Angewandte Chemie International Edition: Solid interhalogenated compounds with effective Br0 fixation for stable high-energy zinc batteries
Although a large number of researchers are committed to the exploration of Br-based batteries, highly soluble Br2/Br3- substances cause severe "shuttle effects" that lead to severe self-discharge and low coulomb efficiency. Traditionally, quaternary ammonium salts such as methylethylmorpholine bromide (MEMBr) and tetrapropylammonium bromide (TPABr) can be used to immobilize Br2 and Br3-, but they occupy the mass and volume of the battery without capacity contribution.
Here, Professor Chunyi Chi's team from City University of Hong Kong reports a fully active solid interhalogenated compound IBr as a cathode to address the above challenges. The oxidized Br0 is fixed by iodine (I), and the cross-diffused Br2/Br3- substance is completely eliminated during the entire charging process and discharge. The Zn|| IBr batteries offer an extremely high energy density of 385.8 Wh×kg-1, significantly higher than the I2, MEMBr3 and TPABr3 cathodes. This work provides a new way to realize the active solid halogen interchemistry of high-energy electrochemical energy storage devices.
Figure 1. The mechanism of action of the IBr cathode
Specifically, active iodine (I) was used to immobilize Br on the solid interhalogen of IBr, where the halogen intercoordination chemically fixed Br0 and did not produce cross-diffusion of Br2/Br3- during the entire charge-discharge process. The results show that the IBr cathode has a high output voltage of 1.65 V and a high specific volume of 267.3 mAh g-1 and its energy density is as high as 385.8 Wh kg-1, which is significantly higher than the I2 cathode, MEMBr3 cathode and TPABr3 cathode. Meanwhile, Zn|| IBr batteries can run more than 6000 times and retain 82.7% of their initial capacity due to IBr's stable interhalogen fixation and stable adhesion to macroporous carbon.
In addition, the team developed a ~750 mAh Zn|| with a high IBr load (~13.0 mg cm-2). IBr pouch batteries have excellent cycle stability, maintaining 85.9% of their initial capacity after 250 cycles of over 98.0% CE. This work successfully achieves high energy density redox-enhanced halogen intercoordination in aqueous batteries based on low-cost and tangible active I and Br non-metallic halogens.
Figure 2. Electrochemical performance of IBr pouch cells and Ah-class high-capacity pouch cells (4-layer 6×8 cm2).
Solid Interhalogen Compounds with Effective Br0 Fixing for Stable High-energy Zinc Batteries, Angewandte Chemie International Edition 2023 DOI: 10.1002/anie.202301467
2. Angewandte Chemie International Edition: Molecular engineering of carbonate electrolyte solvation structures for durable sodium metal batteries at -40°C
Carbonate electrolytes have excellent chemical stability and high salt solubility, making them ideal for achieving high energy density at room temperature in sodium-metal batteries. However, the adverse effects of instability and difficulty in desolvation of solid electrolyte interfacial phase (SEI) formed by electrolyte decomposition at ultra-low temperature (-40°C) limit its large-scale development.
Here, Professor Yan Yu's team from the University of Science and Technology of China designed a novel low-temperature carbonate electrolyte for ultra-low temperature (-40°C) sodium metal batteries through molecular engineering of solvated structures. That is, 1M bis(fluorosulfonyl)imide sodium (NaFSI) in EC/PC/diethyl carbonate (DEC) (1:1:4, v/v) novel carbonate electrolyte system. In addition, vinyl sulfate (ES) additives are used to adjust the solvation structure. And this electrolyte can achieve accelerated charge transfer kinetics and obtain stable SEI at -40 °C.
Figure 1. Solvation structure and design principle of electrolyte
Through the calculation of the energy level of the front-line molecular orbital, the reduction stability of each electrolyte component and the role of additives in the construction of SEI films were evaluated. Since ES has the lowest unaccounted molecular orbital energy (LUMO, -0.14 eV), extraneous electrons are more likely to occupy their lower electron orbitals, resulting in easier reduction at higher voltages and participating in the formation of SEI membranes.
ES contributes to the formation of SEIs rich in Na3N, Na2S, and Na2SO3 with high ionic conductivity and mechanical strength (~7.0GPa). In Na|| In a Na-symmetrical battery system, it can maintain a low polarization voltage at -40 °C for more than 1500 hours. In Na|| In the NVP full battery system, the initial discharge capacity reaches 84 mAh g-1 at -40 °C, and after 200 cycles, the corresponding capacity retention rate is 88.2%. Therefore, this work provides a new attempt to achieve high energy density batteries by changing the solvation structure of carbonate electrolytes at ultra-low temperatures.
Figure 2. Na|| using CSE, BLTE and ES6-BLTE electrolytes Electrochemical performance of NVP full battery
Molecular Engineering on Solvation Structure of Carbonate Electrolyte toward Durable Sodium Metal Battery at -40 ℃，Angewandte Chemie International Edition 2023 DOI: 10.1002/anie.202301169
3. Advanced Functional Materials: Dynamic ion sieve as a buffer layer to regulate the Li+ flow in lithium metal batteries
The solid electrolyte interface layer (SEI) plays an important role in protecting the lithium anode and inhibiting the growth of lithium dendrites. However, it is not enough to inhibit lithium dendrite growth by protecting SEI, which mainly affects the negative electrode aspect. Equally important, regulating the flow of Li+ in the electrolyte can also promote uniform lithium deposition. Therefore, how to achieve the uniform flow of Li+ is one of the key factors to achieve uniform deposition of lithium metal batteries (LMB).
Here, Professor Ma Jianmin's team from Hunan University proposed a dynamic ion sieve concept to adjust the spatial arrangement of Li+ by introducing tributylmethylphosphine bis(trifluoromethanesulfonyl)imide (TMPB) into the carbonate electrolyte and designing a buffer layer near the surface of the lithium anode. The buffer layer induced by TMP+ can adjust the speed of the arriving solvated Li+, so that the solvated Li+ has enough time to redistribute and accumulate on the surface of the lithium anode, so that the flow of Li+ is uniform and more concentrated.
In addition, TFSI− can participate in the generation of inorganic-rich solid electrolyte interfaces (SEIs) and Li3N, which can promote the Li+ conductivity of SEIs. Thus, stable and uniform lithium deposits can be obtained.
Figure 1. Theoretical analysis
This work successfully proposed the concept of Li+ sieve as a buffer layer to change the interface between the negative electrode and the electrolyte for the protection of the lithium anode. In detail, TMP+ with high LUMO energy has a lower reduction tendency, so it can wander at the interface as a dynamic ion sieve and participate in the spatial arrangement of ions. When Li is deposited, TMP+ can act as a buffer layer to regulate the spatial distribution of Li+. In addition, electrostatic action can adjust the transmission speed of Li+, so Li+ can be redistributed and aggregated on the negative electrode surface to obtain a more uniform and higher concentration of Li+ flow.
At the same time, Li+ coordinates with more anions, which can bring them to the negative surface and participate in the generation of SEI. More PF6− and TFSI− anions induce stable and conductive SEI, and more LiF and Li3N inorganic components. Under the synergistic effect of both sides of the interface, Li+ can be uniformly deposited on the surface of the Li anode and at a Li|||0.5 mA cm−2 Li symmetrical cells cycle stably for up to 1000 hours. In addition, Li|| The NCM622 full battery also exhibits excellent cycling performance, maintaining high capacity over 300 cycles. Therefore, this work provides a new interface model for understanding and protecting the interface of lithium anodes.
Figure 2. Li|| in different electrolytes Electrochemical performance of Li-symmetric batteries
Dynamic Ion Sieve as the Buffer Layer for Regulating Li+ Flow in Lithium Metal Batteries，Advanced Functional Materials 2023 DOI: 10.1002/adfm.202213811
4. Journal of the American Chemical Society: Hybrid conductors based on metal-organic frameworks (MOFs) realize highly stable light-assisted solid-state lithium-oxygen batteries
The demand for high energy density and continuously rechargeable batteries is further driving the development of lithium-oxygen (Li-O2) batteries. However, the safety concerns of liquid electrolytes and the slow kinetics of oxygen reduction (ORR) and oxygen evolution (OER) at the positive electrode have seriously hindered the commercial application of lithium-oxygen batteries.
Here, Professor Xu Jijing's team from Jilin University reported the use of metal-organic framework hybrid ion/electronic conductors as both solid electrolytes (SSEs) and cathode materials in light-assisted solid-state lithium-oxygen batteries. It is found that mixed ion/electron conductors can effectively capture UV-visible light and generate a large number of photoelectrons and holes, which are beneficial to participate in electrochemical reactions and greatly improve the reaction kinetics of solid lithium-oxygen.
In addition, the conductivity of metal-organic frameworks has been studied and mixed ion/electron conductors have excellent Li+ conductivity (1.52×10−4 S cm−1 at 25°C) and superior chemical/electrochemical stability (especially for H2O, O2−) when used as solid electrolytes.
Figure 1. Electrochemical properties and theoretical calculations of MIL-125-Li and NH2-MIL-125-Li
Aiming at the reversibility of solid-state lithium-oxygen batteries, Raman mapping and various structural characterization techniques were also used to study the morphology and composition changes of electrodes before and after charging and discharging. The results show that NH2-MIL-125-Li has excellent reversibility under illumination. Due to the synergistic effect of photoelectrons and lithium ions in NH2-MIL-125-Li, light-assisted solid-state lithium-oxygen batteries can be stably cycled up to 320 times. For light-assisted liquid lithium-oxygen batteries, the side reactions caused by electrolyte decomposition gradually accumulate, and the polarization of the battery gradually increases after 150 cycles.
Therefore, light-assisted solid-state lithium-oxygen batteries based on MOF hybrid conductors provide excellent cycling performance and high round-trip efficiency. That is, the introduction of light greatly reduces the high reaction energy barrier during the charging process of traditional solid-state batteries, thereby reducing the charging potential of the battery and improving the energy conversion efficiency and cycle life of the battery. In conclusion, this work creates a MOF hybrid conductor with excellent electron/ion conductivity and electrochemical stability, and deeply explores the electron-ion transport mechanism in MOF. In addition, the light-assisted solid-state lithium-air battery with high safety and long life exhibits a high energy efficiency of 94.2% and a long cycle life of 320 cycles. This work is clearly innovative in key material design and battery integration, providing new ideas for the development of the next generation of high-performance solid-state battery technology.
Figure 2. Electrochemical performance of solid-state lithium-oxygen batteries
Metal–Organic Framework-Based Mixed Conductors Achieve Highly Stable Photo-assisted Solid-State Lithium–Oxygen Batteries，Journal of the American Chemical Society 2023 DOI: 10.1021/jacs.2c11839
5. Angewandte Chemie International Edition: Low-cost, high-strength cellulose benchmark solid-state polymer electrolyte for solid-state lithium-metal batteries
Polymer electrolytes have high safety, high energy density, high temperature resistance, good processing performance, non-flammable and explosive characteristics, so they have received extensive attention from academia and industry. However, due to the low ionic conductivity of the polymer electrolyte at room temperature (<10-3 S cm-1) and the poor interfacial properties with the electrode, it has not been applied in practice. Quasi-solid polymer electrolytes can effectively overcome the problem of poor contact with the electrode. However, quasi-solid polymer electrolytes have various problems, such as solvent residue and insufficient mechanical properties, which limit its further development. So far, most polymer matrices used for quasi-solid composite electrolytes, such as poly(vinylidene fluoride-co-hexafluoropropene), polyacrylonitrile and polyethylene oxide, have been unable to meet the needs of long battery cycles and inhibition of lithium dendrites due to insufficient Li+ migration and mechanical property limitations.
Here, the team of Professor Tian Lei of Shenzhen University prepared a quasi-solid composite polymer electrolyte using cellulose acetate as raw material by direct thermal formation, which solved the problems of low ionic conductivity and incompatibility between the polymer electrolyte and the electrode. The acetate ester (CH3COO-) on cellulose acetate breaks the large hydrogen bond interaction between cellulose chains and provides a high-speed Li+ transport channel. The Li+ transfer of the composite electrolyte (C-CLA-10 QPE) formed by binding to the NASICON-type inorganic electrolyte (Li1.3Al0.3Ti1.7(PO4)3, LATP) is 0.85, which is higher than most polymer electrolytes.
Figure 1. Electrochemical performance of solid-state batteries based on C-CLA-10 QPE
In addition, the authors also used Gaussian theoretical simulations to further study the interaction between Li+ and CLA and the interaction between CLA, and found that Li+ can form a variety of interactions with the abundant oxygen-containing functional groups in the CLA matrix during transport. This includes work with -OH and -CH3COO- and with -OH, -CH3COO- and -O-. DFT simulations show that when Li+ is coordinated with -OH and -CH3COO-, the resulting dissociation energy is low, indicating that the channels formed by -OH and -CH3COO- have less hindrance to Li+ degrees of freedom, providing a pathway for rapid transportation of Li+.
In conclusion, the experimental results and DFT simulation results show that the CLA matrix has high interface stability and provides a high-speed and stable Li+ transmission channel. Prepared LFP| C-CLA-1 QPE| Li cells exhibit superior cycle stability after 1200 cycles at 1C and 25°C, with a capacity retention rate of up to 97.7%. Therefore, the study proposes an inexpensive and high-performance solid-state electrolyte material that provides an important solution for the future manufacturing of long-lived and economical solid-state batteries.
Figure 2. Mechanism of action
Low-Cost, High-Strength Cellulose-based Quasi-Solid Polymer Electrolyte for Solid-State Lithium-Metal Batteries, Angewandte Chemie International Edition 2023 DOI: 10.1002/anie.202302767
6. Journal of the American Chemical Society: Topological directional transformation of surface structure realizes the direct regeneration of the cathode of waste lithium-ion batteries
The recycling of used lithium-ion batteries has become a top priority to solve the problem of resource shortage and potential environmental pollution. However, direct recovery of the discarded LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode is challenging because the strong electrostatic repulsion of the transition metal octahedral in the lithium layer provided by the rock salt/spinel phase formed on the surface of the cyclic cathode severely interferes with the transport of Li+, thereby inhibiting the replenishment of lithium during the regeneration process, resulting in poor regeneration cathode capacity and cycling performance.
Here, Academician Cheng Huiming of the Shenzhen Advanced Research Institute of the Chinese Academy of Sciences, Professor Zhou Guangmin of Shenzhen International Graduate School of Tsinghua University and Professor Liang Zheng of Shanghai Jiao Tong University proposed a topological phase transition strategy using ammonium hydroxide pretreatment of SNCM523 to realize the phase transition of rock salt/spinel phase to Ni0.5Co0.2Mn0.3(OH)2 layered hydroxide on the surface of SNCM523, and then obtain the regenerated NCM523 cathode material. Compared with non-topological orientation transformation (host substance changes with Li content), topological orientation transformation helps to form better Li+ transport channels, minimize kinetic complexity, and improve the transport efficiency of Li+ in SNCM523 regeneration. There is no unconverted rock salt/spinel phase on the surface of the regenerated cathode, which improves cycling performance.
More importantly, the regeneration of industrially produced waste NCM523 blackbody (SNCM523-BM), waste LiCoO2 (SLCO), and waste LiNi0.6Co0.2Mn0.2O2 (SNCM622) materials is realized through topological orientation.
Figure 1. Schematic diagram of the topological transformation method and structural characterization of the regenerative SNCM523
In conclusion, this work proposes a topological transformation of stable rock salt/spinel facies to Ni0.5Co0.2Mn0.3(OH)2, which then returns to the NCM523 cathode. The result is that Li+ is more easily transported in the channel (from one octahedral position to another octahedral body position, via a tetrahedral intermediate) and electrostatic repulsion is weakened, resulting in topological resulfurization with a low migration barrier, which greatly improves lithium supplementation during regeneration.
In addition, the proposed method can be extended to repair waste NCM523 black matter, waste LiNi0.6Co0.2Mn0.2O2 and waste LiCoO2 cathode, and its electrochemical performance after regeneration is comparable to that of commercial original cathode. This work demonstrates the rapid topological revulcanization process in the regeneration process by modifying the Li+ transmission channel, which provides a unique perspective for the regeneration of waste LIB cathodes.
Figure 2. Electrochemical performance of SNCM523, RSNCM523 and RHSNCM523
Topotactic Transformation of Surface Structure Enabling Direct Regeneration of Spent Lithium-Ion Battery Cathodes, Journal of the American Chemical Society 2023 DOI: 10.1021/jacs.2c13151
7. Advanced Energy Materials: for 4.6 V Li|| Amide function of LiCoO2 battery, electrode-electrolyte interface rich in Li3N/LiF heterostructure
Increasing the charge cut-off voltage of LiCoO2 to 4.6V can improve battery density. However, structural instability is a key challenge (e.g., electrolyte decomposition, Co dissolution, and structural phase transitions).
Here, Professor Ma Jianmin's team from Hunan University constructed a stable electrode electrolyte interface (EEI) with high Li+ conductivity provided by polar amide groups and Li3N/LiF heterostructures. Among them, 3-(trifluoromethyl)phenyl isocyanate (3-TPIC) is reasonably designed as an electrolyte additive for maintaining 4.6V Li|| with this CEI LiCoO2 batteries, which can effectively solve the challenge of structural instability. Polar amide groups can desolvate Li+ and increase Li+ transport. The Li3N/LiF heterostructure in the cathode electrolyte interface (CEI) can accelerate the insertion/extraction of Li+ to improve coulomb efficiency and weaken the polarization of LiCoO2 at 4.6 V.
In addition, a solid electrolyte interface (SEI) with a similar structure on the surface of the Li anode facilitates uniform Li deposition to inhibit Li dendrite growth. Therefore, 4.6V Li|| with excellent EEI LiCoO2 batteries can provide excellent electrochemical performance.
Figure 1. Simulation of MD with blank and electrolyte containing 3-TPIC
In conclusion, this work proposes amide-functional, Li3N/LiF-rich heterostructured EEIs, which stabilize the transport of LiCoO2 at 4.6V by inhibiting the dissolution of Co ions and by inhibiting the growth of Li dendrites. This EEIs conferred by 3-PIC greatly improves the 4.6V Li|| Electrochemical performance of LiCoO2 batteries. The polar amide group can promote the desolvation of Li+ and increase the transport of Li+. In addition, the Li3N/LiF heterostructure can speed up the transport of Li+. Under the synergistic effect of polar amide groups and Li3N/LiF heterostructures, stable CEI can prevent the structural phase transition of LiCoO2 and maintain its structural stability during cycling.
Similarly, stable SEI can inhibit the growth of lithium dendrites and maintain the stability of lithium anodes. Therefore, this work provides an important reference for improving the cycle stability of lithium cobalt oxide at high voltage through EEI with good function of additive design.
Figure 2. Li|| in blank and electrolytes containing additives Electrochemical performance of Li-symmetric batteries
Amide-Functional, Li3N/LiF-Rich Heterostructured Electrode Electrolyte Interphases for 4.6 V Li|| LiCoO2 Batteries, Advanced Energy Materials 2023 DOI: 10.1002/aenm.202300084
8. Advanced Functional Materials: Grafted MXenes-based polymer electrolyte for 5V solid-state batteries
Polymer-blended solid polymer electrolytes (SPEs) combine the benefits of multiple polymers for greater safety in applications such as LiCoMnO4 (LCMO) in 5V cathodes. However, the presence of defects and severe macroscopic phase separation of voids in the polymer blend limits the electrochemical stability and ion mobility of SPE.
Here, Professor Chunyi Zhi and Associate Professor Jun Fan of City University of Hong Kong developed MXene (MXene-g-PAN), an inorganic compatibilizer polyacrylonitrile, to improve the compatibility of polyvinylidene fluoride-hexafluoropropylene (PVHF)/PAN blends and inhibit the solidification of phase particles. The resulting SPE exhibits high negative stability, with an ionic conductivity of 2.17×10-4S cm-1, enabling stable and reversible Li deposition/peeling (over 2500 hours). The prepared solid-state Li‖LCMO battery can provide a discharge voltage of 5.1V and has good capacity (131 mAh g-1) and cycle performance.
In addition, the authors also constructed solid-state integrated graphite ‖ LCMO batteries to expand the application of MXene-based SPE in flexible batteries. Benefiting from the interfaceless design, the battery achieves excellent mechanical flexibility and stability, withstands various deformations, and has a low capacity loss (<≈10%).
Figure 1. Electrochemical performance of half-cell batteries
In conclusion, based on the PVHF and PAN mixture, with MXene-g-PAN as the compatibilizer, SPE with a wide electrochemical stability window and high ion conductivity was developed to improve its phase stability and ion mobility at the phase interface. Solid-state Li|||based on the designed SPE LCMO batteries and integrated solid graphite|| LCMO batteries that provide discharge voltages in excess of 5V and significant capacity. In addition, the integrated structure makes solid-state lithium-ion batteries have stronger deformation ability, can withstand bending (100,000 times), twisting (10,000 times), rolling (5,000 times) and folding (200 times), and there is almost no capacity loss.
Therefore, the combination of a rationally designed SPE with an optimized phase structure and an integrated structure makes the manufacture of flexible solid-state lithium-ion batteries with excellent performance simple. This research marks a significant development in solid-state flexible lithium-ion batteries that can improve their performance, stability, and reliability by studying the miscibility of polymer mixtures, which facilitates the design of high-performance SPEs.
Figure 2. One-piece graphite|| Electrochemical performance of LCMO batteries
Grafted MXenes Based Electrolytes for 5V-Class Solid-State Batteries, Advanced Functional Materials 2023 DOI: 10.1002/adfm.202214539