High-safety Lithium-ion Batteries Research Articles

Bilayer Heterostructure Electrolytes Were Prepared by a UV-Curing Process for High Temperature Lithium-Ion Batteries

Solid-state electrolytes are widely anticipated to revitalize high-energy-density and high-safety lithium-ion batteries. However, low ionic conductivity and high interfacial resistance at room temperature pose challenges for their practical application. In this work, the dual-matrix concept is applied to the design of a bilayer heterogeneous structure. The electrolyte in contact with the cathode blends PVDF-HFP and oxidation-resistant PAN. In contrast, the electrolyte in contact with the anode blends PVDF-HFP and reduction-resistant PEO. A UV-curing process was used to fabricate the bilayer heterostructure electrolyte. The heterostructure electrolyte exhibits an ionic conductivity of 4.27 × 10−4 S/cm and a Li+ transference number of 0.68 at room temperature. Additionally, when assembled into LiFePO4/CPEs/Li batteries, it shows a high initial discharge capacity at room temperature (168 mAh g−1 at 0.1 C and 60 mAh g−1 at 2 C), with a capacity retention of 93.3% after 100 cycles at a current density of 0.2 C. Notably, at 60 °C, the battery maintains a discharge capacity of 90 mAh g−1 at 2 C, with a capacity retention of 97.4% after 100 cycles at 0.2 C. Therefore, solid-state batteries using this bilayer heterogeneous structure electrolyte demonstrate promising performance, including effective capacity output and cycling stability.

Reversible Li plating regulation on graphite anode through a barium sulfate nanofibers-based dielectric separator for fast charging and high-safety lithium-ion battery

Poor Li plating reversibility and high thermal runaway risks are key challenges for fast charging lithium-ion batteries with graphite anodes. Herein, a dielectric and fire-resistant separator based on hybrid nanofibers of barium sulfate (BS) and bacterial cellulose (BC) is developed to synchronously enhance the battery’s fast charging and thermal-safety performances. The regulation mechanism of the dielectric BS/BC separator in enhancing the Li+ ion transport and Li plating reversibility is revealed. (1) The Max-Wagner polarization electric field of the dielectric BS/BC separator can accelerate the desolvation of solvated Li+ ions, enhancing their transport kinetics. (2) Moreover, due to the charge balancing effect, the dielectric BS/BC separator homogenizes the electric field/Li+ ion flux at the graphite anode-separator interface, facilitating uniform Li plating and suppressing Li dendrite growth. Consequently, the fast-charge graphite anode with the BS/BC separator shows higher Coulombic efficiency (99.0% vs. 96.9%) and longer cycling lifespan (100 cycles vs. 59 cycles) than that with the polypropylene (PP) separator in the constant-lithiation cycling test at 2 mA cm−2. The high-loading LiFePO4 (15.5 mg cm−2)//graphite (7.5 mg cm−2) full cell with the BS/BC separator exhibits excellent fast charging performance, retaining 70% of its capacity after 500 cycles at a high rate of 2 C, which is significantly better than that of the cell with the PP separator (retaining only 27% of its capacity after 500 cycles). More importantly, the thermally stable BS/BC separator effectively elevates the critical temperature and reduces the heat release rate during thermal runaway, thereby significantly enhancing the battery’s safety.

Delithiation-accelerating and self-healing strategies realizes high-capacity and high-rate black phosphorus anode in wide temperature range

Black phosphorus (BP) anode with high capacity (2596 mAh g−1) and suitable lithiation potential (0.7 V vs. Li+/Li) is an ideal candidate for high-energy-density and high-safety lithium-ion batteries, however, the pratical implementation is greatly limited by its slow reaction kinetics and huge volume expansion. Here, inspired by nature, liquid metal (LM) is explored as a self-heal agent, which can well stabilize the BP anode through buffering the volumetric expansion and re-activating “dead P and LixP”. Moreover, LM also acts as a good catalyst, which can adjust Li ion concentration and reduce the activation energy of delithiation reaction, thus prolonging the cycling life. Therefore, the LM modified BP/graphite (G) composite delivers an excellent high-rate performance of 1123 mAh g−1 at 4 C with 80.0% capacity retention after 200 cycles, a superior wide-temperature performance of 1547.5 mAh g−1 and 569.0 mAh g−1 at 50 oC and −20 oC, respectively.

Electrolytes for High-Safety Lithium-Ion Batteries at Low Temperature: A Review.

As the core of modern energy technology, lithium-ion batteries (LIBs) have been widely integrated into many key areas, especially in the automotive industry, particularly represented by electric vehicles (EVs). The spread of LIBs has contributed to the sustainable development of societies, especially in the promotion of green transportation. However, the high demand for battery performance and safety in these fields has made the high viscosity, volatility, and potential leakage inherent in traditional organic liquid electrolytes a constraint on their further expansion. Especially at low temperature, the increased viscosity of the electrolyte, reduced solubility of lithium salts, crystallization or solidification of the electrolyte, increased resistance to charge transfer due to interfacial by-products, and short-circuiting due to the growth of anode lithium dendrites all affect the performance and safety of LIBs. Therefore, improving the safety performance of LIBs under low-temperature environments has become a focus of current research. This paper primarily reviews the progress made in utilizing different types of electrolytes in LIBs to enhance safety and optimize low temperature performance and discusses the current research progress as well as the future development direction of the field.

A high-safety lithium-ion battery electrospun separator with Si3N4-assisted sulfonated poly(ether ether ketone) for regulating lithium flux

The uncontrolled lithium (Li) dendrite growth significantly impacts the safety performance of polymer separators. To mitigate this growth, this study introduces Si3N4 into sulfonated poly(ether Ether Ketone) (SPEEK) and prepares Si3N4/SPEEK composite separators via electrospinning. At the interface between the Si3N4/SPEEK separator and the Li anode, the Si nanowires that form impede Li dendrite growth, thereby enhancing the electrochemical performance of lithium-ion batteries (LIBs). The Li deposition test of the 10 % Si3N4/SPEEK separator can operate for 1000 h without short-circuiting. Additionally, the LiFePO4||Li cell with the 10 % Si3N4/SPEEK separator shows improved initial discharge capacity (157.8 mAh g−1 at 1C) and superior rate performance (125 mAh g−1 at 10C). Moreover, the nano-scale Si3N4 endows the separator with robust thermal and mechanical properties. The FLIR observations reveal that the 10 % Si3N4/SPEEK separator maintains uniform thermal distribution and structural integrity even at 300 °C, ensuring safe battery operation at high temperatures. The additional load of the 10 % Si3N4/SPEEK separator can reach 10.2 mN, which enhances the puncture resistance of the separator. This work provides a solid approach for the application of SPEEK as a high-safety and high-rate LIB separator.

A lightweight carbon-incorporated polymer current collector for improving the performance and safety of lithium-ion batteries

The current collector plays a crucial role in transporting electrons and mechanical support of electrodes for lithium-ion batteries (LIBs). Commercial Cu and Al foil with high density deliver no capacity, so decreasing the weight of the metallic current collector is an effective method for enhancing the energy density of batteries. In this study, we prepared a carbon-incorporated polyimide (CIPI) current collector with a lightweight areal density of 1.41 mg cm−2 and voltage window of 0–5 V. CIPI can suppress the current collector corrosion and improve the long-term cycling performance of high-voltage cathode. Besides, CIPI decreases polarization resistance and relieves the volume expansion of SiOx particles, demonstrating a high capacity retention after 200 cycles. In nail penetration tests, the maximum temperature of the pouch battery with CIPI is only 46.73 % of the battery using Cu and Al foil. In addition, the mechanical flexibility makes CIPI suitable for flexible batteries, delivering ultra-stable voltage even when repeatedly folded in half. The CIPI opens a new pathway to develop high energy density and high safety LIBs and promotes the development of flexible and wearable storage devices.

Comprehensive crosslinking strategy using fluorinated azide to enhance the thermal stability of ceramic-coated separators for Li-ion batteries

Enhancing the thermal and mechanical stabilities of ceramic-coated separators (CCSs) is required for high-safety lithium-ion batteries (LIBs). As both the thickness and areal mass of ceramic coating layers (CCLs) have reduced, various strategies have been developed to overcome the limitations of conventional ceramics and polymeric binders. In this regard, we suggest a comprehensive photocrosslinking approach to form fully crosslinked CCLs using a new fluorinated azide binder that can readily react with aliphatic functional groups in any component of CCSs. When a small amount of azide binder is added to a CCL slurry consisting of Al2O3 particles and a poly(acrylic acid) (PAA) binder, short UV irradiation can lead to inter- and intramolecular crosslinking points within the polyethylene (PE) separator, between the PE separator and the PAA binder, and within the PAA binders in the CCL. Consequently, the thermal stability and the adhesive strength of crosslinked CCS (X-CCS) can be significantly improved compared to the control CCS without azide. Moreover, a LiNi0.6Co0.2Mn0.2O2/graphite cell with X-CCS exhibited a comparable cycle life to that of the PE separator and non-crosslinked CCS. Furthermore, because UV illuminators are easily added to conventional fabrication processes, this strategy is a simple but effective approach for advancing high-safety LIBs.

Flame-retardant separator coated with Boehmite ammonium polyphosphate composite for high-safety lithium-ion batteries

To enhance the thermal stability, electrochemical compatibility, and overshoot protection of separators, it is common practice to incorporate inorganic particles for separator modification. In this work, we discussed a polypropylene (PP) separator that was coated with a combination of hydrothermal boehmite (AlOOH) and ammonium polyphosphate (APP). The coating layer can greatly reduce the thermal shrinkage rate of the separator, enabling the modified separator to retain its original size at 180 °C. In addition, part of the material formed by the decomposition of the coating material at high temperatures can be well-diluted oxygen, thus reducing the risk of combustion. Furthermore, the presence of the coating layer increases the ionic conductivity and electrolyte wettability, thereby improving the cycle stability of the battery. This study utilizes inexpensive, lightweight, and eco-friendly materials to enhance a commercially available polypropylene separator. This modification not only increases the efficiency of material usage but also enhances the economic and environmental advantages of the improved separator.

A novel Al2O3/polyvinyl pyrrolidone-coated polyethylene separator for high-safety lithium-ion batteries

In this study, a novel ceramic-polyethylene (PE) composite separator is designed and achieved by a very facile preparation strategy for high-safety lithium-ion batteries (LIBs). The optimized ceramic slurry composed of Al2O3 and polyvinyl pyrrolidone (PVP) is coated on one side of PE separator in an economically efficient way to form the novel Al2O3/PVP-PE separator. It is found that the superior PVP binder can improve the adherence of heat-resistant Al2O3 ceramic powders on the PE substrate, which significantly enhances the thermal stability of the optimized separator. The Al2O3/PVP-PE separator shows negligible shrinkage at a high temperature of 180 °C after 30 min thermal treatment. In addition, the prepared Al2O3/PVP-PE separator shows excellent wettability with electrolyte, large porosity and high liquid storage capacity, which are quite beneficial to the ionic conductivity and charge storage kinetics. Furthermore, LIBs (LiFePO4/graphite) assembled with the optimized Al2O3/PVP-PE separator shows superior electrochemical performance than LIBs assembled with bare PE separator. This study provides insight into the practical application and commercialization of novel Al2O3/PVP-PE separator for high-safety LIBs with improved electrochemical performance.

An eco-friendly and flame-retardant bio-based fibers separator with fast lithium-ion transport towards high-safety lithium-ion batteries

As one of the most important parts in lithium-ion batteries (LIBs), commercial polyolefin separators suffer from inherent drawbacks such as thermal-dimensional shrinkage, poor electrolyte wettability, and environmental pollution. In this study, a green bio-based composite separator with good flame retardancy and high ion conductivity is designed by a facile paper-making process and subsequently borate salts crosslinking, which consists of marine-derived calcium alginate fibers bridge and land-derived cellulose micro-fibers filler. The composite separator reveals a multi-hierarchical porous structure and homogeneous boron crosslinking, and consequently has a superior liquid electrolyte wettability and high strength. Impressively, the composite separator delivers better flame retardancy and higher lithium-ion transference number (tLi+ = 0.4) and ion conductivity (σ = 1.53 mS cm−1) compared with the commercial polypropylene separator, attributing to the abundant polar groups upon the fibers and the incorporation of sp3 Boron. As a result, the LIBs equipped with composite separator demonstrate excellent interface stability and rate capability. More importantly, the LIBs exhibit greater security at the elevated temperature of 140 °C. Additionally, the composite separator shows a potential degradation in natural environments. This eco-friendly bio-based separator paves a new insight for the design of heat-resistance separator as well as the safe running of LIBs.

High-Safety Lithium-Ion Battery Separator with Adjustable Temperature Function Inspired by the Sugar Gourd Structure.

As the power core of an electric vehicle, the performance of lithium-ion batteries (LIBs) is directly related to the vehicle quality and driving range. However, the charge-discharge performance and cycling performance are affected by the temperature. Excessive temperature can cause internal short circuits and even lead to safety issues, such as thermal runaway. The separator plays a crucial role in protecting the battery from regular operation, preventing direct touch between the cathode and the anode while allowing the transport of lithium ions. In this study, we have designed a thermoregulating separator in the shape of calabash, which uses melamine-encapsulated paraffin phase change material (PCM) with a wide enthalpy (0-168.52 J g-1) to dissipate the heat generated inside the battery promptly. Under extra-long-use conditions, the heat emitted by the battery is absorbed by the PCM without causing a significant temperature rise that triggers thermal runaway. The PCM separator can effectively suppress the temperature increase caused by battery penetration. Due to the unique structure of the PCM, the battery is short-circuited; it can significantly delay the internal temperature rise of the battery and quickly dissipate the heat, which is consistent with the characteristics of natural calabash in nutrient absorption and water diffusion, improving the melting and heat storage efficiency of the PCM. The design of the phase change separator provides an effective reference for overheat protection and improved safety in lithium-ion batteries.

Evaluation of asymmetric poly(vinylidene fluoride)-coated polyimide separator with three-dimensionally homogeneous microporous structure for high-safety lithium-ion battery

Safety hazards associated with separators in lithium-ion batteries are more pronounced in light of the significant improvement of energy density of batteries, hindering their wide application. In this research, asymmetric poly (vinylidene fluoride) (PVDF)-coated polyimide separators with three-dimensionally homogeneous microporous (3DHM API/PVDF) structure are prepared, in which a PVDF layer with a thickness of 6 μm on one side of polyimide. Polyimide, as the base film, has a high heat-resistant temperature which ensures that as-prepared separators will not be shrunk and burned. The coated PVDF layer imparts 3DHM API/PVDF with thermal shutdown function at 175 °C due to the melting of PVDF. The temperature difference between the shutdown and meltdown temperature is over 100 °C, ensuring that the LIB assembled with 3DHM API/PVDF is safe for use. Moreover, the interconnected microporous structure of the separator facilitates the formation of 3D Li+ transport pathways and uniformity of lithium deposition, suppressing lithium dendrite growth. The coin cells assembled by 3DHM API/PVDF exhibit similar electrochemical performance to that of a commercial polypropylene separator at room temperature. Therefore, the novel 3DHM API/PVDF separator may be a promising candidate for a significantly safer LIB.

Composite polymer electrolyte facilitated by enhanced amorphousity and Li+ conduction using LaFeO3-embedded PVDF-HFP for solid-state lithium metal battery

Composite polymer electrolytes (CPEs) are a promising alternative to flammable conventional liquid electrolytes for high-safety lithium-ion batteries. Establishing low-cost filler that enhances the amorphous nature of polymer in the CPEs and exhibits efficient Lewis acid-base interaction between fillers and anions of lithium salt, leading to improved dissociation of salts for enhanced conduction, is indispensable. In this work, for the first time, we construct a solid composite polymer electrolyte of poly(vinylidene fluoride hexafluoropropylene) embedded LaFeO3 (LFO) particles prepared by solution casting and electrospinning methods and study their performances. The 5 wt% LFO filler embedded CPE made by means of solution casting and electrospinning methods exhibited the highest ionic conductivity of 5.9 × 10-4 and 1.49 × 10-3 S cm−1 at room temperature and electrochemical stability window up to 4.6 and 4.45 V, respectively. Further, as-assembled solid-state lithium-ion batteries using electrospun CPE showed an initial discharge capacity of 166 mAh/g at 0.1C-rate and solution-casted CPE showed excellent cycling stability with 98.6 % capacity retention at 0.3C-rate even at 50th cycle. Such excellent performance originated from the introduction of the LFO particles as filler into the polymer matrix to enhance the ionic conductivity, mechanical strength and lithium metal compatibility of the resulting CPEs.

Doping in Solvation Structure: Enabling Fluorinated Carbonate Electrolyte for High-Voltage and High-Safety Lithium-Ion Batteries

Doping in Solvation Structure: Enabling Fluorinated Carbonate Electrolyte for High-Voltage and High-Safety Lithium-Ion Batteries

Dual-modified LiNi0.8Co0.1Mn0.1O2 cathode materials with lithium conducting hybrid oligomer and single-walled carbon nanotube for improving electrochemical performance and thermal stability of lithium-ion batteries: A novel approach for high-power and high-safety applications

In this study, we investigated the synergetic effect of a novel lithium-ion conducting hybrid oligomer [N, N′-bismaleimide-4, 4′-diphenylmethane (BMI), lithiated trithiocyanuric acid (Li-TCA) and Jeffamine®-M1000 (JA®); Li-BTJ] coating layer on a nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material wrapped with highly electron-conductive single-walled carbon nanotubes (SWCNTs) to enhance electrochemical performance and thermal stability for high-power and high-safety lithium-ion batteries (LIBs). Morphological analyses using scanning electron microscopy/energy dispersive spectroscopy and transmission electron microscopy showed that the NCM811 active material surface was uniformly coated with a hybrid oligomer to form NCM811@Li-BTJ, which was subsequently wrapped with SWCNTs (NCM@Li-BTJ/SWCNT composite cathode). CR2032 coin-type cells with optimized NCM811@1 wt% Li-BTJ/0.2 wt% SWCNT composite electrodes delivered a significantly enhanced capacity retention (CR) of 90.1 % relative to that of bare NCM811 electrodes (CR: 82.1 %) at 1C for 200 cycles from 2.8 to 4.3 V (vs. Li/Li+). Electrochemical impedance spectroscopy and cyclic voltammetry revealed that this superior cycling performance resulted from a lower charge transfer resistance (Rct: 96.2 vs. 324.3 Ω) and a lower polarization voltage (∆V: 0.243 vs. 0.411 V vs. Li/Li+). The in-situ micro-calorimetric results presented the total heat generation (Qt) values of the coin cells with the delithiated NCM811@Li-BTJ and NCM@Li-BTJ/SWCNT electrodes at 5C and 35 °C were substantially lower by ~9.3 % and ~ 14.6 %, respectively, compared to the bare NCM811 counterpart, indicating that the surface modifications on the NCM811 active materials could prevent the LIBs' thermal instability. Furthermore, X-ray photoelectron spectroscopy studies revealed that the Li-BTJ hybrid oligomer coating layer effectively suppressed the formation of residual Li side products such as Li2CO3 evidently on the surface of the NCM811 active material particles, thereby inhibiting undesirable side reactions. Post-mortem analyses of the dual-modified NCM811 electrode after cycling revealed that the microstructure and particle morphology of the NCM composite cathode material were extensively maintained through the synergistic effects of the Li-BTJ ion-conductive and SWCNTs electron-conductive agents.

Critical Review on High-Safety Lithium-Ion Batteries Modified by Self-Terminated Oligomers with Hyperbranched Architectures

In recent years, the evolution of lithium-ion batteries (LIB) has been propelled by the growing demand for energy storage systems that are lightweight, have high energy density, and are long-lasting. This review article examines the use of self-terminated oligomers with hyperbranched architecture (STOBA) as a key electrode additive for the superior performance of LIBs. STOBA has been found to have excellent electrochemical properties, including high specific capacity, low impedance, and good cycling stability when used as an additive in electrode materials. The article discusses the process of synthesis and characterization of STOBA materials, including their potential applications in LIBs as electrode material additives. The article also discusses current research on the optimization of STOBA materials for LIBs, including the use of different solvents, monomers, and initiators. Overall, the review concludes that STOBA materials possess huge potential as a next-generation additive for LIB safety.

Tackling application limitations of high-safety γ-butyrolactone electrolytes: Exploring mechanisms and proposing solutions

Developing wide-temperature and high-safety lithium-ion batteries (LIBs) presents significant challenges attributed to the absence of suitable solvents possessing broad liquid range and non-flammability properties. γ-Butyrolactone (GBL) has emerged as a promising solvent; however, its incompatibility with graphite anode has hindered its application. This limitation necessitates a comprehensive investigation into the underlying mechanisms and potential solutions. In this study, we achieve a molecular-level understanding of the perplexing interphase formation process by employing in-situ spectroelectrochemical techniques and density function calculations. Our findings reveal that, even at high salt concentrations, GBL consistently occupies the primary Li+ solvation sheath, leading to extensive GBL decomposition and the formation of a high-impedance and inorganic-poor solid-electrolyte interphase (SEI) layer. Contrary to manipulating solvation structures, our research demonstrates that the utilization of film-forming additives with higher reduction potential facilitates the pre-establishment of a robust SEI film on the graphite anode. This approach effectively inhibits GBL decomposition and significantly enhances the battery's lifespan. This study provides the first reported intrinsic understanding of the unique GBL-graphite incompatibility and offers valuable insights for the development of wide-temperature and high-safety LIBs.

Cellulose-based mesoporous membrane co-engineered with MOF for high-safety lithium-ion batteries

At present, the commercial polyolefin membranes for lithium-ion battery (LIBs) usually have poor thermal stability, poor wettability and high cost. Herein, we developed a sustainable mesoporous membrane with good anionic grabbing effect based on the biomass cellulose co-engineered with the metal–organic frameworks (MOFs). The abundant oxygen-containing functional groups in cellulose can enhance the affinity of the membrane with the electrolyte. And the coordination of the metal ions in MOFs with the functional groups in cellulose not only prevents the aggregation of the cellulose to form uniform porous structure, but also enhances the mechanical strength of the membrane. More importantly, the MOFs has appropriate mesopore size and strong cationic site, which can crab the PF6- anions in the electrolyte, thus promoting the fast transfer of Li+, thereby inhibiting the growth of lithium dendrite. In summary, this work put forward a simple and efficient strategy for designing the membrane with fast Li+ transfer, high safety and thermal stability and for LIBs.

Niobium-Based Oxide for Anode Materials for Lithium-Ion Batteries.

Recently, it has become imperative to develop high energy density as well as high safety lithium-ion batteries (LIBS) to meet the growing energy demand. Among the anode materials used in LIBs, the currently used commercial graphite has low capacity and is a safety hazard due to the formation of lithium dendrites during the reaction. Among the transition metal oxide (TMO) anode materials, TMO based on the intercalation reaction mechanism has a more stable structure and is less prone to volume expansion than TMO based on the conversion reaction mechanism, especially the niobium-based oxide in it has attracted much attention. Niobium-based oxides have a high operating potential to inhibit the formation of lithium dendrites and lithium deposits to ensure safety, and have stable and fast lithium ion transport channels with excellent multiplicative performance. This review summarizes the recent developments of niobium-based oxides as anode materials for lithium-ion batteries, discusses the special structure and electrochemical reaction mechanism of the materials, the synthesis methods and morphology of nanostructures, deficiencies and improvement strategies, and looks into the future developments and challenges of niobium-based oxide anode materials.

Nano-alumina@cellulose-coated separators with the reinforced-concrete-like structure for high-safety lithium-ion batteries

Nano-alumina@cellulose-coated separators with the reinforced-concrete-like structure for high-safety lithium-ion batteries