Toshiba equips electric bus with niobium-titanate cells

NTO anode for extremely fast charging and long service life - with low energy density

Toshiba, Sojitz and CBMM developed an extremely fast-charging electric bus with NTO anodes

By: Stefan Leichsenring

Published by: Brian Potter

Jul 8, 2024 at 5:43am ET

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Lithium titanate? Does that mean anything to you? We had to look it up first. The material, also known as lithium titanium oxide or LTO, is used as an alternative to graphite at the anode. It is said to ensure significantly higher charging speeds.

Toshiba has already presented such cells in 2022 - the trade name is Super Charge Ion Battery (SCiB). Under the designation SCiB Nb, there is now also a variant with niobium titanate (NTO), which, according to Toshiba, should have a volumetric energy density three times greater than LTO. The advantages of LTO technology - high charge rates and long shelf life - are to be retained. Such SCiB-Nb cells have now been installed in an electric bus.

Toshiba claims that the battery can be charged extremely quickly with around 10 minutes being enough. Toshiba also promises a high energy density.

An SCiB Nb cell from Toshiba

The bus prototype is intended to provide data on the properties of the NTO battery. It was developed by Volkswagen Truck & Bus Brazil, a pioneer in the development and production of electric commercial vehicles. The vehicle is being used as a demonstrator at the plant of Companhia Brasileira de Metalurgia e Mineração (CBMM) in Araxá, Brazil. CBMM is the world's largest producer of niobium; in Aeraxá, the metal is extracted from a mineral called pyrochlore (Ca2Nb2O7).

The Sojitz Corporation, a CBMM shareholder and wholesaler from Japan, is also involved. The company wants to establish a global supply chain for the cells. Together, the three companies want to launch the lithium-ion cells with NTO anode on the global market in spring 2025. The batteries will be used primarily in electric commercial vehicles.

Wikipedia has a separate entry on LTO batteries. It states that the stronger chemical bond of the lithium in the titanate prevents the formation of an insulating surface layer on the electrode. This solid electrolyte interface (SEI) is one of the main reasons for ageing in graphite anodes. LTO cells are also considered to be particularly safe. A disadvantage is the lower voltage as it is only around 2.4 volts instead of 3.6 volts for normal lithium-ion cells. This results in a lower energy density. Nevertheless, LTO cells are used in the Japanese i-MiEV, among others. NTO cells are also mentioned as these are used in battery electric trains of the Siemens Mireo Plus B type (Wikipedia).

To explore the potential of NTO, Toshiba, CBMM and Sojitz signed a cooperation agreement in June 2018. In September 2021, this was extended to include series production processes, and in August 2023, a sales and marketing cooperation was also agreed.

According to the Toshiba website for the SCiB Nb cells, the cells have the following technical data

Storage capacity: 50 ampere hours (Ah)
Nominal voltage: 2.3 volts
Max. Power output: 1000 watts (at SoC 50% and 25 degrees Celsius for 10 seconds)
Max. Power consumption: 2000 watts (at SoC 50% and 25 degrees Celsius for 10 seconds)
Volumetric energy density: 350 watt hours per litre (307 Wh/L with tab and seal)
Gravimetric energy density: 130 Wh/kg
Dimensions: 98 x 280 x 12 mm (102 x 310 x 12 mm with tab and seal)
Weight: approx. 860 grams
Fast charge rate: 5C (in 10min. to 80% SoC)
Operating temperature: -30 to +60 degrees Celsius

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The bottom line

Depending on the variant, nickel-manganese-nickel oxides (NMC), nickel-cobalt-aluminium oxides (NCA) or lithium iron phosphate (LFP) are used at the cathode of lithium-ion cells. Graphite is traditionally used as the anode, sometimes mixed with silicon in the one per cent range. In addition to silicon, lithium titanate (LTO) and niobium titanate (NTO) are considered the most promising materials for the anode. This chemistry is being promoted by Toshiba; it is particularly suitable for commercial vehicles and other applications where extremely fast charging and long service life are more important than energy density.

Source: Toshiba via InsideEVs.com

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