雅思阅读 080: The Salt-Powered EV — Sodium-Ion Batteries for Winter

Adapted from "A salt battery could make EVs more winterproof" by You Xiaoying, Scientific American, 3 March 2026.

🎧 课文朗读音频（约 50 秒）

Reading Passage

For electric vehicle owners, watching battery capacity vanish on a frigid morning is a familiar winter ritual. Now a common element found in table salt may hold the key to keeping electric cars running reliably in the cold.

Cars powered by a sodium-ion battery are scheduled to go on sale in China in mid-2026, according to the battery manufacturer CATL, the world's largest producer of EV batteries, and the vehicle maker Changan Automobile. Even if these cars are unlikely to reach Western showrooms soon, the announcement offers an early signal of whether sodium-ion technology can solve one of electric driving's most persistent problems: winter range loss.

CATL's new battery, called Naxtra, can perform stably at –50 degrees Celsius. For drivers in Minnesota, Ontario or Norway, that claim is hard to ignore.

Why Lithium Batteries Struggle in the Cold

Most EVs today use lithium-ion batteries. In warm weather they are powerful and efficient, but cold temperatures slow them dramatically. At –10 degrees Celsius, a typical lithium-ion EV can lose 30 to 40 percent of its range. Charging also slows dramatically, and fast charging in extreme cold can permanently damage the battery.

The reason lies in chemistry. Batteries store and release energy by moving charged particles called ions between two electrodes through a liquid called an electrolyte. In cold weather, the electrolyte becomes thick and sluggish, making it harder for lithium ions to move. Worse, if lithium ions cannot enter the negative electrode fast enough during charging, they may form metal deposits on its surface — a process called plating that can cause short circuits and even fires.

Why Sodium Is Different

As its name suggests, a sodium-ion battery replaces lithium with sodium — an abundant and cheap element found in ordinary salt. Sodium ions are actually larger than lithium ions, which previously limited their energy storage. But in cold weather, that size difference becomes an advantage.

"Sodium ions form weaker bonds with the electrolyte than lithium does," explains Liu Chenguang, a battery researcher at Xi'an Jiaotong-Liverpool University. "This allows them to detach and move much more easily, even when the cold makes the electrolyte thick." In other words, sodium suffers less from the winter sluggishness that cripples lithium.

CATL claims that at –30 degrees Celsius, Naxtra can deliver nearly three times the discharge power of comparable lithium iron phosphate (LFP) batteries. It can charge to 90 percent at –40 degrees and maintain "stable power delivery" at –50 degrees in laboratory tests.

Independent experts caution that these figures are best-case results from controlled conditions. "Real-world performance depends on driving style, heater use and many other factors," says one analyst. Early sodium-ion cars sold in China in 2023 had a range of just 170 kilometres and sold poorly. CATL has spent nearly $1.4 billion and 300 researchers on improving the technology since then.

The Bigger Picture

Sodium-ion batteries will not replace lithium-ion entirely. They have lower energy density, meaning a car needs a heavier, larger battery pack for the same range. But they do not require lithium, cobalt or nickel — metals whose prices are volatile and whose mining raises environmental concerns. Salt is everywhere and cheap.

For China, which has almost no domestic lithium reserves but vast salt flats rich in sodium, the technology offers a strategic advantage. And for cold-climate drivers anywhere, a battery that works without preheating may finally remove one of the last major obstacles to mass EV adoption.

Questions 1–5

Choose the correct letter, A, B, C or D.

1. What is the main advantage of CATL's Naxtra battery?

   • A. It has a longer range than lithium-ion.
   • B. It works reliably at extremely low temperatures.
   • C. It is cheaper to produce than LFP batteries.
   • D. It uses no rare earth metals at all.

2. In cold weather, a typical lithium-ion EV may lose what percentage of its range?

   • A. 10–20 percent
   • B. 20–30 percent
   • C. 30–40 percent
   • D. 50–60 percent

3. What is "plating"?

   • A. The process of charging a battery in warm weather
   • B. Lithium metal forming on an electrode surface during cold charging
   • C. A new type of battery coating
   • D. The recovery of energy from braking

4. Why are sodium ions less affected by cold than lithium ions?

   • A. They are smaller and move faster.
   • B. They form weaker bonds with the electrolyte.
   • C. They do not need an electrolyte.
   • D. They are found in table salt.

5. What is a disadvantage of sodium-ion batteries?

   • A. They are more expensive than lithium.
   • B. They have lower energy density.
   • C. They cannot be recharged.
   • D. They require cobalt.

Questions 6–10

Do the following statements agree with the information?

Write:

• TRUE
• FALSE
• NOT GIVEN

6. Sodium-ion cars will be sold in the US in mid-2026.
7. CATL is the world's largest EV battery maker.
8. At –40 degrees, Naxtra can charge to 90 percent.
9. Early sodium-ion cars from 2023 had a range of over 500 km.
10. China has large domestic lithium reserves.

Questions 11–13

Complete the summary below. Choose ONE WORD ONLY from the passage.

Both lithium-ion and sodium-ion batteries store energy by moving ions between 11 through a liquid electrolyte. In cold weather, the electrolyte thickens and ions move more slowly. Lithium ions may also form 12 on the electrode surface, causing damage. Sodium ions, although larger, bond more 13 with the electrolyte and therefore remain mobile in the cold.

Answers

1. B — "perform stably at –50 degrees Celsius."
2. C — "lose 30 to 40 percent of its range."
3. B — "form metal deposits on its surface."
4. B — "weaker bonds with the electrolyte."
5. B — "lower energy density."
6. FALSE — The cars are scheduled for China, not the US.
7. TRUE — "the world's largest producer of EV batteries."
8. TRUE — "charge to 90 percent full when the temperature drops to –40 degrees."
9. FALSE — The range was 170 kilometres.
10. FALSE — China has "almost no domestic lithium reserves."
11. electrodes
12. deposits / plating
13. weakly

Key Vocabulary