New research believes that lithium batteries can achieve higher energy density without just focusing on 3.7v 18650 lithium battery

According to foreign media reports, although lithium-ion batteries still have room for improvement, most people in the industry believe that 3.7v 18650 lithium battery will become the next-generation battery of choice. Now, Tesla's battery research partners have announced a method to achieve higher energy density in lithium-ion batteries, allowing everyone to no longer focus on 3.7v 18650 lithium battery.

A team at Canada's Dalhousie University, led by Professor Jeff Dahn, in collaboration with colleagues at Tesla's Canadian R&D Center and the University of Waterloo, Canada, demonstrated the use of a dual-salt electrolyte (fluoroethylene carbonate). Ester (FEC): An anode-free lithium metal battery made of 1M lithium difluoroborate (LiDFOB) and 0.2M lithium tetrafluoroborate (LiBF4) in ethylene carbonate (DEC) solution. The researchers say their findings could shift research focus from 3.7v 18650 lithium battery (SSBs) to rechargeable, high-energy-density batteries.

Replacing traditional graphite anodes with lithium metal is one of the most popular methods to increase the energy density of lithium-ion batteries, which can increase the energy density of the battery by 40% to 50%. However, only when the lithium metal anode is ultra-thick can the energy density be significantly increased. However, in practice, very thick anodes cannot be used at all, so the researchers stated that the thickness of the lithium metal anode needs to be limited to 50 microns. Limiting excess lithium is a huge challenge, because the surface of metallic lithium is easy to form dendrites, which will increase the reactivity of the anode and electrolyte, isolate metallic lithium, and lead to low battery cycle efficiency. This cycle inefficiency is particularly evident in anodeless batteries, which are built directly with bare copper anodes and lithium is deposited directly on the cathode during the first charge cycle. Since there is no excess lithium in the battery, battery size is minimized and energy density is maximized, but performance can be very poor because there is no stored lithium to continuously replenish the battery during cycles.

In order to improve the cycle stability of liquid electrolytes, many different methods have been adopted, such as high salt concentration electrolytes, ether solvents, fluorinated compounds, electrolyte additives, anode surface coatings and external pressure. In addition, there is another method to use solid electrolytes, but solid electrolytes have not succeeded in completely eliminating the lithium dendrite problem, and it is not clear whether this technology is compatible with existing lithium-ion battery production equipment, and currently in lithium-ion batteries Investments in production equipment have reached billions of dollars. However, if safe, long-life lithium metal batteries can be produced using liquid electrolytes, then existing production equipment can quickly commercialize high-energy-density batteries.

In this study, researchers used electrolytes made of LiDFOB and LiBF4 to achieve the longest cycle life of existing anode-free batteries. After 90 cycles, 80% of the capacity can still be maintained. Because the lithium metal anode consists of tightly packed lithium with a diameter of 50 microns, no dendrites will grow even after 50 cycles. Furthermore, compared with single-salt electrolyte complexes, dual-salt electrolyte complexes perform better at different voltages and are less dependent on external pressure to achieve good cycle performance.

In a new battery, lithium ions are extracted from the battery cathode and deposited onto the current collector in the form of metallic lithium (Cu) during the initial charge. During the discharge process, lithium ions are stripped from the current collector and directly enter the cathode.

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