-60 ℃ normal work of the battery does not smell? Ultra-low temperature battery Li-CO2

Unprotonated Li-CO2 batteries due to their high energy density (1876 WhKg ^-1 ), and coupled to the CO2 fixation and effective double feature of advanced energy storage, caused great concern in the field of energy storage. In addition, since the cathode material is CO2 in the air, Li-CO2 batteries in the aerospace exploration technology exhibit unique advantage. For example, the concentration of CO2 in the atmosphere of Mars up to 96%, is the future of Li-CO2 batteries the most promising applications. To promote the practical application of battery Li-CO2, in recent years, researchers have developed various catalytic cathode, quasi-solid electrolyte and solid electrolyte additive, and the design of new flexible electrode, Li-CO2 to increase battery energy / power density, cycling performance and mechanical flexibility. While the art has made initial progress, existing research working cell Li-CO2 environment focused at room temperature to a high temperature 150 ℃. Mars is a very cold planet, with an average temperature of about minus sixty degrees, currently reported battery Li-CO2 does not work in extreme cold environments. It is well known, to reduce the ambient temperature will lead to lower the conductivity of the electrolyte, the electrode reaction kinetics slow, the electrode / electrolyte interface is deteriorated, and therefore requires more energy to drive the charging and discharging process, thereby increasing the discharge / charge over the course of the potential to shorten the cycle life. Worse, since the electrolyte completely solidified, the battery will not work at extremely low temperatures (e.g., -60 ℃). So far, no studies on low temperature (below zero) Li-CO2 batteries, not to mention ultra-low temperature battery of Li-CO2. To address these challenges Department

Introduction

the results of , Macromolecular Science, Fudan University, Professor Peng Huisheng and [ 123] Prof. Wangbing Jie designed and assembled, a Li-CO2 Swagelok-type battery. The battery using metal lithium as the anode material, containing the 1,3-dioxolan LiTFSI (DOL) is an electrolyte, a gas diffusion layer coated with iridium catalyst as the cathode, and a commercially available Parafilm protective layer as the cathode. Thanks to the very low DOL yl freezing point of the electrolyte at low temperatures, from highProton conductivity and excellent electrochemical stability, and iridium cathodic reduction of CO2 (CO2RR) high catalytic activity and CO2 precipitation reactor (CO2ER) of the prepared Li-CO2 battery can work efficiently at ultra-low temperature environment . at a current density of 100 mAg cryogenic temperatures – 1 ^{and -60 ℃, the battery shows 8976 mAg} -1 ^{and a high capacity deep discharge cycles 150 (1500 h ) ultra-high cycle life, and a fixed volume of each cycle was 500 mAg} -1 ^{. Thus excellent electrochemical properties at a low temperature to suppress side reactions formed on generating discharge products and an electrolyte and a lithium anode labile small size (FIG. 1) due to the cathode. Related outcomes to \”Li-CO2Batteries Efficiently Working at Ultra-Low Temperatures\” the title in 2020 May 15, published in the} Advanced Functional Materials .

Principle FIG 1. Li-CO2 cell operating at ultra-low temperature environment, and forming a schematic view of the discharge products and discharge decomposition (left) and the charge (right) process. Li-CO2 working mechanism based on the electrochemical reaction of the battery 4Li + 3CO2 + 4e- ⇋2Li2CO3 + C (E = 2.80 V vs Li + / Li).

Detailed graphics

First, the Li-CO2 cryogenic cell design

cryogenic cell design relates generally to material selection and optimization system / or cell structure. First, should the use of high conductivity electrolyte, to ensure its efficient ion transmission at low temperatures and a good electrolyte / electrode interface. DOL cyclic ether is a small molecule, having a low freezing point of -95 deg.] C, a low viscosity solvent and solvated lithium ions good characteristics can be low, and a large capacity, can ensure high cycle efficiency of the lithium anode. Accordingly, ultra-low temperature became Li-CO2 battery electrolyte an ideal candidate. Ordinary electrical tetraglyme groupSolution quality (about -40 deg.] C) compared to the freezing point of the electrolyte DOL group even below -100 deg.] C, and has a higher ion conductivity can be maintained at -80 ℃ 2.26 mS cm

-1 ^{the high electrical conductivity. Further, due to the enhanced stability of the electrolyte, DOL may be introduced into the electrolyte effective to produce inhibition of side reactions. Oxidative stability of the electrolyte is increased with decreasing temperature, 4.34 V. stable at the time of its voltage range from 3.05 V at 0 ℃ increased to -30 ° C 3.53 V and -60 ° C Thus, DOL electrolyte solvent is an ideal low battery Li-CO2. Since iridium has high catalytic activity and CO2RR CO2ER, and has been used to improve the Li-CO2 electrochemical performance of the battery. Thus researchers chose coated with iridium is used as the cathode GDL battery Li-CO2, and the first to explore the performance of the energy storage device at low temperature. Further, taking into account the battery Li-CO2 is a semi open system, through which the electrolyte which will inevitably porous cathodes were evaporated. Thus, researchers using a commercially available material may be used as the permeable Parafilm Li-CO2 gas cathodic protection layer to suppress volatilization of the electrolyte, and further extend the life of battery Li-CO2.} Second, the low temperature performance of Li-CO2 electrochemical cell

First, the researchers explored the effect of temperature on the electrochemical properties of Li-CO2 batteries. In the cut-off voltage of 2.0 V, current density of 100 mAg

-1 ^{conditions, deep battery discharge capacity of Li-CO2 up to 14 720 mAhg} -1 ^{at 0 deg.] C, or even at -60 ℃ can reach 8976 mAhg} -1 ^{(Figure 2a). Further, even at a current density of from -60 ℃ 50 mAg} -1 ^{increased to 500 mAg} -1 ^{, Li-CO2 apparent battery voltage does not drop, showing its further good low temperature flexibility and high rate capability. Cyclic voltammetry indicated that the oxidation stability of the electrolyte is increased with decreasing temperature, which makes it capable of withstanding DOL charge polarization-based electrolyte at ultra-low temperature -60 ℃.}

Electrochemical Performance of FIG 2. Li-CO2 cell operating at ultra-low temperature environment.Subsequently, researchers Li-CO2 long-term cycle stability of the battery at low temperature 0, -30 and -60 ℃ (FIG. 2b-d), the test conditions: cut-off capacity of 500 mAhg

-1 ^{, a current density of 100 mAg} -1 ^.

at 0 ℃, Li-CO2 battery capacity of the first cycle showed moderate potential difference of 0.85 V, was increased to 1.35 V in the first 30 cycles, and ultimately fail at 40 cycles. Surprisingly, although inevitably there will be the first cycle gap expansion phenomenon of polarization, but with decreasing battery Li-CO2 ambient temperature but exhibit enhanced cycling stability.

When the working temperature dropped to -30 deg.] C, the battery 69 can be stably charging and discharging cycles, even its service life can be extended to 150 cycles at -60 ℃ (1500 h). In addition, the study found that the iridium catalyst is introduced, such that the polarization is significantly reduced clearance, a significant increase in the number of cycles.

Under the condition of -60 ℃, Li-CO2 cell cathode coated with iridium may be up to 150 cycles, while the coatings without the iridium Li-CO2 cell cycle after the ring 23 failed.

The above results show that iridium-based cathode Li-CO2 batteries at ultra-low temperature can be used as primary or secondary battery stability, which is so far the first can have a high capacity and good cyclability at such ultra low temperature aprotic Li-CO2 battery.

Third, at low Li-CO

2 Analysis of the product discharge cell Generally, the product form of the discharge cycle life of a metal gas cell aprotic and composition are closely related. To explore why the Li-CO2 batteries with enhanced cycle performance at low temperatures, researchers discharge battery cycle product was analyzed. Non-situ XRD and FTIR showed that the discharge products of lithium battery (of Li2CO3) and the charging completely decomposed at the cathode. This indicates that the battery Li-CO2 produced having good reversibility at ultra-low temperature of -60 ℃. Further, the charging process in the ultra-low temperature environmentDifferential in situ electrochemical mass spectrometry confirmed the co-oxidation reaction mainly occurs Li2CO3 and C and mild self-decomposition reaction of Li2CO3 charging phase: 2Li2CO3 + C → 4Li ++ 3CO2 + 4e- and 2Li2CO3 → 4Li ++ 2CO2 + O

2- ^{+ 3e-. Characterization SEM showed that the product will form a discharge vary significantly with temperature. After an initial discharge at 0 ℃, the cathode cycle is 100-300 nm in size covering sheet (FIG. 3c). As the temperature is further reduced to -30 and -60 ℃, gradually evolved into a product having a diameter of 50-70 nm (Figure 3d) and 30-50 nm (FIG. 3e) of the spherical particles. Particulate and flaky product showed formation of the product may follow the discharge solution growth mechanism, rather than a surface mediated pathway. SEM image further shows, after the initial charge at different temperatures, the particulate discharge products have been completely decomposed and removed from the cathode (FIG. 3f-h). However, after 10 cycles of charging after discharge cycle, there are some undecomposed product remains on the surface of the cathode at 0 deg.] C, and at -30 and -60 deg.] C, the product discharge completely decomposed. This shows that the structure and morphology of the discharge products and greatly affects the reversibility of Li-CO2 battery life.}

3. Li-CO2 topography battery discharge products at ultra-low temperature environment and characterization of cyclic reversibility.Thus, according to the researchers morphological difference between the discharge products at different temperatures, the reasons explained (FIG. 3j) Li-CO2 cycle characteristics of the battery at low temperature are improved. At low temperatures of -60 ° C, nucleation occurs more readily than the product in the case at 0 ° C. And at -60 ° C, the growth process is slowed down discharge product, resulting in a particulate product less loosely gathered on the cathode, at 0 ° C and the discharge end of the larger product particles deposited on the electrode on. Further, since the electron tunneling distance limitations, the insulating oxidation product is typically carried out from solution into solid phase region inside the insulator. And oxidation due to the increased bit interface, such that a small-sized product particles are more easily decomposed during charging. Batteries and Li-CO2 \”death\” and the accumulation of undecomposed product insulating the cathode about the loopThis will cause clogging and passivated porous cathode. Thus, the size of discharge products formed in smaller and a low temperature easily decomposed, and can be completely decomposed after charging, which greatly improves the performance of the battery and cycle reversibility.

Fourth, the stability at low temperature battery Li-CO2

In addition to the important reasons undecomposed discharge products accumulated on the cathode, adverse side effects are also produced during cycle gas metal premature battery failure. To verify this, researchers use a new sheet reactivate lithium Li-CO2 failed battery, and electrolyte and after the fresh cycles and cycles of the lithium anode were carried out before and after the ex situ XRD analysis and 1H NMR characterization. NMR spectrum displayed (FIG. 4a-c), there is no clear evidence that the electrolyte recollected adverse reactions occurred at -30 and -60 ° C, and after ten cycles under a serious 0 ℃ electrolyte secondary reactions, including the decomposition of the molecule and DOL ring-opening polymerization. These results indicate that low ambient temperatures can be effectively suppressed some of the electrolyte associated with adverse DOL. Similarly, X-ray diffraction pattern, after ten cycles at 0 ° C, the surface of the lithium anode appeared adverse hydrated lithium (LiOH) by-products, which may be due to the reaction of the lithium anode and the moisture or the electrolyte due. In contrast, in the Li anode -30 and -60 ° C cycles LiOH no detectable signal (FIG. 4d-e), demonstrated at lower temperatures, some of the adverse side effects on the Li anode is suppressed . Further, in addition to improving the stability of the electrolyte, the lower temperatures reduce the water content in the battery may help to improve the cyclability of battery Li-CO2. Indeed, even when used in the initial cell assembly completely dry the material, due to degradation and the electrolyte into the water environment, long-term operation is still difficult to completely remove moisture from the battery, which inevitably caused no the necessary side reaction, thereby shortening the battery life. However, due to the reduction of water does not even exist, and enhance the stability of electrolytes, these moisture-related side effects at extremely low temperatures may be inhibited. In general, the lower the operating temperature effective to inhibit cell Li-CO2 harmful side reactions, which is another important factor to improve the low-temperature cycle performance.

FIG. 4. Li-COAnalysis of battery electrolyte and a lithium anode circulation of stability at different temperatures.

Fifth, the low temperature Li-CO

to apply a presentation 2 battery taking into account the Li-CO2 batteries are most likely to find important applications on Mars, researchers ultra-low temperature battery Li-CO2 was proof of concept. As shown in FIG. 5a, Li-CO2 in a cell using ultra-low temperature environment and CO2 stabilize the output voltage, i.e., ultra-low temperature -70 ° C. (Dry ice implementation) power supply LED on the model for astronauts. FIG. 5b-c have confirmed Li-CO2 cells can be used in a low-temperature environment for an electronic power supply apparatus. Further, according to the actual Mars temperature fluctuations over a period of time and changes in ambient temperature, the battery can still operate in a stable, almost no change in the voltage (FIG. 5d).

Figure 5. cryogenic battery Li-CO2 presentation application.

Summary

In summary, the work for the first time realized efficient ultra-low temperature Li-CO2 battery, not only can be stably operated at -60 ℃ ultra-low temperature environment, and with up to 8976 mAg

-1 ^{the depth of the high-capacity, long service life of 150 cycles (1,500 hours) and the fixed capacity of each circle 500 mAhg} -1 ^{. Studies have shown that enhance the cycle stability at ultra-low temperatures is mainly due to the small size and easy to suppress the cathode discharge decomposition products are formed and the low temperature of the electrolyte and the anode side reaction produced. This work provides a common and effective paradigm for the development of high-performance metal gas cell operating at extremely low temperatures. References:… Li-CO2 Batteries Efficiently Working at Ultra-Low Temperatures Adv Funct Mater 2020, 2001619. DOI:. 10.1002 / adfm.202001619 description link: https: //onlinelibrary.wiley.com/doi/10.1002/adfm .202001619}