Energy Density Lithium-ion Batteries Research Articles

Electrolyte Design for NMC811||SiOx-Gr Lithium-Ion Batteries with Excellent Low-Temperature and High-Rate Performance

Abstract The use of high-nickel NMC811 cathode and SiOx-Gr anode can greatly improve the overall energy densities of lithium-ion batteries. However, the unfavorable solid electrolyte interphase (SEI) layer generated from the decomposition of EC-based electrolytes lead to the poor cycling stability of NMC811||SiOx-Gr cells. Here we report an electrolyte design of 1.5 M LiPF6 dissolved in FEC/MA/BN 2:2:6 by volume, which can form thin, robust, and homogeneous SEI layer to greatly improve the charge transfer at the electrode-electrolyte interface. Importantly, the designed electrolyte shows an outstanding low temperature performance that it can deliver a capacity of 123.3 mAh g–1 after 50 cycles at -20℃ with a current density of 0.5 C, overwhelming the standard EC-based electrolyte (1.2 M LiPF6 EC/EMC 3:7 by volume) with a capacity of 35.7 mAh g–1. The electrolyte also has a superior rate performance that it achieves a capacity of 122.5 mAh g-1 at a high current density of 10 C. Moreover, the LTE electrolyte holds the great potential of extreme fast-charging ability because of the large part of CC contribution in the CCCV charging model at high charging current densities.

Ultralight, dual-conductive, all-fiber based 3D anode current collector for anode-free lithium metal battery

The anode-free Li metal batteries (AFLMBs), by pairing Li-containing cathode with bare anode current collector (CC), have the potential to enable the maximum improvement (>70 %) in energy density of lithium batteries. Here, we report an ultralight, dual-conductive all-fiber based Cu–CNF-CNT as anode CC, which takes advantage of the high electronic conductivity of carbon nanotube (CNT), good ionic conductivity of copper-coordinated cellulose nanofiber (Cu–CNF), and the three-dimensional porous structure by nanofibers. The interactions between CNTs and Cu-CNFs enables good mechanical strength (4.71 MPa), high electrical conductivity (31.7 S/cm), low density (1.1 g/cm3) and good wettability with electrolyte. The 3D microstructure effectively homogenizes the Li+ flux and buffers the volume changes during cycling, leading to stable Li plating/stripping. As a result, AFLMB using Cu–CNF-CNT exhibits improved capacity retention by 33 % compared to that using Cu CC. The significantly elevated energy-density shows great application potential of the Cu–CNF-CNT in AFLMBs.

Mitigating chain degradation of lithium-rich manganese-based cathode material by surface engineering

Due to offering joint cationic and anionic redox, lithium-rich manganese-based layered oxides (LMLOs) allow high energy density in lithium-ion batteries. However, the oxygen loss, electrode-electrolyte interface side reactions and the structural degradation have resulted in continuous performance decay, hindering the scale-up application of LMLOs. Here, Li1.3V0.94(BO3)2 (LVB) is uniformly coated on the Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) surface by using a sol-gel method combined with a high-temperature calcination. By applying multiple characterizations including in-situ XRD, DEMS, HRTEM, AFM and electrochemical test, we prove that the LVB layer provides a physical barrier, which effectively inhibits the surface reactivity and blocks the chain degradation from the source, improves the reversibility of O2- redox and prevents the phase transition and structural degradation propagating from the surface to the bulk. Moreover, the kinetic investigations and calculations reveal that the LVB modification not only improves the electron conductivity of materials by decreasing the surface work function and increasing the electron density near the Fermi energy level, but also provides expanded pathways with lower impedance to facilitate the Li+ transfer and diffusion. Impressively, the modified cathode exhibits the higher rate performance (151 mAh g-1 at 5C) and improved cycle stability under high cutoff voltage (217.7 mAh g-1 after 200 cycles at 0.2C in 2.0–4.8 V, 92.5 % capacity retention; even in 2.0–5 V, 93.9 % after 100 cycles). This work systematically investigates the inhibiting degradation mechanism and establishes the correlation between the intrinsic structure and surface engineering, and offers valuable insight into the development of high-performance LMLOs.

Mitigating chain degradation of lithium-rich manganese-based cathode material by surface engineering

Due to offering joint cationic and anionic redox, lithium-rich manganese-based layered oxides (LMLOs) allow high energy density in lithium-ion batteries. However, the oxygen loss, electrode-electrolyte interface side reactions and the structural degradation have resulted in continuous performance decay, hindering the scale-up application of LMLOs. Here, Li1.3V0.94(BO3)2 (LVB) is uniformly coated on the Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) surface by using a sol-gel method combined with a high-temperature calcination. By applying multiple characterizations including in-situ XRD, DEMS, HRTEM, AFM and electrochemical test, we prove that the LVB layer provides a physical barrier, which effectively inhibits the surface reactivity and blocks the chain degradation from the source, improves the reversibility of O2- redox and prevents the phase transition and structural degradation propagating from the surface to the bulk. Moreover, the kinetic investigations and calculations reveal that the LVB modification not only improves the electron conductivity by the strong bond of V-O and B-O to decrease the surface work function and increase the electron density near the Fermi energy level, but also provides expanded pathways with lower impedance to facilitate the Li+ transfer and diffusion. Impressively, the modified cathode exhibits the higher rate performance (151 mAh g-1 at 5C) and improved cycle stability under high cutoff voltage (217.7 mAh g-1 after 200 cycles at 0.2C in 2.0–4.8 V, 92.5% capacity retention; even in 2.0–5 V, 93.9% after 100 cycles). This work systematically investigates the inhibiting degradation mechanism and establishes the correlation between the intrinsic structure and surface engineering, and offers valuable insight into the development of high-performance LMLOs.

Revolutionizing multifunctional electrolyte additive design and synthesis for high-voltage nickel-rich batteries in diverse climates

The high-voltage LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode presents a promising avenue for advancing the energy density of lithium-ion batteries. Nevertheless, current limitations primarily arise from electrolyte systems unable to meet stringent criteria, including stable performance under elevated temperatures and efficient discharge at low temperatures. In this study, we address these challenges by designing a molecular structure incorporating boron oxygen functional groups, phenyl-, and fluorine moieties to simultaneously enhance ion conductivity and thermal stability under extreme voltages. A multifunctional electrolyte additive, 3, 4, 5-trifluorophenylboronic anhydride (TFPBA), has been successfully developed via synthesis. TFPBA plays a pivotal role in promoting the formation of a hierarchical cathode electrolyte interphase (CEI) through its preferential decomposition and oxidation processes. This CEI features a mechanically stable inner layer enriched with fluorophenyl- groups, crucial for high-temperature cycling, alongside an outer layer concentrated with BxOyFz complexes that significantly improve Li+ conductivity, ensuring superior performance under low-temperature conditions and at elevated rates. Moreover, TFPBA acts as an HF scavenger within the electrolyte, mitigating corrosive effects on the cathode surface, thereby curtailing CEI reformation and the transition metal dissolution. The Li/NCM622 half cells with TFPBA exhibit impressive capacity retention rates of 92.58%, 80.09%, and 81.77% after extensive cycling at temperatures of −20 °C, 25 °C, and 55 °C, respectively. Moreover, NCM622/graphite full cells with TFPBA achieve a remarkable capacity retention of 97.97% after 150 cycles at room temperature. Our findings highlight the exceptional electrochemical performance of NCM622 cathodes at elevated voltages across a wide temperature range, providing valuable insights for the development of advanced electrolytes in high-demand applications.

Zirconium effect on the lithiation mechanism of LiNi0.83Mn0.05Co0.12O2 positive electrode material

Ni-rich LiNi1-x-yMnxCoyO2 (x + y ≤ 0.2) materials are employed to enhance the energy density of lithium-ion batteries, while they are still facing the stability issue. Doping is considered as an efficient approach to improve the stability of the LiNi1-x-yMnxCoyO2 materials. A considerable number of studies have concluded that Zr-doping improves the stability when undoped and doped LiNi1-x-yMnxCoyO2 materials are lithiated under the same conditions. Unfortunately, a fundamental understanding of the Zr dopants role during lithiation conditions is still lacking. This work investigates the Zr effects on lithiation mechanism of LiNi0.83Mn0.05Co0.12O2 (NMC). The main findings are: First, the NMC and Zr-doped NMC have different lattice parameter growth speeds, and the (003) & (101) lattice planes form order structures at lower temperatures during lithiation process when the dopant is included. Second, Zr is prone to locate near the surface region of NMC secondary particles. Third, when lithiation time increase from 8 h to 12 h at 800 oC, the undoped NMC electrochemical performance deteriorates whereas the doped material improves. These findings highlight that understanding the mechanism behind lithiation conditions is essential for doped LiNi1-x-yMnxCoyO2. The insights revealed in this work can guide for design other dopants for Ni-rich positive electrode materials.

Mitigating chain degradation of lithium-rich manganese-based cathode material by surface engineering

Due to offering joint cationic and anionic redox, lithium-rich manganese-based layered oxides (LMLOs) allow high energy density in lithium-ion batteries. However, the oxygen loss, electrode-electrolyte interface side reactions and the structural degradation have resulted in continuous performance decay, hindering the scale-up application of LMLOs. Here, Li1.3V0.94(BO3)2 (LVB) is uniformly coated on the Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) surface by using a sol-gel method combined with a high-temperature calcination. By applying multiple characterizations including in-situ XRD, DEMS, HRTEM, AFM and electrochemical test, we prove that the LVB layer provides a physical barrier, which effectively inhibits the surface reactivity and blocks the chain degradation from the source, improves the reversibility of O2- redox and prevents the phase transition and structural degradation propagating from the surface to the bulk. Moreover, the kinetic investigations and calculations reveal that the LVB modification not only improves the electron conductivity by the strong bond of V-O and B-O to decrease the surface work function and increase the electron density near the Fermi energy level, but also provides expanded pathways with lower impedance to facilitate the Li+ transfer and diffusion. Impressively, the modified cathode exhibits the higher rate performance (151 mAh g-1 at 5C) and improved cycle stability under high cutoff voltage (217.7 mAh g-1 after 200 cycles at 0.2C in 2.0–4.8 V, 92.5% capacity retention; even in 2.0–5 V, 93.9% after 100 cycles). This work systematically investigates the inhibiting degradation mechanism and establishes the correlation between the intrinsic structure and surface engineering, and offers valuable insight into the development of high-performance LMLOs.

High voltage electrochemical performance of ultrahigh-Ni cathode via in situ constructed nano-LiF and CNT composite cathode electrolyte interphase layer

Ultrahigh-nickel LiNixCoyMn1-x-yO2 cathode material (Ni content ≥ 0.9) is of great significance for the development of high energy density of lithium-ion batteries. However, its high surface activity leads to more surface residual lithium formation and deterioration of electrochemical performance, especially at high voltage. Here we add NH4F and nitrogen-doped carbon nanotubes (CNT) during the dimethyl carbonate (DMC) washing process, and constructed in situ the nano-LiF and CNT composite cathode electrolyte interphase (CEI) layer while removing part of residual lithium, effectively optimizing the surface environment of LiNi0.9Co0.05Mn0.05O2. The modified LiNi0.9Co0.05Mn0.05O2 has a capacity retention rate of 61.3 % after 200 cycles between 2.8 and 4.5 V at 1C, significantly higher than the 46.7 % of the unwashed sample, and a specific discharge capacity of 146.9 mAh g−1 at 5C, compared to 127.5 mAh g−1 for the unwashed sample. Benefit from the alleviation of polarization and the increase of Li+ diffusion coefficient, the stable CEI layer provides effective protection for LiNi0.9Co0.05Mn0.05O2 under 4.5 V, alleviating surface side reactions. In this paper, a simple and effective strategy is developed to optimize the surface of Ni-rich cathode material, which provides a new insight for the treatment of surface residual lithium.

Rigid-flexible mediated Co-polyimide enabling stable silicon anode in lithium-ion batteries

Silicon is considered as a promising electrode materials for the next generation of lithium-ion batteries. However, it’s commercial applications are hindered by significant volume changes. In this study, copolyimide binders with adjustable rigidity and flexibility were synthesized through simple copolymerization. The rigid segments containing adenine groups (p-APA) provide excellent mechanical strength and interface interaction, while flexible segments containing siloxane bonds and alkane chains (DS-NH2) can buffer volume changes through enhanced mobility and topological entanglement of molecular segments. Optimizing the copolymerization ratio helps minimize damage to the silicon electrode structure and stabilizes solid electrolyte interphase (SEI) growth. Compared to the rigid polyimide binders, rigid-flexible coupling strategy improves cycling stability, remaining a capacity of 2170 mAh/g at 2 A/g after 200 cycles and exhibiting stable cycling for over 750 cycles with a capacity limitation of 1500 mAh/g. The high mass loading silicon anodes, micron-sized silicon oxide electrodes and the full cells also exhibit favorable electrochemical performance. This research provides valuable insights for designing high-performance aromatic polymer binders for high energy density lithium-ion batteries.

Influence of the temperature-induced ordered-disordered phases for iron difluoride on the electrochemical performance

Iron difluoride (FeF2) is one of the promising cathodes to achieve high energy-density lithium-ion batteries (LIBs). However, the sluggish ion transportation kinetics in the FeF2 bulk phase may cause large voltage hysteresis and lower cell efficiency, which hinders its commercial adoption. Introducing a disordered phase into the ordered bulk FeF2 is proposed to promote ion transportation and increase ion diffusion channels. Here, varying ratios of the disordered phase are incorporated into the ordered matrix of FeF2 by adjusting the annealed temperatures. The ion transportation is improved due to the optimal ratio of the disordered to ordered (RDO) phase. Among four electrodes, the RDO25% electrode demonstrates the least electrochemical polarization of 1.22V and the lowest voltage hysteresis of about 1.0V, in addition to delivering a discharge capacity of 128 mAh g-1 after 100 cycles in the carbonate-type electrolyte. The introduction of the disordered phase enables FeF2 to exhibit a distinct intercalation and conversion dual-mechanism cathode. Additionally, appropriate ratios of the disordered-ordered phase can mitigate nanoparticle agglomeration, establish a conformal cathode electrolyte interface (CEI), reduce interfacial resistance, and thereby enhance ion transport.

Stable operation of SiO anodes enabled by a multifunctional molecular crosslinker

SiO anodes are promising for energy-dense lithium-ion batteries, however, they suffer from short cycle life caused by large volume change (∼200%) and low initial Coulomb efficiency (ICE). Herein, we report a conceptual strategy to boost the electrochemical performance of SiO by enhancing the interaction between binders and conductive additives via a molecular crosslinker with both pyrene ring and adamantyl group (AdPy). Benefiting from the inclusion interaction between beta-cyclodextrin polymers (βCDp) and AdPy as well as the π-π interaction between single-walled carbon nanotube (SWCNT) and AdPy, a robustly conductive and adhesive network is constructed for maintaining integral electrode structure and robust conductive network during charge/discharge cycles. The resultant SiO electrode with SWCNT/AdPy-βCDp networks achieves larger initial capacity, higher ICE and better cycle stability than those of SiO electrode with SWCNT/βCDp complex, indicating the key role of AdPy crosslinker in enhancing electrochemical performance. Experimental results suggest that the interaction between binders and conductive additives can effectively alleviate stress generated from SiO volume changes during cycling. This work provides a promising platform to construct dynamic cross-linking conductive and adhesive network for boosting the lithium storage performance of high-capacity electrode materials.

A Slightly Expanded Graphite Anode with High Capacity Enabled By Stable Lithium-Ion/Metal Hybrid Storage.

Integrating lithium-ion and metal storage mechanisms to improve the capacity of graphite anode holds the potential to boost the energy density of lithium-ion batteries. However, this approach, typically plating lithium metal onto traditional graphite anodes, faces challenges of safety risks of severe lithium dendrite growth and short circuits due to restricted lithium metal accommodation space and unstable lithium plating in commercial carbonate electrolytes. Herein, a slightly expanded spherical graphite anode is developed with a precisely adjustable expanded structure to accommodate metallic lithium, achieving a well-balanced state of high capacity and stable lithium-ion/metal storage in commercial carbonate electrolytes. This structure also enables fast kinetics of both Li intercalation/de-intercalation and plating/stripping. With a total anode capacity of 1.5 times higher (558mAhg-1) than graphite, the full cell coupled with a high-loading LiNi0.8Co0.1Mn0.1O2 cathode (13mgcm-2) under a low N/P ratio (≈1.15) achieves long-term cycling stability (75% of capacity after 200 cycles, in contrast to the fast battery failure after 50 cycles with spherical graphite anode). Furthermore, the capacity of the full cell also reaches a low capacity decay rate of 0.05% per cycle at 0.2C under the low temperature of -20°C.

Assembled MXene-Liquid Metal Cages on Silicon Microparticles as Self-Healing Battery Anodes.

In pursuit of higher energy density in lithium-ion batteries, silicon (Si) has been recognized as a promising candidate to replace commercial graphite due to its high theoretical capacity. However, the pulverization issue of Si microparticles during lithiation/delithiation results in electrical contact loss and increased side reactions, significantly limiting its practical applications. Herein, we propose to utilize liquid metal (LM) particles as the bridging agent, which assemble conductive MXene (Ti3C2Tx) sheets via coordination chemistry, forming cage-like structures encapsulating mSi particles as self-healing high-energy anodes. Due to the integration of robust Ti3C2Tx sheets and deformable LM particles as conductive buffering cages, simultaneously high-rate capability and cyclability can be realized. Post-mortem analysis revealed the cage structural integrity and the maintained electrical percolating network after cycling. This work introduces an effective approach to accommodate structural change via a resilient encapsulating cage and offers useful interface design considerations for versatile battery electrodes.

Enhanced Low-Temperature Resistance of Lithium-Metal Rechargeable Batteries Based on Electrolyte Including Ethyl Acetate and LiDFOB Additives.

To meet the demand for higher energy density in lithium-ion batteries and expand their application range, coupling lithium metal anodes with high-voltage cathodes is an ideal solution. However, the compatibility between lithium metal batteries and electrolytes affects their applicability. In this study, proposes a locally concentrated electrolyte based on ethyl acetate (EA) as the solvent, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the lithium salt, and lithium difluorooxoborate (LiDFOB) as a sacrificial agent to enhance the low-temperature and high-voltage endurance of Li//Lithium cobalt oxide (LCO) batteries. The Li//LCO battery can operate within the voltage range of 3 to 4.5 V, with an initial discharge specific capacity of 174.5 mAh g-1 at 20 °C. At -40 °C, after 200 cycles, the capacity retention rate is 87.7 %. It can operate under extreme conditions of -70 °C, with a discharge specific capacity of 112.6 mAh g-1. Additionally, LCO//HC batteries using this electrolyte demonstrate excellent performance. Present work provides a new perspective for the optimization of electrolytes for low-temperature lithium-ion batteries.

In Situ Construction of a Multifunctional Interphase Enabling Continuous Capture of Unstable Lattice Oxygen Under Ultrahigh Voltages.

The use of nickel-rich layered materials as cathodes can boost the energy density of lithium batteries. However, developing a safe and long-term stable nickel-rich layered cathode is challenging primarily due to the release of lattice oxygen from the cathode during cycling, especially at high voltages, which will cause a series of adverse effects, leading to battery failure and thermal runaway. Surface coating is often considered effective in capturing active oxygen species; however, its process is rather complicated, and it is difficult to maintain intact on the cathode with large volume changes during cycling. Here, we propose an in situ construction of a multifunctional cathode/electrolyte interphase (CEI), which is easy to prepare, repairable, and, most importantly, capable of continuously capturing active oxygen species during the entire life span. This unique protective mechanism notably improves the cycling stability of Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) cells at rigorous working conditions, including ultrahigh voltage (4.8 V), high temperature (60 °C), and fast charging (10 C). An industrial 1 A h graphite||NCM811 pouch cell achieved stable operation of 600 cycles with a capacity retention of 79.6% at 4.4 V, exhibiting great potential for practical use. This work provides insightful guidance for constructing a multifunctional CEI to bypass limitations associated with high-voltage operations of nickel-rich layered cathodes.

Enhanced cycling stability in 4.6 V LiCoO2 for high energy density lithium-ion batteries through Al and Y co-doping

For the first time, this work investigates the synergetic impact of yttrium (Y) and aluminium (Al) co-doping on the electrochemical properties of 4.6 V LiCoO2 (LCO) cathode for high energy density lithium-ion batteries. The optimized LCO demonstrates an impressive initial discharge capacity of 208.6 mAh g−1 in the voltage range of 3–4.6 V, along with superior structural stability, retaining over 86 % of its initial capacity even after 125 cycles at the current of 100 mA g−1 that is far higher than the capacity retention of 40 % for the pristine LCO under the same condition. Thanks to the synergistic effect, Al in Co layers enhances the bonds of Al/Co-O to stabilize oxygen in the LCO crystal structure while Y serves “pillar” in Li layers, migrated from the initial Co layers during cycling process, effectively curtail the formation and expansion of interlayer cracking, which contributes to the long-term cycle stability of LCO under high voltage. Most importantly, Al/Y co-doping is a facile process compatible with the existing industrial infrastructure for LCO mass production, and thus it can be scaled up readily for commercial applications. Al/Y co-doped LCO is assembled into commercial-level pouch cells with graphite anode, achieves an extremely high energy density of 750 Wh/L, and exhibits a superior cycling stability and obtains a capacity retention of 88.2 % at 25 °C after 800 cycles with the high cutoff voltage of 4.55 V.

Noncombustible gel polymer electrolyte inspired by bio-radical chemistry for high voltage and high safety Ni-rich lithium batteries

For high energy density lithium-ion batteries (LIBs) with nickel-rich ternary cathodes, the chemical degradation of electrolytes caused by free radical reactions and the hazards of thermal runaway have always been significant challenges. Inspired by the free radical scavenging of living organisms and multiphase synergistic flame retardant mechanism, we innovatively designed and prepared a multifunctional flame retardant HCCP-TMP that combines flame retardancy and free radical scavenging by combining hindered amine and cyclophosphazene. Only 1 wt% HCCP-TMP can make the polyacrylate-based gel polymer electrolyte (GPE) incombustible. Moreover, the equipped NCM811//Graphite pouch cells don't exhibit combustion behavior after thermal runaway and can resist mechanical abuse. Based on the above noncombustible GPE, the NCM811//Li battery exhibits capacity retention rate of 82.2 % after 100 cycles at a current density of 2 C and in the voltage range of 3.0–4.7 V, exhibiting excellent cyclability under high voltage. This simple molecular design simultaneously improves the fire safety and high voltage stability, demonstrating enormous application potential in the field of advanced LIBs with high safety and high energy density.

Dynamically constructing robust cathode-electrolyte-interphase on nickel-rich cathode by organic boron additive for high-performance lithium-ion batteries

Nickel-rich ternary cathode materials LiNi0.8Co0.1Mn0.1O2 (NCM811) have attracted broad attention due to their high voltage and high energy density for lithium-ion batteries. However, rapid capacity decay due to unstable particle surface inhibit the application. Artificial cathode electrolyte interface (CEI) is undoubtedly a more effective and simpler way to solve this issue. Here, stable and highly conductive in situ CEI is designed using a low-cost organic boron additive isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (ITD). Higher occupied molecular orbital energy endows ITD ability to participate in forming CEI. ITD-contained CEI can reduce nickel dissolving, resulting in a lower self-discharge rate, which is benefit from the uniform and stable CEI on the NCM811 surface. As expected, ITD-based CEI can restrain NCM811crystal cracking in Li||NCM811 half batteries, improving capacity retention from 29.4 % to 93.0 % after 200 cycles at 1C (1C = 200 mA g−1). It is worth mentioning that ITD–derived CEI is conducive to ion migration, which improve the rate capacity retention from 91.5 % to 95.5 %.

Composition and state prediction of lithium-ion cathode via convolutional neural network trained on scanning electron microscopy images

High-throughput materials research is strongly required to accelerate the development of safe and high energy-density lithium-ion battery (LIB) applicable to electric vehicle and energy storage system. The artificial intelligence, including machine learning with neural networks such as Boltzmann neural networks and convolutional neural networks (CNN), is a powerful tool to explore next-generation electrode materials and functional additives. In this paper, we develop a prediction model that classifies the major composition (e.g., 333, 523, 622, and 811) and different states (e.g., pristine, pre-cycled, and 100 times cycled) of various Li(Ni, Co, Mn)O2 (NCM) cathodes via CNN trained on scanning electron microscopy (SEM) images. Based on those results, our trained CNN model shows a high accuracy of 99.6% where the number of test set is 3840. In addition, the model can be applied to the case of untrained SEM data of NCM cathodes with functional electrolyte additives.

Boosting the initial coulombic efficiency for SiO anodes through component controlling and microcrystalline size limiting regulated by carbon layer

Silicon-based anode materials are attracting considerable attention due to their high specific capacity for further improving the energy density of lithium-ion batteries (LIBs). Among them, silicon monoxide (SiO) has a good balance between high specific capacity and cycling lifespan, which is increasingly valuable in the market of lithium-ion batteries. However, its poor initial coulombic efficiency (ICE) severely impedes the commercialization of SiO. Although prelithiation and surface carbon coating are considered effective methods to reduce irreversible consumption during the initial lithiation process, the synergistic relationship between prelithiation and carbon coating has not yet been confirmed. Herein, we used LiH as solid-phase prelithiation reagent and acetylene as carbon source for carbon coating to improve the ICE as well as cyclic stability of SiO anode. Results show that the process sequence of pre-lithiation and carbon coating has a significant impact on regulating the internal lithium silicate components and the microcrystalline size of silicon and lithium silicates. A prioritizing carbon layer coating subsequent to prelithiation can achieve physical barrier effect, effectively regulating the prelithiation reaction process to refine the internal silicon and lithium silicate crystal material, and avoiding the formation of lithium-poor Li2Si2O5 phase. The obtained SOC-P sample exhibits a superior ICE of 88.1 % and a stable irreversible capacity of 842.9 mAh/g after 200 cycles. This work provides practical reference idea for solving the low initial efficiency issue of SiO anode material.