Not All BESS Cells Degrade the Same

Understanding Degradation Across Four Energy Storage Technologies

The battery energy storage system (BESS) market is booming, global BESS demand jumped 51% in 2025 as installations topped 300 GWh. But behind the growth headlines lies an inconvenient truth: battery degradation is eating into projected lifespans, and the problem is especially acute in high-demand applications like data centers. The root cause isn’t just chemistry, it’s a mismatch between how batteries were designed to operate and how they are actually being used.​

Not all BESS cells degrade at the same rate, or through the same mechanisms. Four energy storage technologies, standard LFP (pouch and cylindrical), LFP prismatic, solid-state, and supercapacitors—each offer fundamentally different degradation profiles. And beyond chemistry and cell format, one of the most underappreciated factors in battery longevity is thermal management. Understanding how cooling architecture affects degradation is just as critical as choosing the right cell.

How Battery Degradation Works

All lithium-ion batteries degrade through two primary mechanisms: loss of lithium inventory (LLI) and loss of active material (LAM) at the electrodes. During cycling, a solid-electrolyte interphase (SEI) layer builds up on the anode, trapping lithium ions and increasing internal resistance. Deep discharges, high C-rates, elevated temperatures, and extended time at high state-of-charge all accelerate these processes.

Key variables that impact BESS degradation include state of charge ranges, operating temperature, depth of discharge, C‑rate (charge and discharge speed), calendar aging, voltage limits, and cell balancing. Research on commercial 100 Ah prismatic LFP cells cycled at 45°C found that electrolyte loss from enhanced SEI film evolution was the primary degradation pathway, with larger LFP particles prone to fracturing and iron deposition accelerating SEI formation.

But critically, how much each of these factors matters depends on the physical construction and chemistry of the cell, and on whether the thermal management system can keep every cell operating in its optimal temperature band.

The Four BESS Cell Technologies

LFP (Pouch and Cylindrical Form Factors)

Standard lithium iron phosphate (LFP) chemistry is the workhorse of the BESS industry, chosen for its safety, thermal stability, and long cycle life relative to NMC alternatives. LFP cells in pouch and cylindrical form factors are widely deployed in grid-scale and behind‑the‑meter applications.

Pouch cells use a flexible aluminum‑plastic laminate enclosure with stacked or wound electrode layers. They offer high volumetric energy density, lightweight construction, thin profiles (as low as 4 mm), and efficient heat dissipation from their large surface area. However, pouch cells carry the highest risk in terms of mechanical and thermal safety among LFP form factors, with no rigid casing, they are vulnerable to swelling, gas buildup, and mechanical degradation over time. In demanding BESS applications with sustained cycling, pouch cells tend to have the shortest cycle life because temperature swings and poor heat management in tightly stacked configurations accelerate aging.

Cylindrical cells (18650 and 21700 formats) feature a jellyroll design wound into a cylindrical shape. They are highly reliable, thermally uniform, and benefit from decades of mass‑production optimization. However, dead spaces between cells in a pack reduce volumetric energy density, making them less space‑efficient for large‑scale BESS deployments. Cylindrical cells are best suited for residential and modular systems where serviceability matters.

Both pouch and cylindrical LFP cells typically achieve 3,000–6,000 cycles to 80% state of health, depending on operating conditions. Internal resistance rises approximately 50–150% over the cell’s lifetime, generally faster in LFP than in NMC chemistries.

LFP Prismatic

LFP prismatic cells have emerged as the dominant format for grid‑scale and containerized BESS deployments, and for good reason. Their rigid, rectangular metal casing provides structural robustness that directly addresses the degradation weaknesses of pouch and cylindrical formats.​  

The current industry standard is the 314 Ah LFP prismatic cell, produced by multiple leading manufacturers. These cells deliver substantially superior cycle life specifications:

• 10,000+ cycles at 0.3C charge/discharge to 80% SoH at 25°C and 100% DoD​  
• 15,000 cycles at 0.3C to 70% SoH under the same conditions​  
• 8,000 cycles at 0.5C to 80% SoH at cell level​  
• 11,000+ cycles at 0.5C to 70% SoH for optimized designs​  

At the system level, accounting for calendar aging and real‑world temperature conditions up to 35°C, these cells still deliver **6,000–8,000 cycles to 70% SoH** over a 15–20 year operational life.​

Why Prismatic Outperforms Other LFP Form Factors

The structural advantages of prismatic cells translate directly into degradation resistance:

Research has demonstrated that appropriate external pressure, which prismatic cells inherently provide through their rigid casing, it reduces capacity degradation by 6.0% or more compared to unpressurized cells over 1,000 cycles. Pressurized cells show fewer instances of lithium plating, electrode folding, and cracking, all of which are key aging mechanisms. Pouch cells require external compression systems to achieve similar pressure conditions, adding complexity and potential failure points.​

Solid-State Batteries: Graphene-Enhanced Solid-State Approach

Solid‑state batteries replace the liquid electrolyte found in conventional lithium‑ion cells with a solid polymer electrolyte and often use graphene‑enhanced electrodes to improve conductivity and heat spreading. Commercial solid‑state cells in this class deliver more than 15,000 full cycles at 0.5C and 100% depth of discharge, with round‑trip efficiency on the order of 96–97%, and projected design lives of 15–20 years in stationary applications. Typical products support discharge rates from about 5C up to 20C, operate roughly between ‑20°C and +55°C for discharge, and maintain low internal resistance (ESR in the tens of milliohms), which limits resistive heating and further slows degradation.

Key characteristics include:

• 15,000+ cycles at 0.5C charge/discharge and 100% depth of discharge  
• 96.8% round‑trip efficiency—substantially higher than conventional LFP batteries at ~92%  
• Solid and polymer electrolyte eliminates liquid decomposition, the primary driver of SEI layer growth and capacity fade in conventional Li‑ion cells  
• 5C to 20C discharge rates available on select products, enabling fast‑response applications that would destroy conventional LFP cells  
• Operating temperature range of ‑20°C to +55°C for discharge, with storage tolerance to +60°C  
• ESR ≤ 50 mΩ at 25°C, indicating low internal resistance and efficient energy transfer  
• Less than 3% monthly self‑discharge, minimizing calendar aging losses  
• Design life of 15–20 years projected based on supercapacitor‑derived technology  

Containerized solid‑state systems at around 1 MWh/500 kW per 20‑foot enclosure are already commercially available, integrating BMS, fire protection, cooling, and standard industrial communications into turnkey packages for C&I and data center use.

What makes these commercial solid‑state systems fundamentally different from conventional LFP is the degradation mechanism itself. With no liquid electrolyte to decompose, the primary aging pathway (SEI layer growth from electrolyte breakdown) is dramatically reduced. Graphene’s high electrical conductivity enables rapid electron movement with less resistive heating, while its thermal conductivity helps dissipate heat more evenly across the cell. The result is a cell that not only starts with more cycles but loses capacity more slowly per cycle than its liquid‑electrolyte counterparts.​

Supercapacitors and Electrostatic Energy Storage

Supercapacitors, also called ultracapacitors or EDLCs (electrochemical double‑layer capacitors), store energy electrostatically rather than electrochemically, which fundamentally changes the degradation equation. Because there is no chemical reaction driving storage and release, supercapacitors experience virtually no wear and tear per cycle.

Modern utility‑grade ultracapacitor cells (electrostatic energy storage) routinely exceed **500,000 charge–discharge cycles** between rated voltage and half‑rated voltage at 25°C, with less than 30% loss in capacitance and less than a 200% increase in ESR. Large‑format EDLC cells in this class achieve **10‑year+ design life** at rated voltage and 25°C, with operating ranges from about ‑40°C to +70°C and peak power densities above **20 kW/kg**. Because energy is stored electrostatically rather than via chemical reactions, degradation per cycle is negligible compared with any battery chemistry, making cycle life effectively measured in the hundreds of thousands to millions of events.

Typical performance:

• 500,000+ cycles between rated voltage and half‑rated voltage at 25°C, with less than 30% capacitance decrease and less than 200% ESR increase​  
• 1,000,000+ cycles on large‑format cells designed for grid and transportation applications​  
• 10‑year design life at rated voltage (2.7 V) and 25°C—with lower operating voltage extending design life significantly beyond 10 years​  
• 15‑year design life on advanced module platforms​  
• Peak power density exceeding 20 kW/kg—over 100× that of conventional LFP batteries​  
• Charge/discharge currents up to 1000C—enabling microsecond to millisecond response times​  
• Operating temperature range of ‑40°C to +70°C, far exceeding any battery chemistry  
• Completely maintenance‑free with no conditioning required​  
• No chemical reactions during charge/discharge, the highly reversible process relies solely on ion movement within the electrolyte, not making or breaking chemical bonds​  

Rack‑level ultracapacitor modules for grid and data‑center use offer **15‑year design life**, extremely high C‑rate capability (up to the order of 1000C), and maintenance‑free operation, which makes them ideal buffers for millisecond‑scale power spikes while batteries handle longer‑duration energy needs.

The trade‑off remains energy density, ultracapacitors store substantially less energy per unit volume than batteries. But for short‑duration, high‑power applications like absorbing GPU load spikes, this limitation is irrelevant. The ultracapacitor only needs to store enough energy to buffer transients lasting milliseconds to seconds, not hours.​

Why Data Centers Are Destroying Their LFP Batteries

The explosion of AI workloads has created a power profile that conventional BESS was never designed to handle. Traditional data centers consumed steady, predictable loads. AI‑driven facilities, with massive GPU clusters, surge from idle to 100% utilization in milliseconds, creating power swings of 100 MW or more that occur multiple times per minute on sub‑second timescales.

This matters for battery degradation because most commercial BESS solutions are designed for grid applications requiring low charge/discharge rates (typically around 0.5C) and large energy capacities cycled once or twice daily. When data centers subject these same batteries to high‑frequency, high‑C‑rate transient cycling driven by GPU workloads, degradation accelerates dramatically.

Lithium‑ion batteries common in UPS systems lose 1–3% of capacity annually under normal operation, but high‑frequency fluctuations from GPU clusters accelerate this significantly. Repeated high‑rate discharge increases internal resistance, shortens overall lifespan, and creates thermal stress that compounds over time. In high‑density AI data center environments, UPS lithium batteries face more frequent, faster, and higher‑current discharge events than ever anticipated, creating cascading technical and safety challenges.

The core problem is that data centers are cycling batteries far more aggressively than the design case assumed. A BESS designed for one or two cycles per day at 0.5C is instead being hit with dozens or hundreds of partial cycles at varying C‑rates throughout every hour. Each of those micro‑cycles contributes to SEI layer growth, lithium inventory loss, and active material degradation. The batteries aren’t failing because LFP chemistry is flawed, they’re failing because the duty cycle has fundamentally changed.​  

As one analysis put it: “UPS lithium batteries are no longer passive backup components, they operate continuously under high stress and must support dynamic, high‑density computing workloads.” Without a comprehensive lifecycle management strategy, these systems experience unexpected failures, increased maintenance costs, and reduced availability.

How Cooling Architecture Impacts BESS Degradation

Cell chemistry and form factor only tell half the degradation story. The other half is thermal management. Temperature is one of the most powerful accelerants of battery degradation, and the method used to manage heat has a direct, measurable impact on cycle life, capacity fade, and safety.

Lithium‑ion batteries are designed to operate within a narrow temperature band, typically 25–40°C. Performance, safety, and lifespan all depend on keeping every cell as close to this range as possible. Real‑world testing has demonstrated that a 20°C increase in operating temperature, from 25°C to 45°C, reduces cycle life by 3,000 to 4,000 cycles for the same LFP cell. That single variable alone can cut a battery’s useful life in half.

Three cooling architectures dominate the BESS market today, each with vastly different implications for degradation.

Air Cooling

Air cooling is the simplest and most cost‑effective thermal management approach. It uses fans and air ducts to push ambient or conditioned air across battery modules, relying on forced convection to remove heat.

Advantages:

• Lowest upfront cost—only requires fans and ducting  
• Simple design with high reliability and no fluid leak risk  
• Rapid deployment—installation time reduced by over 30% vs. liquid cooling  
• Easier maintenance, especially in cold climates  

Degradation drawbacks:

• Heat removal is inherently uneven, creating thermal gradients across cells and racks that accelerate degradation  
• Temperature uniformity is poor—cells near airflow inlets run cooler while those downstream run hotter, causing uneven aging across the pack  
• Struggles in high‑temperature environments where inconsistent heat dissipation shortens battery lifespan  
• Requires large buffer spaces between components for airflow, reducing energy density  
• More susceptible to dust, moisture ingress, and external temperature swings  
• Round‑trip efficiency reaches only ~85.5% at 0.5C discharge, partly due to higher auxiliary power consumption  

Air‑cooled systems are categorized as “ESS 1.0” in the industry and remain viable for budget‑sensitive, small‑to‑medium installations in mild climates. For utility‑scale, high‑cycling, or data center applications, their inability to maintain tight thermal uniformity makes them a poor choice for maximizing battery life.

Liquid Plate Cooling

Liquid cooling uses a closed‑loop fluid circuit—typically water‑glycol coolant—circulated through cold plates or channels attached to battery modules. The coolant absorbs heat through contact with the plate surface and transfers it to external heat exchangers. This is the current industry standard for large‑scale BESS.

Advantages:

• Superior heat dissipation—water’s specific heat capacity is 4.18 kJ/kg·K vs. 1.0 kJ/kg·K for air, meaning it absorbs over 4× more heat for the same temperature rise  
• Maintains battery pack temperature fluctuations within ±3°C, extending cycle life 10–30% compared to air cooling  
• Higher space efficiency—eliminates large air ducts, enabling ~4.5 MWh per 20‑ft container  
• Low noise (below 65 dB), suitable for residential or indoor installations  
• Round‑trip efficiency reaches ~90.3% at 0.5C discharge  
• Operates effectively from ‑30°C to 55°C with active pre‑heating capability  

Degradation drawbacks:

• Coolant heats up as it flows through the plate, creating a temperature gradient along the flow path—cells near the outlet run hotter and age faster  
• Flow distribution across complex piping networks is rarely uniform, causing some plates to receive strong flow while others starve  
• Relies on physical surface contact to remove heat, meaning any gap, uneven pressure, or manufacturing tolerance introduces thermal resistance and hot spots  
• Temperature spreads of 10–15°C across plates have been observed in thermal simulations  
• More than half of system‑level failures in some field inspections trace back to cooling and integration issues rather than defective cells  
• Higher initial investment, 20–30% more than air cooling, plus ongoing maintenance for seals, pumps, and coolant condition  

Liquid plate cooling represents a major step forward from air cooling, but its contact‑based architecture introduces structural limitations that compound over years of operation. The uneven aging it creates becomes the hidden cost of many BESS projects.

Liquid Immersion Cooling

Immersion cooling represents the most advanced thermal management approach currently available for BESS. Battery cells are fully submerged in a non‑conductive, fire‑retardant dielectric fluid that makes direct contact with every surface of every cell.

Advantages:

• Full‑surface heat transfer eliminates hot and cold spots entirely  
• Maintains cell temperatures near 25°C with variation limited to ±1.5°C under normal operating conditions  
• Extends battery cell life by up to 22% compared to liquid plate cooling in controlled testing  
• Inherent fire safety—the dielectric fluid physically isolates cells from air, removing a key element of the fire triangle  
• Prevents thermal runaway propagation by absorbing thermal spikes and isolating affected cells  
• No dependence on surface contact quality, mechanical tolerances, or flow balancing  
• Eliminates the gradients caused by uneven contact pressure and flow maldistribution  

Trade-offs:

• Highest upfront cost of the three approaches  
• Requires specialized dielectric fluid and sealed module designs  
• Relatively newer technology with less field deployment history than liquid plate cooling  
• Maintenance requires handling and potential replacement of dielectric fluid  

The degradation advantage of immersion cooling is rooted in physics: by maintaining every cell within ±1.5°C of its optimal temperature, it eliminates the uneven aging that plagues both air and liquid plate systems. Studies show that temperature differences as small as 3°C can significantly accelerate degradation, and in some configurations, larger differences cause batteries to age at roughly twice the normal rate. Immersion cooling keeps the entire pack aging uniformly, which means the weakest cell in the system degrades at nearly the same rate as the strongest, preserving usable capacity far longer.

The Cooling–Degradation Connection for Data Centers

For data centers running AI workloads, the cooling choice amplifies every degradation factor discussed earlier. GPU‑driven transient cycling already stresses batteries beyond their design envelope. If those batteries are also subject to thermal gradients from inadequate cooling, the degradation compounds:

• High C‑rate cycling generates more heat per cycle, making thermal management more critical, not less
• Uneven cooling causes the hottest cells to degrade first, and in a series string the weakest cell limits the entire pack’s capacity
• Frequent partial cycling in thermally stressed cells accelerates SEI growth and lithium plating more than the same cycling pattern would in uniformly cooled cells  

For data center BESS applications where batteries face aggressive duty cycles, the combination of LFP prismatic cells (for structural and cycling durability) with immersion cooling (for thermal uniformity) represents the most degradation‑resistant architecture available today. Notably, advanced graphene‑enhanced solid‑state cells, with their inherently lower thermal sensitivity due to improved heat dissipation—benefit from immersion cooling as well, but may also perform exceptionally under simpler cooling configurations where conventional LFP would suffer.​

Better Approaches: Prismatic Cells, Solid-State, and Electrostatic Hybrids

LFP Prismatic for Bulk Energy Cycling

For data centers that need sustained energy delivery—load shifting, energy arbitrage, and extended backup—LFP prismatic cells are the superior choice over pouch or cylindrical alternatives. Their 8,000–15,000 cycle ratings at cell level provide significantly more headroom for the aggressive cycling that data center applications demand. The rigid casing’s mechanical compression maintains electrode contact integrity and reduces lithium plating, which is especially important when cycling frequency increases.

High‑C‑rate prismatic designs are emerging specifically for this use case. Some systems, for example, use purpose‑built prismatic battery architectures with charge rates of approximately 2C and discharge rates up to 4C, enabling more compact solutions that handle sub‑second power swings without the oversizing required by conventional 0.5C systems.

Graphene-Enhanced Solid-State for High-Cycling, Safety-Critical Applications

Graphene‑enhanced solid‑state cells offer a compelling alternative for data center applications where safety and cycle life are paramount. At 15,000+ cycles and ~96.8% round‑trip efficiency, these cells match or exceed the best LFP prismatic specifications, while eliminating the liquid electrolyte that drives the dominant degradation pathway in conventional lithium‑ion. The ability to operate at 5C–20C discharge rates makes them uniquely suited for the dynamic, high‑C‑rate power profiles that AI workloads demand. Their solid polymer electrolyte means no risk of electrolyte leakage, thermal runaway propagation, or the internal gas generation that causes pouch cell swelling, delivering both longer life and inherently safer operation.

Ultracapacitors for Transient Spike Absorption

The most promising architecture for AI data centers may not be a single technology but a hybrid approach: ultracapacitors handling short‑duration transient spikes, with LFP prismatic or solid‑state batteries providing bulk energy storage.

Ultracapacitors deployed at the rack, zone, or distribution level can absorb inrush currents and fast load spikes in microseconds to milliseconds, far faster than any battery can respond. With charge/discharge currents up to 1000C and peak power density exceeding 20 kW/kg, a relatively small deployment of ultracapacitors can buffer the massive, instantaneous power swings generated by GPU clusters.

Independent evaluations of rack‑level supercapacitor deployment have shown:

• Current fluctuations (ΔI) reduced by 60–70%
• Nuisance‑trip rates down 80–90%
• PUE improvements on the order of 0.02–0.05

Other commercial systems take a similar approach, deploying hybrid supercapacitors within GPU racks to modulate the power fluctuations from AI training and inference workloads.

This hybrid architecture works because it separates two fundamentally different power demands:

• Transient spikes (microseconds to seconds): handled by ultracapacitors with 500,000–1,000,000 cycle life, microsecond response, and zero chemical degradation
• Sustained energy delivery (minutes to hours): handled by LFP prismatic or solid‑state batteries optimized for energy density and long cycle life  

By preventing the rapid partial‑cycling that destroys batteries, ultracapacitors effectively extend the life of the battery cells behind them. The batteries see a smooth, predictable load profile rather than the chaotic transient envelope generated by GPU clusters. This means the battery cells can operate within their designed parameters, moderate C‑rates, predictable DoD ranges, controlled temperature, and actually achieve their rated 10,000–15,000+ cycle lifespans.

Technology Selection Framework

The energy storage industry is at an inflection point. LFP chemistry dominates, demand rose 48% year‑on‑year in 2025, but the assumption that all BESS cells perform equally, or that all cooling systems protect batteries equally, is costing operators millions in premature replacements and downtime.​

Data centers adopting AI workloads cannot afford to treat battery selection or thermal management as commodity decisions. The evidence points toward a multi‑technology solution:

• LFP prismatic cells for proven bulk energy cycling
• Graphene‑enhanced solid‑state cells for safety‑critical and high‑C‑rate applications with 15,000+ cycle longevity
• Ultracapacitors for electrostatic transient absorption with 500,000–1,000,000 cycle endurance
• Immersion cooling to maintain the thermal uniformity that maximizes the lifespan of every cell in the system    

Together, these technologies address the full spectrum of challenges, from microsecond GPU spikes to multi‑hour energy arbitrage to the silent, slow degradation caused by uneven temperatures. For projects being designed and built today, the combination of the right cell technology, the right electrostatic buffer, and the right thermal management architecture represents the most technically sound and economically defensible path forward.

Partner with Empower IT for Your Energy Storage Solution

Choosing the right BESS isn’t a one‑size‑fits‑all decision, it requires matching cell chemistry, form factor, cooling architecture, and hybrid configurations to your specific workload profile, cycling demands, and site conditions.

Empower IT is a vendor‑agnostic energy storage solutions provider that works with a wide range of manufacturers worldwide, including suppliers of ultracapacitors, solid‑state batteries, and leading LFP prismatic OEMs, to design, source, and integrate the right BESS for your project. Whether you need LFP prismatic systems for bulk energy cycling, solid‑state cells for high‑C‑rate safety‑critical deployments, ultracapacitors for GPU transient absorption, immersion‑cooled architectures for maximum cell longevity, or a combination of all of the above, Empower IT evaluates the full technology landscape and delivers a solution engineered for performance, lifecycle cost, and reliability.

What Empower IT brings to your project:

• Technology‑neutral sourcing across LFP prismatic, solid‑state, ultracapacitor, and other manufacturers—selecting on performance and fit, not brand loyalty  
• Cycling and degradation analysis to match your actual duty cycle to the right cell, electrostatic buffer, and cooling architecture
• Turnkey BESS specification and integration including container architecture, PCS/EMS interfaces, thermal management, and protection schemes
• Procurement leverage from competitive multi‑OEM sourcing that balances price, performance, and delivery timelines  

Don’t let your batteries become the bottleneck. Contact Empower IT today to discuss how the right combination of cell technology, electrostatic storage, thermal management, and hybrid architecture can protect your investment and power your project for decades.