Periodic Reporting for period 1 - AM4BAT (Gen. 4b Solid State Li-ion battery by additive manufacturing)
Reporting period: 2022-07-01 to 2023-12-31
The concept of anode-free as the core concept of AM4BAT project, has been attracted increasing attention within the battery community recently. In this concept, a current collector (CC) devoid of an anode material is integrated with other essential battery cell components during manufacturing. The anode is expected to form on the CC during the initial charging phase of the cell. During discharge, it is expected that the Li deposited on he CC will return to the cathode, leaving the CC to its pre-charge state. In terms of energy, there hasn't been significant progress in specific energy compared to LMB, primarily because of the inherently low density of Li metal (0.534 g/cm3). However, in terms of volumetric energy density, anode-free LIBs could theoretically achieve more than 1000 Wh/L, a noteworthy number when compared to both graphite batteries (250-500 Wh/L) and LMBs (~750 Wh/L).
While the anode-free idea is fascinating, it does come with certain limitations. First and foremost, the CC must exhibit a high degree of lithiophilicity to ensure a uniform deposition of Li during charge process. In another term, this means that the CC, acting as the substrate for Li deposition, should have a minimal nucleation overpotential. Unfortunately, this criterion is not met by the commonly employed copper (Cu) CC in traditional LIBs. The second significant challenge is related to the reversibility, or, in technical jargon, the quality of stripping/plating, which at a full cell level, translates to the battery’s coulombic efficiency (CE). A model developed at Smalley-Curl Institute reveals that to retain 80% of the initial capacity after 1000 cycles a CE of 99.987% is required in an anode-free configuration.
Due to the absence of excess Li in an anode-free configuration, not only the anode but also other battery components, including the cathode, must operate efficiently to preserve all available Li in the cell. Currently. Cathode materials typically demonstrate first discharge efficiencies of approximately 85-88% for NMC, 94-96% for LCO, and slightly higher than LCO for LFP, ranging from 95-97%. Another critical component crucial for the success of anode-free batteries is the role of electrolyte. Despite recent strides in optimizing cycling parameters and enhancing liquid electrolytes, inadequate efficiencies and dendrite growth during lithium plating contribute to poor cycle life, typically less than 100 cycles, along with safety concerns.
While the anode-free idea is fascinating, it does come with certain limitations. First and foremost, the CC must exhibit a high degree of lithiophilicity to ensure a uniform deposition of Li during charge process. In another term, this means that the CC, acting as the substrate for Li deposition, should have a minimal nucleation overpotential. Unfortunately, this criterion is not met by the commonly employed copper (Cu) CC in traditional LIBs. The second significant challenge is related to the reversibility, or, in technical jargon, the quality of stripping/plating, which at a full cell level, translates to the battery’s coulombic efficiency (CE). A model developed at Smalley-Curl Institute reveals that to retain 80% of the initial capacity after 1000 cycles a CE of 99.987% is required in an anode-free configuration.
Due to the absence of excess Li in an anode-free configuration, not only the anode but also other battery components, including the cathode, must operate efficiently to preserve all available Li in the cell. Currently. Cathode materials typically demonstrate first discharge efficiencies of approximately 85-88% for NMC, 94-96% for LCO, and slightly higher than LCO for LFP, ranging from 95-97%. Another critical component crucial for the success of anode-free batteries is the role of electrolyte. Despite recent strides in optimizing cycling parameters and enhancing liquid electrolytes, inadequate efficiencies and dendrite growth during lithium plating contribute to poor cycle life, typically less than 100 cycles, along with safety concerns.
The AM4BAT project aims to develop an anode-free solid-state battery using VAT photopolymerization 3D printing, within the framework of HORIZON CL5-2021-D2-01-03. A Hybrid Solid electrolyte (HSE) comprises a mixture of ceramic material (LLZO) and photopolymer is considered for this battery. During first 18 months, besides specifications defined for materials and methods, the project focused on defining its trajectory and conducting primary tests and validations of material essential for AM4BAT battery cell components: anode, cathode, and electrolyte. Additionally, a thorough life cycle assessment of production methods and raw materials was undertaken to ensure both environmental and economic viability.
A surface of 5000 m2 could easily be considered to the electrode coating step. If in such a line LLZO, which is moisture sensitive is employed, it would require the processing to be carried out in a dried atmosphere with a dew point not lower than -40°C. This comes with additional infrastructure cost as well as running cost and human protections and restrictions. With the employment of a 3D printer to generate electrodes and HSE, this can be reduced.
In WP3, various routes for LLZO preparation together with the development of different formulations of the photocurable polymers have been studied to achieve a sensitive HSE formulation for 3D printing using VAT polymerization method. The project successfully addressed several challenges, such as structural sensitivity of LLZO to variations in thermal treatment temperature, number of steps, and duration, difficulties in achieving uniform dispersion and distribution of LLZO particles in the solvent, and LLZO sensitivity to the atmosphere, which adversely affected conductivity and the physical properties of the final HSE product.
WP4 focuses on several key objectives related to the development and enhancement of cathode materials for AM4BAT cells. This WP was successful in implementing a protective layer on the surface of cathode active material particles to hinder the decomposition of HSE at high potentials. The protective layer developed in WP4 has demonstrated promising results, leading to the registration of a patent.
Given the fact that AM4BAT uses anode-less cell configuration, and absence of excess Li in the battery, reducing irreversible capacity stands out as a primary objective in the testing of prepared NMC particles.
In the AM4BAT project, different routes for developing a CC for an anode-less battery are also being explored. The primary objective is to design a lithiphilic CC with high Li stripping/plating efficiencies. The project within WP5 has made significant progress so far in developing a lithiophilic CC for an anode-less Li-ion battery, aimed at improving coulombic efficiency.
Over the initial 18 months, the WP partners have explored various methodologies for constructing CCs, engaging in electrochemical testing to narrow down options and refine processes. Some samples demonstrated promising performance by being able to strip and plate Li ions for over 900 cycles at a current density of 0.4 mA/cm2. Although it falls short of the project’s target of 3000 cycles at 1C, this initial trail is encouraging and indicates potential for further optimization.
A surface of 5000 m2 could easily be considered to the electrode coating step. If in such a line LLZO, which is moisture sensitive is employed, it would require the processing to be carried out in a dried atmosphere with a dew point not lower than -40°C. This comes with additional infrastructure cost as well as running cost and human protections and restrictions. With the employment of a 3D printer to generate electrodes and HSE, this can be reduced.
In WP3, various routes for LLZO preparation together with the development of different formulations of the photocurable polymers have been studied to achieve a sensitive HSE formulation for 3D printing using VAT polymerization method. The project successfully addressed several challenges, such as structural sensitivity of LLZO to variations in thermal treatment temperature, number of steps, and duration, difficulties in achieving uniform dispersion and distribution of LLZO particles in the solvent, and LLZO sensitivity to the atmosphere, which adversely affected conductivity and the physical properties of the final HSE product.
WP4 focuses on several key objectives related to the development and enhancement of cathode materials for AM4BAT cells. This WP was successful in implementing a protective layer on the surface of cathode active material particles to hinder the decomposition of HSE at high potentials. The protective layer developed in WP4 has demonstrated promising results, leading to the registration of a patent.
Given the fact that AM4BAT uses anode-less cell configuration, and absence of excess Li in the battery, reducing irreversible capacity stands out as a primary objective in the testing of prepared NMC particles.
In the AM4BAT project, different routes for developing a CC for an anode-less battery are also being explored. The primary objective is to design a lithiphilic CC with high Li stripping/plating efficiencies. The project within WP5 has made significant progress so far in developing a lithiophilic CC for an anode-less Li-ion battery, aimed at improving coulombic efficiency.
Over the initial 18 months, the WP partners have explored various methodologies for constructing CCs, engaging in electrochemical testing to narrow down options and refine processes. Some samples demonstrated promising performance by being able to strip and plate Li ions for over 900 cycles at a current density of 0.4 mA/cm2. Although it falls short of the project’s target of 3000 cycles at 1C, this initial trail is encouraging and indicates potential for further optimization.
As the outcomes surpass the state-of-the-art, products from WP3, WP4, and WP5 deserve consideration.
Am4BAT has designed a hybrid solid electrolyte based on photocurable polymer matrix and 20% ceramic, with a remarkable conductivity of 10-3 S/cm at room temperature with a thickness on the order of 100 µm. this development resulted in in a defect-free demonstrating excellent mechanical flexibility. In WP4, a protective layer for cathode active material to inhibit solid electrolyte oxidation and reduce irreversible capacity with promising results has led to a patent registration. For confidentiality reasons, we won’t be sharing further results here. In WP5, a 30-40 µm thick anode current collector has been developed, demonstrating nearly 1000 cycles of lithium stripping/plating, aligning with the project’s volumetric energy density target. This thickness represents a reduction of at least 70% compared to typical anodes used in Li-Metal batteries (100-300 µm).
Am4BAT has designed a hybrid solid electrolyte based on photocurable polymer matrix and 20% ceramic, with a remarkable conductivity of 10-3 S/cm at room temperature with a thickness on the order of 100 µm. this development resulted in in a defect-free demonstrating excellent mechanical flexibility. In WP4, a protective layer for cathode active material to inhibit solid electrolyte oxidation and reduce irreversible capacity with promising results has led to a patent registration. For confidentiality reasons, we won’t be sharing further results here. In WP5, a 30-40 µm thick anode current collector has been developed, demonstrating nearly 1000 cycles of lithium stripping/plating, aligning with the project’s volumetric energy density target. This thickness represents a reduction of at least 70% compared to typical anodes used in Li-Metal batteries (100-300 µm).