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Quick Understanding of Characteristics and Parameters of Six Common Lithium Batteries (3/6)

Mar 13, 2019


Spinel lithium manganate batteries were first reported in 1983. In 1996, Moli Energy Company commercialized lithium-ion batteries using lithium manganate as cathode material. The structure forms a three-dimensional spinel structure, which can improve the ion flow on the electrode, thereby reducing the internal resistance and improving the current carrying capacity. Another advantage of spinel is its high thermal stability and safety, but its cycle and calendar life are limited.

Power is discharged at 20-30A current with moderate heat accumulation. Load pulses up to 50A1 seconds can also be applied. Continuous high load at this current will lead to heat accumulation, and the temperature of the battery should not exceed 80 C (176 F). Lithium manganate is used in electric tools, medical devices, and hybrid and pure electric vehicles.

Figure 4 illustrates the formation of a three-dimensional crystal skeleton on the cathode of a lithium manganate battery. The spinel structure is usually composed of a rhombic shape connected to the lattice, and usually occurs after the formation of batteries.

Figure 4: Lithium manganate structure.The crystallization of lithium manganate cathode has a three-dimensional skeleton structure formed after formation. Spinel provides low resistance but lower specific energy than  lithium cobalt.

The capacity of lithium manganate is about one third lower than that of lithium cobalt. Design flexibility allows engineers to choose to maximize battery life, or to increase maximum load current (specific power) or capacity (specific energy). For example, the long-life version of 18650 battery has a moderate capacity of only 1,100 mAh, while the high-capacity version has a moderate capacity of 1,500 mAh. Figure 5 shows a spider diagram of a typical lithium manganate battery. These characteristic parameters do not seem ideal, but the new design improves in power, safety and life. Pure lithium manganate batteries are no longer common today; they are only used in special situations.
Fig. 5: Spider diagram of pure lithium manganate battery.
Despite its general performance, the new lithium manganate design can improve power, safety and life.

Most lithium manganate is mixed with lithium nickel manganese cobalt oxide (NMC) to increase specific energy and prolong life. This combination brings the best performance of each system, and most electric vehicles, such as Nissan Leaf, Chevrolet Volt and BMW i3, use LMO (NMC). The LMO part of the battery can reach about 30% and provide higher current at acceleration, while the NMC part provides a long range.

Lithium-ion batteries tend to combine lithium manganate with cobalt, nickel, manganese and/or aluminium as active cathode materials. In some architectures, a small amount of silicon is added to the anode. This provides a 25% capacity increase; however, as silicon expands and shrinks during charging and discharging, it causes mechanical stress, which is usually closely related to short cycle life.

These three kinds of active metals and silicon reinforcement can be conveniently selected to improve specific energy (capacity), specific power (load capacity) or life. Consumer batteries need large capacity, while industrial applications need battery systems, which have good load capacity, long life and provide safe and reliable services.

Summary table

Lithium manganate oxide: LiMn2O4 cathode, graphite anode;

Abbreviation: LMO or Li-Mn (spinel structure) since 1996

3.70V(3.80V)3.0-4.2V  Voltage 3.70V (3.80V) nominal value; Typical operating range 3.0-4.2V/battery

Specific energy (capacity) 100-150 Wh/kg

Charging (C rate) typical value is 0.7-1C, maximum value is 3C, charging to 4.20V (most batteries)

Discharge (C rate) 1C; Some batteries can reach 10C, 30C pulse (5s), 2.50V cut-off.

Cycle Life 300-700 (Depending on Depth of Discharge and Temperature)

The typical value of thermal runaway is 250 degrees C (482 degrees F). High charge promotes thermal runaway

 Application of Electric Tools, Medical Equipment, Electric Power Transmission System

 Notes: High power but low capacity; safer than lithium cobalt; usually mixed with NMC to improve performance.