Solid Lithium Research Articles

Accurate prediction of remaining useful life for lithium-ion battery using deep neural networks with memory features

Li-ion batteries degrade with time and usage, caused by factors like the growth of solid electrolyte interface (SEI), lithium plating, and several other irreversible electrochemical reactions. These failure mechanisms exacerbate degradation and reduce the remaining useful life (RUL). This paper highlights the importance of feature engineering and how a careful presentation of the data can capture the hidden trends in the data. It develops a novel framework of deep neural networks with memory features (DNNwMF) to accurately predict the RUL of Li-ion batteries using features of current and previous n cycles. The results demonstrate that introducing memory in this form significantly improves the accuracy of RUL prediction as root mean square error (RMSE) decreases more than twice with memory compared to without memory. The optimal value of n, referred to as nopt, is also determined, which minimizes the prediction error. Moreover, the number of optimization parameters reduces by more than an order of magnitude if an autoencoder is used in conjunction with the proposed framework (DNNwMF). The framework in this paper results in a trade-off between accuracy and computational complexity as the accuracy improves with the encoding dimensions. To validate the generalizability of the developed framework, two different datasets, i) from the National Aeronautics and Space Administration’s Prognostic Center of excellence and ii) from the Center for Advanced Life Cycle Engineering, are used to validate the results.

In-situ solidification of plastic interlayers enabling high-voltage solid lithium batteries with poly(ethylene oxide) based polymer electrolytes

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes play an important role in the next-generation solid batteries owing to their distinct advantages of low cost, light weight, and easy large-scale production. However, the oxidative decomposition potential lower than 3.8 V (vs Li/Li+) of pure PEO severely hinders its coupling with high-voltage cathodes, directly leading to the limited energy density. Herein, the succinonitrile (SN) plastic crystal interlayers are in-situ solidified between high-voltage cathodes and PEO electrolytes in order to address the critical issue of interfacial incompatibility of PEO against high-voltage cathodes. On the one hand, the liquid SN fully penetrates the porous cathode and spreads out on cathode surface at the temperature higher than its melting point, followed by in-situ solidification forming ion-conducting networks inside the cathode and at cathodic interface after cooling to room temperature. On the other hand, the solidified SN acts as a physical shield to isolate PEO from high-voltage cathodes, avoiding PEO decomposition at high charging potentials. Consequently, PEO can be coupled with a high-voltage LiNi0.6Co0.2Mn0.2O2 cathode, endowing the resultant solid cell with a remarkable cycling stability under cutoff voltages of 4.2, 4.25, and 4.3 V after 100 cycles. Furthermore, a high cathode loading of 10.3 mg cm−2 with initial discharge capacity of 152.4 mAh g−1 (corresponding to 1.57 mAh cm−2) is achieved along with the capacity retention of 80.8% over 50 cycles. This work provides a promising strategy to improve the compatibility of PEO-based electrolytes against high-voltage cathodes via facile in-situ solidification of plastic interlayers.

Codependent failure mechanisms between cathode and anode in solid state lithium metal batteries: mediated by uneven ion flux

An in-depth understanding of the degradation mechanisms is a prerequisite for developing the next-generation all solid-state lithium metal battery (ASSLMB) technology. Herein, synchrotron X-ray computed tomography (SXCT) together with other probing tools and simulation method were employed to rediscover the decaying mechanisms of LiNi0.8Co0.1Mn0.1O2 (NCM)|Li6PS5Cl (LPSCl)|Li ASSLMB. It reveals that the detachment and isolation of NCM particles cause the current focusing on the remaining active regions of cathode. The extent of Li stripping and the likelihood of Li+ plating into LPSCl facing the active NCM particles becomes higher. Besides, the homogeneity of Li stripping/plating is improved by homogenizing the electrochemical reactions at the cathode side by LiZr2(PO4)3 (LZP) coating. These results suggest a codependent failure mechanism between cathode and anode that is mediated by uneven Li ion flux. This work contributes to a holistic understanding of the degradation mechanisms in ASSLMBs and opens new opportunities for their further optimization and development.

Mechanochemical synthesis of LAGP/PEG hybrid solid electrolyte: Investigation of surface structure and chemistry

The drive towards all solid state lithium ion batteries requires discovery of new methods for synthesis of true hybrid solid electrolytes in which organic and inorganic components are chemically associated to simultaneously maximize lithium ion conductivity and processability. Herein, the first mechanochemical milling synthesis of an ambient processable hybrid lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3)/polyethylene glycol (PEG) solid electrolyte is presented. Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) provide evidence that the mechanochemical milling procedure impels a condensation reaction between the ceramic and organic phases which produces a surface product, water. Solid state nuclear magnetic resonance (NMR) spectroscopy confirms that protons from the polymer or associated surface water product are in bonding proximity to the Q2 metaphosphate sites of the glassy phase of the ceramic. This work thus establishes the viability of mechanochemical milling as a synthetic pathway for a class of promising ambient processable hybrid electrolytes.

Functional materials for modifying interfaces between solid electrolytes and lithium electrodes of all-solid-state lithium metal batteries

Functional materials for modifying interfaces between solid electrolytes and lithium electrodes of all-solid-state lithium metal batteries

A two-level optimization framework for battery energy storage systems to enhance economics and minimize long-term capacity fading

This paper proposes a two-level optimization framework for a battery energy storage system to maximize revenue with consideration of the phenomena that cause battery's capacity fading. Instead of solving the scheduling problem as a singular problem, a two-level optimization framework is introduced. The upper-level optimization focuses on maximizing revenue by arbitrage in a real-time electricity market. With the determined operating schedule, the lower-level optimization, solved with particle swarm optimization, determines the optimal charging current that mitigates the side reactions while maintaining economic performance. With the optimal charging current and operating schedule, a pseudo-2D electrochemical model is used to simulate the battery behavior. To reflect the actual behavior of the lithium-ion battery, two side reactions, solid electrolyte interface formation and Lithium plating, are simulated. A case study using California energy prices is presented. With the proposed framework, the results show that the battery's lifespan is extended by up to 5.1 % and overall revenue increases by up to 9.8 % compared to a singular economic optimization utilizing the standard constant current, constant voltage charging protocol.

Enhanced Electrochemical Properties and Optimized Li+ Transmission Pathways of PEO/LLZTO‐Based Composite Electrolytes Modified by Supramolecular Combination

Poly(ethylene oxide) (PEO) and Li6.75La3Zr1.75Ta0.25O12 (LLZTO)‐based composite polymer electrolytes (CPEs) are considered one of the most promising solid electrolyte systems. However, agglomeration of LLZTO within PEO and lack of Li+ channels result in poor electrochemical properties. Herein, a functional supramolecular combination (CD‐TFSI) consisting of active β‐cyclodextrin (CD) supramolecular with self‐assembled LiTFSI salt is selected as an interface modifier to coat LLZTO fillers. Benefiting from vast H‐bonds formed between β‐CD and PEO matrix and/or LLZTO, homogeneous dispersion and tight interface contact are obtained. Moreover, 6Li NMR spectra confirm a new Li+ transmission pathway from PEO matrix to LLZTO ceramic then to PEO matrix in the as‐prepared PEO/LLZTO@CD‐TFSI CPEs due to the typical cavity structure of β‐CD. As a proof, the conductivity is increased from 5.3 × 10−4 S cm−1 to 8.7 × 10−4 S cm−1 at 60 °C, the Li+ transference number is enhanced from 0.38 to 0.48, and the electrochemical stability window is extended to 5.1 V versus Li/Li+. Li‖LiFePO4 CR2032 coin full cells and pouch cells prove the practical application of the as‐prepared PEO/LLZTO@CD‐TFSI CPEs. This work offers a new strategy of interface modifying LLZTO fillers with functional supramolecular combination to optimize PEO/LLZTO CPEs for solid lithium batteries.

Synthesis and characterization of poly [(3,4‐ethylenedioxy) thiophene]:polystyrene sulfonate (PEDOT:PSS) for energy storage device application

AbstractIn this paper, the facile synthesis and characterization aspects of PEDOT:PSS has been presented, in the context of energy storage device technology. PEDOT/PSS particles were synthesized via chemical oxidative polymerization to improve the electrical conductivity. The mechanism for this conductivity enhancement was studied through various chemical and physical characterizations. The structural characterization establishes that all the samples have high surface area and are highly crystalline, showing 3–4 nm spherical nanoparticles with the smoother surface. The electrical conductivity of measured thin film reached 6.23 × 10−6 ℧ cm−1. The use of the PEDOT:PSS as a binders will surely be helpful for scaling up the energy storage technology like high electrical conductivity, the ability for aqueous processing, electrochemical performance, good electrochemical stability and shows good binding ability. It also helps to protect the energy storage devices against electrode particle cracking, solid electrolyte interface (SEI), dendrite formation or lithium plating.

Effect of Particle Size and Pressure on the Transport Properties of the Fast Ion Conductor t‐Li7SiPS8

AbstractAll‐solid‐state batteries promise higher energy and power densities as well as increased safety compared to lithium‐ion batteries by using non‐flammable solid electrolytes and metallic lithium as the anode. Ensuring permanent and close contact between the components and individual particles is crucial for long‐term operation of a solid‐state cell. This study investigates the particle size dependent compression mechanics and ionic conductivity of the mechanically soft thiophosphate solid electrolyte tetragonal Li7SiPS8 (t‐LiSiPS) under pressure. The effect of stack and pelletizing pressure is demonstrated as a powerful tool to influence the microstructure and, hence, ionic conductivity of t‐LiSiPS. Heckel analysis for granular powder compression reveals distinct pressure regimes, which differently impact the Li ion conductivity. The pelletizing process is simulated using the discrete element method followed by finite volume analysis to disentangle the effects of pressure‐dependent microstructure evolution from atomistic activation volume effects. Furthermore, it is found that the relative density of a tablet is a weaker descriptor for the sample's impedance compared to the particle size distribution. The multiscale experimental and theoretical study thus captures both atomistic and microstructural effects of pressure on the ionic conductivity, thus emphasizing the importance of microstructure, particle size distribution and pressure control in solid electrolytes.

Grafted MXenes Based Electrolytes for 5V‐Class Solid‐State Batteries

AbstractPolymer blends based solid polymer electrolytes (SPEs), combining the advantages of multiple polymers, are promising for the utilization of 5 V‐class cathodes (e.g., LiCoMnO4 (LCMO)) with enhanced safety. However, severe macro‐phase separation with defects and voids in polymer blends restrict the electrochemical stability and ionic migration of SPEs. Herein, inorganic compatibilizer polyacrylonitrile grafted MXene (MXene‐g‐PAN) is exploited to improve the miscibility of the poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVHF)/PAN blends and suppress the consolidation of phase particles. The resulting SPE exhibits a high anodic stability with an ionic conductivity of 2.17 × 10−4 S cm−1, enabling a stable and reversible Li platting/stripping (over 2500 h). The fabricated solid Li‖LCMO cell delivers a 5.1 V discharge voltage with a decent capacity (131 mAh g−1) and cycling performance. Subsequently, the solid all‐in‐one graphite‖LCMO battery is also constructed to extend the application of MXene based SPEs in flexible batteries. Benefiting from the interface‐less design, outstanding mechanical flexibility and stability is achieved in the battery, which can endure various deformations with a low‐capacity loss (< ≈10%). This study signifies a significant development on solid flexible lithium ion batteries with enhanced performance, stability, and reliability by investigating the miscibility of polymer blends, benefiting for the design of high‐performance SPEs.

Thin films of solid electrolyte lithium sulfate deposited by e-beam evaporation

Fabrication of lithium sulfate (Li2SO4) thin films has been successfully attempted by the electron beam evaporation technique, and the deposition conditions were systematically optimized to get stable Li2SO4 thin films. The structural, optical, and electrical properties of the fabricated Li2SO4 thin films were investigated using X-ray diffraction, scanning electron microscope, vibrational spectroscopy techniques, optical transmission spectroscopy, and electrical conductivity measurements. The as-deposited Li2SO4 thin films were X-ray amorphous, although they exhibited Bragg peaks corresponding to Li2SO4 when annealed. The fundamental vibrational modes of sulfate anions in thin films were observed through FT-IR and Raman spectroscopy studies. The ionic conductivity value for the thin film was found to be 2.03 × 10-8 S cm−1 at 373 K, which is of three orders of magnitude higher than that of the bulk.

Crosslinked polymer electrolyte constructed by metal-oxo clusters for solid lithium metal batteries

By using structurally well-defined metal-oxo clusters as crosslinkable nanofillers, the authors develop a hybrid inorganic/organic crosslinked polymer electrolyte. With the favorable electrochemical and mechanical properties, as well as the enhanced lithium dendrite-suppressing capability, the metal-oxo cluster crosslinked polymer electrolyte can significantly improve the capacities, rate capabilities, and cycling stabilities of solid lithium metal batteries. Download : Download high-res image (175KB)Download : Download full-size image

EC modified PEO/PVDF-LLZO composite electrolytes for solid state lithium metal batteries

The polymer-ceramic composite electrolytes have great application potential for next-generation solid state lithium batteries, as they have the merits to eliminate the problem of liquid organic electrolytes and enhancing chemical/electrochemical stability. However, polymer-ceramic composite electrolytes show poor ionic conductivity, which greatly hinders their practical applications. In this work, the addition of plasticizer ethylene carbonate (EC) into polymer-ceramic composite electrolyte for lithium batteries effectively promotes the ionic conductivity. A high ionic conductivity can be attained by adding 40 wt% EC to the polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF)-Li7La3Zr2O12 (LLZO) based polymer-ceramic composite electrolytes, which is 2.64 × 10−4 S cm−1 (tested at room temperature). Furthermore, the cell assembled with lithium metal anode, this composite electrolyte， and LiFePO4 cathode can work more than 80 cycles at room temperature (tested at 0.2 C). The battery delivers a high reversible specific capacity after 89 cycles, which is 119 mAh g−1.

Designing Bidirectionally Functional Polymer Electrolytes for Stable Solid Lithium Metal Batteries

AbstractThe development of high energy density lithium metal batteries has been retarded by the uncontrolled lithium dendrite formation and unstable Ni‐rich cathode–electrolyte interface (CEI). Herein, the bidirectionally functional polymer electrolytes (BDFPE) are designed via direct UV solidification of functional polymer species on electrode surfaces to simultaneously handle the interface issues faced by anodes and cathodes. By constructing the BDFPE, a smooth and dendrite‐free lithium deposition is enabled for Li||Li symmetry cells after 1800 h ultralong cycling at 1 mA cm−2 and 1 mAh cm−2, which are attributed to the fast ion conductivity (5.84 × 10−4 S cm−1), high Li+ transfer number (0.69) of BDFPE and low interfacial resistance between electrode and solid electrolytes. Furthermore, Li||LiNi0.6Co0.2Mn0.2O2 batteries demonstrate a favorable cycling and rate capability, and a stable and phosphate‐based CEI layer is constructed in situ. DFT studies reveal that the functional additives FEC and TEP participate in the interface formation. The finding provides a promising design strategy to accommodate the anode and cathode interfaces for high energy density lithium metal batteries.

Dual Single-Atom Moieties Anchored on N-Doped Multilayer Graphene As a Catalytic Host for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are promising for energy storage, especially in the era of carbon neutrality. Nonetheless, the sluggish kinetics of converting soluble lithium polysulfides into solid lithium sulfide impedes its development. In this work, we design Fe and Co dual single-atom moieties anchored on N-doped multilayer graphene (FeCoNGr) as a catalytic sulfur cathode host for Li-S batteries. With an efficient catalytic role in converting soluble lithium polysulfides into solid Li2S, the FeCoNGr-based Li-S cell demonstrates a capacity of 878.7 mA h g-1 at 0.2 C and retains 77.4% of the initial value after 100 cycles. The first and retained capacities are ∼1.7 and ∼1.8 times those of the NGr (without single atoms)-based cell, respectively. Theoretical calculations reveal that the Fe-N4 moiety has a higher binding energy toward low-order lithium polysulfides, while the Co-N4 moiety has a higher binding energy toward high-order lithium polysulfides. The efficient catalytic conversion of soluble lithium polysulfides into solid lithium sulfides of FeCoNGr plays important roles in outperforming NGr. This work enhances our knowledge on the tandem role of dual single-atom moieties and confirmed the high catalytic efficiency of single-atom catalysts in Li-S batteries.

An Ultrathin Asymmetric Solid Polymer Electrolyte with Intensified Ion Transport Regulated by Biomimetic Channels Enabling Wide‐Temperature High‐Voltage Lithium‐Metal Battery

AbstractSolid electrolytes that can be made compatible with high‐voltage cathodes are greatly desired to increase the energy density of solid lithium metal batteries (SLMBs). However, no monophase polymer or ceramic examples can simultaneously exhibit strong electrochemical stability and reasonable lithium compatibility due to their limited internal energy gap. Herein, a novel asymmetric solid polymer electrolyte (AMSE) with tailored Li+ transport mechanisms is proposed. It is composed of a high‐voltage layer (HVL, polyacrylonitrile/ionic liquid [IL]) and lithium‐compatible layer (LCL, poly(vinylidene fluoride‐co‐hexafluoropropylene)/UiO‐66‐SO3Li). The HVL exhibits a vehicular Li+ transport mechanism with the introduction of IL, which achieves exceptional‐electrochemical stability and reduced interfacial resistance. Due to the complexation between anions and UiO‐66‐SO3Li, a structural diffusion mechanism is achieved in LCL, realizing a quasi‐single‐ion migration in biomimetic ionic channels. The as‐proposed asymmetric configuration, combined with the transport mechanisms, leads to a gradient distribution of electric potential and Li+ in the electrolyte, thus realizing a stable Li+ flux, which is proved by COMSOL‐Multiphysics. The AMSE‐based SLMBs and scale‐up pouch cells show remarkable cycling stability at 4.3 V from room temperature (Li/LiNi0.8Mn0.1Co0.1O2, 3.27 mAh cm−2) to 100 °C. The strategy of facilitating the transport mechanism is expected to provide new pathways for designing next‐generation SLMBs with high energy density.

Safety, high-performing and effects of the N/P ratio of a solid lithium ion battery using PEGDME based polymer electrolytes

In this study, we report on the electrochemical properties of a solid state lithium ion battery (LIB) using a poly (ethylene glycol) dimethyl ether (PEGDME)-based solid polymer electrolyte (P-SPE). The LIB is prepared using a LiFePO4 (LFP) cathode and graphite anode material with P-SPE, and the kinetic properties of the lithium ions in the P-SPE are investigated. The synthesized P-SPE is shown to be suitable solid polymer electrolyte candidate for LIB applications. LFP and graphite are selected as electrode materials to validate their effectiveness in different battery cells with respect to their high energy density and inherent safety. The five-layer stacked 5 × 6 cm2 pouch-type LIB demonstrates a high capacity of 90 mAh (0.6 mAh/cm2) or more in the initial cycle, and it shows cycle stability with a capacity decrease of 20% over 500 cycles. We test the manufactured pouch-type full cells under extreme conditions (e. g., cutting, crushing and exposure of the battery cell to the atmosphere). LIBs using the developed P-SPE are promising solid polymer electrolyte candidates for wearable LIB as well as high energy LIB applications.

A Study of Li3.8Ge0.9S0.1O4 Solid Electrolyte Stability Relative to Electrode Materials of Lithium Power Sources

The stability of Li3.8Ge0.9S0.1O4 lithium-conducting solid electrolyte versus lithium metal and Li–V bronze Li1.3V3O8 is studied in the present research. Isothermal heat treatment and thermal analysis of the mixtures of Li1.3V3O8 and Li3.8Ge0.9S0.1O4 powders indicate that there is no interaction between them below 300–350 °C. Moreover, Li3.8Ge0.9S0.1O4 solid electrolyte is stable versus lithium at 100 °C for 240 h. A model of a lithium-ion power source with a Li1.3V3O8-based cathode and a lithium metal anode is assembled and tested. The data obtained show that Li3.8Ge0.9S0.1O4 can be used in all-solid-state medium-temperature lithium and lithium-ion batteries.

An enhanced interface between garnet solid electrolyte and lithium through multifunctional lithium titanate anode-additive for solid-state lithium batteries

Garnet-structured solid-state electrolytes are getting considerable attention due to their high figure of merit over other inorganic solid-state electrolytes. The high lithium-ion conductivity and exceptional stability with metallic lithium over a wide voltage window open the door for the practical realization of an all-solid-state battery. However, the lithiophobic nature of garnet solid electrolytes creates huge interface resistance, which restricts achieving high critical current density. Herein a multifunctional composite anode containing lithium metal and lithium titanate (Li4Ti5O12) is introduced to tackle the interface challenges with the garnet solid electrolyte. The partial reduction of titanium in the composite enhances the electronic conductivity of the anode, and the intrinsic structural advantages of lithium titanate are expected to accommodate volume change as well. The prepared symmetric cell with the composite anode is found to have a minimal areal-specific resistance of 27 Ω cm2, while that of the pristine lithium anode is 249 Ω cm2. The cell has also run with a better critical current density (0.35 mA cm−2) than the pristine lithium (0.15 mA cm−2). A full cell study with a lithium iron phosphate cathode offers a capacity of 145 mAh g−1 at 0.2 C and runs for 100 cycles at 1 C with minimum capacity loss.

Enhancing the interfacial stability between argyrodite sulfide-based solid electrolytes and lithium electrodes through CO2 adsorption

The CO2 treatment on argyrodite sulfide-based solid electrolyte Li6PS5Cl (LPSC) can effectively improve the interfacial stability between the Li and LPSC.