Lithium manganate (LiMn2O4)

　　The spinel lithium manganate battery was first published in the material research report in 1983. In 1996, Moli Energy Company commercialized lithium ion batteries with 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 improved safety, but its cycle and calendar life are limited.

　　Low battery internal resistance can realize fast charging and high current discharge. 18650 type battery cell, lithium manganate battery can discharge under 20-30A current, and has moderate heat accumulation. The battery temperature cannot exceed 80 ° C. Lithium manganate is used in electric tools, medical devices, and hybrid and pure electric vehicles. The capacity of lithium manganate is about one third lower than that of lithium cobalate. Design flexibility allows engineers to choose to maximize battery life or increase maximum load current or capacity.

　　Figure 3 shows the spider diagram of a typical lithium manganate battery. These characteristic parameters seem not ideal, but the new design has improved in power, safety and life. Pure lithium manganate batteries are no longer common today; They are only used in special cases.

　　Most lithium manganate is mixed with lithium nickel manganese cobalt oxide (NMC) to increase the specific energy and prolong the service 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%, which can provide high current during acceleration; The NMC part provides a long range.

　　Lithium ion battery research tends to combine lithium manganate with cobalt, nickel, manganese and/or aluminum as active cathode materials. In some architectures, a small amount of silicon is added to the negative electrode. This provides a 25% capacity increase; However, silicon expands and contracts with charging and discharging, resulting in mechanical stress. Capacity increase is usually closely related to short cycle life.

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