Currently, the most commercially successful batteries are lithium-ion batteries. After lithium-ion technology is applied to portable electronic devices, it has entered the fields of industrial applications, power systems, Photovoltaic energy storage and electric vehicles.
Lithium-ion batteries outperform many other types of rechargeable batteries in many aspects, including energy storage capacity, number of duty cycles, charging speed, and cost-effectiveness. Currently, the only issue is safety, flammable electrolytes can catch fire at high temperatures, which requires the use of electronic control and monitoring systems.
Lithium is the lightest of all metals, has the highest electrochemical potential, and offers higher volumetric and mass energy densities than other known battery technologies.
Lithium-ion technology has made it possible to drive the use of energy storage systems, mainly associated with intermittent renewable energy sources (solar and wind) and has also driven the adoption of electric vehicles.
Lithium-ion batteries used in power systems and electric vehicles are of the liquid type. These batteries use the traditional structure of an electrochemical battery, with two electrodes immersed in a liquid electrolyte solution.
Separators (porous insulating materials) are used to mechanically separate the electrodes while allowing the free movement of ions through the liquid electrolyte. The main feature of an electrolyte is to allow the conduction of ionic current (formed by ions, which are atoms with excess or lack of electrons), while not allowing electrons to pass through (as happens in conductive materials). The exchange of ions between positive and negative electrodes is the basis for the functioning of electrochemical batteries.
Research on lithium batteries can be traced back to the 1970s, and the technology matured and began commercial use around the 1990s.
Lithium polymer batteries (with polymer electrolytes) are now used in battery phones, computers and various mobile devices, replacing older nickel-cadmium batteries, the main problem of which is the “memory effect” that gradually reduces storage capacity. When the battery is charged before it is fully discharged. Compared to older nickel-cadmium batteries, especially lead-acid batteries, lithium-ion batteries have a higher energy density (stores more energy per volume), have a lower self-discharge coefficient, and can withstand more charging and the number of discharge cycles, which means a long service life.
Around the early 2000s, lithium batteries began to be used in the automotive industry.
Lithium-ion batteries can have different performances, lifespans, and costs, depending on how they’re made. Several materials have been proposed, mainly for electrodes.
Typically, a lithium battery consists of a metallic lithium-based electrode that forms the positive terminal of the battery and a carbon (graphite) electrode that forms the negative terminal.
Depending on the technology used, lithium-based electrodes can have different structures. The most used materials for the manufacture of lithium batteries and the main characteristics of these batteries are as follows:
- Lithium and Cobalt Oxides (LCO): High specific energy (Wh/kg), good storage capacity and satisfactory lifetime (number of cycles), suitable for electronic devices, disadvantage is specific power (W/kg) Small, reducing the loading and unloading speed.
- Lithium and Manganese Oxides (LMO): allow high charge and discharge currents with low specific energy (Wh/kg), which reduces storage capacity.
- Lithium, Nickel, Manganese and Cobalt (NMC): Combines the properties of LCO and LMO batteries. In addition, the presence of nickel in the composition helps to increase the specific energy, providing greater storage capacity. Nickel, manganese and cobalt can be used in varying proportions (to support one or the other) depending on the type of application. Overall, the result of this combination is a battery with good performance, good storage capacity, long life, and low cost.
- Lithium, nickel, manganese and cobalt (NMC): Combines features of LCO and LMO batteries. In addition, the presence of nickel in the composition helps to raise the specific energy, providing greater storage capacity. Nickel, manganese and cobalt can be used in different proportions, according to the type of application (to favor one characteristic or another). In general, the result of this combination is a battery with good performance, good storage capacity, good life, and moderate cost. This type of battery has been widely used in electric vehicles and is also suitable for stationary energy storage systems.
- Lithium Iron Phosphate (LFP): The LFP combination provides batteries with good dynamic performance (charge and discharge speed), extended lifetime and increased safety due to its good thermal stability. The absence of nickel and cobalt in their composition reduces the cost and increases the availability of these batteries for mass manufacturing. Although its storage capacity is not the highest, it has been adopted by manufacturers of electric vehicles and energy storage systems due to its many advantageous characteristics, especially its low cost and good robustness;
- Lithium and Titanium (LTO): The name refers to batteries that have titanium and lithium in one of the electrodes, replacing the carbon, while the second electrode is the same used in one of the other types (such as NMC – lithium, manganese and cobalt). Despite the low specific energy (which translates into reduced storage capacity), this combination has good dynamic performance, good safety, and greatly increased service life. Batteries of this type can accept more than 10,000 operating cycles at 100% depth of discharge, while other types of lithium batteries accept around 2,000 cycles.
- LiFePO4 batteries outperform lead-acid batteries with extremely high cycle stability, maximum energy density and minimal weight. If the battery is regularly discharged from 50% DOD and then fully charged, the LiFePO4 battery can perform up to 6,500 charge cycles. So, the extra investment pays off in the long run, and the price/performance ratio remains unbeatable. They are the preferred choice for continuous use as solar batteries.
- Performance: Charging and releasing the battery has a 98% total cycle effectiveness while being quickly charged and released in time frameworks of less than 2 hrs– and even faster for a decreased life.
- Storage capacity: a lithium iron phosphate battery packs can be over 18 kWh, which uses less space and weighs less than a lead-acid battery of the same capacity.
- Battery cost: Lithium iron phosphate tends to cost greater than lead-acid batteries, yet usually has a lower cycle cost as a result of greater longevity
The power storage market is growing fast – so it's hard for homeowners to keep track of it. While lead storage systems used to dominate due to their affordability, it's the durable and efficient lithium-ion storage systems that are now driving growth.
Since solar batteries are the most expensive part of residential solar batteries and new storage products are deviating from traditional off-grid designs, it is important to understand the various design options to meet customer expectations within the project budget. When researching options for your solar home battery storage system, there are many choices to consider, and the following are a few of the most common selection criteria：
- If you already have solar panels, choose a residential battery backup system and inverter of comparable power to it.
- If you intend to power even more of your home at once, look for a solar battery with a high-power ranking.
- Furthermore, some systems permit you to stack more than one unit to get the degree of back-up you need.
- If you want to power a much more energy-intensive device (like cooling or sump pumps that need more power to start up than as soon as they're running), seek a battery with a high instantaneous power rating.
- If you want to run your home with your solar battery for a much more extended quantity of time, try to find a battery with a greater useful ability.
- If you really feel that the price of lithium-ion solar batteries and inverters is out of your budget plan, you can look for all-in-one residence power storage space remedies, as well as usually they are more economical than batteries and inverters of the exact same capacity.
- If you intend to get one of the most out of every kilowatt-hour of electrical power you put into your battery, try to find batteries with a high roundtrip performance.
- If you are space-constrained and wish to get one of the most storage out of the least amount of area, look for lithium-ion LiFePo4 solar batteries.
- If you want a battery with one of the most extensive lives to cycle the most amount of times, seek lithium iron phosphate batteries.
- If you desire a battery with the absolute highest possible safety ranking possible, look for lithium iron phosphate batteries.
- If you want a home battery backup system with ensured high quality, seek a reliable house battery system provider or manufacturer.
- Since lithium-ion batteries should not be fully discharged, there are always two indications of their capacity. One is the nominal capacity, i.e., the usable storage capacity, and the actual storage capacity. The nominal capacity is decisive for the purchase.