Next-generation batteries options: storage battery technologies for automotive applications
From technical presentations and exhibits at Battery Japan 2019
The 10th International Rechargeable Battery Expo (BATTERY JAPAN), as part of the Smart Energy Week 2019 organized by Reed Exhibition Japan, was held from February 27 ~ March 1, 2019 at the Tokyo Big Sight exhibition center, which showcased a multitude of storage battery technologies for consumer, industrial and energy infrastructure applications.
|Major exhibitors at the BATTERY JAPAN 2019
（all photo images were taken by the author）
Rechargeable battery options for automotive applications in Japan are still few in comparison to those for mobile phone and PC applications, and batteries for HEV/EV applications are exclusively sourced from suppliers by automakers. This year’s exhibition did not strongly target batteries for automotive applications. Regardless, a number of the battery technologies exhibited have long been considered for automotive applications. This report addresses the current state of storage battery technologies exhibited.
EV and FCV Components exhibited during World Smart Energy Week 2019 （Mar. 2019）
Tesla Model 3 Teardown: Motor, Inverter, and Battery （Mar. 2019）
Nissan LEAF Teardown: Lithium-ion battery pack structure （Nov. 2018）
EVs and the next-generation batteries
The selection of storage battery types affects the popularization and practical usability of EVs. In the ongoing debate on next generation lithium-ion batteries, which is currently the mainstream technology, the first on the list of requirements cited by every technical paper or information source is “safety”.
For storage batteries that were exhibited at this year’s expo, the battery types that have been used for EV studies and trials are listed in the table below.
Overview of storage batteries for EVs
|Battery classification||Experience on passenger car applications||Links to articles|
|Major classification*||Sub-classification||Minor classification||(Note)||Battery manufacturer|
|Primary Battery||Metal-air battery||Mg-Air||△||Fujikura Rubber||◆Magnesium-air battery|
|Secondary Battery||Lead-acid battery||Electrolyte replenishable (JIS-NL series)||◎||Multiple suppliers||◆Lead-acid batteries: Furukawa Battery|
|Lithium-ion battery||Ternary type positive electrode||◎||Multiple suppliers||◆Lithium-ion batteries (electrolyte type)|
|Iron phosphate positive electrode (cathode)||◎||Multiple suppliers|
|Lithium titanate negative electrode (anode)||◎||Toshiba|
|All-solid-state battery||Oxide-based||〇||－||◆All-solid state lithium-ion battery|
|Sodium-sulfur battery||〇||ABB||◆NaS (Sodium Sulfur) battery|
|Redox flow battery||〇||Sumitomo Electric
||◆Redox flow batteries|
|* Primary batteries are non-rechargeable, secondary batteries are rechargeable|| (Note)
◎ Adopted for mass production
〇 Various Prototypes
△ Experimental trials
Major manufacturers of lithium-ion battery for automotive applications such as BYD, CATL, LG Chem, and Panasonic did not exhibit at this year’s event. Regarding all solid-state batteries, there were no exhibitions from manufacturers such TDK, Murata Seisakusho, Toyota and Sakti3 (acquired by Dyson to enter the EV market) but there were many exhibitions by other manufacturers. Below is the list of battery manufacturers visited for this report.
Overview of storage battery manufacturer exhibitions
|Exhibitor name||Exhibit/technical presentation/exhibition name||Overview|
|Hitachi Zosen||Development of sulfide-based and all-solid state batteries BATTERY JAPAN||Very close in commercializing sulfide-based batteries|
|FDK||Development of oxide-based all-solid state battery BATTERY JAPAN||Aims to commercialize oxide-based batteries with high energy density in 2020s|
|DARE Japan||Development of oxide-based all-solid state battery BATTERY JAPAN||Oxide-based battery for automotive applications to be produced in Japan (plan)|
|Murata Manufacturing||Future roadmap of lithium-ion battery SMART GRID EXPO||Battery as core business inheriting Sony’s technology|
|LG Chem (Korea)
Energy Solution Company
|Performance improvements in lithium-ion battery BATTERY JAPAN (presentation)||Mainstream ternary-type Ni-rich cathode and Si-based anode|
|Fujikura Rubber||Introduction of Mg-Air battery BATTERY JAPAN||Successful test drive conducted with Tamagawa University|
|NGK Insulators||Current status of expansion of sodium sulfur battery SMART GRID EXPO||Sole supplier of mass-production NaS battery|
|Sumitomo Electric||Advantages of redox flow battery SMART GRID EXPO||Promoting development of alternatives for scarce Vanadium|
|Furukawa Battery||Trends in lead-acid battery, Mg-air battery BATTERY JAPAN||Pursuit of long life lead-acid battery|
All-solid state lithium-ion battery: Hitachi Zosen, FDK, DARE
The “solid-state” part of the all solid-state lithium-ion battery is composed of sulfides, oxides, and plastics. Oxide compounds are used for small parts mounted on electronic printed boards while sulfide types are used for high power applications. In the all solid-state battery development project sponsored by NEDO, the roadmap in Fig 1 is presented (announced in June 2018). Plastics will need to be developed as the technologies evolve.
|Figure 1 Forecast of battery technology shift for EVs|
Source: NEDO News release 2018/6/15
Sulfide-based electrolytes are not ideal in terms of “safety” due to their toxicity and flammability. However, due to their energy density and quick charging excellent properties, they are attractive in the transitional phase. On the other hand, there are issues with oxide-based electrolytes. For automotive applications the brittleness of ceramics is well known to result in cracking. Small batteries built into electronic devices may not be of much concern, but for large scale devices it is important to ensure that the batteries can can withstand breakage.
Hitachi Zosen: The supplier closest to the mass-production of sulfide-based cells?
Hitachi Zosen plans to mass produce sulfide-based batteries under the AS-LiB brand name. The development of electrolyte is jointly conducted with a materials manufacturer, leveraging Hitachi’s unique strengths in processing technologies (likely its press forming technology). According to reports, its production system will likely be completed in 2019, but will initially be used for aerospace, medical, and industrial applications. As its booth staff explained, the company is targeting the launch of these batteries for automotive applications in 2025.
External features, dimensions: refer to Picture 1
Cell voltage: 4.5 (max) ~ 2.7V (at rated current)
Cell discharge current: 0.14A (1C rate)
Cell rated capacity: 140mAh
|Picture 1 Dimensions of product exhibit: 52 x 65.5 x 2.7mm, weight 25g|
FDK: Targeting to launch high-energy density cathode materials in 2020
The company is planning to use and electrode material with a standard potential of 5V (typically 3.2~4V for Lithium Ion batteries), with the expectation of realizing a high energy battery. The display sample had a nominal voltage of 3V (a maximum value among oxide-based batteries) with a capacity of 140 μAh.
|Picture 2 High-voltage potential materials for positive electrodes||Picture 3 Applications for backup power of printed board mounted devices|
Sanyo Electric’s battery division was broken up and sold, with Panasonic acquiring batteries for automotive applications, and FDK for non-automotive applications. FDK does not plan to enter the automotive market.
DARE Japan: Manufacturing automotive-grade oxide-based all solid-state battery in Japan (plan)
|Picture 4 Cell prototype|
DARE is a Chinese company headquartered in Shanghai. Although not a battery manufacturer, the company is applying its semiconductor materials and manufacturing technology expertise to embark upon the development of oxide-type all-solid-state batteries. The company foresees being able to market large-scale batteries for automobiles and is planning to go into pilot production in the early 2020s with its Japan subsidiary. The company is conducting early development and production of oxide-based electrolytes for all solid-state batteries and aims to mass produce and sell within Japan and overseas after 2022, and supply worldwide to user companies beyond 2024.
Lithium-ion batteries (electrolyte type): Murata Manufacturing, LG Chem
Lithium-ion batteries are most often used for storage batteries, are produced by many manufacturers, and are continuously being improved from a cost and performance perspective. Besides the companies introduced below, there were exhibitions from ELIIY Power, FDK, Furukawa Battery (reported in the lead-acid battery section), GS Yuasa, Sekisui Chemicals, and many manufacturers from neighboring countries.
Murata Manufacturing: inheriting Sony’s technology making battery its core business (Lithium Ion, all-solid state)
|Picture 5 External features of FORTELION (Source: Murata Manufacturing catalogue)|
The main objective of its absorbing Sony’s battery division in 2017 was to acquire its all solid-state battery technology and cylindrical olivine-type iron phosphate Li-ion battery technology. Even before the buyout, Murata had developed the olivine-type Li-ion battery, which did not go into mass production (for automotive applications), and the company has been using Sony’s proven technology and production infrastructure since 2009. The company will focus on selling the olivine-type FORTELION for industrial applications. The registered trademark used is based on Sony’s trademark. The company says that it “continues to conduct R&D” on laminate type cells.
LG Chem： uses the mainstream Ni-rich ternary-type for cathodes, Si-based for anodes (abstract from the presentation)
LG Chem is the world’s No. 1 automotive battery supplier (according to LG Chem’s website) and its products have been adopted on many new and advanced models of western automakers. During the presentation, the company introduced the latest improvements incorporated into its new products.
LG Chem’s batteries are the most trusted by automakers and have been adopted on the latest state-of-the-art EVs such as Audi’s e-tron and Jaguar’s i-Pace. The current product achieves a range of 300 miles, charges to 80% within 30 minutes, and has a product life of 10 years or 150,000 miles (residual capacity of 70% or more).
Improvements to the laminate-type cell are based on latest technologies, as follows:
Cathode (positive electrode) material made of ternary compounds reduces Co and using Ni-rich materials achieves significant cost reduction
The material is composed of more than 80% Ni (nickel) and less than 5% Co (cobalt). Conventionally, the composition is 60% and 20% respectively. The thermal stability of the cathode was achieved by coating the material and reducing volume changes. This lowered material costs by 11~26%
Anode (negative electrode) has a unique composition by adding Si to graphite
By adding a Si (silicon)-based compound (SixMnOz), the amount of Lithium absorption between the anode layers increases dramatically resulting in increased capacity. And the problem of initial characteristic fluctuations was improved. The carbon component has a highly conductive nanotube configuration.
|Figure 2 Cathode structure||Figure 3 Anode structure|
Source: LG Chem homepage
Improvements of the SRS (trademark) separator since 2007
The company’s original separator was called the Safety Reinforced Separator (SRS), due to its adaptability to a Ni-rich (nickel) cathode in addition to its traditional porous polyolefin main layer to ensure thermal stability with the addition of a flame-retardant ceramic coating layer.
Electrolytes with additives reduced resistance (Ni-rich applications)
Based on these improvements, further performance improvements were made on the next generation cells such as increased energy density (570 -> 670 Wh/L, 250 -> 295 Wh/kg), reduced charging time by half, and a longer service life. The cooling method for the module was also changed from side cooling to bottom cooling (Note 1) which achieved a space savings by eliminating the gaps between cells.
(Note 1) The gap was eliminated by not placing a cooling mechanism on the laminate cell surface, and transferring heat by direct contact with the thermal resin.
Magnesium-air battery: Fujikura Rubber
Since the air battery takes in oxygen, which is a positive electrode active material, from the surrounding atmosphere, the separator and the space on the cathode side are not necessary, and the size can be considerably reduced. Furthermore, by replacing Mg (Magnesium) and Li (Lithium), it is a promising technology that can further improve energy density.
Originally, primary batteries were not considered for automotive applications but can be used as “replaceable battery-type power supply”. Furthermore, for Mg-air batteries, electric power can be generated by replenishing water and stockpiling these batteries in a warehouse to act as a power supply station. At the exhibition, Fujikura Rubber and Furukawa Electric exhibited nearly compatible products (please refer to the list below).
|Mg-air battery specifications comparison
(Source: extracted from manufacturer catalogs)
|Figure 4 Principle of Mg-air battery
(Source: Fujikura Rubber homepage)
Fujikura Rubber: Successful vehicle testing conducted jointly with Tamagawa University
The battery product is intended to supply power to mobile telephone devices during disasters, and Fujikura Rubber has successfully conducted joint EV test drives with Tamagawa University for the purpose of expand its fields of application in the future. The test vehicle was displayed at the exhibition booth. The vehicle is 2.3m long,1.3m wide, weighs 460kg, can carry 2 persons powered by a 4kW drive motor.
|Picture 6 Fujikura Rubber battery product and container||Picture Prototype vehicle used for actual drive tests|
NaS (Sodium Sulfur) battery：NGK Insulators Ltd.
The battery has a simple structure using S (sulfur) for the cathode chamber and Na (sodium) for the anode chamber, and a solid electrolyte (the same as the electrolyte layer of an all solid-state battery) between the electrodes but requires heating and insulation due to its high operating temperature of 300degC. The basic principle was first published by Ford and development was advanced in the 1990s, including 3 German OEMs. Although it was disregarded for automotive use because it has less no advantage over the lithium-ion battery, but an advantage is that it does not use scarce resources. Regarding safety, there is the risk of fire due to high temperature operation with Na (sodium), but NGK’s improvement efforts have resulted in an increase in the use of its stationary power storage sources both in Japan and overseas.
NGK Insulators: Sole supplier of commercialized NAS battery (NAS is a registered trademark)
In the 1990s, NGK Insulators worked on the introduction of ABB-made NaS battery into the Japan market, and since 2002 has been struggling to improve and disseminate the technology in partnership with Tokyo Electric Power Co (TEPCO) as the sole supplier of NaS batteries. At the exhibition, NGK displayed a large logo of NAS exhibiting it as the flagship product.
|Picture 8 NGK showcases its NAS battery inside the rounded booth area||Picture 9 Example of NaS battery equipped cars in the 1990s (Note 2)|
(Note 2) In the Electric Jetta, a total of 360 ABB-made 2V cells using β alumina (oxide-type solid electrolyte) with 90 cells is arranged in series in 4 parallel rows. The capacity is 22kWh and the pack weighs 276kg.
At the booth, it was explained that the cause of fires in the past were caused by short circuiting and fusing due to foreign contaminants inside the battery. Since then, improvements were made such as revising manufacturing quality standards and designing structures that prevent the spread of fire to other cells. Along with battery monitoring and control technologies developed with Li-ion batteries, the safety level is comparable to that of Li-ion batteries.
Redox flow batteries: Sumitomo Electric
Electromotive force is generated between electrodes when two types of Vanadium aqueous solutions with different ionic valence numbers (V2+ ←→ V3+ and V4+ ←→ V5+) are partitioned by ion exchange membrane separators and electrodes are placing into each solution. The cells are comprised of the two electrolyte solutions and a separator placed within a container. By supplying each electrolyte solution to each cell from a common supply tank, a battery with a capacity corresponding to the tank volume can be configured. The circulation of fluid between the tank and cells is done with a pump. The battery operates at room temperature and because the fluid is inflammable, the product is the safest among the batteries presented in this report. On the other hand, a large volume tank is required, and the energy density is low.
Sumitomo Electric: promotes development of alternative materials to scarce Vanadium
|Picture 10 Sumitomo Electric’s Redox Flow Battery exhibit|
At the exhibit booth, examples of stationary power systems installed in Japan, the U.S., and Taiwan were displayed to emphasize that this battery is in the process of becoming popular. When asked, the booth staff replied that in the future, that due its large size, if the number of suppliers in the world increases there could be a problem with the supply of vanadium. Therefore, they also see the importance of developing non-Vanadium materials from a material cost viewpoint.
At Sumitomo Electric, batteries of this size are thought to be not suitable for automotive applications and that the nanoFlowcell (Note 3) being proposed for EV applications, in their opinion should be viewed as an “unbelievable challenge”
(Note 3) nanoFlowcell is a brand name of a redox flow battery supplied by a company with the same name and is conducting test drives and has already received back orders exceeding 25,000 units. This vehicle adopts low voltage and redox flow battery for “absolute safety” and runs at 48V, combining a special 48-phase motor and distribution cable.
Furukawa Battery: The pursuit of long-life lead-acid storage batteries
|Picture 11 Furukawa Battery’s exhibition booth|
The lead-acid battery has a very old history, and still plays a leading role. It has an electromotive force of approximately 2V per cell, which significantly exceeds the capacity of Nickel-Metal Hydride (NiMH) batteries. Furthermore, it’s the cost is extremely low, and the aqueous electrolyte is also very competitive in terms of safety. The proposal at Furukawa Battery’s booth displayed a large sign with the message “Do you know how amazing lead-acid batteries are?” was worth seeing.
Furukawa Battery: The pursuit of long-life lead-acid storage batteries
The lead-acid battery display by Furukawa Battery was for large-scale power storage applications that has achieved a service life of 20 years (5,500 cycles). Lead-acid batteries originally had a long expected service life. By adopting methods to further improve the durability of the electrode plates and terminal sealing parts, state-of-charge monitoring and control with the Battery Management Unit to inhibit sulfation, it was explained that a 20-year expected service life has been achieved. We were told that batteries used for automotive applications that are currently circulating in the market do not have this kind of long service life because there has been “no request from automakers”. The reason behind not having this type of request is assumed to be due to considerations for the aftermarket parts business (if the frequency of battery replacement goes down, the market scale of parts distribution and maintenance will shrink). On the other hand, there is a strong demand for non-fully sealed replenishable European-types (Battery Association Standard LN series) and major automakers are in the process of sequentially switching to this type.
Furukawa Battery is also working on Li-ion batteries that have been adopted on space probes such as the asteroid explorer “HAYABUSA” and the Venus explorer “AKATSUKI”. Although it is claimed (by Hitachi Zosen) that all solid-state batteries are advantageous for aerospace applications, the exhibited example can withstand vacuum conditions with liquid electrolyte and square winding-type (uses hermetic sealing for electrode seals different from land-based applications). It was indicated that “there is“ a plan to expand into the consumer market, but it looks like the due to constraints in production facilities, it is likely to adopt the laminate-type cells.
|Picture 12 External features of the lead-acid battery with a 20-year service life||Picture 13 Li-ion battery for aerospace applications|
Electric, EV, Battery, storage battery, solid battery, lithium ion battery, magnesium air battery, sodium sulfur battery, redox flow battery, lead battery, cathode, anode, separator, electrolyte, Hitachi Zosen, FDK, DARE, Murata Manufacturing, LG Chem, Fujikura Rubber, NGK Insulators, Sumitomo Electric Industries, Furukawa Battery
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