Chapter 55 Engineering Challenges

One week later.

At three in the afternoon, the atmosphere in the laboratory was as oppressive as the sky before a storm.

Everyone gathered around the test bench, staring at the glaring curve on the screen.

"Cycle 201, capacity retention has dropped below 80%." Li Xiao's voice was cautious, as if afraid of disturbing something. "According to commercial standards, 200 cycles... is a failure."

No one spoke.

Zhang Zhe stared at the screen, his brow furrowed into a knot. The separator modification plan he was responsible for had already gone through three rounds of optimization, yet the best batch of samples only lasted until cycle 203.

Chen Xueming stood by the side, his fingers unconsciously tapping on the tabletop, producing a dull thudding sound.

He had been with the team for exactly ten days. During these ten days, he had practically lived in the laboratory, designing round after round of electrolyte formulas, adjusting lithium salt concentrations, solvent ratios, and additive types—testing every parameter he could think of.

The best result: 208 cycles.

It was still four-fifths short of the commercial standard of 1,000 cycles.

"Has all the data been compiled?" Lin Mo's voice came from behind.

Li Xiao nodded. "It's all here. The electrolyte group's best is 208 cycles, the separator group's is 203, but when combined, it actually decreased to only 195."

Lin Mo walked to the screen and carefully examined the decay curve.

For the first 50 cycles, the capacity retention was almost a straight line, so stable it was heartening. After 50 cycles, it began a slow decline. After 150 cycles, the decline accelerated. Around 200 cycles, it took a precipitous plunge.

A typical outbreak of the "Shuttle Effect."

"polysulfides accumulate to a critical point around cycle 200," Chen Xueming spoke, his voice somewhat hoarse. "The better the early suppression, the more violent the later outbreak. It's like a dam; the longer it holds back the water, the more complete the collapse."

Zhang Zhe nodded. "Same on my end. Separator modification can block some polysulfides, but not all. Around 200 cycles, the corrosion of the negative electrode noticeably accelerates."

Lin Mo was silent for a few seconds, then asked, "Is the direction wrong?"

This question made everyone's heart tighten.

A wrong direction meant that these ten days of effort—perhaps even longer—might have to be scrapped and restarted from scratch.

Chen Xueming clenched his fists.

"No." He looked up. "The direction isn't wrong; our thinking is just too narrow."

He walked to the whiteboard, picked up a marker, and took a deep breath.

"I've been trying to suppress polysulfides by optimizing the electrolyte. Teacher Zhang wanted to block them by modifying the separator. We were fighting separate battles, and the result is that the electrolyte and the separator are hindering each other; neither can achieve its best effect."

He drew two circles on the whiteboard, one labeled "Electrolyte" and the other "Separator," connected by a line.

"What we need is synergy, not just superposition."

Zhang Zhe's eyes lit up. "You mean... make the electrolyte and the separator work together?"

"Exactly." Chen Xueming drew a heavy stroke over the connecting line. "It's not about each pursuing its own optimum, but pursuing the best performance when working together. The electrolyte can sacrifice a bit of early performance to be more compatible with the separator; the separator can also relax its blocking capability slightly to leave room for the electrolyte."

Li Xiao raised her hand. "But how do we know if they work well together? There are too many permutations and combinations, aren't there?"

"Theoretical screening," Chen Xueming said. "I've accumulated some data over the years regarding the compatibility of different additives and separator materials. If we can combine that with Teacher Zhang's separator database and then use Teacher Li's program for matching—"

He turned to Lin Mo. "Teacher Lin, we need a system simulation."

Lin Mo looked at him, the corners of his mouth curling up slightly.

"How long will it take?"

"Three days," Chen Xueming said. "Give me three days, and I'll organize the candidate formulas and matching schemes."

Lin Mo nodded. "Then let's do it."

He scanned the room, his voice steady and powerful.

"The commercial standard is 1,000 cycles, so we'll aim for 1,000. 208 cycles is the starting point, not the end. Everyone—from now on, fully cooperate with Dr. Chen's plan."

Zhang Zhe nodded. "Understood."

Li Xiao also nodded. "Got it!"

Chen Xueming was stunned for a moment and looked at Lin Mo. "Teacher Lin, aren't you going to ask how confident I am?"

Lin Mo smiled. "You just said you needed three days, not that you needed a guarantee. That shows you truly want to make it work, rather than just relying on luck."

He patted Chen Xueming on the shoulder.

"Go do it. I believe in you."

For the next three days, the laboratory entered a wartime footing.

Chen Xueming hardly ever left his workstation. He pulled up all the experimental data he had accumulated over the years, organizing it page by page and marking it line by line. Some records dated back to his time in the United States, the paper already yellowing, but he remembered every detail—that failed attempt, that accidental discovery, that hypothesis rejected by his advisor.

Zhang Zhe wasn't idle either. He opened up his entire separator database, providing Chen Xueming with every detail regarding material parameters, preparation processes, and test results.

Li Xiao was even more energized. She used a web crawler to fetch the latest international literature while writing matching algorithms to help Chen Xueming screen possible combinations from the massive amount of data.

"Dr. Chen, look at this!" She ran over from time to time, pointing at a paper on the screen. "A Japanese team published one last year using an additive somewhat similar to what you're thinking of!"

Chen Xueming leaned in to look, his eyes growing brighter. "Yes! That's exactly the right thinking! What concentration did they use?"

"0.5M!"

"Help me check the separator material they used!"

"On it!"

Zhao Gang was not to be outdone. Although he didn't understand the data, he had his own way of supporting them—every night at ten o'clock, he would punctually appear at the laboratory door with night snacks in hand.

"Take a break, everyone, and eat something." He placed the bag on the table. "Lamb skewers, freshly grilled, eat them while they're hot."

Li Xiao was the first to rush over. "Uncle Zhao, you're the best!"

Chen Xueming paused for a moment and then walked over. He picked up a lamb skewer and took a bite; it was steaming hot, the fragrance of cumin and chili exploding in his mouth.

"It's delicious," he said.

Zhao Gang gave a rare smile. "Of course. These are the best lamb skewers on this street. I ran two kilometers to buy them."

Chen Xueming looked at him, wanting to say something but not knowing what. Finally, he just nodded. "Thank you, Captain Zhao."

Zhao Gang waved his hand. "Less talk. Finish eating and get back to work."

The following night, Chen Xueming finally compiled the first version of the candidate formula list.

Five full pages, densely listing over thirty additive combinations, each marked with potential advantages, latent issues, and the types of separators they needed to be matched with.

He handed the list to Zhang Zhe. "Teacher Zhang, take a look at these. Which separator schemes can match them?"

Zhang Zhe took it and flipped through the pages. After finishing the first page, he looked up. "For this combination, my PVDF-HFP modified membrane is worth a try."

Chen Xueming's eyes lit up. "Really?"

"Yes." Zhang Zhe flipped to the second page. "For this one, a PI-based one must be used. I have some spares on hand."

He flipped faster and faster, making more and more notes. Half an hour later, out of the thirty-plus combinations, he had screened twelve feasible matching schemes.

"That's it," Zhang Zhe said. "We'll start preparing samples tomorrow. We should have the first batch of test data within three days."

Chen Xueming looked at the densely annotated list, his eyes feeling a bit warm.

"Teacher Zhang," he said, "thank you."

Zhang Zhe said indifferently, "No need for thanks. It's all just part of the work."

Just then, Li Xiao suddenly cried out, "Dr. Chen! Come look at this!"

Chen Xueming walked over, and Li Xiao pointed at the screen. "I just fetched a preprint. A team from MIT is using an additive almost identical to what you were thinking of! But they got stuck on the separator matching, and their cycle life is only 400!"

Chen Xueming stared at the screen, his heart racing.

The team from MIT followed the same thinking as him, but they only reached 400 cycles.

Why?

He looked closer, his eyes brightening more and more as he read.

"The separator they used is a commercial Celgard, not a modified one." He turned to Zhang Zhe. "Teacher Zhang, if we swap it for your PVDF-HFP membrane, can we achieve a breakthrough?"

Zhang Zhe pondered for a few seconds. "Theoretically, yes. My membrane's blocking rate for polysulfides is 30% higher than Celgard's, but it slightly reduces ionic conductivity. If we can balance it well—"

"I'll adjust the formula," Chen Xueming interrupted him. "I can fine-tune the additive concentration to compensate for the loss in ionic conductivity."

The two looked at each other and said simultaneously:

"Give it a try?"

"Give it a try."

At eleven o'clock on the third night, the preparation of the first batch of twelve sample groups was finally complete.

Chen Xueming stood before the workstation, looking at the encapsulated pouch cells, his heart filled with mixed emotions. These small batteries carried everyone's hopes—his, Zhang Zhe's, Li Xiao's, Lin Mo's, and even those lamb skewers from Zhao Gang.

"Shall we start the test?" Li Xiao asked.

Chen Xueming glanced at the clock on the wall. "If we test now, we'll have the first batch of data by tomorrow morning. Test them!"

Li Xiao nodded and began setting up the test program.

Chen Xueming watched from the side and suddenly remembered something. "Right, the data recording should be split into two groups—save the single-component data and the coupled data separately. That way, it'll be easier to perform a comparative analysis later."

"Understood!"

Zhang Zhe walked over and stood next to Chen Xueming, also looking at the batteries.

After a few seconds of silence, he suddenly asked, "Dr. Chen, are you confident?"

Chen Xueming turned to look at him, thought for a moment, and said, "Yes."

"Why?"

"Because this time, I'm not thinking alone," Chen Xueming said. "Your separator, Li Xiao's data, Teacher Lin's support—all of these added together are much stronger than when I was working in isolation before."

Zhang Zhe was silent for a few seconds, then nodded.

"Me too."

Just then, the door was pushed open.

Lin Mo walked in and was surprised to see everyone still there. "You haven't left yet?"

Li Xiao didn't even turn her head. "We're testing! The first batch of data will be out tomorrow morning!"

Lin Mo walked to the test bench, looked at the batteries undergoing charge-discharge cycles, was silent for a few seconds, and then said:

"Regardless of the result, you've all done your best."

Chen Xueming shook his head. "It's not enough. Only reaching 1,000 cycles counts as doing our best."

Lin Mo looked at him and smiled.

"Fine. Then let's get to 1,000."

At seven o'clock the next morning, Chen Xueming was the first to rush into the laboratory.

He went straight to the test bench and stared at the data on the screen.

Group One: 127 cycles.

Group Two: 156 cycles.

Group Three: 189 cycles.

Group Four: ...

He looked down the list, his heart beating faster and faster.

Group Eleven: 612 cycles.

Chen Xueming was stunned.

612 cycles.

It was three times the previous 208 cycles.

It was still 388 cycles short of 1,000.

But—the direction was right!

Just then, Zhang Zhe also rushed in. "How much?"

Chen Xueming pointed at the screen, his voice trembling slightly. "Teacher Zhang, look."

Zhang Zhe leaned in and stared at the number, not speaking for a long time.

Then he looked up at Chen Xueming, his eyes lit up.

"Another round," he said. "Optimize the parameters and prepare a second batch."

Chen Xueming nodded vigorously. "Another round."

Li Xiao and Lin Mo also arrived. Several people gathered around the screen, looking at the curve that far exceeded market standards, their faces filled with irrepressible excitement.

"Dr. Chen," Lin Mo said, "does this formula have a name?"

Chen Xueming paused for a moment and thought about it. "Let's call it... E-Li-1. Electrolyte Number One."

Lin Mo nodded. "E-Li-1, write that down. There will be E-Li-2 and E-Li-3 in the future, until we reach 1,000 cycles."

Chen Xueming looked at him, his eyes feeling a bit warm.

"Teacher Lin," he said, "thank you."

Lin Mo patted him on the shoulder.

"No need for thanks. You came up with it yourself."

Chen Xueming shook his head. "It wasn't just me; it's what we came up with together."

He looked at Zhang Zhe, at Li Xiao, and at Zhao Gang, who had arrived at the door at some unknown point.

"All of us together."

Sunlight streamed in through the window, falling on the batteries being tested, on the number 612 on the screen, and on the slight smiles on everyone's faces.

The bottleneck has finally begun to loosen.