Weak-Interaction Environment in a Composite Electrolyte Enabling Ultralong-Cycling High-Voltage Solid-State Lithium Batteries.

Poly(vinylidene fluoride) (PVDF)-based solid electrolytes with a Li salt-polymer-little residual solvent configuration are promising candidates for solid-state batteries. Herein, we clarify the microstructure of PVDF-based composite electrolyte at the atomic level and demonstrate that the Li+-interaction environment determines both interfacial stability and ion-transport capability. The polymer works as a "solid diluent" and the filler realizes a uniform solvent distribution. We propose a universal strategy of constructing a weak-interaction environment by replacing the conventional N,N-dimethylformamide (DMF) solvent with the designed 2,2,2-trifluoroacetamide (TFA). The lower Li+ binding energy of TFA forms abundant aggregates to generate inorganic-rich interphases for interfacial compatibility. The weaker interactions of TFA with PVDF and filler achieve high ionic conductivity (7.0 × 10-4 S cm-1) of the electrolyte. The solid-state Li||LiNi0.8Co0.1Mn0.1O2 cells stably cycle 4900 and 3000 times with cutoff voltages of 4.3 and 4.5 V, respectively, as well as deliver superior stability at -20 to 45 °C and a high energy density of 300 Wh kg-1 in pouch cells.

Dielectric Filler-Induced Hybrid Interphase Enabling Robust Solid-State Li Metal Batteries at High Areal Capacity.

The fillers in composite solid-state electrolyte are mainly responsible for the enhancement of the conduction of Li ions but barely regulate the formation of solid electrolyte interphase (SEI). Herein, a unique filler of dielectric NaNbO3 for the poly(vinylidene fluoride) (PVDF)-based polymer electrolyte, which is subjected to the exchange of Li+ and Na+ during cycling, is reported and the substituted Na+ is engaged in the construction of a fluorinated Li/Na hybrid SEI with high Young's modulus, facilitating the fast transport of Li+ at the interface at a high areal capacity and suppressing the Li dendrite growth. The dielectric NaNbO3 also induces the generation of high-dielectric ß phase of PVDF to promote the dissociation of Li salt. The Li/Li symmetrical cell exhibits a long-term dendrite-free cycling over 600 h at a high areal capacity of 3 mA h cm-2. The LiNi0.8Mn0.1Co0.1O2/Li solid-state cells with NaNbO3 stably cycle 2200 times at 2 C and that paired with high-loading cathode (10 mg cm-2) can stably cycle for 150 times and exhibit excellent performances at -20 °C. This work provides a novel design principle of fillers undertaking interfacial engineering in composite solid-state electrolytes for developing the safe and stable solid-state lithium metal battery.

A dielectric electrolyte composite with high lithium-ion conductivity for high-voltage solid-state lithium metal batteries.

The ionic conductivity of composite solid-state electrolytes does not meet the application requirements of solid-state lithium (Li) metal batteries owing to the harsh space charge layer of different phases and low concentration of movable Li+. Herein, we propose a robust strategy for creating high-throughput Li+ transport pathways by coupling the ceramic dielectric and electrolyte to overcome the low ionic conductivity challenge of composite solid-state electrolytes. A highly conductive and dielectric composite solid-state electrolyte is constructed by compositing the poly(vinylidene difluoride) matrix and the BaTiO3-Li0.33La0.56TiO3-x nanowires with a side-by-side heterojunction structure (PVBL). The polarized dielectric BaTiO3 greatly promotes the dissociation of Li salt to produce more movable Li+, which locally and spontaneously transfers across the interface to coupled Li0.33La0.56TiO3-x for highly efficient transport. The BaTiO3-Li0.33La0.56TiO3-x effectively restrains the formation of the space charge layer with poly(vinylidene difluoride). These coupling effects contribute to a quite high ionic conductivity (8.2 × 10-4 S cm-1) and lithium transference number (0.57) of the PVBL at 25 °C. The PVBL also homogenizes the interfacial electric field with electrodes. The LiNi0.8Co0.1Mn0.1O2/PVBL/Li solid-state batteries stably cycle 1,500 times at a current density of 180 mA g-1, and pouch batteries also exhibit an excellent electrochemical and safety performance.

Determining the Role of Ion Transport Throughput in Solid-State Lithium Batteries.

Solid-state lithium metal batteries (SSLMBs) are promising candidates for high-energy-density energy storage devices. However, there still lacks an evaluation criterion to estimate real research status and compare overall performance of the developed SSLMBs. Herein, we propose a comprehensive descriptor, Li+ transport throughput ( φ L i + ${{\phi{} }_{{{\rm L}{\rm i}}^{+}}}$ ), to estimate actual conditions and output performance of the SSLMBs. The φ L i + ${{\phi{} }_{{{\rm L}{\rm i}}^{+}}}$ is defined as molar number of Li+ passing through unit area of electrode/electrolyte interface in an hour (mol m-2 h-1 ) during cycling of battery, which is a quantizable value after taking complex aspects including cycle rate, electrode areal capacity and polarization into account. On this basis, we evaluate the φ L i + ${{\phi{} }_{{{\rm L}{\rm i}}^{+}}}$ of liquid, quasi-solid-state and solid-state batteries, and highlight three key aspects to achieve high value of φ L i + ${{\phi{} }_{{{\rm L}{\rm i}}^{+}}}$ via building highly efficient cross-phase, cross-gap and cross-interface ion transport in the solid-state battery systems. We believe that the new concept of φ L i + ${{\phi{} }_{{{\rm L}{\rm i}}^{+}}}$ provides milestone guidelines towards large-scale commercialization of SSLMBs.

Ultrathin and Robust Composite Electrolyte for Stable Solid-State Lithium Metal Batteries.

Solid-state polymer electrolytes (SPEs) are considered as one of the most promising candidates for the next-generation lithium metal batteries (LMBs). However, the large thickness and severe interfacial side reactions with electrodes seriously restrict the application of SPEs. Herein, we developed an ultrathin and robust poly(vinylidene fluoride) (PVDF)-based composite polymer electrolyte (PPSE) by introducing polyethylene (PE) separators and SiO2 nanoparticles with rich silicon hydroxyl (Si-OH) groups (nano-SiO2). The thickness of the PPSE is only 20 µm but possesses a quite high mechanical strength of 64 MPa. The introduction of nano-SiO2 fillers can tightly anchor the essential N,N-dimethylformamide (DMF) to reinforce the ion-transport ability of PVDF and suppress the side reactions of DMF with Li metal, which can significantly enhance the electrochemical stability of the PPSE. Meanwhile, the Si-OH groups on the surface of nano-SiO2 as a Lewis acid promote the dissociation of the lithium bis(fluorosulfonyl)imide (LiFSI) and immobilize the FSI- anions, achieving a high lithium transference number (0.59) and an ideal ionic conductivity (4.81 × 10-4 S cm-1) for the PPSE. The assembled Li/PPSE/Li battery can stably cycle for a record of 11,000 h, and the LiNi0.8Co0.1Mn0.1O2/PPSE/Li battery presents an initial specific capacity of 173.3 mA h g-1 at 0.5 C, which can stably cycle 300 times. This work provides a new strategy for designing composite solid-state electrolytes with high mechanical strength and ionic conductivity by modulating their framework.

Effects of repetitive transcranial magnetic stimulation on post-stroke patients with cognitive impairment: A systematic review and meta-analysis.

BACKGROUND: Post-stroke cognitive impairment (PSCI) is one of the common symptoms in stroke survivors, by which their quality of life and rehabilitation progress are severely limited. Repetitive transcranial magnetic stimulation (rTMS) has been proven to regulate cognition in a non-invasive way. However, the inconsistency in its effectiveness on PSCI reported in previous studies cannot be ruled out. A critical and comprehensive systematic review of rTMS on PSCI patients is necessary. METHODS: Trials published before the end of February 2022 on rTMS and PSCI were systematically retrieved from PubMed, Cochrane Library, EBSCO, Embase and SCOPUS. High-quality literature was selected following the inclusion and exclusion criteria, with their references being screened. Meta-analysis of data was carried out using RevMan 5.4 software. RESULTS: Ten trials involving 347 participants were included in the current review. Global cognition as measured by MMSE or MoCA (SMD=0.54; 95% CI=0.31, 0.76; P < 0.00001; I2 = 38%) and modified Barthel index (MD=9.00; 95% CI=2.93, 15.06; P = 0.004; I2 = 0%) were significantly improved by rTMS compared to sham stimulation in PSCI patients. Performance of the digit symbol test, rivermead behavioral memory test and attention in PSCI patients were also significantly improved. Subgroup analyses showed that significant differences were found in both MoCA and MMSE among PSCI patients by rTMS. MoCA was significantly improved by high frequency rTMS, while both MoCA and MMSE were significantly improved targeting on left dorsolateral prefrontal cortex. CONCLUSION: rTMS provides a non-invasive and effective technique for the treatment of post-stroke patients with cognitive impairment.