Doom is much more than a classic, bloodsoaked first-person shooter known for its chaotic action, over-the-top weapons, and challenging boss fights. For some odd (but very enjoyable) reason, it’s served as a benchmark for testing basic computing capabilities for well over 30 years. Name a device——calculators, ATMs, digitally enabled tractors, and even biochips built with E. coli bacteria—and someone has likely coded it to run Doom.
The latest entry in the ever-growing list of Doom compatible contraptions is a double-dose of DIY ingenuity, however. The Linux software engineer known as Miss Molerat recently began tinkering with a pocket-sized medical gadget made specifically to keep track of her menstrual cycle. But unlike many similar commercial products, “Clotty” keeps all personal data strictly on the device itself. It never connects to an external cloud or offloads sensitive information to a company’s servers, thereby preventing any unwanted data harvesting. And it does all this on a custom, uterus-shaped minicomputer running on a Raspberry Pi microcontroller.
Clotty includes a Tamagotchi-like sprite players must maintain and keep happy. Credit: Miss Molerat
“I have one thing that has been bothering me for as long as I’ve been menstruating: despite my cycle being very regular, I somehow manage to get surprised by PMS each and every month anew,” Clotty’s inventor wrote on her website’s blog.
Clotty “does the boring stuff” for her by tracking her period via a Tamagotchi-like digital pet that requires attention and maintenance throughout each month. The pixelated creature’s mood shifts depending on the cycle phase, but it also can go on little quests and offer various minigames in the meantime.
“[It’s] basically some sort of adorably shaped mirror version of my own moods that serves as a reminder that I, too, am just some sort of creature that tries to stay alive and happy,” explained Clotty’s creator.
But why stop there? Clotty is powerful enough to run Doom on its itty-bitty LCD screen, which is thematically perfect given the project’s overarching, bloody motif. This means that, when not keeping up with personal health, a user can also blast through wave after wave of space demons using small onboard sensors.
The inventor admitted that Clotty is still in its “fetal stage,” but she plans to add more features like a menstrual cycle history archive, more games, and even some reproductive health trivia. It’s also a completely open-source project, so anyone can follow her online tutorials and download files for Clotty (and Doom).
California is known for its giant, multi-laned highways bustling under bright blue skies. And while this infrastructure is useful to humans, the Golden State’s many highways represent an almost impenetrable barrier for wildlife.
Wildlife crossings are structures that help animals safely cross roads. In the United States, collisions between motorists and large animals take place more than a million times a year. Experts estimate that this results in 400 human deaths every year. But the problem isn’t just road accidents. Habitat fragmentation is also a concern, especially for species that require a large range. Inbreeding can occur if a small enough group of animals becomes isolated.
In the Los Angeles area, mountain lions (Puma concolor), also known as pumas or cougars, are currently the species most vulnerable to genetic isolation caused by roads and development, according to the project’s website. And the 101 Freeway appears to be the most important obstacle, out of all the roads in the area, to the region’s ecological health.
Some of the many species that will benefit from the crossing. Image: Living Habitats/Wallis Annenberg Wildlife Crossing
As such, the Wallis Annenberg Wildlife Crossing aims to reconnect local plants and animals in the ecosystem of the Santa Monica Mountains. It’s about 210 feet long and about 170 to 174 feet wide. A thick, sturdy-looking vegetation-covered bridge already straddles the busy freeway—but the weather might throw a wrench in the project’s schedule.
“We’re just hoping El Niño‘s on our side,” Beth Pratt, president of the Wildlife Crossing Fund, tells the Los Angeles Times, in reference to the climate pattern that typically brings wetter winter weather along the United States’ southern border. Flooding would put work on pause, according to the outlet. “I keep saying, ‘Mother Nature, we’re trying to help you. Let’s not throw any more complications our way.’”
The scams are getting a bit meta. The Federal Trade Commission (FTC) has issued a warning about a new scam currently making the rounds. But this time, the con artists aren’t impersonating a politician or celebrity to trick consumers.They’re claiming that they are the ones sounding the alarm at the FTC.
Real FTC officials explained the general scheme in an alert released on October 22. Scammers call a target to tell them that bad actors in another country have registered a separate phone using their name and number for nefarious purposes. The imposter may even “transfer” you to a fake police officer to file a report. Fake badge numbers and IDs are also offered to make it all sound legitimate, and skeptics may even be directed to verify everything by searching for the police department’s phone number online (also fake). Failure to comply allegedly results in the loss of your personal phone number.
Those who follow through with the instructions provide scammers with their state-issued ID and other personal info for the bogus police report, but it’s not over yet. Some time later, targets will receive another call informing them that they will soon be arrested for those nonexistent crimes committed using their phone number. The solution? Transfer money for a security deposit.
“None of this is true—it’s all a scam,” assured the FTC.
To prevent unnecessary headaches, the FTC listed a few ironclad rules. Actual FTC employees will never contact you about sending money, or transfer you to someone else requesting funds. The FTC will never threaten to disconnect your phone number, or ask you to keep your conversations secret from others. Finally, they will never text a photo of the supposed employee ID as a way to verify their identity to you.
Unfortunately, combatting scammers is a bit like playing a neverending game of Whack-a-Mole. While the FTC has a list of common ways to spot government imposters, they encourage everyone to report the latest con jobs to ReportFraud.ftc.gov.
When it comes to buying a home, many people pay a premium for privacy. But one new listing Carlton, Kansas, takes the cake. For a measly $1.6 million, someone can call a converted Cold War Atlas intercontinental ballistic missile (ICBM) silo home. Though the site sits on 18.2 acres of rural grassland, nearly the entire complex is hidden underground, save a single ominous steel door. The silo trenches down 182 feet, eventually leading to a two floor launch control center retrofitted to fit the modern world.
Surrounding the entire complex are 600 tons of steel rebar and six-foot-thick epoxy concrete walls meant to withstand nuclear blasts and 500 mph winds. The listing’s website calls it quite possibly “one of the most hardened structures ever built by man.” Once the staging ground for nuclear Armageddon, the indoor launch control center has been converted into a 2,200-square-foot, two bedroom, two bath, home outfitted with generic modern appliances. To top it all off, it is caked in a fresh coat of muted millennial gray and white paint.
The only clear sign of the bunker above ground is a single metal door. Image: North Star Missile Silo
From launch control to living room
This particular missile silo was part of the United States Air Force’s Atlas F Intercontinental Ballistic Missile Program. The Atlas program began toward the end of World War II, and produced the country’s first operational ICBM. At its peak, from late 1962 to mid-1964, 132 of these Atlas sites were built around the country.
According to the National Park Service, north-central Kansas’ Atlas F was “by far the best” of the Atlas variants ever deployed. The missile stood 82 feet tall and carried a 4.5 megaton warhead, roughly 300 times as powerful as the 15-kiloton bomb dropped on Hiroshima. Aside from the Kansas location, there were 72 Atlas missile sites stationed on bases in Nebraska, Oklahoma, Texas, New Mexico, and New York.
Though advanced for its time, the Atlas was soon eclipsed by the even stronger Titan and then Minuteman systems.The majority of the Atlas systems were decommissioned in 1979, when President Richard Nixon signed the SALT (The Strategic Arms Limitation Talks) treaties. That meant dozens of the massive structures were left dormant. Many of those relics have taken on new lives as luxury apocalypse bunkers or gimmicky rentals.
A 40 foot underground tunnel connects the retrofitted launch control to the missile silos. Image: North Star Missile Silo.
A buyer interested in viewing the North Star Missile Silo in Kansas would really have to know what they’re looking for. Getting there requires driving through a seemingly nondescript stretch of grassland before eventually coming up on a large gated fence with the iconic yellow “Fallout Shelter” signage on its side. Once inside, a surreal-looking steel door jutting out of the quiet countryside offers a clue to the shelter. It looks like a portal to some eerie, distant world, which, in some sense, it really is.
Once through the door, visitors descend a metal staircase that leads to a 40-foot tunnel. Photos show a narrow, claustrophobic walkway encased in a ring of white metal beams. At the end of the walkway stands a pair of imposing 7,000-pound blast doors. Home sweet home!
But the weirdest part about the retrofitted missile silo house is how remarkably normal much of it looks on the inside. The living quarters feature a floor plan with two bedrooms, two kitchens, and two bathrooms spread across two floors. Stainless steel appliances and a washer and dryer sit alongside standard wooden cabinets, none of which would look out of place in any hastily built rental unit across the country. The central area is laid out loft-style, showing off the control center’s massive support column. Visually, everything seems out of context. It evokes a slightly off not quite right AI-generated version of a house, or a modern millennial apartment that a visiting alien might describe to fellow interstellar travelers.
The loft style interior is built around the control’s center’s missive support column. Image: North Star Missile Silo.
It’s an undeniably weird place to live full time, but not a half-bad survival bunker. The listing notes that it features two separate sewage systems (one above ground and one underground) humidity control, a cellphone phone signal repeater and a solar power powered seven foot chain link gate. It also has ample room for solar or wind energy installation, though the buyer would have to install those. It’s also not necessarily limited just to survival or end time doomers. Realtor.com notes that the silo was previously used as a rental, though he also said there was interest in using it as an off-the grid conference site or even a wedding venue.
A new era of fancy bunkers
Many Cold War relics have taken on new lives as quirky rental and luxury condominiums. Airbnb shows a number of silos available for short term stays in New Mexico, Kansas, and southern Texas. Some of these explicitly court “prepper” audiences with fat wallets. Possibly the best known of those is Survival Condo, located about 200 miles outside of Kansas City, That sprawling Atlas Missile Silo was converted into a 15 floor luxury condominium outfitted with a pet park, climbing walls, swimming pool (with a slide) library and a movie theater. The starting asking price for one of the units? Around $1 million in 2020 dollars.
And while Cold War bunkers are relics of the past, new interpretations of the structures are still being built. In the U.S. and abroad (New Zealand attracts a particular amount of attention) a subset of the world’s wealthiest elites are reportedly constructing their own apocalyptic lairs. Some of the best known examples of those billionaire bunker builders are in the tech industry with some racing to build advanced AI models that are increasingly putting them at odds with public opinion. Aside from escaping the pitchforks, the Kansas listing also notes one more potentially enticing incentive.
“Underground structures not taxable by [the] County.”
Fall is here, and with it comes very determineddeer. Mating season for the hoofed ruminants typically begins once temperatures dive and the days grow shorter, but the annual event also poses problems for humans. The deer have one thing on their mind, which means they pay even less attention to vehicles and roadways. In New Jersey, roughly 41 percent of all annual animal collisions occur between October and December, while the AAA Foundation for Traffic Safety routinely tallies over 275 fatalities from similar accidents nationwide every year.
Driving gets even riskier in rural areas, which frequently host higher deer populations and much darker roads. However, a recent pilot program in Virginia offers a promising tool that may keep commuters safe while also allowing the animals to do their thing. At the Virginia Tech Transportation Institute (VTTI), researchers designed an automated digital roadside sensor system that warns drivers of large jaywalkers like deer and elk.
According to VTTI engineer Shreyas Bhat, the year-long trial demonstrated a “measurable change” in how local drivers responded when alerted to oncoming wildlife. Bhat and his colleagues tested the system with help from the state’s Department of Transportation along a 14-mile section of Route 460 in southwest Virginia. The array was composed of eight portable, solar-powered trailers and customizable digital message signs. Each station included thermal cameras analyzed by onboard machine learning software, which triggered the sign alerts whenever it flagged nearby medium– to large–sized animals.
Over the course of the trial, researchers amassed driving data on over 10,000 vehicles, while the detection system maintained an estimated accuracy of around 97 percent. This is particularly impressive given the region’s environmental and infrastructural challenges.
“This system is unique because of the requirements of the area—it needed to be solar powered, portable, and be able to withstand all weather conditions,” explained VTTI engineer Jean Paul Talledo Vilela.
The team reported an average reduced speed of about three miles per hour thanks to the roadside warning signs. That may not seem like much, but even a slight slowdown can save lives. It also proved people took note of the system.
“Speed is an important data point to understand if drivers were actually paying attention to the message board,” said Talledo Vilela. “Even if they are not braking aggressively, some reduction in speed indicates that they may be paying more attention to their surroundings because they got that alert.”
While Talledo Vilela, Bhat, and their collaborators are still parsing through data from the program,(it ended in September) the initial findings remain promising. From here, the team hopes to refine the overall system while organizing future trials in other regions of the country. If successful, the relatively simple installations could also be adapted for other year-round road safety situations like construction or real-time weather hazards.
Early iPhone Duo reviews are examining how Apple’s first foldable handles everyday tasks ahead of its October 23 launch. Reviewers describe an appealing inner display alongside adjustments involving one-handed use, authentication, and app layouts, providing a practical picture of where the design works well and where it asks users to adapt.
Evaluations published October 21 offer a more substantial picture than brief demonstrations, ahead of initial retail availability on OctobeIn a September 19 hands-on, Android Central’s Harish Jonnalagadda also highlighted the inner display’s coating. Those earlier impressions provide context for the October reviews, but came from a shorter session rather than extended everyday use.r 23. The emerging story combines an appealing inner display with practical questions about handling, applications, and the compromises involved in carrying one device that serves two roles.
The Matte Display Changes the Experience
The inner screen’s finish is becoming one of the most consistent points of interest. Apple’s official announcement describes a nano-textured polymer cover intended to reduce glare and minimize the visibility of the fold.
In his PetaPixel review, Jaron Schneider praises the reduction in reflections and says fingerprints are much less noticeable during normal use. He also acknowledges that people who dislike matte displays may not appreciate this one.
In a September 19 hands-on, Android Central’s Harish Jonnalagadda also highlighted the inner display’s coating. Those earlier impressions provide context for the October reviews, but came from a shorter session rather than extended everyday use.
That gives the comparison with existing foldables a more useful starting point than screen size alone. A larger panel matters less if reflections repeatedly interfere with what someone wants to see. Equally, a finish that one reader finds comfortable may disappoint someone who prefers the appearance of glossy glass.
The relevant difference is therefore partly experiential. Shoppers should examine text, photographs, and dark scenes under several lighting conditions rather than judging the screen from a promotional image.
Image Credit: Apple Inc.
A Folding Phone Still Has to Work Closed
Schneider’s assessment also exposes a practical tension: he finds the hardware exceptionally well made, yet describes difficulty with one-handed typing and adjusting his grip for Touch ID. His experience favors using both hands.
Those observations should remain attributed to the reviewer. Hand size, preferred grip, and familiarity can produce different reactions to the same device.
Nevertheless, they identify something worth testing before choosing a foldable. The closed phone will still handle quick messages, authentication, and tasks performed while standing or moving. Those interactions deserve as much attention as the impressive moment when the inner screen opens.
A useful demonstration would involve composing a message, reaching frequently used controls, unlocking the device, and then opening it to continue working. Comfort across that sequence reveals more than holding an unfolded phone briefly for a photograph.
Software Makes the Comparison More Complicated
Mark Spoonauer’s October 21 Tom’s Guide review praises the ease of using two applications together, but finds that applications without appropriate optimization can look poor. He also reports that rotating into portrait interrupts the side-by-side layout, which returns when the phone rotates back.
In that specific comparison, he notes that Samsung’s Galaxy Z Fold 8 keeps two narrow app windows visible in portrait.
This illustrates why “supports multitasking” is only the beginning of a useful comparison. What happens when the phone rotates, when someone switches tasks, or when an application encounters an unfamiliar shape can determine whether the extra space feels productive.
The Duo’s Split View limitations become more relevant when they interrupt a task already underway. The review describes a change in layout rather than the loss of the app pair, which returns when the device rotates back to landscape.
Buyers should check the applications they rely on most. A polished demonstration using selected software cannot establish that every banking app, editing tool, or work service will make equally effective use of the display.
Battery Testing Adds a Measured Reference Point
Tom’s Guide recorded 13 hours and 20 minutes in its web-browsing battery test, using the larger display, a 5G connection, and brightness set to 150 nits. The publication says it adapted the test to fill the Duo’s screen and ran it alongside the Galaxy Z Fold 8 and iPhone 18 Pro Max.
In that simultaneous comparison, the Galaxy Z Fold 8 lasted 10 hours and 6 minutes, while the iPhone 18 Pro Max reached 17 hours and 31 minutes. The Samsung phone had previously recorded 12 hours and 19 minutes, illustrating why results from different runs need context rather than being treated as fixed rankings.
The result provides a useful reference, rather than a promise about every owner’s day. It also demonstrates why a single competitive headline can oversimplify testing: the method, screen used, and comparison conditions belong alongside the number.
Image Credit: Apple Inc.
The Strongest Differences Are Practical
These accounts suggest that the Duo’s identity depends on how its screen finish, physical format, and software work together. They also reveal disagreement about whether those benefits outweigh the adjustments. Praise for construction does not automatically resolve concerns about grip or application behavior.
For prospective buyers, the useful question is which compromises fit their routine. Reading comfort, dependable access to work applications, and easy one-handed interactions may carry different weight for different people. The first reviews now provide concrete experiences to investigate, while long-term display and hinge durability still require longer observation.
Ofcom boss Dame Melanie Dawes has admitted today that tech firms have paid just two of the eleven fines handed out under the Online Safety Act since March last year. Giving evidence to the Culture, Media and Sport Committee, she conceded nine remain unpaid, four of the offending sites have simply geo-blocked the UK, and three are still up and running with nothing changed.
American courts have, by now, provided their preliminary view on the likelihood of Ofcom’s enforcement powers being successful in U.S. courts – the obiter dicta in 4chan v. Ofcom, the opinion in the case we filed against Ofcom in the federal District Court for the District of Columbia a little over a year ago.
[…]
Ofcom can’t enforce the Online Safety Act in America. Ofcom knows it, Ofcom has known it for a long time, and now, Ofcom has, finally, admitted it.
[…]
The GRANITE Act, a foreign censorship shield now before both the House and Senate (H.R. 10174 / S. 5478), is one proposed legal response America could adopt. The HOMEFRONT Act, H.R. 10309, is another. Either of GRANITE or HOMEFRONT would strip sovereign immunity from foreign censors and let Americans targeted by their orders drag those agencies into federal court, where they could be held accountable for their actions.
As of iPadOS 27, if you have multiple windows open while AirPlaying (whether or not Stage Manager is on), tapping on anything other than the presenting app will snap the external display into showing your whole iPad screen. This means that my students see all my notes on who I want to call on, or poll results that should be hidden from them. They also get distracted from what we’re learning by all these jarring windows popping up and disappearing. If you’re presenting at a big conference, it’s extremely embarrassing.
[…]
As for what the behavior should be, I’m not a developer, but here’s a proposal: if you’re using an app that is in presenter mode (e.g., PowerPoint playing a presentation, or a GoodNotes document open), it should always get precedence on the external display, until that presentation gets stopped, the document is closed, or the app is quit.
Viruses are sneaky intruders, hijacking the internal machinery of host cells and replicating out of sight. Understanding these dynamics is the first step to developing effective antiviral strategies that could stop infections, but scientists have largely been left in the dark because there are limited tools to study how viruses move in space and time inside live infected cells, according to Joyce Jose, associate professor of biochemistry and molecular biology at Penn State.
Scientists have proposed what they believe is the first method for detecting "mirror life"—a hypothetical form of life made from molecular building blocks that are the mirror image of those found naturally on Earth. Researchers at the University of Strathclyde and the Department of Chemistry at Durham University have outlined a new approach that could identify mirror organisms using molecules which emit left- and right-handed light.
Southeast Asia has 243 million generative AI users, but paid adoption remains low. Businesses now face the challenge of turning widespread usage into revenue through enterprise tools, AI-powered commerce, and infrastructure investment.
With You Can See Everything, Holmes joins other such high-profile subjects as Lance Armstrong, Imelda Marcos and Anthony Weiner to allow film-makers to document their lives. But do they ever come out well?
In You Can See Everything, convicted fraudster Elizabeth Holmes invites film-makers Nathan Fielder and Lance Oppenheim into her home in a supposed act of “radical transparency”. Holmes is filmed, along with her partner, Billy Evans, and their two young children, in the weeks before starting a prison sentence for defrauding Theranos investors. “The best way for people to see who she is,” Evans says, “is to give as much access as possible into our daily lives”. It may also be the best way to market “Theranos 2.0”, which the couple are working on during filming. But the documentary questions whether Holmes is presenting her authentic self or a manufactured persona. Fielder speaks for the audience when he asks Holmes in a tense exchange whether she’s “being real” with him. “I’m always being real,” she says.
That question of authenticity is at the heart of documentary film-making. You Can See Everything is as much about the ambiguous relationship between film-maker and subject as it is about Holmes herself. There is often a power struggle over narrative control in documentaries, with both sides of the dynamic wanting different outcomes from the final film. Watching You Can See Everything inevitably prompts the question: why would Holmes, days before she heads to jail, invite the scrutiny of a film crew?
After months of controversy over the possible use of AI by winners of prestigious awards, the Prix Pascal de Littérature IA is rewarding fiction written with the help of LLMs
A prize for AI-written books has launched this week.
The Prix Pascal de Littérature IA invites submissions of manuscripts co-written with AI tools, with the winner promised publication.
Apple is recruiting a 6G cellular modem systems engineer, adding a next-generation research focus to its in-house modem development. The position, posted October 19 in Sunnyvale, California, describes responsibilities spanning cellular standards, hardware and software architecture, and power efficiency.
The Apple job listing establishes a concrete engineering focus. It does not identify a future iPhone, name a commercial modem, or provide a release date.
That makes the vacancy useful as a window into development priorities rather than a product announcement. The significant detail is how broadly Apple describes the work: connecting emerging standards with the decisions required to build a functioning cellular system.
The Role Connects Research With Product Engineering
The position covers feature definition, algorithm development, simulation, silicon testing, and preparation for production. Apple specifically identifies next-generation modem requirements with a focus on 6G evolution.
The listing also emphasizes translating engineering improvements into throughput, latency, battery life, and connection reliability. Candidates are expected to understand emerging 6G work alongside 5G and 4G standards.
Those responsibilities explain why modem development extends beyond designing a single chip. A cellular system must coordinate signal processing, software, and hardware while operating within a mobile device’s power constraints.
The practical challenge is balancing competing priorities. An approach that improves one performance measure may introduce costs elsewhere, such as greater processing demands. Evaluating those trade-offs is part of turning a technical possibility into something suitable for a portable product.
Image Credit: Apple Inc.
Apple’s 6G References Predate This Vacancy
The October posting is not the first public indication of this research. A separate Apple RF modeling position, dated June 24, includes modeling and simulation for 4G, 5G, and 6G modem systems.
The distinction matters when interpreting the latest recruitment. A newly published vacancy can reveal current responsibilities without establishing when a project began or how much its staffing has changed.
The two roles address different engineering tasks. The RF modeling position focuses on simulating radio-frequency behavior and investigating performance, while the newer systems role connects standards, algorithms, hardware, and software. Together, they illustrate why modem development requires work across several specialties.
The Standards Process Is Still Underway
The wider industry remains in the process of defining 6G. The International Telecommunication Union refers to the next generation as IMT-2030.
According to the ITU’s current development overview, its expert working party completed draft technical performance requirements in February 2026 and draft evaluation guidelines in June. Both documents have been submitted to ITU-R Study Group 5 for approval scheduled for December 2026.
The ITU has also invited proposals for candidate IMT-2030 radio technologies between February 2027 and February 2029. That window concerns submissions for evaluation, rather than consumer launches, and helps explain why companies are recruiting engineers while the technical framework is still taking shape.
These milestones concern how candidate technologies will be specified and assessed. They do not establish a date when a particular operator will offer service or when Apple will ship compatible hardware.
For readers, this is an important distinction between an industry framework and a usable connection. Standards work helps establish common expectations. Commercial availability requires additional decisions and implementation by device makers, network suppliers, operators, and regulators.
The Work Builds on Apple’s Existing Modem Effort
Apple already has experience bringing its own cellular modem to market. The company introduced C1 with iPhone 16e in February 2025, identifying it as its first internally designed cellular modem and a component supporting 5G connectivity.
That C1 announcement provides a commercial reference point for Apple’s modem work. The recruitment concerns a different stage: developing systems around emerging standards. Shipping a 5G modem and researching 6G are related activities, but progress in one does not establish a launch schedule for the other.
It does not establish that the new role belongs to a particular C-series successor. Assigning a name, manufacturing schedule, or specific iPhone generation would go beyond the information available.
What the Vacancy Means for iPhone Buyers
The immediate takeaway is about Apple’s development direction. The company is seeking engineers who can connect emerging wireless standards with practical requirements such as efficient operation and reliable connectivity.
For someone choosing a phone today, the vacancy provides no basis for predicting when 6G will become a useful purchasing consideration. Published device capabilities, local network coverage, and current service plans remain the information buyers can assess.
The more meaningful future milestones will be finalized specifications, announced compatible hardware, and documented operator deployments. Until those arrive, Apple’s recruitment offers evidence of preparation—and a clearer view of the engineering involved—without establishing the features or timing of a future iPhone.
From that fresh paperback smell to the wrinkles in the spine, nothing beats a real book. But if you’re sick of the space they take up in your home, or the weight they steal from your holiday luggage allowance, it might be worth considering an Amazon Kindle. It can fit thousands of weighty reads into as little as 158g, and as tech goes, it’s almost immune to the sort of pathological time-wasting features that come with modern phones and tablets.
Amazon Kindles have been available in the UK for more than 15 years, so they’re an old-school gadget at this point. But in 2024, the biggest update yet arrived: colour, which added an important extra option to the existing Kindle lineup, alongside readers for children, for note-taking and for tighter budgets.
Lithium and sodium are neighbours in the periodic table. Both are alkali metals, both have a single electron in their outer shell, and both can be used to shuttle ions between two electrodes to store and release electrical energy. At first sight, replacing lithium with sodium in a rechargeable battery might therefore seem straightforward.
There are good reasons to try. Sodium is widely available and sodium-ion batteries can rely on electrode materials containing abundant elements such as iron and manganese. But chemical similarity does not mean electrochemical equivalence. A sodium ion is larger and heavier than a lithium ion, and its interaction with the materials surrounding it is different. As a consequence, replacing Li+ with Na+ changes much more than the identity of the charge carrier.
The electrodes have to accommodate a different ion. Their structures may respond differently as sodium is inserted and removed. The electrolyte has to transport and solvate it. New interfaces form between the electrolyte and the electrodes. Even graphite, the standard anode material of most commercial lithium-ion batteries, does not store sodium under conventional conditions nearly as effectively as it stores lithium 1.
A sodium-ion battery is therefore not simply a lithium-ion battery containing a different element. Understanding why requires looking at what happens to sodium once it enters the battery.
Graphite does not play by the same rules
Charging a conventional lithium-ion battery involves moving lithium ions from the positive electrode through the electrolyte and storing them in the negative electrode. Graphite is particularly good at this job. Its carbon atoms are arranged in sheets, and lithium can reversibly occupy the spaces between them, a process known as intercalation. It would be convenient if sodium behaved in the same way. It largely does not.
The poor ability of conventional graphite to accommodate sodium has long been one of the reasons why lithium-ion concepts cannot simply be transferred to sodium-ion batteries. Instead, one of the most widely studied negative-electrode materials is hard carbon 2.
Hard carbon is still carbon, but structurally it is very different from graphite. Rather than a regular stack of extended carbon sheets, it contains disordered graphitic domains, defects and pores. This disordered architecture provides environments in which sodium can be stored, but it also makes the underlying mechanism considerably harder to describe.
Where exactly does the sodium go? Researchers have proposed contributions from adsorption at defects and surfaces, insertion between graphitic layers and storage associated with nanopores. The relative importance of these mechanisms depends on the structure and microstructure of the carbon. This is more than a microscopic detail: where and how sodium is stored determines the voltage profile, reversible capacity, first-cycle losses and, ultimately, the energy that a complete cell can deliver.
Researchers at CIC energiGUNE and collaborators have studied this connection between charge-storage mechanisms, carbon structure and electrochemical performance 3. Their analysis highlights an important point: maximizing the amount of sodium that an anode can store is not enough. The potential at which that storage occurs and the irreversible losses during the first cycle are equally important when the material is incorporated into a full battery.
The problem is therefore not simply to find a carbon that accommodates more sodium. It is to understand how its structure stores sodium and then engineer that structure so that capacity, voltage and efficiency improve together. This has led researchers to explore different ways of controlling hard-carbon structure, including the use of lignocellulosic biomass as a precursor. Work has shown that even apparently simple processing decisions, such as acid treatment of the biomass precursor, can affect the resulting carbon and its behaviour as a sodium-ion anode 4.
And the negative electrode is only half of the problem. At the positive electrode, sodium ions have to repeatedly leave and re-enter a solid structure. Layered transition-metal oxides are attractive candidates because sodium can be reversibly extracted from and inserted into spaces between layers of metal and oxygen atoms. Compositions based on relatively abundant elements such as iron and manganese are particularly interesting 5.
Again, however, accommodating sodium is not enough. The host structure has to survive the process. A useful example is the layered oxide P2-Na₂/₃[Fe₁/₂Mn₁/₂]O₂, investigated by researchers from CIC energiGUNE and collaborators 6. The material can provide high capacity, but its long-term stability strongly depends on the voltage range over which it is operated.
This produces a familiar battery dilemma. Increasing the operating voltage can increase the amount of energy extracted from a material. But pushing the electrode further can also trigger structural transformations that make subsequent cycles less reversible.
The researchers compared cells operating in different voltage windows and combined electrochemical measurements with structural characterization and theoretical calculations. Above approximately 4.0 V versus Na+/Na, the cathode undergoes a high-voltage phase transition. Avoiding this transition improves capacity retention, revealing a direct connection between the structural state of the electrode and its long-term electrochemical behaviour.
Changing the chemical composition can also alter this structural response. In another study, researchers investigated the effect of introducing titanium into sodium manganese-rich layered oxides 7. A certain degree of Ti substitution helped the crystal structure accommodate electrochemically induced strain. Too little was insufficient to stabilize it, while further substitution introduced other destabilizing effects.
Other studies have approached the same problem from a different angle, examining how the precise stoichiometry of P2 layered oxides affects their performance 8, or following their structural evolution under different current rates and dopants using operando techniques 9. The lesson is that there is no single property called “a good sodium cathode”. Composition, atomic arrangement, voltage and cycling conditions are interconnected. Even an element that does not directly provide the stored charge can determine how well the electrode survives sodium repeatedly moving through its structure.
A different chemistry
Layered oxides are not the only possible positive electrodes. Sodium chemistry allows other structural families to be explored.
One particularly instructive example is NaFePO₄, the sodium analogue of the well-known lithium iron phosphate chemistry. Researchers involving CIC energiGUNE have used in situ X-ray diffraction to follow how NaFePO₄ changes during sodium insertion and extraction 10. They have also shown that the reaction mechanism itself depends on how rapidly the electrode is charged or discharged 11.
This is a subtle but important point. We often describe an electrode material as if it had a fixed reaction mechanism. In practice, what happens inside it can depend on how the battery is operated. Computational work has gone further by investigating sodium diffusion in NaₓFePO₄ 12. Combining experiments and modelling in this way makes it possible to connect what is observed at the battery level with the motion of ions through an atomic structure.
But even understanding both electrodes is not enough. Between them lies the electrolyte, and the sodium ion spends much of its journey there. It becomes surrounded by solvent molecules, travels across the cell and eventually reaches an electrode surface. At that interface the electrolyte can decompose, producing a solid-electrolyte interphase, or SEI.
This apparently thin layer can have a disproportionate influence on battery behaviour. Researchers at CIC energiGUNE have investigated both the composition and evolution of the SEI in sodium-ion electrodes 13 and, more broadly, the relationship between electrode-electrolyte interphases, transport properties and electrochemical performance in non-aqueous sodium-ion batteries 14.
The interface illustrates particularly well why changing lithium for sodium is not a simple substitution. The chemistry of the ion influences its solvation, its transport and the decomposition reactions that occur when it reaches an electrode. A material that can reversibly store sodium may still perform poorly if the interface around it continuously consumes electrolyte or sodium during cycling.
This is why sodium-ion research has to consider the cell as a system. Graphite may have to give way to hard carbon. Positive electrodes require structures able to tolerate repeated sodium insertion and extraction. Electrolytes and additives have to create suitable transport conditions and stable interfaces.
And every attempt to solve one of these problems can affect the others.
Sodium is not the new lithium
Lithium has a fundamental advantage that materials engineering cannot simply remove: it is the lightest metal and has a very low electrochemical potential. Sodium is heavier and its electrochemical potential is less favourable, placing intrinsic constraints on the gravimetric energy density that sodium-ion batteries can reach.
That does not necessarily make sodium a worse battery chemistry. Energy density is only one parameter of an electrochemical storage system. Cost, raw-material availability, lifetime, power, safety and operating temperature can become equally important depending on the application. A battery designed for a mobile phone, an electric vehicle or stationary storage does not necessarily have to optimize the same variables. And sodium chemistry itself offers several possible ways of balancing them.
CIC energiGUNE researchers have explored, for example, low-cost phosphate-based cathodes for aqueous sodium-ion batteries 15, Prussian Blue compounds as positive electrodes in aqueous systems 16, alternative sodium layered oxides [5,8,9], hard-carbon anodes [2,3,4] and even materials such as NaTiOPO₄ designed to modify or potentially avoid some of the interfacial problems normally associated with sodium-ion anodes 17.
These are not different routes towards exactly the same battery. They represent different ways of deciding which compromises are acceptable.
This changes the original question. The relevant challenge may not be how to make sodium behave as much like lithium as possible. Research on hard carbons shows that sodium may require a different type of host structure. Work on layered oxides shows that extracting more energy from an electrode can alter its structure and compromise its stability. Studies of NaFePO₄ show that the reaction pathway itself can depend on cycling conditions. And research on interfaces shows that storing sodium reversibly is only part of the problem: the chemistry taking place around the active material matters as well.
Sodium-ion batteries are therefore not lithium-ion batteries in which one element has simply been exchanged for another. Changing the ion changes the materials that host it, the structures they adopt, the reactions they undergo and the interfaces they form.
Sodium may not need to beat lithium at its own game. The more interesting question is whether understanding its different chemistry will allow us to play a different one.
The BRTA is a consortium that remains a step ahead of future socio-economic challenges worldwide and in the Basque Autonomous Community; it addresses them through research and technological development, thus projecting itself internationally. The BRTA centres collaborate to generate knowledge and transfer it to Basque society and industry so as to make them more innovative and competitive. The BRTA is an alliance of 17 R&D centres and cooperative research centres with the support of the Basque Government, the SPRI and the Chartered Provincial Councils of Araba, Bizkaia and Gipuzkoa.
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