Generation Lithium-ion Batteries Research Articles

Advanced electrolyte design for stable lithium metal anode: From liquid to solid

Abstract Li metal anode is among the most promising anode materials for next generation of lithium batteries (Li–O2, Li–S batteries). However, the commercial applications of Li metal batteries have been seriously hindered due to safety and lifetime concerns caused by the formation of Li dendrites. In this review, we focus on the electrolyte designs in handling Li dendritic growth and improving electrochemical performance of Li metal anode, and outline the trend of electrolyte designs from traditional composition adjustment of the liquid electrolyte to molecular design of the solid polymer electrolyte. We aim to provide strategic guidance for the rational design and fabrication of safety electrolytes, and to explore the possibility of these designs in practical application. We critically evaluate the existing challenges and future opportunities associated with this burgeoning field.

Rosa roxburghii-like hierarchical hollow sandwich-structure C@Fe2O3@C microspheres as second nanomaterialsfor superior lithium storage

Fe2O3, as a promising advanced anode for the next generation lithium ion batteries, behaves high theoretical capacity and rich electrochemical properties. However, the poor cycle performances and low conductivity impede its extensive applications in lithium ion batteries. Herein, the von Mises stress distribution on solid spheres and hollow spheres were simulated by finite element method which confirmed the vital role of porous hollow spheres on strain-relaxation behavior as electrode materials. We also have developed a template method for the first preparation of rosa roxburghii-like hierarchical hollow sandwiched C@Fe2O3@C microspheres as second nanomaterials for superior lithium storage. As an advanced anode for lithium ion batteries, the porous C@Fe2O3@C microspheres exhibit reversible gravimetric capacity (1167 mAh g−1 after 100 cycles at 0.2 C), high rate performance (762 mAh g−1 after 1000 cycles at 1 C) and cycling stability without obvious capacity fading. The excellent performance is ascribed to the hierarchical hollow structure which can better withstand the stress produced in the process of ion embedding/stripping and alleviate the volume change of materials. On the other hand, the double carbon layer can effectively inhibit the self-aggregation effect of nano-scale Fe2O3 and provide a three-dimensional electronic network.

A Reduced-Order Electrochemical Model for All-Solid-State Batteries

All-solid-state batteries (ASSBs) have been considered as the next generation of lithium-ion batteries. Physics-based models have the advantage of providing internal electrochemical information. To promote physics-based models in real-time applications, in this study, a series of model reduction methods are applied to obtain a reduced-order model (ROM) for ASSBs. First, analytical solutions of the partial differential equations (PDEs) are derived by the Laplace transform. Then, the Padé approximation method is used to convert the transcendental transfer functions into lower order fractional transfer functions. Next, the concentration distributions in electrodes and electrolytes are approximated by parabolic and cubic functions, respectively. Due to the fast calculation of concentration distributions in real time, the equilibrium potential, overpotentials, and battery voltage can now be directly calculated. Compared with the original PDE-based model, the voltage errors of the proposed ROM are less than 2.6 mV. Compared with the voltage response of experimental data, a good agreement can be observed for the ROM under three large C-rates discharging conditions. The calculation time of ROM per step is within 0.2 ms, which means that it can be integrated into a battery management system. The proposed ROM achieves excellent performance and a better tradeoff between model fidelity and computational complexity.

Preparation of Poly-1-butene Nanofiber Mat and Its Application as Shutdown Layer of Next Generation Lithium Ion Battery.

Nonwoven nanofiber webs from polyolefin show great potential in various fields such as nanofilters, high performance membranes and separators in lithium ion batteries (LiB). Although nonwoven microfiber webs can be obtained by the well-established melt-blown method, it is relatively difficult to produce nonwoven nanofiber web using polyolefin (polyethylene and polypropylene). There have been several reports on the preparation of polyolefin nanofibers by melt-electrospinning, although this approach presents several intrinsic disadvantages, i.e., high processing costs, the requirement of complex equipment, and poor control over pore size or fiber diameter. Solution-based electrospinning has the potential to overcome the drawbacks of melt-electrospinning, but the solubility of most polyolefin is poor. In this study, we found that poly-1-butene, a member of the poly(alpha-olefin) family, can be used in the electrospinning process. We set the concentration of the polymeric solution for electrospinning at 0.65–1.7 g/mL. Here, we report on the fabrication of nonwoven fiber webs composed of poly-1-butene and their copolymers. The diameter of the nonwoven fiber mat was 0.2–0.4 μm, which can be applicable for shutdown layer. As a representative application, we prepared a poly-1-butene nanofiber separator with an appropriate pore size by electrospinning for use as the shut-down layer of a next-generation LiB. The PB-based nanofiber mat provided shutdown ability at around 100 to 120 °C.

Promoting electrochemical performances of LiNi0.5Mn1.5O4 cathode via YF3 surface coating

High voltage LiNi0.5Mn1.5O4 cathodes are of prime importance for the development of next generation lithium-ion batteries (LIBs) with high energy density. LiNi0.5Mn1.5O4, however, always was attacked by the generated HF from the electrolyte decomposition during cycling, leading to instable surface structure and poor Li+ diffusion kinetic property. In this regard, YF3 with good thermal stability and excellent structural stability in the HF containing electrolyte, is chosen as coating layer to modify the surface of LiNi0.5Mn1.5O4. Ex-situ electrochemical impedance spectroscopy study and inductively coupled plasma analysis indicate that YF3 coating layer on the surface of LiNi0.5Mn1.5O4 could act as protect medium to effectively suppress side reactions between the LiNi0.5Mn1.5O4 surface and electrolyte, and thus enhance its structural stability and kinetics properties during repeated electrochemical reactions. As a result, LiNi0.5Mn1.5O4 after YF3 modification shows the improved capacity retention of 84% after 100 cycles at 0.1C, and 78 mAh g−1 could be obtained at 2C, much higher than those of the pristine LiNi0.5Mn1.5O4 cathode (78%, 24 mAh g−1). Furthermore, differential scanning calorimetry result confirms the enhanced thermal stability of LiNi0.5Mn1.5O4 after YF3 coating. These findings open up chance to prepare high performance LiNi0.5Mn1.5O4 cathode and promote development of LIBs with high energy density.

Al-doped Li1.21[Mn0.54Ni0.125Co0.125]O2 cathode material with enhanced electrochemical properties for lithium-ion battery

Layered Li-rich Mn-based oxides are believed to be a good candidate for cathode material in the next generation of lithium-ion batteries. However, they have some disadvantages, such as low initial coulombic efficiency, low rate capacity, and deficient cyclability. To overcome these shortcomings, various approaches, such as elemental doping, have been adopted. In this study, Al-doped Li1.21Mn0.54Ni0.125Co0.125O2 were successfully synthesized using the sol–gel method. Samples were characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), surface-area analysis, field emission scanning electron microscopy and transmission electron microscopy (TEM). Measurements of galvanostatic charge discharge and electrochemical impedance spectroscopy were also performed to evaluate the electrochemical performance of the prepared samples. The XRD patterns showed that all the samples with the structure of 0.55Li2MnO3.0.45LiNi0.33Mn0.33Co0.33O2 had a composite material with two individual layered structures that are integrated with each other. By doping Al, the lattice parameters of the samples changed. The first discharge capacity of the Al-doped specimens was lower than that of the pristine sample. In cycling performance results, it is clear that cyclic behavior and capacity stability rate in doped samples have improved compared to the undoped sample, and in the meantime, the sample with 0.05 aluminum doping has shown the best performance. Optimal performance of the doped specimens can be related to lower load transfer resistance and better structural stability.

Superior lithium-ion storage performance of hierarchical tin disulfide and carbon nanotube-carbon cloth composites

Tin-based composites are promising anode materials for high-performance lithium-ion batteries (LIBs); however, insufficient conductivity, as well as fatal volume expansion during cycling lead to poor electrochemical reversibility and cycling stability. In this work, we demonstrate the lithium-ion storage behaviors of SnS2 anode material deposited on different electrode supports. The SnS2 grown on 3D hierarchical carbon nanotube-carbon cloth composites (SnS2-CNT-CC) shows superior capacity retention and cycle stability, compared to that on planar Mo sheets and carbon cloth. The specific capacity of SnS2 on Mo, CC, and CNT-CC is around 240, 840, and 1250 g−1, respectively. The SnS2-CNT-CC electrode outperforms in the cyclic performance and rate capability compared to other electrode configurations due to the multi-electron pathway and high surface area derived from 3D hierarchical CNT-CC electrode support. Furthermore, a significant decrease in the charge transfer resistance is observed by utilizing 3D hierarchical CNT-CC electrode support. The use of 3D hierarchical structures as electrode support could be the best alternative to enhance the electrochemical performances for the next generation LIBs.

Atomistic mechanism of cracking degradation at twin boundary of LiCoO2

Abstract Intergranular cracking at grain boundary is a well-known mechanical degradation for layered cathodes, which can trigger many detrimental consequences to degrade the cycling performance. To date, the atomistic mechanism of crack, especially the kinetic nucleation process, is still far from clear. Herein, we investigate the cracking mechanism at a coherent grain boundary, twin boundary in LiCoO2, by virtue of atomic resolution electron microscopy. Based on crack's nucleation and evolution process, two kinds of cracks are identified, the cleavage crack and the decomposition crack. The former is a typical deformation induced mechanical failure, featuring the electrochemomechanical fatigue degradation. The latter is formed due to thermodynamic decomposition, acting as the dominant cracking nucleation mechanism during high voltage cycling. Our work also demonstrates that twin boundary as an intrinsic planar defect energetically favors cracking, phase transformation and void formation, which stresses that stabilizing grain boundary mechanically and thermodynamically is vital towards high voltage usage of LiCoO2 and other layered cathodes for next generation lithium ion battery.

Preparation and electrochemical performance of silicon@graphene aerogel composites for lithium-ion batteries

Silicon/graphene composites are recently received more attention as promising negative electrode materials for the next generation lithium-ion batteries (LIBs) due to the synergistic effect of silicon and graphene. Silicon can provide high specific charge capacity, relatively low discharge potential, environmental compatibility and considerable abundance, while graphene exhibits excellent electrical conductivity, flexibility and large space for silicon expansion in the charge process. Herein, we adopted a simple hydrothermal method to obtain a silicon@graphene aerogel (Si@GA) composite with highly dispersible morphology and three-dimensional porous structure. The electrochemical characterizations prove that the Si@GA composite has excellent cycle performance and moderate rate performance during charge/discharge process. After 100 cycles, the specific charge capacity remains above 1330 mAh g−1 at 0.2 A g−1, and above 600 mAh g−1 at 2 A g−1, respectively. The excellent electrochemical performance of the composite may be attributed to the existence and specific structure of GA, which can improve the electrical conductivity and act as a buffer matrix to stabilize the composite electrode material. The composite material may promote the further application of silicon negative electrode materials.

Rational Design and Mechanical Understanding of Three-Dimensional Macro-/Mesoporous Silicon Lithium-Ion Battery Anodes with a Tunable Pore Size and Wall Thickness.

Silicon is regarded as one of the most promising next generation lithium-ion battery anodes due to its exceptional theoretical capacity, appropriate voltage profile, and vast abundance. Nevertheless, huge volume expansion and drastic stress generated upon lithiation cause poor cyclic stability. It has been one of the central issues to improve cyclic performance of silicon-based lithium-ion battery anodes. Constructing hierarchical macro-/mesoporous silicon with a tunable pore size and wall thickness is developed to tackle this issue. Rational structure design, controllable synthesis, and theoretical mechanical simulation are combined together to reveal fundamental mechanisms responsible for an improved cyclic performance. A self-templating strategy is applied using Stöber silica particles as a templating agent and precursor coupled with a magnesiothermic reduction process. Systematic variation of the magnesiothermic reduction time allows good control over the structures of the porous silicon. Finite element mechanical simulations on the porous silicon show that an increased pore size and a reduced wall thickness generate less mechanical stress in average along with an extended lithiation state. Besides the mechanical stress, the evolution of strain and displacement of the porous silicon is also elaborated with the finite element simulation.

A Scalable Silicon Nanowires-Grown-On-Graphite Composite for High-Energy Lithium Batteries

Silicon (Si) is the most promising anode candidate for the next generation of lithium-ion batteries but difficult to cycle due to its poor electronic conductivity and large volume change during cycling. Nanostructured Si-based materials allow high loading and cycling stability but remain a challenge for process and engineering. We prepare a Si nanowires-grown-on-graphite one-pot composite (Gt-SiNW) via a simple and scalable route. The uniform distribution of SiNW and the graphite flakes alignment prevent electrode pulverization and accommodate volume expansion during cycling, resulting in very low electrode swelling. Our designed nanoarchitecture delivers outstanding electrochemical performance with a capacity retention of 87% after 250 cycles at 2C rate with an industrial electrode density of 1.6 g cm-3. Full cells with NMC-622 cathode display a capacity retention of 70% over 300 cycles. This work provides insights into the fruitful engineering of active composites at the nano- and microscales to design efficient Si-rich anodes.

First-principle calculations of lithium adsorption and diffusion on titanium-based monolayers

Rechargeable lithium-ion batteries with excellent mobility and intrinsic safety have attracted great attention for energy storage applications. The performance of electrode materials greatly impacts the development of lithium-ion batteries Titanium-based. 2D materials such as TiO2, Ti2C, and TiCl2, with a high surface-to-mass ratio and excellent surface morphology exhibit a significant promising application on lithium-ion batteries. In this paper, first-principle calculations are carried out to investigate the electronic structure, Li storage capability and diffusion pathway of TiO2, Ti2C, TiCl2 monolayers. The results indicate that TiO2, Ti2C, and TiCl2 monolayers were slightly doped by lithium ions and show metallic electronic structures. According to NEB calculations, TiO2, Ti2C possessed very low diffusion energy barrier and high ion hopping rate of 7.5 × 1010 s−1 and 1.92 × 1012 s−1, respectively. The calculated capacities for the single-layer lithium ion adsorption of TiO2 and Ti2C is 670, 496 mA h g−1. We also explored the double-layer lithium-ion adsorption characteristics on TiO2 and Ti2C surfaces, which greatly enhance the theoretical lithium storage capacity of the material (1342, 995 mA h g−1). Accordingly, that TiO2 with hexagonal fluorite-like (111) morphology was promising for anode materials in new generation lithium-ion batteries.

Synthesis of a microporous poly-benzimidazole as high performance anode materials for lithium-ion batteries

Heteroatom-rich two-dimensional graphene-like structure polymers are highly demanded as high-performance anode materials for lithium ion batteries. Here, a new microporous poly-benzimidazole (MPBI) is accomplished by a condensation reaction between pyromellitic acid and 1,2,4,5-tetraaminobenzene in polyphosphoric acid medium. After heat-treatment at 550 °C, the integrated frame structure of the obtained MPBI-550 remains unchanged without the residual edge groups. Due to the holey pore framework, nitrogen-rich aromatic rings and two-dimensional graphene-like structure, MPBI-550 is suitable for lithium-ion battery anode. It exhibits a remarkable long cycling life, high reversible capacity of 700 mAh g−1 (at 1 A g−1) after 500 cycles and a good rate performance. Such a low-cost and high-performance material constitutes a step towards the design and manufacture of functional anode materials for next generation lithium-ion batteries.

Synthesis and stored performance of LiNi0.8Co0.17Al0.03O2 cathode material prepared by using a flocculation precipitation process

Layered lithium nickel cobalt aluminum oxides cathode materials (α-NaFeO2 structure, Space group: R-3 m) are prepared using an unusual flocculation precipitation process. The synthesis strategy utilized the new aluminum precursor containing nickel, cobalt and aluminum hydroxides has a different mechanism from that for conventional coprecipitation process. As-prepared LiNi0.85Co0.17Al0.03O2 delivers a first cycle capacity of 164 mAh g−1 at 1C rate. The stored sample delivers a first cycle capacity of 146 mAh g−1 and the capacity retention rate of 93% in 40 cycles at 1C rate. Its stored cell exhibits a capacity of 99 mAh g−1 at 1C rate. The particle surface of the sample has a coating layer of Li3.62aLi4.31bNi0.172+Ni0.833+Co0.062+Al0.373+O0.98aO12.6b (with the structure of Li2CO3, LiAl5O8 and α-NaFeO2). The coating layer can prevent the reaction between the particles and moisture in the air or the particles and electrolytes in the cell at 55 °C. Therefore, LiNi0.85Co0.17Al0.03O2 exhibits excellent rate performance and stored one for its low polarization, high stability α-NaFeO2 structure and high stable coating layer. The exceptional overall performance of the as-synthesized LiNi0.85Co0.17Al0.03O2 presents itself a promising cathode material for next generation lithium-ion batteries.

Beyond cell parameters: Exploiting cell operation towards optimizing the SEI and suppressing dendrite growth on lithium metal anodes

AbstractLithium metal electrodes are regarded as the optimal anode for next generation lithium ion batteries especially in the lithium‐sulfur architecture. Unfortunately, the lithium metal anode falls subject to several challenges such as dendrite formation and low Coulombic efficiency, which inhibit its candidacy as a viable technology. As such, substantial research efforts alter cell parameters in effort to manipulate interfacial chemistries, mitigate dendrite growth, and improve cyclability. Unlike conventional efforts, we demonstrate a practical cell operation approach to reinforce the Solid Electrolyte Interphase in lithium anodes via a refined formation protocol governed by the redox reactions found in lithium‐sulfur systems. Galvanostatic and electrochemical impedance data on Li‐Li symmetrical cells reveal that cell operation during the formation phase plays a critical role on interface stability of lithium metal anodes. Li‐Li symmetrical cells subject to our refined protocol, P2, displayed advantages in steadily enduring high cycling currents of 6 mA with minimal polarization, and in lowering the charge transfer resistance at the cell interfaces by a fourfold when compared to cells subject to conventional formation protocols. Additionally, scanning electron microscopy images demonstrate that our formation protocol significantly minimizes the size and dispersion of lithium dendrites, as well as the degree of plated lithium. These effects are enabled by the reinforced SEI formed during P2 which offers a stable ratio between the rates of lithium intercalation to lithium deposition. Microcomputerized tomography characterization further supports these findings by revealing that P2 averts dendrite nucleation sites, and yields greater quantity of SEI species, encompassing 41.1% volume of the entire anode, compared to just 21.5% from the common formation protocol found in literature. Overall, this approach deviates from the convention of materials exploration yet highlights the importance of understanding the nature of interfacial chemistries in response to cell operation. We believe the transferability of this approach has the potential to expedite the commercialization of next‐generation lithium ion technologies.

The effect of carboxyl group position of pyrazinedicarboxylic acid on electrochemical performances in lithium ion batteries anode

Conjugate carbonyl compounds are considered to be one of the most promising electrode materials for the next generation of lithium ion batteries. However, most of the published researches focus on the electrochemical performances of conjugated carbonyl compounds, the researches on the structure-activity relationship of such materials are still not enough. In this work, we investigate the structure-activity relationship of pyrazinedicarboxylic acid (Pzdc) anode materials, and the results show that the lithium storage capability of 2, 3-Pzdc is much better than 2, 5-Pzdc and 2, 6-Pzdc. At 32 mA g−1, 2, 3-Pzdc is able to deliver a discharge capacity around 1200 mA h g−1, while 2, 5-Pzdc and 2, 6-Pzdc anodes only exhibit a capacity of 530 and 550 mA h g−1, respectively. Even at 32 A g−1, 2, 3-Pzdc still retains ca. 500 mA h g−1, and shows 1225 mA h g−1 after 400 cycles at 160 mA g−1 charge and 640 mA g−1 discharge. The combination of electrochemical and spectroscopic studies show that the good electrochemical performance of the 2, 3-Pzdc anode is because of the high lithium conductivity, the low resistance, the stable solid electrolyte interface film form on the electrode, as well as the rich lithium storage functional groups.

Dual-engineered separator for highly robust, all-climate lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as a promising candidate of next generation lithium batteries by virtue of high theoretical energy density, low cost and eco-friendliness, yet their commercialization still suffers from undesirable polysulfide shuttling and uncontrollable Li dendrites growth. Herein, a dual-engineered separator is designed through double-side construction of ammonium alcohol polyvinyl phosphate/carbon black (AAPP/CB) constituted “polysulfide stockroom” and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) based “ion guider” on a commercial polypropylene (PP) substrate. Such functional separator AAPP/CB@PP@LAGP enables highly robust, all-climate Li-S batteries, which is attributed to the efficient polysulfide-absorption/conversion function of the AAPP/CB layer and uniform Li ion distribution/transport capacity induced by the LAGP layer. It is anticipated that this work may provide a promising strategy for interface engineering of separators and promote the wide-temperature application of Li-S batteries.

Flower-like hierarchical Li1.2Ni0.13Co0.13Mn0.54O2 by architectural design for lithium-ion batteries with superior capacity retention

In this work, hierarchical flower-like Li1.2Ni0.13Co0.13Mn0.54O2 (LNCM) with exposed {010} planes assembled and double-sphere Li1.2Ni0.13Co0.13Mn0.54O2 without {010} planes as a comparison were successfully synthesized via a simple solvothermal method. The diffusion of Li+ could be enhanced in the flower-like LNCM with exposed {010} active planes, and the cathode exhibits a superior electrochemical performance especially in long-term cycling stability even at high current densities. The initial discharge capacity of this sample is 274 mA h g−1 at 0.1C (25 mA g−1), with corresponding initial coulombic efficiencies of 77%. Especially, the capacity retention reaches up to 98% at 1250 mA g−1 current density after 100 cycles. By comparing with other LNCM materials reported recently, our optimal cathode has a pretty outstanding electrochemical performance, which is promising for the next generation lithium ion batteries.

The sandwiched buffer zone enables porous SnO2@C micro-/nanospheres to toward high-performance lithium-ion battery anodes

With high theoretical specific capacity and relatively safe working potential, SnO2 has drawn widespread attention as a promising candidate of advanced anode for next generation lithium-ion batteries. However, the practical application of SnO2 anode in lithium-ion batteries is severely blocked by some shortcomings such as the inferior rate capability, fast capacity decay and low initial coulombic efficiency during charge/discharge process. Gratifyingly, there are many works which have demonstrated that the SnO2 anode achieves extra improvement in lithium storage performance after being reduced to nanoscale and embedded into porous carbon matrixes. Herein, porous SnO2@C micro-/nanospheres with a sandwiched buffer zone resulted from unevenly radial distribution of pores in carbon micro-/nanospheres are prepared for the first time. These SnO2@C micro-/nanospheres consist of small SnO2 nanoparticles embedded within porous carbon micro-/nanospheres with a sandwiched buffer zone. The results of this study indicate that the sandwiched buffer zone of carbon micro-/nanospheres and the confinement effect of nanopores on small SnO2 nanoparticles synergistically contribute to outstanding structural stability and excellent electrochemical performance of thus porous SnO2@C micro-/nanospheres. Besides, it is found that the lithium storage performance of the SnO2@C micro-/nanospheres can be tuned by adjusting the SnO2 contents. As a result, the as-prepared SnO2@C micro-/nanospheres with an optimalizing SnO2 content exhibit the best performance, delivering a high capacity of 955 mAh g−1 at 200 mA g−1 after 250 cycles as well as a high capacity of 836 mAh g−1 at even 1000 mA g−1 after 350 cycles.

Critical roles of RuO2 nano-particles in enhancing cyclic and rate performance of LISICON Li3V2(PO4)3 cathode materials

LISICON-type Li3V2(PO4)3 (LVP) is a promising candidate of cathode material for the next generation of lithium ion batteries. Nevertheless, the poor conductivity restricts its practical applications. Carbon coating can improve the deficiency to some extent, but the practical application of LVP is still hindered because of its inert reaction kinetics, unstable electrode structure and side-reaction. Thereby, it is still very insufficient to obtain the satisfied electrochemical performance by the simple modification of carbon coating. Herein, LVP/C@RuO2 composites are designed and characterized. The RuO2/C hybrid layer consists of RuO2 nanoparticles embedded in amorphous carbon. Benefitting from this unique design, the electronic conductivity, Li+ migration rate and structural stability can be remarkably improved. As a result, LVP/C-5 delivers a high initial capacity of 167.8 mAh g−1 at 0.2 C and superior long-term cycling performance of 81.2 mAh g−1 after 1000 cycles at 10 C. Moreover, LVP/C-5 exhibits good thermal stability (55 °C), giving a high reversible capacity of 116 mAh g−1 after 350 cycles at 5 C. More importantly, the LVP/C@RuO2 possesses a facile technical procedure, excellent electrochemical property, and shows significant potential to apply in large-scale production. Our study provides a potential reference for optimizing electrochemical properties through low dosage of carbon and low metallic oxide amount.