Nickel strips play core functions such as electrical connection, structural support, and safety protection in new energy vehicle batteries (especially power batteries). Their performance directly affects the reliability, life, and safety of the battery. The following is a detailed analysis from two aspects: specific application scenarios and technical requirements:
I. Specific application of nickel strips in new energy vehicle batteries
1. Electrical connection between battery cells: electrode tab welding and busbar
Application scenario:
Connect the positive and negative electrode tabs (positive aluminum tabs, negative copper tabs) of a single battery cell with the busbar in the module to form a current path.
Typical case: In Tesla's 4680 battery module, nickel strips connect the battery cell tabs to the stainless steel busbars through laser welding, supporting a continuous discharge current of up to 150A.
Core role:
Reduce contact resistance (target < 2mΩ), reduce energy loss, and improve battery efficiency.
Disperse current density to avoid local overheating of the tabs (such as controlling the temperature at ≤80℃ during fast charging).
2. Module structure fixation and stress buffering
Application scenarios:
As a connecting piece between cells, the cell position is fixed by spot welding or laser welding, which is commonly used in square aluminum shell batteries (such as CATL CTP modules) and soft pack batteries (such as LG New Energy pouch batteries).
Core function:
Absorb the volume expansion of the cell during charging and discharging (about 10%~15%) to prevent the tab from breaking or the diaphragm from puncturing.
Provide mechanical support to ensure the structural stability of the module under vibration (such as bumpy driving of the car, vibration frequency 5~2000Hz).
3. Safety protection components: fuse belt and overcurrent protection
Application scenarios:
Designed as a fusible nickel belt (such as a locally thinned or hollowed structure), it is connected in series in the battery circuit.
Core function:
When the current exceeds the threshold (such as short-circuit current > 500A), the nickel belt fuses before the cell, cuts off the circuit, and prevents thermal runaway.
The response time must be controlled within 10ms, and the insulation resistance after melting must be ≥100MΩ to ensure safety.
4. Thermal management system integration
Application scenarios:
As a heat transfer medium, it transfers the heat of the battery cell to the module water cooling plate or shell, and is used in conjunction with thermal conductive silicone grease.
Core function:
The thermal conductivity must be ≥90W/(m・K), and the goal is to control the temperature difference between the battery cells to ≤2℃ to avoid capacity decay caused by local overheating.
Some nickel strips are designed as microchannel structures and embedded in liquid cooling pipes to improve heat dissipation efficiency (such as the indirect cooling solution of BYD blade batteries).
5. Process and reliability requirements
Dimensional accuracy: thickness tolerance ±5% (such as 0.1mm nickel strip tolerance ±0.005mm), width tolerance ±0.1mm, to ensure the adaptability of automated welding equipment.
Surface quality:
Roughness Ra≤1.6μm, avoid burrs piercing the diaphragm;
No oxidation color, oil stains, the welding surface needs to be electroplated with nickel-phosphorus alloy (plating thickness 2~5μm) to improve welding reliability.
Traceability: The batch number, chemical composition (Ni≥99.5%, impurities Fe≤0.1%, Cu≤0.05%), and mechanical properties data of the nickel strip need to be recorded to meet the requirements of the IATF 16949 quality management system.
II. Typical technical challenges and solutions
1. Ultra-thin requirements under high energy density
Challenge: In order to increase the energy density of the battery pack (target ≥300Wh/kg), the thickness of the nickel strip needs to be reduced from 0.15mm to less than 0.08mm, but it is easy to cause a decrease in strength.
Solution:
Use cold rolling + annealing process to improve strength and ductility through grain refinement (average grain size ≤10μm).
Develop nickel-graphene composite tape. 5% graphene content can increase tensile strength by 30%, while maintaining conductivity above 95%.
2. Heat dissipation optimization in fast charging scenarios
Challenge: During 480kW ultra-fast charging, the temperature of the nickel tape connection point may exceed 150°C, resulting in nickel oxidation or solder joint failure.
Solution:
Silver plating (thickness 1~2μm) on the surface of the nickel tape increases thermal conductivity to 420W/(m・K), and heat dissipation efficiency increases by 50%.
Design an interdigitated nickel tape structure to increase the heat dissipation area, and cooperate with microchannel liquid cooling to reduce the hot spot temperature by more than 20°C.
3. Anti-corrosion technology under long-life requirements
Challenge: In batteries with a cycle life of ≥3000 times, intergranular corrosion may occur when the nickel tape is in long-term contact with the electrolyte.
Solution:
Use vacuum nickel plating technology to form a non-porous pure nickel coating (thickness ≥3μm) to prevent electrolyte penetration.
Develop a passivation film enhancement process, increase the NiO film thickness from 5nm to 20nm through electrolytic oxidation, and reduce the corrosion rate to 0.01μm/year.
III. Future technology trends
Material innovation:
Nanocrystalline nickel strip (grain size < 100nm): strength increased to 800MPa, while maintaining 25% elongation, adapting to thinner specifications (below 0.05mm).
Nickel-carbon nanotube composite strip: conductivity increased to 6.5×10⁷ S/m, meeting the low impedance requirements of the 800V high-voltage platform.
Process upgrade:
Intelligent ultrasonic welding: real-time monitoring of welding power and amplitude through AI algorithms, increasing the solder joint yield from 95% to 99.5%.
Additive manufacturing nickel strip: 3D printing of complex structure nickel strips (such as spiral heat dissipation channels) to adapt to special-shaped battery module designs.
Sustainable development:
Develop electroless nickel strip: generate nickel layer directly on the surface of copper substrate through chemical vapor deposition (CVD) to reduce wastewater pollution.
Improve nickel strip recycling system: use electromagnetic induction heating technology to achieve lossless separation of nickel strip and battery cell, and the target material recovery rate is ≥98%.
Summary
Nickel strip is an "invisible but critical" core component in new energy vehicle batteries, and its performance must meet the stringent requirements of multiple dimensions such as electrical, mechanical, and environmental. With the development of 800V high-voltage platform, ultra-fast charging technology, and solid-state batteries, nickel strip will be iterated in the direction of ultra-thin, high-strength, and functional integration, and continue to support breakthroughs in power battery technology. Collaborative innovation between car companies and material manufacturers (such as the joint research and development of nickel strip by CATL and Baosteel Metal) will become a key driving force for the advancement of the industry.
Nickel strips play core functions such as electrical connection, structural support, and safety protection in new energy vehicle batteries (especially power batteries). Their performance directly affects the reliability, life, and safety of the battery. The following is a detailed analysis from two aspects: specific application scenarios and technical requirements:
I. Specific application of nickel strips in new energy vehicle batteries
1. Electrical connection between battery cells: electrode tab welding and busbar
Application scenario:
Connect the positive and negative electrode tabs (positive aluminum tabs, negative copper tabs) of a single battery cell with the busbar in the module to form a current path.
Typical case: In Tesla's 4680 battery module, nickel strips connect the battery cell tabs to the stainless steel busbars through laser welding, supporting a continuous discharge current of up to 150A.
Core role:
Reduce contact resistance (target < 2mΩ), reduce energy loss, and improve battery efficiency.
Disperse current density to avoid local overheating of the tabs (such as controlling the temperature at ≤80℃ during fast charging).
2. Module structure fixation and stress buffering
Application scenarios:
As a connecting piece between cells, the cell position is fixed by spot welding or laser welding, which is commonly used in square aluminum shell batteries (such as CATL CTP modules) and soft pack batteries (such as LG New Energy pouch batteries).
Core function:
Absorb the volume expansion of the cell during charging and discharging (about 10%~15%) to prevent the tab from breaking or the diaphragm from puncturing.
Provide mechanical support to ensure the structural stability of the module under vibration (such as bumpy driving of the car, vibration frequency 5~2000Hz).
3. Safety protection components: fuse belt and overcurrent protection
Application scenarios:
Designed as a fusible nickel belt (such as a locally thinned or hollowed structure), it is connected in series in the battery circuit.
Core function:
When the current exceeds the threshold (such as short-circuit current > 500A), the nickel belt fuses before the cell, cuts off the circuit, and prevents thermal runaway.
The response time must be controlled within 10ms, and the insulation resistance after melting must be ≥100MΩ to ensure safety.
4. Thermal management system integration
Application scenarios:
As a heat transfer medium, it transfers the heat of the battery cell to the module water cooling plate or shell, and is used in conjunction with thermal conductive silicone grease.
Core function:
The thermal conductivity must be ≥90W/(m・K), and the goal is to control the temperature difference between the battery cells to ≤2℃ to avoid capacity decay caused by local overheating.
Some nickel strips are designed as microchannel structures and embedded in liquid cooling pipes to improve heat dissipation efficiency (such as the indirect cooling solution of BYD blade batteries).
5. Process and reliability requirements
Dimensional accuracy: thickness tolerance ±5% (such as 0.1mm nickel strip tolerance ±0.005mm), width tolerance ±0.1mm, to ensure the adaptability of automated welding equipment.
Surface quality:
Roughness Ra≤1.6μm, avoid burrs piercing the diaphragm;
No oxidation color, oil stains, the welding surface needs to be electroplated with nickel-phosphorus alloy (plating thickness 2~5μm) to improve welding reliability.
Traceability: The batch number, chemical composition (Ni≥99.5%, impurities Fe≤0.1%, Cu≤0.05%), and mechanical properties data of the nickel strip need to be recorded to meet the requirements of the IATF 16949 quality management system.
II. Typical technical challenges and solutions
1. Ultra-thin requirements under high energy density
Challenge: In order to increase the energy density of the battery pack (target ≥300Wh/kg), the thickness of the nickel strip needs to be reduced from 0.15mm to less than 0.08mm, but it is easy to cause a decrease in strength.
Solution:
Use cold rolling + annealing process to improve strength and ductility through grain refinement (average grain size ≤10μm).
Develop nickel-graphene composite tape. 5% graphene content can increase tensile strength by 30%, while maintaining conductivity above 95%.
2. Heat dissipation optimization in fast charging scenarios
Challenge: During 480kW ultra-fast charging, the temperature of the nickel tape connection point may exceed 150°C, resulting in nickel oxidation or solder joint failure.
Solution:
Silver plating (thickness 1~2μm) on the surface of the nickel tape increases thermal conductivity to 420W/(m・K), and heat dissipation efficiency increases by 50%.
Design an interdigitated nickel tape structure to increase the heat dissipation area, and cooperate with microchannel liquid cooling to reduce the hot spot temperature by more than 20°C.
3. Anti-corrosion technology under long-life requirements
Challenge: In batteries with a cycle life of ≥3000 times, intergranular corrosion may occur when the nickel tape is in long-term contact with the electrolyte.
Solution:
Use vacuum nickel plating technology to form a non-porous pure nickel coating (thickness ≥3μm) to prevent electrolyte penetration.
Develop a passivation film enhancement process, increase the NiO film thickness from 5nm to 20nm through electrolytic oxidation, and reduce the corrosion rate to 0.01μm/year.
III. Future technology trends
Material innovation:
Nanocrystalline nickel strip (grain size < 100nm): strength increased to 800MPa, while maintaining 25% elongation, adapting to thinner specifications (below 0.05mm).
Nickel-carbon nanotube composite strip: conductivity increased to 6.5×10⁷ S/m, meeting the low impedance requirements of the 800V high-voltage platform.
Process upgrade:
Intelligent ultrasonic welding: real-time monitoring of welding power and amplitude through AI algorithms, increasing the solder joint yield from 95% to 99.5%.
Additive manufacturing nickel strip: 3D printing of complex structure nickel strips (such as spiral heat dissipation channels) to adapt to special-shaped battery module designs.
Sustainable development:
Develop electroless nickel strip: generate nickel layer directly on the surface of copper substrate through chemical vapor deposition (CVD) to reduce wastewater pollution.
Improve nickel strip recycling system: use electromagnetic induction heating technology to achieve lossless separation of nickel strip and battery cell, and the target material recovery rate is ≥98%.
Summary
Nickel strip is an "invisible but critical" core component in new energy vehicle batteries, and its performance must meet the stringent requirements of multiple dimensions such as electrical, mechanical, and environmental. With the development of 800V high-voltage platform, ultra-fast charging technology, and solid-state batteries, nickel strip will be iterated in the direction of ultra-thin, high-strength, and functional integration, and continue to support breakthroughs in power battery technology. Collaborative innovation between car companies and material manufacturers (such as the joint research and development of nickel strip by CATL and Baosteel Metal) will become a key driving force for the advancement of the industry.
