Breakthrough in the sixth attempt
The electrode slurry is essential for the power density and energy density of a battery. Find out how we have revolutionized electrode slurry production for our customer Lishen in China.
August 2019
It's 2014: Jesse Wang wipes a bead of sweat from his face and readjusts his breathing mask. He knows that now is not the time to make mistakes. He joined Bühler three years ago, in July. He didn't know much about batteries when he started, and he never thought that he would become an expert working tirelessly to develop a new electrode slurry. A process that would be so unique that his customer, Yi Liu, would later say: "This solution from Bühler will completely change the battery industry. It is a historic moment, a revolution."
Customer partnership
Customer partnership
The electrode slurry is essential for the power density and energy density of a battery, that is to say, for the output and energy per battery volume. Traditionally, slurries are produced in batches in large vessels. These conventional plants are huge and expensive. The process is also very inflexible: if a batch does not meet the requirements, it is either disposed of or used for inferior products.
While the production of large batches takes several hours, the production in the new process developed by Bühler takes only a few minutes. Using a rotating twin-shaft mixer, the necessary process steps – such as mixing, homogenizing, dispersing, and degassing – are combined in a single, continuously running unit.
Just after starting in this position, Wang received the order to expand the battery laboratory at the Bühler site in Wuxi. The talks with the first customer were so promising that Bühler quickly decided to make this preliminary investment.Wang was responsible for the battery industry in China, supported by his colleagues at the Swiss headquarters who had originally developed the idea for the new process.
But now he is alone in the battery lab, already working on the sixth trial to make the electrode slurry. So far, the tests have not produced the sought-after results. Would he meet the high requirements his customer Lishen was looking for this time?
Batteries keep our world turning. They are the small energy stores that drive our lives and make them easier. More and more cars are being entirely powered by batteries – particularly in China. In 2017, around 800'000 electric cars were sold in the country; that's nearly half the total global production. E-mobility is heavily supported and subsidized by the Chinese government. It is an effective measure against air pollution and crucial to China's strategy of becoming a high-tech country. Financial support is expected to run out by the end of 2020 though. By that point at the latest, car batteries will have to be powerful enough to be able to survive in the free market. Reason enough for battery manufacturers such as Lishen to invest significantly in research and development of new processes to produce batteries.
Founded in 1997, Lishen today employs over 9000 people. Its list of customers reads like a "who's who" of the electronics and entertainment industry: Apple, Samsung, Dell, HP, Huawei, and Lenovo are just some of the illustrious names. The Chinese battery manufacturer has production plants in Beijing, Qingdao, Suzhou, Wuhan, Shenzhen, and Mianyang and is one of the top-five battery producers in China. Lishen is planning to increase yearly output from around 10 GWh currently to 40 GWh by 2021 – which is equivalent to an output of around 800'000 car batteries.
This solution from Bühler will completely change the battery industry. It is a historic moment, a revolution.
YI LIU,
Lishen Engineer, China
Wang applies the electrode slurry carefully onto a carrier film. It is black and slightly viscous in consistency. He is using a film applicator to apply the layer as thinly as possible on the film – this should be no thicker than 100 micrometers. Afterward, the dried electrode goes to Lishen and to his main contact, Liu, the engineer who is responsible on the customer side.
The cooperation with Lishen is extremely close. The two companies work well together: as the client, Lishen brings its expertise and knowledge of batteries to the table. In return, Bühler brings knowledge of processes and years of experience in continuous mixing: a unique mixing process never used in the battery industry before until now.
Thanks to this continuous mixing process, the manufacturer is able to intervene at any given moment should the results not meet the requirements. Ultimately, what counts is that the improved mixing process significantly increases battery performance. It also reduces the investment costs, and the energy costs are much lower using this new process in comparison to using conventional production methods. Lastly, the space requirements of the new process are considerably lower, and fewer rejects are produced. Something that has also impressed Lishen. Abandoning the classic batch processing of electrode slurry in favor of a new continuous process benefits the customer. But will Bühler be successful in developing the industrial-scale process soon enough for Lishen's new plant?
Each trial takes several months. First, the Bühler engineers develop and validate the optimum slurry composition based on Lishen specifications. Once the Bühler team is satisfied with the test results, they produce 50 liters using the new formula, which is then sent to Lishen. Liu, currently a leading engineer from the process department at Lishen, then takes over. The Lishen team uses the new electrode slurry to create battery prototypes and conducts extensive tests. Because this is no ordinary electrode slurry. Bühler has revolutionized the battery-making process.
Wang is in the analysis laboratory. In addition to the many other parameters, for this sixth test he has further adjusted the concentration of the bonding agent. The test results are in. He checks the viscosity and the distribution of particles in the electrode slurry as well as the electrical conductivity of the electrode; together these determine the power density and energy density of the battery. The viscosity of the slurry was particularly problematic in the last series of tests. New raw materials and new parameter settings led to the slurry being too thick, so that it could not be optimally used. "Thick and viscous like toothpaste," Wang recollects.
The latest values convince the engineer. The test results meet Liu's requirements. But it will be several months before Lishen confirms the results. It's a long wait before Wang knows whether the client will want to perform more trials. But time is of the essence, because Lishen's competitors are also working on innovations, and the Bühler process is the first in a series of steps in the complicated process of developing batteries.
Should the Bühler engineers miss their goal, it endangers the whole manufacturing process and the new plants Lishen is planning in Suzhou.The production of batteries takes place in several phases. It begins with preparing the various raw materials that the battery manufacturers usually buy from chemical companies. These are then processed into anode and cathode slurries in a mixing process.
This is where Bühler's innovative continuous mixing process comes in; however, Bühler solutions are also used in the upstream process to ensure correct dosing of raw materials. After the mixing process, the slurries are applied to films. These are then cut to size and rolled up into battery cells. In the next step, the manufacturers charge and discharge the cells to ensure the best possible battery performance. Finally, the cells are packaged in battery packs, which are then used in cars. A single electric car battery consists of several hundred to several thousand battery cells.
This order has allowed us to send a clear signal to the industry: the new mixing process is ready for industrial use.
JESSE WANG,
Bühler engineer
Months later, Wang’s mobiles phones rings. He takes the call. Liu is on the other end of the line. The Lishen project manager, who is usually rather restrained, is delighted: the results of the sixth trial are impressive. The viscosity problem has been solved, and the power density and energy density of the batteries have significantly increased during the test series.
Wang can hardly believe it. He only trusts the results after conducting the tests again. But in fact, Wang and his team have done it. The electrode slurry was indeed of the required quality. Things now start picking up pace, and Lishen signs a contract for the delivery of a pilot plant to their factory in Tianjin. It is August 2014, three years after Wang started working for Bühler. The successful trials that eventually led to ordering the first pilot plant were the beginning of a mutual success story for Lishen and Bühler. Both partners agreed the delivery of 10 production lines on an industrial scale. Four will be opened in the new Suzhou factory, two in Tianjin, where the pilot plant is located, and four more at the Qingdao location. Altogether, the lines have a yearly output of up to 10 GW/h. Enough to produce more than 200,000 car batteries per year.
“This order allowed us to send a clear signal to the industry: the new mixing process is ready for industrial use; the benefits can be seen directly in an industrial context.
So it did not take long for additional orders to roll in. Another customer has already ordered four production lines, and we are in talks with further customers,” Wang explains.
This is where Bühler's innovative continuous mixing process comes in; however, Bühler solutions are also used in the upstream process to ensure correct dosing of raw materials. After the mixing process, the slurries are applied to films. These are then cut to size and rolled up into battery cells. In the next step, the manufacturers charge and discharge the cells to ensure the best possible battery performance. Finally, the cells are packaged in battery packs, which are then used in cars. A single electric car battery consists of several hundred to several thousand battery cells.
Wang ties his tie. It is July 20th, 2017. Today is a historic moment, the grand opening of the Lishen plant in Suzhou in front of hundreds of spectators. He has already visited the plant and knows just how impressive it is: stretching over 600 by 50 meters, the plant contains all the processing steps for car batteries, from the raw materials and the electrode slurry right up to the finished electric car battery. Everyone from the battery industry will get together tonight. Representatives of the local and regional government will show up. A great success after six years of work in the lab.
It has grown dark in Suzhou. The audience listens with bated breath to the statements made by Qin Xingcai, the President of Lishen. The company plans to be at the forefront of the Chinese battery market with the new plant. "This new factory of ours is producing a new generation of batteries. This 30% increase in energy density means we have achieved a quantum leap," Liu and Wang nod to each other with appreciation. Lishen Suzhou honors Bühler with the Best Equipment Supplier award. "Six years of joint research and development have paid off.
Six years of strong cooperation between Lishen and Bühler colleagues in China and Switzerland. This award and 10 production lines at Lishen are visible proof of this," Wang says with pride. And Liu adds: "Bühler kept the promise they made. Bühler is our long-term partner; we tackle new projects together." Since then, Liu has been appointed Manager of the Engineering Department at Lishen. Not least because of the successful project with Bühler, and a milestone for the battery industry.
