Keep getting asked about cell energy roadmaps and wanted to put this in context, hence using our cell database to set the scene and then walk out to 2035.

How the charts were built

• The year for each cell is its start of production. Where a pre-production cell has no production date, we used the year it was announced.
• A cell counts as production if it is a C or D sample, or has no sample level recorded, and is dated 2026 or earlier. Pre-A, A and B samples and anything dated after 2026 are shown as pre-production. The cell sample maturity page explains the A to D levels.
• The best-cell line for each chemistry is the highest value reached by any production cell up to that year, so it only ever rises.
• Four groups: graphite or silicon-blend NMC, NCA, NCMA and LCO; LFP and LMFP; sodium-ion; and next-gen EV-format, which covers semi-solid, solid-state and lithium-metal cells from automotive programmes. Drone and aviation cells using the same chemistries are plotted as a separate dotted line and are not projected.
• Seven rows were left out because the numbers cannot be right for the stated chemistry, for example LFP cells listed at close to 900 Wh/L. They are being checked in the database.

Read more here: https://www.batterydesign.net/cell-energy-density-roadmap-2035/

Saw a post looking at this on LinkedIn and some comments around CATL analysis, just had to have a look: https://www.batterydesign.net/golden-ratio-for-cell-design/

A very different article for us to publish, after reading the draft we really wanted to put this out there as it rang so many bells.

Over the past 25 years, battery technology has improved dramatically, yet battery startups have struggled. At Catalus Capital, we have unique and extensive insight into the industry, resulting in an informed opinion on what young battery companies must do to succeed.

Over decades, energy density has increased, costs have fallen, and power capabilities have climbed. For illustration, pack prices reached a record low of $108 per kilowatt-hour in 2025, 93% below where they stood in 2010 in real terms. [1] Yet, unlike many other high-tech industries, most of these advances have come from large, established organizations, not startups. In an unusually persistent degree of concentration, about 80% of battery patent families filed between 2000 and 2018 came from a limited group of very large companies, even as battery patenting grew 14% annually (four times the 3.5% average across technologies). [2] Meanwhile, battery startups have consistently failed to turn working technology into working businesses.

When these startups fail, technical reasons are usually given: the chemistry did not perform as expected, cycle life was too short, or costs were too high. But after examining hundreds of battery startups, we identified a different pattern.

In many battery startups, business development focuses on distant future markets while R&D is fixated on achieving step-change improvements for a next-generation product. The result is a familiar pattern: companies pursue large customers that are realistically four years away from actually buying—while devoting a large amount of R&D resources to pursuing breakthroughs—instead of delivering real products to smaller customers, gathering real-world data, and learning quickly.

Historical Performance

To explore this phenomenon further, we assembled a cohort of the 14 most prominent innovative battery companies from the first cleantech wave (roughly 2005 to 2015) and analyzed their outcomes.

As of today, twelve of the fourteen have not reached commercialization. [3] Seven entered bankruptcy, shut down, or underwent an asset-level wind-down; three were acquired before reaching profitability; and two remain active more than a decade later with no publicly verified sustained production. Only two achieved meaningful product adoption, yet neither has publicly demonstrated both durable commercialization and profitability.

Table 1: The 14-company first-wave cohort (roughly 2005 to 2015), showing total disclosed capital raised through August 2026 and outcome as of that date. Capital is stated all-in: disclosed equity, debt, and government funding actually received. Sources: SEC filings (Forms D, S-1, 10-K, 10-Q, and 8-K), U.S. Bankruptcy Court dockets, USAspending.gov federal award records, and company announcements. [4]

A second, partially overlapping cohort of the eight innovative battery technology companies that completed SPAC mergers between January 2020 and December 2022 produced a similar result. Three have yet to meaningfully commercialize their original battery thesis or have abandoned it entirely. The remaining five have generated product revenue, but none were profitable as of June 2026. Out of this cohort, in FY2025, Enovix, Amprius, and SES AI achieved positive gross margins of approximately 19%, 11%, and 54%, respectively, but remain loss-making, while Eos Energy and ESS Tech ran highly negative gross margins. Notably, large amounts of revenue at companies in this cohort do not indicate full commercial adoption: Solid Power’s 2025 10-K says revenue to date ($77.7M since inception and $1.1M in 2025) has primarily come from R&D licensing agreements, a line-installation agreement with SK ON, and government contracts. Solid Power’s 10-K goes on to describe the company as “a research and development company with no commercial operations.” [5] Across the cohort, none has yet converted its battery technology thesis into both durable commercialization and profitability.

Table 2: The eight innovative battery technology companies that completed SPAC mergers between January 2020 and December 2022, on the same all-in capital basis through August 2026. Three of these companies (QuantumScape, Solid Power, and Amprius) also appear in Table 1. Sources: SEC filings and company announcements. [6]

While these cohorts are small cross-sections, they have raised over $15.8B without demonstrating profitability, and they underscore the same patterns we have seen at Catalus after seven years of doing due diligence on innovative battery startups.

Technical Success Is Not the Bar

The lack of success we are illustrating may contradict the press releases and media statements made by some battery companies, so it is useful to distinguish among the levels of success for a battery startup. For example, several companies in the above cohorts produced functioning batteries, ran pilot plants, supplied product to customers, and deployed product into commercial systems.

For a battery technology company, success can be grouped into four categories:

• Technical success: the chemistry or architecture works under laboratory or pilot conditions.
• Initial commercialization: the company ships samples, small batches, or early commercial units.
• Durable commercialization: the product achieves recurring customer adoption and continuing production.
• Economically sustainable operations: the company can make and sell the product profitably.

Most of the companies analyzed above have reached the first stage, several reached the second, very few reached the third, but none have publicly demonstrated the fourth.

Read the full article: https://www.batterydesign.net/why-battery-startups-fail-developing-technology-vs-shipping-products/

• The Illusion of Progress: Attention from Marquee Companies Is Not Traction
• Why Laboratory Testing Is a Poor Substitute for the Real World
• The Importance of Yield
• The Forgotten Middle: Product 1 Pays for Product 2
• China’s Advantage Is Not Better Batteries
• Conclusion: Batteries Don’t Fail, Strategies Fail

We originally made the A to Z glossary completely free to download as a pdf, but of late we have had a lot of abuse of the system that we use to make it available.

After looking at options the only robust way forward with what we use was to charge a small amount. That just means anyone has to formally use the security of the checkout. Hopefully the $5 is reasonable - would love to know everyone's thoughts on that. My thoughts were that this is the price of a coffee in the UK.

https://www.batterydesign.net/downloads/battery-a-to-z-glossary/

A cell’s vent only has one job: get gas out faster than pressure can build up. How much margin that job has depends on the chemistry. NMC811’s high nickel content is what gives it the energy density in the spec sheet above, but nickel-rich cathodes are also less thermally stable than lower-nickel or LFP chemistries. They start decomposing exothermically at lower temperatures, and once thermal runaway starts, the gas volumes involved are large. Published characterisation work on large-format prismatic cells has measured gas generation rates in the region of several litres per amp-hour of capacity during runaway, internal pressures reaching roughly 200kPa, and vented gas temperatures well above 600°C.^(1) On our own reference page on cell venting, we note that prismatic NCM cells typically actuate around 0.9MPa, against roughly 0.6–0.7MPa for prismatic LFP. NCM already needs a higher-pressure, higher-flow vent than the chemistry most of the industry benchmarks against.^(2)

A single vent sized for an older, lower-energy-density cell can become the bottleneck in that scenario: if gas can’t leave fast enough, pressure keeps climbing, and the failure mode gets worse: case rupture, jetting flame, faster heat transfer into neighbouring cells. That’s the design pressure (literally) that a claim like “dual vent” is responding to.

Photos of the cells settle part of the question before any patent search does. The top cover of each cell carries two separate round vent structures on the same face: not one central vent, and not a cell-to-pack arrangement, but two vents built into a single cell’s cover plate. Each vent sits outboard of its nearest terminal: terminal, then vent, then the edge of the case on one side; the mirror image on the other; the polarity marks and a QR-coded traceability label occupy the space between the two terminals in the middle.

That layout tracks with the cell’s proportions, and it’s the 221.3mm length rather than the width that most plausibly drives it. This is a long, thin can, and a gas-generating event doesn’t necessarily start in the middle: an internal short or localised failure can just as easily originate near one end. If the only vent sat at the centre, gas and heat from an event at one end would have to travel up to roughly 110mm internally before reaching it. Over that distance, there’s a real risk that local pressure builds faster than it can propagate to a vent that far away, and the case wall itself gives way first. Once the case has failed, the vent is irrelevant: gas and particles are escaping through an uncontrolled rupture rather than the engineered path, which defeats the entire purpose of designing a vent in the first place. Putting a vent near each end instead means that wherever along the 221.3mm length an event starts, there’s a relief path close by rather than one a full half-length away.

The cell genuinely has two vents. What’s still open is which of CATL’s patents, if any, covers this specific two-vents-per-cell layout we found the obvious ones and they do make interesting reading: https://www.batterydesign.net/catls-dual-vent-prismatic-cell/

A phone battery looks like a simple, sealed slab. Underneath that, five engineering problems are being fought at once, and each one constrains the others:

1. what the electrodes are made of
2. how fast heat can be pulled out of a space the size of a credit card
3. how the charging circuit routes power without wasting it as heat
4. how the management software decides what the cell is actually capable of
5. what a regulator in Brussels will and won’t let you build

https://www.batterydesign.net/phone-battery-design-in-2026-whats-actually-changing-under-the-hood/

While silicon (SiOx/SiC/Si) based anodes skyrocket battery capacity, their swelling character reaching up to 300% volume expansion transforms cell design from a purely electrochemical challenge into a brutal mechanical packaging problem. It is not just about how much lithium the active material can store; how the casing structurally resists (its rigidity) when that material “breathes” is equally vital.

Structural Rigidity Characteristics of Form Factors

To understand a cell’s response to swelling, one must first evaluate the mechanical stiffness of its outer casing essentially its Elastic Modulus or structural rigidity:

• Cylindrical Cells: The casing is typically nickel-plated steel. Due to the cylindrical geometry and material properties (~200 GPa elastic modulus), its radial rigidity is immense. A cylindrical casing barely yields outward; it acts as an impenetrable wall against expansion.
• Prismatic Cells: Utilize a rigid aluminum alloy casing (~70-80 GPa). While the corners are incredibly stiff, the broad, flat lateral surfaces (parallel to the flat sections of the jelly roll) are structurally weaker. Under internal pressure, these faces tend to bulge outward.
• Pouch Cells: The outer packaging is Aluminum Laminated Film (ALF). Its structural rigidity along the Z-axis (thickness direction) is practically zero. When the internal structure attempts to expand, the pouch offers almost no mechanical resistance.

More....https://www.batterydesign.net/the-form-factor-dilemma-in-high-silicon-anodes-structural-rigidity-porosity-loss-and-plating-risk/

Urban mining is the recovery of metals and minerals not from rock, but from the things we’ve already built, used, and discarded phones, laptops, circuit boards, cars, and increasingly, battery packs. The term was coined in Japan in the late 1980s, a country with almost no domestic mineral reserves but, it turns out, one of the richest “mines” in the world sitting in its own cities.

Japan took the idea seriously enough that by the 2010s its urban stockpile of metals like indium, tin and tantalum accounted for over 10% of world reserves, not mined from the ground, but sitting in drawers, landfills, and recycling centres.

Here’s the fact every urban mining article leads with, and it holds up: there is roughly 100 times more gold in a tonne of old mobile phones than in a tonne of gold ore. Some estimates from the UN put the ratio even higher for the richest e-waste streams up to 800 times the concentration of a good mining ore.

Put in absolute terms: a typical gold mine yields 1-3 grams of gold per tonne of rock. A tonne of shredded circuit boards can yield 250-350 grams. Your old iPhone, individually, holds about 0.034g of gold, 0.34g of silver and 0.015g of palladium. Not much on its own, but multiply that by the roughly 1.2 billion smartphones sold every year and you start to see why “phone recycling” is really a mining operation wearing a lowercase hoodie.

as always, more details and references in the main article https://www.batterydesign.net/urban-mining-the-richest-ore-deposit-youve-ever-thrown-in-a-drawer/

What It Means for Battery Pack Producers

If your battery management system (BMS), the microcontrollers, communication chips, or software that monitor and control a battery pack, is designed, developed, or manufactured by an entity from China, Russia, Iran, or North Korea, it will be illegal to import, manufacture, sell, resell, or introduce into U.S. commerce starting on a fixed schedule: software by January 1, 2027, hardware by January 1, 2030.

This applies regardless of vehicle weight, closing an exemption that currently protects heavy trucks and buses. There is no phase-out for existing designs. Producers need to requalify BMS supply chains against country-of-origin and ownership tests now, not when the bill is enacted.

Timeline

Date	Event
Jan 16, 2025	BIS finalizes the existing Connected Vehicles rule (China/Russia, VCS-focused, BMS excluded, >10,000 lb vehicles exempt)
Apr 29, 2026	S.4429 introduced in the Senate (Moreno/Slotkin)
May 11, 2026	H.R.8730 introduced in the House (Moolenaar/Dingell)
Jul 3, 2026	India orders removal of Chinese BMS apps after e-rickshaw remote-shutdown incidents
Jul 15, 2026	Senate Commerce Committee marks up and unanimously advances S.4429
Jul 22–23, 2026	Bill status confirmed advancing; full Senate floor vote and three House committees (Energy & Commerce, Ways & Means, Foreign Affairs) still pending
Jan 1, 2027	If enacted: ban on covered software (including BMS software) takes effect
Jan 1, 2027	Secretary of Commerce must publish initial list of authorized items and establish request-for-authorization procedure
Jan 1, 2030	If enacted: ban on covered hardware (including BMS electronics/comms components) takes effect; repair/warranty exception applies only to pre-model-year-2030 vehicles
Jan 1, 2032	Existing BIS authorizations issued before 2030 expire unless renewed; Commerce must complete rulemaking on whether to continue prior exclusions

We have pulled together a more complete overview with references if you want to read deeper: https://www.batterydesign.net/connected-vehicle-security-act-of-2026/

This is going to be quite a shake up for the BMS suppliers from China and will open up a lot of opportunities for UK, EU and USA based companies.

We thought it would be useful to create a tool that allows you to find the closest benchmark battery pack to your requirements.

Instead of scrolling through spec sheets trying to eyeball a match, you punch in what you actually need — usable energy, voltage window, max weight, max dimension, peak and continuous discharge power — and it searches our benchmark database of ~1,900 real production and prototype packs to show you two results: the closest pack that falls just short of your spec, and the closest one that meets or exceeds it.

A few things worth knowing about how it works:

• You don't have to fill in every field — leave anything blank and it's ignored.
• Energy is the one mandatory field once you set a target: a pack has to actually report a number for it to show up.
• Max voltage is treated as a hard cutoff (more than 5% over and it's out) since exceeding it is a compatibility problem, not just "a bit big." Energy/voltage/power minimums get a bit more slack — up to 10% under still shows up as a "marginal" match worth a look.
• You can optionally pick one spec as the "primary" if there's one dimension you care about most, and it'll weight the ranking toward that.

It's free to use, no sign-up: https://www.batterydesign.net/closest-fit-to-a-battery-pack/

Built it because we kept doing this comparison for our own projects and figured others might find it useful too. Let us know what's missing or what you'd want it to do differently.

Closest Fit to a Battery Pack

We designed a tool that finds you the closest match to your requirements, thus allowing you to find a benchmark. Perhaps we should have called it "Battery Pack Match Making" https://www.batterydesign.net/closest-fit-to-a-battery-pack/

It also shows you the 2nd closest fit, just in case.

Even better, play around with your requirements and see what happens if you remove some of them.

We thought we would put our database to good use and create a battery pack charging calculator https://www.batterydesign.net/ev-pack-charging-time/

The naive way to estimate charge time is energy needed ÷ peak power. That’s wrong by a wide margin, because peak power is rarely sustained for more than a narrow band of state of charge. To model the actual taper, we pulled every Electric Vehicle pack in the Battery Pack Database that had both a quoted peak charging power and a published 10–80% charge time, around 700 entries, and used the ratio between quoted peak power and the average power implied by the real charge time as the calibration target.

Two things fell out of that analysis:

1. The ratio of average-to-peak power over a 10–80% window sits at roughly 0.65–0.70 across the dataset, packs simply don’t hold their headline number for long.
2. The ratio isn’t constant: it correlates with a pack’s implied C-rate (peak kW ÷ usable kWh). Packs rated below about 1.5C typically sustain 75–85% of their peak; packs above 2.5C typically sustain 55–65%. Higher-C-rate designs are pushed harder relative to their own peak, so they taper away from it faster.

The calculator encodes this as two reference curves per chemistry. A “flat” curve calibrated against low-implied-C-rate packs and a “steep” curve calibrated against high-implied-C-rate packs, blended by the pack’s own peak-kW-to-kWh ratio. A 150kW pack on a 90kWh battery (1.7C) gets a noticeably flatter curve than the same 150kW on a 45kWh battery (3.3C), which matches what the database shows.

We layer onto this: Chemistry, Temperature, Voltage and Cooling.

The electrolyte is not the source of the battery’s energy; it is the highway that energy-carrying ions travel on. If this highway closes down under cold operating conditions (meaning ions cannot be transported), the cell’s internal resistance skyrockets. Before the battery even gets a chance to draw its nominal current, the voltage instantly crashes to the cut-off limit, and the system shuts down. Author: Kerem Batuş

Why is going below -20°C like hitting a thermodynamic and kinetic brick wall?

1. The Glass Transition Boundary: No matter how perfectly you tune the solvent cocktail, the transition from a liquid to a “thick gel phase” begins around the -20°C mark. The liquid might not crystallize into solid ice, but it becomes so incredibly viscous that lithium ions (Li+) simply cannot squeeze their way through the solvent molecules.
2. Desolvation Energy (Trapped Ions): A lithium ion doesn’t travel naked through the liquid; it wears a heavy “solvation shell” made of solvent molecules. To intercalate into the graphite anode, it must first strip off this armor—a process called desolvation. At -20°C, there is not enough thermal energy left to break this shell, making it impossible for the ion to overcome the Charge Transfer ($R_{ct}$) resistance.
3. Fatal Lithium Plating: If you try to charge or aggressively discharge a cell against such massive resistance, the ions cannot enter the anode. Instead, they pile up on the anode’s surface as metallic lithium. This is not just capacity loss; it is the birth of lithium dendrites that will eventually pierce the separator, causing a hard short circuit and a potential thermal runaway.

https://www.batterydesign.net/designing-batteries-for-winter-why-the-electrolyte-is-everything/

A bit of a catch up here explaining the changes in each generation of LFP, hopefully it's interesting.

Our 4th generation LFP post set out the core idea behind LFP “generations”: it’s overwhelmingly a compaction density story applied to the same LiFePO₄ crystal, not a chemistry change, with each generation defined by tighter particle grading, different precursor routes, and progressively higher powder/electrode packing density.

5th generation LFP continues the compaction-density trajectory (≥2.70 g/cm³ powder compaction, up from 4th gen’s ~2.6 g/cm³) using the same particle-gradation mechanism, now delivering a confirmed ~205 Wh/kg at cell level from two independent manufacturers (CATL, Gotion) alongside faster charging (4–5C) and longer claimed cycle life.

What it does not have, as of the current public record, is an unambiguous silicon-anode confirmation on either flagship product. CATL’s “3D honeycomb material” and Gotion’s silicon-carbon capacity build-out both point toward anode-side innovation being part of the story, but neither manufacturer has stated plainly that their headline 5th-gen LFP cell uses a silicon or silicon-carbon anode. Worth flagging as an open question for a follow-up once primary technical disclosures (rather than conference-announcement press coverage) become available.

More details around CATL and Gotion's 5th Gen: https://www.batterydesign.net/5th-generation-lfp/

4th generation LFP is not a new chemistry. It’s the point at which powder compaction density (~2.6 g/cm³) and electrode compaction density (~2.80 g/cm³) required particle-gradation engineering, a shift toward the ferrous oxalate precursor route, and materially tighter purity and process control than earlier generations. The payoff is cell energy density in the 200–205 Wh/kg range with genuine 4C fast-charging capability.

Generation	Powder compaction density	Electrode compaction density	Approx. cell energy density
2nd gen	~2.4 g/cm³	—	—
3rd gen	~2.5 g/cm³	~2.65 g/cm³	~180–200 Wh/kg
4th gen	~2.6 g/cm³	~2.80 g/cm³	~200–205 Wh/kg
4.5 gen (transitional)	~2.65 g/cm³	~2.80 g/cm³	—
5th gen (emerging)	≥2.70 g/cm³	—	—

However, the production barrier this creates has concentrated capability in a small number of Chinese suppliers, making the supply chain dynamics arguably as important to track as the material science itself.

Note: The graph shows Real-world LFP cell data (gravimetric vs. volumetric energy density) with the approximate generation bands overlaid. These boundaries are indicative, mapped from industry-cited compaction density figures onto Wh/kg, not confirmed per-cell generation tags.

Full article: https://www.batterydesign.net/4th-generation-lfp/

We are already into 5th Gen LFP and hence this is a bit of a catch up article, we will expand on that subject next - please do let me know what you think and where we should dig deeper.

Having spent a lot of time working for a large vehicle OEM on battery research through to pack design I wanted to create a useful place to share knowledge and data, that is BatteryDesign.net

Then I thought how good it would be to create a glossary and turn that into a book. I'm of the age that I still like an actual paper book that I can add notes to etc. To that end I pulled this together and it's available from Amazon https://www.amazon.co.uk/dp/B0H7CMPPJX

Have tried to keep the price as low as possible at £14.75 (less than $20) and it's printed in color with lots of graphs and illustrations.

A new paper paper, led by Cambridge in collaboration with WMG, Oxford and Sydney (Wang et al., Nature Energy, 2026) has a decent go at answering exactly that, for a Gr‖NMC811 pouch cell, and I think it’s worth a proper look because a couple of the numbers land uncomfortably close to home.

Heng Wang, Rui Wang, Christopher A. O’Keefe, Erik Björklund, Daniela Proprentner, Joe C. Stallard, Hwee Jien Tan, Wesley M. Dose, Louis F. J. Piper, Robert S. Weatherup, Angkur J. D. Shaikeea, Clare P. Grey & Michael De Volder, The interplay between stack pressure, mechanical expansion and degradation pathways in lithium-ion batteries. Nat. Energy (2026).

My review: https://www.batterydesign.net/whats-the-right-stack-pressure/

Finally made it into print, took a few weeks of graft to get here, but it's now available on Amazon https://www.amazon.co.uk/Z-Battery-Design-Nigel-Taylor/dp/B0H7CMPPJX?_encoding=UTF8&dib_tag=se&dib=eyJ2IjoiMSJ9.usQPUSXD7HdGyRvI5Eg4aThIl_j85ALRSWw-9cVUe18.VGfXee2u_cgX0E4Mq2HHngKMCOk52Z6IrhxoCowHrWU&qid=1783343793&sr=8-1&linkCode=ll2&tag=glueitcomthehome&linkId=38751a00244757b498529169fedb407a&ref_=as_li_ss_tl and I have kept the price as low as possible £14.75

If you want the electronic version as a pdf then that is still available: https://www.batterydesign.net/downloads/battery-a-to-z-glossary/