The IDEMA project tackles the study of the failure mechanisms, and their mitigation, for a high-capacity lithium-ion battery with innovative formulation, constituted by a cobalt-free positive electrode, a silicon-based negative electrode and an advanced aprotic electrolyte. The IDEAMA project will last 24 months and will imply the cooperation of three permanent Sapienza Staff (Sergio Brutti, Alessandro Latini and Domenico Stranges), one non-permanent PhD student (Alessio Luongo) and one non-permanent post-doc (to be hired, assegno di ricerca).
The project tackles four parallel closely interacting activities related to four different secondary goals. These research activities (workloads) are illustrated and described below.
The main goals of the project are:
1) To study the fundamental chemical mechanisms underneath the irreversible degradation of the battery constituents (i.e. electrodes, electrolytes) leading to gas release upon thermal abuse.
2) To develop mitigation strategies to improve the thermal stability of the proposed battery formulation.
The project is organized in four workpackages led by the three permanent staff memebers from Sapienza.
In summary this project tackles the study of the parasitic chemistry leading to gas release and its mitigation for an innovative LIB formulation. We adopt a bottom-up approach starting from the unexplored analysis of the thermal degradation of electrodes/electrolytes and then approaching the monitoring of gas release in full LIBs under realistic experimental cycling conditions. Once done we extend this study to further enhanced LIBs where mitigation strategies have been incorporated in the cell formulation.
The current formulation of lithium-ion batteries (LIBs) is constituted by LiCoO2/graphite and a carbonate-based electrolyte with LiPF6 salt [1]. This formulation cannot be simply upscaled from mobile electronics to transportation due to costs, environmental malignity, and chemical hazards upon abuse [2].
The proposed project investigates the degradation chemistry and gas release mitigation strategies of an innovative LIB formulation demonstrated by us previously [3]. In our formulation a high capacity Co-free lithium iron phosphate, i.e. LiFePO4, is coupled with a high capacity silicon-carbon composite and the carbonate based electrolyte is improved by adding trifluoromethyl sulphonyl imide based ionic liquids able to enhance thermal stability and resilience upon abuse. This combination of innovative materials discloses remarkable enhancement compared to the state-of-the-art in terms of environmental benignity, safety and performance [3].
The IDEMA project starts from this solid background and tackles the investigation of the failure mechanisms of this innovative LIB formulation to foster further innovations to mitigate the gas release upon thermal abuse. The project tackles four parallel closely interacting activities:
(1) Analysis of the thermal stability of electrode materials by monitoring structural alterations and gas release
(2) Investigation of the degradation mechanism at high temperature of electrolyte components by identification of the pyrolysis elementary steps
(3) Study of the gas release in fully assembled cells under operation at room temperature and upon thermal abuse
(4) Development and testing of mitigation strategies on the gas release of the LIB in relevant working conditions
The first relevant innovation pursued is to shed light on the multiphase chemical reactivity at high temperature of electrodes (activity 1) and the development of a comprehensive reactive scheme of the thermal breakdown of the electrolytes (activity 2). These two goals aim at paving a fundamental description of the degradation chemistry at high temperature of the constituent elements of our innovative LIB formulation that leads to gas release.
In the literature the description of the most relevant degradation chemistry routes in LIBs leading to gas release have been investigated in the past (see as examples [4,5]). The most relevant understanding consolidated in the literature is the remarkable dependence of the parasitic chemistry on the interaction between the different constituent elements of any full LIB formulation [6,7].
Thus, starting from the solid description of the thermal degradation routes of electrodes and electrolytes components, the further innovation pursued by this project is the analysis of the gas release of the full LIB formulation upon operation at various temperatures (activity 3). A close matching among outcomes from the studies of the degradation of electrodes/electrolytes and the full cell will disclose a knowledge-based description of the parasitic reactive channels in a relevant environment. This knowledge represents itself a remarkable innovative achievement that allows the comprehension of the chemistry beyond the release of permanent gases and the interplay between electrochemical cycling conditions, temperature and gas release.
Once established, this analysis of the degradation chemistry of our LIB formulation will allow to evaluate the relative merit of the proposed mitigation strategies (i.e. the use of lithium oxide and lithium hydroxide as electrode/separators additives) able to minimize the gas release (activity 4). The adoption of these mitigation strategies has been discussed in the literature for different LIB formulations [7] and it is here proposed for the first time on our innovative cell configuration.
In summary this project tackles the study and mitigation of the parasitic chemistry leading to gas release in an innovative LIB formulation. We adopt a bottom-up approach starting from the unexplored analysis of the thermal degradation of electrodes/electrolytes and ending to the implementation of mitigation strategies in the LIB formulation.
[1] B. Scrosati, J. Garche, J. Power Sources. 195 (2010) 2419¿2430. [2] M. Hu, X. Pang, Z. Zhou, J. Power Sources. 237 (2013) 229¿242. [3] A.Celeste, ..., A.Matic, V.Pellegrini, S.Brutti, Batteries & Supercaps (2020) in press, https://doi.org/10.1002/batt.202000070; [4] W.Kong et al. J.Power Sources 142 (2005) 285-291 [5] Y.Fernandes et al. J. Power Sources 414 (2019) 250-261 [6] Z.Liao et al. J. En.Chem, 49 (2020) 124-135. [7] S.Nowak. M.Winter. J.Electrochem. Soc. 162 (2015) A2500¿A2508