After all, adopting these measures can reduce investment risk and increase trust in new technologies, regardless of the industry. With this in mind, DNVGL, a Norwegian global quality assurance and risk management consulting firm, recently released its third-generation battery performance scorecard.
In DNV GL's evaluation this year, 22 battery manufacturers provided battery products for testing on the DNV GL Battery Scorecard. The company stated that even if no battery manufacturer is willing to disclose their name, DNV GL will continue to work with its technology partners to increase transparency, and this remains an ongoing process.
Industry analysts say that, looking at recent technological and market trends, lithium iron phosphate (LFP) batteries are once again gaining popularity, including for stationary energy storage systems. This type of battery dominated the market from 2012 to 2015, but was superseded by nickel-manganese-cobalt (NMC) and nickel-cobalt-aluminum (NCA) ternary lithium batteries after 2016. However, Chinese battery manufacturers such as CATL and BYD are now seeing the potential and trend of this battery and are driving the development and production of LFP battery technology.
DNVGL's third annual battery scorecard tested the charge/discharge behavior and temperature dependence of 22 batteries with different chemistry properties and identified important product trends.
Battery capacity is getting bigger and bigger
Another clear trend is the increasing battery capacity of energy storage systems; current lithium iron phosphate batteries have a capacity of approximately 200 Ah. This is because larger capacity battery cells can save on raw material costs.
Further innovations are expected in electrode material selection, battery structure, and system architecture, but no major breakthroughs in battery technology are anticipated in the coming years. DNV GL believes lithium-ion batteries will remain the preferred choice for energy storage. The company states that it does not expect other battery technologies to replace lithium-ion batteries within the next three to seven years, as lithium-ion batteries will benefit from economies of scale in transportation, consumer electronics, and energy storage applications.
According to research by DNV GL, the current cost of lithium-ion batteries is approximately $100 per kWh, and the company's analysts predict that the price of battery energy storage systems will drop significantly over the next decade.
Deploy more solar + energy storage projects
Another trend observed by analysts is the increasing co-location of energy storage systems with solar or wind power installations. Consequently, energy storage project developers and users are demanding 20-25 year battery lifespans for their battery storage systems to match the lifespan of solar power installations. Developers deploying grid-scale battery storage systems have responded to this demand by including comprehensive overhaul, enhancement, operation, and maintenance services in their battery storage system deployment contracts.
DNV GL states that the way batteries are used will also change. In the early applications of energy storage systems, commercial service projects primarily focused on user-side energy storage systems. Today, however, an increasing number of battery energy storage systems need to shift solar power generation from daytime to nighttime peak electricity demand periods. This places different demands on battery technology, including charge-discharge stability and battery degradation under different charging conditions.
DNVGL tested the charge-discharge stability of 22 products in the scorecard and determined the number of charge-discharge cycles required to cause a 1% capacity loss. In this year's scorecard, the average number of charge-discharge cycles required to cause a 1% capacity loss was 381, with significant differences among the different batteries: lithium iron phosphate batteries required 135–448 cycles, NMC ternary lithium-ion batteries required 180–849 cycles, NCA batteries required 143–330 cycles, and the best-performing titanate battery required 1.067 cycles.
Capacity statistics after charging and discharging
According to tests conducted by research institutions, on average, a battery's capacity will decrease to 90% of its nameplate capacity after 1800 charge-discharge cycles. The scorecard emphasizes that this degradation needs to be understood as a function of temperature. If all charge-discharge cycles are conducted at 10°C, the battery capacity will decrease to approximately 85% on average after 1000 cycles. DNVGL's testing team observed this temperature sensitivity in all battery products. Titanate batteries performed best in this regard, maintaining 90% of their nameplate capacity after 8609 charge-discharge cycles. Two NMC ternary lithium-ion battery products followed closely behind, losing 10% of their capacity after 6410 and 4500 charge-discharge cycles, respectively.
Regarding State of Charge (SOC), the scorecard identified a 50%–80% SOC window where NMC ternary lithium-ion batteries are more prone to degradation. Lithium iron phosphate (LFP) batteries, on the other hand, tend to degrade within a 30%–40% SOC window. DNVGL states that evaluating the primary degradation vectors in battery projects—SOC, charging rate, and temperature—is crucial. The latter two are typically the main causes of battery degradation. Scorecard researchers say that, depending on battery characteristics, the operating range based on SOC may be a secondary consideration.
Charging rate is a more important factor, and a lower charging rate is generally better for battery performance. In DNVGL's tests, lithium iron phosphate (LFP) and titanate batteries typically exhibited higher charging rates. Although testers noted that many NMC ternary lithium-ion batteries also performed well, they suffered from temperature increases at high charging rates.
The scorecard researchers also pointed to developments in safety. Standards such as the UL9540A protocol require improved testing and have taken a step towards safety transparency. However, DNV GL stated that the lack of new standard classifications and non-compliance standards is confusing. Containerized energy storage solutions are constantly evolving, meaning that battery energy storage systems can be fully accessed from the outside, avoiding the risks of operators and maintenance personnel entering the container. The DNV-GL scorecard researchers added that many battery suppliers are working to improve battery fire safety standards and prevent thermal runaway cascading effects.
