Discharge Capacity Retention Rate Research Articles

Homogeneously Planar-Exposure LiB Fiber Skeleton Toward Long-Lifespan Practical Li Metal Pouch Cells.

LiB alloy is promising lithium (Li) metal anode material because the continuous internal LiB fiber skeleton can effectively suppress Li dendrites and structural pulverization. However, the unvalued surface states limit the practical application of LiB alloy anodes. Herein, the study examined the influence of the different exposure manners of the internal LiB fiber skeleton owing to the various surface states of the LiB alloy anode on electrochemical performance and targetedly proposed a scalable friction coating strategy to construct a lithiated fumed silica (LFS) functional layer with abundant electrochemically active sites on the surface of the LiB alloy anode. The LFS significantly suppresses the inhomogeneous interfacial electrochemical behavior of the LiB alloy anode and enables the exposure of the internal LiB fiber skeleton in a homogeneously planar manner (LFS-LiB). Thus, a 0.5Ah LFS-LiB||LiCoO2 (LCO) pouch cell exhibits a discharge capacity retention rate of 80% after 388 cycles. Moreover, a 6.15Ah LFS-LiB||S pouch cell with 409.3Whkg-1 exhibits a discharge capacity retention rate of 80% after 30 cycles. In conclusion, the study findings provide a new research perspective for Li alloy anodes.

Synthesis of Co@CoO/C by micro-tube method and their electrochemical performances

Lithium-ion batteries (LIBs) are promising secondary batteries that are widely used in portable electronic devices, electric vehicles and smart grids. The design and synthesis of high-performance electrode materials play a crucial role in achieving lithium-ion batteries with high energy density, prolonged cycle life, and superior safety. CoO has attracted significant attention as a negative electrode material for lithium-ion batteries due to its high theoretical capacity and abundant resources. However, its limited conductivity and suboptimal cycling performance impede its potential applications. The study proposes a novel micro-tube reaction method for the synthesis of Co@CoO/C, utilizing Kapok fiber as a template with a special hollow structure. The microstructure and composition of the samples were characterized using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After conducting electrochemical performance tests, it was discovered that at a current density of 100 mA/g and within the range of 0.01–3.0 V for 50 charge and discharge cycles. Co@CoO/C composite negative electrode exhibits a reversible lithium insertion specific capacity of 499.8 mAh/g and keep a discharge capacity retention rate of 97.6 %. The greatly improved lithium storage and stability performance of Co@CoO/C composite anode is mainly attributed to the synergistic effect between Co@CoO nanoparticles and the kapok carbon microtubule structure.

Mixed crystal FeFx submicron spheres loaded on fluorinated graphene as cathode materials for Lithium-Ion batteries

Iron fluoride (FeF3 and FeF2) is a potential candidate for the next generation of lithium-ion battery (LIBs) cathode materials due to their high theoretical specific capacity and low cost. However, previous studies have reported that the poor conductivity of FeF3 and FeF2 prevents their theoretical specific capacity from being effectively realized. Herein, fluorinated graphene loaded FeFx (FeFx@FG) submicron sphere was synthesized using graphene oxide and utilized as cathode materials for LIBs. Characterization by X-ray diffraction and transmission electron microscopy confirmed that the synthesized FeFx (x = 2 and 3) contains mixed FeF3 and FeF2crystals. The mixed crystal structure enables the FeFx@FG submicron sphere composite to display two steps in the electrochemical reaction when FeF3 and FeF2 discharge cooperatively, leading to excellent discharge performance. In addition, since the FG prepared by acid thermal method has good conductivity, it can significantly improve the FeFx conductivity and specific capacity when being connected to FG via C-F bond. The electrochemical tests show that the initial discharge capacity of FeFx@FG is as high as 394.24 mAh/g at the rate of 0.2C in the range of 1.5–4.0 V at 25 °C and display an excellent discharge capacity retention rate after the first discharge process, showing great potential of the mixed crystalline iron fluoride cathode in the field of lithium-ion batteries.

RETRACTED: The three-dimensional porous mesh structure of Cu-based metal-organic-framework - Aramid cellulose separator enhances the electrochemical performance of lithium metal anode batteries

Lithium metal, due to its advantages of high theoretical capacity, low density and low electrochemical reaction potential, is used as a negative electrode material for batteries and brings great potential for the next generation of energy storage systems. However, the production of lithium metal dendrites makes the battery life low and poor safety, so lithium dendrites have been the biggest problem of lithium metal batteries. This study shows that the larger specific surface area and more pore structure of Cu-based metal-organic-framework - aramid cellulose (CuMOF-ANFs) composite separator can help to inhibit the formation of lithium dendrites. After 110 cycles at 1 mA/cm2, the discharge capacity retention rate of the Li-Cu battery using the CuMOF-ANFs separator is about 96 %. Li-Li batteries can continue to maintain low hysteresis for 2000 h at the same current density. The results show that CuMOF-ANFs composite membrane can inhibit the generation of lithium dendrites and improve the cycle stability and cycle life of the battery. The three-dimensional (3D) porous mesh structure of CuMOF-ANFs separator provides a new perspective for the practical application of lithium metal battery.

The functional electrolyte containing 2-fluorobenzenesulfonyl fluoride (2FF) additive enhances the performance of LiNi0.8Co0.1Mn0.1O2/graphite batteries by stabilizing the cathode interface

A functional electrolyte containing conventional carbonate esters solvents, LiPF6 salt, and novel 2-fluorobenzenesulfonyl fluoride (2FF) additive is developed to stabilize the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode interface and enhance the performance of NCM811/graphite lithium-ion batteries (LIBs). It is indicated that due to the unique C-F and sulfonyl fluoride groups of 2FF, the NCM811/Li half batteries containing 2% 2FF electrolyte show the highest cycling performance, a coulombic efficiency of 98.4% and a capacity retention of 89.4% are obtained after 100 cycles at 0.5C. And compared to the pouch NCM811/graphite full batteries with blank electrolyte, the long cycle performance of the batteries with 2% 2FF is also increased after 500 cycles at 45 °C, the discharge capacity retention rate retains at 80.04% and the coulombic efficiency closes to 100%. The spectroscopic characterization and theoretical calculation demonstrate that the electrolyte with 2FF additive preferentially react and generate uniform CEI film. These results show that this 2FF-containing electrolyte can stabilize NCM811 cathode interface, revealing a promising prospect of the commercial application of high-nickel LIBs.

Effect of ammonium fluoride concentration on synthesis of Co3O4/CC as cathode material for zinc cobalt battery applications

Aqueous zinc ion batteries (AZIBs) have received great attention due to their simple manufacturing technology, high energy density, intrinsic safety and economic feasibility. Co3O4 is one of the ideal cathode materials for aqueous zinc-ion batteries, but many studies were concentrated on the synthesis, design and doping of cathodes. The effect of process parameters on morphology and performance were rare reported. In this paper, Co3O4/CC cathode material based on carbon cloth was prepared by different reactant concentration. The reactant concentration ratio were 2:1, 4:1, 6:1 and 8:1, respectively. The battery was possessed better performance that was assembled by Co3O4/CC material synthesized reactant concentration of 2:1. Co3O4/CC nanowire was uniform distribution, regular surface and small size on carbon cloth. The Zn-ion battery had excellent rate performance and low reaction resistance. The average discharge specific capacity is 142.6 mAh/g and capacity retention rates of 87.8% after 60 charge discharge cycles. The discharge specific capacity and capacity retention rate are significantly higher than the other three Co3O4/CC materials and the charge transfer resistance of the material is the smallest. The study optimized applicable reactant concentration of fabrication cathode Co3O4 in zinc-ion batteries.

Dual-layer composite solid polymer electrolytes with Janus properties for interface modification of solid state lithium metal batteries

Solid polymer electrolytes are widely applied in lithium metal batteries owing to good flexibility and machinability. However, monolayer polymer electrolyte are difficult to simultaneously satisfy the interfacial contact with the cathode and Li anode. Herein, the dual-layer composite solid polymer electrolyte with polypropylene film (CSPE@PP) are designed to promote the interfacial compatibility between the solid electrolytes and electrodes. The X-ray photoelectron spectroscopy (XPS) results confirm that poly (vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) can react with Li metal to form LiF layer, restraining the Li dendrite growth. Meanwhile, the polyacrylonitrile (PAN) antioxidant layer strengthens the contact stability between the electrolytes and the cathodes. Moreover, the PP film serves as the electrolyte's skeleton and connecting layer, enhancing the ion diffusion and mechanical strength of the solid electrolytes. As a result, the Li||CSPE@PP||Li cell is able to stably cycle over 400 h at 0.1 mA cm−2. The LFP||CSPE@PP||Li solid-state batteries deliver 141.98 mAh g−1 discharge capacity and high retention rate (91.1%) after 100 cycles at 0.1C. This work provides a viable strategy for expanding the application of composite solid polymer electrolyte (CSPE) in lithium metal batteries.

Performance enhancement of lithium-ion battery using modified LiMn2O4 cathode followed by ultrasonic-assisted electrochemically synthesized graphene

Herein, the LiMn2O4 (LMO) cathode was modified using ultrasonic-assisted electrochemically synthesized graphene to enhance lithium-ion batteries' charging and discharging performance. Graphene was synthesized from graphite using an electrochemical exfoliation process in which 0.1 M molar (NH4)2SO4 was utilized as the electrolyte with +10 to +12V DC power, followed by ultrasonication in acetone for 2 h. The FESEM, EDX, XRD, Raman, FTIR, UV–vis, and TGA results suggested that ultrasonically treated graphene (EG1) is superior to electrochemically exfoliated graphene (EG2). Thus, EG1 was used to modify the LMO cathode to fabricate lithium-ion batteries. Afterward, the electrochemical performances of the LMO and LMO/EG1 cathode batteries were investigated. Surface morphological analysis revealed that EG1 is composed of two-dimensional, planar, brighter, and less oxidized graphene nanosheets with an average particle size of 18.02 nm. XRD results exhibited that EG1 has a smaller crystalline size and a thinner average stacking thickness of its layered structure than EG2. According to Raman analysis, the intensity ratio I2D/IG of EG2 and EG1 were 0.70 and 0.81, respectively, deduced that both are multi-layered graphene structures; however, EG1 contains a lesser number of graphene layers than EG2. The electrochemical analysis showed that LMO/EG1 cathode batteries have 89 % coulombic efficiency at 0.1C, while LMO batteries have only 81 %. The discharge capacity retention rate of the LMO batteries was 71.4 %, while it was 94.8 % for LMO/EG1 after observing 100 cycles at 0.1 C. Therefore, LMO/EG1 has excellent cycle stability and electrochemical performance and could potentially enhance the performance in hybrid automotive and electronic devices.

Hydrogen storage and capacity degradation mechanism of superlattice La-Y-Ni-based hydrogen storage alloy

New La-Y-Ni-based hydrogen storage alloys exhibit key technological advantages for energy storage; however, several challenges arise because of their insufficient cycle life. In this study, we design a non-stoichiometric structure and present a scheme for obtaining a stable superlattice structure by optimizing multi-component elements and understanding the structural evolution and anti-degradation mechanism for increasing the cycle life. The rationality of the scheme is verified by designing AB3.67-type La1.4Ce0.5Y4.1-xSmxNi20Mn1.2Al0.8 (x = 0, 0.2, 0.3, and 0.4) alloys. Substituting Y with an appropriate amount of Sm reduces capacity degradationin both in electrochemistry and solid/H2 reactions because it effectively inhibits the transition of the stable phase and this regulation reduces the mismatch of subunits in the Gd2Co7-type phase, especially the control [A2B4] subunit instead of the [AB5] subunit. Further, a capacity degradation mechanism is illustrated and the entire process is divided into three stages. The corrosion resistance of synergistic elements in the first stage (<100 cycles) of the electrochemical reaction is a decisive factor controlling the long-term cyclic stability of alloys. Although the amorphous phase in the solid-H2 reaction is the main factor responsible for decay, the La1.4Ce0.5Y3.8Sm0.3Ni20Mn1.2Al0.8 alloy shows better electrochemical properties, with a maximum discharge capacity, H2-absorption capacity, and capacity retention rate S100 of 377.7 mAh g−1, 1.64 wt%, and 90.9 %, respectively. After 500 cycles, the capacity retention rate is enhanced from 42 % to 60.9 %. The proposed scheme is expected to prom.

Heterojunction‐Accelerating Lithium Salt Dissociation in Polymer Solid Electrolytes

AbstractThe practical application of solid‐state lithium‐metal batteries (SSLMBs) based on polymer solid electrolytes has been hampered by their low ion conductivity and lithium‐dendrite‐induced short circuits. This study innovatively introduces 1D ferroelectric ceramic‐based Bi4Ti3O12‐BiOBr heterojunction nanofibers (BIT‐BOB HNFs) into poly(ethylene oxide) (PEO) matrix, constructing lithium‐ion conduction highways with “dissociators” and “accelerating regions.” BIT‐BOB HNFs, as 1D ceramic fillers, not only can construct long‐range organic/inorganic interfaces as ion transport pathways, but also install “dissociators” and “accelerating regions” for these pathways through the electric dipole layer and built‐in electric field of BIT‐BOB HNFs, promoting the dissociation of lithium salts and the transfer of lithium ions. The working mechanisms of BIT‐BOB HNFs in the polymer matrix are verified by experimental tests and density functional theory calculations. The obtained composite solid electrolytes exhibit excellent lithium‐ion conductivity and migration number (6.67 × 10−4 S cm−1 and 0.54 at 50 °C, respectively). The assembled lithium symmetric battery achieves good cycling stability of over 4500 h. The LiFePO4||Li full battery delivers a high Coulombic efficiency (&gt;99.9%) and discharge capacity retention rate (&gt;87%) after 2200 cycles. In addition, the prepared composite polymer solid electrolyte demonstrates good practical application potential in flexible pouch batteries.

Electrospun Polyacrylonitrile/Polyvinylidene Fluoride/Boehmite Separator and Gel Polymer Electrolyte Polyethylene Oxide/Polyvinylidene Fluoride‐hexafluoropropylene/Lithium Bis(trifluoromethanesulfonyl)imide/Boehmite Composite Separator Are Used for Fast Charging

AbstractWith the increasing popularity of electric vehicles, the fast charging of lithium (Li) batteries is attracting increasing attention. However, the rapid decline in battery capacity caused by fast charging and accidents caused by Li dendrites piercing the separator greatly restrict fast‐charging applications. Herein, an electrospun polyacrylonitrile/polyvinylidene fluoride/boehmite (PAN/PVDF/12 wt.% AlO(OH)) and gel polymer polyethylene oxide/polyvinylidene fluoride‐hexafluoropropylene/lithium bis(trifluoromethanesulfonyl)imide/boehmite (PEO/PVDF‐HFP/12.6 wt.% LiTFSI /10 wt.% AlO(OH)) pressed together to form a two‐layer functional separator is designed. The electrospun separator improves the high‐temperature resistance of the entire separator due to its special structure. After the 1 h heat treatment at 220 °C, the thermal shrinkage rate of the double‐layer separator reaches 10.1%, showing good thermal stability. At 0.2 C, the discharge capacity retention rate is 99.4% after 100 cycles. After 1000 cycles at a rate of 10 C, the discharge capacity remains at 88% of the initial value. The two‐layer separator exhibits better capacity retention and superior rate performance than PP, providing an effective approach for commercializing fast‐charging functional separators.

TiO2‐Induced Conversion Reaction Eliminating Li2CO3 and Pores/Voids Inside Garnet Electrolyte for Lithium–Metal Batteries

AbstractGarnet Li7La3Zr2O12 (LLZO) is regarded as a promising solid electrolyte due to its high Li+ conductivity and excellent chemical stability, but suffers from grain boundary resistance and porous structure which restrict its practical applications in lithium–metal batteries. Herein, a novel and highly efficient TiO2‐induced conversion strategy is proposed to generate Li ion‐conductive Li0.5La0.5TiO3, which can simultaneously eliminate the pre‐existing pores/voids and contamination Li2CO3. The Li/LLZTO‐5TiO2/Li symmetric cell exhibits a high critical current density of 1.1 mA cm−2 at 25°C, and the long‐term lithium cycling stability of over 1500 h at 0.1 mA cm−2. More importantly, the excellent performance of LLZTO‐5TiO2 electrolyte is verified by LiCoO2/LiFePO4 coupled full cells. For example, The LiCoO2 coupled full cell exhibits a significant discharge rate capacity of 108 mAh g−1 at 0.1 C, and a discharge capacity retention rate of 91.23% even after 150 cycles of charge and discharge. COMSOL Multiphysics and density functional theory calculation reveal that LLZTO‐5TiO2 electrolyte has a strong lithium affinity and uniform Li ions distribution, which can improve the cycle stability of Li–metal batteries by preventing dendrite growth.

Synthesis and Performance of NaTi2(PO4)3/VGCF@C Anode Composite Material for Aqueous Sodium-Ion Batteries

This study combines self-prepared NaTi2(PO4)3 (NTP) with commercial vapor-grown carbon fiber (VGCF) using a solid state calcination, then coats it with carbon to synthesize the composite anode material NaTi2(PO4)3/VGCF@C (NTP/VGCF@C). The microstructure and electrochemical properties of the composite material were then analyzed using microstructure analysis and electrochemical testing equipment. Single phase NTP shows nanoparticles with a polyhedral structure, and there is good contact at the interface between the nanoparticles and the VGCFs. The carbon coating formed on the NTP particles displays a nearly 6.5 nm thick layer of amorphous carbon. From the coin-cell battery performance measurements, after 850 cycles, the composite material NTP/VGCF@C exhibits an excellent retention rate of 96.3% compared to that of the pure NTP material when the current density is 200 mA/g. As a result, the composite material and lithium manganate (denoted as LMO) were assembled into an LMO-NTP/VGCF@C aqueous sodium-ion soft pack full battery system. The full battery shows an initial capacity of 31.07 mAh at a rate of 0.5C, and a reversible discharge capacity retention rate of 95.8% after 480 cycles, exhibiting a good long-cycle stability performance.

Effect of Li–Si composites on electrochemical properties of silicon-based anode materials

Metal silicides are considered promising candidates for the replacement of graphite due to their larger capacity than graphite used in Li-ion batteries. In this work, a type of lithium silicide composite material consisting of LixSi, graphite (G), and porous carbon (PC) together with carbon coating treatment, denoted as (LS-G-PC)@C, was prepared by high-energy ball milling and subsequent pitch pyrolysis. This type of material is used as a pre-lithiation additive to improve the initial Coulombic efficiency (ICE) of Si-based anodes. The microstructural characteristic of (LS-G-PC)@C composite material was analyzed by x-ray diffraction and scanning electron microscopy. The electrochemical properties were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and capacity cycling tests. It has been found that the irregular particles of LS compounds are uniformly dispersed on the graphite sheet, which constitutes an effective conductive network together with PC. The addition of a 5 wt. % (LS-G-PC)@C pre-lithiation additive makes the ICE of a low ICE silicon-based composite material increase by 16%. At a current density of 100 mA g−1, the discharge capacity retention rate of the silicon-based composite increased from 86.1% to 91% after the 19th cycle, showing good cycle stability. Further work is to add higher levels of our pre-lithiation additive in order to improve the ICE significantly.

Fabricating Heterostructures for Boosting the Structure Stability of Li-Rich Cathodes.

Li-rich Mn-based oxides are regarded as the most promising new-generation cathode materials, but their practical application is greatly hindered by structure collapse and capacity degradation. Herein, a rock salt phase is epitaxially constructed on the surface of Li-rich Mn-based cathodes through Mo doping to improve their structural stability. The heterogeneous structure composed of a rock salt phase and layered phase is induced by Mo6+ enriched on the particle surface, and the strong Mo-O bonding can enhance the TM-O covalence. Therefore, it can stabilize lattice oxygen and inhibit the side reaction of the interface and structural phase transition. The discharge capacity of 2% Mo-doped samples (Mo 2%) displays 279.67 mA h g-1 at 0.1 C (vs 254.39 mA h g-1 (pristine)), and the discharge capacity retention rate of Mo 2% is 79.4% after 300 cycles at 5 C (vs 47.6% (pristine)).

Reducing Ni/Li disorder and boosting electrochemical performance of LiNi0.8Co0.067Fe0.033Mn0.1O2 cathode material

BackgroundLiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered for commercial application of next-generation lithium batteries due to their high-energy-density. However, Ni/Li disorder affects electrochemical performance, and this restricted further promotion and commercial application of this material. Expensive and toxic Co can boost the reversible properties of electrode materials and decrease Ni/Li disorder. Fe3+ and Co3+ have the same electronic configuration and are considered to replace part of the Co to play the same role. MethodsLiNi0.8Co0.067Fe0.033Mn0.1O2 (Fe1-NCM811) electrode material replacing partly Co with Fe is produced via urea hydrothermal and high temperature sintered process. And NCM811 electrode material is produced by same method. The XRD of NCM811 and Fe1-NCM811 electrode materials were refined by using Maud software. Significant findingsFe1-NCM811 cathode with Fe replacing part Co obviously reduces Ni/Li disorder degree from 3.58% to 1.16%. The first discharge capacity of Fe1-NCM811 electrode (211.4 mAh g-1) is more than NCM811 electrode (200.8 mAh g-1) at 0.1C, and its rate capacity (142.3 mAh g-1) is more than NCM811 electrode(129.4 mAh g-1) at 5C. The discharge capacity retention rate of Fe1-NCM811 cathode (77.5%) after 500 cycles is nearly three times that of NCM811 cathode (26.1%).

Effects of Al2O3 and LiAlO2 Co-coating on electrochemical properties of LiNi0.8Co0.1Mn0.1O2 cathode materials

Lithium-ion batteries are widely used in aerospace, power vehicles, portable electronic devices and other fields because of their environmental friendliness, rechargeable cycle and high energy density. The nickel-cobalt-manganese ternary materials with high nickel has high specific discharge capacity and is regarded as one of the most promising cathode materials. However, with the increase of the number of cycles, the cycle performance becomes worse and the specific capacity decays sharply. In this work, Al2O3 and LiAlO2 were coated on the surface of NCM811 by combining ball milling mixing and solid-phase synthesis to prepare the AL-NCM811 cathode material. The coating thickness formed by Al2O3 and LiAlO2 was 10–70 nm, which effectively improves the cycle stability and rate performance of NCM811 material. When charged and discharged at 0.1C, the first discharge specific capacity and capacity retention rate after 100 cycles of 0.5AL-NCM811 were 196.26 mAh/g and 96.47%, respectively, while those of NCM811 were only 193.78 mAh/g and 72.18%, respectively. When the current density was 5.0C, the discharge specific capacity of 0.5AL-NCM811(139.16 mAh/g) was 55.368 mAh/g higher than that of NCM811(83.80 mAh/g).

High‐performance nano‐TiO2@polyvinylidene fluoride composite separators prepared by electrospinning for safe lithium‐ion battery

AbstractTraditional polyolefin separators cannot guarantee safety for lithium‐ion batteries at high temperature due to their low melting point, especially for high power discharge. Therefore, it is imperative to develop separators with excellent thermal stability. In this paper, we have prepared TiO2 modified PVDF composite separators by electrospinning. When compared with commercial PE separators, this kind of composite separators show superior thermal stability at 160°C. In addition, it is found that the 0.5‐TiO2@PVDF separator exhibits excellent flame retardant and optimal tension strength. Meanwhile, the 0.5‐TiO2@PVDF separator exhibits ideal liquid electrolyte storage capacity, which improves the ionic conductivity (0.68 mS cm−1). As a result, the LiCoO2||Li cells with 0.5‐TiO2@PVDF separator have high discharge capacity retention rate at a current density of 1 C (300 cycles) and excellent rate performance (1.75 mAh at 5 C). In short, nano‐TiO2 modified PVDF separator has a great application prospect in high‐performance and high‐safety lithium‐ion batteries.

Reduced graphene oxide-modified aluminum foils as highly conductive and corrosion-resistant cathode current collectors for Li-ion batteries

Aluminum (Al) foil current collector is easily corroded by the electrolyte during long-term cycling and damages the electrochemical performance of the lithium-ion batteries (LIBs), especially at high operating voltages, this limits the development of next-generation high operating voltage (5 V) LIBs. Here, we successfully fabricated reduced graphene oxide (RGO) modified Al foils with high electrical conductivity and corrosion resistance as current collectors, which significantly enhanced the corrosion resistance of current collectors in LiPF6-based electrolytes and improved the long-term cycling stability and safety of LiMn2O4 batteries at high voltages. The LiMn2O4(LMO) cells with RGO modified Al foils as the current collector (LMO/GA) exhibit a discharge capacity retention rate of 88.7 % after 200 cycles at a current density of 100 mA g−1, which is much higher than that of the cells with pristine Al foils as the current collector (LMO/PA). The reversible capacity, rate capability, and thermal stability of the LMO/GA cells have also been significantly improved with RGO mediations. This work provides a new idea for the development of long-life corrosion-resistant current collector materials for high-performance LIBs at high operating voltages.

Controlled preparation of nano-Al2O3/PPy composite coatings to compensate surface structural defects of lithium-rich layered oxides

Li-rich cathode materials (LRCMs) have high energy density and discharge capacity, but still suffer from low initial Coulombic efficiency, unstable structure, and poor cycle stability. In this paper, an inorganic/organic composite coating strategy is proposed to effectively modulate the interfacial structure and enhance the electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2. The nano-Al2O3 and polypyrrole (PPy) double-layer coating forms a firm protective shell on the surface of the cathode material to alleviate external side reactions. The results show that the double-layer coating sample (PPy-Al-LNCM) achieved a discharge capacity retention rate of 90.74 % after 100 cycles at 1 C rate. In addition, the SEM images after cycling also confirmed that the PPy-Al-LNCM cathode still maintains an intact morphology, which indicates that this modification method is beneficial for the further development of Li-rich cathode materials.