Featured Materials for High Safety Lithium Batteries -Lithium - Ion Battery Equipment
In the context of "carbon peaking" and "carbon neutrality", accelerating the electrification of powertrains has become an inevitable trend in the development of new energy vehicles. As the key technology of new energy vehicle power system, lithium battery has become more and more prominent with the increase of energy density, and battery thermal runaway such as spontaneous combustion and explosion occurs frequently, which seriously restricts the further promotion and application of new energy vehicles. Finding the root cause of potential safety hazards, revealing the mechanism of battery failure, and building a high-safety battery system have become the focus and focus of current lithium battery research. The solid-state energy system technology center of Qingdao Energy Institute has been deeply engaged in the construction of high specific energy and high safety lithium battery system, and has achieved a series of breakthrough results in recent years.(Lithium - Ion Battery Equipment)
In commercial lithium batteries, polyolefin separators with poor dimensional stability and flammable and leaky organic electrolytes are important reasons for thermal runaway of batteries. Modification of them is the most direct way to improve battery safety. The Solid State Energy System Technology Center of Qingdao Energy Institute has developed a series of new flame-retardant and heat-resistant shrinkage diaphragms, including aramid diaphragms, cellulose-based composite diaphragms, and polyarylsulfone amide diaphragms, based on the relevant experience in the previous electrolyte/additive research. and polyimide separators, etc. (NanoEnergy, 2014, 10, 277-287; J. Electrochem. Soc. 2015, 162, A834-A838; Prog. Polym. Sci., 2015, 43, 136-164); at the same time, developed Cyclotriphosphazene flame retardant additives (ethoxy pentafluorocyclotriphosphazene, phenoxy pentafluorocyclotriphosphazene, hexaallylamine based Cyclotriphosphazene and phosphorus-based oligomers, etc.) (Adv. EnergyMater. 2018, 8, 1701398; J. Electrochem. Soc. 2021, 168050511), effectively improving the safety performance of lithium batteries. On the other hand, in trying to solve the safety hazard of electrolyte leakage, the team innovatively took the important component of 502 glue (ethyl cyanoacrylate (PECA)) as the starting point, and used strong nucleophilicity in the lithium-sulfur battery system. The sulfide fast ionic conductor (Li6PS5Cl) attacked PECA to prepare in-situ polymerization of large anion-regulated ether electrolytes. The electrolyte can be anchored on the polymer skeleton through hydrogen bonds, which can effectively prevent electrolyte leakage while achieving high conductivity, improve the safety of the battery, and open up new ideas in the field of electrolyte leakage prevention for lithium-sulfur batteries (Angew. Chem. Int. Ed., 2021, 202103209).
Although the preparation of high thermal stability separator and flame retardant electrolyte can effectively delay or slow down the violent exothermic behavior of the battery, it is still unable to fundamentally prevent the thermal runaway accident of the battery. Tracing the source, understanding the exothermic characteristics of lithium batteries from the microscopic level, and analyzing the triggers of the thermal runaway chain exothermic reaction and its evolution path are important prerequisites for building a high-safety battery system. On the basis of fully summarizing the thermal stability and thermal characteristics of battery materials, the team of researchers proposed that the thermal compatibility between battery materials (electrode materials/electrolytes/additives, etc.) is crucial to battery safety. The thermal stability of several points cannot ensure the improvement of the overall safety performance of the battery (EnergyStorageMater., 2020, 31, 72–86). In view of this, the team explored the failure mechanism of ternary high-nickel batteries at the material-battery level through in-situ/ex-situ coupling methods, and used isotope titration-mass spectrometry online gas detection devices to pioneer the negative electrode of NCM ternary batteries. The existence of H-ion was found on the side, and it was confirmed that this component has poor thermal compatibility with the electrolyte, which became an important trigger for inducing the chain exothermic reaction during the heating process of the battery. Moreover, through the self-designed in-situ detection device and method for thermal runaway gas shuttling of battery materials, it is proved that H2 appearing on the negative electrode side can shuttle to the positive electrode side, thereby accelerating the violent exothermic behavior and causing the battery thermal runaway (Adv. Sci., 2021, 2100676).
In commercial lithium batteries, polyolefin separators with poor dimensional stability and flammable and leaky organic electrolytes are important reasons for thermal runaway of batteries. Modification of them is the most direct way to improve battery safety. The Solid State Energy System Technology Center of Qingdao Energy Institute has developed a series of new flame-retardant and heat-resistant shrinkage diaphragms, including aramid diaphragms, cellulose-based composite diaphragms, and polyarylsulfone amide diaphragms, based on the relevant experience in the previous electrolyte/additive research. and polyimide separators, etc. (NanoEnergy, 2014, 10, 277-287; J. Electrochem. Soc. 2015, 162, A834-A838; Prog. Polym. Sci., 2015, 43, 136-164); at the same time, developed Cyclotriphosphazene flame retardant additives (ethoxy pentafluorocyclotriphosphazene, phenoxy pentafluorocyclotriphosphazene, hexaallylamine based Cyclotriphosphazene and phosphorus-based oligomers, etc.) (Adv. EnergyMater. 2018, 8, 1701398; J. Electrochem. Soc. 2021, 168050511), effectively improving the safety performance of lithium batteries. On the other hand, in trying to solve the safety hazard of electrolyte leakage, the team innovatively took the important component of 502 glue (ethyl cyanoacrylate (PECA)) as the starting point, and used strong nucleophilicity in the lithium-sulfur battery system. The sulfide fast ionic conductor (Li6PS5Cl) attacked PECA to prepare in-situ polymerization of large anion-regulated ether electrolytes. The electrolyte can be anchored on the polymer skeleton through hydrogen bonds, which can effectively prevent electrolyte leakage while achieving high conductivity, improve the safety of the battery, and open up new ideas in the field of electrolyte leakage prevention for lithium-sulfur batteries (Angew. Chem. Int. Ed., 2021, 202103209).
Although the preparation of high thermal stability separator and flame retardant electrolyte can effectively delay or slow down the violent exothermic behavior of the battery, it is still unable to fundamentally prevent the thermal runaway accident of the battery. Tracing the source, understanding the exothermic characteristics of lithium batteries from the microscopic level, and analyzing the triggers of the thermal runaway chain exothermic reaction and its evolution path are important prerequisites for building a high-safety battery system. On the basis of fully summarizing the thermal stability and thermal characteristics of battery materials, the team of researchers proposed that the thermal compatibility between battery materials (electrode materials/electrolytes/additives, etc.) is crucial to battery safety. The thermal stability of several points cannot ensure the improvement of the overall safety performance of the battery (EnergyStorageMater., 2020, 31, 72–86). In view of this, the team explored the failure mechanism of ternary high-nickel batteries at the material-battery level through in-situ/ex-situ coupling methods, and used isotope titration-mass spectrometry online gas detection devices to pioneer the negative electrode of NCM ternary batteries. The existence of H-ion was found on the side, and it was confirmed that this component has poor thermal compatibility with the electrolyte, which became an important trigger for inducing the chain exothermic reaction during the heating process of the battery. Moreover, through the self-designed in-situ detection device and method for thermal runaway gas shuttling of battery materials, it is proved that H2 appearing on the negative electrode side can shuttle to the positive electrode side, thereby accelerating the violent exothermic behavior and causing the battery thermal runaway (Adv. Sci., 2021, 2100676).
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