Development Of Solid-state Lithium Batteries Research Articles

Solid-State Electrolytes by Electrospinning Techniques for Lithium Batteries.

Solid-state lithium batteries (SSLBs) are regarded as next-generation energy storage devices because of their advantages in terms of safety and energy density. However, the poor interfacial compatibility and low ionic conductivity seriously hinder their development. Electrospinning is considered as a promising method for fabricating solid-state electrolytes (SSEs) with controllable nanofiber structures, scalability, and cost-effectiveness. Numerous efforts are dedicated to electrospinning SSEs with high ionic conductivity and strong interfacial compatibility, but a comprehensive summary is lacking. Here, the history of electrospinning SSEs is overeviewed and introduce the electrospinning mechanism, followed by the manipulation of electrospun nanofibers and their utilization in SSEs, as well as various methods to improve the ionic conductivity of SSEs. Finally, new perspectives aimed at enhancing the performance of SSEs membranes and facilitating their industrialization are proposed. This review aims to provide a comprehensive overview and future perspective on electrospinning technology in SSEs, with the goal of guiding the further development of SSLBs.

Electrochemical Performance and Microstructure Evolution of a Quasi-Solid-State Lithium Battery Prepared by Spark Plasma Sintering.

Solid-state lithium batteries are promising next-generation energy storage systems for electric vehicles due to their high energy density and high safety and require achieving and maintaining intimate solid-solid interfaces for lithium-ion and electron transport. However, the solid-solid interfaces may evolve over cycling, disrupting the ion and electron diffusion pathways and leading to rapid performance degradation. The development of solid-state lithium batteries has been hindered by the lack of fundamental understanding of the interfacial microstructure change over cycling and its relation to electrochemical properties. Herein, we prepared a quasi-solid-state lithium battery, 30%LiFePO4-55%Li1.5Al0.5Ge1.5(PO4)3-15%C| Li1.5Al0.5Ge1.5(PO4)3|Li, by spark plasma sintering, and employed it as a model system to reveal the microstructure evolution at the solid-solid interfaces with electrochemical performance of the batteries. The electrochemical assessment showed that the quasi-solid-state lithium battery exhibited a discharge specific capacity of about 150 mAh g-1 in the first 80 cycles and then experienced severe capacity attenuation afterward, accompanied by a gradual internal resistance increase. Scanning electron microscopy observation showed that more cracks were formed inside the solid-state electrolyte and at the solid-solid interfaces as the battery cycled from 10 to 67 and 157 cycles. Detailed microstructure and phase analysis by high-resolution transmission electron microscopy and selected area electron diffraction discovered that the crack formation and performance decay were mainly caused by (1) the volume change of the LiFePO4 composite cathode during cycling, (2) the grain expansion of the Li1.5Al0.5Ge1.5(PO4)3 solid-state electrolyte at its interface with lithium anode, and (3) the formation of a solid electrolyte interphase layer, comprising Li2CO3, LiF, and LiTFSI, at the cathode-solid-state electrolyte interface. These microstructure changes built up over repeated battery cycling, ultimately causing the structure collapse and battery failure. The microstructure evolution information is expected to guide the design of better structures and interfaces for solid-state lithium batteries.

In-situ generated solid-state electrolytes with intimate interface affinity enable conductivity and high performances for lithium-ion batteries

The issues of interfacial compatibility derived from electrolyte/electrodes and unsatisfied ionic conductivity still hinder the practical application of lithium-ion batteries. In the present study, the crosslinked solid polymer electrolytes (SPEs) based on dual epoxy group were prepared through in-situ thermal polymerization method. FSO2NH2 was employed as additive for high reactivity to adapt the kinetic reaction and improve the conductivities of electrolytes. The as-prepared SPEs exhibit a high degree of amorphous structure, lower transmission glass temperature, considerable ionic conductivity (>1.0 mS cm−1) at 25 °C, wider electrochemical stability window, and excellent Li cation transference number. Moreover, the battery performance of the as-prepared PBDE−1 electrolyte-based half-cell means that it delivers a high initial specific capacity (ca. 161.2 mAh g−1), and achieves remarkable Coulombic efficiency of 99.8% after 200 cycles at 0.1 C. X-ray photoelectron spectra further revealed the formation of a solid electrolyte interphase (SEI) layer, which can alleviate Li dendrite growth and facilitate the lifespan stability of Li/graphite anode during cycling. These findings may provide a reference for the development of solid-state lithium batteries.

Interelectrode Talk in Solid-State Lithium-Metal Batteries.

Solid-state lithium-metal batteries have been identified as a strategic research direction for the electric vehicle industry because of their promising high energy density and potential characteristic safety. However, the intrinsic mechanical properties of solid materials cause inevitable electro-chemo-mechanical failure of electrodes and electrolytes during charging and discharging; these failure mechanisms include lithium penetration and formation of cracks and voids, which pose a serious challenge for the long cycle life of solid-state lithium-metal batteries. Here, a short overview of the recent advances with a view to understand this challenge is provided. Furthermore, new insights into the cross-talk behavior between the cathode and lithium-metal anode are provided based on the non-uniform Li+ flux inducing interactional electro-chemo-mechanical failure. Furthermore, guidelines for designing stable solid-state lithium-metal batteries and research directions to figure out the interelectrode-talk-related electro-chemo-mechanical failure mechanism are presented, which can be significant for accelerating the development of solid-state lithium batteries.

In-Situ Plasticized LLZTO-PVDF Composite Electrolytes for High-Performance Solid-State Lithium Metal Batteries

Solid polymer electrolytes (SPEs) are seen as the key component in the development of solid-state lithium batteries (SSLBs) by virtue of their good processability and flexibility. However, poor mechanical strength, low room-temperature lithium-ion (Li-ion) conductivity and unsatisfactory interfacial compatibility with electrodes limit their practical application. In this work, a composite electrolyte consisting of polyvinylidene fluoride and polyvinylidene carbonate with a Li6.4La3Zr1.4Ta0.6O12(LLZTO) active filler (PFPC: LLZTO-SPE) is reported to achieve excellent ionic conductivity (4.25 × 10−4 S cm−1 at 30 °C), a wide electrochemical window (>4.6 V), a high Li-ion transference number (tLi+ = 0.49) and good interfacial compatibility with the electrode. Incorporating LLZTO as an active filler not only increases the ionic conductivity of the electrolyte, but also homogenizes Li-ion flux and stabilizes the electrode/electrolyte interface, thereby preventing lithium dendrites from piercing the electrolyte. As a result, Li/Li symmetrical cells using PFPC: LLZTO-SPEs deliver more than 800 h of cyclability at 0.1 mA cm−2 and a high critical current density (CCD) of 2.6 mA cm−2. The assembled Li/PFPC: LLZTO/LFP SSLBs achieve 87% capacity retention after 150 cycles at 0.2 C and 89% capacity retention for 100 cycles at 0.5 C. This work inspires new insights into designing high-performance SPEs.

In situ induced crosslinking highly conductive solid polymer electrolyte with intimated electrodes interfacial compatibility for safe Li-ion batteries

Nowadays, lower ionic conductivity and interfacial issue are hindering industrial development of solid-state lithium batteries. Herein, we prepare cross-linking solid polymer electrolytes (CSPEs) with a certain amount of additive fluorosulfonamide (FSA) by employing lithium bis(fluorosulfonyl)imide (LiFSI) as an initiator for catalyzing cationic ring-opening polymerization (CROP) via an in-situ thermal strategy. a series of technologies have used to investigate the physiochemical properties and electrochemical performances of as-prepared CSPEs. The ionic conductivity of as-prepared CSPE-2 is 1.46 mS/cm at 25 °C. Its electrochemical anodic oxidation potential is stable up to 5.2 V. Its lithium transference number (tLi+) reaches to 0.61 at room temperature (RT). Furthermore, the assembled half-cell of LiFePO4/CSPE-2/Li delivers an excellent initial discharge capacity of 165 mAh/g at 0.1C and shows Coulombic efficiency (CE) of 96.7%. It retains its capacity at 136 mAh/g after 200 cycles. Full cell configuration of LiFePO4/CSPE-2/graphite shows an initial discharge capacity of 142 mAh/g at 0.1C, retains its capacity at 122 mAh/g, and achieves a CE of 90.2% after 200 cycles. Field emission scanning electron microscope (FE-SEM) reveals an intimate interface compatibility with additive FSA. This study may provide a strategy to design and fabricate solid-state electrolytes for lithium-ion batteries.

Effect of argon sputtering pressure on the electrochemical performance of LiFePO4 cathode

The development of a novel small-scale electrical power source technology is essential in the design of microelectronic devices. In this sense, this study presents the optimization of the sputtering deposition parameters to grow a LiFePO4 cathode, a candidate material for the development of solid-state lithium batteries. Specifically, it was evaluated the effect of argon deposition pressure on the electrochemical properties of LiFePO4 cathode. By combining X-ray photoelectron spectroscopy with electrochemical characterization methods, it was revealed that argon deposition pressure modulated the degree of the re-sputtering effects. In addition, it was found that high argon deposition pressure leads to the growth of LiFePO4 films with oxygen and phosphor deficiency. The absence of these atoms caused the decrease in the LiFePO4 electrochemical activity. Conversely, deposition parameters based on low argon sputtering pressure significantly reduced the degree of the re-sputtering effects, which in turn favored the growth of stoichiometric LiFePO4 films with an enhanced electrochemical activity.

Recent progress of solid-state lithium batteries in China

Different from traditional lithium-ion battery, the solid-state lithium batteries (SSLBs) using solid electrolytes (SEs) have attracted much attention for their potential of high safety, high energy density, good rate performance, and wide operating temperature range in recent years. In China, the SSLB-relevant fundamental research and industrialization exploration are progressing rapidly. In this perspective, we present a timely overview of the recent research and development of SSLBs in China in the past 1 year, covering the latest achievements of SSLBs which used sulfide SEs, oxide SEs, solid polymer electrolytes, and halide SEs, respectively. Moreover, the government policies and the latest company industrialization process relative to SSLBs are comprehensively summarized.

Cathode structural design enabling interconnected ionic/electronic transport channels for high-performance solid-state lithium batteries

Great achievements have been accomplished for high performance solid-state electrolytes, however, the poor electrode/electrolyte interfacial contact severely impedes the development of solid-state lithium batteries (SSLBs). Herein, we design a 3D structural composite cathode based on cross-linked electrospun LiNi0.5Co0.2Mn0.3O2 (ES-NCM) network and ductile Li+ conductive polymer electrolyte. Improved electrochemical kinetics and intimate interface are realized through infiltrating polymer precursor into ES-NCM network followed by in-situ polymerization. Assembled with Li1.3Al0.3Ti1.7(PO4)3-polyvinylidene fluoride (LATP-PVDF) solid electrolyte, the composite ES-NCM||LATP-PVDF||Li battery exhibits satisfactory electrochemical performance (with an initial discharge capacity of 143.2 mAh g−1 at 0.1C and a capacity retention of 74.0% after 80 cycles) since continuous Li+/e− conduction channels are generated by ES-NCM skeleton and Li+ conductive polymer. Besides, the high areal capacity of 1.19 mAh cm−2 at a high ES-NCM loading of 9.28 mg cm−2 further supports the feasibility of our composite cathode design in the application of high energy-density SSLBs. Additionally, the flexible solid-state pouch cell exhibits excellent electrochemical performance (with a discharge capacity of 131.6 mAh g−1) and reliable safety characteristics under mechanical abuse. This work is anticipated to provide a new perspective in overcoming solid-solid contact issues in SSLBs.

Macromolecular Design of Lithium Conductive Polymer as Electrolyte for Solid-State Lithium Batteries.

In the development of solid-state lithium batteries, solid polymer electrolyte (SPE) has drawn extensive concerns for its thermal and chemical stability, low density, and good processability. Especially SPE efficiently suppresses the formation of lithium dendrite and promotes battery safety. However, most of SPE is derived from the matrix with simple functional group, which suffers from low ionic conductivity, reduced mechanical properties after conductivity modification, bad electrochemical stability, and low lithium-ion transference number. Appling macromolecular design with multiple functional groups to polymer matrix is accepted as a strategy to solve the problems of SPE fundamentally. In this review, macromolecular design based on lithium conducting groups is summarized including copolymerization, network construction, and grafting. Meanwhile, the construction of single-ion conductor polymer is also focused herein. Moreover, synergistic effects between the designed matrix, lithium salt, and fillers are reviewed with the objective to further improve the performance of SPE. At last, future studies on macromolecular design are proposed in the development of SPE for solid-state batteries with high energy density and durability.

Rational Design of Ion Transport Paths at the Interface of Metal-Organic Framework Modified Solid Electrolyte.

Solid-state lithium batteries have attracted great attention owing to their potential advantages in safety and energy density. Among various solid electrolytes, solid polymer electrolyte is promising due to its good viscoelasticity, lightweight, and low-cost processing. However, key issues of solid polymer electrolyte include poor ionic conductivity and low Li+ transference number, which limit its practical application. Herein, a new-type of ultraviolet cross-linked composite solid electrolyte (C-CSE), composed of ZIF-based ionic conductor (named ZIL) and polymer, is designed with enhanced ion transport. The ZIL is composed of ZIF-8 and ionic liquid, which can provide C-CSE with fast ion transport paths. Moreover, the proper pore size of ZIF-8 can restrict the migration of embedded ionic liquid and thus construct a solid-liquid transport interface between polymer chains and ZIF-8, which could achieve fast ion transport. In addition, ultraviolet irradiation can decrease the crystallization of C-CSE and thus increase the amorphous region. Consequently, the C-CSE show excellent electrochemical performance including high ionic conductivity of 0.426 mS cm-1 at 30 °C, high Li+ transference number of 0.67, and good Li|Li compatibility cycle over 1040 h. Experimental and computational results indicate that diffusion energy barrier of Li+ through ZIF-8 is smaller than that of polymer chains, which reveals a new Li+ transport mechanism between polymer chains and ZIL, from "chain-chain-chain" to "chain-ZIL-chain". This work demonstrates rational design of ion transport paths at the interface of solid electrolyte could facilitate the development of solid-state lithium batteries as a promising novel strategy.

The devil is in the electrons

The development of solid-state lithium batteries is largely hindered by the undesired lithium dendrite propagation during battery operations. High electronic conductivity of solid electrolytes is now revealed to be the main culprit.

Bottom-current-collector-free thin-film batteries using LiNi0.8Co0.2O2 epitaxial thin films

The decrease in the resistance at solid electrolyte and electrode interfaces has become a critical issue in the development of solid-state lithium batteries. To understand the ionic transport properties across solid electrolyte and electrode interfaces, thin-film batteries consisting of flat epitaxial films are of considerable importance. Herein, we report the operation of bottom-current-collector-free thin-film batteries using LiNi0.8Co0.2O2 epitaxial thin films. As the bottom current collector is not inserted between the substrates and LiNi0.8Co0.2O2, the surface of LiNi0.8Co0.2O2 is very flat, with a surface roughness average of approximately 0.44 nm. This study proposes a very flat electrode surface suitable for the investigation of interfacial phenomena at solid electrolyte and electrode interfaces.

Integrated Interface Strategy toward Room Temperature Solid-State Lithium Batteries.

Solid-state lithium batteries have drawn wide attention to address the safety issues of power batteries. However, the development of solid-state lithium batteries is substantially limited by the poor electrochemical performances originating from the rigid interface between solid electrodes and solid-state electrolytes. In this work, a composite of poly(vinyl carbonate) and Li10SnP2S12 solid-state electrolyte is fabricated successfully via in situ polymerization to improve the rigid interface issues. The composite electrolyte presents a considerable room temperature conductivity of 0.2 mS cm-1, an electrochemical window exceeding 4.5 V, and a Li+ transport number of 0.6. It is demonstrated that solid-state lithium metal battery of LiFe0.2Mn0.8PO4 (LFMP)/composite electrolyte/Li can deliver a high capacity of 130 mA h g-1 with considerable capacity retention of 88% and Coulombic efficiency of exceeding 99% after 140 cycles at the rate of 0.5 C at room temperature. The superior electrochemical performance can be ascribed to the good compatibility of the composite electrolyte with Li metal and the integrated compatible interface between solid electrodes and the composite electrolyte engineered by in situ polymerization, which leads to a significant interfacial impedance decrease from 1292 to 213 Ω cm2 in solid-state Li-Li symmetrical cells. This work provides vital reference for improving the interface compatibility for room temperature solid-state lithium batteries.

Batteries: Getting solid

Materials with high ionic conductivity are urgently needed for the development of solid-state lithium batteries. Now, an inorganic solid electrolyte is shown to have an exceptionally high ionic conductivity of 25 mS cm−1, which allows a solid-state battery to deliver 70% of its maximum capacity in just one minute at room temperature.

Recent Progress in Interfacial Nanoarchitectonics in Solid-State Batteries

Employing solid electrolytes in lithium-ion batteries is anticipated to be a solution to some issues originated from their organic electrolytes. However, solid-state lithium batteries had not been practicable, because ionic conductivities of lithium-ion conductive solid electrolytes had been very low. Therefore, many studies aiming at the development of solid-state lithium batteries have been focused on enhancement of ionic transport in solids. They have succeeded in enhancing the conductivity to be comparable to or even higher than that of liquids. At this stage, rate-determining step of the battery reactions is sometimes ionic transport at interface rather than bulk in the battery components. Since anomalous ionic conduction at the interface takes place in space-charge layers with ca. 10 nm in thickness, it will be controlled by “nanoarchitectonics”. This paper reviews some interfacial nanoarchitectures that control the interfacial ionic conduction to enhance the performance of solid-state lithium batteries.