High-performance Solid-state Lithium Batteries Research Articles

Nuclear magnetic resonance studies of organic-inorganic composite solid electrolytes

Solid electrolytes have received widespread attention due to their higher safety than liquid electrolytes in the past decades. In particular, organic-inorganic composite solid electrolytes (CSEs) in which inorganic fillers dispersed in polymer solid electrolytes are considered to be one of the most promising candidate electrolytes for high-performance solid-state lithium batteries. Understanding the local environments and the conduction pathway/dynamics of Li+ is essential for the design of high-performance CSEs. Nuclear magnetic resonance (NMR) is a non-invasive quantitative technique that has unique capabilities in providing molecular structure information, morphological evolution, and measuring the movement of ions at different time scales. Therefore, for battery researchers, an accurate and comprehensive understanding of the basic principles and experimental design of solid-state NMR (SSNMR) is of great significance for investigating the abundant molecular structure and dynamics information in CSEs. The specific applications of the SSNMR technique in CSEs are briefly introduced in this present review.

A Sandwich Structure Composite Solid Electrolyte with Enhanced Interface Stability and Electrochemical Properties For Solid-state Lithium Batteries

Poor interfacial combination between the solid electrolyte and the lithium anode is a bottleneck for the application of solid-state lithium batteries. Here, a flexible polymer buffer layer of poly (propylene carbonate) (PPC)- Li7La3Zr2O12(LLZO) was introduced to the surface of polyvinylidene fluoride (PVDF)-LLZO solid electrolyte to form a sandwich composite structure, boosting the interfacial contact and stability between electrodes and electrolyte by in situ gelation of the PPC buffer layer. The layered structure composite solid electrolyte (LSCE) membrane has an electrochemical stability window of 4.55 V, and the ion conductivity is 1.25 × 10−4 S·cm−1. Due to the formation of a good interface contact and good stability against lithium and inhibition of lithium dendrite, the assembled NCM622/LSCE/Li solid-state battery has an initial specific capacity of 152.7 mAh·g−1 at a current density of 0.5 C, and the discharge specific capacity remains 106.9 mAh·g−1 after 200 cycles. At 1 C, the initial discharge specific capacity of the battery reaches 149.8 mAh·g−1, and remains 98 mAh·g−1 after 200 cycles. This layered structure composite electrolyte membrane shows good potential for use in high-performance solid-state lithium batteries.

Core-Shell MOF-in-MOF Nanopore Bifunctional Host of Electrolyte for High-Performance Solid-State Lithium Batteries.

Solid-state lithium-ion batteries with high safety are the encouraging next-generation rechargeable electrochemical energy storage devices. Yet, low Li+ conductivity of solid electrolyte and instability of solid-solid interface are the key issues hampering the practicability of the solid electrolyte. In this research, core-shell MOF-in-MOF nanopores UIO-66@67 are proposed as a unique bifunctional host of ionic liquid (IL) to fabricate core-shell ionic liquid-solid electrolyte (CSIL). In the current design of CSIL, the shell structure (UIO-67) has a large pore size and a high specific surface area, boosting the absorption amount of ionic liquid electrolyte, thus increasing the ionic conductivity. Nevertheless, the core structure (UIO-66) has a small pore size compared to the ionic liquid, which can confine the large ions, decreasing their mobility, and selectively boost the transport of Li+ . The CSIL solid electrolyte exhibits considerable enhancement in the lithium transference number (tLi + ) and ionic conductivity compared to the homogenous porous host (pure UIO-66 and UIO-67). Additionally, the Li|CSIL|Li symmetric batteries maintain a stable polarization of less than 28mV for more than 1000 h at 1000 µA cm-2 . Overall, the results demonstrate the concept of core-shell MOF-in-MOF nanopores as a promising bifunctional host of electrolytes for solid-state or quasi-solid-state rechargeable batteries.

Structural evolution of plasma sprayed amorphous Li4Ti5O12 electrode and ceramic/polymer composite electrolyte during electrochemical cycle of quasi-solid-state lithium battery

A quasi-solid-state lithium battery is assembled by plasma sprayed amorphous Li4Ti5O12 (LTO) electrode and ceramic/polymer composite electrolyte with a little liquid electrolyte (10 µL/cm2) to provide the outstanding electrochemical stability and better normal interface contact. Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscopy (STEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectrometer (EDS) were used to analyze the structural evolution and performance of plasma sprayed amorphous LTO electrode and ceramic/polymer composite electrolyte before and after electrochemical experiments. By comparing the electrochemical performance of the amorphous LTO electrode and the traditional LTO electrode, the electrochemical behavior of different electrodes is studied. The results show that plasma spraying can prepare an amorphous LTO electrode coating of about 8 µm. After 200 electrochemical cycles, the structure of the electrode evolved, and the inside of the electrode fractured and cracks expanded, because of recrystallization at the interface between the rich fluorine compounds and the amorphous LTO electrode. Similarly, the ceramic/polymer composite electrolyte has undergone structural evolution after 200 test cycles. The electrochemical cycle results show that the cycle stability, capacity retention rate, coulomb efficiency, and internal impedance of amorphous LTO electrode are better than traditional LTO electrode. This innovative and facile quasi-solid-state strategy is aimed to promote the intrinsic safety and stability of working lithium battery, shedding light on the development of next-generation high-performance solid-state lithium batteries.

An ultra-thin polymer electrolyte based on single-helical-structured agarose for high performance solid-state lithium batteries

An ultra-thin polymer electrolyte is prepared from single helical agarose grafted with PEO to balance ionic conductivity and mechanical properties.

Stable and Flexible Sulfide Composite Electrolyte for High-Performance Solid-State Lithium Batteries.

Sulfide-based lithium (Li)-ion conductors represent one of the most popular solid electrolytes (SEs) for solid-state Li metal batteries (SSLMBs) with high safety. However, the commercial application of sulfide SEs is significantly limited by their chemical instability in air and electrochemical instability with electrode materials (metallic Li anode and oxide cathodes). To address these difficulties, here, we design and successfully demonstrate a novel sulfide-incorporated composite electrolyte (SCE) through the combination of inorganic sulfide Li argyrodite (Li7PS6) with poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer. In this composite structure, Li7PS6 is embedded in PVDF-HFP polymer matrix, making the SCE flexible and air-stable and achieve great chemical and electrochemical stability. Meanwhile, the presence of sulfide facilitates Li-ion transport in SCE, leading to a superior room-temperature ionic conductivity of 1.1 × 10-4 S cm-1. Using the SCE with enhanced stability while maintaining high conductivity, Li||Li symmetric cells achieved stable cycling up to 1000 h at 0.2 mA cm-2. In addition, LiFePO4 (LFP)||SCE||Li cells can deliver an impressive specific capacity of 160 mAh g-1 over 150 cycles. These features indicate that Li7PS6/PVDF-HFP SCE is a promising candidate to contribute to the practical development of SSLMBs.

Incorporating multifunctional LiAlSiO4 into polyethylene oxide for high-performance solid-state lithium batteries

High ionic conductivity, good electrochemical stability, and satisfactory mechanical property are the crucial factors for polymer solid state electrolytes. Herein, fast ion conductor LiAlSiO4 (LASO) is incorporated into polyethylene oxide (PEO)-based solid-state electrolytes (SSEs). The SSEs containing LASO exhibit enhanced mechanical properties performance compared to pristine PEO-LiTFSI electrolyte. A reduced melting transition temperature of 40.57 °C is enabled by introducing LASO in to PEO-based SSE, which is beneficial to the motion of PEO chain and makes it possible for working at a moderate environment. Coupling with the enhanced motion of PEO, dissociation of the lithium salt, and conducting channel of LASO, the optimized composite polymer SSE exhibits a high ionic conductivity of 4.68 × 10−4, 3.16 × 10−4 and 1.62 × 10−4 S cm−1 at 60, 50 and 40 °C, respectively. The corresponding LiFePO4//Li solid-state battery exhibits high specific capacities of 166, 160 and 139 mAh g−1 at 0.2 C under 60, 40 and 25 °C. In addition, it remains 130 mAh g−1 at 4.0 C, and maintains 91.74% after 500 cycles at 1.0 C under 60 °C. This study provides a simple approach for developing ionic conductor-filled polymer electrolytes in solid-state lithium battery application.

Zinc bis(2–ethylhexanoate), a homogeneous and bifunctional additive, to improve conductivity and lithium deposition for poly (ethylene oxide) based all-solid-state lithium metal battery

Poly (ethylene oxide) based solid polymer electrolytes are suitable candidates for constructing all-solid-state lithium metal batteries. However, the low ionic conductivities, poor mechanical strength and incompetence to suppress the penetration of Li dendrites hinder their practical application. Herein, we introduce Zinc bis(2-ethylhexanoate) (Zn (BEH)2) as a homogeneous and bifunctional additive into PEO network by a simple solution casting method to achieve improvements of ionic conductivity and uniformity of lithium deposition. It is shown that the Lewis acid–base interactions between Zn (BEH)2 and PEO chains suppress the polymer crystallization and weaken the O–Li+ interaction, resulting in a good ionic conductivity of 1.1 × 10−5 S cm−1 at 30 °C, 2.7 × 10−4 S cm−1 at 60 °C and an improved lithium ion transfer number of 0.5 at 60 °C. Furthermore, a LiZn alloy layer is formed in-situ on lithium metal anode via the reaction between Zn (BEH)2 and Li, which effectively prevents dendrite growth. Based on PEO–Zn (BEH)2 polymer electrolyte, a Li/Li symmetric cell exhibits a steady cycling over 500 h with a low polarization potential of 150 mV. This strategy will illuminate new design strategy to advance polymer electrolytes towards high performance solid-state lithium batteries.

Cathode-doped sulfide electrolyte strategy for boosting all-solid-state lithium batteries

• FeS 2 cathode was used as doping agent for Li 7 P 3 S 11 -type glass–ceramic electrolyte. • The highest lithium-ion conductivity of 2.22 mS cm −1 was achieved by suitable FeS 2 doping. • The crystallization degree in the designed electrolyte was evaluated by solid-state NMR. • The cathode-doped electrolyte strategy reduced cathode/electrolyte interfacial resistance. • The fabricated all-solid-state batteries presented higher initial capacity and better cycling stability. Low lithium ionic conductivity of the solid-state electrolyte and large interface resistance have hampered the application of all-solid-state lithium batteries. Although various methods have been proposed to address these challenge, a high-efficient method still needs for all-solid-state batteries. For the first time that Pyrite (FeS 2 ) cathode is used as doping agent for Li 7 P 3 S 11 -type glass–ceramic electrolyte that could simultaneously improve the ionic conductivity and decrease the interfacial resistance between FeS 2 cathode and electrolyte. A new series of Li 7 P 3 S 11 -type glass–ceramic electrolytes (x = 0, 0.5, 1, 2) are prepared by high energy ball milling method, and the 99.5(70Li 2 S–30P 2 S 5 )–0.5FeS 2 glass–ceramic electrolyte shows a high lithium ionic conductivity, up to 2.22 mS cm −1 at room temperature. Solid-state NMR studies found that the presence of FeS 2 doping could controllably adjust the crystallisation portions in glass–ceramic electrolyte, thus achieving the superior ionic conductivity. Moreover, the fabricated FeS 2 /99.5(70Li 2 S–30P 2 S 5 )–0.5FeS 2 /Li–Ln cell exhibited lower resistance. As a result, the novel all-solid-state lithium battery presented a higher initial capacity of 543 mAh g −1 at the current density of 0.03 mA cm −2 and also better cycling stability (462 mAh g −1 after 20 cycles) than the counterpart. The proposed cathode-doped electrolyte strategy not only figure out the key factors that determine the ionic conductivity of the glass–ceramic electrolyte and cathode/electrolyte interfacial resistance, and also provides an efficient route for design electrode configuration of high-performance solid-state lithium batteries.

An in-situ polymerized solid polymer electrolyte enables excellent interfacial compatibility in lithium batteries

Due to the ex-situ assembly technology of solid-state electrolyte, solid-state lithium batteries commonly show a poor electrolyte/electrode interfacial contact. Herein, we report an in-situ polymerized poly (tetrahydrofuran) (PTHF)-based solid polymer electrolyte (PTSPE) to resolve the poor interfacial contact problem in solid state lithium batteries. The in-situ formed PTSPE exhibits a high ionic conductivity (2.3 × 10−4 S cm−1) and a wide electrochemical window (4.5 V) at 60 °C. More importantly, the in-situ formed PTSPE improves interfacial compatibility remarkably, suppressing the growth of lithium dendrites. It is revealed that boron trifluoride initiator works as functional additive to form LiF and B-O species at interface layer of lithium metal anode, alleviating lithium dendrites growth and undesired parasitic reactions. An as-assembled LiFePO4/Li cell employing this in-situ formed PTSPE delivers a high discharge capacity of 142.3 mA h g−1 even after 100 cycles. The aforementioned results suggest that the in-situ polymerization technology of solid-state electrolyte is very promising for high-performance solid-state lithium batteries.

A durable and safe solid-state lithium battery with a hybrid electrolyte membrane

Polymer–ceramic composite electrolytes are emerging as a promising solution to achieving high ionic conductivity, optimal mechanical properties, and good safety for developing high-performance all-solid-state rechargeable batteries. In this work, we report a garnet (Li7La3Zr2O12)-based hybrid solid electrolyte (HSE) membrane designed for high performance solid-state lithium batteries for the first time. The composite HSE membrane is composed of LLZO particles and PVDF–HFP polymer matrix. The solid-state lithium battery with this HSE membrane, Li metal anode and LiFePO4 cathode exhibits an initial reversible discharge capacity of 120mAhg−1 at a charge/discharge current density of 0.5C at room temperature. This solid-state battery is used to store the energy harvested by a TENG at different rotation rates. The solid state battery can efficiently store the pulsed energy, especially for output at high frequencies.

Flexible and ion-conducting membrane electrolytes for solid-state lithium batteries: Dispersion of garnet nanoparticles in insulating polyethylene oxide

Solid-state electrolytes with high ionic conductivity, large electrochemical window, good mechanical properties, and easy processability are needed for high-energy solid-state lithium batteries. In this work, composite membranes consisting of lithium garnet (i.e. Li6.4La3Zr1.4Ta0.6O12, LLZTO) particles and Li-salt-free polyethylene oxides (PEOs) are produced as solid-state electrolytes. Li-ion-conducting particles in nano-scale are crucial for the enhancement of conductivity and the membranes containing ~40nm LLZTO particles exhibit conductivities nearly two orders of magnitude larger than those with the micro-scale ones, which is attributed to the difference in specific surface area related to the percolation effect. Compared to the conventional PEO doped with lithium salt, the insulating PEO in PEO:LLZTO membrane electrolyte is conducive to the suppression of lithium dendrite growth owing to prohibition of current flow. With PEO:LLZTO membrane electrolytes in conductivity of 2.1×10−4Scm−1 at 30°C and 5.6×10−4Scm−1 at 60°C, the solid-state LiFePO4/PEO:LLZTO/Li and LiFe0.15Mn0.85PO4/PEO:LLZTO/Li cells deliver energy densities of 345Whkg−1 (662WhL−1) and 405Whkg−1 (700WhL−1) (without the package weight or volume) with good rate capability and cycling performance. This study suggests that the conjunction of nano-scale Li-ion-conducting particles and an insulating polymer provides a promising solution to produce powerful solid-state electrolytes for high-performance solid-state lithium batteries.