Project description:Li-rich antiperovskite materials are promising candidates as inorganic solid electrolytes (ISEs) for all-solid-state Li-ion batteries (ASSLIBs). However, the material faces several pressing issues for its application, concerning the phase stability and electrochemical stability of the synthesized material and the Li-ion transport mechanism in it. Herein, we performed first-principles computational studies on the phase stability, interfacial stability, defect chemistry, and electronic/ionic transport properties of Li2OHBr material. The calculation results show that the Li2OHBr is thermodynamically metastable at 0 K and can be synthesized experimentally. This material exhibits a wider intrinsic electrochemical stability window (0.80-3.15 V) compared with sulfide solid electrolytes. Moreover, the Li2OHBr displays significant chemical stability when in contact with typical cathode materials (LiCoO2, LiMn2O4, LiFePO4) and moisture. The dominant defects of Li2OHBr are predicted to be VLi- and Lii+, corresponding to lower Li-ion migration barriers of 0.38 and 0.49 eV, respectively, while the replacement of some of the OH- by F- is shown to be effective in decreasing migration barriers in Li2OHBr. These findings provide a theoretical framework for further designing high performance ISEs.
Project description:Garnet-type Li6.4La3Zr1.4Ta0.6O7 (LLZTO) is regarded as a highly competitive next-generation solid-state electrolyte for all-solid-state lithium batteries owing to reliable safety, a wide electrochemical operation window of 0-6 V versus Li+/Li, and a superior stability against Li metal. Nevertheless, insufficient interface contacts caused by pores, along with Li dendrite growth at these voids and grain boundary regions, have hindered their commercial application. Herein, we suggest a method to produce high-quality LLZTO using LiAlO2 (LAO) as a chemical additive that leads to an improved microstructure with larger grain size (∼25 μm), a high relative density (∼96%), lower porosity (∼3.7%), and continuous secondary phases in grain boundary regions. This improved structure results in (i) improved Li-ion conductivity and enhanced interfacial resistance between Li metal and LLZTO by a denser structure with fewer pores and (ii) suppression of Li dendrite penetration in the electrolyte by secondary phases in grain boundary regions.
Project description:Designing highly conductive and (electro)chemical stable inorganic solid electrolytes using cost-effective materials is crucial for developing all-solid-state batteries. Here, we report halide nanocomposite solid electrolytes (HNSEs) ZrO2(-ACl)-A2ZrCl6 (A = Li or Na) that demonstrate improved ionic conductivities at 30 °C, from 0.40 to 1.3 mS cm-1 and from 0.011 to 0.11 mS cm-1 for Li+ and Na+, respectively, compared to A2ZrCl6, and improved compatibility with sulfide solid electrolytes. The mechanochemical method employing Li2O for the HNSEs synthesis enables the formation of nanostructured networks that promote interfacial superionic conduction. Via density functional theory calculations combined with synchrotron X-ray and 6Li nuclear magnetic resonance measurements and analyses, we demonstrate that interfacial oxygen-substituted compounds are responsible for the boosted interfacial conduction mechanism. Compared to state-of-the-art Li2ZrCl6, the fluorinated ZrO2-2Li2ZrCl5F HNSE shows improved high-voltage stability and interfacial compatibility with Li6PS5Cl and layered lithium transition metal oxide-based positive electrodes without detrimentally affecting Li+ conductivity. We also report the assembly and testing of a Li-In||LiNi0.88Co0.11Mn0.01O2 all-solid-state lab-scale cell operating at 30 °C and 70 MPa and capable of delivering a specific discharge of 115 mAh g-1 after almost 2000 cycles at 400 mA g-1.
Project description:The performance of nanocomposite electrodes prepared by controlled ball-milling of TiS₂ and a Li₂S-P₂S₅ solid electrolyte (SE) for all-solid-state lithium batteries is investigated, focusing on the evolution of the microstructure. Compared to the manually mixed electrodes, the ball-milled electrodes exhibit abnormally increased first-charge capacities of 416 mA h g(-1) and 837 mA h g(-1) in the voltage ranges 1.5-3.0 V and 1.0-3.0 V, respectively, at 50 mA g(-1) and 30°C. The ball-milled electrodes also show excellent capacity retention of 95% in the 1.5-3.0 V range after 60 cycles as compared to the manually mixed electrodes. More importantly, a variety of characterization techniques show that the origin of the extra Li(+) storage is associated with an amorphous Li-Ti-P-S phase formed during the controlled ball-milling process.
Project description:Utilization of lithium (Li) metal anode in solid-state batteries (SSBs) with sulfide solid-state electrolyte (SSE) is hindered by the instable Li/SSE interface. A general solution to solve this problem is to place an expensive indium (In) foil between the SSE and Li, while it decreases the output voltage and thus the energy density of the battery. In this work, an alternative strategy is demonstrated to boost the cycling performances of SSB by wrapping a graphene oxide (GO) layer on the anode. According to density functional theory results, initial deposition of a thin Li layer on the defective GO sheets leads to the formation of a dipole structure, due to the electron-withdrawing ability of GO acting on Li. By incorporating GO sheets in a nanocomposite of copper-cuprous oxide-GO (Cu-Cu2O-GO, CCG), a composite Li anode enables a high coulombic efficiency above 99.5% over 120 cycles for an SSB using Li10GeP2S12 SSE and LiCoO2 cathode, and the sulfide SSE is not chemically decomposed after cycling. The highest occupied molecule orbital/lowest unoccupied molecular orbital energy gap of this Li/GO dipole structure likely stretches over those of Li and sulfide SSE, enabling stabilized Li/SSE interface that can replace the expensive In layer as Li protective structure in SSBs.
Project description:Argyrodite-type Li6 PS5 Cl (LPSCl) has attracted much attention as a solid electrolyte for all-solid-state batteries (ASSBs) because of its high ionic conductivity and good mechanical flexibility. LPSCl, however, has challenges of translating research into practical applications, such as irreversible electrochemical degradation at the interface between LPSCl and cathode materials. Even for Li-ion batteries (LIBs), liquid electrolytes have the same issue as electrolyte decomposition due to interfacial instability. Nonetheless, current LIBs are successfully commercialized because functional electrolyte additives give rise to the formation of stable cathode-electrolyte interphase (CEI) and solid-electrolyte interphase (SEI) layers, leading to supplementing the interfacial stability between electrolyte and electrode. Herein, inspired by the role of electrolyte additives for LIBs, trimethylsilyl compounds are introduced as solid electrolyte additives for improving the interfacial stability between sulfide-based solid electrolytes and cathode materials. 2-(Trimethylsilyl)ethanethiol (TMS-SH), a solid electrolyte additive, is oxidatively decomposed during charge, forming a stable CEI layer. As a result, the CEI layer derived from TMS-SH suppresses the interfacial degradation between LPSCl and LiCoO2 , thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2 , such as superior cycle life over 2000 cycles (85.0% of capacity retention after 2000 cycles).
Project description:Coupling high-capacity cathode and Li-anode with solid-state electrolyte has been demonstrated as an effective strategy for increasing the energy densities and safety of rechargeable batteries. However, the limited ion conductivity, the large interfacial resistance, and unconstrained Li-dendrite growth hinder the application of solid-state Li-metal batteries. Here, a poly(ether-urethane)-based solid-state polymer electrolyte with self-healing capability is designed to reduce the interfacial resistance and provides a high-performance solid-state Li-metal battery. With its dynamic covalent disulfide bonds and hydrogen bonds, the proposed solid-state polymer electrolyte exhibits excellent interfacial self-healing ability and maintains good interfacial contact. Full cells are assembled with the two integrated electrodes/electrolytes. As a result, the Li||Li symmetric cells exhibit stable long-term cycling for more than 6000 h, and the solid-state Li-S battery shows a prolonged cycling life of 700 cycles at 0.3 C. The use of ultrasound imaging technology shows that the interfacial contact of the integrated structure is much better than those of traditional laminated structure. This work provides an interesting interfacial dual-integrated strategy for designing high-performance solid-state Li-metal batteries.
Project description:Poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) is considered as a promising solid-state electrolyte for all-solid-state lithium batteries (ASSLBs). Nevertheless, the poor interfacial stability with high-voltage cathode materials (e.g., LiCoO2) restricts its application in high energy density solid-state batteries. Herein, high-voltage stable Li3AlF6 protective layer is coated on the surface of LiCoO2 particle to improve the performance and investigate the failure mechanism of PEO-based ASSLBs. The phase transition unveils that chemical redox reaction occurs between the highly reactive LiCoO2 surface and PEO-based SPE, resulting in structure collapse of LiCoO2, hence the poor cycle performance of PEO-based ASSLBs with LiCoO2 at charging voltage of 4.2 V vs Li/Li+. By sharp contrast, no obvious structure change can be found at the surface of Li3AlF6-coated LiCoO2, and the original layered phase was well retained. When the charging voltage reaches up to 4.5 V vs Li/Li+, the intensive electrochemical decomposition of PEO-based SPE occurs, leading to the constant increase of cell impedance and directly causing the poor performance. This work not only provides important supplement to the failure mechanism of PEO-based batteries with LiCoO2, but also presents a universal strategy to retain structure stability of cathode-electrolyte interface in high-voltage ASSLBs.
Project description:While great effort has been focused on bulk material design for high-performance All Solid-State Batteries (ASSBs), solid-solid interfaces, which typically extend over a nanometer regime, have been identified to severely impact cell performance. Major challenges are Li dendrite penetration along the grain boundary network of the Solid-State Electrolyte (SSE) and reductive decomposition at the electrolyte/electrode interface. A naturally forming nanoscale complexion encapsulating ceramic Li1+xAlxTi2-x(PO4)3 (LATP) SSE grains has been shown to serve as a thin protective layer against such degradation mechanisms. To further exploit this feature, we study the interfacial doping of divalent Mg2+ into LATP grain boundaries. Molecular Dynamics simulations for a realistic atomistic model of the grain boundary reveal Mg2+ to be an eligible dopant candidate as it rarely passes through the complexion and thus does not degrade the bulk electrolyte performance. Tuning the interphase stoichiometry promotes the suppression of reductive degradation mechanisms by lowering the Ti4+ content while simultaneously increasing the local Li+ conductivity. The Mg2+ doping investigated in this work identifies a promising route towards active interfacial engineering at the nanoscale from a computational perspective.