IEEE Power & Energy Magazine - September/October 2017 - 29

The installed Li-ion battery capacity is projected to
increase rapidly, so it is expected to become the dominant
battery storage technology for the future.
have discrepant charging strategies. For example, a constantcurrent/constant-voltage protocol is often applicable to Li-ion
batteries. Emerging charging methods consider multiple objectives to seek Pareto-optimal solutions, e.g., tradeoffs among
charge time, energy loss, and charge-induced health decay.

Fault Diagnosis
Functional safety is critical in large-scale battery storage.
Electrical, thermal, and electrochemical faults therefore should
be diagnosed, isolated, and identified via advanced hardwareand software-redundancy approaches. For example, modelbased observer design and structural analysis can be made to
diagnose faults of current, voltage, and temperature sensors.
More sophisticated algorithms are needed to enhance the robustness of fault diagnosis against disturbances and modeling uncertainties.

Conclusions and Future Prospects
Battery energy storage is of great importance for increasing
spatial-temporal operational flexibility of the electric grid.
Current commercial utility-scale battery technologies include
lead-acid, NiMH, L
- i-ion, redox flow, and NaS batteries. These
technologies often display different technical and economic
characteristics in terms of energy density, power density, energy
efficiency, lifetime, safety, cost, and so forth. These differences
render one technology especially appropriate for a particular
energy storage application, due to certain technical/economic
advantages. That is why we still see various battery technologies in the energy storage market across the globe.
Every battery technology is developing and advancing.
However, their rates of development vary considerably. Compared to lead-acid, NiMH, and NaS batteries, Li-ion and
RFBs are increasingly deployed due to significant performance improvements and cost reductions spurred by extensive technological demand and astonishing market growth.
As Navigant Research data demonstrate, the Li-ion battery is
well positioned to be the predominant battery storage technology with the most increased installed capacity in the future. Popular battery vendors, such as AES and Tesla, choose
Li-ion batteries as their storage products, creating fierce competition in the energy storage market.
The following outlines the main future directions of battery storage technologies, along with battery management.

Lead-Acid Batteries
Advanced lead-acid batteries are an emerging technology.
An interesting design is inspired by the advantages of a traseptember/october 2017

ditional lead-acid battery and an ultracapacitor-thus
called an ultrabattery. It is synthesized by introducing an
ultracapacitor's negative electrode, composed of activated
carbon, into the standard lead-acid battery, as illustrated
in Figure 7.
Advanced lead-acid batteries are rapidly evolving, with
several variants observed more recently. Generally, there
are two fundamental changes. First, the carbon-based electrode inhibits the sulphation that generally occurs in conventional lead-acid options and results in increased internal resistance and decreased performance. Second, with
new composition, the batteries can operate within a large
SOC range, particularly at low SOC levels. As a result,
the side reactions of electrolysis slow down, and the corrosion and desiccation of the positive electrode can be
noticeably alleviated. This advanced technology may dramatically improve the performance and durability of leadacid batteries.

Li-Ion Batteries
It is profoundly important to develop better Li-ion batteries suitable for large-scale energy storage applications. The
future emphasis of such development could focus on how to

Separator
+

Separator
-

PbO2

PbO2
i
+

i1
-

PbO2

i
-

Carbon
Electrode

figure 7. The schematic of an advanced lead-acid battery
consisting of a traditional lead-acid battery (upper right)
and ultracapacitor (upper left). PbO2: lead oxide. (Source:
Advanced Lead-Acid Battery Consortium.)
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - September/October 2017