Generation Lithium-ion Batteries Research Articles

The Role of Cathode Surfaces in Lithium-Ion Battery Direct Recycling

Over the past decade the need for new sources of LIB raw materials has become apparent as the market for EVs and other consumer electronics that utilize lithium-ion batteries (LIB) has grown immensely. One emerging source of these needed materials is from the recycling of previous generation LIB cells and devices. Presently, this area is dominated by pyroprocessing and hydroprocessing. As delivered to the manufacturer these processes deliver simple salts or precursors that allow the recovered metals to be re-inserted into the LIB cathode synthesis process at a similar stage to newly mined materials. However, by reducing the end of life cathodes completely to either a metal or simple salt much of the previous investment in cathode creation has been eliminated. Direct processing is a method under development that maintains the integrity of the cathode lattice but seeks to repair the damage done by years of electrochemical cycling and restore the cathode to a near-pristine state. In this talk we will be discussing our work understanding the steps necessary to restore the recovered end of life cathode, assessing the damage done during cycling, and review various methods postulated to achieve this goal. Specific areas discussed will include methods of relithiation, role of surface damage, and role of precursors chosen.

Accelerating amorphous polymer electrolyte screening by learning to reduce errors in molecular dynamics simulated properties

Polymer electrolytes are promising candidates for the next generation lithium-ion battery technology. Large scale screening of polymer electrolytes is hindered by the significant cost of molecular dynamics (MD) simulation in amorphous systems: the amorphous structure of polymers requires multiple, repeated sampling to reduce noise and the slow relaxation requires long simulation time for convergence. Here, we accelerate the screening with a multi-task graph neural network that learns from a large amount of noisy, unconverged, short MD data and a small number of converged, long MD data. We achieve accurate predictions of 4 different converged properties and screen a space of 6247 polymers that is orders of magnitude larger than previous computational studies. Further, we extract several design principles for polymer electrolytes and provide an open dataset for the community. Our approach could be applicable to a broad class of material discovery problems that involve the simulation of complex, amorphous materials.

Exploiting the Iron Difluoride Electrochemistry by Constructing Hierarchical Electron Pathways and Cathode Electrolyte Interface.

Conversion-type cathodes such as metal fluorides, especially FeF2 and FeF3 , are potential candidates to replace intercalation cathodes for the next generation of lithium ion batteries. However, the application of iron fluorides is impeded by their poor electronic conductivity, iron/fluorine dissolution, and unstable cathode electrolyte interfaces (CEIs). A facile route to fabricate a mechanical strong electrode with hierarchical electron pathways for FeF2 nanoparticles is reported here. The FeF2 /Li cell demonstrates remarkable cycle performances with a capacity of 300 mAh g-1 after a record long 4500 cycles at 1C. Meanwhile, a record stable high area capacity of over 6 mAh cm-2 is achieved. Furthermore, ultra-high rate capabilities at 20C and 6C for electrodes with low and high mass loading, respectively, are attained. Advanced electron microscopy reveals the formation of stable CEIs. The results demonstrate that the construction of viable electronic connections and favorable CEIs are the key to boost the electrochemical performances of FeF2 cathode.

Covalent organic framework with active C=O/C=N groups for high performance cathode material for lithium‐ion batteries

The large-scale applications of energy storage system via lithium-ion batteries (LIBs) put forward demands for high capacity, high safety, and low cost of materials. Covalent organic polymers have attracted extensive attention because of their high capacity, flexible structural design, high safety, abundance, and low cost. Here, 2,3,5,6-tetraamino-p-benzoquinone and hexaketocyclohexane octahydrate were chosen as monomers to construct the covalent organic framework (TH-COF) cathode materials with active C=O and C=N groups. The TH-COF was further composed with reduced graphene oxide (rGO) and the prepared TH-COF/rGO cathode provided a capacity of 135 mAh g−1 after 600 cycles at 1 C current density. In addition, after 100 cycles, the cathode delivered capacities of 118 and 73 mAh g−1 at the high current densities of 5 C and 20 C, respectively, displaying superior rate performances. The TH-COF/rGO electrode exhibited high capacity and stability, making it a promising cathode material for the next generation LIBs.

Reinforced structural stability of Li-rich Mn-based cathodes by constructing multifunctional heterostructure using Nb-based MXenes

Lithium rich manganese based materials (LMR) have promised the likeliestcandidate for next generation lithium-ion battery cathodes owing to its high energy density and low materials cost. However, severe capacity decline and voltage decay hinder their practical application, which is closely concerned with the structure degradation and irreversible oxygen release. Herein, a simple strategy to reinforce the structural stability of LMR materials by constructing heterostructure with Nb-based MXenes (Nb2CTx/Nb4C3Tx) is proposed. A small amount of spinel phase and pseudo-bonding between Nb and O ions as well as extra oxygen vacancies can be induced by the MXenes addition in LMR, effectively inactivating the surface oxygen and suppressing the structure distortion. In addition, MXene can also alleviate the volume change during cycling process and provide additional transport channels for electrons. The ably designed 3 wt% LMR/Nb2CTx cathode presented high initial Coulombic efficiency of 85.6% at 0.1C (vs. 77.4% for the pristine material) and excellent cycling performance with a capacity retention of 83.8% after 200 cycles at 0.5C (vs. 66.6% for the pristine material). This work sheds some light on stabilizing the structure of lithium-rich manganese materials and provides a new idea for the design of other high performance cathode materials.

Preparation of silicon oxycarbide (SiOC) anodes for high performance Li-ion batteries using competitive relationship between crosslinking and polymerization

SiOC anode is considered as a candidate for the next generation of lithium ion batteries, because of its appealing specific capacity and relative small volume expansion. However, the inherent inferior electron conductivity blocks its development. Recently, controlling the amount of free carbon domains is adopted to modify the performance, ignoring the influence of free C on the SiOC phases change and their synergistic effect on the performance. The crosslinking and polymerization competition between divinylbenzene and polymethylsilsesquioxane was coordinated to regulate the free carbon and phase composition of SiOC ceramics, and a durable SiOC anode with high ceramic yield was prepared. The result is that, keeping the proportion of free C about 10% and increasing the SiO3C and SiO2C2 phases ratios can obtain good anode within limited cycle life (440 cycle in this work), and increasing free C amount further is necessary for durable long cycle life. Herein, S-DVB-2 anode with 12% free C delivers 698.7 mAh g−1 at a current density of 100 mA g−1 after 100 cycles, and S-DVB-1 anode with 20.6% free C shows excellent stable long cycle performance at the current density of 0.5 A g−1, the remaining capacity is 476 mAh g−1 after 500 cycles.

Difluorophosphoric Acid Generation and Crossover Reactions in LiNixCoyMnzO2 Cathodes Operating at High Voltage

Cycling lithiated metal oxides to high potential (>4.5 V vs Li) is of significant interest for the next generation of lithium ion batteries as this significantly increases the capacity and energy of cells. However, cells cycled to high potential suffer from rapid capacity fade due to a combination of thickening of the anode solid electrolyte interphase (SEI) and impedance growth on the cathode. While transition metal catalysed degradation of the anode SEI has been widely proposed as a primary source of capacity loss, a related acid induced degradation of the anode SEI is proposed. A systematic investigation of LiNi0.5Co0.2Mn0.3O2, and LiNi0.8Co0.1Mn0.1O2 cathodes cycled to 4.2 and 4.6 V has been conducted and the oxidative generation of the strong acid difluorophosphoric acid (F2PO2H) has been quantified by solution Nuclear Magnetic Resonance (NMR) spectroscopy. Ex-situ surface analysis of the electrodes with X-ray Photo Electron spectroscopy (XPS) suggests that the generation of F2PO2H correlates with a thickening of the anode SEI and an increase in the fluorophosphate content of the SEI. Changes to the LiNi0.8Co0.1Mn0.1O2 surface for cells cycled to 4.6 V are also consistent with the generation of acidic species. There is good correlation between the concentration F2PO2H, anode SEI degradation and the capacity loss of the cells.

Oligomeric Poly(Oxazoline) as Potential Lithium Battery Electrolytes

Polymer electrolytes are a promising and inherently material for next generation lithium batteries. The advancement in this field requires the use of new synthetic and fabrication techniques, as well as the investigation of new polymers. Here we report on the development of oligomeric Poly(2-ethyl-2-oxazoline) as a candidate for lithium batteries. By reducing the degree of polymerisation, the glass transition temperature was reduced from 54 °C for commercially available 50,000 Da PEtOx to 9.45 °C for lab synthesized 890 Da PEtOx. Doping with high concentrations of the lithium salts lithium nitrate, Lithium bis(trifluoromethanesulfonyl)imide and lithium perchlorate, we demonstrate a glass transition temperature maximum as the polymer electrolyte moves into the polymer-in-salt regime. In this regime we recorded a maximum conductivity of was 3.3 x 10−3 S cm−1 at 100 °C and 67 mol % LiClO4. This study demonstrates the potential for further use of alkyl oxazolines at high lithium salt concentrations and elevated temperatures.

Numerical Study on Thermal Management of Air-Cooling Model for Diamond, Triangular and Rectangular Lithium-Ion Batteries of Electric Vehicles

To improve the safety of electric vehicles, this paper analyzes the way of cooling lithium-ion batteries of electric vehicles and proposes an air-cooling scheme. First, a heat-generation model for the lithium-ion battery is prepared for numerical simulation and a finned air-cooling model is designed, which combines cold air with fins to lower the temperature of lithium-ion batteries. Through feasibility analysis, it is proved that the heat-generation model can reflect the actual heat generation of lithium-ion batteries. The cooling effect of the finned air-cooling model is also evaluated. The temperature can be 23.6 °C lower than the maximum compared with lithium-ion batteries without cooling. The cooling effect is desirable for diamond, triangle and rectangular lithium-ion battery packs, among which the rectangular battery pack achieves the most desirable effect. To conclude, to ensure the safe operation of lithium-ion batteries in electric vehicles, air cooling can be used to control their temperature, with the cooling effect in the rectangular lithium-ion battery pack being the most desirable.

An interconnected and scalable hollow Si-C nanospheres/graphite composite for high-performance lithium-ion batteries

Silicon (Si) anode is the most promising alternative for next generation lithium-ion batteries (LIBs) owing to large theoretical capacity, low working voltage and abundant natural resources. However, tremendous volume change of Si during the (de)lithiation processes causes repetitive formation of solid electrolyte interphase (SEI) layers, loss of electrical contact and electrodes pulverization, limiting its commercial application. Herein, we fabricate an interconnected hollow Si-C nanospheres/graphite composite via a facile and scalable approach. Notably, hollow Si-C nanospheres and graphite are homogeneously combined by using the surfactants as surface modifiers of graphite and introducing carbon dioxide (CO2) into magnesiothermic reduction reaction, resulting in the enhanced compatibility between hollow Si-C nanospheres and graphite, and the well-established electrical conductive network. The resultant Si-C nanospheres/graphite composite anode with carbon content of 59 wt% delivers a large reversible specific capacity of 662 mAh g−1 and a high capacity retention of 65.7% at 0.5 A g−1 after 200 cycles. Such excellent rate performance and superior cycling performance are attributed to high electrical conductivity and buffering effect of graphite, superior compatibility between hollow Si-C spheres and graphite, uniform distribution of both Si-C nanospheres with a unique hollow architecture and graphite flakes inside the composites and well-established interconnected electrical conductive carbon networks, which can effectively alleviate Si volume expansion and maintain good electrical contact during cycling. This strategy provides insights into designing Si-based anodes for practical LIBs.

Insight into Reversible Conversion Reactions in SnO2 -Based Anodes for Lithium Storage: A Review.

Various anode materials have been widely studied to pursue higher performance for next generation lithium ion batteries (LIBs). Metal oxides hold the promise for high energy density of LIBs through conversion reactions. Among these, tin dioxide (SnO2 ) has been typically investigated after the reversible lithium storage of tin-based oxides isreported by Idota and co-workers in 1997. Numerous in/ex situ studies suggest that SnO2 stores Li+ through a conversion reaction and an alloying reaction. The difficulty of reversible conversion between Li2 O and SnO2 is a great obstacle limiting the utilization of SnO2 with high theoretical capacity of 1494mA h g-1 . Thus, enhancing the reversibility of the conversion reaction has become the research emphasis in recent years. Here, taking SnO2 as a typical representative, the recent progress is summarized and insight into the reverse conversion reaction is elaborated. Promoting Li2 O decomposition and maintaining high Sn/Li2 O interface density are two effective approaches, which also provide implications for designing other metal oxide anodes. In addition, some in/ex situ characterizations focusing on the conversion reaction are emphatically introduced. This review, from the viewpoint of material design and advanced characterizations, aims to provide a comprehensive understanding and shed light on the development of reversible metal oxide electrodes.

Nerve network-inspired solid polymer electrolytes (NN-SPE) for fast and single-ion lithium conduction

The low lithium-ion conductivity is current the bottleneck in developing solid-state electrolytes (SSEs) that are expected to be a key component in the next generation of lithium batteries. Inspired by the high connectivity of the biological nerve network, we designed a mimic architecture inside a polymer electrolyte to provide fast lithium-ion pathways. Detailed experimental and simulation studies revealed that the mimic nerve network could efficiently form the bi-continuous structure at very low percolation threshold, and rendered an unprecedentedly non-linear increment by order of magnitudes in the lithium-ion conductivity, with a superior lithium-ion conductivity up to 0.12 mS·cm−1, transference number up to 0.974 and robust mechanical strength of 10.3 MPa. When applied in lithium metal batteries, good rate and cycling performance were achieved at both room and elevated temperatures.

Biomass-Based Silicon and Carbon for Lithium-Ion Battery Anodes.

Lithium-ion batteries (LIBs) are the most preferred energy storage devices today for many high-performance applications. Recently, concerns about global warming and climate change have increased the need and requirements for LIBs used in electric vehicles, and thus more advanced technologies and materials are urgently needed. Among the anode materials under development, silicon (Si) has been considered the most promising anode candidate for the next generation LIBs to replace the widely used graphite. Si cannot be used as such as the electrode of LIB, and thus, carbon is commonly used to realize the applicability of Si in LIBs. Typically, this means forming a-Si/carbon composite (Si/C). One of the main challenges in the industrial development of high-performance LIBs is to exploit low-cost, environmentally benign, sustainable, and renewable chemicals and materials. In this regard, bio-based Si and carbon are favorable to address the challenge assuming that the performance of the LIB anode is not compromised. The present review paper focuses on the development of Si and carbon anodes derived from various types of biogenic sources, particularly from plant-derived biomass resources. An overview of the biomass precursors, process/extraction methods for producing Si and carbon, the critical physicochemical properties influencing the lithium storage in LIBs, and how they affect the electrochemical performance are highlighted. The review paper also discusses the current research challenges and prospects of biomass-derived materials in developing advanced battery materials.

Alleviating expansion-induced mechanical degradation in lithium-ion battery silicon anodes via morphological design

The mechanics of films undergoing volume expansion on curved substrates plays a key role in a variety of technologies including biomedical implants, thermal and environmental barrier coatings, and electrochemical energy storage systems. Silicon anodes for lithium-ion batteries are an especially challenging case because they can undergo volume variations up to 300% that results in cracking, delamination, and thus significant loss in performance. In this study, we use finite element analysis to model the volume expansion during lithiation for silicon coated on spinodal, inverse opal, gyroid, and Schwartz primitive nickel backbones and compare the distributions of maximum principal stress, strain energy density, and von Mises stress, which we use as indicators for propensity for cracking, delamination, and yielding, in order to explore the effect of backbone morphology on mechanical degradation during expansion. We show that, when compared to the inverse opal, the spinodal morphology reduces and uniformly distributes the maximum principal stress and strain energy density in the silicon layer, and delays the onset of expansion-induced yielding at all silicon layer thicknesses, which we ascribe to the unique interfacial curvature distribution of spinodal structures. This work highlights the importance of morphology on coatings undergoing volume variations and unveils the particular promise of spinodally derived materials for the design of next generation lithium-ion battery electrodes.

An overview of the application of atomic layer deposition process for lithium‐ion based batteries

Lithium-ion battery (LIB) systems provide a very promising range of power supply systems for diverse applications like electric vehicles, hybrid plug-in electric vehicles, grid storage systems, and microelectronics. Nevertheless, the features of lithium-ion batteries (LIBs), which include energy density and power, cycle lifetime, safety, as well as cost, must be enhanced in order to achieve all these feasible applications. Atomic layer deposition (ALD), as a result of its unique benefits above other thin-film methods of deposition, emerges as a very useful approach for use in improving the efficiency of LIBs. This review summarizes ALD's advanced successes in designing new nanostructured solid-state electrolytes and electrode materials, as well as the adjustment of the interfaces of electrodes and electrolytes through the application of surface coatings for the avoidance of undesirable side reactions to attain maximum adequate performance of the electrode. Also covered are ideas for the potential advancement of ALD studies and technology for the applications of LIBs. This review paper is anticipated to furnish researchers within the LIB and ALD fields with valuable information that would encourage much more extensive research on the use of ALD to produce new generation LIBs.

Engineering Bamboo Leaves Into 3D Macroporous Si@C Composites for Stable Lithium-Ion Battery Anodes.

Silicon is considered as the most promising candidate for anodes of next generation lithium-ion batteries owing to its natural abundance and low Li-uptake potential. Building a macroporous structure would alleviate the volume variation and particle fracture of silicon anodes during cycling. However, the common approaches to fabricate macroporous silicon are complex, costly, and high energy-consuming. Herein, bamboo leaves are used as a sustainable and abundant resource to produce macroporous silicon via a scalable magnesiothermic reduction method. The obtained silicon inherits the natural interconnected network from the BLs and the mesopores from the BL-derived silica are engineered into macropores by selective etching after magnesiothermic reduction. These unique structural advantages lead to superior electrochemical performance with efficient electron/ion transport and cycling stability. The macroporous Si@C composite anodes deliver a high capacity of 1,247.7 mAh g−1 after 500 cycles at a current density of 1.0 A g−1 with a remarkable capacity retention of 98.8% and average Coulombic efficiency as high as 99.52% for the same cycle period. Furthermore, the rate capabilities of the Si@C composites are enhanced by conformal carbon coating, which enables the anode to deliver a capacity of 538.2 mAh g−1 at a high current density of 4.0 A g−1 after 1,000 deep cycles. Morphology characterization verifies the structural integrity of the macroporous Si@C composite anodes. This work demonstrated herein provides a simple, economical, and scalable route for the industrial production of macroporous Si anode materials utilizing BLs as a sustainable source for high-performance LIBs.

Enabling Non-Carbonate Electrolytes for Silicon Anode Batteries Using Fluoroethylene Carbonate

Silicon is considered as one of the most promising anodes for next generation lithium-ion batteries, due to its high theoretical capacity and energy density. However, many technical barriers remain to its implementation, due to its high chemical/electrochemical reactivities with standard electrolytes and incomplete passivation. Here we take the most effective passivating additive of fluoroethylene carbonate (FEC) and study its impact on non-carbonate electrolytes. Our results indicate that esters and ureas-based electrolytes are similarly stabilized by FEC, and have very similar capacity retentions and Coulombic efficiencies to the state-of-the-art carbonate electrolyte. This study indicates the discovery of more efficient additives other than FEC is vital in developing an electrolyte that can successfully enable a silicon-anode battery.

Modification Strategy for Constructing Li Gradient Combined with Spinel Phase Coating on Li-Rich Mn-Based Materials

Li-rich layered oxides (LLOs) are considered as the cathode materials for the next generation of lithium-ion batteries because of their high specific capacity. However, due to the structural rearrangement in the charging and discharging process, the initial Coulombic efficiency (ICE) is low and accompanied by serious voltage attenuation and bad cycle performance. In this work, the Li-gradient layer on the surface of the rod-like LLOs is constructed by the treatment of (NH4)2SiF6 under high temperature and subsequent washing. XRD, HRTEM, and Raman spectra verify the existence of the spinel phase of Li1–xMn2O4 on the surface of LLOs by the modification. The results of electrochemical measurements show that the modified LLOs exhibit a higher ICE of 87% with an excellent cycling retention of 90.4% (after 100 cycles at 1 C). These improvements on the electrochemical performance are caused by the high Li+ diffusion and improved the redox reversibility of oxygen ions on the LLOs with the unique structure of the Li-gradient and spinel coating layer on the surface.

Conjugated Tetrathiafulvalene Carboxylates for Stable Organic Lithium Batteries

AbstractOrganic electrode materials are potential energy storage materials for the next generation lithium batteries. Herein, carboxylate groups are installed to a conjugated tetrathiafulvalene (TTF) platform to yield two compounds, namely lithium tetrathiafulvalene‐dicarboxylate (TTF‐Li2) and lithium tetrathiafulvalene‐tetracarboxylate (TTF‐Li4), as stable anode materials for lithium batteries. The low solubility in the electrolyte, brought about by the carboxylate groups, and high rechargeability ensured by the conjugated TTF platform lead to excellent battery performance. After cycling at a current density of 0.5 C for 120 cycles, a net specific capacity of 108.19 mAh g−1 and 217.55 mAh g−1 is obtained for the TTF‐Li2 and TTF‐Li4 anodes containing 70 wt.% of active materials, corresponding to 61.4 % and 82.0 % of their theoretical capacities, respectively. The density functional theory (DFT) calculation confirms the well‐delocalized charge for both TTF‐Li2 and TTF‐Li4. Therefore, the TTF‐Li2 and TTF‐Li4 are promising anode materials for lithium batteries.

Stabilization of crystal and interfacial structure of Ni-rich cathode material by vanadium-doping

Stable structure and interface of nickel-rich metal oxides is crucial for practical application of next generation lithium-ion batteries with high energy density. Bulk doping is the promising strategy to improve the structural and interfacial stability of the materials. Herein, we report the impact of vanadium-doping on the structure and electrochemical performance of LiNi0.88Co0.09Al0.03O2 (NCA88). Vanadium doped in high oxidation state (+5) would lead to alteration of the crystal lattice and Li+/Ni2+ cation mixing. Those are the main factors determining the cycling and rate capability of the materials. With optimization of vanadium-doping, the preservation of the integrity of the secondary particles of the materials, the enhancement of the diffusion of Li+ ions, and alleviation of the side reactions of the electrolyte can be efficiently achieved. As a result, NCA88 doped with vanadium of 1.5 mol % can provide superior cycling stability with capacity retention of 84.3% after 250 cycles at 2C, and rate capability with capacity retention of 65.5% at 10C, as compared to the corresponding values of 58.6% and 55% for the pristine counterpart, respectively. The results might be helpful to the selection of dopants in the design of the nickel-rich materials.