High-performance Solid-state Lithium Batteries Research Articles

Co-doping strategies for advanced solid state electrolytes with lithium salt: a study on the structural and electrochemical properties of LATP

The commercialization of lithium-ion batteries has revolutionized the field of energy storage, yet their usage of organic electrolytes has led to significant safety concerns. Solid-state electrolytes have emerged as a promising solution to these issues, enabling the development of high-performance solid-state lithium batteries. The NASICON-type solid electrolyte Li1.3Al0.3Ti1.7P3O12 (LATP) has demonstrated excellent properties and significant potential. This study involves the solid-state synthesis of LATP electrolytes doped with Cobalt and Silicon. Furthermore, adding 8% LiBr into LATP-0.04 significantly enhanced ionic conductivity, reaching a value of 3.50 × 10−4 S cm−1. This can be linked to lithium salt filling vacant spaces between grains, resulting in a significant drop in grain boundary resistances. The electrochemical analysis through Linear Sweep Voltammetry (LSV) indicates that the investigated material demonstrates the capability to sustain stability and functionality even under the influence of elevated voltages, notably up to 5.45 V. These findings imply that optimal cobalt doping and Lithium salt contribute to superior ionic conductivity compared to pristine LATP.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries.

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

Flexible High Lithium-Ion Conducting PEO-Based Solid Polymer Electrolyte with Liquid Plasticizers for High Performance Solid-State Lithium Batteries.

Lithium-ion secondary batteries (LIB) with high energy density have attracted much attention for electric vehicle (EV) applications. However, LIBs have a safety problem because these batteries contain a flammable organic electrolyte. As such, all-solid secondary batteries that are not flammable have been extensively reported recently. In this study, we have focused on polymer electrolytes, which is flexible and is expected to address the safety problem. However, the conventional polymer electrolytes have low electrial conductivity at room temperature. Various attempts have been made to solve this problem, such as the addition of inorganic fillers and ionic liquids; however, these composite polymer electrolytes have not yet reached a practical level of lithium-ion conductivity. In this study, high electrical conductivity and lithium dendrite formation-free PEO based composite electrolytes are developed with both a filler of Li6,4La3Zr1.4Ta0.6O12 and liquid plasticizers of tetraethylene glycol dimethyl ether and 1,2 dimethoxyethane. The proposed flexible polymer electrolyte shows a high electrical conduciviy of 6.01×10-4 S cm-1 at 25 °C.

Regulating interfaces of composite polymer electrolyte via surface charge on fillers for stable solid-state lithium battery

The commercial potential of composite polymer electrolytes (CPEs) is significant due to their ability to combine the advantages of both inorganic and polymer solid electrolytes. However, the unstable interface and insufficient ionic conductivity remain important challenges in practical applications of CPEs for achieving high-performance solid-state lithium batteries (SLBs). Herein, we construct a double-layer composite polymer electrolyte (D-CPE) by incorporating nanosized TiO2 fillers with adjustable concentrations of oxygen vacancies into poly (ethylene oxide) (PEO)-based electrolyte composites. In the D-CPE structure, one CPE layer containing TiO2 fillers with oxygen vacancies exclusively interfaces with the LiFePO4 cathode, while the other CPE layer consisting of pristine TiO2 fillers (with negatively charged surfaces) solely contacts the lithium anode. This design of D-CPE achieves high ionic conductivity, a broad electrochemical window, and interfacial stability without additional resistance at the electrolyte-electrolyte interface simultaneously. The LiFePO4/D-CPEs/Li battery exhibits excellent cycling stability at 0.1 C, maintaining a capacity of 157.2 mAh g−1 with a capacity retention rate of 99.1% after 100 cycles. Furthermore, even at 0 °C, it delivers an impressive discharge capacity of 133.1 mAh g−1 at 0.1 C. This work presents a simple and effective approach to achieving superior polymer-based electrolytes for high-performance solid-state lithium batteries.

Interfacial self-healing polymer electrolytes for Long-Cycle silicon anodes in High-Performance solid-state lithium batteries

For all-solid-state lithium-ion batteries (ASSLIBs), silicon (Si) stands out as an appealing anodes material due to its high energy density and improved safety compared to lithium metal. However, the substantial volume changes during cycling result in poor solid-state physical contact and electrolyte–electrode interface issues, leading to unsatisfactory electrochemical performance. In this study, we employed in-situ polymerization to construct an integrated Si anodes/self-healing polymer electrolyte for ASSLIBs. The polymer chain reorganization stems from numerous dynamic bonds in the constructed self-healing dynamic supermolecular elastomer electrolyte (SHDSE) molecular structure. Notably, SHDSE also serves as a Si anodes binder with enhanced adhesive capability. As a result, the well-structured Li|SHDSE|Si-SHDSE cell generates subtle electrolyte–electrode interface contacts at the molecular level, which can offer a continuous and stable Li+ transport pathway, reduce Si particle displacement, and mitigate electrode volume expansion. This further enhances cyclic stability (>500 cycles with 68.1 % capacity retention and >99.8 % Coulombic efficiency). More practically, the 2.0 Ah wave-shaped Si||LiCoO2 soft-pack battery with in-situ cured SHDSE exhibits strongly stabilized electrochemical performance (1.68 Ah after 700 cycles, 86.2 % capacity retention) in spite of a high operating temperatures up to 100 °C and in various bending tests. This represents a groundbreaking report in flexible solid-state soft-pack batteries containing Si anodes.

Solid Interfaces for the Garnet Electrolytes.

Solid-state electrolytes (SSEs) have attracted extensive interests due to the advantages in developing secondary batteries with high energy density and outstanding safety. Possessing high ionic conductivity and the lowest reduction potential among the state-of-the-art SSEs, the garnet type SSE is one of the most promising candidates to achieve high performance solid-state lithium batteries (SSLBs). However, the elastic modulus of the garnet electrolyte leads to deteriorated interfacial contacts, and the increasing in electronic conduction at either anode/garnet interface or grain boundary results in Li dendrite growth. Here, recent developments of the solid interfaces for the garnet electrolytes, including the strategies of Li dendrite suppression and interfacial chemical/electrochemical/mechanical stabilizations are presented. A new viewpoint of the double edges of interfacial lithiophobicity is proposed, and the rational design of the interphases, as well as effective stacking methods of the garnet-based SSLBs are summarized. Moreover, practical roles of the garnet electrolyte in SSLB industry are also discussed. This work delivers insights into the solid interfaces for the garnet electrolytes, which provides not only the promotion of the garnet-based SSLBs, but also a comprehensive understanding of the interfacial stabilization for the whole SSE family.

Fusing Ta-doped Li7La3Zr2O12 grains using nanoscale Y2O3 sintering aids for high-performance solid-state lithium batteries.

Solid-state lithium batteries have advantages of high energy density and usage safety and are considered as promising next-generation power sources. Among them, the garnet-type oxide electrolyte has become a widely studied inorganic electrolyte due to its high ionic conductivity and chemical stability. In this paper, nanoscale Y2O3 (NYO) particles are introduced as sintering aids for fabricating Ta-doped Li7La3Zr2O12 (LLZTO) ceramics, and the sintering effects of various NYO ratios on the properties of LLZTO are investigated. Among the samples, the LLZTO-5%NYO sample exhibits the highest ionic conductivity (7.39 × 10-4 S cm-1) and the lowest activation energy (0.17 eV). At various current densities, the polarization voltage of LLZTO-5%NYO is also the lowest without a short circuit. The full cells of LFP|LLZTO-5%NYO|Li exhibit a high capacity of 163.9 mA h g-1 with a high initial coulombic efficiency of 97.4%, and the capacity retention rate is up to 98.1% after 50 cycles. This work may inspire the development of analogous solid-state electrolytes and lithium batteries.

Fluorinated Graphene Fillers for High-Performance Solid-State Lithium Batteries

Solid-state batteries (SSBs) are expected to revolutionize the field of energy storage due to their superior safety and high energy density, which result from the use of lithium metal as the negative electrode. However, the development of solid-state electrolytes (SSEs), the key component of SSBs, is quite crucial. SSEs have high thermal stability, high mechanical strength, and a wide electrochemical window but lack enough ionic conductivity; which is one of the most challenging aspects. Incorporating suitable active or inert fillers in the solid polymer electrolyte matrix is one of several methods adopted to improve the ionic conductivity of pure polymer SSEs. Two-dimensional graphene-based fillers are a promising option as they provide a high surface area for creating an abundant interface with the polymer matrix creating a continuous pathway for lithium-ion transport and simultaneously their robust nature improves the mechanical strength of the electrolyte. Pristine graphene is electronically conducting in nature owing to the continuous sp2 carbon linkages, but the electronic conductivity can be suppressed by disrupting the sp2 bonds by heteroatom functionalization on the graphene. This study investigates the heteroatom functionalization of graphene to obtain various graphene-based fillers such as graphene oxide (GO), reduced graphene oxide (rGO), and fluorinated graphene oxide (FGO) and their effectiveness when introduced into a polymer SSE matrix for LiNi0.8Co0.1Mn0.1O2-based SSBs. FGO filler outperforms others in terms of ionic conductivity, thermal stability, enhanced electrochemical potential window, and compatibility of the SSE. The optimized ratio of FGO fillers in SSE demonstrates excellent electrochemical performance, enabling long-term Li plating/stripping with small overpotential and stable cycling of Li/ LiNi0.8Co0.1Mn0.1O2 full cells. This work highlights the notable potential of FGO materials in improving the comprehensive properties of polymer SSEs and promoting the applications of polymer SSEs in high-performance SSBs.

Design principles for sodium superionic conductors

Motivated by the high-performance solid-state lithium batteries enabled by lithium superionic conductors, sodium superionic conductor materials have great potential to empower sodium batteries with high energy, low cost, and sustainability. A critical challenge lies in designing and discovering sodium superionic conductors with high ionic conductivities to enable the development of solid-state sodium batteries. Here, by studying the structures and diffusion mechanisms of Li-ion versus Na-ion conducting solids, we reveal the structural feature of face-sharing high-coordination sites for fast sodium-ion conductors. By applying this feature as a design principle, we discover a number of Na-ion conductors in oxides, sulfides, and halides. Notably, we discover a chloride-based family of Na-ion conductors NaxMyCl6 (M = La–Sm) with UCl3-type structure and experimentally validate with the highest reported ionic conductivity. Our findings not only pave the way for the future development of sodium-ion conductors for sodium batteries, but also consolidate design principles of fast ion-conducting materials for a variety of energy applications.

Defect Strategy in Solid-State Lithium Batteries.

Solid-state lithium batteries (SSLBs) have great development prospects in high-security new energy fields, but face major challenges such as poor charge transfer kinetics, high interface impedance, and unsatisfactory cycle stability. Defect engineering is an effective method to regulate the composition and structure of electrodes and electrolytes, which plays a crucial role in dominating physical and electrochemical performance. It is necessary to summarize the recent advances regarding defect engineering in SSLBs and analyze the mechanism, thus inspiring future work. This review systematically summarizes the role of defects in providing storage sites/active sites, promoting ion diffusion and charge transport of electrodes, and improving structural stability and ionic conductivity of solid-state electrolytes. The defects greatly affect the electronic structure, chemical bond strength and charge transport process of the electrodes and solid-state electrolytes to determine their electrochemical performance and stability. Then, this review presents common defect fabrication methods and the specific role mechanism of defects in electrodes and solid-state electrolytes. At last, challenges and perspectives of defect strategies in high-performance SSLBs are proposed to guide future research.

Recent Advances in Developing High-Performance Solid-State Lithium Batteries: Interface Engineering

Recent Advances in Developing High-Performance Solid-State Lithium Batteries: Interface Engineering

Flexible PVDF-HFP based hybrid composite solid electrolyte membrane co-filled with hydroxypropyl methyl cellulose and Li6.4La3Zr1.4Ta0.6O12 for high-performance solid-state lithium batteries

Solid polymer electrolytes (SPEs) have sparked attention due to their superior mechanical robustness and excellent security in solid-state lithium batteries. However, intrinsic limitations, such as poor ionic transport properties and large interface impedance, severely hinder their practical applications. Herein, a novel composite solid electrolyte (PLHL-CSE) membrane, which consists of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), hydroxypropyl methyl cellulose (HPMC), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and Li6.4La3Zr1.4Ta0.6O12 (LLZTO), was prepared by solution-casting technique. The incorporation of HPMC into PVDF-HFP-based electrolyte played crucial roles in reducing the crystallinity of PVDF-HFP, promoting the dissociation of lithium salt, and increasing the amount of mobile Li+. With synergistic effects of HPMC and LLZTO, the mechanical and electrochemical performance of PVDF-HFP-based electrolytes were greatly enhanced. The obtained PLHL-CSE membrane showed better mechanical strength (3.0 MPa), enhanced ionic conductivity (0.25 mS/cm at 25 °C), greater lithium-ion transference number (0.7), and broadened electrochemical window of 5.0 V (vs. Li+/Li) than the PVDF-HFP/LiTFSI solid polymer electrolyte (PL-SPE) membrane. After 300 cycles at 1 C, the assembled LiFePO4/PLHL-CSE/Li cell with PLHL-CSE membrane as the hybrid composite solid electrolyte displayed a high capacity retention (95.6%). In addition, the positive effects of HPMC and LLZTO on promoting the generation of stable SEI and the uniform lithium deposition were also confirmed by the SEM results of cycled lithium metals. These findings point to the good potential of PLHL-CSE membrane as a hybrid composite solid electrolyte for practical application in lithium batteries.

Green recycling of short-circuited garnet-type electrolyte for high-performance solid-state lithium batteries

Solid-state lithium batteries (SSLBs) solve safety issues and are potentially energy-dense alternatives to next-generation energy storage systems. Battery green recycling routes are responsible for the widespread use of SSLBs due to minimizing environmental contamination, reducing production costs, and providing a sustainable solution for resources, e.g., saving rare earth elements (La, Ta, etc.). Herein, a solid-state recycling strategy is proposed to achieve green recycling of the crucial component solid-state electrolytes (SSEs) in spent SSLBs. The short-circuited garnet Li6.5La3Zr1.5Ta0.5O12 (LLZTO) is broken into fine particles and mixed with fresh particles to improve sintering activity and achieve high packing density. The continuous Li absorption process promotes sufficient grain fusion and guarantees the transformation from tetragonal phase to pure cubic phase for high-performance recycled LLZTO. The Li-ion conductivity reaches 5.80 × 10-4 S cm−1 with a relative density of 95.9%. Symmetric Li cell with as-recycled LLZTO shows long-term cycling stability for 700 h at 0.3 mA cm−2 without any voltage hysteresis. Full cell exhibits an excellent cycling performance with a discharge capacity of 141.5 mA h g−1 and a capacity retention of 92.1% after 400 cycles (0.2C). This work develops an environmentally friendly and economically controllable strategy to recycle SSE from spent SSLBs, guiding future directions of SSLBs large-scale industrial application and green recycling study.

Zeolitic imidazolate framework upgrading polyethylene oxide composite electrolyte for high-energy solid-state lithium batteries.

The energy density of solid-state lithium batteries (SSLBs) has been primarily limited by the low ionic conductivity of solid electrolyte and poor interface compatibility between electrolyte and electrodes. Herein, a multifunctional composite solid polymer electrolyte (CSPE) based on polyethylene oxide (PEO) embedded with zeolitic imidazolate framework-8 deposited on carboxymethyl cellulose (ZIF@CMC) is reported. The ZIF@CMC interpenetrated in PEO matrix creates a continuous Li+ conductive network by combining Zn2+ in ZIF with the unsaturated group in PEO to boost the Li+ transport through the PEO chain segment. On the other hand, Zn2+ can bond with bis(trifluoromethane)sulfonimide (TFSI-) anion, thus promoting the dissolution of lithium salt and releasing more lithium ions. This CSPE demonstrates brilliant electrochemical properties, including a high ionic conductivity of 1.8×10-4 S cm-1 at room temperature and a wide electrochemical window of 5V. The integrated LiFePO4/CSPE/Li batteries using 20wt.% ZIF-8@CMC show excellent reversible capacity of 145.6 mAh g-1 with a capacity retention of 88.95% after 200 cycles at a high current density of 0.5C. Our study proposed a novel and effective strategy to construct high-performance solid-state lithium batteries.

Multiple functional biomolecule-based metal-organic-framework-reinforced polyethylene oxide composite electrolytes for high-performance solid-state lithium batteries

Composite synthesis by adding inorganic fillers to the polymer electrolyte is proposed as a method to obtain solid-state electrolytes (SSE) with high ionic conductivity and long-term stability for high-performance solid-state lithium batteries. Here, we originally introduce biomolecule-based metal-organic frameworks (bio-MOFs) as efficient multiple functional active fillers with naturally abundant functional groups. The proposed bio-MOFs possess plentiful functional Lewis acidic sites composed of open metal nodes and Lewis basic sites consisting of NH2 functional groups and heterocyclic N atoms to satisfy various requirements, such as high ionic conductivity, wide electrochemical window, high Li+ transference number, and long-term stability. Notably, the multiple functional bio-MOF fillers demonstrate good distribution in the PEO matrix owing to strong hydrogen bonding between functional NH2 groups of bio-MOFs. Moreover, it ensures an enhanced electrochemical window and long-term cycling stability. These improvements are attributed to an increase in the number of free Li+ ions due to the strong interaction between the Lewis acidic sites (open metal sites) of the bio-MOF and TFSI− of Li salts and the enhanced amorphous structure of the PEO matrix. Consequently, bio-MOF@polyethylene oxide (PEO):LiTFSI exhibited high ionic conductivity (5.7×10−5 S·cm−1 at 30 °C and 5.7×10−4 S·cm−1 at 60 °C), a wide electrochemical window (<4.57 V vs Li/Li+), and an excellent Li+ transference number (0.63). Moreover, Li/SSE/LiFePO4(LFP) battery cells utilizing bio-MOF@PEO:LiTFSI exhibited a high specific capacity of 153.9 mAh·g−1 at 0.1 C.

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.

Solid-state lithium battery with garnet Li7La3Zr2O12 nanofibers composite polymer electrolytes

In recent years, solid-state lithium-ion batteries with high safety and excellent performance have become a research hotspot. Garnet Li7La3Zr2O12 (LLZO) has been widely used in lithium-ion batteries because of its high ionic conductivity, wide electrochemical window, excellent thermal performance, and promising stability. In this study, Ga-LLZO was prepared by the electrospinning method and combined with PVDF-HFP to prepare a composite polymer electrolyte. The addition of 15 wt% Ga-LLZO nanofibers in the electrolyte improved the ionic conductivity, reaching 8.92 × 10−4 S·cm−1 at room temperature. The electrochemical window for PVDF-HFP/LiTFSI/Ga-LLZO composite polymer electrolyte was 5.2 V vs Li/Li+. In addition, LiFePO4|PVDF-HFP/LiTFSI/Ga-LLZO|Li exhibited good cycling performance and rate capability. High-performance composite electrolyte films of ceramic nanofiber Ga-LLZO and polymer were successfully prepared for high-performance solid-state lithium batteries.

Hexagonal Rodlike Cu-MOF-74-Derived Filler-Reinforced Composite Polymer Electrolyte for High-Performance Solid-State Lithium Batteries

Hexagonal Rodlike Cu-MOF-74-Derived Filler-Reinforced Composite Polymer Electrolyte for High-Performance Solid-State Lithium Batteries

Challenge-driven printing strategies toward high-performance solid-state lithium batteries

Printing techniques promote the development of solid-state batteries by constructing high performance cathodes, dendrite-free anodes, and ideal solid-state electrolytes with versatile structures and configurations.

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.