Solar photovoltaic (PV) energy generation depends greatly on weather conditions, leading to a gap between demand and supply . Therefore, combining photovoltaics energy generation and batteries energy storage is of high interest which can reduce the usage of fossil fuels 2. Batteries to be integrated with a PV module in a PV-Battery system need to have high capacity and long cycle life in the temperature range of -20 – +70 °C using low-cost abundant materials.
Lithium-ion batteries (LIBs) are among the most promising energy storage systems, which can be utilized in an integrated PV-Battery system. Graphite (Gr) is a commonly used anode active material in commercial LIBs due to its long cycle life, low cost, high coulombic efficiency (CE) and low working potential (~ 0.2 V vs Li/Li+). However, its low theoretical capacity of 372 mAh.g-1 limits its usage for high-energy density battery applications. Silicon (Si) on the other hand has high abundancy, low cost, low operating potential (~ 0.2-0.4 V vs Li/Li+), and high theoretical capacity of 4200 mAh.g-1 (Li4.4Si) and 3590 mAh.g-1 (Li3.75Si) at 415 °C and room temperature (RT) respectively. In spite of all these advantages, Si goes through large volume expansion (≥280%) during charge/discharge, which results in mechanical stress and pulverization if Si particles. Utilizing Si/Gr blend anode with designer polymeric binders is one method to overcome the challenges of Si and Gr active materials by presenting a synergistic benefits of both components [3,4].
In this work, Si/Gr anodes and LiPAA/CMC dual binder system were optimized used with a NMC 622 cathode in a coin cell configuration and investigated in a PV-Battery system. To improve the thermal behaviour of the system, electrolyte additives such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), and high-temperature enabler silane-based additives (TEOSCN)  were used. The electrochemical measurements were carried out on anode and cathode half-cells (vs. Li/Li+) as well as Si/Gr||NMC622 full-cell at c-rates up to 3C at room temperature (RT), 45 °C, and 60 °C. At 60 °C, NMC622 |Li and Si/Gr||NMC622 show higher initial capacity is observed which is followed by a rapid capacity loss, which suggests further optimization of electrolyte formulation. After deep charge and discharge at 3C, the Si/Gr anode half-cell shows 98.36% and 88.65% capacity recovery at RT and 60 °C respectively.
The developed LIB with Si/Gr anode and TEOSCN electrolyte additive was used in a PV-Battery system with a 15.31% efficient perovskite solar cell (PSC) using a DC-DC booster converter, which resulted in an overall efficiency of 8.74% under 2C charging rate at RT. Usage of Si/Gr blend anode in combination with TEOSCN electrolyte additive showed promising results in the development of integrated PV-battery systems. With further optimizing the cathode and electrolyte system, high-temperature electrolyte additives such as TEOSCN can help to improve the development of integrated PV-battery systems.
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