Abstract: A negative electrode plate includes a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, where the negative electrode active material layer includes a negative electrode active material, the negative electrode active material includes graphite and niobium composite metal oxide, the niobium composite metal oxide includes at least one of compounds with a molecular formula of TxNbyMzOa, and a mass ratio of the niobium composite metal oxide to the graphite is (5-50):(50-95). The electrochemical apparatus using such negative electrode plate of this application has good comprehensive performance.

Abstract: A positive electrode material includes a matrix material Na2Fe2(SO4)3. A surface of the matrix material includes a polyanionic material and a carbon material. The polyanionic material includes at least one of a phosphate compound, a NASICON compound, a pyrophosphate compound, or a fluorinated phosphate compound. A molar ratio between the matrix material and the polyanionic material is (1-A):A, where 0<A?0.1. Based on a mass of the positive electrode material, a mass percent of the carbon material is C %, satisfying: 0.5?C?5.

Abstract: An electrochemical device, including a positive electrode. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer includes particles A and particles B. A circularity of a particle A is RA, a cross-sectional area of the particle A is SA, a circularity of a particle B is RB, a cross-sectional area of the particle B is SB, where RB<0.4?RA and SB<20 ?m2?SA. Based on a total area of a cross section of the positive electrode in a direction perpendicular to the positive current collector, a ratio of a total area percent of the particles A to a total area percent of the particles B is 1:9 to 8:2. The electrochemical device exhibits excellent electrochemical performance, especially reduces the amount of generated gas and improves cycle stability of the electrochemical device.

Abstract: A positive active material, wherein, based on an initial lithium content of the positive active material, a delithiation percentage of the positive active material is t, and in a process from a start of delithiation of the positive active material to the delithiation percentage reaching t, a difference between a maximum value and a minimum value of a 2? angle of a (003) peak of the positive active material in an in-situ X-ray diffraction pattern is not greater than 1.2°, wherein 80%?t?93%. The electrochemical device that adopts the foregoing positive active material can achieve excellent electrochemical performance, especially reduce gas generation and improve cycle stability of the electrochemical device.