The battery everyone’s been waiting for, and no one has to wait for any longer.

For years, solid-state batteries have been described as the holy grail of EV technology. Better range, faster charging, improved safety, longer lifespan.

The catch was always the same: they were perpetually five years away. Now something interesting has happened. Chinese automaker SAIC has started delivering the MG4 with a semi-solid-state battery to actual customers. Not a concept car. Not a limited run for testing. Real vehicles, at a price point that undercuts most compact EVs on the market.

This matters because semi-solid-state represents a genuine stepping stone. Full solid-state batteries remain difficult and expensive to manufacture at scale.

Semi-solid-state sits in the middle ground, keeping some liquid electrolyte while reducing it dramatically. The MG4’s battery contains just 5% liquid electrolyte compared to conventional lithium-ion cells. That’s enough of a change to unlock some of the benefits without the manufacturing headaches that have plagued full solid-state development.

The infographic below provides a comparison of semi-solid state vs lithium-ion batteries:

Semi-solid state battery infographic, a comparison of semi-solid state vs lithium-ion batteries — The infographic below provides a comparison of semi-solid state vs lithium-ion batteries

What makes a battery semi-solid

The illustration below shows the different inner workings of lithium-ion and semi-solid state battery technologies, with a direct demonstration of the internals:

A conventional EV battery uses liquid electrolyte to carry lithium ions between the anode and cathode during charging and discharging. This liquid is flammable. It’s also one of the reasons batteries can experience thermal runaway, the chain reaction that leads to fires.

Solid-state batteries replace that liquid entirely with a solid electrolyte, but getting solid materials to conduct ions efficiently and interface properly with electrodes has proven extremely difficult at production scale.

Semi-solid-state batteries reduce the liquid content without eliminating it completely. The MG4’s pack uses a manganese-based lithium-ion chemistry with that 5% liquid electrolyte figure. The result is something that can be manufactured using adapted versions of existing production equipment while still delivering measurable improvements in safety and longevity. The tech is different to Nissan’s, which plans to put solid-state batteries in cars by 2028.

The illustration below shows the transfer of power from a semi-solid state battery to an electric car, helping you visualise how it all comes together:

The safety case

SAIC has been pushing the safety angle hard. The company claims its semi-solid-state battery passed needle penetration tests with no smoke, no fire, and no explosion after two hours. Needle penetration is one of the most aggressive battery safety tests.

A metal spike is driven through the cell to simulate a catastrophic internal short circuit. Most conventional lithium-ion cells fail this test dramatically.

Reducing the liquid electrolyte content directly addresses one of the main fire risks in EV batteries. Less flammable material means less fuel for a thermal event. It doesn’t eliminate risk entirely, no battery chemistry does, but it shifts the probability curve in the right direction.

Cycle life is the other claimed improvement. Semi-solid-state cells are expected to degrade more slowly over repeated charge and discharge cycles. For EV owners, that translates to better battery health after years of use and potentially higher resale values down the line.

What the specs actually show

The MG4 with semi-solid-state battery has a 53.95 kWh pack paired with a 120 kW motor. CLTC range is rated at 530 km, which translates to roughly 330 miles on the Chinese test cycle. Real-world European figures would be lower, probably somewhere around 260-280 miles depending on driving conditions. The electric car kWh per mile is likely to be slightly better.

Charging speed is quoted as 30-80% in 21 minutes using 2C fast charging. That’s competitive but not exceptional. The current generation of conventional lithium-ion batteries in cars like the Hyundai Ioniq 6 can match or beat those figures. Energy consumption is listed at 11.9 kWh per 100 km, which is efficient for a car of this size.

The honest assessment is that this first semi-solid-state production car doesn’t deliver a dramatic leap in headline performance. Range and charging speed are comparable to existing technology. The gains are in safety, durability, and the groundwork being laid for future improvements.

Why this matters more than the specs suggest

The significance isn’t the battery. It’s the factory. QingTao Energy, the startup supplying these cells, is now producing semi-solid-state batteries at scale for a mass-market vehicle.

That’s the breakthrough. Getting exotic battery chemistry out of the lab and into volume production has been the stumbling block for the entire industry. Toyota has been promising solid-state for years. QuantumScape has been working on it for over a decade. Chinese manufacturers have now shipped a product.

The next few years will be about refining the manufacturing process. As production scales up and yields improve, costs will come down. As costs come down, manufacturers can either reduce prices or pack in more cells for greater range. The technology will improve in lockstep with the manufacturing expertise.

This is the same pattern that played out with lithium iron phosphate batteries. LFP was once considered too energy-sparse for serious EV applications. Chinese manufacturers spent years optimising production. Now LFP is the dominant chemistry for affordable EVs worldwide.

The price question

In China, the semi-solid-state MG4 costs around 102,800 yuan, roughly £11,500. The standard LFP versions start at 68,800 yuan, about £7,700. That’s a premium of around 50% for the new battery technology.

Chinese prices don’t translate directly to European markets. Import duties, shipping costs, and local taxes push figures up substantially. The current MG4 in the UK starts at around £26,995. If the semi-solid-state version arrives in Europe, expect a significant premium on top of that.

Whether that premium is worth paying depends on priorities. If longevity and safety matter more than upfront cost, the new chemistry could make sense. For buyers focused purely on value per mile, conventional batteries remain the pragmatic choice for now.

Cold weather performance

One area where semi-solid-state batteries could offer genuine advantages is cold weather operation. Conventional lithium-ion cells lose significant capacity when temperatures drop. The liquid electrolyte becomes more viscous, slowing the movement of ions and reducing both range and charging speed.

Semi-solid-state chemistry should be less affected by temperature extremes. With less liquid to thicken in the cold, ion transport remains more consistent. For EV owners in Scandinavia, Scotland, or anywhere that sees proper winters, this could be more meaningful than any improvement in laboratory range figures.

Real-world cold weather data from the MG4 semi-solid-state is still limited. The cars have only just started reaching customers. Winter testing results over the coming months will reveal whether the theoretical benefits translate to practical improvements.

What about weight

Higher energy density is one of the main promises of solid-state battery technology. More energy stored per kilogram of battery weight. For EVs, that means either longer range with the same size pack or equivalent range with a lighter, more agile car.

The MG4’s semi-solid-state pack doesn’t appear to deliver a significant weight advantage over conventional alternatives with similar capacity. This first generation is focused on proving the manufacturing process works rather than maximising energy density. Future iterations should improve as the technology matures.

Some industry observers expect manufacturers will use any weight savings to fit smaller, cheaper packs while maintaining current range figures rather than pushing for longer distances. A 250-mile EV that weighs 300 kg less would handle better, accelerate faster, and cost less to produce than the current generation.

The competition

Nio has been offering a 150 kWh semi-solid-state battery pack through its battery swap stations for several years. The difference is Nio sells premium vehicles at substantially higher prices. The MG4 puts similar technology in a compact hatchback aimed at mainstream buyers. That’s the shift.

Other Chinese manufacturers are watching closely. CATL, the world’s largest battery producer, has its own semi-solid-state development underway.

BYD is almost certainly working on the same. Whichever company cracks affordable mass production first gains a significant competitive advantage.

European and American battery manufacturers are further behind. They’ve focused resources on scaling conventional lithium-ion production to meet immediate demand. Playing catch-up on semi-solid-state technology while maintaining existing output will be a challenge.

When will it reach the UK

The new MG4 is confirmed for European markets in 2026. Whether that includes the semi-solid-state variant remains unclear. SAIC may choose to focus on higher-volume conventional battery versions initially, reserving the new technology for a later phase or a higher-spec model.

If the European launch does include semi-solid-state, expect it to sit at the top of the range with premium pricing. Early adopters willing to pay for the latest technology will be the target market. Broader availability at more competitive prices will depend on how quickly manufacturing scales.

The road to full solid-state

Semi-solid-state is a waypoint, not a destination. The ultimate goal remains batteries with no liquid electrolyte at all. Full solid-state promises higher energy density, faster charging, and even better safety. The challenge is manufacturing cells that can survive thousands of charge cycles without the solid electrolyte cracking or losing contact with the electrodes.

China is now targeting 1,000 Wh/kg solid-state cells. For context, current lithium-ion batteries manage around 250-300 Wh/kg. That’s a three to four times improvement in energy density. Achieving those figures at production scale would transform what EVs can do.

Semi-solid-state production provides the stepping stone. Manufacturers learn to work with new materials and processes at volume. Each generation incorporates less liquid electrolyte. Eventually, the technology arrives at full solid-state through incremental improvement rather than a single revolutionary leap.