SHINHOP laser

We often talk about ternary lithium batteries or iron lithium batteries, which are named according to the positive electrode active materials of lithium batteries. This article summarizes six common types of lithium batteries and their main performance parameters. As we all know, the specific parameters of battery cells with the same technical route are not completely identical, and the parameters shown in this article represent the general level of current parameters. The six types of lithium batteries specifically include:Lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese oxide (NCM), nickel cobalt aluminum oxide (NCA), lithium iron phosphate, lithium titanate.
1. Lithium Cobalt Oxide (LiCoO2)
Its high specific energy makes lithium cobalt oxide a popular choice for mobile phones, laptops, and digital cameras. The disadvantages of lithium cobalt oxide are its relatively short lifespan, low thermal stability, and limited load capacity (specific power). Like other cobalt mixed lithium-ion batteries, lithium cobalt oxide uses a graphite anode, and its cycle life is mainly limited by the solid electrolyte interface (SEI), which is mainly manifested in the gradual thickening of the SEI film and the lithium plating issue on the anode during fast charging or low-temperature charging processes. Newer material systems have increased nickel, manganese, and/or aluminum to improve lifespan, load capacity, and reduce costs.

The hexagonal spider chart summarizes the specific energy or capacity aspects of lithium cobalt oxide performance related to operation. Lithium cobalt oxide performs excellently in terms of high specific energy, but can only provide general performance in power characteristics, safety, and cycle life.

2. Lithium Manganese Oxide (LiMn2O4)
Spinel lithium manganese oxide batteries were first published in a materials research report in 1983. In 1996, Moli Energy Corporation commercialized lithium-ion batteries with lithium manganese oxide as the positive electrode material. This structure forms a three-dimensional spinel structure that improves ion flow on the electrode, thereby reducing internal resistance and improving current carrying capacity. Another advantage of spinel is its high thermal stability and improved safety, but its cycle and calendar life are limited.
Low internal resistance of the battery allows for fast charging and high current discharge. The 18650 type cell, lithium manganese oxide battery can discharge at currents of 20-30A and has moderate heat accumulation, with the battery temperature not exceeding 80°C. Lithium manganese oxide is used in power tools, medical devices, and hybrid and pure electric vehicles. The capacity of lithium manganese oxide is about one-third lower than that of lithium cobalt oxide. Design flexibility allows engineers to choose to maximize battery lifespan or increase maximum load current or capacity.
Figure 3 shows the spider chart of a typical lithium manganese oxide battery. These characteristic parameters may seem less than ideal, but new designs have improved power, safety, and lifespan. Pure lithium manganese oxide batteries are no longer common today; they are only applied in special cases.

Figure 3 Spider chart of pure lithium manganese oxide batteries
Most lithium manganese oxide is mixed with lithium nickel manganese cobalt oxide (NMC) to improve specific energy and extend lifespan. This combination brings optimal performance for each system, and most electric vehicles, such as the Nissan Leaf, Chevrolet Volt, and BMW i3, have chosen LMO (NMC). The LMO portion of the battery can reach about 30%, providing high current during acceleration; the NMC portion offers long range.
Lithium-ion battery research tends to combine lithium manganese oxide with cobalt, nickel, manganese, and/or aluminum as active positive electrode materials. In some architectures, a small amount of silicon is added to the anode. This provides a 25% capacity increase; however, silicon expands and contracts with charging and discharging, causing mechanical stress, and the capacity increase is often closely associated with a short cycle life.

Table 4 Characteristics of lithium manganese oxide
3. Nickel Cobalt Manganese Oxide (NMC)
One of the most successful lithium-ion systems is the positive electrode combination of nickel, manganese, and cobalt (NMC). Similar to lithium manganese oxide, this system can be customized for use as an energy battery or power battery. For example, under moderate load conditions, the NMC in the 18650 battery has a capacity of about 2,800mAh and can provide a discharge current of 4A to 5A; the same type of NMC optimized for specific power has a capacity of only 2,000mAh but can provide a continuous discharge current of 20A. Silicon-based anodes can reach over 4000mAh, but load capacity decreases and cycle life shortens. Silicon added to graphite has the drawback that the anode expands and contracts with charging and discharging, leading to significant mechanical stress and structural instability.
The secret of NMC lies in the combination of nickel and manganese. This is similar to table salt, where the main components sodium and chloride are toxic by themselves, but when mixed together, they serve as a seasoning and food preservative. Nickel is known for its high specific energy but has poor stability; manganese spinel structure can achieve low internal resistance but has lower specific energy. The advantages of the two active metals complement each other.
NMC is the preferred battery for power tools, electric bicycles, and other electric power systems. The positive electrode combination is typically one-third nickel, one-third manganese, and one-third cobalt, also known as 1-1-1. This provides a unique mixture that reduces raw material costs due to the lower cobalt content. Another successful combination is NCM, which contains 5 parts nickel, 3 parts cobalt, and 2 parts manganese (5-3-2). Other different combinations of positive electrode materials can also be used.
Due to the high cost of cobalt, battery manufacturers are shifting from cobalt-based to nickel-based positive electrodes. Nickel-based systems have higher energy density, lower costs, and longer cycle life than cobalt-based batteries, but their voltage is slightly lower. New electrolytes and additives can charge a single battery to over 4.4V, thereby increasing energy capacity. Figure 5 shows the characteristics of NMC.

Due to the economic and comprehensive performance of this system being relatively good, NMC mixed lithium-ion batteries are receiving increasing attention. The three active materials nickel, manganese, and cobalt can be easily mixed to adapt to the wide applications of automotive and energy storage systems that require frequent cycling. The diversity of the NMC family is growing.

Table 6 Characteristics of lithium nickel manganese cobalt oxide (NMC)
4. Lithium Iron Phosphate (LiFePO4)
In 1996, the University of Texas discovered that phosphates could be used as positive electrode materials for rechargeable lithium batteries. Lithium phosphate has good electrochemical performance and low resistance. This is achieved through nano-scale phosphate cathode materials. The main advantages are high rated current and long cycle life; good thermal stability enhances safety and tolerance to abuse.
If kept at high voltage for a long time, lithium iron phosphate has stronger tolerance to all charging conditions and experiences less stress than other lithium-ion systems. The downside is that the lower nominal voltage of the 3.2V battery results in lower energy density compared to cobalt-doped lithium-ion batteries. For most batteries, low temperatures reduce performance, and higher storage temperatures shorten lifespan, and lithium iron phosphate is no exception. Lithium iron phosphate has a higher self-discharge rate than other lithium-ion batteries, which may lead to aging and subsequently balancing issues. Although this can be compensated by selecting high-quality batteries or using advanced battery management systems, both methods increase the cost of the battery pack. Battery lifespan is very sensitive to impurities in the manufacturing process and cannot tolerate moisture contamination; due to the presence of moisture impurities, some batteries have a minimum lifespan of only 50 cycles. Figure 7 summarizes the properties of lithium iron phosphate.

Figure 7 Spider chart of typical lithium iron phosphate batteries
Commonly used lithium iron phosphate replaces lead-acid starter batteries. Four series-connected batteries produce 12.80V, similar to the voltage of six 2V lead-acid batteries connected in series. The vehicle charges the lead-acid battery to 14.40V (2.40V/battery) and maintains a float charge. The purpose of the float charge is to maintain a fully charged level and prevent sulfation of the lead-acid battery.
By connecting four lithium iron phosphate batteries in series, each with a voltage of 3.60V, this is the correct fully charged voltage. At this point, charging should be disconnected, but charging continues while driving. Lithium iron phosphate tolerates some overcharging; however, since most vehicles maintain a voltage of 14.40V for extended periods during long trips, it may increase mechanical stress on the lithium iron phosphate battery. Time will tell how long lithium iron phosphate can withstand overcharging as a replacement for lead-acid batteries. Low temperatures will also reduce lithium ion performance, which may affect starting ability in extreme conditions.

Table 8 Properties of lithium iron phosphate
5. Nickel Cobalt Aluminum Lithium (NCA)
Nickel cobalt aluminum lithium batteries, or NCA, have been in use since 1999. They have a high specific energy, relatively good specific power, and long lifespan, similar to NMC. Less favorable are safety and cost. Figure 9 summarizes six key features.

Figure 9 Spider chart of NCA
NCA is a further development of lithium nickel oxide; the addition of aluminum gives the battery better chemical stability. High energy and power density, along with good lifespan, make NCA a candidate for EV power systems. However, high cost and marginal safety have negative impacts.

Table 10 Properties of Nickel Cobalt Aluminum Lithium (NCA)
6. Lithium Titanate
Since the 1980s, lithium titanate anode batteries have been known. Lithium titanate replaces graphite in typical lithium-ion battery anodes, and the material forms a spinel structure. The cathode can be lithium manganese oxide or NMC. The nominal battery voltage of lithium titanate is 2.40V, it can be charged quickly, and provides a high discharge current of 10C. It is said to have a cycle life higher than that of conventional lithium-ion batteries. Lithium titanate is safe, with excellent low-temperature discharge characteristics, achieving 80% capacity at -30°C (-22°F).

Figure 11 Spider chart of lithium titanate
LTO (usually Li4Ti5O12) has zero strain, no SEI film formation, and no lithium plating during fast charging and low-temperature charging, thus exhibiting superior charge and discharge performance compared to traditional cobalt-doped Li-ion and graphite anodes. Thermal stability at high temperatures is also better than that of other lithium-ion systems; however, the battery is expensive. The specific energy is low, only 65Wh/kg, comparable to NiCd. Lithium titanate is charged to 2.80V and discharged to 1.80V. Figure 13 shows the characteristics of lithium titanate batteries. Typical applications include electric drive systems, UPS, and solar street lights.