54 September/October 2025 | E-Mobility Engineering LFP batteries are made up from cells with LiFePO4 cathodes and graphite anodes. Specific energy is low to moderate at between 90 and 160 Wh/kg, and service life is good at 3000 to 6000 cycles. As well as a long life, they maintain performance at high temperatures and are inherently safer than NMC batteries thanks to their greater resistance to thermal runaway. Furthermore, as they don’t contain nickel or cobalt, they are also less expensive. However, having lower specific energy than NMC means that LFP batteries are heavier for a given capacity, and they are also slower to charge. NMC batteries are available with cells that have different proportions of nickel, manganese and cobalt in their cathodes, the main options being NMC 532, NMC 622 and NMC 811. The numbers represent the proportions of those elements in the cathode – NMC 532 cells have nickel, manganese and cobalt in the proportions of five to three to two, for example. The choice between them comes down to finding the best balance between energy density, cycle life, safety, charging rate and cost for each application. Specific energy ranges from around 160 to 250 Wh/kg. All other things being equal, NMC 532 offers the lowest specific energy of the three, the longest cycle life, the highest safety in terms of inherent thermal runaway resistance, the lowest maximum charge rates and the lowest cost. NMC 811 is at the other end of the scale in each of those categories, with NMC 622 essentially splitting the difference. In mining, the key trade-off is safety versus specific energy, with underground mines prioritising 532 or 622 batteries for their stability, while surface mines adopt 811 batteries for range and typically invest in very capable thermal management systems. In terms of total cost of ownership, 532s win thanks to their long cycle life – while 811s cost less per kilowatt-hour but need to be replaced more often. The other cell chemistry commonly used in mining is LTO, in which the anode material is Li4Ti5O12 (lithium titanate oxide) rather than the traditional graphite. Like other lithium-ion chemistries, the electrolyte is a lithium salt dissolved in an organic solvent. Cathodes normally use either LiMn2O4 (lithium manganese oxide) or lithium iron phosphate, so the batteries are generally free of nickel and cobalt. The specific energy of LTO batteries is low at around 60–100 Wh/kg, but the batteries are very long-lived, completing more than 20,000 cycles and lasting more than 20 years in some cases, longevity that offsets their high initial cost driven by the titanium content. LTO batteries work well in temperatures ranging from -30 to +60 C. Furthermore, they are very safe, remaining stable up to and beyond 300 C. Also, LTO batteries charge very quickly, achieving C rates of 10 or more (much higher than the 2–4C of NMC 811, for example), so a full charge can be achieved in minutes, making charging and swapping close in terms of time taken. Battery/supercap hybrid Another promising energy storage technology for mining is the Skeleton SuperBattery, which combines characteristics of graphene-based electric double-layer capacitors (also known as supercapacitors or ultracapacitors) with those of lithiumion batteries. The result is a hybrid storage device with modest specific energy that is about the same as that of an LTO battery at 60–100 Wh/kg, but with a specific power output of 10–20 kW/kg, a life of around 50,000 cycles, charging at rates of up to 60C, and no risk of thermal runaway. A SuperBattery can charge from zero to 80% in between 15 seconds and 2 minutes, and be fully charged in around 5 minutes. A SuperBattery has an anode made from curved graphene, a material that Skeleton compares to a sheet of paper This TH550B haul truck is using Sandvik’s battery AutoSwap system, which manages alignment with a sensor-based guidance system, secures electrical and coolant connections and assesses pack condition automatically (Image courtesy of Sandvik) Trolley systems draw power from overhead lines, supporting both diesel electric and battery electric vehicles, such as this Epiroc MT42 SG on sections of haul routes that demand the most power (Image courtesy of Epiroc)
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