Project R-11567

Novel hybrid organic-inorganic active material for high-capacity and sustainable lithium-ion batteries (Research)

Modern civilization undoubtedly requires a fast-increasing amount of energy, and has become very dependent on fossil fuels of finite supply and uneven distribution. In that respect, during the past decade there has been a surge of investments in renewable energy generation, wind and solar power being the most prolific. Importantly, none of these renewable energy sources can be directly harnessed to power the transportation sector. The most convenient form of energy storage is portable chemical energy, which is the reason for our addiction to polluting fossil fuels for heat, propulsion, lighting, and communication. The battery, on the other hand, provides the portability of stored chemical energy but is void of any exhaust gases. In addition, most alternative energy sources are preferably converted into dc electrical energy, which is ideal for storage as chemical energy in a battery. Moreover, batteries have the ability to release the stored energy again as electrical energy with a very high conversion efficiency. A LIB has three main components: an anode, a cathode and a (usually liquid) electrolyte. The most widespread cathode material so far is LiCoO2, as found in the first commercial LIBs since 1991 (Sony). Upon battery discharge, the lithium ions travel back to the cathode and produce an external electrical current. During cell operation at 3.0–4.2 V, however, the surface reactivity and instability of the delithiated Li1-xCoO2 structure limit the practical capacity of the LiCoO2 electrodes to approximately 140 mAh/g(4). These limitations, together with the high possibility of thermal runaway caused by cell overcharge and short circuit in inadequately controlled batteries and the relatively high cost of cobalt, have led to enormous efforts since 1991 to find alternative cathode materials to LiCoO2 that provide Li-ion cells with superior energy density, rate capability, safety, and cycle life. Despite showing potential, none of them have succeeded in combining all of the desired properties. They are typically higher in capacity but less thermally stable (LiNi0.8Co0.15Al0.05O2, LiMnxNiyCo1-x-yO2), or they are more stable upon Li extraction but have lower capacity (spinel LiMn2O4 and olivine LiFePO4). Li metal is theoretically the best anode material for LIBs, with an extremely high specific capacity but due to the technical hurdles of Li metal as the anode material have led to the use of carbon-based materials as the most widely used anodes in LIBs. Several elements that form compounds with Li have been explored as alternatives (Sn, Sb, Si, Ge), among which Si is the most attractive owing to its high theoretical specific capacity of 4200 mAh/g. In a nutshell, the body of research invested into anode and cathode materials for LIBs is enormous, yet great challenges still exist for each of them, and relate to capacity, cycling stability, safety and cost. If LIBs are to continue revolutionizing energy storage on a larger scale (e.g. prolific electrified transportation), these obstacles urgently need to be eliminated. Intriguingly, it appears that hybrid metal halide perovskites (HMHPs) can be of particular interest for tackling each of the existing challenges on a short timescale. Unlike typical ACE materials, HMHPs are mechanically resilient, easy to synthesize from solution, from cheap chemicals, and in most cases even close to room temperature. HMHPs also have highly tunable electronic and ionic properties in the relevant range for ACE materials, rendering them a high-potential candidate material class for implementation in superior new generation LIBs in terms of capacity, cycling stability, safety and cost. Their soft mechanical properties even make them excellent candidates for flexible batteries. Provided the appropriate fine-tuning, HMHPs can be explored as anode, cathode, and solid electrolyte, or a combination of these.

01 December 2019 - 30 November 2023