Fabrication and evaluation of a polymer Li-ion battery with microporous gel electrolyte

This paper introduces an easy method for the fabrication of polymer Li-ion batteries with microporous gel electrolyte (MGE). The MGE is a multiphase electrolyte, which is composed of liquid electrolyte, gel electrolyte, and polymer matrix. The MGE not only has high ionic conductivity and good adhesion to the electrodes at low temperatures, but also retains good mechanical strength at elevated temperatures. Therefore, the MGE batteries are able to operate over a wide temperature range. During battery fabrication, the MGE is formed in situ by introducing liquid electrolyte into a swellable microporous polymer membrane and then heating or cycling the battery. In this work, the chemical compatibility of MGE with metal lithium during 60 °C storage and with LiMn₂O₄ cathode during cycling was studied. In addition, graphite/MGE/LiMn₂O₄ Li-ion batteries were made and evaluated.     

In situ Interweaved Binder Framework Mitigating the Structural and Interphasial Degradations of High-nickel Cathodes in Lithium-ion Batteries

The practical viability of high-nickel layered oxide cathodes is compromised by the interphasial and structural degradations. Herein, we demonstrate that by applying an in situ interweaved binder, the cycling stability of high-nickel cathodes can be significantly improved. Specifically, the results show that the resilient binder network immobilizes the transition-metal ions, suppresses electrolyte oxidative decomposition, and mitigates cathode particles pulverization, thus resulting in suppressed cathode-to-anode chemical crossover and ameliorated chemistry and architecture of electrode-electrolyte interphases. Pouch full cells with high-mass-loading LiNi_0.8Mn_0.1Co_0.1O₂ cathodes achieve 0.02 % capacity decay per cycle at 1 C rate over 1 000 deep cycles at 4.4 V (vs. graphite). This work demonstrates a rational structural and compositional design strategy of polymer binders to mitigate the structural and interphasial degradations of high-Ni cathodes in lithium-ion batteries.     

The Stabilization Effect of CO2 in Lithium–Oxygen/CO2 Batteries

The lithium (Li)–air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O₂), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O₂⁻, and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li-air battery. Even worse, the water and/or CO₂ in air bring parasitic reactions and safety issues. Therefore, applying such systems in open-air environment is challenging. Herein, contrary to previous assertions, we have found that CO₂ can improve the stability of both anode and electrolyte, and a high-performance rechargeable Li–O₂/CO₂ battery is developed. The CO₂ not only facilitates the in situ formation of a passivated protective Li₂CO₃ film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O₂⁻. Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li₂CO₃. The Li–O₂/CO₂ battery achieves a full discharge capacity of 6628 mAh g⁻¹ and a long life of 715 cycles, which is even better than those of pure Li–O₂ batteries.     

过渡金属及其化合物应用于锂硫电池的研究进展

锂硫电池因具有高理论比容量和性价比,被认为是具有发展潜力的新型二次电池。 但是,作为活性物质的单质硫和反应产物是电子绝缘体,充放电过程的中间产物多硫化锂在电解液中易于溶解和迁移引起“穿梭效应”和一系列的副反应,造成活性物质利用率低,电池的电化学稳定性变差。 本文综述了近年来过渡金属纳米材料应用于锂硫电池的研究进展,重点介绍了材料的合成方法以及其抑制多硫化锂溶解并促进其转化的反应机理,并对锂硫电池正极载体材料的发展方向进行了展望。     

Instability of PVDF Binder in the LiFePO4 versus Li4Ti5O12 Li-Ion Battery Cell

The conventional formulation of electrodes used in Li-ion batteries consists of a mixture of three components: an active material, a conductive additive (carbon), and an organic binder. While the first encompasses a broad spectrum of chemistries, the carbon and the binder are often standard elements of the composite, with the latter being, in most of the cathode cases, the polyvinylidene fluoride (PVDF). The high (electro-)chemical inertia spanning over a broad range of oxidative and reductive potentials gives grounds for this choice. Herein, we demonstrate, contrary to electrochemical expectations, that the PVDF is electrochemically unstable at relatively low potentials. We consider in this study the LiFePO₄ (LFP) cathode cycled versus Li₄Ti₅O₁₂ (LTO) anode as a representative low-voltage battery cell system. The binder degradation process starts upon charge on the LFP electrode at 3.45 V vs. Li⁺/Li when the PVDF binder reacts with lithium and forms LiF. The latter does not precipitate on the LFP but migrates/diffuses towards the LTO counter-electrode, following the Li-ions’ trajectory. X-Ray photoelectron spectroscopy complemented with the high lateral resolution of X-ray photoemission electron microscopy disclosed the formation of a thin layer of LiF homogenously distributed across the LTO electrode, which partially dissolves (or decomposes) upon discharge. The degradation of the PVDF and the deposition and dissolution (and/or decomposition) of the LiF layer continue over subsequent charge and discharge cycles. The process is augmented when the cycling temperature is increased to 80 °C. The results shown in this work are crucial to interpret electrochemical data, such as specific charge decay or impedance rise, and have relevance for all PVDF-based electrodes, especially when employed in high-voltage battery cells where the more extreme cycling conditions exacerbate electrode components’ stability.     

Flexible cellulose/LiFePO4 paper-cathodes: toward eco-friendly all-paper Li-ion batteries

Today most of commercial Li-ion batteries (LIBs) are manufactured using toxic solvents and synthetic polymer binders. In order to lower the cost and the environmental impact of LIBs an effort must be made to identify low-cost and environmentally friendly materials and processes. In this work, flexible, self-standing and easily recyclable LiFePO₄ cathodes are obtained using cellulose fibers as biosourced binder and a quick, aqueous filtration process, easily upscalable capitalizing the well-established papermaking know-how. The obtained paper-cathodes show very good mechanical properties, with Young’s modulus as high as 100 MPa, discharge capacity values up to 110 mAh g^?1 and very good cycling performances, comparable with conventional polymer-bonded LiFePO₄ cathodes. Moreover, a complete paper-cell, constituted by a paper-cathode, a paper-separator and a paper-anode is presented, showing good cycling performances in terms of specific capacity, efficiency and stability.     

高性能锂离子电池正极黏合剂研究进展

正极黏合剂是维持锂离子电池正极结构稳定性的关键材料,对于锂离子电池的能量密度及安全性具有重要作用.本文综述了锂离子电池正极黏合剂材料的研究及应用进展,重点介绍了锂离子电池正极黏合剂对于正极材料及锂离子电池电化学性能的影响,详细总结了以聚偏氟乙烯(PVDF)、聚酰亚胺(PI)、功能性聚合物黏合剂为代表的油溶性黏合剂和以聚丙烯酸(PAA)、羧甲基纤维素(CMC)为代表的水溶性黏合剂的特点:PVDF具备良好的化学稳定性,黏合效果较好,但耐高温性能差且在电解液中易溶胀;PI的耐高温性能优异,机械性能较好,但成本相对较高;功能性聚合物黏合剂具备良好的导电性,可有效抑制Li-S锂电池中多硫化物的穿梭效应,但制备工艺复杂;PAA的柔性较好,抗高压能力较强,但是力学性能较差;CMC具有良好的分散性,机械强度较大,因脆性较大需与丁苯橡胶(SBR)配合使用.结合已有的研究报道,探讨了高性能锂离子电池先进正极黏合剂材料的未来发展方向及前景.     

锂离子二次电池用隔膜的制备及其性质

本文采用倒相法制备了锂离子二次电池用的PVDF HFP共聚物型多孔聚合物隔膜 ,该聚合物膜具有良好的机械性能 ,其孔隙率可达 75% ,吸附电解液后增重 4 50 % ,电导率为 10 - 3S/cm ,组装成电池后表现出良好的循环性能和较低的极化率     

Effect of CO2-induced side reactions on the deposition in the non-aqueous Li-air batteries

This paper presents a non-aqueous Li-air battery model that considers the side reactions of lithium carbonate (Li₂CO₃) formation from both electrolyte decomposition and carbon dioxide (CO₂) in the ambient air. The deposition and decomposition behaviors of discharge products, the voltage, and capacity evolutions during the cycling operation of the Li-air batteries are investigated. The deposition behavior analysis implies that the Li₂CO₃ generated by electrolyte decomposition is mainly distributed near the separator side, while it is dominantly generated by Li-O₂/CO₂ reaction near the air side. The formation of Li₂CO₃ by side reactions makes the Li-air batteries exhibit a peak discharge deposition inside the cathode. Moreover, Li₂CO₃ is difficult to decompose and gradually accumulates with cycles, especially near the air side. The severe accumulation of Li₂CO₃ near the air side significantly reduces the O₂ diffusion into the electrode, which induces severe cycling performance decay of the Li-air batteries. According to the distribution and evolution of the deposition, three simple hierarchical cathode structures with high porosities near the air side are finally studied. The simulation results indicate that the increase of the local porosity near the air side substantially improves the cycling performance of the Li-air batteries.

     

四元尖晶石相Li——M——Mn——O(M=Ni,Cr,Mo,V)嵌入电极的研究

制备了用不同价态的几种金属阳离子(Ni2^+,Cr3^+,V5^+,Mo6^+)修饰的尖晶石LiMn~2O~4嵌入化合物作为锂二次电池的阴极材料,对Li/LiM~yMn~2~-~yO~4电池进行了电化学和X射线衍射研究.结果表明,其它离子的掺杂使标准尖晶石LiMn~2O~4电极对锂的反复脱嵌和嵌入有了更强的承受力,但在不同程度上降低了其初始容量.循环性能的提高归于掺杂的金属阳离子使尖晶石结构趋于更稳定.同时还讨论了修饰离子对尖晶石相在充放电时5V电压平台出现的影响。     

Recovery and Reuse of Composite Cathode Binder in Lithium Ion Batteries

Here, we investigate the recovery and reuse of polyvinylidene fluoride (PVDF) binders from both homemade and commercial cathode films in Li ion batteries. We find that PVDF solubility depends on whether the polymer is an isolated powder or cast into a composite film. A mixture of tetrahydrofuran:N-methyl-2-pyrrolidone (THF : NMP, 50 : 50 v/v) at 90 °C delaminates composite cathodes from Al current collectors and yields pure PVDF as characterized by ¹H nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), wide-angle X-ray scattering (WAXS), and scanning electron microscopy (SEM). PVDF recovered from Li ion cells post-cycling exhibits similar performance to pristine PVDF. These data suggest that PVDF can be extracted and reused during Li ion battery recycling while simultaneously eliminating the formation of HF etchants, providing an incentive for use in direct cathode recycling.     

Correlating Polysulfide Solvation Structure with Electrode Kinetics towards Long-Cycling Lithium–Sulfur Batteries

Lithium–sulfur (Li−S) batteries are promising due to ultrahigh theoretical energy density. However, their cycling lifespan is crucially affected by the electrode kinetics of lithium polysulfides. Herein, the polysulfide solvation structure is correlated with polysulfide electrode kinetics towards long-cycling Li−S batteries. The solvation structure derived from strong solvating power electrolyte induces fast anode kinetics and rapid anode failure, while that derived from weak solvating power electrolyte causes sluggish cathode kinetics and rapid capacity loss. By contrast, the solvation structure derived from medium solvating power electrolyte balances cathode and anode kinetics and improves the cycling performance of Li−S batteries. Li−S coin cells with ultra-thin Li anodes and high-S-loading cathodes deliver 146 cycles and a 338 Wh kg⁻¹ pouch cell undergoes stable 30 cycles. This work clarifies the relationship between polysulfide solvation structure and electrode kinetics and inspires rational electrolyte design for long-cycling Li−S batteries.     

基于一体化正极与电解质膜的高性能固态电池

Lithium ion batteries (LIBs) are becoming the most popular energy storage systems in our society. However, frequently occurring accidents of electrical cars powered by LIBs have caused increased safety concern regarding LIBs. Solid-state lithium batteries (SSLBs) are believed to be the most promising next generation energy storage system due to their better in-built safety mechanisms than LIBs using flammable organic liquid electrolyte. However, constructing the ionic conducting path in SSLBs is challenging due to the slow ionic diffusion of Li ion in solid-state electrolyte, particularly in the case of solid-solid contact between the solid materials. In this paper, we demonstrate the construction of an integrated electrolyte and cathode for use in SSLBs. An integrated electrolyte and cathode membrane is obtained via simultaneous electrospinning and electrospraying of a polyacrylonitrile (PAN) electrolyte and a LiFePO₄ (LFP) cathode material respectively, for the cathode layer, followed by the electrospinning of PAN to prepare the electrolyte layer. The resultant integrated PAN-LFP membrane is flexible. Scanning electron microscopy and energy dispersive X-ray spectroscopy measurement results show that the electrode and electrolyte are in close contact with each other. After the integrated PAN-LFP membrane is filled with a succinonitrile-bistrifluoromethanesulfonimide (SN-LiTFSI) salt mixture, it is paired with a lithium foil metal anode electrode, and the resultant solid-state Li|PAN-LFP cell exhibits limited polarization and outstanding interfacial stability during long term cycling. That is, the Li|PAN-LFP cell presents a specific capacity of 160.8 mAh∙g⁻¹ at 0.1C, and 81% of the initial capacity is maintained after 500 cycles at 0.2C. The solid-state Li|PAN-LFP cell also exhibits excellent resilience in destructive tests such as cell bending and cutting.     

Facile Route to Constructing Ternary Nanoalloy Bifunctional Oxyegn Cathode for Metal-Air Batteries

Highly stable and efficient bifunctional air cathode catalyst is crucial to rechargeable metal-air batteries. Herein, a ternary nanoalloy layer composed of noble and base metal coated on a three-dimensional porous Ni sponge as the bifunctional cathode is synthesized through in-situ anchoring strategy, which can effectively keep the multi-metal nanoparticles from agglomeration and improve the density of active sites and catalytic activity. The prepared catalyst displays an excellent catalytic performance with lower overpotential and long-term stability. The Zn-air batteries with the as-prepared cathodes possess a large power density of 170 mW/cm², long cycling stability up to 230 cycles, and a high specific capacity of 771 mA·h/g. Furthermore, the corresponding Li-air batteries deliver a discharge capacity of 22429 mA·h/g. These superior properties of the metal-air batteries can be attributed to the combined influence of design and composition of electrode, which is of great significance to improve the electrochemical catalytic activity, providing great potential of wide application in expanded rechargeable energy systems.     

Recent progress in liquid electrolytes for lithium metal batteries

Li metal batteries are revived as the next-generation batteries beyond Li-ion batteries. The Li metal anode can be paired with intercalation-type cathodes LiMO₂ and conversion-type cathodes such as sulfur and oxygen. Then, energy densities of Li/LiMO₂ and Li/S,O₂ batteries can reach 400 Whkg^?1 and more than 500 Whkg^?1, respectively, which surpass that of the state-of-the-art LIB (280 Whkg^?1). However, replacing the intercalation-type graphite anode with the Li metal anode suffers from low coulombic efficiency during repeated Li plating/stripping processes, which leads to short cycle lifetime and potential safety problems. The key solution is to construct a stable and uniform solid electrolyte interphase with high Li⁺ transport and high elastic strength on the Li metal anode. This review summarizes recent progress in improving the solid electrolyte interphase by tailoring liquid electrolytes, a classical but the most convenient and cost-effective strategy.     

果胶粘结剂在锂硫电池中的应用研究

锂硫电池由于其超高理论能量密度(2567 Wh·kg^?1),较低的成本,以及环境友好性,被视为下一代储能设备的有力竞争者之一.鉴于粘结剂在稳定硫正极结构和抑制多硫化物穿梭方面可发挥重要作用,发展高性能硫正极粘结剂是改善锂硫电池性能的有效途径之一.本文研究了以果胶作为锂硫电池正极粘结剂的可行性.研究表明,采用果胶作为粘结剂的锂硫电池在电化学循环测试中首次放电比容量可达1210.6 mAh·g^?1,并且在200次循环后仍有837.4 mAh·g^?1的放电比容量,明显优于羧甲基纤维素钠-丁苯橡胶复合粘结剂的电池性能.经研究证实果胶粘结剂性能优良的原因在于其可以有效确保多壁碳纳米管/硫复合正极的结构稳定性并抑制多硫化物的穿梭.     

Suppressing Universal Cathode Crossover in High-Energy Lithium Metal Batteries via a Versatile Interlayer Design**

The universal cathode crossover such as chemical and oxygen has been significantly overlooked in lithium metal batteries using high-energy cathodes which leads to severe capacity degradation and raises serious safety concerns. Herein, a versatile and thin (≈25 μm) interlayer composed of multifunctional active sites was developed to simultaneously regulate the Li deposition process and suppress the cathode crossover. The as-induced dual-gradient solid-electrolyte interphase combined with abundant lithiophilic sites enable stable Li stripping/plating process even under high current density of 10 mA cm⁻². Moreover, X-ray photoelectron spectroscopy and synchrotron X-ray experiments revealed that N-rich framework and CoZn dual active sites can effectively mitigate the undesired cathode crossover, hence significantly minimizing Li corrosion. Therefore, assembled lithium metal cells using various high-energy cathode materials including LiNi_0.7Mn_0.2Co_0.1O₂, Li_1.2Co_0.1Mn_0.55Ni_0.15O₂, and sulfur demonstrate significantly improved cycling stability with high cathode loading.     

Highly Rechargeable Lithium-CO2 Batteries with a Boron- and Nitrogen-Codoped Holey-Graphene Cathode

Metal-air batteries, especially Li-air batteries, have attracted significant research attention in the past decade. However, the electrochemical reactions between CO₂ (0.04 % in ambient air) with Li anode may lead to the irreversible formation of insulating Li₂CO₃, making the battery less rechargeable. To make the Li-CO₂ batteries usable under ambient conditions, it is critical to develop highly efficient catalysts for the CO₂ reduction and evolution reactions and investigate the electrochemical behavior of Li-CO₂ batteries. Here, we demonstrate a rechargeable Li-CO₂ battery with a high reversibility by using B,N-codoped holey graphene as a highly efficient catalyst for CO₂ reduction and evolution reactions. Benefiting from the unique porous holey nanostructure and high catalytic activity of the cathode, the as-prepared Li-CO₂ batteries exhibit high reversibility, low polarization, excellent rate performance, and superior long-term cycling stability over 200 cycles at a high current density of 1.0 A g⁻¹. Our results open up new possibilities for the development of long-term Li-air batteries reusable under ambient conditions, and the utilization and storage of CO₂.     

EC modified PEO/PVDF-LLZO composite electrolytes for solid state lithium metal batteries

The polymer-ceramic composite electrolytes have great application potential for next-generation solid state lithium batteries, as they have the merits to eliminate the problem of liquid organic electrolytes and enhancing chemical/electrochemical stability. However, polymer-ceramic composite electrolytes show poor ionic conductivity, which greatly hinders their practical applications. In this work, the addition of plasticizer ethylene carbonate (EC) into polymer-ceramic composite electrolyte for lithium batteries effectively promotes the ionic conductivity. A high ionic conductivity can be attained by adding 40 wt% EC to the polyethylene oxide (PEO)/polyvinylidene fluoride (PVDF)-Li₇La₃Zr₂O₁₂ (LLZO) based polymer-ceramic composite electrolytes, which is 2.64 × 10⁻⁴ S cm⁻¹ (tested at room temperature). Furthermore, the cell assembled with lithium metal anode, this composite electrolyte, and LiFePO₄ cathode can work more than 80 cycles at room temperature (tested at 0.2 C). The battery delivers a high reversible specific capacity after 89 cycles, which is 119 mAh g⁻¹.