High-energy Lithium-ion Batteries Research Articles

Densification of Alloying Anodes for High Energy Lithium-Ion Batteries: Critical Perspective on Inter- Versus Intra-Particle Porosity.

High Li-storage-capacity particles such as alloying-based anodes (Si, Sn, Ge, etc.) are core components for next-generation Li-ion batteries (LIBs) but are crippled by their intrinsic volume expansion issues. While pore pre-plantation represents a mainstream solution, seldom do this strategy fully satisfy the requirements in practical LIBs. One prominent issue is that porous particles reduce electrode density and negate volumetric performance (WhL-1) despite aggressive electrode densification strategies. Moreover, the additional liquid electrolyte dosage resulting from porosity increase is rarely noticed, which has a significant negative impact on cell gravimetric energy density (Whkg-1). Here, the concept of judicious porosity control is introduced to recalibrate existing particle design principles in order to concurrently boost gravimetric and volumetric performance, while also maintaining the battery's cycle life. The critical is emphasized but often neglected role that intraparticle pores play in dictating battery performance, and also highlight the superiority of closed pores over the open pores that are more commonly referred to in the literature. While the analysis and case studies focus on silicon-carbon composites, the overall conclusions apply to the broad class of alloying anode chemistries.

Enabling stable high lithium storage of Si anode via synergistic effects of nanosized Fe3C and partially graphitized porous carbon

Si is considered as a promising anode for high-energy lithium-ion batteries (LIBs) because of its ultrahigh theoretical specific capacity and desired working potential. However, the main problems of Si as an anode are still faced with low conductivity and inevitable structure damage caused by large volume change during cycle. Although design of Si/C composites effectively mitigates the above problems, their preparation usually involves complex methods. This work demonstrates a very simple ball milling and subsequent carbonization approach for the preparation of high-performance Si NPs@Fe3C@PC anode, which integrates partially hollow Fe3C nanoparticles (Fe3C) and partially graphitized porous carbon (PC) into Si nanoparticles (Si NPs)-based composite. It is found that Fe3C with catalysis is favorable not only to formation of a graphitized porous carbon during material preparation but also to formation of a stable solid electrolyte interfaces (SEI) on electrode surface during cycle. With Fe3C, the Si NPs@Fe3C@PC shows smaller Li+ adsorption energy, lower activation energy, higher electric conductivity, larger Li+ diffusion coefficient and a thinner SEI film than Si NPs and Si NPs@PC counterparts. The findings verify that the synergistic effects of the Fe3C and PC provide fast kinetics, high capacitive contribution, improved structure stability and a stable LiF-rich SEI film for Si NPs@Fe3C@PC during cycle. Therefore, Si NPs@Fe3C@PC shows excellent electrochemical performance, gaining 1786, 1211.4 and 411.5 mAh/g after 210, 650 and 840 cycles at 100, 1000 and 5000 mA g−1, respectively. Finally, this contribution proposes a simple and effective strategy for improving Si NPs performance and hence obtaining a high-performance of Si-based anode for LIBs.

Comprehensive aging model coupling chemical and mechanical degradation mechanisms for NCM/C6-Si lithium-ion batteries

The aging of lithium-ion batteries (LIBs) is synergistically influenced by multiple chemical/mechanical degradation mechanisms. Therefore, conventional models that incorporate only partial mechanisms exhibit limited predictive accuracy and applicability, failing to fully reflect the effects of chemical/mechanical degradation under complex operating conditions. Here, we propose an aging model for NCM/C6-Si LIBs coupled with comprehensive chemical/mechanical degradation mechanisms. The model includes chemical mechanisms at the C6-Si anode solid electrolyte interface (SEI), Li plating, and NCM cathode electrolyte interface (CEI), as well as mechanical mechanisms of loss of active material (LAM) for C6, Si, and NCM. Based on this model, we comprehensively investigate the effect of capacity loss by (dis)charge rates and ambient temperatures, obtaining the aging characteristics and the contribution of each mechanism to loss under different variables. Furthermore, we quantitatively analyze the sensitivity and response characteristics of the degradation sub-mechanism to (dis)charge rate and temperature. This study introduces an advanced aging analysis model for NCM/C6-Si LIBs, which can effectively decouple the operational characteristics of the degradation mechanism and provide guidance for developing next-generation high-energy LIBs.

Enabling stable high lithium storage of Si anode via synergistic effects of nanosized Fe3C and partially graphitized porous carbon

Si is considered as a promising anode for high-energy lithium-ion batteries (LIBs) because of its ultrahigh theoretical specific capacity and desired working potential. However, the main problems of Si as an anode are still faced with low conductivity and inevitable structure damage caused by large volume change during cycle. Although design of Si/C composites effectively mitigates the above problems, their preparation usually involves complex methods. This work demonstrates a very simple ball milling and subsequent carbonization approach for the preparation of high-performance Si NPs@Fe3C@PC anode, which integrates partially hollow Fe3C nanoparticles (Fe3C) and partially graphitized porous carbon (PC) into Si nanoparticles (Si NPs)-based composite. It is found that Fe3C with catalysis is favorable not only to formation of a graphitized porous carbon during material preparation but also to formation of a stable solid electrolyte interfaces (SEI) on electrode surface during cycle. With Fe3C, the Si NPs@Fe3C@PC shows smaller Li+ adsorption energy, lower activation energy, higher electric conductivity, larger Li+ diffusion coefficient and a thinner SEI film than Si NPs and Si NPs@PC counterparts. The findings verify that the synergistic effects of the Fe3C and PC provide fast kinetics, high capacitive contribution, improved structure stability and a stable LiF-rich SEI film for Si NPs@Fe3C@PC during cycle. Therefore, Si NPs@Fe3C@PC shows excellent electrochemical performance, gaining 1786, 1211.4 and 411.5 mAh/g after 210, 650 and 840 cycles at 100, 1000 and 5000 mA g−1, respectively. Finally, this contribution proposes a simple and effective strategy for improving Si NPs performance and hence obtaining a high-performance of Si-based anode for LIBs.

Monolithic Layered Silicon Composed of a Crystalline-Amorphous Network for Sustainable Lithium-Ion Battery Anodes.

While nanostructural engineering holds promise for improving the stability of high-capacity silicon (Si) anodes in lithium-ion batteries (LIBs), challenges like complex synthesis and the high cost of nano-Si impede its commercial application. In this study, we present a local reduction technique to synthesize micron-scale monolithic layered Si (10-20 μm) with a high tap density of 0.9-1.0 g cm-3 from cost-effective montmorillonite, a natural layered silicate mineral. The created mesoporous structure within each layer, combined with the void spaces between interlayers, effectively mitigates both lateral and vertical expansion throughout repeated lithiation/delithiation cycles. Furthermore, the remaining SiO2 network fortifies the layered structure, preventing it from collapsing during cycling. Half-cell tests reveal a capacity retention of 92% with a reversible capacity of 1130 mAh g-1 over 500 cycles. Moreover, the pouch cell integrated with this Si anode (with a mass loading of 3.0 mg cm-2) and a commercial NCM811 cathode delivers a high energy density of 655 Wh kg-1 (based on the total mass of the cathode and anode) and maintains 82% capacity after 200 cycles. This work demonstrates a cost-efficient and scalable strategy to manufacture high-performance micron Si anodes for the ever-growing demand for high-energy LIBs.

Lanthanum doping and surface Li3BO3 passivating layer enabling 4.8 V nickel-rich layered oxide cathodes toward high energy lithium-ion batteries

Single crystalline Ni-rich layered oxide cathodes show high energy density and low cost, have been regarded as one of the most promising candidates for next generation lithium-ion batteries (LIBs). Extending the cycling voltage window will significantly improve the energy density, however, suffers from bulk structural and interfacial chemistry degradation, leading to rapidly cycle performance deterioration. Here, we propose a dual-modification strategy to synthesize La doping and Li3BO3 (LBO) coating layers modified LiNi0.8Co0.1Mn0.1O2 (NCM811) by a facile one-step heating treatment processing. In-situ EIS and XRD, ex-situ XPS techniques are applied to demonstrate that the La diffused amorphous domains and Li3BO3 passivating layers dampen the lattice distortion, enhance the interfacial chemistry behavior as well as lithium ion transportation kinetics. Specifically, surface La doping amorphous domains successfully suppress the intense lattice stress and volume changes induced by the phase transitions during lithiation/delithiation, thus avoiding the intergranular crack and enhancing the mechanical stability of the material. Moreover, the LBO layer formed by the consumption of residual lithium prevents successive parasitic reactions at the interface as well as provides rapid Li-ion diffusion channels. Furthermore, the coating layer also diminishes the residual lithium compounds, increasing the atmosphere stability and safety of LIBs. Consequently, the La doping and LBO coating NCM811 exhibits an exceptional initial specific capacity (230.6 mAh/g) at 0.5C under a high cutoff voltage of 4.8 V, and a 73.8 % capacity retention following 100 cycles. In addition, a superior specific capacity of 133.8 mAh/g is provided even at a high current density (4C). Our work paves a promising road to tackle the integral structure deterioration and interfacial instability of Ni-rich cathodes.

A synergistic duo for enhanced cathode stability in high-voltage lithium-ion batteries

Lithium-ion batteries with high-nickel cathode materials are promising candidates for achieving significantly higher energy densities. However, when Ni-rich subjected to higher charging cutoff voltages accelerates both electrolyte decomposition and structural degradation, leading to compromised cycling stability and reduced lifespan. In this study, we have developed a dual-additive strategy using lithium difluoro bisoxalate phosphate (LiDFBOP), and 1,3-divinyl-1,1,3,3-tetramethyldisilazane (DTDS) to address these challenges and improve the battery's performance. Theoretical calculations and experimental results indicate that the LiDFBOP regulates Li⁺ solvation for robust CEI formation, while DTDS scavenges impurities and promotes the formation of an inorganic/organic interphase. The synergistic effect of these additives combination allows Li||NCM811 coin cell to retain a capacity retention 87.9 % at 4.6 V and Graphite||NCM811full cell achieved 90.5 % capacity retention at 4.5 V. Moreover, the 1Ah pouch full cells exhibit excellent cycling stability, with a capacity retention of 91.4 % after 610 cycles at a constant current of 500 mA and voltage of 4.5 V. This work offers guidance on designing multifunctional additives to achieve synergistic electrolyte engineering for high-energy lithium-ion batteries.

The high-fluorinated bi-molecular combination enables high-energy lithium batteries under challenging environment

The drawbacks of temperature sensitivity, high voltage intolerance, and flammability of lithium batteries are gradually brought to light in conventional carbonate electrolytes. To solve these problems, a localized high concentration electrolyte (LHCE) employing highly fluorinated ethyl trifluoroacetate (TFAE) and 2,2,3,3-tetrafluoro-1-(1,1,2,2-tetrafluoroethoxy) propane (TFEP) is designed. When applied in high-energy lithium batteries, the discharge specific capacity of Li||NMC811 battery can maintain 143.6 mAh/g after 500 cycles at 4.6 V and 1C, and the capacity retention of Li||LNMO battery retains as high as 89.99 % after 500 cycles at 5 V. In addition, this LHCE also possesses the ability to operate the battery under challenging conditions including low temperature, fast charge, safety risks, etc. The LHCE based on TFAE and TFEP has unique solvated structures to generate a moderate LiF-rich interfacial layer, ensuring the fast Li+ migration. This work will provide strong guidance for future electrolyte industrial design of high-energy lithium battery.

Precycling Strategy in Suitable Voltage to Improve the Stability of Interfacial Film and Suppress the Decline of LiNi0.6Mn0.2Co0.2O2 Cathode at Elevated Temperatures.

Layered ternary oxide LiNixMnyCo1-x-yO2 is a promising cathode candidate for high-energy lithium-ion batteries (LIBs). However, the capacity of LIBs is significantly restricted by several factors, including the repeated dissolution-regeneration of the interfacial film at high temperatures, the dissolution of transition metals, and the increase of impedance. Herein, a new precycling strategy in suitable voltage scope at room temperature is proposed to construct a uniform, thermally stable, and insoluble cathode-electrolyte interface (CEI), which helps to maintain stable cycling performances at high temperatures. Specifically, after 5 precycles in the range of 3.85-4.3 V at room temperature, a CEI layer containing numerous inorganic components and oligomers is formed on the surface of LiNi0.6Mn0.2Co0.2O2. Subsequently, the harmful side reactions are effectively suppressed, endowing the cell with an excellent capacity retention of 84.67% after 50 cycles at 0.5C and 55 °C, much higher than that of 65.61% under the conventional film-forming process conditions. This work emphasizes the crucial role of the precycling strategy in regulating the characteristics of CEI layer on the surface of cathode electrode, opening up a new avenue for the high-temperature application of positive electrodes of LIBs.

Mathematical Model for a Lithium-Ion Battery with a SiO/Graphite Blended Electrode Based on a Reduced Order Model Derived Using Perturbation Theory

Silicon oxide (SiO) is a promising anode material for high-energy lithium-ion batteries, as it is made from low-cost precursors, has a potential close to that of Li, and has high theoretical specific capacity. However, the applications of SiO are limited by the intrinsic low electrical conductivity, large volume change, and low coulombic efficiency, which often lead to poor cycling performance. A common strategy to address these shortcomings is to blend SiO with graphite active materials to form a composite anode for better capacity retention. In this work, we derive a reduced order model (ROM1) using perturbation theory. We employ the multi-site, multi-reaction (MSMR) framework of a composite porous electrode blend consisting of two lithium-host materials, SiO and graphite. The ROM1 model employs a single-particle model (SPM) approach as the leading-order solution and involves the numerical analysis of a single, nonlinear partial differential equation for each host material that describes diffusion by means of irreversible thermodynamics, wherein chemical-potential gradients are the driving forces for the diffusion. The first-order correction treats losses other than that of the SPM.

Quenching-Induced Ultrathin LiF-Rich Interphases on LiNi0.8Co0.1Mn0.1O2 Cathode

Nickel-rich layered oxides (NCM) are a promising contender material for the cathode electrode of high-energy lithium-ion batteries (LIBs) due to their large reversible capacity and high operating voltage. However, the poor surface/interfacial stability and the dissolution of transition metal ions hinder the commercial application of NCM. To create an artificial cathode electrolyte interphase (CEI) with LiF-rich inorganic phase on the NCM surface, a practical and efficient way of quenching the NCM powder from high temperature in 1,1,2,2-Tetrafluoroethyl 2,2,2-trifluoroethyl ether (HFE) was devised. With this artificial CEI film, the side reactions between NCM and electrolytes are inhibited, and the dissolution of TM ions is retarded. The quenched-NCM achieved fantastic cycling performance and suppressed voltage decay. Our research offers an efficient and worthy approach for improving the surface/interfacial stabilization of nickel-rich cathode materials for high-energy-density LIBs.

Remarkably improved cycling stability of commercial micron-sized silicon enabled by a novel organic/inorganic hybrid binder

Silicon (Si) anode with ultra-high capacity and low cost are highly desirable for next-generation high-energy lithium-ion batteries, whereas suffers from severe volume change that causes rapid capacity decay upon lithiation/delithiation. The development of high-performance binders to alleviate volumetric expansion and maintain integrity of Si particles remains a significant challenge. Here, reported is a novel organic/inorganic hybrid binder composed of partial neutralized polyacrylic acid (PAAS) and sodium metaborate tetrahydrate (SMTH), which achieves in-situ crosslinking upon drying wafer electrodes. The robust crosslinked network structure with borate ester bonds is successfully attained, and can be modulated by changing the content of sodium metaborate. The strong covalent bond network endows the hybrid binder system with superior mechanical properties and powerful adhesion, which improve the contact and integrity of wafer silicon electrode by suppressing volume expansion and exfoliation, therefore facilitating Li-ion migration and enhancing electrochemical performance. The resulting commercial micro-silicon wafer electrode with PAAS/0.08SMTH binder remains a reversible specific capacity of 1670 mAh g−1 after 150 cycles at 300 mA g−1, largely superior to that prepared with the original PAAS binder because its reversible specific capacity was determined to be only 1046 mAh g−1 under identical conditions. The in-situ crosslinked 3D network structure provides a facile feasible way to improve the high-capacity anode materials for lithium-ion batteries.

Constructing adaptive silicon–carbon interconnected network for high-energy lithium-ion batteries

Nano-silicon (n-Si)/graphite anodes are highly desirable for high-energy lithium-ion batteries. Nevertheless, the high surface energy of n-Si grains is prone to causing serious agglomeration. In this work, the modified n-Si is evenly dispersed on the g-C3N4 carbon mesh that acquired through melamine heat treatment constructing an adaptive Si-carbon interconnection network structure (mSi50/g-C3N4). Ideally, the mSi50/g-C3N4 composite can be well dispersed and fill the gaps in graphite through traditional ball milling processes. The obtained mSi50/g-C3N4/Gr composite prevents the accumulation of Si grains which is beneficial for expediting ion transport, improving conductivity and structural stability. As a result, this anode provides a reversible capacity of 621 mAh⋅g−1 at 0.2 C, with high-capacity retention of 93.3 % after 300 cycles at 1 C and low volume expansion of only 28.6 %. Furthermore, it also maintains excellent cycling stability in full batteries with LiFePO4 cathode. Therefore, constructing the mSi50/g-C3N4 network is an effective strategy to achieve uniform dispersion of Si in graphite and promote larger scale industrialization of n-Si/graphite anode.

Rest in phase transition: Should charging habits in next generation EVs be adapted?

Nickel-rich cathode materials are a popular cathode for high energy lithium ion batteries in the current and next generation of electric vehicles. While nickel-rich cathodes offer high energy density, their cycle-life is compromised due to several factors directly related to their (de)lithiation behavior. At high state of charge the nickel-rich cathode experiences a hexagonal-hexagonal transition which is accompanied by drastic changes in the unit cell parameters. This phenomenon is detrimental for cycle-life of a battery cell. This work elucidates on the effect of storing LiNi0.8Mn0.1Co0.1O2‖Graphite cells at 95 % state of charge corresponding to the above-mentioned transition for 10 h every six cycles. The results are compared to cells cycled without a rest at high state of charge and cells cycled to 100 % state of charge. Analysis of the obtained cycling data shows that resting lithium ion cells based nickel-rich cathode based cells is detrimental leading to higher impedance growth and capacity decay than cycling to 100 % state of charge.

Complex reaction mechanisms of electrolyte decomposition at large-scale Ni-rich Li-ion battery cells including electrode crosstalk effect

Ni-rich cathodes are essential for the advancement of high-energy lithium-ion batteries but encounter significant challenges at elevated voltages, including oxygen liberation and enhanced surface reactivity, which precipitate electrolyte decomposition. This study explores the intricate reaction mechanisms of electrolyte decomposition linked to the pronounced release of oxygen from the cathode lattice in large-scale 18650 cylindrical cells employing Ni-rich LiNi0.90Mn0.05Co0.05O2(NMC90)//graphite configurations, focusing on electrode crosstalk effects at high voltages. Notably, acetals such as methoxy methanol (49.93 %) and methane diol (50.07 %) were identified at 4.7 V, with their presence escalating at 4.9 V. Formaldehyde, present at 7.21 %, along with methanol (22.77 %), methane diol (36.35 %), and methoxy methanol (33.67 %), begins to manifest at 4.9 V. The dissolution of transition metals was analyzed using Inductively Coupled Plasma Atomic Emission Spectrometry, and changes in the double-layer capacitance were assessed through electrochemical impedance spectroscopy, further validating the link between these decomposition products and cathode failure associated with oxygen release. These insights reveal the complex relationship between electrolyte decomposition and cathode degradation due to oxygen release, highlighting a critical failure mechanism in large-scale cylindrical lithium-ion batteries.

Design of dual carbon encapsulated porous micron silicon composite with compact surface for enhanced reaction kinetics of lithium-ion battery anodes

Developing high-performance composites with fast charging and superior cycle life is paramount for lithium-ion batteries (LIBs). Herein, we synthesized a double-shell carbon-coated porous structure composite with a compact surface (P-Si@rGO@C) using low-cost commercial micron-sized silicon (Si) instead of nanoscale silicon. Results reveal that the unique P-Si@rGO@C features high adaptability to volume expansion, accelerates electron/ion transmission rate, and forms a stable solid electrolyte interphase (SEI) film. This phenomenon arises from the synergistic effect of abundant internal voids and an external double-layer carbon shell with a dense surface. Specifically, the P-Si@rGO@C anode exhibits a high initial coulombic efficiency (ICE) (88.0 %), impressive rate-capability (612.1 mAh/g at 2C), and exceptional long-term cyclability (972.2 mAh/g over 500 cycles at 0.5C). Further kinetic studies elucidate the diffusion-capacitance hybrid energy storage mechanism and reveal an improved Li+ diffusion coefficient (from 3.47 × 10-11 to 2.85 × 10-9 cm2 s-1). Ex-situ characterization confirms the crystal phase change of micron-sized Si and the formation of a stable LiF-rich SEI. Theoretical calculations support these findings by demonstrating an enhancement in the adsorption ability of Si to Li+ (from -0.89 to -0.97 eV) and a reduction in the energy migration barrier (from 0.35 to 0.18 eV). Additionally, practical LixSi powder is shown to increase the ICE of full cells from 67.4 % to 87.9 %. Furthermore, a pouch cell utilizing the prelithiated P-Si@rGO@C anode paired with LiNi1/3Co1/3Mn1/3O2 (NCM111) cathode delivers a high initial reversible capacity of 7.2 mAh and 76.8 % capacity retention after 100 cycles. This work provides insights into the application of commercial silicon-aluminum alloy powder in the anode of high-energy LIBs.

Dual-gate design enables intrinsic safety of high-energy batteries

The safety issue hampers the application of high-energy lithium-ion batteries in electric vehicles, grid energy storage, electric ships and aircrafts. The chemical cross-talk, which refers to the migration of energetic intermediates between cathode and anode, initiates battery self-heating and accelerates the intensive heat release during battery thermal failure. However, blocking the chemical cross-talk is extremely hard. Previously, we may expect a thermally stable separator can guard the gate between battery cathode and anode, however, large amount of hot gas breaks the defense mechanically not thermally. Draining the cross-talk gas is of equal importance with blocking it. Herein, a dual-gate design notion is proposed, using separator as “block gate” and vent valve as “removal gate” to regulate the spatial distribution of energetic species to reduce the major heat release during battery thermal runaway. The design is validated by more than 50 battery chemistries. Typically, the maximum temperature of NMC811||Gr pouch cell decreases from >800 °C to <300 °C, the highest temperature rising rate decreases from 761.0 °C/s to 0.013 °C/s. The morphology and crystalline change of cathode verify that the chemical cross-talk is successfully suppressed. Moreover, such design has little side effect on the electrochemical performance of batteries. The dual-gate design breaks the bottleneck for the safety design of high energy batteries, providing insight into the safe utilization of electrochemical energy storage materials.

Toward Cost-Effective High-Energy Lithium-Ion Battery Cathodes: Covalent Bond Formation Empowers Solid-State Oxygen Redox in Antifluorite-Type Lithium-Rich Iron Oxide

Toward Cost-Effective High-Energy Lithium-Ion Battery Cathodes: Covalent Bond Formation Empowers Solid-State Oxygen Redox in Antifluorite-Type Lithium-Rich Iron Oxide

Advanced Micro/Nanostructure Silicon-Based Anode Materials for High-Energy Lithium-Ion Batteries: From Liquid- to Solid-State Batteries

Advanced Micro/Nanostructure Silicon-Based Anode Materials for High-Energy Lithium-Ion Batteries: From Liquid- to Solid-State Batteries

Reduced Volume Expansion of Micron-Sized SiOx via Closed-Nanopore Structure Constructed by Mg-Induced Elemental Segregation.

The inherently huge volume expansion during Li uptake has hindered the use of Si-based anodes in high-energy lithium-ion batteries. While some pore-forming and nano-architecting strategies show promises to effectively buffer the volume change, other parameters essential for practical electrode fabrication, such as compaction density, are often compromised. Here we propose a new in situ Mg doping strategy to form closed-nanopore structure into a micron-sized SiOx particle at a high bulk density. The doped Mg atoms promote the segregation of O, so that high-density magnesium silicates form to generate closed nanopores. By altering the mass content of Mg dopant, the average radii (ranged from 5.4 to 9.7 nm) and porosities (ranged from 1.4 % to 15.9 %) of the closed pores are precisely adjustable, which accounts for volume expansion of SiOx from 77.8 % to 22.2 % at the minimum. Benefited from the small volume variation, the Mg-doped micron-SiOx anode demonstrates improved Li storage performance towards realization of a 700-(dis)charge-cycle, 11-Ah-pouch-type cell at a capacity retention of >80 %. This work offers insights into reasonable design of the internal structure of micron-sized SiOx and other materials that undergo conversion or alloying reactions with drastic volume change, to enable high-energy batteries with stable electrochemistry.