Toshiba Develops Lithium-ion Battery with Energy Density Comparable to LFP Battery, Super-Rapid Charging and Long-Life Performance

Toshiba Corporation continues to promote innovation in lithium-ion batteries with the development of a battery with a niobium titanium oxide (NTO) anode that delivers volumetric energy density^*1 comparable to that of widely used lithium iron phosphate (LFP) batteries^*2, and that also achieves a charge-discharge cycle life over 10 times that of LFP. The new NTO battery combines this excellent performance with super-rapid charging and a long life that is suitable for large commercial vehicles, such as buses and trucks. Behind this achievement is Toshiba’s success in uniformly dispersing nano-level conductive agents on the surface of NTO particles, and forming a strong conductive network between particles to achieve marked improvements in energy density, lifespan and charging.

The NTO battery can be charged to approximately 70% of full capacity in five minutes, and maintain a charge capacity of over 80% even after more than 15,000 cycles of super-rapid charging and discharging (Figure 1). It can also perform super-rapid charging in harsh environments ranging from -30°C to 60°C, with a very low risk of lithium deposition, making it highly reliable and safe for use in extreme temperatures. Given the high utilization rate and harsh external temperatures commercial vehicles often operate in, the battery's super-rapid charging, long life performance, high level safety, and reliability make it ideal for electrification of large commercial vehicles. Additionally, the ability to repeatedly perform super-rapid charging allows for a reduction in battery capacity, significantly reducing the need for battery replacement and lowering both initial and operational costs for commercial EVs, thereby reducing the total cost of ownership (TCO).

In 2017, Toshiba successfully prototyped a next-generation lithium-ion battery with an NTO anode, and in 2018, the company entered into a joint development agreement with Brazil’s CBMM and Japan’s Sojitz Corporation on commercialization of the battery. Since June this year, the three companies have carrying out demonstration operations at CBMM’s industrial plant in Araxá, Brazil^*3, using an e-bus powered by the battery.

The electrification of mobility is essential for a carbon-neutral society. Efforts in this area have focused on passenger EV, the largest market, where advances in battery capacity have extended range per charge, and parts standardization has cut initial costs. The focus is now widening use to include commercial EV, a sector where many challenges have to be overcome to secure greater adoption.

Commercial vehicles have a higher utilization rate than private cars, and improving utilization requires efficient charging and a sufficient driving range per charge. To enhance charging efficiency, super-rapid charging and long-life performance with minimal degradation after repeated charging and discharging are crucial. While LFP batteries are widely used in passenger EVs, commercial EVs require higher long-life performance in addition to super-rapid charging. The driving range can be increased by installing more batteries, but this reduces passenger or cargo space and increases vehicle weight, reducing energy efficiency. It is essential to improve the volumetric energy density of batteries and to plan efficient charging cycles with minimal battery capacity.

Commercial EVs often operate in harsh external temperature conditions and need highly durable batteries. In low-temperature environments, battery input/output performance falls off, leading to shorter ranges and longer charging times. In high-temperature environments, side reactions in battery materials can cause gas generation and battery swelling, leading to degradation issues.

A well-known cause of degraded performance in lithium-ion batteries is lithium deposition on the anode. The NTO anode eradicates this problem to deliver volumetric energy density comparable to LFP batteries, and over 10 times the number of super-rapid recharge cycles. It also realizes a long life with marginal degradation, even after repeated charging and discharging, and stability in both low and high temperature conditions. These are all characteristics that make it highly suitable for commercial EVs. A further important advantage is its high thermal stability: battery temperatures generally rise during rapid recharging, but the NTO anode continues fast recharging even when the battery is hot.

The NTO particles that form the NTO anode act as non-electric conductors when discharged, so construction of an efficient conductive network for carrying electrons to the particles is an effective way to realize super-rapid charging and a long life. Toshiba recently developed an electrode manufacturing technology that deposits a highly uniform, nano-level conductive agent on the surface of particles, forming a strong conductive network between them (Figure 2).

Figure 2: Electrode manufacturing technology that forms a strong conductive network
between particles and the manufactured electrode

In the past, a large volume of the conductive agent was required, which led to reduced energy density and lifespan, due to side reactions between the conductive agent and battery electrolyte. However, Toshiba’s technology forms a conductive network with only a small amount of conductive agent, achieving improvements in energy density and lifespan while maintaining high safety and achieving high input/output performance.

Cycle tests that simulated the operation of a shuttle bus subjected a large, 50 Ah capacity NTO battery cell to repeated super-rapid charging and discharging^*4. It found that the cell maintained over 93% of its capacity after 7,000 cycles^*5. The estimated number of cycles for super-rapid charging is over 15,000, allowing for more than 15 years (equivalent to 1.5 million km) of use under harsh operating conditions, with 2-3 super-rapid charges per day, without any need for battery replacement, enabling continuous use until vehicle retirement. The use of super-rapid recharging, allowing multiple recharges during operation, cuts the number of batteries the vehicle requires, which reduces the initial cost, while the associated weight reduction cuts electricity consumption and running costs. Since both initial and operating costs can be cut, a lower TCO can be expected.

Battery safety was confirmed with a nail penetration test^*6 to see if an internal short circuit resulting in smoking or combustion. It found that the battery cell is highly safe (EUCAR hazard level 3). Other tests confirmed that it can be quickly and repeatedly charged and discharged, even in severe temperatures as low as -30°C and as high as 60°C, since lithium deposition does not occur.

Through the ongoing demonstration operation with CBMM and Sojitz since June, Toshiba continues to collect data on the characteristics of next-generation lithium-ion batteries using NTO and vehicle operation data, advancing efforts towards commercialization.

• The amount of energy stored per unit volume
• Toshiba comparison during partial charge and discharge cycles (not full charge and discharge, but within a certain capacity range) assuming super-rapid charging cycles.
• https://www.global.toshiba/ww/news/corporate/2024/06/news-20240620-01.html
• Cycle test conducted under 3C charging conditions (charging 3C/discharging 1C cycle) with repeated super-rapid charging and discharging. C represents the ratio of the charge/discharge current value to the battery capacity. 1C represents the current value when the battery is fully discharged from a fully charged state in one hour.
• Capacity retention rate based on 0.2C discharge capacity obtained every 200 cycles.
• Nail penetration test in accordance with SAE J 2464.