High-Nickel Lithium-Ion Battery Electrodes for Energy Density and Cycle Life
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Solution Overview
Problem
Existing lithium-ion batteries face limitations in achieving higher mass energy density due to the theoretical capacity constraints of positive and negative electrode materials, leading to challenges in meeting market demands for improved energy storage performance in various applications.
Innovation Solution
A secondary battery design incorporating a positive electrode with a high nickel content and a carbon-silicon composite material for the negative electrode, featuring a three-dimensional network cross-linked pore structure, optimizes the distribution of silicon nanoparticles to enhance energy density and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high nickel content (≥85% molar) is used in the positive electrode active material to increase specific capacity and energy density, then the energy per unit area reaches 15-35 mWh/cm2, but transition metal dissolution increases causing deposition on the negative electrode plate which deteriorates cycle performance
Solution Approach 1:
A lithium phosphate coating layer is applied to the surface of the high-nickel positive electrode particles (LiNi0.85Co0.05Mn0.10O2) to act as an intermediary barrier. This coating prevents direct contact between the nickel-rich cathode material and the electrolyte, thereby suppressing transition metal dissolution and subsequent deposition on the negative electrode while maintaining high energy density (15-35 mWh/cm2).
Solution Approach 2:
The positive electrode uses a composite structure combining LiNi0.85Co0.05Mn0.10O2 with a lithium phosphate coating layer. This composite approach allows the core material to provide high specific capacity (85% nickel content) while the coating layer provides protective functions, resolving the contradiction between high energy density and cycle stability by preventing harmful interactions.
2Use of energy by moving object
If silicon nanoparticles are used in the negative electrode active material to increase theoretical capacity, then energy density is improved, but volume expansion during charging and discharging causes structural instability and poor cycle performance
Solution Approach 1:
A porous carbon coating layer is applied to the silicon nanoparticles in the negative electrode. This porous structure provides expansion space for the silicon during lithiation/delithiation cycles, accommodating volume changes without causing structural collapse. The porosity allows the silicon to expand and contract while maintaining structural integrity, thus preserving cycle performance while utilizing the high capacity of silicon.
Solution Approach 2:
The carbon coating layer acts as a flexible shell surrounding the silicon nanoparticles. This thin film structure can accommodate the volume expansion of silicon during charging by deforming elastically, while still providing mechanical support and preventing particle disintegration. The flexible carbon shell maintains electrical contact and protects the silicon core, enabling high energy density with sustained cycle performance.
3Use of energy by moving object
If the housing weight to bare cell weight ratio is reduced to 0.01≤z/JR≤0.42 to decrease overall battery mass, then mass energy density is improved, but structural strength and safety may be compromised
Solution Approach 1:
The housing design optimizes the weight ratio parameter z/JR to fall within 0.01-0.42, representing a significant reduction from conventional designs. This parameter change enables lighter overall battery mass while maintaining sufficient structural strength through advanced housing material selection and structural optimization, thereby achieving high mass energy density without compromising safety.
Data Source
AI summary
A secondary battery and an electric device are disclosed. The secondary battery includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet has a film layer comprising a positive electrode active material that contains transition metal elements, where nickel accounts for at least 85% of the total molar content of the transition metals. The energy per unit area of the positive electrode film layer on one side of the sheet ranges from 15 to 35 mWh/cm2. The negative electrode sheet includes a film layer with a carbon-silicon composite active material, in which silicon nanoparticles are attached to a carbon matrix having a carbon skeleton. The combination of a high-nickel positive electrode and a carbon-silicon composite negative electrode enhances the energy density of the secondary battery.