Non Technical Summary
Controlled-environment agriculture (CEA) is becoming increasingly popular because it provides significantly higher yields with while requiring 80% less water compared with conventional agricultural methods. One reason CEA can provide such impressive yields compared with conventional agriculture practices is due to the high level of environmental control, creating ideal growing conditions. Controlling light quality, nutrient levels, water and air temperature, growing media, humidity, and CO2 levels enables growers to target ideal conditions for each crop. However this control results in significant energy consumption. Supplemental CO2 typically from combustion of fossil fuels is currently utilized to support CO2 levels to maximize productivity and support photosynthesis inside these facilities.Li-CO2 batteries are energy storage devices capable of efficiently capturing CO2 from the ambient air, which is then released during charge while offsetting or replacing the need to draw energy from the grid by enabling energy storage from renewables. Giner will focus on development of a cathode engineered to facilitate selective capture and release of CO2 at commercially relevant rates utilizing a non-volatile electrolyte and carefully designed internal structure and catalyst. The resulting technology will be modular and scalable and flexible in form factor to customize for different environmental needs. In addition to providing a direct air capture method to supply CO2 to CEA facilities, the energy reseased during capture can be support the needs of growing facilities, such as lighting or temperature control, or stored in a power bank for later use. The proposed technology addresses both environmental and economic challenges for CEA resulting in a more economically competitive product.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
401	7410	2000	100%

Knowledge Area
401 - Structures, Facilities, and General Purpose Farm Supplies;

Subject Of Investigation
7410 - General technology;

Field Of Science
2000 - Chemistry;

Goals / Objectives
Indoor farming systems require controlled dosing of CO2 to maintain concentrations beneficial to plant growth. A shipping container can require 3 kg of supplemental CO2 per day, while a small greenhouse can require as much as 200 kg of supplemental CO2 per day. Currently, this is accomplished either by transporting compressed CO2 gas to a growing facility, or through combustion of natural gas or propane. In most cases, a CO2 sensor controls a CO2 generator that burns natural gas or propane to produce CO2. A lithium carbon dioxide (Li-CO2) battery is an ideal solution to address the dual challenges of CO2 generation and reducing energy consumption. A Li-CO2 battery captures CO2 from the air to be later released into the growing space. In the process, the Li-CO2 battery provides energy during the CO2 capture process which could be used to support the CEA systems power needs. In Phase I Giner Labs will develop a novel Li-CO2 battery to capture and release CO2 to increase production in controlled agricultural environments, while providing energy that can be utilized to power the facility.Based upon the more mature Li-air battery technology, Li-CO2 and Li-CO2/O2 batteries utilize CO2 as an active cathode material, and during discharge, convert CO2 to Li2CO3. The conversion of CO2 to Li2CO3 generates energy, thereby acting as an energy storage device as well as a carbon capture device. In Phase I, Giner will develop a novel cathode for Li-CO2 battery and demonstrate reversible CO2 capture and controlled release in a small scale (coin cell) Li-CO2 battery.To accomplish this, Giner Labs has identified goals and measurable milestone metrics for each.Goal 1. Develop and characterize porous IL-GPE materials.Objective 1: Fabricate IL-GPE with bulk conductivity >10-2 mS/cm, 100% elongation before breaking, and which is electrochemically stable between 2.5-4.4 V. Down select three IL-GPE materials to incorporate into electrodes.Goal 2. Fabricate and characterize IL-GPE composite cathodes.Objective 2: Fabricate mechanically stable cathode electrode with >50% porosity and electrical conductivity >1 mS/cm.Goal 3. Electrochemically evaluate cathodes in full Li-CO2 cells.Objective 3: Demonstrate 50 discharge/charge cycles to 500 mAh/g with >95% CO2 recovery. Goal 4. Perform postmortem analysis of cycled components.Objective 4. Identify failure mechanisms for Li-CO2 IL-GPE cathode electrodes.Goal 5. Perform technoeconomic feasibility study.Objective 5. Complete feasibility study, identifying targets met and recommend mitigation or improvement strategies where the technology is found to fall short of targets.Once developed, the proposed Li-CO2 battery is expected to reduce costs in CEA facilities in three main categories:Dehumidification and cooling are reduced, leading to an expected reduction in electricity consumption from 3.92 Wh/m2 to 3.28 Wh/m2 a 16% reduction in electricity consumption.Realize an additional 2-5% reduction in due to renewable energy storage.CO2 supply costs would also be reduced by 45% by switching from natural gas consumption

Project Methods
The outlined goals will be achieved through 5 tasks:Task 1: Develop and characterize porous IL-GPE materials. Several IL-GPE compositions will be prepared to evaluate the bulk properties of the potential IL-GPE materials. LiTFSI will be incorporated into each candidate IL at concentrations ranging from 0.25 - 1.0 M and combined with poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP). The candidate ILs were selected specifically to be CO2 selective and have demonstrated CO2 à Li2CO3 performance. The ratio of IL to polymer will be varied from 4:1 to 1:4, prepared in 1-methyl-2-pyrrolidone (NMP) solvent. Following procedures found in the literature, freestanding porous films will be cast on glass slides and submerged in a coagulation bath for 1, 3, 5, and 10 minutes, varying temperatures between 25°C and 60°C before drying under vacuum at 85°C for 24 hours. The resulting materials are characterized as described below. The three best candidate IL/polymer combinations will be incorporated into the cathode in Task 2.IL-GPE Flexibility will be evaluated by mechanical testing involving repeated bending, flexing, and rolling. SEM imaging will compare each electrode before and after mechanical testing to evaluate the effect on the polymer scaffold morphology.Ionic conductivity will be evaluated by assembling IL-GPE membranes in symmetrical cells between two lithium electrodes. Electrochemical impedance spectroscopy will be done over a frequency range of 1Hz to 100k Hz and an input voltage amplitude of 10 mV. The high-frequency intercept will be used as the electrode resistance (Rm) and converted to ionic conductivity by the following equation: σ = 1/ (Rm x T)/A, where σ is ionic conductivity, T is membrane thickness, and A is membrane area. IL-GPE will be compared against glass fiber separators soaked in IL/LiTFSI without polymer. Impedance analysis will be completed to fully characterize the cell impedance components.Cyclic Voltammetry The freestanding IL-GPE will be assembled into symmetric cells between two lithium disks and scanned over a voltage range from 2.0 V to 4.8 V. at a rate of 1 mV/sec between 2.5 V and 4.5 V. Three scans will be completed to evaluate the electrochemical stability window of each IL-GPE.SEM imaging. Top-down and cross-sectional imaging will be used to measure membrane thickness, porosity, and uniformity.Task 2. Fabricate and characterize IL-GPE composite cathodes. Cathodes will be fabricated, using the down-selected IL-GPE materials from Task 1. Giner has significant experience designing and tuning electrode structures to accommodate products. Conductive carbons, carbon nanotubes, and MoS2 nanoflakes will be incorporated into the IL-GPE matrix to form a composite cathode, where the IL-GPE acts as a binder and electrolyte. The ratio of MoS2/conductive carbons will be varied from 1:10 to 1:5. The IL-GPE will vary from 5 - 25% of the electrode weight. A slurry will be prepared with MoS2/CNF, ionic liquid, PVDF-HFP, and NMP, and the resulting slurries will be cast onto an aluminum wire mesh to act as a current collector and submerged in a coagulation bath using parameters developed in Task 1. Electrodes will be fabricated with MoS2 loadings between 0.05 - 0.2 g/cm2. Pore volume and size will be tuned by controlling IL-GPE concentration, coagulation time and temperature, and slurry dilution.IL-GPE Composite Cathode Flexibility and Stability will be evaluated by mechanical testing involving repeated bending, flexing, and rolling. SEM imaging will compare each electrode before and after mechanical testing to evaluate the effect on the polymer scaffold morphology. An adhesive tape will be pressed onto the surface of the electrode and peeled off. An electrode will mechanically fail if significant electrode is removed with the tape.Through Plane Electrical Conductivity. The electrode will be placed between two flat gold plates and placed under mild compression to ensure good contact. Direct current internal resistance (DCIR) measurements will be made to evaluate the through plane conductivity of each electrode, to ensure a continuous electronically conductive pathway throughout the electrode. Three separate sections from each electrode will be evaluated to ensure uniformity across the whole structure.Selectivity of IL-GPE A film of the IL-GPE will be placed between two vials of an H-Cell and crossover of humidity and O2 will be evaluated to screen each composition for CO2 selectivity. One side will be purged with dry N2 and the opposite side will be purged with CO2, O2 and 100% RH N2. GC samples will be taken from the initially dry N2 and analyzed using GC to quantify the selective crossover for each condition.SEM imaging. Top-down and cross-sectional imaging will be used to measure cathode thickness, porosity and pore structure, and uniformity.Task 3. Evaluate Electrochemical Performance of IL-GPE composite cathode in full Li-CO2 battery. The IL-GPE composite cathodes will be assembled into coin cells vs Li anodes. A Whatman glass fiber separator soaked in LiTFSI in IL will be used as a separator, with IL and LiTFSI concentration matching that contained in the IL-GPE for each cathode tested. AC impedance of each cell will be taken before testing and at end of life. DCIR will be taken after each cycle to monitor cell heath. Cells will be assembled into the air-breathing coin cell fixtures and cycled in hermetically sealed boxes purged with dry CO2/N2 and CO2/O2/N2 mixtures. In-house test fixtures equipped with pressure monitoring capabilities to monitor CO2 consumption and evolution will be used as well as in-house analysis via gas chromatography (GC) analysis of regenerated gas composition.Cyclic Voltammetry. Voltage scan at a rate of 1 mV/sec between 2.5 V and 4.5 V. The Li-CO2 battery typically has a discharge plateau at 2.8 V and a charge plateau between 4.2 V and 4.4 V (Ahmadiparidari et al. 2019). Three scans will be completed to confirm reversible reaction.Reversible Cycling. Cycling will be conducted between 2.5 V and 4.5 V. The cells will be discharged and charged at 100 mA/g MoS2 to 500, 1000, and 1500 mAh/g capacity (5, 10, 15- hour discharge/charge times) at room temperature to optimize conditions for 100% release of CO2 from the reaction product. Efficiency and voltage during charge and discharge will be monitored during cycling to evaluate cell health.CO2 capture and release rate Monitoring of CO2 generation and capture rates and Coulombic efficiency during charge and discharge at 50, 100, 250, and 500 mA/g will be conducted by recording internal pressure in the cell chamber during charge and discharge of the battery. Gas samples will be taken after discharge and charge and analyzed via in-house GC to confirm CO2 capture and release efficiency.Task 4. Postmortem Analysis. Cathodes will be analyzed after cycling to evaluate reaction product and cathode mechanical stability. Cells will be disassembled in the discharged state and reaction product Li2CO3 will be confirmed via EDX. Controlled cycling will be conducted to evaluate cells over a range of charge and discharge states. Porosity and electrode structure will be compared to fresh electrodes. Cells discharged to the same depth of discharge and subsequently charged will be disassembled after charge and analyzed for evidence of incomplete charge or side reactions and unexpected products. Cells that have undergone extended cycling will also be disassembled and analyzed to identify changes in electrode structure and failure mechanisms.Task 5. Technoeconomic feasibility study. A paper study on the technoeconomic feasibility of the best performing cathode will be completed to provide a foundation for Phase II. The objective will be to evaluate how the best performing cathode meets the CO2 production, cost, and energy savings targets required to facilitate adoption of this technology into CEA.