOSFET.

A stable cathode-solid electrolyte composite for high-voltage, long-cycle-life solid-state sodium-ion batteries

Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of the ion conductor Na3-xY1-xZrxCl6 (NYZC) that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 × 10−5 S cm−1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2 + NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40 °C. These findings highlight the immense potential of halides for SSSB applications.

Controlling Covalency and Anion Redox Potentials through Anion Substitution in Li-Rich Chalcogenides

Development of next-generation battery technologies is imperative in the pursuit of a clean energy future. Toward that end, battery chemistries capable of multielectron redox processes are at the forefront of studies on Li-based systems to increase the gravimetric capacity of the cathode. Multielectron processes rely either on the iterative redox of transition metal cations or redox involving both the transition metal cations and the anionic framework. Targeting coupled cation and anion redox to achieve multielectron charge storage is difficult, however, because the structure–property relationships that govern reversibility are poorly understood. In an effort to develop fundamental understanding of anion redox, we have developed a materials family that displays tunable anion redox over a range of potentials that are dependent on a systematic modification of the stoichiometry. We report anion redox in the chalcogenide solid solution Li2FeS2–ySey, wherein the mixing of the sulfide and selenide anions yields a controllable shift in the high voltage oxidation plateau. Electrochemical measurements indicate that reversible multielectron redox occurs across the solid solution. X-ray absorption spectroscopy supports the oxidation of both iron and selenium at high states of charge, while Raman spectroscopy indicates the formation of Se–Se dimers in Li2FeSe2 upon Li deintercalation, providing insight into the charge mechanism of the Li-rich iron chalcogenides. Anion substitution presents direct control over the functional properties of multielectron redox materials for next generation battery technologies.

Electrochemical Stability and Ionic Transport in Coating Materials for Mg Batteries

A major bottleneck for the development of Mg batteries is the identification of liquid electrolytes that are simultaneously compatible with the Mg-metal anode and high-voltage cathodes [1,2]. A viable strategy to widen the stability windows of current nonaqueous electrolytes is to introduce protective coating materials at the electrodes, where these materials are required to exhibit swift Mg transport. Using first-principles calculations we map the electrochemical stability windows for non-redox-active Mg binary and ternary compounds in order to identify potential coating materials for Mg batteries [3]. The ion mobility in a set of Mg-containing binary, ternary, and quaternary compounds spanning a wide chemical space will be also discussed. Combining mobility, electronic band gaps, and stability requirements, we identify MgSiN2, MgI2, MgBr2, MgSe, and MgS as potential coating materials against the highly reductive Mg metal anode [4], whereas MgAl2O4 and Mg(PO3)2 appear promising materials against high-voltage oxide cathodes (up to ∼3 V).

Solid-State Li-Ion Batteries Operating at Room Temperature Using New Borohydride Argyrodite Electrolytes.

Using a new class of (BH4)− substituted argyrodite Li6PS5Z0.83(BH4)0.17, (Z = Cl, I) solid electrolyte, Li-metal solid-state batteries operating at room temperature have been developed. The cells were made by combining the modified argyrodite with an In-Li anode and two types of cathode: an oxide, LixMO2 (M = ⅓ Ni, ⅓ Mn, ⅓ Co; so called NMC) and a titanium disulfide, TiS2. The performance of the cells was evaluated through galvanostatic cycling and Alternating Current AC electrochemical impedance measurements. Reversible capacities were observed for both cathodes for at least tens of cycles. However, the high-voltage oxide cathode cell shows lower reversible capacity and larger fading upon cycling than the sulfide one. The AC impedance measurements revealed an increasing interfacial resistance at the cathode side for the oxide cathode inducing the capacity fading. This resistance was attributed to the intrinsic poor conductivity of NMC and interfacial reactions between the oxide material and the argyrodite electrolyte. On the contrary, the low interfacial resistance of the TiS2 cell during cycling evidences a better chemical compatibility between this active material and substituted argyrodites, allowing full cycling of the cathode material, 240 mAhg−1, for at least 35 cycles with a coulombic efficiency above 97%.

In Situ Electrooxidation of Electrolyte Additive to Improve Capacity Retention in Li-Rich Layered Oxide Cathode, Li2RuO3

Conventional positive electrode materials for Li-ion technology utilize a Li+ intercalation mechanism charge-balanced by redox on transition metals within an oxide host lattice. Moving forward, multi-electron cathodes that gain capacity by contribution to the redox from the structural anions are of interest for the hybrid intercalation- and conversion-type chemistry during cycling. One such material, Li2RuO3, first studied by Goodenough and coworkers, exhibits high capacity but also a significant capacity loss after the first charge and long-term capacity fade. We suspect the capacity loss is due to structural distortions induced as the lattice accommodates the removal of Li+. Electrolyte additives with tailored chemistry can be an efficient and cost-effective way to stabilize structural changes and promote reversible cycling. Here, in situ, irreversibleelectrooxidation of soluble electrolyte additives at the cathode-electrolyte interface was investigated as a route to stabilizing the cathode surface. Electrooxidation causes dramatically improved capacity retention and stabilizes high-voltage oxidation processes in Li2RuO3. Through understanding how to stabilize structural distortions in Li-rich layered oxide cathodes, we hope to promote reversible cycling near theoretical capacity and target design principles for active electrolyte additives that enhance battery performance.

Revealing Nanoscale Solid-Solid Interfacial Phenomena for Long-Life and High-Energy All-Solid-State Batteries.

Enabling long cyclability of high-voltage oxide cathodes is a persistent challenge for all-solid-state batteries, largely because of their poor interfacial stabilities against sulfide solid electrolytes. While protective oxide coating layers such as LiNbO3 (LNO) have been proposed, its precise working mechanisms are still not fully understood. Existing literature attributes reductions in interfacial impedance growth to the coating's ability to prevent interfacial reactions. However, its true nature is more complex, with cathode interfacial reactions and electrolyte electrochemical decomposition occurring simultaneously, making it difficult to decouple each effect. Herein, we utilized various advanced characterization tools and first-principles calculations to probe the interfacial phenomenon between solid electrolyte Li6PS5Cl (LPSCl) and high-voltage cathode LiNi0.85Co0.1Al0.05O2 (NCA). We segregated the effects of spontaneous reaction between LPSCl and NCA at the interface and quantified the intrinsic electrochemical decomposition of LPSCl during cell cycling. Both experimental and computational results demonstrated improved thermodynamic stability between NCA and LPSCl after incorporation of the LNO coating. Additionally, we revealed the in situ passivation effect of LPSCl electrochemical decomposition. When combined, both these phenomena occurring at the first charge cycle result in a stabilized interface, enabling long cyclability of all-solid-state batteries.

Ionic Transport in Potential Coating Materials for Mg Batteries

A major bottleneck for the development of Mg batteries is the identification of liquid electrolytes that are simultaneously compatible with the Mg-metal anode and high-voltage cathodes. One strategy to widen the stability windows of current non-aqueous electrolytes is to introduce protective coating materials at the electrodes, where coating materials are required to exhibit swift Mg transport. In this work, we use a combination of first-principles calculations and ion-transport theory to evaluate the migration barriers for nearly 27 Mg-containing binary, ternary, and quaternary compounds spanning a wide chemical space. Combining mobility, electronic band gaps, and stability requirements, we identify MgSiN$_2$, MgI$_2$, MgBr$_2$, MgSe, and MgS as potential coating materials against the highly reductive Mg metal anode, and we find MgAl$_2$O$_4$ and Mg(PO$_3$)$_2$ to be promising materials against high-voltage oxide cathodes (up to $\sim$3~V).