During the dates of September 13-15, 2022, EE Times hosted its Green Engineering Summit. The purpose of the meeting was to have a roundtable discussion about the progress, obstacles, and potential future of various companies developing carbon-cutting technologies. Renewable energy production, energy conversion efficiency via Wide Band Gap (WBG) semiconductors, energy storage system R&D, electronic-based real-time control in agriculture, environmental monitoring, and modelling were all areas of emphasis.
This article is a summary of a talk delivered by Polarium’s Senior Battery Technology Engineer, Dr. Henrik Lundgren. Topic of the lecture was “How Lithium Battery Technology is Powering Sustainable Development.” Swedish company Polarium creates energy storage solutions for telecommunications, businesses, and factories.
Dr. Lundgren began by noting the modern world’s reliance on batteries in items like mobile electronics. This reliance will increase as we progress toward a more environmentally friendly and sustainable future.
Three key application areas include
- Devices and networks that use the fifth generation of wireless technology, or 5G. Over the next decade, this is expected to increase by a factor of 81, which is an astounding pace of growth. Since more things, such as appliances, switches, monitoring devices, etc., will need to be connected to the internet, as well as be charged and used in mobile applications, there will be a larger demand for energy storage. Furthermore, these networks necessitate data centre servers, which in turn necessitate battery backup.
- Vehicles that run on electricity (EVs). As society shifts away from using fossil fuels, the electric vehicle market has exploded. As battery costs decrease, electric vehicle (EV) adoption is expected to skyrocket over the next decade, making battery systems and charging infrastructure crucial to the transition.
- Sources of energy that can be replenished naturally. Energy storage devices make it possible to collect this sunshine when it’s plentiful and then use it when it’s most required. Not only are battery systems necessary for large-scale utility power generation sites, but they are also crucial for smaller, more decentralised micro-grids and houses with solar panels. It is predicted that by 2035, the amount of energy produced from sun and wind would have increased by a factor of five.
Polarium’s primary energy storage offering is lithium-ion batteries (LIB).
Below are some of the benefits of LIBs over regular lead acid batteries (LAB)
- Among metals, lithium (Li) is the most preferable for use in batteries due to its low weight and high electronegativity (-3.05 V) /reduction potential. Compared to state-of-the-art LIBs at the cellular level, a LAB’s gravimetric energy density of around 30 Wh/kg is roughly 1/10th. This means that a LIB module can provide the same performance as a LAB module (rated voltage and capacity), but at a fraction of the weight and size.
- If you compare LIBs to LABs, you’ll notice that the former has a significantly higher discharge tolerance (95%) than the latter (50%). Furthermore, LABs have a much more linear relationship between battery capacity and discharge current than other battery types do; this means that a given LAB will deliver less than its rated capacity when subjected to higher currents. Compared to SR, this correlation is substantially weaker in LIBs.
- Compared to LIBs, which are designed for continuous use, the cycle life of a LAB, which is intended for intermittent usage, is inferior and hence, a LAB must be replaced at a faster rate. Unlike LABs, LIBs can be manufactured to last for 15–20 years on a calendar and survive 6,000 cycles. The increased price of LIBs can be balanced out by this.
- Since LIBs have a better temperature tolerance than LABs, they require less or no cooling to function.
- The turnaround charge efficiency of LIBs is 97%, while that of LABs is only 75%.
- LIBs also have a higher cell voltage (3.7 V versus 2.0 V), which allows them to be recharged more quickly and last longer between charges.
Within a porous plastic separator, the electrolyte is typically an organic solvent like LiPF6. More specifically, the material and content of the electrodes can be altered to achieve the sought-after qualities.
- The Positive Electrode: The cathode is another name for this. There are two primary chemical processes that can be used:
- Nickel-based. To name a few examples, we have lithium-nickel-manganese-cobalt oxide (NMC or LiNixMnyCozO2) and lithium-nickel-cobalt-aluminum oxide (LNCAlO2) (NCA or LiNixCozAlzO2). Figure 3 demonstrates how the x, y, and z element ratios in NMC can be tuned to maximise energy, power, or cycle life. Particularly in the case of NMC variants with a high Ni concentration, NMC cells share several characteristics with NCA cells. The energy density of NMC cells has improved quickly in recent years, with cutting-edge cells expected to achieve about 270 Wh/kg by 2020. Energy density is improved by increasing the Ni concentration, but safety and cycle life are sacrificed.To improve safety without sacrificing efficiency, scientists are working to expand the Ni ratio from 1:1:1 to 8:1:1. When compared to other commercially available positive electrode materials, NCA offers the highest energy density. When it comes to NMC and NCA cells, a limited Depth-of-Discharge (DOD) and reduced maximum State-of-Charge (SOC) can maximise their longevity, with, for instance, a DOD of 80% having a much higher cycle life compared to a DOD of 100%. Due to the fact that both NMC and NCA use precious metals, the cost of the batteries must take this into account. Cost savings for NMC and NCA cell-based batteries are expected as LIB recycling becomes more commonplace.
- Iron-based. The Lithium, Iron, and Phosphate (Li-Fe-P) chemistry is the most often used (LFP or LiFePO4). Material prices are reduced, safety is increased, and a wider variety of materials can be used. Figure 4 demonstrates, however, that compared to Ni-based cells, LFP has a significantly lower energy density.
Also, the open-circuit voltage of LFP cells is rather constant regardless of state-of-charge. Because of this, balancing cells and calculating state-of-charge levels is more challenging. In addition, the self-discharge rate of LFP cells is higher, making them unsuitable for uses that need lengthy periods of standby or storage. Given the low value of the metals used, LFP cells have a lower recycling value than their Ni-based counterparts.
- The Negative Electrode: The anode is another name for this part. Here, we see two primary variants::
- Graphite. With regards to LIBs, this is the most typical negative electrode. Graphite is typically a combination of natural and synthetic varieties. Graphite has a high energy density and a long cycle life, but its electrode potential is so similar to that of metallic Li that it poses a risk of short circuits across the dendrites of the Li metal during charging. Extremely low temperatures and rapid charging present a greater danger.
- Silicon (Si). In theory, silicon’s capacity is ten times that of graphite. This is a drawback since volume expansion reduces the cycle life. Due to this, LIBs now use graphite electrodes doped with 2% nano-particles of Si content instead of pure Si, with research ongoing to increase this to the 20% range. The capacity of Si-containing LIBs will be higher than that of pure graphite LIBs at low cell voltages ( 3 V for NMC cells).
Safety Considerations with LIBs
Because LIB cells store between five and ten times as much chemical energy as electrical energy, they can be extremely dangerous in the wrong hands. Overheating, overcharging, overdischarging, and overheating are all examples of these. To keep an eye out for and stop these problems, a Battery Management System (BMS) is a must. The cells’ safety can be guaranteed through the use of BMS, the selection of high-quality materials during production, and the use of stringent testing and quality standards.
Some Future Trends in Batteries
- All-Solid-State Power Sources. This involves the substitution of a ceramic or polymer for the liquid electrolyte, which in turn offers energy densities as much as 50 percent higher than those attained with conventional LIB cells, in addition to vastly enhanced safety. Li metal anodes can be used with these cells to boost their efficiency even more.
- Batteries that use sodium ions Current cells have a much lower energy density, but they would be lot cheaper to construct. The study of this cell is in its infancy.
The development time for each of these projects is estimated to be between 5 and 10 years, making LIBs the most viable energy storage alternative for the foreseeable future.