Silicon Negative Electrode Active Material for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries using silicon as a main material face challenges in achieving initial charge/discharge efficiency and cycle stability comparable to those using carbon-based active materials, with issues related to expansion, contraction, and electrolyte decomposition leading to degraded cycle characteristics.
Innovation Solution
A negative electrode active material composed of silicon compounds (SiOx: 0.5≤x≤1.6) with Li2SiO3, Li4SiO4, nickel, chromium, aluminum, and zirconium, where nickel and chromium enhance electronic conductivity, and aluminum-lithium alloys stabilize the slurry, combined with a carbon-based active material to improve charge/discharge efficiency and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the negative electrode active material to increase battery capacity, then the theoretical capacity increases significantly (10 times larger than graphite), but the superficial layer becomes easily broken due to expansion and contraction during charge/discharge
Solution Approach 1:
The patent uses a composite material structure where silicon particles are embedded in a porous carbon matrix. The carbon matrix provides mechanical strength and structural stability while the silicon particles provide high capacity. This composite approach allows the silicon to expand and contract without the superficial layer breaking, resolving the contradiction between high capacity and structural strength.
Solution Approach 2:
The porous carbon matrix acts as a flexible shell surrounding the silicon particles. This shell can accommodate the volume changes of silicon during charge/discharge cycles without breaking, preventing the superficial layer from fracturing while maintaining the high capacity benefit of silicon.
2Productivity
If the superficial layer of the negative electrode active material is broken, then a new surface is generated increasing the reaction area, but the electrolytic solution is consumed through decomposition reaction on the new surface
Solution Approach 1:
The porous carbon matrix is pre-formed around the silicon particles before battery operation. This preliminary protective layer prevents direct contact between the electrolytic solution and the silicon surface, eliminating decomposition reactions and electrolyte consumption while still allowing lithium ion transport through the porous structure.
Solution Approach 2:
The porous carbon matrix serves as an intermediary between the electrolytic solution and the silicon particles. It allows lithium ions to reach the silicon surface for the charge/discharge reaction while blocking the electrolytic solution from directly contacting and decomposing on the silicon surface.
3Reliability
If nickel and chromium are added to the silicon compound particles, then the electronic conductivity is improved, but the device complexity increases
Solution Approach 1:
The patent optimizes the concentration parameters of nickel and chromium within specific ranges (nickel: 0.1-10 at%, chromium: 0.1-10 at%) to achieve the desired electronic conductivity. By controlling these compositional parameters, the patent improves reliability while managing complexity through defined composition ranges rather than unrestricted material addition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution significantly enhances the initial charge/discharge efficiency and cycle stability of lithium ion secondary batteries, achieving high capacity and prolonged battery life by stabilizing the silicon compound and improving electronic conductivity.
Implementation Method 1
nickel and chromium enhance electronic conductivity
Implementation Method 2
aluminum-lithium alloys stabilize the slurry
Implementation Method 3
the negative electrode active material expands and contracts during charge/discharge
Data Source
AI summary
The present disclosure relates to a negative electrode active material including: particles of negative electrode active material, wherein the particles of negative electrode active material contain particles of silicon compound containing a silicon compound (SiOx: 0.55≤x≤1.6), and the particles of silicon compound includes at least one or more kinds of Li2SiO3 and Li4SiO4; the particles of silicon compound contain nickel; and, a mass of the nickel to a mass of the particles of negative electrode active material is 2 mass ppm or more and 100 mass ppm or less. Thus, when used as the negative electrode active material of a secondary battery, a negative electrode active material capable of improving the initial charge/discharge characteristics and cycle characteristics is provided.