Gas production is very common in lithium-ion batteries using liquid electrolyte, usually lithium-ion battery production is mainly in two stages: the first is the phase, with Li + continuously embedded in the anode, the negative potential decreases gradually, when the negative potential drops to about 1V, the solvent in the electrolyte such as EC, 2, C2H4As well as additives in the electrolyte, such as VC, FEC, etc. began to decompose on the anode surface, forming the SEI film we know, and producing Co, CO And so on, so the soft-pack Li-Ion battery in the production process will be reserved gas chamber, and in the gas after gas discharge; The second stage of gas production is mainly in the case of lithium-ion batteries due to improper use of the overcharge, liquid electrolyte not only in low potential when the reduction of decomposition, the potential is too high when the anode surface oxidation decomposition, such as we have previously reported, the French national Orleans University of Y. 2 (47%) , H2 (23%) , C2H4 Fernandes and others study shows that the main gases released during the overcharge process of lithium-ion batteries include Co (10%), CO (4.9%) 2H5and C F (4.6%) (What gas does the lithium-ion battery produce in the overcharge?)
, while the lithium-ion battery cycle is accompanied by sustained gas production, it is much smaller than the two phases. In general, we believe that gas production is the use of liquid electrolyte lithium-ion battery ' patent ', and the use of solid electrolyte lithium-ion batteries, because of solid electrolyte stability, not easy to decompose, so we generally believe that all-solid-state lithium-ion batteries are not gas-producing. But studies by Timo Bartsch of the Karlsruhe Institute of Technology in Germany (first author, communications author), Jürgen Janek (communication authors) and Torsten Brezesinski (communication authors) show that the use of high NI layered cathode materials and sulfur phosphate solid electrolyte systems 2All-solid-state batteries will still produce a co after the charging voltage exceeds 4.5V 2and O 2, further studies have shown that CO 2Mainly from the decomposition of carbonate on the surface of the cathode material, and O
is mainly from the decomposition of high nickel cathode material phase. 3In the experiment, Timo Bartsch used NCM622 as cathode material, β-li 4Ps 4As electrolytes, with metal in and Li 5O12Ti As negative. 2We all know that when NCM622 material is exposed to air, it is associated with moisture in the air and Co 2React to produce Li on the surface of the particles 3CO 2, in order to reduce the particle surface carbonate impurities, Timo Bartsch will NCM622 material at 740 ℃ high temperature, oxygen environment heat treatment 2h, the use of titration test shows that the NCM622 material surface Li 3CO The content decreased from 0.09% to 0.03%, but after the treatment of the NCM622 material and Β-LI3PS4 composed of the whole battery, during the first charge of the process will cause solid electrolyte decomposition, resulting in the cycle of polarization increased, so Timo 2Bartsch that the NCM622 material surface suitable li 3CO It is still very necessary to stabilize the interface. 213Therefore, in subsequent experiments, the isotope tracer method was used to generate a layer containing 95% 13C of Li on the surface of the NCM622 particle. 3CO
Layer (content of about 0.72wt%), which is used to track the origin of gases in all solid-state batteries. The isotope-labeled NCM622 material and the solid electrolyte form a flake battery, and then in the 45 ℃, the 2.9-5.0v between the c/20, the small magnification of the cycle, and the use of mass spectrometer to monitor the production of gas. First, the Timobartsch is tested with metal in as a negative electrode, the charge ratio of NCM622 material is 240mah/g, the discharge capacity is 204mah/g, and the first efficiency is 85% during the first charge and discharge process. 2In-situ detection by mass spectrometer found that the above-mentioned all-solid-state batteries in the use of the main gas produced by H 2, CO 2and O 2, where H Just a very sharp peak was produced in the instant of the power, which the authors believe is mainly due to the decomposition of the trace water in the system. 2and O 2will be generated in each cycle, when the voltage reaches 4.5V in the first cycle O 2When the maximum cutoff voltage is reached, the O 2The release amount reaches the maximum, followed by a few cycles O 2, the authors believe that this is mainly the NCM material in the high Soc, decomposition release O
Caused by. 2From Co 2Release, a small release peak occurs after the voltage reaches 4.0V, and then starts to release mass after the voltage reaches 4.5V, which can be seen from the mass spectrometry, releasing the CO 2Species are mainly isotope-labeled 13CO 2, a small amount of normal 12CO 2, which is generated with the NCM622 particle surface, Li 3CO 213Ingredients (95% of Li 3CO 2, 5% of ordinary Li 3CO 2), which indicates that the CO in all-solid-state batteries 2Mainly from the NCM622 material particle surface of Li 3CO 2Decomposition, with O 2Same in the first charge and discharge of CO 2The production volume is the largest, followed by the two cycles of CO has been gradually reduced. 2But the author also noticed a detail here that the CO detected in the first three cycles 2The total gas is only NCM622 particle surface li 3CO About 7% of the total, which may have two reasons: first, the decomposition rate of carbonate is much slower in all-solid-state batteries; Or the resulting gas interacts with the solid electrolyte, where physical adsorption or chemical adsorption occurs.
But in any case, the total solid-state battery production capacity compared to liquid electrolyte lithium ion batteries are much smaller, which is a clear advantage of all-solid electrolyte. 3Timo Bartsch's work has made us realize that even all-solid-state batteries can still face the problem of gas production, for NCM622 materials and Β-li 4Ps 2An all-solid-state battery system consisting of an electrolyte and a metal in anode that produces the co during the cycle 2and O 2Two kinds of gases, of which co 2Mainly from the NCM622 particle surface of Li 3CO 2The decomposition, O
