Uniform Li-ion Research Articles

An effective solid-electrolyte interphase for stable solid-state batteries

An effective solid-electrolyte interphase for stable solid-state batteries

Expandable crosslinked polymer coatings on silicon nanoparticle anode toward high-rate and long-cycle-life lithium-ion battery

Porous and electrically conductive coating on silicon nanoparticles (Si NPs) anode can mitigate the volume expansion during charging or discharging in Li-ion battery (LIB) while conventional protection coating process resulted in non-uniform polymer shell which show low volumetric or areal capacities. Here, we demonstrated that ultra-thin polyacrylonitrile layer can be formed conformally by emulsion-assisted coating process and cross-linked on Si NPs (Si@x-PAN) producing stable and expandable polymer shell which showed a highly stable long-term cycling ability. Areal and specific capacities of Si@x-PAN were an ∼ 2 mAh/cm2 and a 2000 mAh/g, respectively. Importantly, we found that capacity decay was only 5 % after 100 cycles and>75 % of capacity was retained even after 1000 cycles (0.5C/0.5C) with the help of a uniform Li-ion current around the Si NPs during continuous charging and discharging. To our knowledge, this long-term stability at reasonable loading levels is one of the highest levels of performance in pure Si anode systems.

Sandwiched Li plating between Lithiophilic-Lithiophobic gradient Silver@Fullerene interphase layer for ultrastable lithium metal anodes

Constructing a multi-functionally artificial interphase layer is an emerging strategy to possibly address the issues of inhomogeneous Lithium (Li) nucleation and dendrite growth. In this study, a silver@fullerene (Ag@C60) interphase layer with lithiophilic-lithiophobic gradient was designed, which was fabricated by series of deposition of silver and fullerene (Ag@C60) on Cu foam current collector (ACCF). In this way, the typically uncontrolled Li deposition process will become a highly nucleation-guided process, due to the preferentially induced Li nucleation of Ag nanoparticles, which will guide the Li deposition sandwiched in C60 and Ag layers. While the top lithiophobic fullerene layer is beneficial for regulating uniform Li-ion flux and facilitating the formation of LiF-rich SEI layer, finally suppressing the top deposition of Li metal, due to the high nucleation energy barrier on fullerene. Consequently, Li@ACCF exhibits a low overpotential of 14 mV and an ultra-stable cyclic life for more than 2500 h in symmetric cells. Besides, it also displays excellent long-term cycle life and high-rate performance in lithium-metal full cells. This deliberate design of the “push–pull” Li could ensure the uniform Li deposition sandwiched fullerene and silver layers and provide a feasible and efficient approach to advance the practical use of lithium-metal anodes for high-energy–density batteries.

High Interfacial-Energy and Lithiophilic Janus Interphase Enables Stable Lithium Metal Anodes.

The stability of solid electrolyte interphase (SEI) layers is critical for developing lithium (Li) metal batteries. However, the fabrication of stable SEI layers is plagued by un-controlled structures, properties, and functions. Here a controllable design of an ordered LiF-rich and lithiophilic hybrid Janus interphase (LiF-HJI) is reported using organic fluorination reagent as a functional SEI precursor. The LiF-HJI with a lower crystalline LiF layer and an upper Li organosulfide layer provides high interfacial energy with the Li metal and strong Li-ion affinity, allows homogenous Li-ion distribution, fast and uniform Li-ion transport, and excellent mechanical and passivation properties, enabling stable Li metal anodes under harsh conditions, such as high deposition capacities (6mAhcm-2 ), current densities (10mAcm-2 ), and rates (5 C). Stable LiF-HJI@Li greatly improves cycling stability and capacity retention (80.1% after 300 cycles) of Li||LiNi0.8 Co0.1 Mn0.1 O2 cells at a commercial-level areal capacity (≈4.2mAhcm-2 ). Even under a lean-electrolyte condition of 3gAh-1 , 80% capacity retention can be maintained after 100 cycles, demonstrating excellent cycling performance under such harsh conditions.

Guiding Uniformly Distributed Li-Ion Flux by Lithiophilic Covalent Organic Framework Interlayers for High-Performance Lithium Metal Anodes.

Lithium (Li) metal anodes are regarded as prospective anode materials in next-generation secondary lithium batteries due to their ultrahigh theoretical capacities and ultralow potentials. However, inhomogeneous lithium deposition and uncontrollable growth of lithium dendrites always give rise to the low lithium utilization, rapid capacity fading, and poor cycling performance. Herein, we design the lithiophilic covalent organic frameworks (COFs) containing preorganized triazine rings and carbonyl groups as the multifunctional interlayer in lithium metal batteries (LMBs). Triazine rings rich in lone pair electrons can act as the donor attracting Li ions, and carbonyl groups serve as Li-anchoring sites effectively coordinating Li ions. These periodic arranged subunits significantly guide uniform Li ion flux distribution, guarantee smooth Li deposition and less lithium dendrite formation. Consequently, the symmetric batteries with COF interlayers exhibit an extraordinary cycling stability for more than 2450 and 1000 h with ultralow polarization voltage of about 12 and 14 mV at 0.5 and 1.0 mA cm-1. Coupling with sulfur (S) cathodes and LiFePO4 (LFP) cathodes, the full cells also demonstrate superb energy density achievement and rate performance. With introducing lithiophilic COFs interlayers, the Li-LFP batteries exhibit high capacity of 150 mAh g-1 and 86% capacity retention after 450 cycles at 0.5 C.

Dendrite-Suppressing Separator with High Thermal Stability Modified by Beaded-Chain-Like Polyimide Coating for a Li Metal Anode

Dendritic Li growth is the root hurdle against the implementation of a Li metal anode because it brings safety issues and unsatisfactory efficiency. In this work, a beaded-chain-like polyimide (PI) coating is designed on the commercial polyethylene (PE) separator to suppress the Li dendrite. Owing to the compactly stacking structure and high Li-ion absorption of the PI coating, the wettability of the prepared PI-PE separator is improved and a Li-ion-rich layer with uniform Li-ion transfer channels forms on the surface of the Li metal anode. Therefore, the planar Li deposition rather than dendrite growth has been achieved using this custom separator. The life spans of Cu||PI-PE||Li half-cells have been extended to 7 and 4 times longer than that of Cu||PE||Li half-cells at a current density of 1 mA/cm2 with deposition capacities of 0.5 and 1 mA h/cm2, respectively. Besides suppressing Li dendrites, the multifunctional PI-PE separator also delivers a higher thermal stability to 120 °C than commercial PE and Al2O3-PE separators. This facile approach provides a feasible strategy to realize smooth lithium deposition, and the fundamental mechanism underlying the combination of pore structure and surface chemistry may lead to new approaches to tackle the dendritic problem of Li deposition.

Robust Conversion-Type Li/Garnet interphases from metal salt solutions

Garnet-type Li7La3Zr2O12 (LLZO) electrolytes show considerable potentials in solid-state Li metal batteries, yet the serious interfacial problem has hindered its practical application. Herein, we propose a facile strategy to construct conversion-type metal oxides (eg. PbO, ZnO or Co3O4) as lithiophilic layers on garnet surface from metal salt aqueous solutions. Robust garnet/Li interface and greatly reduced interfacial resistance to as small as ~ 10 Ω cm2 can be obtained. Combined with experimental analysis and theoretical calculation (ΔG), the mechanism of lithiophilicity of different metal oxides was explained. The mixed ionic and electronic conductive interlayer which can lead to uniform Li-ion flow is superior to the electronic conductive metal interlayer with poor ionic conductivity causing gradual failure of the interface. As expected, the Li|PbO/LLZTO/PbO|Li cells show the improved critical current density of 1.1 mA cm−2 and excellent cycling stability for 1000 h at 0.3 mA cm−2. With PbO modified garnet, LiNi0.5Co0.2Mn0.3O2|garnet|Li cells operate well at room temperature and all-solid-state LiFePO4/PEO|garnet|Li cells run stably at 0.3 mA cm−2 for at least 100 cycles at 60 ℃.

Superorganophilic MAF-6/PP Composite Separator Boosts Lithium Metal Anode Performance

Practical application of lithium metal anodes in high-energy rechargeable batteries is impeded by the issue of Li dendrite growth. Herein, an exceptional hydrophobic MAF-6 material is utilized to modify polypropylene (PP) separator to yield a superorganophilic MAF-6/PP composite separator. Owing to a combination of superorganophilicity with three-dimensional ordered porosity, the MAF-6/PP achieves a Li ion transference number of 0.78. Homogeneous and dense Li plating behaviors are present in cells with MAF-6/PP which can afford uniform Li ion flux. The MAF-6/PP enables Li|Cu cells to run steadily for over 350 cycles at 0.5 mA cm−2-1 mAh cm−2 with an average coulombic efficiency (CE) of 98.8%, symmetric Li|Li cells to work stably for 2200 h without short-circuit at 0.5 mA cm−2-1 mAh cm−2, and Li|LiFePO4 cells to retain a reversible capacity of 102.4 mAh g−1 after 1500 cycles at 1C with a capacity retention of 73.2% and a CE of 99.9%.

PVP-bridged γ-LiAlO2 nanolayer on Li1.2Ni0.182Co0.08Mn0.538O2 cathode materials for improving the rate capability and cycling stability

Li-rich layered materials have been considered as promising cathode materials for next-generation lithium-ion batteries due to their high capacity (≥250 mAh g−1). Unfortunately, this type of cathode material still suffers from intrinsic deficiencies of capacity fading and side reactions. Surface coating with a protective layer can resolve the above problems to some extent, whereas normal coating strategies still suffer from process complexity and are difficult to prevent phase separation that leads to the formation of an independent miscellaneous phase. Herein, we report an effective PVP-bridged coating method, in which the PVP molecules can bridge the gap between the coating shell and the electrode material core through hydrogen bonding and functional groups. Utilizing this strategy, a uniform Li-ion conductor γ-LiAlO2 nanolayer with a thickness of 7 nm is successfully formed on the surface of the Li1.2Ni0.182Co0.08Mn0.538O2 cathode material, which leads to an excellent rate capability (177.0 mAh g−1 delivered at 5 C) and superior cycling stability (89.3% capacity retention achieved after 100 cycles at 10 C) for the composite material. Furthermore, the exothermic reaction for the composite material takes place at a higher temperature (234.1 °C) relative to the uncoated sample (220.9 °C), implying its improved thermal stability. Galvanostatic intermittent titration technique and density functional theory calculation demonstrate a higher Li+ diffusion coefficient for the γ-LiAlO2 coated sample and a lower Li+ diffusion energy barrier in γ-LiAlO2. Based on the promising results, the PVP-bridged coating strategy presented in this study provides a new perspective in material design towards high-performance Li-rich cathode materials for lithium-ion batteries.

Fast Li-ion transport and uniform Li-ion flux enabled by a double–layered polymer electrolyte for high performance Li metal battery

Polymer–based lithium metal batteries are considered to be one of the most promising Li–based energy storage systems for portable devices and flexible technologies. However, low ionic conductivity of polymer electrolytes and poor compatibility in electrode–electrolyte interfaces restrict the wide applications of polymer–based lithium metal batteries. Here we report a novel polycarbonate–polyethylene oxide based polymer electrolyte with a double layered structure to achieve fast Li–ion conduction and uniform Li-ion flux. Comprehensive experiments and simulations show the ion-dipolar pair of [C=O...Li+] is the main reason for Li+ conduction, and the balances of coupling/decoupling in Li+…TFSI– and Li+…PAN/PVEC synergistically facilitate a fast Li+ transport on the cathode side, which results in high Li+ transference number (0.602) and high ionic conductivity (1.56 × 10–4 S cm–1, 20 °C) of DLPE. Besides, uniform Li+ flux in PEGDMA-SiO2-Pyr14TSFI achieves stable Li/electrolyte interface rich in LiF and Li3N on the anode side. Benefit from this design, the DLPE–based LiFePO4 and LiNi0.8Co0.1Mn0.1O2 battery deliver high safety and high stable performances under various extreme conditions.

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.

Rational Design of Sandwich-Like “Gel–Liquid–Gel” Electrolytes for Dendrite-Free Lithium Metal Batteries

Issues of lithium dendrite growth still hinder the popular application of lithium metal batteries (LMBs). Herein, we demonstrate that “gel–liquid–gel” electrolytes effectively suppress the growth of dendrites. This sandwich structure is based on introducing gel polymer coating layers, which consist of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), onto both sides of a Celgard separator. The PVDF-HFP layers improve the overall liquid electrolyte retention and compatibility with lithium anodes. They also lead to a uniform Li-ion flux at the polymer/lithium interface, which results in the suppression of dendrite nucleation. Impressively, Li|Cu cells operate stably for over 400 cycles with a high Coulombic efficiency of ∼98%. Li|Li symmetric cells enable highly stable Li plating/stripping cycling for over 1200 h at 1 mA cm–2. Li|LiFePO4 full cells also exhibit excellent cycling performance. We expect this work to have great potential in the application of simple composite gel polymer electrolytes to achieve highly safe LMBs.

Regulated lithium ionic flux through well-aligned channels for lithium dendrite inhibition in solid-state batteries

The utilization of solid electrolyte (SE) to suppress lithium (Li) dendrites is promising but still far from satisfactory due to the inhomogeneous Li plating/stripping. Here, we demonstrated a novel strategy to inhibit Li dendrites via regulating Li-ion flux in SE by using vertically aligned channels. The ion-insulating walls facilitated uniform distribution of Li-ion flux through the channels, leading to a homogeneous Li deposition, thus alleviating Li dendrite formation. As a result, symmetric cells with this SE exhibited excellent long-term stability (1000 ​h) against Li metal. In addition, Li4Ti5O12 (LTO)/Li cell with the developed SE achieved good battery performance over 100 cycles. The mechanism for dendrite suppression was further investigated by phase-field simulation. This work provides a novel strategy by manipulating uniform Li-ion flux to fabricate SE to inhibit Li dendrites and facilitates the development of high-performance rechargeable Li batteries.

A gelatin-based artificial SEI for lithium deposition regulation and polysulfide shuttle suppression in lithium-sulfur batteries

Abstract Lithium-sulfur (Li-S) battery is one of the best candidates for the next-generation energy storage system due to its high theoretical capacity (1675 mA h−1), low cost and environment friendliness. However, lithium (Li) dendrites formation and polysulfide shuttle effect are two major challenges that limit the commercialization of Li-S batteries. Here we design a facile bifunctional interlayer of gelatin-based fibers (GFs), aiming to protect the Li anode surface from the dendrites growth and also hinder the polysulfide shuttle effect. We reveal that the 3D structural network of GFs layer with abundant polar sites helps to homogenize Li-ion flux, leading to uniform Li-ion deposition. Meanwhile, the polar moieties also immobilize the lithium polysulfides and protect the Li metal from the side-reaction. As a result, the anode-protected batteries have shown significantly enhanced performance. A high coulombic efficiency of 96% after 160 cycles has been achieved in the Li-Cu half cells. The Li-Li symmetric cells exhibit a prolonged lifespan for 800 h with voltage hysteresis (10 mV). With the as-prepared GFs layer, the Li-S battery shows approximately 14% higher capacity retention than the pristine battery at 0.5 C after 100 cycles. Our work presents that this gelatin-based bi-functional interlayer provides a viable strategy for the manufacturing of advanced Li-S batteries.

Evaluation of Porous Ni(Zn) Materials As 3D Matrices for Li Metal Electrodes

Due to its very high theoretical capacity (3861 mAh g-1 or 2062 mAh cm-3) and low redox potential (-3.04 V vs standard hydrogen electrode), lithium metal is one of the most attractive anode materials for batteries. However, its use in rechargeable batteries such as Li-S and Li-air batteries is problematic due to the uncontrolled formation of lithium dendrites during charge/discharge cycling, which can induce cell short circuit, aggravated adverse reactions, dead Li formation, polarization increase and large volume changes, resulting in safety concerns and low coulombic efficiencies. Various strategies have been evaluated to prevent the growth of Li dendrites such as: (i) electrolyte engineering for modifying the physicochemical properties of the solid electrolyte interphase and better regulating the current distribution during Li deposition; (ii) interface engineering by covering the Li surface with a protective coating before cycling; (iii) use of solid electrolyte or reinforced separator to mechanically block Li dendrite propagation and (iv) development of 3D substrates inducing a more uniform Li-ion flux in addition to act as stable hosts that guide Li plating and minimize the electrode volume variation upon cycling [1-3].According to this latter strategy, the present study is focused on porous Ni and Ni-Zn electrodes elaborated by the dynamic hydrogen bubble template (DHBT) method [4]. The Li wettability of these electrodes as a function of their porosity and composition will be presented. Their ability to better control lithium dendritic growth will be discussed on the basis of cycling experiments in Li/S batteries, electrochemical dilatometry experiments and operando optical microscopy analyses. References [ 1 ] X.B. Cheng, R. Zhang, C.Z. Zhao, Q. Zhang, Toward safe lithium metal anode in rechargeable batteries: a review, Chem. Rev 117 (2017) 10403-10473. [ 2 ]X.B. Cheng, J.Q. Huang, Q. Zhang, Review-Li metal anode in working lithium-sulfur batteries, J. Electrochem. Soc. 165 (2018) A6058-A6071. [ 3 ] D. Lin, Y. Liu, Y. Cui, Reviving the lithium metal anode for high-energy batteries, Nat. Nanotechnol. 12 (2017) 194-206. [ 4 ] M. Hao, V. Charbonneau, N. N. Fomena, J. Gaudet, D. R. Bruce, S. Garbarino, D. A. Harrington, D. Guay, . Hydrogen Bubble Templating of Fractal Ni Catalysts for Water Oxidation in Alkaline Media. ACS Appl. Energy Mater. 2 (2019) 5734-5743.

A smart lithiophilic polymer filler in gel polymer electrolyte enables stable and dendrite-free Li metal anode

A new conceptional lithiophilic polymer-filler-reinforced gel polymer electrolyte was proposed and prepared to guide uniform Li-ion flux during the Li plating/stripping process.

Facile and Scalable Modification of a Cu Current Collector toward Uniform Li Deposition of the Li Metal Anode.

The development of lithium metal anodes has been severely impeded by the detrimental lithium (Li) dendrite growth which can largely shorten the lifespan of the battery. Here, we propose a one-step redox strategy to fabricate reduced graphene oxide (rGO) and Cu2O co-modified Cu current collector (rGO-Cu2O/Cu), which can guide the uniform Li ion nucleation and suppress the formation of the Li dendrite. The lithiophilic Cu2O in situ grown on the Cu substrate via direct chemical oxidation of Cu foil by the GO solution can decrease the Li nucleation overpotential and regulate the preferential nucleation of Li ions, while the rGO produced at the same time can facilitate the electron transport. As the consequence of the synergistic effects, rGO-Cu2O/Cu could be fully discharged with largely enhanced Coulombic efficiency of 98% and extended cycling life of the symmetrical cell up to 300 h. The full battery assembled with LiFePO4 also exhibits satisfying electrochemical performance, indicating the promising practical application of this Li-plated rGO-Cu2O/Cu anode. Furthermore, the processable rGO-Cu2O/Cu which can make Li metal anode moldable into various shapes with a controllable size will be favorable to manufacture diverse device architectures.

A scalable bio-inspired polydopamine-Cu ion interfacial layer for high-performance lithium metal anode

The growth of Li dendrites and the instability of the solid electrolyte interphase (SEI) layer during plating/stripping has hindered the practical application of high-energy-density batteries based on a lithium metal anode. Building a stable interfacial layer is effective in preventing lithium corrosion by the electrolyte and controlling the deposition of lithium metal. Here, we present a robust polydopamine-Cu ion (PDA-Cu2+) coating layer formed by the aggregation of nanoparticles and Cu ions, which can be obtained by a subtle immersion strategy. We demonstrate that the PDA-Cu2+ protective layer, with a unique structure comprising nanoparticles, can regulate and guide Li metal deposition, and together with Cu ions, forms a lubricating surface to facilitate uniform Li ion diffusion and induce stable SEI layer formation. Li anodes with this PDA-Cu2+ layer modification ultimately achieve higher Coulombic efficiencies, which are consistently stable for over 650 cycles at 0.5 mA·cm−2 without Li dendrites. The introduced PDA-Cu2+ coating can adhere to any material of any shape; additionally, the operation can be realized on a large scale because of its simplicity. These merits provide a promising approach for developing stable and safe lithium metal batteries.

A New Aspect of the Li Diffusion Enhancement Mechanism of Ultrathin Coating Layer on Electrode Materials.

Atomic layer deposition (ALD) coating on active material particles has been widely considered as an effective and efficient strategy to improve the capacity and cycle life of lithium-ion batteries. One of the key roles of the ALD coating layer is to facilitate the Li ion transfer in electrode particles. Several recent studies demonstrated that an ALD coating layer could significantly improve the effective diffusion coefficients in cathode particles. As such, this enhanced transport property is generally believed to be a result of the higher conductivity of the coating layer itself when compared to that of active materials. However, since the fraction of ALD coating layer is very small, it is questionable that the ultrathin coating layer could lead to such a significant improvement of the diffusivity for the whole particle. Thus, we proposed a new hypothesis about the role of ALD coating layer on Li ion transportation. Due to the agglomeration of particles in an electrode, the surfaces of the particles are partially blocked, and, correspondingly, Li ion intercalation is not uniform over the whole surface. Herein, we propose that the ALD coating could provide a quick path to distribute Li ions over the whole particle surface and allow Li ions to spread uniformly and effectively, leading to improved effective diffusivity of the particles and their utilization. In this work, this hypothesis was validated by simulation and experimental study. It was proved that the particle with an optimal ALD coating thickness has the most uniform Li ion distribution, leading to an optimal discharge capacity. Along with the validation of the hypothesis, a parametric study was conducted by consideration of the flux area, particle size, and current density, which revealed the fundamental role of coating layer on charge transfer, Li ion diffusion, and corresponding battery performance.

Safe LAGP-based all solid-state Li metal batteries with plastic super-conductive interlayer enabled by in-situ solidification

Safe and high-energy-density all solid-state lithium metal batteries (ASSLMBs) are great in demand for future electrical vehicle and grid energy storage. The compatibility of electrode-electrolyte interface is a critical factor influencing the electrochemical performance of ASSLMBs. Herein, we propose a plastic super-conductive carrier to deter untoward reaction between Li anode and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) electrolyte by in-situ solidifying succinonitrile-based plastic interlayer with Li6.4La3Zr2Al0.24O12 (LLZAO) nanowires (l-SN). The method of in-situ solidification promises the low interfacial resistance. The l-SN interlayer can not only act as a physical obstacle to isolate LAGP pellet from Li metal, but also provide three-dimensional ion channels to regulate the transfer of Li ions, delivering an uniform Li ion distribution for dendrite-free Li deposition. The Li|l-SN|LAGP|l-SN|Li symmetric cell can stably cycle for 240 h without short circuit at room temperature (R.T). This approach enables a high specific capacity of 152.5 mAh g−1 at 0.1C for Li|l-SN|LAGP|l-SN|LiFePO4 cells at R.T. Furthermore, the integrated ASSLMBs show excellent cyclic stability at 40 °C with an initial discharge capacity of 168.4 mAh g−1 at 0.5C and retention of 93.17% after 100 cycles. The super-ionic property at the interface makes excellent rate performance of ASSLMBs at 40 °C. This strategy is facile and efficient in promising safe and outstanding ASSLMBs and also has some referential values for other unstable electrolyte interface beyond LAGP.