Nickel-rich LiNi0 Research Articles

Understanding the Carbon Additive/Sulfide Solid Electrolyte Interface in Nickel-Rich Cathode Composites and Prioritizing the Corresponding Interplay between the Electrical and Ionic Conductive Networks to Enhance All-Solid-State-Battery Rate Capability.

All-solid-state lithium batteries, including sulfide electrolytes and nickel-rich layered oxide cathode materials, promise safer electrochemical energy storage with high gravimetric and volumetric densities. However, the poor electrical conductivity of the active material results in the requirement for additional conducive additives, which tend to react negatively with the sulfide electrolyte. The fundamental scientific principle uncovered through this work is simple and suggests that the electrical network benefits associated with the introduction of short-length carbons will eventually be overpowered by the increase in bulk resistance associated with their instability in the sulfide electrolyte. However, applying just the right amount of short carbon fibres minimizes degradation of the sulfide solid electrolyte and maximizes the electron movement. Therefore, we propose the application of a low-weight-percent carbon nanotubes (CNTs) coating on the nickel-rich cathode LiNi0.8Co0.1Mn0.1O2 (NCM811) along with large-aspect-ratio carbon nanofibers (CNFs) as the primary conductive additive. When only 0.3 wt % CNTs was utilized with 4.7 wt % CNFs, an initial Coulombic efficiency of 83.55% at 0.05C and a notably excellent capacity retention of 90.1% over 50 cycles at 0.5C were achieved along with a low ionic resistance. This work helps to confirm the validity of applying short carbon pathways in sulfide-electrolyte-based cathode composites and proposes their combination with a larger primary carbon additive as a solution to the ongoing all-solid-state battery rate and instability issues.

Lithium Borate Polycarbonates for High-Capacity Solid-State Composite Cathodes.

Improving composite cathode function is key to the success of the solid-state battery. Maximizing attainable cathode capacity and retention requires integrating suitable polymeric binders that retain a sufficiently high ionic conductivity and long-term chemo-mechanical stability of the cathode active material-solid-electrolyte-carbon mixture. Herein, we report block copolymer networks composed of lithium borate polycarbonates and poly(ethylene oxide) that improved the capacity (200 mAh g-1 at 1.75 mA cm-2) and capacity retention (94 % over 300 cycles) of all-solid-state composite cathodes with nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode active material, Li6PS5Cl solid electrolyte, and carbon. Tetrahedral B(OR)2(OH)2 - anions immobilized on the polycarbonate segments provide hydrogen-bonding chain crosslinking and selective Li-counterion conductivity, parameterized by Li-ion transference numbers close to unity (tLi+~0.94). With 90 wt % polycarbonate content and a flexible low glass transition temperature backbone, the single-ion conductors achieved high Li-ion conductivities of 0.2 mS cm-1 at 30 °C. The work should inform future binder design for improving the processability of cathode composites towards commercializing solid-state batteries, and allow use in other cell configurations, such as lithium-sulphur cathode designs.

Stable and Fast Ion Transport Electrolyte Interfaces Modified with Novel Fluorine- and Nitrogen-Containing Solvents for Ni-Rich Cathode Materials.

Ternary nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811) is recognized as a cathode material with a promising future, attributed to its high energy density. However, the pulverization of cathode particles, structural collapse, and electrolyte decomposition are closely associated with the fragile cathode-electrolyte interphases (CEI), which seriously affect the electrochemical performances of ternary high-nickel materials. In this paper, fluorine- and nitrogen-containing methyl-2-nitro-4-(trifluoromethyl)benzoate (MNTB) was selected, which was synergistically regulated with fluoroethylene carbonate (FEC) to generate a robust CEI film. The preferential decomposition of MNTB/FEC results in the formation of an inorganic-rich (Li3N, LiF, and Li2O) CEI film with uniformly dense and stable characteristics, which is conducive to the migration of Li+ and the stability of the NCM811 structure and enhances the cycling stability of the battery system. Simultaneously, MNTB effectively suppresses the adverse reaction associated with increased polarization caused by higher interface impedance due to conventional single FEC additives, further improving the rate capability of the battery. Moreover, MNTB/FEC can effectively eliminate HF, preventing its corrosion on the NCM811 cathode. Under the synergistic effect of MNTB/FEC, after 300 discharge cycles at a high cutoff voltage of 4.3 V and a current density of 1 C (2 mA cm-2), the discharge capacity of the NCM811||Li battery was 150.12 mA h g-1 with a capacity retention of 81.10%, while it was only 32.8% for the standard electrolyte (STD). The discharged capacity of the MNTB/FEC-containing battery was about 115.43 mA h g-1 at the high rate of 7 C, which was considerably higher than that of the STD (93.34 mA h g-1). In this study, the designed MNTB as a novel solvent synergistically regulated with FEC will contribute to the enhanced stability of NCM811 materials at high cutoff voltages and at the same time provide an effective modified strategy to enhance the stability of commercial electrodes.

Tổng hợp vật liệu LiNi0,9Mn0,05Co0,05O2 bằng phương pháp phản ứng pha rắn (NMC9.5.5-PR) ứng dụng chế tạo pin ion liti

Nickel-manganese-cobalt (NMC) transition metal oxide-based layered structural materials are evaluated a promising material for applications as cathode in lithium-ion batteries. In this study, we have successfully synthesized nickel-rich NMC material LiNi0.9Mn0.05Co0.05O2 by solid-state reaction method (NMC9.5.5- PR). The CR2032-type lithium-ion battery is also successfully fabricated from NMC material to serve the study of electrochemical properties. The NMC9.5.5-PR material exhibits outstanding discharge specific capacity when providing a maximum specific capacity of up to 212.4 mAh/g at a current density of 10 mA/g. However, the cycle efficiency survey results show that the NMC9.5.5-PR material has some disadvantages (only maintaining 81.6% of the discharge specific capacity after 50 continuous charge-discharge cycles at current density of 10 mA/g). These electrochemical properties indicate that it is necessary to further improve the cyclic efficiency of NMC9.5.5-PR material but preserving its outstanding electrical energy storage capacity. Successfully accomplishing this goal, we believe that NMC-9.5.5-PR or a material based on NMC9.5.5-PR will be one of the suitable materials to fabricate positive electrodes used in lithium-ion batteries.

Enhancement of the electrochemical properties of the nickel-rich cathode material LiNi0.815Co0.15Al0.035O2 by WO3 coating

Enhancement of the electrochemical properties of the nickel-rich cathode material LiNi0.815Co0.15Al0.035O2 by WO3 coating

Revealing the origin of enhanced structural stability for nickel-rich LiNi0.83Co0.11Mn0.06O2 cathodes in situ modified with multifunctional polysiloxane

Multifunctional polysiloxane (MPS) layer is elaborately constructed on the surface of LiNi0.83Co0.11Mn0.06O2 (NCM83) particles via in situ hydrolysis-polycondensation of tetraethyl orthosilicate. Impressively, optimal NCM83 (NCM83-2) electrode covered with average 7 nm-thickness of fresh MPS layer delivers improved capacity retention ratio of 81.8 % after 150 cycles at 25 °C and retains the value of 78.7 % after 200 cycles at 60 °C and 1.0 C. Moreover, NCM83-2 electrode presents lower polarization degree with sluggish growth of the capacity platform. The significant advantages of NCM83-2 can be interpreted by the fact that the MPS layer effectively mitigates microcracks generation by inhibiting phase transition and lattice oxygen loss. Moreover, the MPS protective layer suppresses the thickening of cathode electrolyte interphase film and boosts the structural stability of NCM83 electrode to optimize electrochemical properties. Therefore, this strategy may provide promising enlightenments for preserving structural integrity and improving interfacial stability of nickel-rich cathodes for lithium-ion batteries.

The trade-off characteristic between battery thermal runaway and combustion

Lithium iron phosphate (LFP) lithium-ion batteries are widely believed to be more thermally safe than nickel-rich layered LiNixCoyMnzO2 (NCM) batteries because LFP cathodes are more stable. However, LFP batteries have been reported to cause serious combustion accidents. The relationship between internal thermal runaway and external combustion in LFP and NCM batteries remain unclear. Herein, we found that there is a trade-off between thermal runaway within the battery and external combustion. Cathode oxidizability is linearly correlated with the intensity of thermochemical reactions within battery components. The nickel-rich LiNi0.9Co0.05Mn0.05O2|Graphite (NCM955|Gr) battery exhibits the most intense exothermic reactions and energy release due to the strong oxidation of its cathode, leading to the highest thermal runaway temperature of 862.4 °C within the battery. The LiFePO4|Graphite (LFP|Gr) battery with the weak cathode oxidizability shows the lowest temperature of 297.4 °C within the battery, but with the highest laminar flame speed of 55 cm s−1 outside the battery. The reason for this is that the LFP cathode rarely oxidizes the electrolyte, instead, the electrolyte reacts with the anode primarily, thereby generating substantial reductive gases and accumulating the explosion risks. This work provides the theoretical basis and data support for future battery selection and design.

Dual-modified LiNi0.8Co0.1Mn0.1O2 cathode materials with lithium conducting hybrid oligomer and single-walled carbon nanotube for improving electrochemical performance and thermal stability of lithium-ion batteries: A novel approach for high-power and high-safety applications

In this study, we investigated the synergetic effect of a novel lithium-ion conducting hybrid oligomer [N, N′-bismaleimide-4, 4′-diphenylmethane (BMI), lithiated trithiocyanuric acid (Li-TCA) and Jeffamine®-M1000 (JA®); Li-BTJ] coating layer on a nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material wrapped with highly electron-conductive single-walled carbon nanotubes (SWCNTs) to enhance electrochemical performance and thermal stability for high-power and high-safety lithium-ion batteries (LIBs). Morphological analyses using scanning electron microscopy/energy dispersive spectroscopy and transmission electron microscopy showed that the NCM811 active material surface was uniformly coated with a hybrid oligomer to form NCM811@Li-BTJ, which was subsequently wrapped with SWCNTs (NCM@Li-BTJ/SWCNT composite cathode). CR2032 coin-type cells with optimized NCM811@1 wt% Li-BTJ/0.2 wt% SWCNT composite electrodes delivered a significantly enhanced capacity retention (CR) of 90.1 % relative to that of bare NCM811 electrodes (CR: 82.1 %) at 1C for 200 cycles from 2.8 to 4.3 V (vs. Li/Li+). Electrochemical impedance spectroscopy and cyclic voltammetry revealed that this superior cycling performance resulted from a lower charge transfer resistance (Rct: 96.2 vs. 324.3 Ω) and a lower polarization voltage (∆V: 0.243 vs. 0.411 V vs. Li/Li+). The in-situ micro-calorimetric results presented the total heat generation (Qt) values of the coin cells with the delithiated NCM811@Li-BTJ and NCM@Li-BTJ/SWCNT electrodes at 5C and 35 °C were substantially lower by ~9.3 % and ~ 14.6 %, respectively, compared to the bare NCM811 counterpart, indicating that the surface modifications on the NCM811 active materials could prevent the LIBs' thermal instability. Furthermore, X-ray photoelectron spectroscopy studies revealed that the Li-BTJ hybrid oligomer coating layer effectively suppressed the formation of residual Li side products such as Li2CO3 evidently on the surface of the NCM811 active material particles, thereby inhibiting undesirable side reactions. Post-mortem analyses of the dual-modified NCM811 electrode after cycling revealed that the microstructure and particle morphology of the NCM composite cathode material were extensively maintained through the synergistic effects of the Li-BTJ ion-conductive and SWCNTs electron-conductive agents.

Highly stable nickel-rich cathode materials LiNi0.90Co0.05Mn0.05O2 with Mn concentration gradient for lithium-ion batteries

Ni-rich layered cathode materials (LiNixCoyMn1-x-yO2) have attracted much attention due to their high energy density and environmentally friendly advantages. However, the capacity fading and structural instability with the increase of Ni content are still the main problems restricting the commercialization of high nickel cathodes. In this paper, the method of co-precipitation and calcination is used to prepare LiNi0.90Co0.05Mn0.05O2 (CG-NCM5) with Mn concentration gradient, which the Ni content is decreasing from the core to the outer of CG-NCM5, while the Mn content is increasing. The CG-NCM5 has less Li/Ni mixing and a good layered structure. More importantly, the Mn-rich outer plays a key role in preventing the appearance of microcracks and enhancing the structure stability, because it can effectively suppress the volume change stemming from the phase transition during charge/discharge process. Meanwhile, the low Ni on the surface reduces the highly reactive Ni4+ that easily reacts with electrolyte, mitigates material surface degradation and accelerates lithium-ion transport. Therefore, it exhibits a superior reversible capacity of 191.4 mAh/gat 1C and a capacity retention of 83.7 % after 200 cycles in 2.7–4.3 V. These results indicate that Mn concentration gradient materials may provide a practical approach to highly stable nickel-rich cathode materials for lithium-ion batteries.

Anchoring Active Li Metal in Oriented Channel by In Situ Formed Nucleation Sites Enabling Durable Lithium-Metal Batteries.

Lithium metal is the ultimate anode material for pursuing the increased energy density of rechargeable batteries. However, fatal dendrites growth and huge volume change seriously hinder the practical application of lithium metal batteries (LMBs). In this work, a lithium host that preinstalled CoSe nanoparticles on vertical carbon vascular tissues (VCVT/CoSe) is designed and fabricated to resolve these issues, which provides sufficient Li plating space with a robust framework, enabling dendrite-free Li deposition. Their inherent N sites coupled with the in situ formed lithiophilic Co sites loaded at the interface of VCVT not only anchor the initial Li nucleation seeds but also accelerate the Li+ transport kinetics. Meanwhile, the Li2Se originated from the CoSe conversion contributes to constructing a stable solid-electrolyte interphase with high ionic conductivity. This optimized Li/VCVT/CoSe composite anode exhibits a prominent long-term cycling stability over 3000h with a high areal capacity of 10 mAh cm-2. When paired with a commercial nickel-rich LiNi0.83Co0.12Mn0.05O2 cathode, the full-cell presents substantially enhanced cycling performance with 81.7% capacity retention after 300 cycles at 0.2 C. Thus, this work reveals the critical role of guiding Li deposition behavior to maintain homogeneous Li morphology and pave the way to stable LMBs.

Synergistic Effect of Lithium (difluoromethanesulfonyl)(trifluoromethanesulfonyl)Imide (LiDFTFSI) and Vinylene Carbonate (VC) on High Performance of NMC811║Graphite Cells

Lithium-ion batteries (LIBs) have gained increasing importance in energy storage systems, driven by the growing demands of grid storage, automotive, and portable consumer applications. To meet the need for high energy density batteries, one promising approach involves the utilization of high capacity layered transition metal oxide cathodes, such as nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811), which can deliver a high reversible specific capacity of over 180 mAh·g-1 [1,2]. However, due to the structural and interfacial instability[3], nickel-rich NMC cathode still faces challenges in long-term galvanostatic cycling. For these reasons, design of novel electrolyte formulations, which enable formation of an effective cathode electrolyte interphase (CEI), is highly desirable. Recent studies have highlighted the cross-talk between the cathode and anode, indicating that the evolution of the solid electrolyte interphase (SEI) can impact the formation of the CEI[4]. Thus, establishing an effective SEI/CEI pair is essential for achieving long-term cycling of nickel-rich NMC cathode-based cells. Electrolyte optimization plays a crucial role in facilitating the formation of a desirable SEI/CEI pair, leading to an improved cell performance and longevity. Lithium (difluoromethanesulfonyl)(trifluoro-methanesulfonyl)imide (LiDFTFSI) has proven to be promising in solid-polymer-electrolyte batteries due to the good SEI/CEI formation ability and suppressed Al-dissolution[5]. Additionally, LiDFTFSI exhibits also good compatibility with Li-metal batteries[6], heralding promising applications in Li-ion batteries. However, there is lack of systematic research investigating the potential impact of LiDFTFSI on the cathode as well as on resulting CEI formation and dynamics.In this work, we demonstrated enhanced galvanostatic cycling performance of NMC811||graphite cells achieved by utilizing LiDFTFSI and lithium hexafluorophosphate (LiPF6) in a blended salt organic carbonate-based electrolyte formulation. Comprehensive electrochemical and post mortem analysis revealed that the LiDFTFSI alone can effectively mitigate the structural changes in the NMC811 electrode by facilitating the formation of modified CEI. However, the continued growth of an inhomogeneous CEI, caused by the cross-talk effect between electrodes, adversely affected long-term cycling stability. To address this, vinylene carbonate (VC) was introduced to the electrolyte. Synergistic effect with LiDFTFSI leads to the formation of effective and uniform SEI and CEI. As a result, 720 charge/discharge cycles were achieved in NMC811||graphite cells with LiDFTFSI and VC containing electrolytes at 1C while maintaining 80% state-of-health (SOH80%).

Elevating cycle stability of Ni-rich NCM811 cathode via single-crystallization integrating dual-modification strategy for lithium-ion batteries

Nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811), as an attractive next-generation cathode material for lithium-ion batteries, still encounters grievously poor cycling stability triggered by irreversible phase transition in the layered structure and side reactions at the particle surface. Herein, a straightforward sol-gel method was proposed to fabricate highly stable Na+-doped and carbon-coated NCM811 single crystal, where the sodium glutamate acts as the common source of carbon-coating and Na+-doping. The Na ions prefer to occupy Li-sites that can lower the Li+ diffusion energy barrier and raise the threshold energy of Ni2+/Li+ irreversible migration to facilitate boosting Li+ migration rate and structural reversibility, as confirmed by theoretical calculation in conjunction with experimentation. And the carbon coating constructs a protective layer to effectively suppress parasitic reactions at the particle surface for enhancing cycling stability upon cycles. Consequently, the modified NCM-1 cathode displays the initial discharge capacity of 213.8 mAh·g−1 at 0.1 C and distinguished cycling stability at 5 C after 500 cycles with only approximately 0.034% capacity fading per cycle, which will be a strong competitive cathode material for developing high-power and long-lifespan lithium-ion batteries.

Li4Ti5O12-TiO2 composite coating layer enabling LiNi0.8Co0.1Mn0.1O2 electrodes with superior cycling performance

Nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) materials are considered to be one of the cathode candidate materials for high energy density lithium-ion batteries (LIBs), but its electrochemical instability caused by electrodes to electrolyte interface degradation needs to be overcome. Surface coatings can effectively solve this problem. However, traditional coating techniques cover particles rather than electrodes to protect a broader area. Herein, for a more precise coating, a nanoscale Li4Ti5O12-TiO2 composite coating layer (LTOTO) is directly sputtered onto the NCM811 electrodes surface. The LTOTO has superior electronic conductivity compare to Li4Ti5O12. Lithium ions and electrons can diffuse and distribute more uniformly owing to the LTOTO coating on NCM811 electrode. For NCM811 electrodes, the LTOTO coating layer serves as the cathode-electrolyte interface (CEI) within the cycling potential range. Because of its robust structure and strong chemical inertness, LTOTO may successfully shield NCM811 electrodes from electrolyte reactions. The rate performance of NCM811 electrodes is significantly enhanced after Li4Ti5O12-TiO2 coating at 5C (149.74 mAh/g). The capacity retention of NCM811/LTOTO-3 electrode at 1C is 93.2 % at the 100th cycle, which is 13.3 % higher than that of the pristine NCM811 electrodes.

Relieving Stress Concentration through Anion-Cation Codoping toward Highly Stable Nickel-Rich Cathode.

Nickel-rich LiNi0.8Co0.15Al0.015O2 (NCA) with excellent energy density is considered one of the most promising cathodes for lithium-ion batteries. Nevertheless, the stress concentration caused by Li+/Ni2+ mixing and oxygen vacancies leads to the structural collapse and obvious capacity degradation of NCA. Herein, a facile codoping of anion (F-)-cation (Mg2+) strategy is proposed to address these problems. Benefiting from the synergistic effect of F- and Mg2+, the codoped material exhibits alleviated Li+/Ni2+ mixing and demonstrates enhanced electrochemical performance at high voltage (≥4.5 V), outperformed the pristine and F-/Mg2+ single-doped counterparts. Combined experimental and theoretical studies reveal that Mg2+ and F- codoping decreases the Li+ diffusion energy barrier and enhances the Li+ transport kinetics. In particular, the codoping synergistically suppresses the Li+/Ni2+ mixing and lattice oxygen escape, and alleviates the stress-strain accumulation, thereby inhibiting crack propagation and improving the electrochemical performance of the NCA. As a consequence, the designed Li0.99Mg0.01Ni0.8Co0.15Al0.05O0.98F0.02 (Mg1+F2) demonstrates a much higher capacity retention of 82.65% than NCA (55.69%) even after 200 cycles at 2.8-4.5 V under 1 C. Furthermore, the capacity retention rate of the Mg1+F2||graphite pouch cell after 500 cycles is 89.6% compared to that of the NCA (only 79.4%).

Tackling issues of lithium metal anodes with a novel polymeric lithicone coating

Lithium metal (Li) has been hindered from as anodes in commercial batteries for over 50 years, due to two main issues: continuous formation of solid electrolyte interphase (SEI) and lithium dendritic growth. In this work, we report a new strategy to tackle these issues, i.e., using molecular layer deposition (MLD) to grow an ionically conducting but electrically insulating polymeric lithicone coating, an Li-containing triethanolamine (LiTEA). Our electrochemical tests revealed that this LiTEA coating could serve as an exceptional protection layer over Li anodes. Consequently, the LiTEA-coated Li electrodes could achieve a superior cyclability of > 10000 Li stripping/plating cycles at a current density of 5 mA cm−2 and a long cyclability of > 5500 cycles at 2 mA cm−2 in Li||Li symmetric cells without failures, under a fixed areal capacity of 1 mAh cm−2. Characterizations using scanning electron microscopy and X-ray photoelectron microscopy verified that Li+ ions could be easily extracted through and deposited under the LiTEA coating during the stripping/plating processes. Consequently, this LiTEA coating significantly inhibited the formation of SEI and Li dendrites. This underlies the long cycling lifetime of the LiTEA-coated Li||Li cells. Coupling with the nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes, more encouragingly, the LiTEA-coated Li anodes could remarkably extend the cyclability and sustainable capacity of the resultant Li||NMC full cells. We also demonstrated that the performance of Li||NMC cells could be further improved through combining an LiTEA-coated Li anode with an Li2S-modified NMC811 via atomic layer deposition (ALD). Thus, this study is inspiring for developing high-energy Li||NMC lithium metal batteries.

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.

Application of Artificial Interphase on Ni-Rich Cathode Materials Via Hybrid Ceramic-Polymer Electrolyte in All Solid State Batteries

Among many cathode materials, nickel-rich LiNi0.83Co0.12Mn0.05O2 (NCM 831205) has been spotlighted as one of the most feasible candidates for next-generation LIBs because of its high discharge capacity (~200 mAh/g). However, NCM 831205 shows significant performance degradation, which is mostly attributed to cation mixing, surface side reactions, and intrinsic structural instability originating from the large volume changes during repeated cycling.Conventional lithium ion batteries (LIB) normally use flammable nonaqueous liquid electrolytes, resulting in a serious safety issue in use. In this respect, all-solid-state batteries (ASSB) are regarded as a fundamental solution to address the safety issue by using a solid state electrolyte in place of the conventional liquid one.This work employed lithium sulfonate (SO3Li) tethered polymer, obtained from sulfonation of commercial polymer, to serve as the artificial protective coating on the active NCM831205 of the cathode for ASSB based on hybrid PEO-ceramic solid electrolyte.The coating layer should prevent direct contact of electrolyte with the cathode, thus avoid the negative effects such as microcracks of NCM831205 and undesired CEI formation. The preparation of hybrid ceramic-polymer electrolyte through a solvent-free process. The hybrid electrolytes exhibit good flexibility and processability with respect to pure ceramic and pure PEO polymer electrolyte.It is demonstrated that the hybrid electrolytes can penetrate into cathode under 60°C, providing a good Li+ transfer channel inside the battery. Moreover, the sulfone based polymer protective coating could effectively improve the electrochemical stability of the NCM831205 without sacrificing the battery performance. Keywords: NCM831205, Artificial Polymer Coating, All-Solid-State Batteries

Boron and magnesium ions co-doping synergistically enhances the electrochemical performance of nickel-rich cathode materials

Nickel-rich ternary materials still suffer from defects of poor structure stability, fast capacity decay and poor rate performance, which inhibits their practical application in power batteries. Herein, a novel nickel-rich LiNi0.74Co0.14Mn0.12O2 cathode material co-doped with metallic and non-metallic ions was designed and prepared. The doped Mg2+ ions enter the lithium layers, reducing the Li+/Ni2+ cation mixing of the material; act as pillars, stabilizing the layered framework. While the doped B3+ ions occupy the tetrahedral sites, which expand the interlayer spacing and accelerate the diffusion of lithium ions. Furthermore, B3+ ions change the microstructure of the primary particles, alleviate the structural strain during the long cycle process and maintains the stability of the layered structure. Owing to the synergistic effect of Mg2+ and B3+ doping, the co-doped material exhibits superior electrochemical performance. A discharge capacity of 127.6 mAh·g−1 at 10 C, as well as a capacity retention of 91.33% after 100 cycles at 1C rate was achieved in the co-doped material. This metallic and non-metallic ion co-doping ternary material demonstrates its superiority compared with the single-element modified material.

Stabilization of NCM811 cathode for Li-ion batteries by N-doped carbon coating

Ternary nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM811), as a promising next-generation cathode material for lithium-ion batteries, is still suffered from severe capacity fading triggered by irreversible phase transition and side reactions during cycling, which can be effectively circumvented by surface coating. Herein, microspheric NCM811 particles are homogeneously coated by N-doped carbon layer via a facile and low-cost rheological phase reaction method followed by low temperature sintering. The N-doped carbon coating disperses more uniformly than carbon coating on NCM811, which is attributed to the formation of NiN bond between carbon coating layer and bulk NCM811. And the introduced N element can inhibit the reduction of Ni3+ to Ni2+ on the surface of NCM811, leading to a positive effect on the suppression of cationic mixing that further improves the structural stability. Based on the electrochemical performance analyses, it is found that the surface pseudocapacitance and Li+ diffusion ability both are significantly promoted after N-doped carbon coating. Benefit from the suitable pseudocapacitive behavior and high Li+ diffusion coefficient, the NCM811-CN0.5 electrode presents a discharge specific capacity of 216.98 mAh/g at 0.1C, 151.01 mAh/g at 10C, and capacity retention of 82.3 % after 500 cycles at 5C, indicating that it will be an ideal cathode material for developing high-power and long-lifespan lithium-ion batteries.

High structural stability of graphene coated nickel – rich cathode material in Li – ion battery

The high energy density cathode material, nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (LNCM), has been extensively researched for its potential applications. Nevertheless, its structural instability, weak conductivity and unsafe properties greatly impede its further development. To address these issues, the method of surface coating by graphene and element doping by Mg atom for LNCM is proposed, and its structural and electrochemical properties, as well as the promoting mechanism are comprehensively studied. Such as, the structural and morphological features are investigated by X– ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy dispersive X – ray spectroscopy (EDX) and transmission electron microscopy (TEM). Characterization techniques depict the composites’ dimension, modified construction and components. Electrochemical performances are studied using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge – discharge test. The typical redox peaks of Ni2+/Ni4+ and Co3+/Co4+ are well-defined for LNCM@rGM, and its improved electrochemical performance compared to LNCM are demonstrated. Specifically, LNCM@rGM exhibits a higher capacity retention of 58%, maintaining a capacity of 123.3 mAh g−1 after the 200th cycle, from an initial value of 211.0 mAh g−1. Additionally, LNCM@rGM shows a higher rate capability of 80.2 mAh g−1 at 5 C, as well as improved Li+ diffusion and higher exchange current density. The findings indicate that the composite structure consisting of graphene coating and element doping shows improved electrochemical performance when exposed to an optimal heating temperature, resulting in enhanced structural stability, elevated ionic/electronic conductivity, and synergistic effects on the materials.