# Battery Charging Speed and Energy Density

Topic radar · 5,218 documents · 2021-01-01–2026-11-09 · updated 2026-11-08

Canonical: https://slate.greyb.com/radar/battery-charging-speed-and-energy-density/innovations

## In one minute

### The same two moves recur in every chemistry
The first move is to host more ion per gram of material. Silicon takes roughly ten times the lithium per gram that graphite does, and swells by up to 300% in the process, which cracks particles and rebuilds the surface film each cycle [1]. Sulfur converts through dissolved polysulfide intermediates, so its capacity depends on keeping those intermediates inside a conductive scaffold [2]. Iodine pushed into higher valences carries several electrons per atom instead of one [3]. In sodium cells the energy sits in closed pores of hard carbon that fill at a low plateau, which is also where sodium plates when charging is pushed [4].

The second move shortens the path or repairs the interface. Laser-ablated channels through a calendered electrode postpone plating above 4C [5]. Removing under 0.4% of the electrode as sparse conical pores raises the achievable rate without cutting usable energy [6], and three-dimensional porous structures reach 62.3% state of charge at 10C [7]. Those designs work on graphite, on lithium iron phosphate, and on chemistry already in production.

1. [10.54097/pqchwg18](https://doi.org/10.54097/pqchwg18)
2. [10.1021/acs.jpclett.6c00675](https://doi.org/10.1021/acs.jpclett.6c00675)
3. [10.1021/jacs.6c00787](https://doi.org/10.1021/jacs.6c00787)
4. [10.1039/d5nh00471c](https://doi.org/10.1039/d5nh00471c)
5. [10.1149/ma2022-012342mtgabs](https://doi.org/10.1149/ma2022-012342mtgabs)
6. [10.1021/acsenergylett.4c01727.s002](https://doi.org/10.1021/acsenergylett.4c01727.s002)
7. [10.1021/acsenergylett.5c01406](https://doi.org/10.1021/acsenergylett.5c01406)

### The charge time buyers compare comes from iron phosphate packs
CATL quotes its third-generation Shenxing iron-phosphate pack at 10% to near full in under seven minutes, holding over 90% of capacity after 1,000 fast cycles. BYD's second-generation Blade quotes 20% to 97% with a plan for 20,000 fast-charging stations by year end. Sunwoda put a 15C iron-phosphate pack on its roadmap, a number its own trade coverage flagged for caution.


### The areas with a line to fill are filed by companies
Lithium-ion carries roughly twice as many company documents as university and institute ones combined, and lead-acid with hybrid pack integration runs at a similar ratio. The names doing the filing are not only the headline cell makers. CATL leads overall, but Zhuhai Cosmx, Jiangsu Zhengli, Svolt, CALB, Liwei and Envision all sit near the top, alongside BASF-type materials suppliers and a Chinese Academy of Sciences layer.


### Charge rate is now bought from geometry and interface
The pattern holds outside lithium-ion. In sodium cells a pore-size-controlled hard carbon paired with a layered oxide reached 2.2 Ah and about 90% of capacity in ten minutes, holding roughly 90% after 1,500 cycles at 6C. In solid-state, sulfides already conduct about as well as the liquid they replace, so the work moved to making a dense film: sputtered 1 to 10 µm layers that are pore-free as deposited. A garnet interface engineered with a thin gold layer charges at up to 2.5 mA/cm² at 0.7 MPa of stack pressure, and a bromide electrolyte reached 1.4 mS/cm and cycled 6,000 times at 10C.


### What a buyer can purchase, and the claim standing beside it
Set what has reached a product beside what the same period's papers and patents claim, and the gap is consistent across the whole radar.


### Sodium-ion is the anomaly: a product in the showroom and a thin company file
Sodium has a passenger car in production and a 60 GWh storage agreement signed, yet university and institute documents still outnumber company ones. Its parameter filings are recent and specify porosity, particle size, coating weight and capacity ratios to manufacturing tolerance. The filers are mostly manufacturers entering from elsewhere, including lead-acid and solar firms rather than battery specialists.


### The measurements do not yet separate the areas
What limits these designs now is making them repeatably, and what hides the cost of that is how they are reported. A 2026 review of solid-state scale-up finds coin cells passing 2,000 cycles at 2C while pouch cells above 50 Ah fall below 500. Most rate results also come from electrodes thinner than a practical cell needs, at 0.5 to 1.5 mg per square centimetre against the 3 to 6 a production electrode carries, which flatters them.


### Energy density is what got signed, and the seller now publishes a cycle life
Group14's five offtakes carry minimum commitments above US$300 million. Nexeon supplies Panasonic's Kansas plant. Sila supplies Mercedes-Benz, with the G-Class as the named vehicle.


## Overview


Six areas, and one shift runs under all of them. Charging speed and energy density have come apart. Charge rate is now delivered at the coating line and in the charging protocol, on chemistries already in production. Energy density is still a materials problem, and it has been sold forward on contracts that fix volume and leave price, loading and cycle life open. Once those two separate, the asset that decides who wins stops being the material and becomes the qualification record and the warranty standing behind it.


## What's new


BYD's nine-minute Atto 8, first shown at the Paris Motor Show in October, was restated this week with European deliveries set for the first quarter of 2027.


## Market

### The volume buyer that arrived is a storage developer
Storage additions are headed for a record in 2026 and 2027. That buyer purchases cost per kilowatt-hour and cycle count. It is where the largest commitments now sit: CATL's 60 GWh sodium agreement runs three years and is a storage deal, and the US executive order that followed effectively bars Chinese cells from grid-scale projects, which sorts suppliers by origin before it sorts them by performance.


### The rules now move landed cost further than the materials do
China exempts sodium-ion and solid-state cells from excise tax through the end of 2028, conditional on a test report under national standards, while lithium-ion pays 2% from September 2026 rising to 4% a year later. At a 4% rate that is a few tens of dollars per kilowatt-hour on a high-cost cell, which is comparable to the margin on a mature one.


### The number the market has not produced is a price
No silicon, sodium, all-solid or zinc-iodine product here carries a price per kilowatt-hour from a signed deal. The one transacted comparison is a September 2026 mixed-chemistry storage tender that averaged ¥1.0322/Wh for sodium against ¥0.5318 for lithium iron phosphate. One tender bundles integration, warranty and financing, so it overstates a cell-level penalty, and it still marks the distance between a parity claim and what a buyer was asked to pay in the same year.


## Strategy

### Solid-state files hardest without a product to sell
Solid-state has grown faster than any other area: from around twenty documents in 2021 to ninety-two through October 2026. Its 121 company documents are the third largest of the six areas, and no all-solid product has shipped to justify them. The company list has breadth rather than depth. Cell makers such as CATL, LG Energy Solution, Samsung SDI, SK On, BYD and Envision sit beside Toyota, Nissan and Honda, a layer of small specialists, and separator incumbents such as Celgard. Envision appears under two entity names, which is a company organising a programme.


### Rate records and manufacturing claims come from different organisations
Universities and national laboratories hold the rate results. A 3D-printed cathode with a pore and loading gradient reached 15.7 mAh cm⁻² at 5C in a single-layer pouch; a garnet interface engineered with 300 nm of sputtered gold charged at 2.5 mA cm⁻² at 0.7 MPa. Both are academic groups publishing a mechanism on a small cell.


### Filing is Chinese in every area, and the second office names the second industry
China leads all six. Within lithium-ion, Chinese documents (1,711) run several times the US (211), Korean (156) and Japanese (95) totals combined. Sodium is the outlier in shape: China 302, then the US at 20 and India at 18, an unusual second place for a battery chemistry.


### Automakers have started filing on the parts that set the charge number
A move that was not visible a few years ago: vehicle makers are claiming electrolyte and electrode architecture directly. Geely claims an electrolyte conductivity band, Dongfeng a coated current collector, and Guangzhou Automobile a particle-level porosity gradient.


### Two areas have stopped growing while the rest advanced
Sodium held between 95 and 101 documents a year since 2024, and lithium-sulfur has stayed between thirteen and thirty a year across the whole window, with one paper in the latest month. Against solid-state's climb from twenty to ninety-two, that is a plateau in both.


### What would mark a change in direction
Three signals would move this reading. Company filings in solid-state turning to rate and thickness rather than dryness and composition, which would show the interface problem becoming a manufacturing one. A company filing base appearing in aqueous zinc or lithium-sulfur, where at present a university can hold the most advanced position and also be the party building the plant. And a second filing office establishing itself in sodium, which would show a supply chain outside China forming around the chemistry rather than a market for Chinese cells.


## Areas

- Lithium-Ion · 3,000 documents
- Sodium-Ion · 420 documents
- Solid-State · 313 documents
- Lithium-Sulfur · 125 documents
- Lead-Acid & Flexible/Semi-Solid · 693 documents
- Aqueous Zinc & Supercapacitors · 643 documents