Next-generation Lithium-ion Batteries Research Articles

Lithium insertion/extraction mechanism in Mg2Sn anode for lithium-ion batteries

Due to its high capacity and excellent voltage properties, the Mg2Sn intermetallic phase is considered a promising anode material for next-generation lithium-ion batteries. However, the rapid capacity loss with cycling presently limits the application of Mg2Sn-based anodes. In this work, the Mg2Sn intermetallic phase was synthesized via a conventional casting method, and mechanisms of lithium ions intercalation into Mg2Sn alloy anodes were systematically studied. Density functional theory (DFT) calculations and electrochemical analyses identified two pathways involving four electrochemical reactions for Li+ intercalation/extraction in the Mg2Sn phase. The first pathway involves the insertion reaction of lithium ions into the octahedral sites of the Mg2Sn face center cubic (FCC) matrix, whilst the second involves the substitution of Mg by Li ions (releasing Mg metal). Furthermore, ex-situ EIS analysis and DFT calculations verified that adjusting the cut-off voltage range could control the reaction pathways. Excessively high or low cut-off voltages adversely impact the stability of the Mg2Sn anode. At cut-off voltages between 0.1 and 1 V, Mg2Sn anodes show very good capacity retention (78 % after 50 cycles), benefiting from the minimized formation of metallic Mg and Sn phases.

Interface chemical reconstruction with residual lithium compounds on nickel-rich cathode by nonstoichiometrical MoO3-x coating enables high stability

The layered lithium nickel-rich cathodes have become one of the most promising candidates for next-generation lithium-ion batteries with high energy density, However, the nickel-rich cathode suffers from a rapid decay of capacity due to their intrinsic instability and undesirably residual lithium compounds originated from LiNiO2 structural changes on the surface, hindering large-scale commercial application. Herein, a continuous and uniform oxygen vacancy enriched-MoO3-x coating was successfully synthesized and reacted residual lithium compounds as a functional layer on the cathode. Such chemically reconstructed coating (Li2MoO4) strategy endows the 1 wt% MoO3-x coated NCA cathode with a fast Li+ ions transport and enhanced structural stability, leading to an outstanding discharge capacity of 214.0 mAh g−1 at 0.1C (1C = 270 mA g−1), a better capacity retention of 80.3 % after 120 cycles at 0.5C, and an excellent high rate capability of 120 mAh g−1 at 5C cycled in voltage range of 2.75 V–4.3 V. This work provides an effective strategy to modulate surface structure towards advanced Ni-rich cathodes for high-performance lithium-ion batteries.

Boosting the Electrochemi,cal Performance of Primary and Secondary Lithium Batteries with Mn-Doped All-Fluoride Cathodes.

Transition metal fluorides are potentially high specific energy cathode materials of next-generation lithium batteries, and strategies to address their low conductivity typically involve a large amount of carbon coating, which reduces the specific energy of the electrode. In this study, MnyFe1-yF3@CFx was generated by the all-fluoride strategy, converting most of the carbon in MnyFe1-yF3@C into electrochemical active CFx through a controllable NF3 gas phase fluorination method, while still retaining a tightly bound graphite layer to provide initial conductivity, which greatly improved the energy density of the composite. This synergistic effect of nonfluorinated residual carbon (∼11%) and Mn doping ensures the electrochemical kinetics of the composite. The loading mass of the active substance had been increased to 86%. The theoretical and actual discharge capacity of MnyFe1-yF3@CFx composite was up to 765 mAh g-1 (pure FeF3 is 712 mAh g-1) and 728 mAh g-1, respectively. The discharge capacity at the high-voltage (3.0 V) platform was more than three times higher than that of the non-Mn-doped composite (FeF3@CFx).

Lithium-Ion Dynamic and Storage of Atomically Precise Halogenated Nanographene Assemblies via Bottom-Up Chemical Synthesis.

Graphene has received much scientific attention as an electrode material for lithium-ion batteries because of its extraordinary physical and electrical properties. However, the lack of structural control and restacking issues have hindered its application as carbon-based anode materials for next generation lithium-ion batteries. To improve its performance, several modification approaches such as edge-functionalization and electron-donating/withdrawing substitution have been considered as promising strategies. In addition, group 7A elements have been recognized as critical elements due to their electronegativity and electron-withdrawing character, which are able to further improve the electronic and structural properties of materials. Herein, we elucidated the chemistry of nanographenes with edge-substituted group 7A elements as lithium-ion battery anodes. The halogenated nanographenes were synthesized via bottom-up organic synthesis to ensure the structural control. Our study reveals that the presence of halogens on the edge of nanographenes not only tunes the structural and electronic properties but also impacts the material stability, reactivity, and Li+ storage capability. Further systematic spectroscopic studies indicate that the charge polarization caused by halogen atoms could regulate the Li+ transport, charge transfer energy, and charge storage behavior in nanographenes. Overall, this study provides a new molecular design for nanographene anodes aiming for next-generation lithium-ion batteries.

High-Performance Anode Material Based on Zinc Naphthalocyanine/Graphene Composite.

Transition metal oxides are a potential anode material owing to their high theoretical capacity. Nonetheless, their large volume changes and low electrical conductivities lead to poor cycling performance and rate capabilities. In this article, an effective strategy is proposed and developed for preparing a ZnO/N-doped graphene composite (ZnNc/GO-5). The key point of this strategy is to use zinc tetra tert-butyl-naphthalocyanine (ZnNc) as a codoped source of N atoms and zinc ions, and graphene oxide (GO) which is combined with ZnNc by π-π deposition as a carbon matrix. After calcination, ZnO microcrystals coated with N-doped graphene are obtained. The unique features of the composite and synergistic effect between N-doped reduced graphene oxide and ZnO microcrystals enable good electrochemical performance by the composites when used in lithium-ion batteries. As an anode material, the as-synthesized ZnNc/GO-5 composite delivers a high first capacity of 1942.9 mAh g-1 and excellent cyclic stability of 861.4 mAh g-1 after 150 cycles at 100 mA g-1. This strategy may offer a new method of designing the anode materials of lithium-ion batteries and promote the practical use of organic molecules in next-generation lithium-ion batteries.

Surface Pinning of Mn by Oxidation State Control for the Synthesis of Cobalt-Free, Ni-Rich, Core/Shell Structured Cathode Materials.

Motivated by the increasing cost, environmental concerns, and limited availability of Co, researchers are actively seeking alternative cathode materials for lithium-ion batteries. A promising strategy involves structure-modified materials, such as a NiMn core/shell system. This design leverages the high energy density of a Ni-rich core while employing an Mn-rich shell to enhance interfacial stability by suppressing unwanted reactions with the electrolyte. This approach offers improved cycling stability and reduced reliance on Co. However, the interdiffusion of Mn ions between the core and shell remains a significant challenge during synthesis. This work presents a facile approach to address the issue of Mn interdiffusion in core/shell cathode materials. The study demonstrates that partial oxidation of the precursor during the drying stage effectively enhances the Mn oxidation state. This strategy successfully suppresses Mn interdiffusion during subsequent calcination, leading to the preservation of the core/shell architecture in the final cathode material. This optimized structure mitigates interfacial reactions, enhances chemomechanical properties, and reduces crosstalk, a major contributor to rollover failure. This work presents a novel approach for synthesizing high-performance core/shell cathode materials for next-generation lithium-ion batteries.

Multilayer boron doped Si@SiOx/C from Si-Ca alloy for lithium-ion battery anodes

SiOx has been considered as a promising anode for next-generation lithium-ion batteries. However, the poor rate performance caused by the low electrical conductivity is a bottleneck of its application. Approaches involving carbon composites, boron doping and two-dimensional structure have been pursued to improve the electrical conductivity. In this work, through the combination of these strategies, a multilayer boron doped Si@SiOx/C composites are fabricated by a chemical exfoliation of CaSi2 with B2O3 and CaCO3. The production exhibits favorable properties for lithium-ion battery anodes, such as proper specific surface area, complete multilayer structure, boron doped and carbon composite structure. The as-obtained B-Si@SiOx/C-700 delivers a capacity of 659.3 mAh g−1 after 500 cycles at 1 A g−1. Especially, at 4 A g−1, the capacity retention of the B-Si@SiOx/C-700 anode is still 40.9 % of its average discharge capacity at 0.2 A g−1. The capacitive contribution to the total Li+ storage capacity for the B-Si@SiOx/C-700 electrode is 83.6 % at 1.0 mV s−1. This work presents a simple and efficient strategy to construct a multilayer doped structure to improve electrochemical properties.

Borate modified Co-free LiNi0.5Mn1.5O4 cathode material: A pathway to superior interface and cycling stability in LNMO/graphite full-cells

Cobalt-free LiNi0.5Mn1.5O4 (LNMO) holds great promise as a next-generation cathode material for high-energy and high-power density lithium-ion batteries (LIBs), making it a key contender for large-scale energy storage systems (ESS) and transportation applications. Despite its potential, the commercial utilization of LNMO has been impeded by its rapid capacity deterioration attributed to an unstable LNMO/electrolyte interface caused by the intrinsically high operating voltage of LNMO. Here, we present a pragmatic and scalable strategy to improve the LNMO/electrolyte interface through borate-based surface coating of the LNMO. Optimizing the coating process yielded high-rate capability and stable LNMO/electrolyte interface analyzed by extended float tests. Borate-LNMO materials show superior cycling stability at 25 °C and 45 °C, attributed to a robust cathode electrolyte interphase (CEI) formation. The bare LNMO and 0.25-B2O3-LNMO demostrated a cycling stability of around 41.20 % and 62.50 % respectively after 1000 cycles in LNMO/graphite full-cells. Post-mortem X-ray photoelectron spectroscopy (XPS) analysis revealed fewer side reaction products on borate-LNMO cathodes compared to bare LNMO. Additionally, scanning electron microscopy (SEM) revealed a thicker and denser solid-electrolyte interphase (SEI) layer on cycled graphite anodes from bare LNMO cells, while a thin and robust SEI was observed on graphite from borate-LNMO cells. Finally, we have conclusively demonstrated that the primary aging mechanism in LNMO/graphite full cells stems from the instability at the LNMO/electrolyte or/and graphite/electrolyte interface, rather than material-related degradation phenomenon. These compelling outcomes underscore the potential of cathode material surface coating in general and especially of borate coating on LNMO as a promising and cost-effective enabler for the use of LNMO in next-generation 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.

Influence of defects on enhancing lithium diffusivity in crystalline silicon anodes for fast charging lithium-ion batteries

The energy storage sector requires high capacity, long cycling life batteries. Silicon (Si) arises as a pivotal anode material for next-generation lithium-ion batteries owing to its exceptional capacity. However, challenges arise from lithium interactions, causing volumetric expansion and structural concerns like cracking. Si anodes also exhibit diverse phenomena during lithiation, influenced by crystal orientations. A thorough comprehension of the (de)lithiation process is essential to address challenges, despite existing gaps in knowledge, with strategic design and complementary materials, offering potential solutions by enhancing ion mobility and minimizing diffusion barriers. Here we have developed and applied first-principles simulations to offer fundamental insights into atomic interactions, providing a realistic atomistic representation of lithiation processes. Our simulations systematically incorporate Li+ into Si and Si- nitrogen vacancies (NV) orientations, and evaluation between Si and Si-NV (110) indicates a more favorable behavior in ionic diffusion for Si-NV(110), with a range of 2.55 × 10−3 to 1.64 × 10−2 (cm2/s) and a 15 % decrease in volume expansion. Our results explain the ternary Si–Li–N electrode materials and the identification of optimal site disorders to maximize the rate of Li+ diffusion in crystalline Si anodes.

Ternary composites of poly(vinylidene fluoride-co-hexafluoropropylene) with silver nanowires and titanium dioxide nanoparticles as separator membranes for lithium-ion batteries

In the realm of polymer composites, there is growing interest in the use of more than one filler for achieving multifunctional properties. In this work, a composite separator membrane has been developed for lithium-ion battery application, by incorporating conductive silver nanowires (AgNWs) and titanium dioxide (TiO2) nanoparticles into a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer matrix. The composite membranes were manufactured by solvent casting and thermally induced phase separation, with total filler content varying up to 10 wt%. The ternary composites composites present improved mechanical characteristics, ionic conductivity and lithium transfer number compared to the neat polymer matrix. On the other hand, the filler type and content within the composite has little bearing on the morphology, polymer phase, or thermal stability. Once applied as a separator in lithium-ion batteries, the highest discharge capacity value was obtained for the 5 wt% AgNWs/5 wt% TiO2/PVDF-HFP membrane at different C-rates, benefiting from the synergetic effect from both fillers. This work demonstrates that higher battery performance can be achieved for next-generation lithium-ion batteries by using separator membranes based on ternary composites.

Enhancing the Electrochemical Performances of Disordered Li1.23Ni0.3Nb0.3Fe0.16O0.85F0.15 Cathode Material for Lithium-Ion Batteries by LiNbOx Coating.

For the next generation of lithium-ion batteries (LIBs), it is primary to seek high capacity and long-lifetime electrode materials. Li-excess disordered rock-salt structure (DRS) cathodes have gained much attention due to their high specific capacity. However, Li-excess can lead to a decrease in the structural stability of an electrode material. A new Li-rich DRS oxyfluorides, Li1.23Ni0.3Nb0.3Fe0.16O0.85F0.15 (F0.15) with a series amounts of LiNbOx (LN) coating (0, 5, 10, and 15 wt % denoted as F0.15-LN0, F0.15-LN5, F0.15-LN10, and F0.15-LN15, respectively), are successfully synthesized and evaluated as cathode materials in LIBs. Among them, F0.15-LN10 exhibits the highest initial discharge specific capacity of 296.1 mAh g-1 (at a current density of 20 mA g-1) with the capacity retention rate of 14% higher than that of the uncoated F0.15 after 80 cycles. Even at 300 mA g-1, F0.15-LN10 still delivers the highest discharge specific capacity of 130 mAh g-1. After 20 cycles, the charge-transfer impedance of F0.15-LN10 remained the smallest. The characterizations indicate that LN coating reduces the surface polarization of the cathode materials, slows the interfacial side reactions between the electrolyte and the electrode, and speeds up the Li+ diffusion. These results demonstrate that LN coating is an effective strategy to improve the electrochemical performance.

Realization of high-capacity coulombic efficiency in sodium alginate/carbon nanotube double network coated Si-anode for lithium-ion batteries

Silicon (Si) is considered as one of the most promising anodes for the next-generation lithium-ion batteries (LIBs) owing to its ultra-high specific capacity, low redox potential and the second abundance of elements in the earth's crust. However, drastic volume change will directly cause electrode pulverization, thus leading to low initial coulombic efficiency (ICE) and terrible cycling stability. In this work, a sodium alginate (SA)‑carbon nanotube (CNT) derived double carbon-coated Si composite (SA-CNT@Si) was prepared through freeze-drying technique followed by high-temperature carbonization, where SA was utilized to encase Si nanospheres, with CNT serving as the conductive framework that interconnects Si spheres. These composites exhibit improved electrical conductivity and stability throughout the charge and discharge cycles when employed as the anodes in LIBs, demonstrating superior electrochemical properties. The SA-CNT@Si electrode with a mass ratio of Si: SA: CNT = 5: 1: 0.75, achieved a first discharge specific capacity of 2200.8 mAh g−1 at a current density of 500 mA g−1 (with the initial three cycles at 100 mA g−1), along with an ICE of 86.2%. Even after 500 cycles, it maintained a capacity of 607 mAh g−1. This study presents a novel approach to designing Si-based anode materials characterized by both high electrical conductivity and structural stability.

Surface and Bulk Stabilization of Silicon Anodes with Mixed-Multivalent Additives: Ca(TFSI)2 and Mg(TFSI)2.

Silicon is drawing attention as an emerging anode material for the next generation of lithium-ion batteries due to its higher capacity compared with commercial graphite. However, silicon anions formed during lithiation are highly reactive with binder and electrolyte components, creating an unstable SEI layer and limiting the calendar life of silicon anodes. The reactivity of lithium silicide and the formation of an unstable SEI layer are mitigated by utilizing a mixture of Ca and Mg multivalent cations as an electrolyte additive for Si anodes to improve their calendar life. The effect of mixed salts on the bulk and surface of the silicon anodes was studied by multiple structural characterization techniques. Ca and Mg ions in the electrolyte formed relatively thermodynamically stable quaternary Li-Ca-Mg-Si Zintl phases in an in situ fashion and a more stable and denser SEI layer on the Si particles. These in turn protect silicon particles against side reactions with electrolytes in a coin cell. The full cell with the mixed cation electrolyte demonstrates enhanced calendar life performance with lower measured current and current leakage in comparison to that of the baseline electrolyte due to reduced side reactions. Electron microscopy, HR-XRD, and solid-state NMR results showed that electrodes with mixed cations tended to have less cracking on the electrode surface, and the presence of mixed cations enhances cation migration and formation of quaternary Zintl phases stabilizing the bulk and forming a more stable SEI in comparison to baseline electrolyte and electrolyte with single multivalent cations.

A simple and effective approach to relieve stress and enhance cyclability of Si-based materials toward high-energy lithium-ion batteries

Silicon-based materials are promising anodes to keep up with the demands for next-generation lithium-ion batteries in the coming decades owing to their ultrahigh theoretical capacities. However, the severe volume changes and mechanical fractures during cycling greatly hinder their way to commercialization. So far, it still remains a great challenge to develop advanced Si-based electrodes with high mechanical stability and remarkable electrochemical properties. In this work, we propose a simple and effective strategy to encapsulate Si@SiOx particles into B, N co-doped carbon nanotubes (BNCNTs) to develop Si@SiOx@BNCNT electrode for enhanced lithium storage. The SiOx layer upon Si particle is designed to mitigate the volume expansion of Si and maintain the particle integrity. Finite element analysis demonstrates that BNCNTs with high mechanical strength can further relieve the internal stress induced by Si expansion upon lithiation. The double restraint effect from SiOx layers and BNCNTs on the Si particles contributes to excellent resistance to structural degradation, enabling high stability and desirable electrochemical performance of Si@SiOx@BNCNT electrode. This strategy provides great opportunities for the practical application of Si-based anodes in high-energy lithium-ion batteries.

Enhancing compatibility between LiNi0.8Co0.1Mn0.1O2 and LiPF6-based electrolyte via bis(trimethylsilyl)oxalate additive

LiNi0.8Co0.1Mn0.1O2 (NCM811)-layered oxide has a high discharge capacity and is considered as an alternative cathode for next-generation high-energy density lithium-ion batteries (LIBs). However, the corrosion of LiPF6-based electrolyte and the poor stability of the cathode solid electrolyte interface (CEI) film pose a threat to the cyclic stability of the battery. Herein, bis(trimethylsilyl)oxalate (DTMSO) is introduced as a novel multifunctional electrolyte additive to construct a stable CEI film and improve the high temperature tolerance of NCM811/Li cells. Results show that DTMSO can effectively scavenge HF resulted from trace water and high temperature, preventing the detrimental effects of HF on CEI film and NCM811 electrode material. More than that, DTMSO can react with LiPF6 to form conducive lithium tetrafluoro(oxalate)phosphate (LiTFOP) when undergoes the ordeal of high temperature (55 °C) for 24 h. The as-generated LiTFOP aids in the construction of a stable and conductive CEI film that is rich in LiF and LixPOyFz. Benefit from these characteristics, DTMSO additive enables effective protection of the electrode material and mitigates capacity decay in the battery, ultimately facilitating good cycling performance and improving ability to resist high temperature within a certain time. As a result, the capacity retention rate of the NCM811/Li cell after 100 cycles is increased from 67.8% to 85.6%, when the test condition is shelved at 55 °C for 24 h and then changed back to cycling at 25 °C. This work provides a viable strategy for the development of electrolytes compatible with nickel-rich cathode and is of great significance for the development of advanced LIBs.

Constructing oxygen-deficient shell on Li-rich cathodes by spark plasma sintering for high-performance lithium-ion batteries

Lithium-rich layered oxides (LROs) are considered as promising cathodes in building next-generation lithium-ion batteries (LIBs) with superior charge-discharge capacity. Nevertheless, LROs are confronted with irreversible oxygen loss accompanied with surface-to-bulk degradation upon cycling. To inhibit the oxygen release and to increase the lifespan of LROs, we report on an innovative strategy to rapidly construct an ultrathin oxygen-deficient shell layer covering the surface of LROs’ particles via a sparking plasma sintering (SPS) technique. It is demonstrated that the inner structure of the LROs’ particles is maintained, whereas the surface of the particles forms a thin shell (∼5 nm) consisting of a considerable amount of oxygen vacancies. Benefitting from the existence of an oxygen-deficient shell, the cathode activation is facilitated and the oxygen loss is suppressed, leading to enhanced capacity and prominent cyclability under long cycling. The modified LRO exhibits outstanding electrochemical performance, delivering a maximum capacity of 187.67 mAh g−1 and a capacity retention of 95.71% after 200 cycles at 250 mA g−1. Our work evidences that SPS is a fast and effective approach to construct oxygen-deficient shell on LRO cathodes for high-performance LIBs.

Transforming Residual Lithium Compounds on the LiNi0.8Mn0.1Co0.1O2 Surface into a Li-Mn-P-O-Based Composite Coating for Multifaceted Improvements.

LiNi0.8Mn0.1Co0.1O2 (NMC811) is the most promising cathode material for next-generation lithium-ion batteries (LIBs). However, the chemical instability of the material during air exposure leads to the formation of residual lithium compounds (RLCs: LiOH and Li2CO3) on the surface and inhibits its practical application. Here, we propose a chemical conversion process to remove RLCs by utilizing them and forming a hybrid coating layer on the surface of NMC811 that contains Li3PO4, LiMn2O4, and LiMnPO4 phases, yielding multifaceted benefits. The hybrid layer on the surface protects the material from undesirable side reactions. It improves the cycle life of NMC811 by retaining 80% of its initial capacity after 300 cycles and 66% after 500 cycles at a 0.5C rate in the operating voltage of 3.0-4.3 V. The process enables high-voltage (4.7 V vs Li+/Li) operation by stabilizing the electrode-electrolyte interface, reduces the degree of cationic disorder and the voltage polarization for phase transitions, improves Coulombic efficiency and ion diffusion kinetics, and minimizes the secondary particle crack formation over long-term cycling. In fact, the coating reduces the detrimental effects of RLCs, leaves the surface for better Li+ transport, and hence significantly improves the electrochemical performance of NMC811.

Ladderlike polysilsesquioxanes derived dual-carbon-buffer-shell structural silicon as stable anode materials for lithium-ion batteries

Silicon-carbon (Si/C) composite materials have been proven to be one of the most promising anode materials for the next generation of lithium-ion batteries (LIBs) due to their high theoretical capacity. However, the substantial volume changes during alloying/dealloying processes have posed significant challenges to the working lifespan of Si-based anodes. In this study, we designed a dual-carbon-layer-structured Si composite anode material (DCS-Si). Using ladderlike polysilsesquioxanes as a precursor, we employed a zinc thermal reaction to internally reduce the Si–O–Si framework to Si0. Simultaneously, the phenyl groups directly connected to Si atoms served as a carbon source for the internally dense coating layer. The obtained product underwent further coating controllable pyrolysis reactions to form an external carbon coating layer. As anode for LIBs, DCS-Si delivered a reversible specific capacity exceeding 1000 mAh g−1. Even after 1350 cycles at a current density of 0.3 A g−1, the specific capacity remained above 500 mAh g−1. Moreover, even under a high current density of 3 A g−1, after nearly 1000 cycles, the capacity retention rate still exceeded 70%. Further testing of the full cell also indicated that DCS-Si is a highly promising high-energy-density anode, with potential applications in future commercial lithium-ion batteries.

Electrolyte design for robust gradient solid-electrolyte interfaces to enable high-performance silicon anodes for pouch batteries

Silicon (Si) anodes has emerged as an ideal anode for the next generation of lithium-ion batteries owing to its high specific capacity. Nevertheless, Si particles undergo large volume expansion during cycling, inducing the continuous fragmentation/re-formation of the solid-electrolyte interphase (SEI) layer, which leads to rapid capacity decay and low Coulombic efficiency in EC-based carbonate electrolytes. Herein, a weakly solvating electrolyte with boric acid tris(hexafluoroisopropyl) ester (BTHE), 2,2,2-trifluoroethyl methyl carbonate (FDEC), and fluoroethylene carbonate (FEC) is developed to build a stable SEI. BTHE is introduced as a functional additive, which is induce anion and fluorinated solvent to form a gradient rigid–soft coupling SEI layer. In contrast to other anion-derived interfaces, weakly solvating electrolyte has been proven to construct a highly robust and stable –CF3-rich-organic outer layer and LiF-rich inner layer SEI on the Si anodes, resulting in approximately 99.9 % ultra-high Coulombic efficiency and ultra-high areal capacity (∼8.1 mAh cm−2). Beyond proof of concept, a 2.68 Ah Si||LiNi0.8Mn0.1Co0.1O2 pouch cell has an impressive 84.3 % capacity retention after 1000 cycles and could work normally at temperatures ranging from −30 °C to 100 °C based on this electrolyte, representing a pioneering report in pouch cells incorporating Si anodes.