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Because of the high specific capacity and low cost, Ni-rich layered oxide (NRLO) cathodes are one of the most promising cathode candidates for the next high-energy-density lithium-ion batteries. However, they face structure and interface instability challenges, especially the battery safety risk caused by using an intrinsic flammable organic liquid electrolyte. In this regard, a solid electrolyte with high safety is of great significance to promote the development of energy storage. Among them, sulfide electrolytes are considered to be the most potential substitutes for liquid electrolytes because of their high ionic conductivity and good processing properties. Nevertheless, the interfacial incompatibility between the sulfide electrolyte and NRLO cathode is the critical challenge for high-performance sulfide all-solid-state lithium batteries (ASSLBs). In this review, we summarize the problems of the Ni-rich cathode/sulfide solid electrolyte interface and the strategies to improve the interface stability. On the basis of these insights, we highlight the scientific problems and technological challenges that need to be resolved urgently and propose several potential directions to further improve the interface stability. The objective of this study is to provide a comprehensive understanding and insightful recommendations for the enhancement of the sulfide ASSLBs with NRLO cathode.

Solid-state symmetrical battery represents a promising paradigm for future battery technology. However, its development is hindered by the deficiency of high-performance bipolar electrodes and compatible solid electrolytes. Herein, a quasi-solid-state all-V2O5 battery constructed by a binder-free carbon fabric-V2O5 nanowires@graphene (CVOG) bipolar electrode and a softly cross-linked polyethylene oxide-based solid polymer electrolyte (SPE) is reported. The synergetic effect of nano-structuring of V2O5, hierarchical conductive network, and graphene wrapping endows the CVOG electrode with boosted reaction kinetics and suppressed vanadium dissolution. The cathodic and anodic reactions of CVOG are decoupled by electrochemical analysis, conceiving the feasibility of constructing all-V2O5 full battery. In manifesting the solid-state all-V2O5 battery, the robust and elastic SPE exhibits high ionic conductivity, tight/self-adaptable electrolyte-electrode contact, and a low charge-transfer barrier. The resultant solid-state full battery exhibits a high reversible capacity of 158 mAh g-1 at 0.1 C, good capacity retention of over 61% from 0.1 C to 2 C, and remarkable cycling stability of 77% capacity retention after 1000 cycles at 1 C, which surpass other solid-state symmetrical batteries. Hence, this work provides a practice of high-performance solid-state batteries with symmetrical configuration and is constructive for next-generation battery technology.

Na-O2 batteries have emerged as promising candidates due to their high theoretical energy density (1,601 Wh kg-1), the potential for high energy storage efficiency, and the abundance of sodium in the earth's crust. Considering the safety issue, quasi-solid-state composite polymer electrolytes are among the promising solid-state electrolyte candidates. Their higher mechanical toughness provides superior resistance to dendritic penetration compared with traditional liquid electrolytes. The flexibility of the composite polymer electrolyte matrix allows it to conform to various battery configurations and considerably reduces safety concerns related to the combustion risks associated with conventional liquid electrolytes. In this study, we employed poly(ethylene oxide) (PEO) and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as the polymer matrix and sodium ion-conducting agent, respectively. We incorporated nanosized NZSP (25 wt %) to create the composite polymer electrolyte membrane. This CPE design facilitates ion conduction pathways through both sodium salt and NZSP. By utilizing a liquid electrolyte infiltration method, we successfully enhanced its ionic conductivity, achieving an ionic conductivity of 10-4 S cm-1 at room temperature.

Replacing liquid electrolytes with solid polymer electrolytes (SPEs) is considered as a vital approach to developing sulfur (S)-based cathodes. However, the polysulfides shuttle and the growth of lithium (Li) dendrites are still the major challenges in polyethylene oxide (PEO)-based electrolyte. Here, an all-solid-state Li metal battery with flexible PEO-Li10 Si0.3 PS6.7 Cl1.8 (LSPSCl)-C-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) composite cathode (FCC) and PEO-LSPSCl-LiTFSI composite electrolyte (S-CPE) is designed. The initial capacity of the Li|S-CPE|FCC battery is 414 mAh g-1 with 97.8% capacity retention after 100 cycles at 0.1 A g-1 . Moreover, the battery displays remarkable capacity retention of 80% after 500 cycles at 0.4 A g-1 . Cryo-transmission electron microscopy (Cryo-TEM) reveals rich large-sized Li2 CO3 particles at the Li/PEO interface blocking the Li+ transport, but the layer with rich Li2 O nanocrystals, amorphous LiF and Li2 S at the Li/S-CPE interface suppresses the growth of lithium dendrite and stabilizes the interface. In situ optical microscopy demonstrates that the excellent cyclic stability of FCC is ascribed to the reversible shuttle of P-S-P species, resulting from the movement of ether backbone in PEO. This study provides strategies to mitigate the polysulfide shuttle effect and Li dendrite formation in designing high energy density solid-state Li-S-based batteries.

Since the electrochemical potential of lithium metal was systematically elaborated and measured in the early 19th century, lithium-ion batteries with liquid organic electrolyte have been a key energy storage device and successfully commercialized at the end of the 20th century. Although lithium-ion battery technology has progressed enormously in recent years, it still suffers from two core issues, intrinsic safety hazard and low energy density. Within approaches to address the core challenges, the development of all-solid-state lithium-ion batteries (ASSLBs) based on halide solid-state electrolytes (SSEs) has displayed potential for application in stationary energy storage devices and may eventually become an essential component of a future smart grid. In this Review, we categorize and summarize the current research status of halide SSEs based on different halogen anions from the perspective of halogen chemistry, upon which we summarize the different synthetic routes of halide SSEs possessing high room-temperature ionic conductivity, and compare in detail the performance of halide SSEs based on different halogen anions in terms of ionic conductivity, activation energy, electronic conductivity, interfacial contact stability, and electrochemical window and summarize the corresponding optimization strategies for each of the above-mentioned electrochemical indicators. Finally, we provide an outlook on the unresolved challenges and future opportunities of ASSLBs.

Solid-state Li-S and Li-Se batteries are promising devices that can address the safety and electrochemical stability issues that arise from liquid-based systems. However, solid-state Li-Se/S batteries usually present poor cycling stability due to the high resistance interfaces and decomposition of solid electrolytes caused by their narrow electrochemical stability windows. Here, an integrated solid-state Li-Se battery based on a halide Li3 HoCl6 solid electrolyte with high ionic conductivity is presented. The intrinsic wide electrochemical stability window of the Li3 HoCl6 and its stability toward Se and the lithiated species effectively inhibit degeneration of the electrolyte and the Se cathode by suppressing side reactions. The inherent thermodynamic mechanism of the lithiation/delithiation process of the Se cathode in solid is also revealed and confirmed by theoretical calculations. The battery achieves a reversible capacity of 402 mAh g-1 after 750 cycles. The electrochemical performance, thermodynamic lithiation/delithiation mechanism, and stability of metal-halide-based Li-Se batteries confer theoretical study and practical applicability that extends to other energy-storage systems.

Manufacturing advanced solid-state electrolytes (SSEs) for flexible rechargeable batteries becomes increasingly important but remains grand challenge. The sophisticated structure of robust animal dermis and good water-retention of plant cell in nature grant germane inspirations for designing high-performance SSEs. Herein, tough bioinspired SSEs with intrinsic hydroxide ion (OH- ) conduction are constructed by in situ formation of OH- conductive ionomer network within a hollow-polymeric-microcapsule-decorated hydrogel polymer network. By virtue of the bioinspired design and dynamic dual-penetrating network structure, the bioinspired SSEs simultaneously obtain mechanical robustness with 1800% stretchability, good water uptake of 107 g g-1 and water retention, and superhigh ion conductivity of 215 mS cm-1 . The nanostructure of bioinspired SSE and related ion-conduction mechanism are revealed and visualized by molecular dynamics simulation, where plenty of compact and superfast ion-transport channels are constructed, contributing to superhigh ion conductivity. As a result, the flexible solid-state zinc-air batteries assembled with bioinspired SSEs witness high power density of 148 mW cm-2 , specific capacity of 758 mAh g-1 and ultralong cycling stability of 320 h as well as outstanding flexibility. The bioinspired methodology and deep insight of ion-conduction mechanism will shed light on the design of advanced SSEs for flexible energy conversion and storage systems.

Traditional liquid electrolyte batteries face safety concerns such as leakage and flammability, while further optimization has reached a bottleneck. Solid electrolytes are therefore considered a promising solution. Here, a PEO-LiTFSI-LATP (PELT) composite electrolyte was developed by incorporating nanosized Li1.3Al0.3Ti1.7(PO4)3 fillers into a polyethylene oxide matrix, effectively reducing crystallinity, enhancing mechanical robustness, and providing additional Li+ transport channels. The PELT electrolyte exhibited an electrochemical stability window of 4.9 V, an ionic conductivity of 1.2 × 10-4 S·cm-1 at 60 °C, and a Li+ transference number (tLi+) of 0.46, supporting stable Li plating/stripping for over 600 h in symmetric batteries. More importantly, to address poor electrode-electrolyte contact in conventional layered cells, we proposed an integrated electrode-electrolyte architecture by in situ coating the PELT precursor directly onto LiFePO4 cathodes. This design minimized interfacial impedance, improved ion transport, and enhanced electrochemical stability. The integrated PELT/LFP battery retained 74% of its capacity after 200 cycles at 1 A·g-1 and showed superior rate capability compared with sandwich-type batteries. These results highlight that coupling LATP-enhanced polymer electrolytes with an integrated architecture is a promising pathway toward high-safety, high-performance solid-state lithium-ion batteries.

As the most abundant and renewable biopolymer, cellulose has found applications in a range of fields such as healthcare, packaging, electronics and environmental remediation, contributing to the transition towards sustainability. Here we apply a green and scalable process transforming cellulose to a robust electrolyte exhibiting lithium (Li) ion conductivity of 1.09 × 10<SUP>−3</SUP> S cm<SUP>−1</SUP> with a transference number of 0.81 and mechanical strength of 12 MPa. Our process takes advantage of the rich hydroxyl groups in the cellulose which are replaced by phthalic anhydride through an esterification reaction to form cellulose phthalate (CP). Combined experimental and theoretical analyses reveal that the introduction of phthalate groups is essential to not only ensure effective multi-oxygen interaction with Li ions to create fast ion transportation channels, but also facilitates the intermolecular hydrogen bond responsible for the impressive mechanical properties. The CP biopolymer film is even compatible with most commercial cathode materials, and our solid-state Li/CP/LiFePO<SUB>4</SUB> cells show better performance and notably good stability over 1,000 cycles than that of a baseline Li-ion cell with a flammable organic liquid electrolyte. Our study unlocks the enormous potential of cellulose utilization in batteries and opens an avenue for the development of abundant and sustainable solid-state electrolytes.

Developing high specific energy Lithium-ion (Li-ion) batteries is of vital importance to boost the production of efficient electric vehicles able to meet the customers' expectation related to the electric range of the vehicle. One possible pathway to high specific energy is to increase the operating voltage of the Li-ion cell. Cathode materials enabling operation above 4.2 V are available. The stability of the positive electrode-electrolyte interface is still the main bottleneck to develop high voltage cells. <P />Moreover, important research efforts are devoted to the substitution of graphite anodes with Li metal: this would improve the energy density of the cell dramatically. The use of metallic lithium is prevented by the dendrite growth during charge, with consequent safety problems. To suppress the formation of dendrites solid-state electrolytes are considered the most promising approach. <P />For these reasons the present review summarizes the most recent research efforts in the field of high voltage solid-state electrolytes for high energy density Li-ion cells.

Lithium and sodium (Na) mixed polyanion solid electrolytes for all-solid-state batteries display some of the highest ionic conductivities reported to date. However, the effect of polyanion mixing on the ion-transport properties is still not fully understood. Here, we focus on Na<SUB>1+x</SUB>Zr<SUB>2</SUB>Si<SUB>x</SUB>P<SUB>3‒x</SUB>O<SUB>12</SUB> (0 ≤ x ≤ 3) NASICON electrolyte to elucidate the role of polyanion mixing on the Na-ion transport properties. Although NASICON is a widely investigated system, transport properties derived from experiments or theory vary by orders of magnitude. We use more than 2000 distinct ab initio-based kinetic Monte Carlo simulations to map the compositional space of NASICON over various time ranges, spatial resolutions and temperatures. Via electrochemical impedance spectroscopy measurements on samples with different sodium content, we find that the highest ionic conductivity (i.e., about 0.165 S cm<SUP>-1</SUP> at 473 K) is experimentally achieved in Na<SUB>3.4</SUB>Zr<SUB>2</SUB>Si<SUB>2.4</SUB>P<SUB>0.6</SUB>O<SUB>12</SUB>, in line with simulations (i.e., about 0.170 S cm<SUP>-1</SUP> at 473 K). The theoretical studies indicate that doped NASICON compounds (especially those with a silicon content x ≥ 2.4) can improve the Na-ion mobility compared to undoped NASICON compositions.

Accurately predicting aging of lithium-ion batteries would help to prolong their lifespan, but remains a challenge owing to the complexity and interrelation of different aging mechanisms. As a result, aging prediction often relies on empirical or data-driven approaches, which obtain their performance from analyzing large datasets. However, these datasets are expensive to generate and the models are agnostic of the underlying physics and thus difficult to extrapolate to new conditions. In this article, a physical model is used to predict capacity fade caused by solid-electrolyte interphase (SEI) growth in 62 automotive cells, aged with 28 different protocols. Three protocols parametrize the time, current and temperature dependence of the model, the state of charge dependence results from the anode's open circuit voltage curve. The model validation with the remaining 25 protocols shows a high predictivity with a root-mean squared error of $1.28\%$. A case study with the so-validated model shows that the operating window, i.e. maximum and minimum state of charge, has the largest impact on SEI growth, while the influence of the applied current is almost negligible. Thereby the presented model is a promising approach to better understand, quantify and predict aging of lithium-ion batteries.

Several active areas of research in novel energy storage technologies, including three-dimensional solid state batteries and passivation coatings for reactive battery electrode components, require conformal solid state electrolytes. We describe an atomic layer deposition (ALD) process for a member of the lithium phosphorus oxynitride (LiPON) family, which is employed as a thin film lithium-conducting solid electrolyte. The reaction between lithium tert-butoxide (LiO$^t$Bu) and diethyl phosphoramidate (DEPA) produces conformal, ionically conductive thin films with a stoichiometry close to Li$_2$PO$_2$N between 250 and 300$^\circ$C. The P/N ratio of the films is always 1, indicative of a particular polymorph of LiPON which closely resembles a polyphosphazene. Films grown at 300$^\circ$C have an ionic conductivity of $6.51\:(\pm0.36)\times10^{-7}$ S/cm at 35$^\circ$C, and are functionally electrochemically stable in the window from 0 to 5.3V vs. Li/Li$^+$. We demonstrate the viability of the ALD-grown electrolyte by integrating it into full solid state batteries, including thin film devices using LiCoO$_2$ as the cathode and Si as the anode operating at up to 1 mA/cm$^2$. The high quality of the ALD growth process allows pinhole-free deposition even on rough crystalline surfaces, and we demonstrate the fabrication and operation of thin film batteries with the thinnest (<100nm) solid state electrolytes yet reported. Finally, we show an additional application of the moderate-temperature ALD process by demonstrating a flexible solid state battery fabricated on a polymer substrate.

All-solid-state Li-ion batteries promise safer electrochemical energy storage with larger volumetric and gravimetric energy densities. A major concern is the limited electrochemical stability of solid electrolytes and related detrimental electrochemical reactions, especially because of our restricted understanding. Here we demonstrate for the argyrodite, garnet and NASICON type solid electrolytes, that the favourable decomposition pathway is indirect rather than direct, via (de)lithiated states of the solid electrolyte, into the thermodynamically stable decomposition products. The consequence is that the electrochemical stability window of the solid electrolyte is significantly larger than predicted for direct decomposition, rationalizing the observed stability window. The observed argyrodite metastable (de)lithiated solid electrolyte phases contribute to the (ir)reversible cycling capacity of all-solid-state batteries, in addition to the contribution of the decomposition products, comprehensively explaining solid electrolyte redox activity. The fundamental nature of the proposed mechanism suggests this is a key aspect for solid electrolytes in general, guiding interface and material design for all-solid-state batteries.

All solid state batteries are claimed to be the next-generation battery system, in view of their safety accompanied by high energy densities. A new advanced, multiscale compatible, and fully three dimensional model for solid electrolytes is presented in this note. The response of the electrolyte is profoundly studied theoretically and numerically, analyzing the equilibrium and steady state behaviors, the limiting factors, as well as the most relevant constitutive parameters according to the sensitivity analysis of the model.

Transformations at interfaces between solid-state electrolytes (SSEs) and lithium metal electrodes can lead to high impedance and capacity decay during cycling of solid-state batteries, but the links between structural/chemical/mechanical evolution of interfaces and electrochemistry are not well understood. Here, we use in situ X-ray computed tomography to reveal the evolution of mechanical damage within a Li1+xAlxGe2–x(PO4)3 (LAGP) SSE caused by interphase growth during electrochemical cycling. The growth of an interphase with expanded volume drives fracture in this material, and the extent of fracture during cycling is found to be the primary factor causing the impedance increase, as opposed to the resistance of the interphase itself. Cracks are observed to initiate near the edge of the lithium/LAGP interface, which agrees with simulations. The chemomechanical effects of interphase growth studied here are expected to play a role in a variety of SSE materials, and this work is a step toward designing durable interfaces.