Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)
6Development of Large High-performance Lithium-ion
Batteries for Power Storage and Industrial Use

DAISUKE MUKAI*1

KATSUAKI KOBAYASHI*2

TOMOYOSHI KURAHASHI*1 NAOTO MATSUEDA*1

KATSUO HASHIZAKI*3

MASANORI KOGURE*3

Mitsubishi Heavy Industries, Ltd. (MHI) has developed large high-performance lithium-ion
batteries (50-Ah class P140 and 20-Ah class P060 batteries) for power storage and industrial use.
These batteries have high capacities and power combined with long lives. They were developed byoptimizing an original combination of the electrode elements, such as the positive and negativeelectrode materials, the separator, and the electrolyte. Additionally, the battery structure, namely
the electrode shape, current collecting structure, outer package, and the manufacturing processes
and methods, such as slurry mixing, battery assembly, and inspection, were also optimized.
Currently, the 50-Ah class P140 battery is in the production phase for supply to the market. This
report will describe the characteristics of our large lithium-ion batteries and their applications
currently in development.

|1. Introduction
The lithium-ion batteries used as power sources for communication devices, such as cell
phones and PCs, require further reduction in size and weight, and increased capacity. Moreover,there is an increasing market share for storage batteries for environmentally friendly electricvehicles to reduce carbon dioxide emissions. Research and development work, as well asverification tests, on power storage and load stabilization for battery applications in renewableenergy systems, such as wind-farm and mega-solar power generation, are gaining social attention.
In view of this, Mitsubishi Heavy Industries, Ltd. (MHI) has developed and commercialized
lithium-ion batteries for electric automobiles, industrial vehicles, and hybrid drives, and also for a
described above power storage and load stabilization facility for stationary use. MHI completed theconstruction of a verification plant for mass production at the Nagasaki Shipyard and Machinery
Works in November 2010, and started battery production for various purposes. We are expecting agrowing market through economical prices and performance. In this report, the features,specifications, and performance of the currently produced 50-Ah class P140 battery (hereinaftercalled the P140 battery) for power storage and industrial use, and the 20-Ah class P060 battery(hereinafter called the P060 battery) are presented.

|2. Features of lithium-ion battery
2.1

General features

A lithium-ion battery, compared to other room-temperature operating batteries (i.e., lead,nickel-cadmium, and nickel-metal hydride rechargeable batteries), has the general characteristics
listed below:(1) Lightweight and compact in size with a high energy density, (2) Rapidcharging/discharging with high charging/discharging efficiencies attained with low internal
resistance, (3) No memory effect, and (4) Long life.
*1

New Energy Systems Department, Power Systems*2Nagasaki Research and Development Center, Technology & Innovation Headquarters*3

Manager, Joint Lithium Battery Operations Department

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)7

Because of these features, coming from previously, lithium-ion batteries have been widelyused in home appliances, such as portable terminal equipment, which is small in size and requires
longer operating hours.

2.2Features of MHI’s lithium-ion batteryIn keeping with the advantageous features described above, our lithium-ion batteries weredesigned with our original electrode materials, a new battery construction, and specific parts
development to ensure their performance, safety, and reliability for power storage and industrialuse. The characteristics of our battery design and its properties are described below.
(1) Battery electrode material
A lithium compound oxide, that was selected and combined with the proper transition
elements, such as nickel, manganese, and cobalt for active metals, was selected for the positiveelectrode material. The optimization of the negative electrode utilized a natural graphite base,high-strength separator, electrolyte, and electrolyte additives to attain high voltage and highcapacity, a high energy density to volume and weight, a high charge/discharge rate, and longlife.
(2) Electrode structure
The flat-plate stacked structure of the electrode achieved high charge/discharge rates,
long life, and a high-level of safety by eliminating the stress difference generated at the
inner/outer spiral electrode, and at small radius positions caused by electrodeexpansion/shrinkage, and the directional heat transfer (rolling direction only; seen in a spiralelectrode). Also, the electrode compressed pressure and heat transfer in the plane direction weremade constant and possible.
(3) Battery shape and packaging
A prismatic-shaped battery provides a high volumetric efficiency and high energy density
in a module or package compared to a round-shaped battery. The aluminum metal case used forthe external body and the integrated resin forming with the lid and terminals allowed for arobust and completely sealed structure. Also, direct air/water cooling produced high heatradiation efficiency and, in turn, long-lasting reliability and life.
Generally speaking, a spiral electrode structure has a higher productivity compared to that ofa stacked structure. Our company has introduced a fully automated production line that applies fast
and accurate stacking and inspecting technologies exclusively for the production of large stacked
batteries in our plant. Thus, we can produce stacked electrodes with high productivity and quality.
The plant has introduced in all the processing steps, including the manufacturing control system,
which controls and monitors the manufacturing conditions in real time, and the production control
system, which controls the processes from production planning to automated procurement, stockand cost. The traceability of the raw material to a produced battery was included, and the plant
product control system considered cost while maintaining quality and reliability.

|3. Specifications and performance of MHI’s lithium-ion batteries
3.1

Specifications

External views of our large lithium-ion batteries (P140 and P060 batteries) are shown in
Figure 1, while their specifications are listed in Table 1. Both batteries have the same electrodematerial and working voltage; however, the P140 battery was designed to have a high energy
density for power storage and industrial vehicles through the securing of a conductive network witha proper dispersion of conductive materials, while the P060 battery was designed to have a highpower density for the driving energy of a hybrid vehicle by reducing the internal resistance with an
optimized electrode thickness and so on.

Figure 1 Appearances ofthe P140 (left) andP060 (right) batteries

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)
8Table 1 Specifications of the P140 and P060 batteries
Item
P140 battery
P060 battery
RemarkNominal capacity
50Ah
20Ah
Nominal voltage
3.7V
3.7Vo
0.2C，25 C
Voltage range
4.15–2.70V
4.15–2.70V
Energy density per volume266Wh/L
170Wh/L
Energy density per weight
132Wh/kg
87Wh/kg
Dimensions（H×W×T） 166.5mm×109.9mm×38.0mm
130.0mm×109.9 mm×27.6mm
ooCharge0 to 50 Co
0 to 50 Co
Operationaltemperature Discharge
20 to 50oC
30 to 50oC
range
Storage
30 to 40 C
30 to 40 Co
Maximum Continuous
100A
100A
25 Cocurrent
Instantaneous
300A
300A
25 C，10s
Cycle life
3,500 cycles or more
3,500 cycles or more
80% DOD @ 1C
Self discharge rate
2% or less
2% or less/month
Weight1.4kg
0.85kgCasingPrismatic aluminum bodyPrismatic aluminum body

3.2
(1)

PerformanceoDischarge rate characteristics (at 25 C)
The discharge rate characteristics of the P140 and P060 batteries at an atmosphericotemperature of 25 C are shown in Figures 2 and 3. The measuring conditions of both batteries
were 1C-CC/CV (constant current/constant voltage), CC: 4.15V, CV: 0.02C cut in charging;oand each current –CC: 2.7V cut in discharging in a 25 C thermostatic bath. The discharge ratecharacteristics of 0.2 to 8C of the P140 battery are shown. Compared to the 0.2C discharging
capacity, the 2C discharging showed a high discharging capacity ratio of 95%. Even the 6C
discharging exhibited a high discharging capacity ratio of 94%. Similarly, the discharge ratecharacteristics of 0.2 to 15C of the P060 battery are shown. Even at a high discharge rate of15C, a discharging capacity of 85% or higher was observed, indicating good discharge ratecharacteristics.

Figure 2
P140 battery discharge rateocharacteristics (at 25 C)(2)

oFigure 3
P060 battery discharge rateocharacteristics (at 25 C)

Charge rate characteristics (at 25 C)
The charge rate characteristics of the P140 and P060 batteries at an atmosphericotemperature of 25 C are shown in Figures 4 and 5. The measuring conditions of both batteries
were 1C-CC/CV (constant current/constant voltage), CC: 4.15V, CV: 0.02C cut in charging;oand each current –CC: 2.7V cut in discharging in a 25 C thermostatic bath. In the case of theP140 battery, a charging capacity of 90% or more was achieved during 2C-CC charging, whilea charging capacity of 80% or more was achieved during 6C-CC charging when compared tothe capacity of 0.2C-CC charging. Furthermore, in the case of the P060 battery, a charging
capacity of 96% or more was available with good charge rate characteristics.
(3) Discharge rate characteristics at low temperatures (temperature characteristics)
The discharge rate characteristics of P140 and P060 batteries at low temperatures areshown in Figures 6 and 7. The measuring conditions of both batteries were 1C-CC/CV CC:
o4.15V cut, CV: 0.02C cut in charging at an atmospheric temperature of 25 C; and 1C–CC: 2.7V
cut in discharging at each temperature condition. In the case of the P140 battery, compared tothe 25℃ discharging capacity, a discharging capacity ratio of approximately 80% wasMitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)9o

maintained, even at a low temperature of -15 C. Likewise, in the case of the P060 battery, aodischarging capacity ratio of approximately 66% was maintained at a temperature of -30 C,
and the battery still exhibited good low-temperature discharge rate characteristics.

Figure 4 P140 battery chargeocharacteristics (at 25 C)

rate

Figure 6 P140 battery discharge ratecharacteristics at low temperatures

Figure 5 P060 battery chargeocharacteristics (at 25 C)

rate

Figure 7 P060 battery discharge ratecharacteristics at low temperatures

The P140 battery was designed with consideration of its high capacity; its high capacity rateduring high rate charging/discharging was attained by securing the conductive network, adjusting
the separator porosity, diffusing the lithium-ion in the electrolyte, and easing the insertion to thenegative electrode through optimization of the conductive materials, electrolyte composition, andelectrolyte additives.1,2 Moreover, in the P060 battery, the thickness of electrode, porosity
optimization, and strengthening of the current collector, in addition to the design specifications for
the P140 battery, were thought to reduce the internal resistance, increase the charge/discharge rate,and improve the capability of charging/discharging in a low-temperature zone.

|4. Safety assessment test of the batteries
The United Nations Recommendations on the Transport of Dangerous Goods (hereinaftercalled the UN Recommendations) specifies the procedure for battery safety confirmation tests
during transportation.3 A safety confirmation test of the P140 battery was conducted at an external
institution based on these UN Recommendations. The results demonstrated that all seven items inTable 2 were satisfied to meet the standards of the UN Recommendations, with no rupture or fire.
The same test was also conducted on the P060 battery, and compliance with the UN
Recommendation was confirmed.
Table 2 Safety confirmation test based on“UN recommendations on the Transport of Dangerous Goods”
Test item

Leakage Venting Disassembly Rupture

FireAltitude simulation test (T1)
○
○
○
○
○
Thermal test (T2)
○
○
○
○
○
Vibration test (T3)
○
○
○
○
○
Shock test (T4)
○
○
○
○
○
External short-circuit test(T5)○○○Impact test (T6)○○
Forced discharge test (T8)○○
*1: A voltage decline of 90% or less is acceptable.
o*2: A battery surface temperature of 170 C or less during the test is acceptable.

Battery
Mass
Voltagedecline*1 temperature*2 loss
○
○
○
○
○
○
○
○
○
○
○ indicates acceptanceMitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)
10A nail penetration test and a crushing test were also performed, in addition to the test above.
In the nail penetrating test, a nail-shaped rod, with a diameter of 5 mm, was penetrated in the centerof the wide face of the prismatic battery. Measurements of the battery voltage, temperature, andappearance change with time after nail penetration were recorded. The battery appearances before
and after the test are shown in Figure 8. The battery voltage declined with a short circuit between
the positive and negative poles. The battery temperature rose with the short-circuit current, andoperation of the safety venting was observed, irrespective of the state of charge. A rupture or fire of
the battery body did not occur.

BeforeFigure 8After

P140 battery appearances before and after the nail penetrating test

In the impact test, a round-shaped jig, 8 mm in radius, was used to impact each of the wideand narrow faces in two directions. The impacting ratio was approximately 35% and the battery
voltage, temperature, and appearance change with time were observed after the battery wasimpacted. The battery appearances before and after the test are shown in Figure 9. In the case ofimpacting on the narrow face, the battery voltage and temperature showed no change, and thesymptoms of an internal short circuit were not observed, irrespective of the state of charge. On thecontrary, in the case of impacting on the wide face, a temperature rise associated with an internalshort circuit was observed. However, rupture or fire of the battery was not observed. Thus, weverified the safety of batteries made using our large battery design, including their materials.

BeforeFigure 9Narrow face after the test

Wide face after the test

P140 battery appearances before and after the impacting test

|5. Examples of applied products
Currently, the P140 battery is already being produced, and commercialization of systems
using the large lithium-ion battery is in progress. As an example, the appearance and specificationsof a verification unit for a 1,000-kW output, 400-kWh class container-shaped large-capacity
energy-storage system (ESS) are shown in Figure 10. The ESS is expected to be used for load
leveling in the grid-connected operation of wind-farm and mega-solar power generation, and forpeak cutting of power demands for factories and buildings. The verification of grid connected
operation with the factory power grid in coordination with the inverter, and the temperature
characteristics and lifetime evaluation on charging/discharging are in progress. For transportationuse, the lithium-ion battery was installed in an electric bus by modifying a public transportation
diesel engine bus. A running test on a bus route is currently being conducted. Verification of thecontrolling-circuit system reliability, including the motor and inverter required for the power train
development, charger system, battery modularization, and battery packaging, is in progress.
Thus, MHI is moving forward with the commercialization of lithium-ion batteries as
power-source backups for condominiums, hospitals, office buildings, factories, wind-farm andMitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012)11

mega-solar power generation, and micro-grids. They will also serve as stationary batteries for
power storage of renewable energy and grid shaving/stabilizing. Additionally, they will work as atransportable electric power source for industrial machines, such as forklift trucks and vehicles forhigh-lift work, public transportation (e.g., electric buses and tramcars), and construction (e.g.,electric shovels and excavators). Figure 11 shows application examples.
Capacity
OutputAppearance of the verification unit
at the Nagasaki Shipyard and Machinery Works

400-kWh class (15min)
1,000 kW (500kW2)40-ft container【Battery rack, 12 units
Container size
(23 modules/unit)】
20-ft container【500-kVAPCS panel, 2 units】
PCS control panel
Controller panel
Ancillary
Grid connection transformerfacilities
With air conditioning facilities

Figure 10 1,000-kW output, 400-kWh class container-shaped large-capacity energy-storage
system (ESS)

Figure 11

Examples of future applications of large lithium-ion batteries|6. Conclusion
MHI has been working on optimizing the electrode materials combination, battery structure,and battery production process of large lithium-ion batteries for high-performance power storageand industrial use. Currently, the 50-Ah class P140 battery is being produced and is available on
the market. Also, sample production for the 20-Ah class P060 battery has started.
Aside from battery technology, knowledge of the power grid and transportation power trainsis required in the cooperative design of commercial lithium-ion batteries. Our company has
provided various products that contribute to society’s infrastructure. We will continue to develop
lithium-ion batteries for various power storage and industrial uses, along with products and systems
that incorporate them.

References
1.
2.
3.

M. Ue: Prog. In Batteries and Battery Materials, 14,137 (1995)
S.E Millman and G. Kirczenow: Study of the Phase Diagrams of Graphite Intercalation Compounds, Phys.
Rev., B28, 3482-3500 (1983)
Recommendations on the TRANSPORT OF DANGEROUS GOODS UNITED NATIONS New York andGeneva, 2009