Li Capacity Research Articles

Reveal the capacity loss of lithium metal batteries through analytical techniques

AbstractHigh energy density and stable long cycle are the basic requirements for an ideal battery. At present, lithium (Li) metal anode is regarded as one of the most promising anode materials, but it still faces major problems in terms of capacity fading and safe and stable long‐term cycle. The reason for the continuous fading of Li anode capacity is mainly due to the loss of active Li source, and the loss of Li source is mainly due to the continuous generation of dead Li. At the same time, the unstable interface and dendrite growth of Li anodes during the Li plating/delithiation process eventually lead to battery safety issues. In fact, recent studies have shown that the disordered expansion of dendrites is the main reason for the infinite generation of dead Li. Therefore, here we take different detection techniques as clues, review the exploration process of qualitative and quantitative research on the source and mechanism of Li capacity loss, and summarize the strategies to reduce dead Li generation and capacity fading by inhibiting dendrite formation. In particular, we give suggestions on the development of advanced testing methods on how to further study the problem of dead Li, and also give relevant strategy suggestions on how to completely solve the problem of capacity loss in the future, with the main goal of suppressing dendrites.

Theoretical exploration of AlB2 monolayer with high energy storage properties in the field of ion battery materials

The rapid development of electric vehicles has promoted researchers to explore the field of high-capacity batteries. Two-dimensional (2D) materials have been proven to have ultra-high storage capacity due to their unique structural advantages. A first-principles approach was applied here to verify the feasibility of the novel AlB2 monolayer as an anode material with ultra-high storage capacity for Li/Na-ion batteries. The Li capacity of AlB2 monolayer is up to 3308.6 mAh/g. Meanwhile, the Na capacity up to 1654.3 mAh/g. It is worth noting that the diffusion barrier of the monolayer is extremely low (Li: 0.50 eV; Na 0.26 eV). The results show that AlB2 monolayer is a kind of anode material for high energy storage, which provides a new choice for the development of long-life battery.

Investigation of Lithium Deposition in Tri-Layer Llzo Garnet Structure As a Function of Cell Cycling Using Nuclear Reaction Analysis Method

A key challenge of lithium metal batteries is the volumetric expansion of battery after several charging cycles due to the non-uniform deposition of lithium on anode. This leads to lithium dendrite formation compromising battery safety, and poor lifetime. We adapted tri-layer (porous-dense-porous) Al-doped Lithium Lanthanum Zirconium Oxide (LLZO) host (separator) via tape casting. During cycling lithium is deposited in the porous structure preventing dendrite formation. XRD analysis of annealed host structure confirmed presence of cubic phase LLZO which provides higher ionic conductivity. We measured Li distribution on LLZO host structure before and after different cell cycling conditions and investigated the failure mechanism. We performed concentration depth profiles of 7Li and 6Li isotopes by Nuclear Reaction Analysis (NRA) using two different methods: Proton Induced Gamma-ray Emission (PIGE) and Proton Induced Alpha-particle Reaction (Particle-Particle reaction) and compared the results for accuracy. Depth profile of 7Li confirmed 33 at % Li at 0.44µm thickness before cycling which was increased after cycling. The Gaussian distribution of NRA data indicated a uniform Li depth profile in the dense layer. Through electrochemical testing, we measured that Li capacity loss after 5 and 25 charging cycles with 0.1C rate, 1.51mAh and 2.89mAh, respectively, in tri layered LLZO separator.

A contribution to understanding ion-exchange mechanisms for lithium recovery from industrial effluents of lithium-ion battery recycling operations

Industrial effluents or process waters generated from spent lithium-ion battery recycling operations often contain high concentrations of lithium ions (Li+). This study characterizes the composition of process water obtained from pre-treatment and concentration operations of LIBs recycling. Ion-exchange experiments are conducted using synthetic lithium solutions (1 g/L) and industrial waters to understand Li+ recovery. Employing four commercial cationic resins, fast Li+ exchange kinetics are observed fitting the pseudo-second order model. The equilibrium isotherm data corresponds to the Langmuir adsorption model and reveals a Li capacity of 30–32 mg/g using Amberlite™ IRC 120 H, 70 mg/g using Lewatit® TP 308 H, 37–40 mg/g using Lewatit® TP 208 Na, and 37–41 mg/g using Lewatit® TP 260 Na. While the resins initially demonstrate moderate affinity for Li+, this can be significantly enhanced by increasing the Li+ concentration. Notably, as LIBs recycling operation effluents typically contain minimal competing ions, these results underscore the potential of employing ion exchange as a viable method to recover and concentrate lithium before precipitation into lithium salts.

Decreased Electrically and Increased Ionically Conducting Scaffolds for Long-Life, High-Rate and Deep-Capacity Lithium-Metal Anodes.

Lithium (Li) metal batteries are deemed as promising next-generation power solutions but are hindered by the uncontrolled dendrite growth and infinite volume change of Li anodes. The extensively studied 3D scaffolds as solutions generally lead to undesired "top-growth" of Li due to their high electrical conductivity and the lack of ion-transporting pathways. Here, by reducing electrical conductivity and increasing the ionic conductivity of the scaffold, the deposition spot of Li to the bottom of the scaffold can be regulated, thus resulting in a safe bottom-up plating mode of the Li and dendrite-free Li deposition. The resulting symmetrical cells with these scaffolds, despite with a limited pre-plated Li capacity of 5mAhcm-2, exhibit ultra-stable Li plating/stripping for over 1 year (11 000h) at a high current density of 3mAcm-2 and a high areal capacity of 3mAhcm-2. Moreover, the full cells with these scaffolds further demonstrate high cycling stability under challenging conditions, including high cathode loading of 21.6mgcm-2, low negative-to-positive ratio of 1.6, and limited electrolyte-to-capacity ratio of 4.2gAh-1.

Stable ultrathin lithium metal anode enabled by self-adapting electrochemical regulating strategy

Ultrathin lithium (Li) metal foils with controllable capacity could realize high-specific-energy batteries; however, the pulverization of Li metal foils due to its extreme volume change results in rapid active Li loss and capacity fading. Here, we report a strategy to stabilize ultrathin Li metal anode via in-situ transferring Li from ultrathin Li foil into a well-designed three-dimensional gradient host during a cycling process. A three-dimensional carbon fiber with gradient distribution of Ag nanoparticles is placed on the ultrathin Li foil in advance and acts as a Li reservoir, guiding Li deposition into its interior and thus alleviating the volume change of ultrathin Li foil anodes. Hence, a high reversibility of Li metal is achieved and Li pulverization is suppressed, which can be witnessed by a long cyclic life in the symmetric cells. The proposed method offers a versatile and facile approach for protecting ultrathin Li metal anodes, which will boost their commercial application process.

Electronegative graphene film based interface-chemistry regulation for stable lithium metal batteries

To achieve practical application of lithium (Li) metal anodes for high-energy–density batteries, the primary challenges of the inhomogeneous solid electrolyte interphase (SEI) and irregular Li electrochemical stripping/depositing behaviors should been surmounted. So as to homogenize Li+ distribution and stabilize the SEI layer, herein, we reported a partially reduced graphene oxide (PrGO) film with a manageable electronegativity as an ideal Li host to construct composite electrode (PrGO@Li). The fabricated PrGO with tunable oxygen amount and negatively charge can achieve controllable Li capacity avoiding excess Li. More importantly, the electronegative PrGO film matrix can cause an electrostatic force and thereby regulate the Li+ distribution pattern and diffusion kinetics, which induces a homogeneous and stable LiF-rich SEI and highly conformal Li+ stripping/deposition behaviors without Li dendrites. As a result, the optimal PrGO@Li electrode delivers long-term reversible Li+ stripping/depositing processes with an extremely low overpotential (7 mV) after 2000 h cycling at 20 mA cm−2 and 10 mAh cm−2. Moreover, the full battery based on this anode paired with LiFePO4 cathode exhibits outstanding cycling stability, high rate capacity and excellent flexibility characters. Meanwhile, the controllable PrGO films can also be loading with sulfur as cathodes for satisfactory Li/sulfur batteries. This research deeply analyzes the intermediation mechanism between the graphene host and Li+ on the electrochemical behaviors, and offers universal guidance for the development of high-performance Li-metal batteries.

Interfacial pressure improves calendar aging of lithium metal anodes

Lithium (Li) metal is a promising anode because its theoretical specific capacity is approximately ten times larger than graphite. However, Li anodes suffer from long-term capacity fade due to Li stranding (becoming electronically disconnected) and electrolyte decomposition. Applied interfacial pressure has been shown to improve Li anode cycling, likely due to reincorporating stranded or “dead” Li into the anode. Calendar aging can also lead to Li capacity loss due to electrolyte decomposition/Li corrosion and the formation of stranded Li. Some research suggests that calendar aging during cycling results in reversible capacity losses due to Li stranding and reconnection. We here investigate the effect of applied interfacial pressure on Li anode calendar aging during cycling with incorporated rest steps in a localized high-concentration electrolyte (LHCE) to understand if pressure can mitigate stranded Li formation during rest by manipulating the Li morphology. Pouch cells exhibit more stable cycling and denser Li deposits between 10 kPa and 1,000 kPa of applied pressure compared to no applied pressure. Despite drops in CE during periodic rest cycles, the average cumulative lost capacity and average coulombic efficiency (CE) of cells over 50 cycles show that cells aged with incorporated rest steps perform similarly to cells cycled without added rests. This similar average CE suggests that dead Li is largely responsible for drops in CE during rest rather than irreversible Li corrosion and that the dead Li can be reconnected in subsequent cycling. The addition of a lithiophilic ZnO coating to the Cu working electrode increases the adhesion and coverage of Li deposits at low pressures and improves CE during the first cycle.

First-principles study of Li adsorption and diffusion in naphyne

The Li adsorption and diffusion properties in naphyne are explored by first-principles calculations. The porous structure of naphyne facilitates the adsorption of Li atoms, and the adsorption performance of large pores is better than that of small pores. The average open circuit potential is 0.78 V and the maximum Li storage capacity of bulk naphyne is up to 620 mAh/g, much larger than the up limit of the popular graphite. Upon Li intercalation, the interlayer spacing dilatation of bulk naphyne is only 1.78 %, implying that naphyne would not undergo significant structural degradation during cycling. The average adsorption energy between Li and naphyne in LiC3.6 is −2.38 eV/Li, which is feasible to realize their free migration. The porous structure enables Li atoms to diffuse either parallel or perpendicular to the naphyne plane. About 0.41–0.70 eV barriers are needed to overcome for the three-dimensional Li diffusion. Compared to commercial graphite, the higher Li capacity, the smaller structural distortion, and the unique three-dimensional diffusion performance of Li atoms make naphyne a promising candidate as the anode material of LIB.

A novel two-dimensional whorled TiB4 as a high-performance anode material for Li-ion and Na-ion batteries

The search for high storage capacity anode materials has been an important topic in the field of ion batteries. With the gradual development of two-dimensional (2D) materials, their potential as high-performance electrode materials have been demonstrated. Here, using first principles calculations, we investigate the feasibility of novel 2D TiB4 as an ideal anode material for Li/Na ion batteries. Our results indicate that Li/Na ions can be chemically and stably adsorbed on the surface of 2D TiB4. It is noteworthy that the Li capacity of 2D TiB4 is up to 2353.2 mA h g−1 and the Na capacity up to 1764.9 mA h g−1 with a guaranteed low diffusion barrier (0.24 eV for Li; 0.09 eV for Na). Therefore, our calculations show that TiB4 monolayer is an excellent anode material with great potential for ultra-high energy storage devices.

Integrative design of laser-induced graphene array with lithiophilic MnOx nanoparticles enables superior lithium metal batteries

The practical applications of lithium metal batteries are limited by uncontrolled dendrite growth during cycling. Herein, we propose a simple and scalable approach to stabilize lithium metal anodes using laser scribing technology to integratively design and construct a laser-induced graphene (LIG) with lithiophilic metal oxide nanoparticles. The porous LIG and lithiophilic MnOx nanoparticles effectively reduce the nucleation overpotential of Li and regulate uniform Li plating, while the array structure offers continuous and ultra-fast ion/electron transport channels, accelerating Li+ transport kinetics at high rate and high capacity. Consequently, the Li@MnOx@LIG-a anode exhibits superior rate capability of up to 40 ​mA ​cm−2 with low nucleation overpotential. It also can withstand ultra-high Li capacity to 20 mAh cm−2 without dendrite growth and stably cycle for 3000 ​h with 100% depth of discharge at 40 ​mA ​cm−2. More importantly, this technology can be expanded to other metal oxides for various metal batteries.

Insight into the effects of S-vacancy and O-doping in monolayer VS2 as lithium-ion battery anodes from first-principles calculations

First-principles calculations are executed to probe the effects of S-vacancy and O-doping on the structure and electrochemical performances of monolayer VS2 as an anode material for lithium-ion batteries (LIBs). According to the defect formation energy, the formation of S-vacancy in monolayer VS2 is an endothermic reaction while the O-doping formation is an exothermic reaction. The difference in electronic structure arrangement near the defects results in varied adsorption energies of Li ions at the same site from that of pristine VS2. Two defects can significantly reduce the diffusion energy barrier of Li ions on the VS2 monolayer surface, 0.016 (for S-vacancy) and 0.117 eV (for O-doping), compared with pristine VS2 without defects (0.233 eV). In addition, these two defects are beneficial to the intercalation and de-intercalation of Li on the surface of VS2, so they can provide excellent rate performance for LIBs. All the Pristine, O-doped, and S-vacancy VS2 monolayers can stably adsorb the upper and lower Li layers, with theoretical capacities of 1397, 1419, and 1442 mAh/g, respectively. As a result of defect engineering, VS2 can become an ideal anode material for the LIBs due to its low diffusion barrier, high Li capacities, and high electrical conductivity.

Engineering Li Metal Anode for Garnet-Based Solid-State Batteries.

ConspectusThe past 30 years have witnessed the great achievements of Li-ion batteries (LIBs) based on a graphite anode and liquid organic electrolytes. Yet the limited energy density of a graphite anode and unavoidable safety risks caused by flammable liquid organic electrolytes hinder further developments of LIBs. To reach higher energy density, Li metal anodes (LMAs) with high capacity and low electrode potential are a promising choice. However, LMAs suffer from more serious safety concerns than the graphite anode in liquid LIBs. The dilemma of safety and energy density remains an inevitable obstacle in the way of LIBs.Solid-state batteries (SSBs) offer new opportunities to simultaneously achieve intrinsic safety and high energy density. Among all types of SSBs that are based on oxides, polymers, sulfides, or halides, garnet-type SSBs seem to be one of the most attractive choices due to garnet's merits in high ionic conductivities (10-4-10-3 S/cm at room temperature), wide electrochemical windows (0-6 V), and intrinsically high safety. However, garnet-type SSBs are faced with large interfacial impedance and short-circuit problems caused by Li dendrites. Recently, engineered Li metal anodes (ELMAs) have shown unique advantages in tackling interface issues and attracted extensive research interest.In this Account, we focus on fundamental understandings and provide an in-depth review of ELMAs in garnet-based SSBs. Considering the limited space, we mainly discuss the recent progress made in our groups. First, we introduce the design guidelines for ELMAs and emphasize the unique role of theoretical calculation in predicting and optimizing ELMAs. Then we discuss the interface compatibility of ELMAs with garnet SSEs in details. Specifically, we have demonstrated the advantages of ELMAs in enhancing interface contact and suppressing Li dendrite growth. Next, we attentively analyze the gaps between laboratory and practical applications. We strongly recommend establishing a unified testing standard, with a practically desired areal capacity per cycle (>3.0 mAh/cm2) and a precisely controlled Li capacity excess. Finally, novel chances to enhance ELMAs' processability and fabricate thin Li foils are highlighted. We believe that this Account will offer an insightful analysis of ELMAs' recent advancements and push forward their practical applications.

Vanadium and Niobium MXenes-Bilayered V2 O5 Asymmetric Supercapacitors.

MXenes offer high metallic conductivity and redox capacitance that are attractive for high-power, high-energy storage devices. However, they operate limitedly under high anodic potentials due to irreversibleoxidation. Pairing them with oxides to design asymmetric supercapacitors may expand the voltage window and increase the energy storage capabilities. Hydrated lithium preintercalated bilayered V2 O5 ( δ-Lix V2 O5 ·nH2 O) is attractive for aqueous energy storage due to its high Li capacity at high potentials; however, its poor cyclability remains a challenge. To overcome its limitations and achieve a wide voltage window and excellent cyclability, it is combined with V2 C and Nb4 C3 MXenes. Asymmetric supercapacitors employing lithium intercalated V2 C (Li-V2 C) or tetramethylammonium intercalated Nb4 C3 (TMA-Nb4 C3 ) MXenes as the negative electrode, and a δ-Lix V2 O5 ·nH2 O composite with carbon nanotubes as the positive electrode in 5m LiCl electrolyte operate over wide voltage windows of 2 and 1.6V, respectively. The latter shows remarkably high cyclability-capacitance retention of ≈95% after 10 000 cycles. This work highlights the importance of selecting appropriate MXenes to achieve a wide voltage window and a long cycle life in combination with oxide anodes to demonstrate the potential of MXenes beyond Ti3 C2 in energy storage.

Theoretical prediction on net boroxene as a promising Li/Na-ion batteries anode.

Novel two-dimensional (2D) electrode materials have become a new frontier for mining electrode materials for Li-ion batteries (LIBs) and Na-ion batteries (NIBs). Herein, based on first-principles calculations, we present a systematic study on the Li and Na storage behaviors in Calypso-predicted completely flat 2D boron oxide (l-B2O) with large mesh pores. We start our calculations from geometrical optimization, followed by a performance evaluation of Li/Na adsorption and migration processes. Finally, the specific capacity and average open-circuit voltage are evaluated. Our study reveals that l-B2O has good electrical conductivity before and after Li/Na adsorption and the Li/Na diffusion barrier height and average open-circuit voltage are both low, which is beneficial to the rate performance and full-cell operation voltage, respectively. Furthermore, it suffers a small lattice change (<1.7%), ensuring good cycling performance. In particular, we find that the Li and Na theoretical specific capacities of l-B2O can reach up to 1068.5 mA h g-1 and 712.3 mA h g-1, respectively, which are almost 2-3 times higher than graphite (372 mA h g-1). All the above outcomes indicate that 2D l-B2O is a promising anode material for LIBs and NIBs.

Thickness Dependency of Battery Anode Properties in Multilayer Graphene.

With the development of practical thin-film batteries, multilayer graphene (MLG) is being actively investigated as an anode material. Therefore, research on determining a technique to fabricate thick MLG on arbitrary substrates at low temperatures is essential. In this study, we formed an MLG with controlled thickness at low temperatures using a layer exchange (LE) technique and evaluated its anode properties. The LE technique enabled the formation of a uniform MLG with a wide range of thicknesses (25-500 nm) on Ta foil. The charge/discharge characterization using coin-type cells revealed that the total capacity, which corresponded to Li intercalation into the MLG interlayer, increased with increasing MLG thickness. In contrast, cross-sectional transmission electron microscopy showed a metal oxide formed at the MLG/Ta interface during annealing, which had small Li capacity. MLG with sufficient thickness (500 nm) exhibited an excellent Coulombic efficiency and capacity retention compared to bulk graphite formed at high temperatures. These results have led to the development of inexpensive and reliable rechargeable thin-film batteries.

(Invited) Garnet Solid Electrolytes for Advanced All-Solid-State Li Metal Batteries

These days, Li metal anode-based battery has been arisen as one of the key energy storage technologies due to its high theoretical energy density compared to conventional lithium and sodium ion-based batteries. The present Li-S batteries suffer due to Li dendrite formation and capacity decay due to polysulfide dissolution effect, because of organic electrolytes used in the current research. Solid state (ceramic) electrolytes are promising to prevent Li dendrite growth and polysulfide dissolution. Among different ceramic electrolytes garnet-type structure solid inorganic electrolytes are very promising because of its high lithium-ion conductivity and stability with elemental Li. However, the high interfacial resistance with the electrode is the major bottleneck for the practical use of ceramic electrolyte. Polymer and ceramic hybrid electrolytes exhibit low interfacial resistance. In this talk, we will present development of electrolytes for all-solid-state Li metal batteries.

(Invited) Lithium – Sulfur Batteries

These days, Li-S battery has been arisen as one of the key energy storage technologies due to its high theoretical energy density compared to conventional lithium and sodium ion-based batteries. The present Li-S batteries suffer due to Li dendrite formation and capacity decay due to polysulfide dissolution effect, due to organic electrolytes used in the current research. Solid state (ceramic) electrolytes are promising to prevent Li dendrite growth and polysulfide dissolution. Among different ceramic electrolytes garnet-type structure solid inorganic electrolytes are very promising because of its high lithium-ion conductivity and stability with elemental Li. However, the high interfacial resistance with the electrode is the major bottleneck for the practical use of ceramic electrolyte. Polymer and ceramic hybrid electrolytes exhibit low interfacial resistance. In this talk, we will present development of novel hybrid electrolytes for all-solid-state Li-S batteries, along with new methods to produce S cathodes with minimal polysulfide shuttle effect.

First-principles study on the electronic, magnetic, and Li-ion mobility properties of N-doped Ti2CO2

First-principles calculations have been used to investigate the electronic, magnetic and Li-ion mobility properties, and theoretical capacity of N-doped Ti2CO2 with the N contents from 5 at% to 20 at%. Three possible doping types were considered: lattice substitution for C, function substitution for O, and surface adsorption on O. Our results indicate that only C-substitution doping is feasible due to its thermodynamic and dynamical stability. Upon N doping, Ti2CO2 turns into metal from semiconductor, which ensures the good electronic conductivity. A non-magnetic (NM) → ferromagnetic (FM) transition also occurs at 10 at% N content. Most importantly, the calculated lowest Li diffusion barriers are 0.33, 0.31, 0.25, and 0.23 eV, for 0 at%, 5 at%, 10 at%, and 20 at% N contents, respectively. The lower diffusion barrier shows that N-doped Ti2CO2 has a faster Li transport than pristine one. The maximum Li capacity (378–383 mAh/g) of N-doped Ti2CO2 is higher than that of most MXenes, such as Ti3C2, Nb2C, and Mo2C. These remarkable improvements in electronic conductivity, Li diffusion and storage performance suggest that N-doped Ti2CO2 is a promising anode material for Li-ion batteries.

High‐Concentration Additive and Triiodide/Iodide Redox Couple Stabilize Lithium Metal Anode and Rejuvenate the Inactive Lithium in Carbonate‐Based Electrolyte

AbstractCarbonate‐based electrolytes are incompatible with lithium (Li) metal anode because the generated solid electrolyte interphase (SEI) undergoes repeated breakage‐repair, resulting in the accumulation of inactive Li including Li+ compounds and electrically isolated dead Li0 in the SEI. Therefore, exploiting a suitable strategy to construct a stable SEI while efficiently rejuvenating the inactive Li capacity is urgent and more thoughtful than just building a stereotyped SEI layer. Herein, an innovative strategy is proposed of high‐concentration additive (HCA) of LiNO3 inspired by (localized) high‐concentration electrolyte and inactive Li restoration methodology via triiodide/iodide (I3−/I−) redox couple to improve the compatibility of carbonate‐based electrolytes. The HCA of LiNO3 can maintain the cation–anion aggregates solvation structures in the carbonate‐based bulk electrolyte and induce the in situ formation of superior‐ionic‐conductivity NO3−‐derived SEI. Moreover, the reversible I3−/I− redox couple can further optimize the SEI and constantly rejuvenate the inactive Li including solvent/LiNO3‐derived Li2O, a derivative has almost been acquiescent in LiNO3‐additive electrolytes, and dead Li0 into delithiated cathode. Consequently, epitaxy‐like planar Li deposition, better reversibility, and higher capacity retention can be realized and are systematically verified by Li||Cu half cells, full cells with excess/limited Li (N/P ratio = 1.5) and anode‐free lithium metal batteries.