High-energy Lithium-ion Batteries Research Articles

Building Three-Dimensional Network Structures of Silicon–Graphite/Carbon Nanotube Composite Anode for High-Energy Lithium-Ion Batteries

As the increasing demand for high-energy-density lithium-ion batteries (LIBs), silicon-based anodes have become an excellent alternative to conventional graphite anodes owing to their high theoretical capacities. In this study, a three-dimensional (3D) electric network structure was developed using an aqueous carbon nanotube (CNT) suspension to improve the specific capacity and cyclability of Si–graphite electrodes. Field-emission scanning electron microscopy demonstrated that longer single-walled CNTs (SWCNTs) effectively covered and interconnected the entire surface of the Si and graphite particles, thereby providing electric conduction networks and facile access to Li ions in the electrode and structural strength with flexibility. As a result, 3D networks structure of Si–graphite/SWCNTs (Si-G-SW) exhibited the highest specific capacity (829.7 mAh g−1 at 0.1 A g−1), rate capability, and cycle stability (>79% after 100 cycles). We expect this robust 3D network electrode system to provide a new route for high-energy-density LIB anodes.

Polymeric Backbone Eutectogel Electrolytes for High-Energy Lithium-Ion Batteries.

This work introduces a polymeric backbone eutectogel (P-ETG) hybrid solid-state electrolyte with an N-isopropylacrylamide (NIPAM) backbone for high-energy lithium-ion batteries (LIBs). The NIPAM-based P-ETG is (electro)chemically compatible with commercially relevant positive electrode materials such as the nickel-rich layered oxide LiNi0.6Mn0.2Co0.2O2 (NMC622). The chemical compatibility was demonstrated through (physico)chemical characterization methods. The nonexistence (within detection limits) of interfacial reactions between the electrolyte and the positive electrode, the unchanged bulk crystallographic composition, and the absence of transition metal ions leaching from the positive electrode in contact with the electrolyte were demonstrated by Fourier transform infrared spectroscopy, powder X-ray diffraction, and elemental analysis, respectively. Moreover, the NIPAM-based P-ETG demonstrates a wide electrochemical stability window (1.5-5.0 V vs Li+/Li) and a reasonably high ionic conductivity at room temperature (0.82 mS cm-1). The electrochemical compatibility of a high-potential NMC622-containing positive electrode and the P-ETG is further demonstrated in Li|P-ETG|NMC622 cells, which deliver a discharge capacity of 134, 110, and 97 mAh g-1 at C/5, C/2, and 1C, respectively, after 90 cycles. The Coulombic efficiency is >95% at C/5, C/2, and 1C. Hence, gaining scientific insights into the compatibility of the electrolytes with positive electrode materials that are relevant to the commercial market, like NMC622, is important because this requires going beyond the electrolyte design itself, which is essential to their practical applications.

Enabling high-performance lithium iron phosphate cathodes through an interconnected carbon network for practical and high-energy lithium-ion batteries

The olivine lithium iron phosphate (LFP) cathode has gained significant utilization in commercial lithium-ion batteries (LIBs) with graphite anodes. However, the actual capacity and rate performance of LFP still require further enhancement when combined with high-capacity anodes, such as silicon (Si) anodes, to achieve high-energy LIBs. In this study, we introduce a gelatin-derived carbon network into a nanosized LFP cathode without the need for additional binding and conductive agents, employing a simple and cost-effective method. The resulting cathode exhibits an extremely high LFP content (∼92.3 wt%), enabling it to show a high real capacity of 159.7 mAh/g at 0.2 C in half cells. Additionally, the interconnected carbon network effectively facilitates electron and Li+ transport, providing rapid pathways within the LFP nanoparticles. Consequently, the cathode exhibits superior rate capability (107.3 mAh/g at 10 C) and good cycling performance (with a capacity retention of ∼ 80 % after 500 cycles). To further assess its practical viability, the LFP cathode is assembled into a full cell utilizing a Si-based anode with a N/P ratio of 1.1. The resulting full cell delivers a significantly high energy density of 419.7 Wh kg−1, coupled with prolonged cycle life, highlighting its promising prospects for practical applications.

Design of Nb5+-doped high-nickel layered ternary cathode material and its structure stability

LiNi0.8Co0.1Mn0.1O2 (NCM811) is one of the most promising cathode materials for high-energy lithium-ion batteries, but there are still problems such as rapid capacity decay during charge and discharge and poor cycle performance. Elemental doping can significantly improve the electrochemical performance of high nickel ternary cathode materials. In this work, Nb5+-doped NCM811 cathode material was successfully synthesized. The results show that Nb5+ doping helps to increase the interlayer spacing of the lithium layer, electron transport, and structural stability, thereby significantly improving the conductivity of Li+. At a high voltage of 4.6 V, the initial discharge specific capacity of 1% Nb5+-doped NCM811 cathode material at 0.1 C is 222.3 mAh·g−1, and the capacity retention rate after 100 cycles at 1 C is 92.03%, which is far more than the capacity retention rate of NCM811 under the same conditions (74.30%). First-principles calculations prove that 1% Nb5+-doped NCM811 cathode material shows the highest electronic conductivity and Nb5+ doping will not change the lattice structure, demonstrating the effectiveness of the proposed strategy.

Domino Reactions Enabling Sulfur-Mediated Gradient Interphases for High-Energy Lithium Batteries.

Silicon (Si)-based anodes are currently considered a feasible solution to improve the energy density of lithium-ion batteries owing to their sufficient specific capacity and natural abundance. However, Si-based anodes exhibit low electric conductivities and large volume changes during cycling, which could easily trigger continuous breakdown/reparation of the as-formed solid-electrolyte-interphase (SEI) layer, seriously hampering their practical application in current battery technology. To control the chemoelectrochemical instability of the conventional SEI layer, we herein propose the introduction of elemental sulfur into nonaqueous electrolytes, aiming to build a sulfur-mediated gradient interphase (SMGI) layer on Si-based anodes. The SMGI layer is generated through the domino reactions (i.e., electrochemical cascade reactions) involving the electrochemical reductions of elemental sulfur followed by nucleophilic substitutions of fluoroethylene carbonate, which endows the corresponding SEI layer with strong elasticity and chemomechanical stability and enables rapid transportation of Li+ ions. Consequently, the prototype Si||LiNi0.8Co0.1Mn0.1O2 cells attain a high-energy density of 622.2 W h kg-1 and a capacity retention of 88.8% after 100 cycles. Unlike previous attempts based on sophisticated chemical modifications of electrolyte components, this study opens a new avenue in interphase design for long-lived and high-energy rechargeable batteries.

High Performance Hybrid Aqueous Li/NiCl2 Rechargeable Batteries with Water‐Stable High Lithium‐Ion Conductivity Solid Electrolyte

AbstractThe feasibility of a novel high specific energy and power density rechargeable aqueous lithium battery with a lithium anode, an aqueous NiCl2 catholyte, and a water‐stable high lithium‐ion conducting solid electrolyte separator was investigated. Water‐stable Li1.6Al0.4Ge0.2Ti1.4(PO4)3‐10 wt % TiO2‐3 wt % LiCl ⋅ H2O‐expoxy resin (LAGTP‐T), which has a high lithium‐ion conductivity of 10−3 S cm−1 at 25 °C and an excellent bending strength of 150 N mm−2, was used as the separator between the lithium anode and the aqueous NiCl2 catholyte in the rechargeable aqueous Li/NiCl2 battery. The battery was successfully operated at 5 mA cm−2 and room temperature. The estimated specific energy density of the battery based on the cell components of a 200 μm thick LAGTP‐T, a lithium anode, current collectors, and an interlayer electrolyte is higher than that of the conventional lithium‐ion battery with a carbon anode and a LiCoO2 cathode at a high specific capacity of more than 15 mAh cm−2, and that at 50 mAh cm−2 is two times higher than that of the lithium‐ion battery.

A new high-valence cation pillar within the Li layer of compositionally optimized Ni-rich LiNi0.9Co0.1O2 with improved structural stability for Li-ion battery

Elevating the nickel (Ni) content within layered cathodes constitutes a straightforward and effective approach to enhance the energy density of lithium-ion batteries (LIBs). However, the phase transition from H2 to H3 introduces substantial alterations in lattice volume, leading to structural degradation and diminished electrochemical performance. This study employs density functional theory (DFT) calculations to determine that the formation energy for Nb5+ occupied at Li 3b sites is lower compared to that of Ni 3a and Co 3a sites, yet higher than that of Mn 3a sites. This suggests a preference for Nb5+ doping within the Li layer of Mn-free cathodes. Motivated by these DFT results, we show the viability of high-valence Nb5+ as a stable pillar in the compositionally optimized binary oxide LiNi0.9Co0.1O2. The inclusion of this Nb5+ pillar in the Li layer of Ni/Co-based oxide significantly enhances the reversibility of the H2–H3 redox couple and mitigates microcrack formation in polycrystalline cathodes. As a result, the Nb-doped Ni/Co-based cathode exhibits an extended cycling lifespan, elevated rate capability, and increased thermal stability compared to the undoped. This investigation achieves precise control over doping sites by optimizing the chemical composition of Ni-rich cathodes and provides novel insights into advancing their electrochemical performance for high-energy LIBs.

High Rate and Low-Temperature Stable Lithium Metal Batteries Enabled by Lithiophilic 3D Cu-CuSn Porous Framework.

Lithium (Li) metal is regarded as the "Holy Grail" of anodes for high-energy rechargeable lithium batteries by virtue of its ultrahigh theoretical specific capacity and the lowest redox potential. However, the Li dendrite impedes the practical application of Li metal anodes. Herein, lithiophilic three-dimensional Cu-CuSn porous framework (3D Cu-CuSn) was fabricated by a vapor phase dealloying strategy via the difference in saturated vapor pressure between different metals and the Kirkendall effect. CuSn alloy sites were converted into LiSn alloy sites through the molten Li infusion method, and composite Li metal anodes (3D Cu-LiSn-Li) are achieved. Alloyed tin, as the bridge between the porous copper substrate and metallic Li, plays a critical role in optimizing Li nucleation and enhancing the fast lithium migration kinetics. This work demonstrates that lithiophilic binary copper alloys are an effective way to achieve room-temperature high rate performance and satisfied low-temperature cycling stability for Li metal batteries.

Restoring the Crystal Structure of Single-Crystalline High Ni Ncm with Synthetic Heat Treatment Profile Control

Single-crystalline high Ni NCM is regarded as a next generation cathode candidate for high-energy lithium ion batteries with great potential due to its advanced crystal structural and chemical stability. The synthesis of single-crystalline high Ni NCM was studied using in-operando heating XRD. The change of the crystal structure of single-crystalline NCM was observed while raising the synthesis temperature. The synthesis was carried out in two steps, with the first step at 860 degrees to form the phase and grow the particle size, and the second step around 740 degrees to recover the collapsed structure by the first heat treatment. XRD data and Rietveld refinement results showed that the half width of (104) peak decreased over time in each step, but tended to increase as it moved from 1st step to 2nd step. In addition, it was confirmed that Li/Ni cation mixing maintained a high value at the 1st step but then steadily decreased at the 2nd step, which means relatively low temperature heat treatment is effective to recover crystal structural anti-site defects. To evaluate the electrochemical properties of structural restoration, coin half cell characteristics were evaluated. It was showed that the longer time of 2nd step of the heat treatment, the higher efficiency and capacity due to structural recovery.Overall, this study provides insights into the synthesis of single-crystalline high Ni NCM and their crystal structure changes under real-time heating. This findings highlight the importance of the two-step synthesis process and the role of relatively low temperature of 2nd step heat treatment that can reduce Li/Ni cation mixing through structural recovery.

(Invited) Additives Approach to Improve the Performance of LiNi0.5Mn1.5O2 5V Cathodes

The high voltage spinel cathode of LiNi0.5Mn1.5O2 has an average working voltage of 4.7 V, high-rate performance with faster diffusion properties, and is viewed as one of the promising cathode materials for high energy lithium-ion batteries. The lack of Co in such cathode materials is also advantageous due to the issues of artisan mining and geopolitical tensions associated with Co mining. However, the high working voltages in LiNi0.5Mn1.5O2 exceeds the stability of electrolyte window and the redox center in the cathode materials is mainly Ni2+ while Mn stays at the 4+ charge state. Due to the dominance of the Mn elements in the cathode, acid leaching from the impurity of the electrolytes can cause Mn dissolution, and the degradation of LNMO//Gr is associated with transition metal dissolution and crosstalk to the anode side, causing loss of inventory Li loss. For example, the decomposition of ethylene carbonate leads to formation of glycolic acid and difluorophosphoric acid (HPO2F2).Using additives in the electrolyte formulation is an economic way of improving the performance without significant change in either the processing industry or manufacturing technology, and here we present the approach of using a combinatorial approach to optimize the additives for LNMO//Gr full cells. The degradation mechanism will also be discussed. Machine learning (ML) method has been used effectively to predict molecular structures, preferred quantity, as well as formation of interfaces.1-3 In this study, we used ML to formulate the high-performance additives with both improved capacity retention and reduced initial and final impedance. Okamoto, Y.; Kubo, Y., Ab Initio Calculations of the Redox Potentials of Additives for Lithium-Ion Batteries and Their Prediction through Machine Learning. ACS Omega 2018, 3 (7), 7868-7874.Bhowmik, A.; Castelli, I. E.; Garcia-Lastra, J. M.; Jørgensen, P. B.; Winther, O.; Vegge, T., A perspective on inverse design of battery interphases using multi-scale modelling, experiments and generative deep learning. Energy Storage Materials 2019, 21, 446-456.Hildenbrand, F.; Aupperle, F.; Stahl, G.; Figgmeier, E.; Sauer, D. U., Selection of Electrolyte Additive Quantities for Lithium-Ion Batteries Using Bayesian Optimization. Batteries & Supercaps 2022, 5 (7), e202200038.

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

End of life (EoL) lithium-ion batteries (LIBs) are piling up at an intimidating rate which is alarming for the environmental health and balance. The rise of renewable technologies such as electric vehicles (EV) needs to be balanced with LIB recycling to reduce the carbon footprint, ensure sustainable development, and create a circular supply chain. LiNixCoyMnzO2 (NCM) cathode materials being a dominant chemistry in high energy LIBs makes 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 which involve toxic organic solvents. Herein, we have demonstrated a process which integrates the pretreatment and relithiation of the cathode black. Cathode material from EoL EV batteries is treated in 100g per batch operation and the regenerated cathode active material demonstrates 100% electrochemical performance recovery, with 91% yield rate, and showed promise to further scale up. No use of toxic organic solvents makes our process unique with minimal environmental impact. This process has the advantages of integration, scalability, and universality, which clears the barricade for the direct recycling to move from lab to industry scale with considerable profitability.

Enhanced Cycling Performance by Transition Metal Substitution on Li2CuO2 Cathode Additive for Advanced Lithium-Ion Battery

Lithium-Ion batteries (LIBs) have made remarkable progress in the last decade and have been employed so far as the most popular power source for electric vehicles (EVs). However, the energy density issue still remains a drawback for LIBs on long-range driving of EVs for the reason of significant irreversible Li+ loss in the initial charging process of LIBs, induced by a spontaneous formation of solid electrolyte interphase (SEI) on the anode surface. Therefore, strategic studies are required to maximize the energy density of LIBs as compensation of the initial loss of Li+ during cell operation. The utilization of a Li-excess cathode additive in commercial cathodes is an ideal approach to minimize the loss of energy density of LIBs. Recently, Li2CuO2 has been proposed as a potential cathode additive with many advantages over other candidates, including the following: (i) high charge capacity (~ 490 mAh g-1), (ii) comparable operating voltage window (2.5 ~ 4.3 V vs. Li/Li+) to commercial cathode materials, and (iii) abundance of copper (Cu) on the earth. But, its practical use is still restricted by the structural instability and spontaneous oxygen (O2) evolution (> 3.8 V vs. Li/Li+), which results in loss of reversibility during subsequent cycling. It is thus crucial to reinforce the structure of Li2CuO2 to make it more reliable as a cathode additive for charge compensation. In a pursuit of improving the structural stability of Li2CuO2, herein, we demonstrate structural modification via co-substitution by heteroatoms, such as nickel (Ni) and manganese (Mn), for improving the structural stability and electrochemical performance of Li2CuO2. Such an approach effectively enhances the reversibility of Li2CuO2 by suppressing continuous structural degradation and O2 gas evolution during cycling. Our findings provide new conceptual pathways for developing advanced cathode additives for high-energy LIBs.

Dual-modification of Ni-rich cathode materials through strontium titanate coating and thermal treatment

Ni-rich layered structure ternary oxides, such as LiNi0.8Co0.1Mn0.1O2 (NCM811), are promising cathode materials for high-energy lithium-ion batteries (LIBs). However, a trade-off between high capacity and long cycle life still obstructs the commercialization of Ni-rich cathodes in modern LIBs. Herein, a facile dual modification approach for improving the electrochemical performance of NCM811 was enabled by a typical perovskite oxide: strontium titanate (SrTiO3). With a suitable thermal treatment, the modified cathode exhibited an outstanding electrochemical performance that could deliver a high discharge capacity of 188.5 mAh/g after 200 cycles under 1C with a capacity retention of 90%. The SrTiO3 (STO) protective layer can effectively suppress the side reaction between the NCM811 and the electrolyte. In the meantime, the pillar effect provided by interfacial Ti doping could effectively reduce the Li+/Ni2+ mixing ratio on the NCM811 surface and offer more efficient Li+ migration between the cathode and the coating layer after post-thermal treatment (≥600 °C). This dual modification strategy not only significantly improves the structural stability of Ni-rich layered structure but also enhances the electrochemical kinetics via increasing diffusion rate of Li+. The electrochemical measurement results further disclosed that the 3 wt% STO coated NCM811 with 600 °C annealing exhibits the best performance compared with other control samples, suggesting an appropriate temperature range for STO coated NCM811 cathode is critical for maintaining a stable structure for the whole system. This work may offer an effective option to enhance the electrochemical performance of Ni-rich cathodes for high-performance LIBs.

Design of phosphorus-doped porous hard carbon/Si anode with enhanced Li-ion kinetics for high-energy and high-power Li-ion batteries

With the rapid progress of portable electronics and electric vehicles, high-energy lithium-ion batteries (LIBs) with fast-charging technology are urgently required. Silicon (Si) is considered as the most promising anode candidate for high-energy LIBs but challenging to large-scale commercialization due to its huge volume change and poor conductivity. To develop high-capacity Si-based anode materials with enhanced lithium-ion diffusion and fast reaction kinetics, we design a novel high-Si-content Si/hard carbon composite via scalable methods. The combination between phosphorus-doped hard carbon with porous structure and uniformly distributed Si nanolayers effectively improve lithium-ion kinetics and mitigate the volume change of Si. As a result, the architecture delivers a reversible capacity of 1124 mAh/g at 0.1C and superior cycling stability with an 87.4% capacity retention after 200 cycles at 1C. The 1.5 A h pouch-type full-cell tests further demonstrate good cycling stability and high rate performance at 4C under an electrode density of 1.6 g cm−3 and areal capacity loading of 3.53 mAh cm−2. This work paves a new way for the rational design of Si-based anode materials for high-energy and high-power LIBs.

Hybrid surface coating layers comprising boron and phosphorous compounds on LiNi0.90Co0.05Mn0.05O2 cathode materials to ensure the reliability of lithium-ion batteries

High-energy lithium-ion batteries (LIBs) have undergone significant technological advancements in response to the expanding market for electric vehicles (EVs). Ni-rich layered cathode materials (LiNixCo1-x-yMn1-x-yO2, x ≥ 0.8) are a viable option because of their high reversible capacity over 200 mAh/g. However, the inherent challenges of Ni-rich cathodes include the occurrence of residual lithium, side reactions, and structural instability. Herein, we propose a hybrid surface coating of boron and phosphorous on a LiNi0.9Co0.05Mn0.05O2 (NCM955) cathode material to minimise the side reactions and enhance the structural stability. The hybrid surface coating on NCM955 provides an excellent discharge capacity of 180 mAh/g at 5 C-rate compared to the bare NCM955 capacity of 159 mAh/g. After 300 cycles, the coated NCM955 retained 84% of its capacity, while the uncoated retained only 46%. The improvement can be attributed to the enhanced lithium-ion diffusion achieved through hybrid coating, as confirmed by impedance measurements and cyclic voltammetry analysis. TEM and XPS analyses were performed to validate the presence of the coating layer, confirming the presence of the desired material on the surface. This study provides practical guidance for designing highly reliable, high-capacity cathode materials for use in EV applications.

Doped micro-silicon and vanadium carbide MXene composite as anode for high stability and high capacity Li-ion batteries

The demand for high-energy lithium-ion batteries (LIBs) has been rising exponentially. Silicon (Si) is gaining increased attention and popularity as an anode material due to its high theoretical capacity (4200 mAhg−1, Li4.4Si) and ample abundance, but the huge volume expansion of Si restricts its use in practical applications. Herein, we propose a composite consisting of nitrogen (N) and phosphorus (P) doped micron Si/graphite with vanadium carbide (V2C) MXene, which effectively helps to buffer the mechanical stresses initiated by the volume expansion of Si. The lithium storage specific capacity of the composite is 2003 mAhg−1 (based on the weight of Si) after a long-term cycling of 500 cycles (1C rate) along with a good high rate performance. The improved performance of the composite electrode can be attributed to V2C as well as N/P doping, which significantly enhance the electron/ion conduction pathways. Also, low-cost micron Si can provide high tap density in practical applications where volumetric performance is desired. Thus, this work provides an approach to develop high-performance micron Si-based materials for LIBs.

Silicon-carbon anode with high interfacial stability by a facile thermal reaction involving alkaline nitrogenous carbon source for lithium ion batteries

Silicon‑carbon composites are considered one of the most promising anodes for high-energy lithium-ion batteries. In this work, NC@Si nanospheres were prepared as silicon‑carbon anode materials for lithium-ion batteries by using an alkaline nitrogenous carbon source (polydopamine, PDA) to induce the anchoring of ultra-fine and high-purity SiO2 quantum dots onto a carbon matrix, followed by a magnesium thermal reduction treatment. The small volume expansion of silicon quantum dots (<10 nm) in NC@Si nanospheres and the thin Si3N4 outerwear formed on Si quantum dots due to the diffusion of N atoms and the local high temperature of magnesium heat synergistically ensure the structural integrity of NC@Si nanospheres and inhibit the excessive formation of SEI. The multi-point solid electrical contact between the silicon quantum dots and the nitrogen-doped carbon matrix provides sufficient conductive channels for fast Li+ diffusion and charge transfer. The as-prepared NC@Si anode exhibits a specific capacity of 497.2 mAh g−1 at 0.1 A g−1 with a capacity retention of 75.4% after 100 cycles, demonstrating a stable cycling performance. In the NC@Si||LFP full cell, the anode maintains a reversible capacity of 260.8 mAh g−1 after 80 cycles. The investigation of NC@Si composite anode proves that the silicon‑carbon anode by a facile thermal reaction involving alkaline nitrogenous carbon source can effectively improve the defects of silicon, offering the possibility of commercial application of silicon-based anode.

Optimization of hybrid energy management system based on high-energy solid-state lithium batteries and reversible fuel cells

Integrating a high power source, like a super capacitor (SCAP), and a lithium-ion battery (LIB) for electric vehicle (EV) applications yields achievement improvements, including maximum reliability, long lifetime (LT), small size, and competitive pricing for the overall source. A hybrid energy storage system (ESS) controlled by an intelligent energy management strategy (EMS) may be substantially included in multi-source EV design and development. Therefore, this paper proposes a hybrid chimp optimization algorithm (ChOA) and Levy walk technique to create an optimum EMS. The proposed technique reduces battery power (BP) stress and increases the LT, which is accomplished by using a hybrid ChOA-Levy walk (ChOA-LW) optimization algorithm with a rule-based approach in accordance with understanding the performance of LIB and SCAP. In order to optimize the rule-based EMS's control settings, the latter strategy is suggested. The control approach can be implemented online once the offline optimization procedure is finished. The presented technique is evaluated via simulation and on an experimental platform by means of a power emulator testbed of a LIB/SCAP hybrid ESS. In terms of BP stress and LT, the findings are compared with a conventional rule-based approach and a mono-source containing a regular high-power LIB. Results obtained demonstrate the effectiveness of the suggested technique, which enables the requested performance to be satisfied with better energy utilization. The assessment results also show notable LT improvements for the LIB, an improvement of up to 19% over the mono-source in reference to a conventional single cell LIB.

A strategy of boosting the effect of carbon nanotubes in graphite-blended Si electrodes for high-energy lithium-ion batteries

High capacity silicon (Si) has been added in graphite electrodes to overcome the theoretical capacity limit of the carbonaceous anode. However, different active materials that store Li+ ions via intercalation and alloying mechanisms are prone to suffer electrical disconnection due to the large gap derived from their different volume shrinkage ratios during delithiation. Herein, to address this poor compatibility on graphite-blended Si composite electrode (Gr-SC), a strategic usage of carbon nanotubes (CNTs) as electric bridge between graphite and Si is investigated through the comparison of three different types of Si blended graphite anodes (Gr-SC, Gr-SC with CNTs as additive, and Gr-MSC having implanted multi-walled CNTs on Si). Among the comparison group, the selectively located MW-CNT around Si in Gr-MSC exhibits outperformed capacity retention (98.4 %) and faster charge transfer kinetics after 50 cycles in a half cell, demonstrating a great compatibility between graphite and Si. This study presents a comprehensive understanding on the role of CNTs as an electric bridge on the electrode exploiting multiple Li storage mechanisms which undergo dissimilar volume change.

A Phosphorofluoridate-Based Multifunctional Electrolyte Additive Enables Long Cycling of High-Energy Lithium-Ion Batteries.

Ni-rich layered oxides are regarded as key components for realizing post Li-ion batteries (LIBs). However, high-valence Ni, which acts as an oxidant in deeply delithiated states, aggravates the oxidation of the electrolyte at the cathode, causing cell impedance to increase. Additionally, the leaching of transition metal (TM) ions from Ni-rich cathodes by acidic compounds such as Brønsted-acidic HF produced through LiPF6 hydrolysis aggravates the structural instability of the cathode and renders the electrode-electrolyte interface unstable. Herein, we present a multifunctional electrolyte additive, bis(trimethylsilyl) phosphorofluoridate (BTSPFA), to attain enhanced interfacial stability of graphite anodes and Ni-rich cathodes in Li-ion cells. BTSPFA eliminates the corrosive HF molecules by cleaving silyl ether bonds and enables the formation of a polar P-O- and P-F-enriched cathode electrolyte interface (CEI) on the Ni-rich cathode. It also promotes the creation of a solid electrolyte interphase composed of inorganic-rich species, which suppresses the reduction of the electrolyte during battery operation. The synergistic effect of the HF scavenging ability of BTSPFA and the stable BTSPFA-promoted CEI effectively suppresses the TM leaching from the Ni-rich cathode while also preventing unwanted TM deposition on the anode. LiNi0.8Co0.1Mn0.1O2/graphite full cells with 1 wt % BTSPFA exhibited an enhanced discharge capacity retention of 79.8% after 500 cycles at 1C and 45 °C. These unique features of BTSPFA are useful for resolving the interfacial deterioration issue of high-capacity Ni-rich cathodes paired with graphite anodes.