High-energy Lithium-ion Batteries Research Articles

Boosting the overall specific capacity of SiO electrodes for lithium-ion batteries using a multifunctional carbon cloth current collector

An approach of coating high-capacity active materials on current collectors with capacity-contributing ability is proposed to produce high-capacity electrodes.

Progress and perspectives on two-dimensional silicon anodes for lithium-ion batteries

Silicon (Si) anodes with extremely high theoretical capacities are considered indispensable for next-generation high-energy lithium-ion batteries (LIBs). However, several intractable problems, including pulverization, poor electrical contact, and continuous side reactions caused by the large volume change of Si during lithiation/delithiation, lead to a short cycle life and poor rate capability, thus hindering the commercial use of Si anodes in LIBs. Two-dimensional (2D) Si with a unique graphene-like structure has a short ion diffusion pathway, small volume change during lithiation, and efficient redox site utilization, making it more promising than bulk Si or Si with other versatile structures for use in LIBs. Theoretical analysis demonstrated that the low energy barrier on the surface of 2D Si accelerates the transport of Li + . However, the issues surrounding 2D Si, including the tedious and user-unfriendly synthesis, ease of restacking, and atmospheric sensitivity, limit its practical applications, which are discussed in this review. Furthermore, possible solutions to these remaining challenges and new directions are provided, with the aim of designing practical and high-performance 2D Si anodes for next-generation LIBs.

Constructing Lithium-Free Anode/Separator Interface via 3D Carbon Fabric Scaffold for Ultrasafe Lithium Metal Batteries.

Metallic lithium represents a promising anode candidate to be utilized in future high-energy lithium batteries. However, the undesirable dendrite growth and fragile solid-electrolyte interphase (SEI) pose critical challenge for pursuing further practical application. In contrast to traditional approaches of using inert/lithiophilicity coating, here, we demonstrate a reverse strategy of introducing a highly conductive and lithophobic carbon fabric (CF) scaffold on lithium foil to guide a favorable nucleation site of lithium far away from the anode/separator interface. The CF scaffold with high conductivity can couple with inner electric field for achieving a uniform distribution of the lithium-ion flux, while the lithophobic feature offers the condition to guide the preferred deposition of lithium onto the underlying lithium foil, which greatly reduces the risk of dendrite-induced short circuits. Moreover, the SEI immersed in the CF scaffold is well supported by CF fibers and therefore exhibits extremely high stability during charge-discharge cycles. As a result, the lithium/CF anodes show >2,000-h stable cycling at 0.5 mA cm-2. Lithium metal batteries equipped with our lithium/CF anode deliver a high capacity retention of ~99.99% per cycle, i.e., retain ~97.3% capacity after 200 cycles. The unique interface-regulation strategy is versatile for various conductive scaffolds (e.g., ultrathin and ultralight conductive fabrics), exhibiting high superiority for highly safe lithium metal batteries.

Multicore–shell iron fluoride@carbon microspheres as a long-life cathode for high-energy lithium batteries

Multicore–shell iron fluoride@carbon microspheres, synthesized using a bottom-up method, have a quality carbon coat and smaller core size. As a conversion cathode of lithium batteries, it exhibits notable stability over 3500 cycles at 1 C.

A comprehensive diffusion-induced stress coupled multiscale modeling and analysis in hard-carbon electrodes of Li-ion batteries.

Particle fracture due to diffusion-induced stress (DIS) in electrodes is a key factor for lithium-ion battery (LIB) failure. Among many ways to minimize DIS, optimization of particle size and C-rates using state of charge (SOC) dependent varying properties can be a noble approach. Herein, a comprehensive multiscale modeling approach has been proposed to optimize the particle size by studying the DIS in hard carbon (HC) particles as the potential anode materials for high-energy LIBs. To accomplish this, density functional theory (DFT) was used to calculate the SOC dependent coefficient of volume expansion (CVE). Similarly, SOC dependent diffusivity and elastic modulus are calculated via molecular dynamics (MD) simulations. These results are transferred to a continuum model to examine the evolution of concentrations and DISs in hard carbon particles of radius 100-1000 nm lithiated at various C-rates (1C, 2C, 5C, and 10C). Our model successfully incorporates the variation of Li+ diffusivity and elastic modulus with SOC and tracks stress relaxation and volume expansion in the particles during lithiation. An optimized particle size has been recommended for hard carbon, considering both stresses for different C-rates. Our study provides a more realistic multiscale modeling framework for optimizing the DIS and can act as a guiding method towards achieving an optimum particle size so that capacity fading due to cracking can be avoided.

Li2Se as cathode additive to prolong the next generation high energy lithium-ion batteries

The initial lithium loss caused by the formation of solid electrolyte interface (SEI) is a critical issue that reduces the energy density of lithium-ion batteries (LIBs). In order to offset the initial capacity loss, herein we propose lithium selenide (Li2Se) as an effective cathode prelithiation agent, which has a high “donor” Li-ion capacity, poor reversibility, relatively low delithiation potential and good compatibility to the existing cell fabrication processes. In a LiNi0.8Co0.1Mn0.1O2 (NCM)/ Si-C-Gr full cell, a high initial charge capacity of 250 mAh/g is obtained with 7% Li2Se additive, and the discharge capacity is 188.2 mAh/g (10.3 mAh/g higher than that of the pristine counterpart). The released capacity from Li2Se can offset the initial capacity loss during the SEI formation, confirmed by the enhanced discharged capacity. In addition, it can serve as a “lithium bank” to compensate the Li loss caused by the ongoing SEI breakage and reformation of Si-C-Gr anodes, leading to an improved cycling stability. The reversible capacity of the full cell with Li2Se prelithiation additives remains 152 mAh/g after 150 cycles at 0.3C, with an increase of 37.1% as compared to the counterpart without the additive. Li2Se is a promising cathode prelithiation agent especially for future advanced battery systems involving high specific capacity anodes with large initial irreversible capacity and poor cycling performance.

Scalable Direct Recycling of Cathode Black Mass from Spent Lithium‐Ion Batteries

AbstractEnd of life (EoL) lithium‐ion batteries (LIBs) are piling up at an intimidating rate, which is alarming for environmental health. With further expected rapid growth of LIB use, the magnitude of spent battery accumulation is also expected to grow. LiNixCoyMnzO2 (NCM) cathode materials are a dominant chemistry in high energy LIBs, and make up a huge portion of this waste accumulation. Direct recycling is one of the most promising ways to turn this waste to wealth, but has been limited to lab‐scale, due to lack of robustness, namely the tedious pretreatment required that involves toxic organic solvents. Herein, a process that integrates the pretreatment and relithiation of the cathode black mass is demonstrated. Cathode material from EoL electric vehicle (EV) batteries is treated in a 100 g per batch operation and the regenerated cathode active material demonstrates 100% electrochemical performance recovery, with 91% yield rate, and shows promise for further scale up. This process has the advantages of integration, scalability, and universality, which clears the barricade for direct recycling to move from lab to industry scale with considerable profitability.

A scalable silicon/graphite anode with high silicon content for high-energy lithium-ion batteries

High-capacity Si-based anodes are urgently needed for high-energy lithium-ion batteries in forthcoming electric vehicles and energy storage systems. However, it is still a challenge to prepare Si anodes with high Si content materials as well as good electrochemical performance because the accumulation and growth of Si lead to large volume expansion, pulverization and cycling degradation. Herein, we demonstrate feasibility of a high-capacity Si-based anode via a scalable and simple route using high Si content (31.6 wt%) Si/graphite composite, consisting of thin Si nanolayer and edge-sites-exposed graphite. This architecture effectively alleviates the volume changes of Si and facilitates lithium-ion transport. As a result, the Si/graphite composite delivers a reversible capacity of 1,080 mAh/g with an initial Coulombic efficiency of 86.3% and achieves outstanding cycling stability (94.3% capacity retention after 100 cycles). When combined with commercial graphite-blended systems for a 1.5 Ah pouch-type full-cell test under a high electrode density (1.6 g/cm3) and areal capacity (3.46 mAh/cm2), the composite demonstrates excellent cycling stability at 25 and 45 °C, respectively, and good high-rate performance. This strategy offers a practical feasibility of next-generation high-capacity anode for high-energy LIBs.

Atomic Horizons Interpretation on Enhancing Electrochemical Performance of Ni-Rich NCM Cathode via W Doping: Dual Improvements in Electronic and Ionic Conductivities from DFT Calculations and Experimental Confirmation.

The rapid capacity degradation and poor rate capability hinder the application of Rich-Ni layered LiNix Coy Mnz O2 (NCM) as cathode materials for high-energy lithium-ion batteries. In this study, density functional theory (DFT) calculations, combined with conventional electrochemical measurements, reveal from the atomic view that the dual improvements in electronic and ionic conductivities are the main facts for the property enhancement. The bandgap of the cathode material is reduced to 1.1623eV due to the increased number of electrons near the Fermi level after W intercalation. Such improved electronic conductivity subsequently leads to a suppressed polarization and reduced resistance, enabling an improved cycle life of up to 93.97% after 100 cycles at 0.5 C. Furthermore, the doping with W6+ also introduced a strong WO bond into the layered structure so that the thickness of the Li slab is expanded to 2.6476 Å, which reduces the energy barrier from 0.355 to 0.308eV for the migration of Li+ within the Li slab, as confirmed by the DFT calculation. Consequently, the rate performance is greatly improved due to the reduced diffusion energy, with a specific capacity of 159.11 mAg-1 even at 5 C rate, indicating high potential for future applications.

In situ mitigating cation mixing of Ni-rich cathode at high voltage via Li2MnO3 injection

Ni-rich layered oxides (LiNixCoyMnzO2, x ≥ 0.8) have been under intense investigation as cathode materials for high-energy rechargeable lithium ion batteries (LIBs) due to their high capacity and relatively low cost. However, Ni/Li cation mixing, in most cases, brings about capacity degradation, structure evolution and poor thermal stability, especially at high cut-off voltage. Herein, a universal strategy with novel mechanism-in situ mitigating cation mixing at 4.55 V via injecting Li2MnO3 has been achieved (label as LD-NCM811), significantly improving the electrochemical property, structural integrity and thermal stability of Ni-rich cathode materials compared with the conventional NCM811. LD-NCM811 maintains a high capacity retention of 93% at 0.3 C after 200 cycles at 25 °C with negligible voltage decay of 40 mV, whereas the NCM811 shows a retention of 68% and large voltage decay of 248 mV, and the corresponding cation mixing has been mitigated from 13.5% to 7.5%. At the temperature of 45 °C, LD-NCM811 still keeps a considerable capacity retention of 93% at 1 C, significantly superior to the NCM811 with 75%. Characterization and calculation reveal that the excellent performances result from the Li2MnO3 phase with unique superlattice providing lithium voids in transition metal (TM) oxide layers when it is charged above 4.5 V, which is favorable for the mixed Ni ions migrating back to TM layers instead of blocking the lithium channel. This new finding establishes a general strategy for mitigating cation mixing of NCM811 to realize its application in high energy density and safety batteries.

Ultrahigh areal capacity silicon anodes realized via manipulating electrode structure

High areal capacity is critical towards the practical application of silicon anodes for high-energy lithium ion batteries. Herein, a free-standing silicon-graphene (3D-Si/G) anode with ultrahigh areal capacity is proposed by manipulating electrode structure using 3D-printing. For the 3D-Si/G electrodes with the circle-grid pattern, electrode thickness and printed filament spacing can be precisely constructed and adjusted by controlling a computer program. In this configuration, the tailored free space between and inside the filaments are enough to withstand volume fluctuation of silicon anodes, which significantly improves the structure stability and integrity of electrodes and endows the great accessibility to lithium ions transport in thick electrodes. Furthermore, the unique edge-coaxial and internal-disordered structure in printed filaments greatly enhances the electrode mechanical stability. Simultaneously, the graphene framework with excellent electron-ion transport characteristic ensures fast electrochemical reaction kinetics and low electrochemical polarization in thick electrodes. Therefore, the optimized 3D-Si/G electrode achieves a favorable cycle stability with 8.5 mAh cm −2 after 70 cycles (capacity retention of 75.4%). And the 3D-Si/G thick electrode with four layers achieves a reversible ultrahigh areal capacity of 16.2 mAh cm −2 . More importantly, the easy ink preparation and controllable printing process provide broad prospects for the commercial application of silicon anodes.

The pursuit of commercial silicon-based microparticle anodes for advanced lithium-ion batteries: A review

Silicon (Si) is one of the most promising anode materials for high-energy lithium-ion batteries. However, the widespread application of Si-based anodes is inhibited by large volume change, unstable solid electrolyte interphase, and poor electrical conductivity. During the past decade, significant efforts have been made to overcome these major challenges toward industrial applications. This review summarizes the recent development of microscale Si-based electrodes fabricated by Si microparticles or other industrial bulk materials from the perspective of industrialization. First, the challenges for microscale Si anodes are clarified. Second, structural design strategies of stable micro-sized Si materials are discussed. Third, other critical practical metrics, such as robust binder construction and electrolyte design, are also highlighted. Finally, future trends and perspectives on the commercialization of Si-based anodes are provided.

Investigation on high-energy Si anode mechanical-electrochemical-thermal characteristic under wide temperature range

Studying the cyclic evolution of high-energy Si anode, including the mechanical deformation, voltage hysteresis, heat generation and temperature response, is of great significance for its performance and safety. In this paper, a novel coupled semi-analytical model is developed to investigate the mechanical-electrochemical-thermal characteristic of Si particle anode. This model is adopted a series of temperature and concentration dependent parameters related to electrochemical reaction and Li+ diffusion. The results show that Li+ diffusion process will be limited at a lower initial temperature, which may increase the elastic–plastic stress. Thus, the stress-induced voltage hysteresis is more evident, resulting in the capacity loss and polarization heat increase. In the aspect of thermal behavior, the heat generation during lithiation is more than that during delithiation at each initial temperature, and the total heat accumulation after one cycle is greater at a higher initial temperature. Besides, the asymmetrical elastic–plastic deformation and heat accumulation during cyclic lithiation/delithiation may lead to ratcheting deformation of the Si particle electrode. The ratcheting deformation will be aggravated at a lower temperature. Additionally, the effects of charging rates (0.2C, 0.5C and 1C) are also discussed. The increased charging rate leads to a steeper concentration gradient, the more obvious asymmetrical elastic–plastic deformation, and earlier reaching the cut-off voltage. The electrode will produce more heat in a short time in the case of fast charging, and the resulting self-heating accumulation will affect its thermal stability. Based on this, ratcheting deformation at a fast charging rate is more severe, which will further decrease the mechanical stability of the Si electrode. The theoretical results are verified by the experiments. This study provides a theoretical and experimental basis for understanding the comprehensive performance of high-energy lithium-ion batteries, as well as design and management guidance.

Ta Doping Improves the Cyclability and Rate Performance of a Nickel-Rich NCA Cathode via Promoted Electronic and Cationic Conductivity

NCA layered cathode materials are characterized by low cost and high reversible specific capacity compared with olivine and spinel cathodes. However, the high Ni content also leads to poor cyclability. In this paper, other than the mechanism reported by another group, we proposed the increase in electronic and cationic conductivity of Ta-doped LiNi0.94Co0.04Al0.02O2 cathode material could be the other reason for the promoted electrochemical behavior. DFT calculation revealed that the increased amount of electrons near Fermi energy which reduces the bandgap (from 1.2953 eV to 1.2171 eV) of Ta-NCA can be ascribed to the enhanced electronic conductivity. Such improvement later leads to reduced polarization and therefore the cyclability of the half cell is increased. Meanwhile, the suppressed H2–H3 phase transition, is also found to be responsible for the promoted cyclic performance. For the Ta-NCA cathode, the capacity retention after 100 cycles is promoted from 42.11% to 93.62% (from 81.16 mAh·g–1 to 181.54 mAh·g–1). Ta doping also increases the Li diffusion coefficient due to the expanded interplanar spacing of the Li slab. For Ta-NCA cathode with a promoted diffusion coefficient of 3.11 × 10–11 cm2·s–1, the specific capacity at 5C is increased from 118.51 mAh·g–1 to 158.47 mAh·g–1. Both the increase in cyclability and rate behavior indicate the high potential of the Ta-NCA cathode material in high-energy lithium-ion batteries.

Unraveling the degradation mechanism of LiNi0.8Co0.1Mn0.1O2 at the high cut-off voltage for lithium ion batteries

LiNi0.8Co0.1Mn0.1O2 (NCM811) layered oxides have been regarded as promising alternative cathodes for the next generation of high-energy lithium ion batteries (LIBs) due to high discharge capacities and energy densities at high operation voltage. However, the capacity fading under high operation voltage still restricts the practical application. Herein, thecapacity degradationmechanismof NCM811 at atomic-scale isstudied in detail under various cut-off voltages using aberration-corrected scanning transmission electron microscopy (STEM).It is observed that the crystal structure of NCM811 evolution from a layered structure to a rock-salt phase is directly accompanied by serious intergranular cracks under 4.9 V, which is distinguished from the generally accepted structure evolution of layered, disordered layered, defect rock salt and rock salt phases, also observed under 4.3 and 4.7 V. The electron energy loss spectroscopy analysis also confirms the reduction of Ni and Co from the surface to the bulk, not the previously reported only Li/Ni interlayer mixing. The degradation mechanism of NCM811 at a high cut-off voltage of 4.9 V is attributed to the formation of intergranular cracks induced by defects, the direct formation of the rock salt phase, and the accompanied reduction of Ni2+ and Co2+ phases from the surface to the bulk.

Mo2C catalyzed low-voltage prelithiation using nano-Li2C2O4 for high-energy lithium-ion batteries

Irreversible lithium loss in the initial cycles appreciably reduces the energy density of lithium-ion batteries. Prelithiation is an effective way to compensate for such lithium loss, but current methods suffer from either the instability or low capacity of prelithiation reagents. Lithium oxalate (Li2C2O4) has shown great potential as a lithium-compensation material because of its high theoretical capacity (equivalent to lithium metal), low cost, and air stability. However, the practical applications of Li2C2O4 are limited by its low electrochemical activity and high critical decomposition voltage. In this study, we performed the prelithiation of a low-voltage cathode by using Mo2C catalysis and nano-Li2C2O4. Results show that the Mo2C catalyst changes the electron cloud distribution around Li2C2O4 and greatly reduces the activation energy, thereby significantly accelerating the lithium release from Li2C2O4. The nano-Li2C2O4 prepared by freeze-drying shows accelerated ionic and electronic conduction as well as close contact with Mo2C. Benefiting from the synergistic effect, the decomposition potential of Li2C2O4 is decreased by 0.5 V with an efficiency close to 100%. The LiCoO2∥SiO full cell empowered with the nano-Li2C2O4/Mo2C prelithiation composite demonstrates 46.9% higher capacity than the control and thus has great potential for practical applications.

Flexible and ultralight MXene paper as a current collector for microsized porous silicon anode in high-energy lithium-ion batteries

Silicon (Si) is a new candidate anode material for lithium-ion batteries. The porous treatment of Si anode has been proved to be effective. In order to improve the interface performance and energy density of batteries, we start from the current collector (CC) and make further improvements. Combined with the advantages of new two-dimensional material MXene in electrochemical aspects, we make MXene replace the traditional Cu foil as CC of Si anode. The prepared MXene paper is both flexible and lightweight. After coating the Si slurry on it, the assembled half cells and 5 V-class full cells can achieve normal lithium-ion intercalation and deintercalation. Moreover, compared with the battery using Cu current collector, the volume expansion of porous silicon in the battery with MXene is further alleviated, and the cycle stability performance is also improved.

Stabilizing structure and voltage decay of lithium-rich cathode materials

A major challenge in the discovery of high-energy lithium-ion batteries (LIBs) is to control the voltage stability and Li+ kinetics in lithium-rich layered oxide (LrLO) cathode materials. Although these materials can provide a higher specific capacity compared to the current industrially used cathodes, the substantial voltage decay and low Li+ diffusion during long term cycling is a serious reason for hindering their practical applications. In order to suppress the voltage decay in lithium-rich cathode materials, herein we introduce the Ti doping into Li1.2Mn0.56Ni0.17Co0.07O2 cathodes. Also, the influence of Ti doping on the crystalline internal structure, surface chemistry, cycling retention, and Li+ kinetics of Li1.2Mn0.56Ni0.17Co0.07O2 cathodes have been focused in this work. The Ti doping effectively enhances the structural/interfacial stability of the cathode and accelerates the Li+ kinetics by expanding the lattice, thereby significantly realizing its voltage/cycling stability and high-rate capability. Experimental results show that Ti-doped LrLO (1% Ti) has achieved high electrochemical kinetics as the discharge cycle retention increased from 61.58% (pristine) to 80.0% after 180 cycles at 1 C, with 150.3 mAh g−1 showing superior high-rate performance at 5C. Ex-situ XRD results confirmed the better structural stability of Ti-doped LrLO after high-rate electrochemical cycling. Our findings provide a suitable element doping strategy for regulating the voltage decay and cycle retention of LrLO, thus promoting their real-world application in future batteries.

Rapid Self-Healing Gel Electrolyte Based on Deep Eutectic Solvents for Solid-State Lithium Batteries.

A deep eutectic solvent (DES) is a promising electrolyte choice for lithium metal batteries. However, the DES liquid electrolyte causes safety concerns and side reactions with the lithium anode. Therefore, it is necessary to solidify the DES-based electrolyte and enhance its electrochemical stability. Herein, we present a novel DES-based rapid self-healing gel electrolyte, which is able to self-smooth its surface cracks in only 30 min. The electrolyte exhibits noncombustibility (SET = 4 s g-1), high ionic conductivity (1.1 × 10-3 S cm-1 at 25 °C), and a wide electrochemical voltage window (4.5 V vs Li/Li+). As a result, the solid-state lithium batteries coupling the gel electrolyte with the Li anode and LiFePO4 cathode deliver a high specific capacity of 135.4 mA h g-1 with durable cyclic stability (>1200 h). This work provides valuable insights for design of fire-resistant and high-energy solid-state lithium batteries.

Towards fast-charging high-energy lithium-ion batteries: From nano- to micro-structuring perspectives

Electric vehicles (EVs) have been playing an indispensable role in reducing greenhouse gas emissions for our modern society. However, current EVs are difficult to meet people’s diverse travel needs, especially in long endurance and fast-charging capacities. At the heart of this issue is the physicochemical limit of current lithium-ion batteries (LIBs), which are the core parts for powering the vehicles. Hence, LIBs with simultaneous high energy and power are critically required to further promote the development of EVs. In this review, we first summarize the key electrochemical processes in electrochemical reactions which lead to the corresponding overpotentials in or between multiple battery components. Furthermore, numerical simulations are employed to quantitatively analyze the effects of versatile electrode parameters on electrochemical properties in high-energy NMC811//graphite systems. On the basis of the in-depth understandings from simulation, recent experimental efforts on designing electroactive materials and electrode architectures across multiple length scales are discussed. Among them, nano-structuring can promote local mass transport and stabilize the interfaces at the particle level, while micro-structuring can establish efficient pathways for charge carriers at the electrode level. Finally, we conclude that a tight feedback loop among structure engineering, characterization and simulation should be followed to speed up the understanding of the deficiencies existing in current electrode designs as well as point out the possible electrode optimization routes for next-generation fast-charging LIBs.